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Sample records for actin cable assembly

  1. Nonmedially assembled F-actin cables incorporate into the actomyosin ring in fission yeast

    PubMed Central

    Huang, Junqi; Huang, Yinyi; Yu, Haochen; Subramanian, Dhivya; Padmanabhan, Anup; Thadani, Rahul; Tao, Yaqiong; Tang, Xie; Wedlich-Soldner, Roland

    2012-01-01

    In many eukaryotes, cytokinesis requires the assembly and constriction of an actomyosin-based contractile ring. Despite the central role of this ring in cytokinesis, the mechanism of F-actin assembly and accumulation in the ring is not fully understood. In this paper, we investigate the mechanism of F-actin assembly during cytokinesis in Schizosaccharomyces pombe using lifeact as a probe to monitor actin dynamics. Previous work has shown that F-actin in the actomyosin ring is assembled de novo at the division site. Surprisingly, we find that a significant fraction of F-actin in the ring was recruited from formin-Cdc12p nucleated long actin cables that were generated at multiple nonmedial locations and incorporated into the ring by a combination of myosin II and myosin V activities. Our results, together with findings in animal cells, suggest that de novo F-actin assembly at the division site and directed transport of F-actin cables assembled elsewhere can contribute to ring assembly. PMID:23185032

  2. Srv2/CAP is required for polarized actin cable assembly and patch internalization during clathrin-mediated endocytosis.

    PubMed

    Toshima, Junko Y; Horikomi, Chika; Okada, Asuka; Hatori, Makiko N; Nagano, Makoto; Masuda, Atsushi; Yamamoto, Wataru; Siekhaus, Daria Elisabeth; Toshima, Jiro

    2016-01-15

    The dynamic assembly and disassembly of actin filaments is essential for the formation and transport of vesicles during endocytosis. In yeast, two types of actin structures, namely cortical patches and cytoplasmic cables, play a direct role in endocytosis, but how their interaction is regulated remains unclear. Here, we show that Srv2/CAP, an evolutionarily conserved actin regulator, is required for efficient endocytosis owing to its role in the formation of the actin patches that aid initial vesicle invagination and of the actin cables that these move along. Deletion of the SRV2 gene resulted in the appearance of aberrant fragmented actin cables that frequently moved past actin patches, the sites of endocytosis. We find that the C-terminal CARP domain of Srv2p is vitally important for the proper assembly of actin patches and cables; we also demonstrate that the N-terminal helical folded domain of Srv2 is required for its localization to actin patches, specifically to the ADP-actin rich region through an interaction with cofilin. These results demonstrate the in vivo roles of Srv2p in the regulation of the actin cytoskeleton during clathrin-mediated endocytosis.

  3. TorsinA controls TAN line assembly and the retrograde flow of dorsal perinuclear actin cables during rearward nuclear movement.

    PubMed

    Saunders, Cosmo A; Harris, Nathan J; Willey, Patrick T; Woolums, Brian M; Wang, Yuexia; McQuown, Alex J; Schoenhofen, Amy; Worman, Howard J; Dauer, William T; Gundersen, Gregg G; Luxton, G W Gant

    2017-03-06

    The nucleus is positioned toward the rear of most migratory cells. In fibroblasts and myoblasts polarizing for migration, retrograde actin flow moves the nucleus rearward, resulting in the orientation of the centrosome in the direction of migration. In this study, we report that the nuclear envelope-localized AAA+ (ATPase associated with various cellular activities) torsinA (TA) and its activator, the inner nuclear membrane protein lamina-associated polypeptide 1 (LAP1), are required for rearward nuclear movement during centrosome orientation in migrating fibroblasts. Both TA and LAP1 contributed to the assembly of transmembrane actin-associated nuclear (TAN) lines, which couple the nucleus to dorsal perinuclear actin cables undergoing retrograde flow. In addition, TA localized to TAN lines and was necessary for the proper mobility of EGFP-mini-nesprin-2G, a functional TAN line reporter construct, within the nuclear envelope. Furthermore, TA and LAP1 were indispensable for the retrograde flow of dorsal perinuclear actin cables, supporting the recently proposed function for the nucleus in spatially organizing actin flow and cytoplasmic polarity. Collectively, these results identify TA as a key regulator of actin-dependent rearward nuclear movement during centrosome orientation.

  4. Myosin Vs organize actin cables in fission yeast

    PubMed Central

    Lo Presti, Libera; Chang, Fred; Martin, Sophie G.

    2012-01-01

    Myosin V motors are believed to contribute to cell polarization by carrying cargoes along actin tracks. In Schizosaccharomyces pombe, Myosin Vs transport secretory vesicles along actin cables, which are dynamic actin bundles assembled by the formin For3 at cell poles. How these flexible structures are able to extend longitudinally in the cell through the dense cytoplasm is unknown. Here we show that in myosin V (myo52 myo51) null cells, actin cables are curled, bundled, and fail to extend into the cell interior. They also exhibit reduced retrograde flow, suggesting that formin-mediated actin assembly is impaired. Myo52 may contribute to actin cable organization by delivering actin regulators to cell poles, as myoV∆ defects are partially suppressed by diverting cargoes toward cell tips onto microtubules with a kinesin 7–Myo52 tail chimera. In addition, Myo52 motor activity may pull on cables to provide the tension necessary for their extension and efficient assembly, as artificially tethering actin cables to the nuclear envelope via a Myo52 motor domain restores actin cable extension and retrograde flow in myoV mutants. Together these in vivo data reveal elements of a self-organizing system in which the motors shape their own tracks by transporting cargoes and exerting physical pulling forces. PMID:23051734

  5. Computational model of polarized actin cables and cytokinetic actin ring formation in budding yeast

    PubMed Central

    Tang, Haosu; Bidone, Tamara C.

    2015-01-01

    The budding yeast actin cables and contractile ring are important for polarized growth and division, revealing basic aspects of cytoskeletal function. To study these formin-nucleated structures, we built a 3D computational model with actin filaments represented as beads connected by springs. Polymerization by formins at the bud tip and bud neck, crosslinking, severing, and myosin pulling, are included. Parameter values were estimated from prior experiments. The model generates actin cable structures and dynamics similar to those of wild type and formin deletion mutant cells. Simulations with increased polymerization rate result in long, wavy cables. Simulated pulling by type V myosin stretches actin cables. Increasing the affinity of actin filaments for the bud neck together with reduced myosin V pulling promotes the formation of a bundle of antiparallel filaments at the bud neck, which we suggest as a model for the assembly of actin filaments to the contractile ring. PMID:26538307

  6. Fimbrin phosphorylation by metaphase Cdk1 regulates actin cable dynamics in budding yeast

    PubMed Central

    Miao, Yansong; Han, Xuemei; Zheng, Liangzhen; Xie, Ying; Mu, Yuguang; Yates, John R.; Drubin, David G.

    2016-01-01

    Actin cables, composed of actin filament bundles nucleated by formins, mediate intracellular transport for cell polarity establishment and maintenance. We previously observed that metaphase cells preferentially promote actin cable assembly through cyclin-dependent kinase 1 (Cdk1) activity. However, the relevant metaphase Cdk1 targets were not known. Here we show that the highly conserved actin filament crosslinking protein fimbrin is a critical Cdk1 target for actin cable assembly regulation in budding yeast. Fimbrin is specifically phosphorylated on threonine 103 by the metaphase cyclin–Cdk1 complex, in vivo and in vitro. On the basis of conformational simulations, we suggest that this phosphorylation stabilizes fimbrin's N-terminal domain, and modulates actin filament binding to regulate actin cable assembly and stability in cells. Overall, this work identifies fimbrin as a key target for cell cycle regulation of actin cable assembly in budding yeast, and suggests an underlying mechanism. PMID:27068241

  7. Directed actin assembly and motility.

    PubMed

    Boujemaa-Paterski, Rajaa; Galland, Rémi; Suarez, Cristian; Guérin, Christophe; Théry, Manuel; Blanchoin, Laurent

    2014-01-01

    The actin cytoskeleton is a key component of the cellular architecture. However, understanding actin organization and dynamics in vivo is a complex challenge. Reconstitution of actin structures in vitro, in simplified media, allows one to pinpoint the cellular biochemical components and their molecular interactions underlying the architecture and dynamics of the actin network. Previously, little was known about the extent to which geometrical constraints influence the dynamic ultrastructure of these networks. Therefore, in order to study the balance between biochemical and geometrical control of complex actin organization, we used the innovative methodologies of UV and laser patterning to design a wide repertoire of nucleation geometries from which we assembled branched actin networks. Using these methods, we were able to reconstitute complex actin network organizations, closely related to cellular architecture, to precisely direct and control their 3D connections. This methodology mimics the actin networks encountered in cells and can serve in the fabrication of innovative bioinspired systems.

  8. Common formin-regulating sequences in Smy1 and Bud14 are required for the control of actin cable assembly in vivo.

    PubMed

    Eskin, Julian A; Rankova, Aneliya; Johnston, Adam B; Alioto, Salvatore L; Goode, Bruce L

    2016-03-01

    Formins comprise a large family of proteins with diverse roles in remodeling the actin cytoskeleton. However, the spatiotemporal mechanisms used by cells to control formin activities are only beginning to be understood. Here we dissected Smy1, which has dual roles in regulating formins and myosin. Using mutagenesis, we identified specific sequences in Smy1 critical for its in vitro inhibitory effects on the FH2 domain of the formin Bnr1. By integrating smy1 alleles targeting those sequences, we genetically uncoupled Smy1's functions in regulating formins and myosin. Quantitative imaging analysis further demonstrated that the ability of Smy1 to directly control Bnr1 activity is crucial in vivo for proper actin cable length, shape, and velocity and, in turn, efficient secretory vesicle transport. A Smy1-like sequence motif was also identified in a different Bnr1 regulator, Bud14, and found to be essential for Bud14 functions in regulating actin cable architecture and function in vivo. Together these observations reveal unanticipated mechanistic ties between two distinct formin regulators. Further, they emphasize the importance of tightly controlling formin activities in vivo to generate specialized geometries and dynamics of actin structures tailored to their physiological roles.

  9. Filopodia-like actin cables position nuclei in association with perinuclear actin in Drosophila nurse cells.

    PubMed

    Huelsmann, Sven; Ylänne, Jari; Brown, Nicholas H

    2013-09-30

    Controlling the position of the nucleus is vital for a number of cellular processes from yeast to humans. In Drosophila nurse cells, nuclear positioning is crucial during dumping, when nurse cells contract and expel their contents into the oocyte. We provide evidence that in nurse cells, continuous filopodia-like actin cables, growing from the plasma membrane and extending to the nucleus, achieve nuclear positioning. These actin cables move nuclei away from ring canals. When nurse cells contract, actin cables associate laterally with the nuclei, in some cases inducing nuclear turning so that actin cables become partially wound around the nuclei. Our data suggest that a perinuclear actin meshwork connects actin cables to nuclei via actin-crosslinking proteins such as the filamin Cheerio. We provide a revised model for how actin structures position nuclei in nurse cells, employing evolutionary conserved machinery.

  10. Actin dynamics in Phytophthora infestans; rapidly reorganizing cables and immobile, long-lived plaques.

    PubMed

    Meijer, Harold J G; Hua, Chenlei; Kots, Kiki; Ketelaar, Tijs; Govers, Francine

    2014-06-01

    The actin cytoskeleton is a dynamic but well-organized intracellular framework that is essential for proper functioning of eukaryotic cells. Here, we use the actin binding peptide Lifeact to investigate the in vivo actin cytoskeleton dynamics in the oomycete plant pathogen Phytophthora infestans. Lifeact-eGFP labelled thick and thin actin bundles and actin filament plaques allowing visualization of actin dynamics. All actin structures in the hyphae were cortically localized. In growing hyphae actin filament cables were axially oriented in the sub-apical region whereas in the extreme apex in growing hyphae, waves of fine F-actin polymerization were observed. Upon growth termination, actin filament plaques appeared in the hyphal tip. The distance between a hyphal tip and the first actin filament plaque correlated strongly with hyphal growth velocity. The actin filament plaques were nearly immobile with average lifetimes exceeding 1 h, relatively long when compared to the lifetime of actin patches known in other eukaryotes. Plaque assembly required ∼30 s while disassembly was accomplished in ∼10 s. Remarkably, plaque disassembly was not accompanied with internalization and the formation of endocytic vesicles. These findings suggest that the functions of actin plaques in oomycetes differ from those of actin patches present in other organisms.

  11. Photonic-powered cable assembly

    DOEpatents

    Sanderson, Stephen N.; Appel, Titus James; Wrye, IV, Walter C.

    2013-01-22

    A photonic-cable assembly includes a power source cable connector ("PSCC") coupled to a power receive cable connector ("PRCC") via a fiber cable. The PSCC electrically connects to a first electronic device and houses a photonic power source and an optical data transmitter. The fiber cable includes an optical transmit data path coupled to the optical data transmitter, an optical power path coupled to the photonic power source, and an optical feedback path coupled to provide feedback control to the photonic power source. The PRCC electrically connects to a second electronic device and houses an optical data receiver coupled to the optical transmit data path, a feedback controller coupled to the optical feedback path to control the photonic power source, and a photonic power converter coupled to the optical power path to convert photonic energy received over the optical power path to electrical energy to power components of the PRCC.

  12. Photonic-powered cable assembly

    DOEpatents

    Sanderson, Stephen N; Appel, Titus James; Wrye, IV, Walter C

    2014-06-24

    A photonic-cable assembly includes a power source cable connector ("PSCC") coupled to a power receive cable connector ("PRCC") via a fiber cable. The PSCC electrically connects to a first electronic device and houses a photonic power source and an optical data transmitter. The fiber cable includes an optical transmit data path coupled to the optical data transmitter, an optical power path coupled to the photonic power source, and an optical feedback path coupled to provide feedback control to the photonic power source. The PRCC electrically connects to a second electronic device and houses an optical data receiver coupled to the optical transmit data path, a feedback controller coupled to the optical feedback path to control the photonic power source, and a photonic power converter coupled to the optical power path to convert photonic energy received over the optical power path to electrical energy to power components of the PRCC.

  13. An atomic model of the tropomyosin cable on F-actin.

    PubMed

    Orzechowski, Marek; Li, Xiaochuan Edward; Fischer, Stefan; Lehman, William

    2014-08-05

    Tropomyosin regulates a wide variety of actin filament functions and is best known for the role that it plays together with troponin in controlling muscle activity. For effective performance on actin filaments, adjacent 42-nm-long tropomyosin molecules are joined together by a 9- to 10-residue head-to-tail overlapping domain to form a continuous cable that wraps around the F-actin helix. Yet, despite the apparent simplicity of tropomyosin's coiled-coil structure and its well-known periodic association with successive actin subunits along F-actin, the structure of the tropomyosin cable on actin is uncertain. This is because the conformation of the overlap region that joins neighboring molecules is poorly understood, thus leaving a significant gap in our understanding of thin-filament structure and regulation. However, recent molecular-dynamics simulations of overlap segments defined their overall shape and provided unique and sufficient cues to model the whole actin-tropomyosin filament assembly in atomic detail. In this study, we show that these MD structures merge seamlessly onto the ends of tropomyosin coiled-coils. Adjacent tropomyosin molecules can then be joined together to provide a comprehensive model of the tropomyosin cable running continuously on F-actin. The resulting complete model presented here describes for the first time (to our knowledge) an atomic-level structure of αα-striated muscle tropomyosin bound to an actin filament that includes the critical overlap domain. Thus, the model provides a structural correlate to evaluate thin-filament mechanics, self-assembly mechanisms, and the effect of disease-causing mutations.

  14. Debris protection cover assembly for cable connectors

    NASA Technical Reports Server (NTRS)

    Yovan, Roger D. (Inventor)

    1999-01-01

    A protective cover assembly for an end of a cable connector having a cable housing that encloses a plurality of connective pins or sockets and that satisfies all requirements for space applications. A connector body flange is formed at the extremity of a cable and is positioned so that it may register with a corresponding connector body flange on the end of a companion cable to which a connection is to be made, one cable end having cable lead pins and the companion cable end having lead sockets with which the pins register. A latch mechanism having a latch housing is received in the connector body flange and a crank connected to a manually rotatable cap actuates a spring-loaded latch element that is engageable with a connector body flange to secure or to release the cover assembly with the simple twisting motion of the cap, thereby simplifying the task of effecting coupling and decoupling of the cable ends.

  15. Profilin connects actin assembly with microtubule dynamics

    PubMed Central

    Nejedla, Michaela; Sadi, Sara; Sulimenko, Vadym; de Almeida, Francisca Nunes; Blom, Hans; Draber, Pavel; Aspenström, Pontus; Karlsson, Roger

    2016-01-01

    Profilin controls actin nucleation and assembly processes in eukaryotic cells. Actin nucleation and elongation promoting factors (NEPFs) such as Ena/VASP, formins, and WASP-family proteins recruit profilin:actin for filament formation. Some of these are found to be microtubule associated, making actin polymerization from microtubule-associated platforms possible. Microtubules are implicated in focal adhesion turnover, cell polarity establishment, and migration, illustrating the coupling between actin and microtubule systems. Here we demonstrate that profilin is functionally linked to microtubules with formins and point to formins as major mediators of this association. To reach this conclusion, we combined different fluorescence microscopy techniques, including superresolution microscopy, with siRNA modulation of profilin expression and drug treatments to interfere with actin dynamics. Our studies show that profilin dynamically associates with microtubules and this fraction of profilin contributes to balance actin assembly during homeostatic cell growth and affects micro­tubule dynamics. Hence profilin functions as a regulator of microtubule (+)-end turnover in addition to being an actin control element. PMID:27307590

  16. Procedure for potting electrical cable assembly terminations

    NASA Technical Reports Server (NTRS)

    Williams, H. F.

    1972-01-01

    Procedures for the safe cleaning and potting of cable assembly terminations are given. Data cover primer application and injection of the potting compound. Required safety precautions for the process are listed.

  17. The F-BAR protein Hof1 tunes formin activity to sculpt actin cables during polarized growth

    PubMed Central

    Graziano, Brian R.; Yu, Hoi-Ying E.; Alioto, Salvatore L.; Eskin, Julian A.; Ydenberg, Casey A.; Waterman, David P.; Garabedian, Mikael; Goode, Bruce L.

    2014-01-01

    Asymmetric cell growth and division rely on polarized actin cytoskeleton remodeling events, the regulation of which is poorly understood. In budding yeast, formins stimulate the assembly of an organized network of actin cables that direct polarized secretion. Here we show that the Fer/Cip4 homology–Bin amphiphysin Rvs protein Hof1, which has known roles in cytokinesis, also functions during polarized growth by directly controlling the activities of the formin Bnr1. A mutant lacking the C-terminal half of Hof1 displays misoriented and architecturally altered cables, along with impaired secretory vesicle traffic. In vitro, Hof1 inhibits the actin nucleation and elongation activities of Bnr1 without displacing the formin from filament ends. These effects depend on the Src homology 3 domain of Hof1, the formin homology 1 (FH1) domain of Bnr1, and Hof1 dimerization, suggesting a mechanism by which Hof1 “restrains” the otherwise flexible FH1-FH2 apparatus. In vivo, loss of inhibition does not alter actin levels in cables but, instead, cable shape and functionality. Thus Hof1 tunes formins to sculpt the actin cable network. PMID:24719456

  18. Arabidopsis ACTIN-DEPOLYMERIZING FACTOR7 Severs Actin Filaments and Regulates Actin Cable Turnover to Promote Normal Pollen Tube Growth[W

    PubMed Central

    Zheng, Yiyan; Xie, Yurong; Jiang, Yuxiang; Qu, Xiaolu; Huang, Shanjin

    2013-01-01

    Actin filaments are often arranged into higher-order structures, such as the longitudinal actin cables that generate the reverse fountain cytoplasmic streaming pattern present in pollen tubes. While several actin binding proteins have been implicated in the generation of these cables, the mechanisms that regulate their dynamic turnover remain largely unknown. Here, we show that Arabidopsis thaliana ACTIN-DEPOLYMERIZING FACTOR7 (ADF7) is required for turnover of longitudinal actin cables. In vitro biochemical analyses revealed that ADF7 is a typical ADF that prefers ADP-G-actin over ATP-G-actin. ADF7 inhibits nucleotide exchange on actin and severs filaments, but its filament severing and depolymerizing activities are less potent than those of the vegetative ADF1. ADF7 primarily decorates longitudinal actin cables in the shanks of pollen tubes. Consistent with this localization pattern, the severing frequency and depolymerization rate of filaments significantly decreased, while their maximum lifetime significantly increased, in adf7 pollen tube shanks. Furthermore, an ADF7–enhanced green fluorescent protein fusion with defective severing activity but normal G-actin binding activity could not complement adf7, providing compelling evidence that the severing activity of ADF7 is vital for its in vivo functions. These observations suggest that ADF7 evolved to promote turnover of longitudinal actin cables by severing actin filaments in pollen tubes. PMID:24058157

  19. CF2256 cable assembly: development report

    SciTech Connect

    Barber, E.R.; Donaldson, G.H.

    1980-08-01

    The CF2256 is a multiwire, low-voltage cable contained in the W76-0/MK4 Reentry Body. It carries fuze presetting and actuator signals between the DOD cabling and the MC2912 Arming, Fuzing, and Firing assembly. The CF2256 successful development history is given along with some evaluation data. There is also an extensive list of references to assist in finding additional information.

  20. Formaldehyde fixation is detrimental to actin cables in glucose-depleted S. cerevisiae cells

    PubMed Central

    Vasicova, Pavla; Rinnerthaler, Mark; Haskova, Danusa; Novakova, Lenka; Malcova, Ivana; Breitenbach, Michael; Hasek, Jiri

    2016-01-01

    Actin filaments form cortical patches and emanating cables in fermenting cells of Saccharomyces cerevisiae. This pattern has been shown to be depolarized in glucose-depleted cells after formaldehyde fixation and staining with rhodamine-tagged phalloidin. Loss of actin cables in mother cells was remarkable. Here we extend our knowledge on actin in live glucose-depleted cells co-expressing the marker of actin patches (Abp1-RFP) with the marker of actin cables (Abp140-GFP). Glucose depletion resulted in appearance of actin patches also in mother cells. However, even after 80 min of glucose deprivation these cells showed a clear network of actin cables labeled with Abp140-GFP in contrast to previously published data. In live cells with a mitochondrial dysfunction (rho0 cells), glucose depletion resulted in almost immediate appearance of Abp140-GFP foci partially overlapping with Abp1-RFP patches in mother cells. Residual actin cables were clustered in patch-associated bundles. A similar overlapping “patchy” pattern of both actin markers was observed upon treatment of glucose-deprived rho+ cells with FCCP (the inhibitor of oxidative phosphorylation) and upon treatment with formaldehyde. While the formaldehyde-targeted process stays unknown, our results indicate that published data on yeast actin cytoskeleton obtained from glucose-depleted cells after fixation should be considered with caution.

  1. Self-assembly of Artificial Actin Filaments

    NASA Astrophysics Data System (ADS)

    Grosenick, Christopher; Cheng, Shengfeng

    Actin Filaments are long, double-helical biopolymers that make up the cytoskeleton along with microtubules and intermediate filaments. In order to further understand the self-assembly process of these biopolymers, a model to recreate actin filament geometry was developed. A monomer in the shape of a bent rod with vertical and lateral binding sites was designed to assemble into single or double helices. With Molecular Dynamics simulations, a variety of phases were observed to form by varying the strength of the binding sites. Ignoring lateral binding sites, we have found a narrow range of binding strengths that lead to long single helices via various growth pathways. When lateral binding strength is introduced, double helices begin to form. These double helices self-assemble into substantially more stable structures than their single helix counterparts. We have found double helices to form long filaments at about half the vertical binding strength of single helices. Surprisingly, we have found that triple helices occasionally form, indicating the importance of structural regulation in the self-assembly of biopolymers.

  2. Viral Replication Protein Inhibits Cellular Cofilin Actin Depolymerization Factor to Regulate the Actin Network and Promote Viral Replicase Assembly

    PubMed Central

    Kovalev, Nikolay; de Castro Martín, Isabel Fernández; Barajas, Daniel; Risco, Cristina; Nagy, Peter D.

    2016-01-01

    RNA viruses exploit host cells by co-opting host factors and lipids and escaping host antiviral responses. Previous genome-wide screens with Tomato bushy stunt virus (TBSV) in the model host yeast have identified 18 cellular genes that are part of the actin network. In this paper, we show that the p33 viral replication factor interacts with the cellular cofilin (Cof1p), which is an actin depolymerization factor. Using temperature-sensitive (ts) Cof1p or actin (Act1p) mutants at a semi-permissive temperature, we find an increased level of TBSV RNA accumulation in yeast cells and elevated in vitro activity of the tombusvirus replicase. We show that the large p33 containing replication organelle-like structures are located in the close vicinity of actin patches in yeast cells or around actin cable hubs in infected plant cells. Therefore, the actin filaments could be involved in VRC assembly and the formation of large viral replication compartments containing many individual VRCs. Moreover, we show that the actin network affects the recruitment of viral and cellular components, including oxysterol binding proteins and VAP proteins to form membrane contact sites for efficient transfer of sterols to the sites of replication. Altogether, the emerging picture is that TBSV, via direct interaction between the p33 replication protein and Cof1p, controls cofilin activities to obstruct the dynamic actin network that leads to efficient subversion of cellular factors for pro-viral functions. In summary, the discovery that TBSV interacts with cellular cofilin and blocks the severing of existing filaments and the formation of new actin filaments in infected cells opens a new window to unravel the way by which viruses could subvert/co-opt cellular proteins and lipids. By regulating the functions of cofilin and the actin network, which are central nodes in cellular pathways, viruses could gain supremacy in subversion of cellular factors for pro-viral functions. PMID:26863541

  3. Cytoplasmic Actin: Purification and Single Molecule Assembly Assays

    PubMed Central

    Hansen, Scott D.; Zuchero, J. Bradley; Mullins, R. Dyche

    2014-01-01

    The actin cytoskeleton is essential to all eukaryotic cells. In addition to playing important structural roles, assembly of actin into filaments powers diverse cellular processes, including cell motility, cytokinesis, and endocytosis. Actin polymerization is tightly regulated by its numerous cofactors, which control spatial and temporal assembly of actin as well as the physical properties of these filaments. Development of an in vitro model of actin polymerization from purified components has allowed for great advances in determining the effects of these proteins on the actin cytoskeleton. Here we describe how to use the pyrene actin assembly assay to determine the effect of a protein on the kinetics of actin assembly, either directly or as mediated by proteins such as nucleation or capping factors. Secondly, we show how fluorescently labeled phalloidin can be used to visualize the filaments that are created in vitro to give insight into how proteins regulate actin filament structure. Finally, we describe a method for visualizing dynamic assembly and disassembly of single actin filaments and fluorescently labeled actin binding proteins using total internal reflection fluorescence (TIRF) microscopy. PMID:23868587

  4. Formation of long and winding nuclear F-actin bundles by nuclear c-Abl tyrosine kinase

    SciTech Connect

    Aoyama, Kazumasa; Yuki, Ryuzaburo; Horiike, Yasuyoshi; Kubota, Sho; Yamaguchi, Noritaka; Morii, Mariko; Ishibashi, Kenichi; Nakayama, Yuji; Kuga, Takahisa; Hashimoto, Yuuki; Tomonaga, Takeshi; Yamaguchi, Naoto

    2013-12-10

    The non-receptor-type tyrosine kinase c-Abl is involved in actin dynamics in the cytoplasm. Having three nuclear localization signals (NLSs) and one nuclear export signal, c-Abl shuttles between the nucleus and the cytoplasm. Although monomeric actin and filamentous actin (F-actin) are present in the nucleus, little is known about the relationship between c-Abl and nuclear actin dynamics. Here, we show that nuclear-localized c-Abl induces nuclear F-actin formation. Adriamycin-induced DNA damage together with leptomycin B treatment accumulates c-Abl into the nucleus and increases the levels of nuclear F-actin. Treatment of c-Abl-knockdown cells with Adriamycin and leptomycin B barely increases the nuclear F-actin levels. Expression of nuclear-targeted c-Abl (NLS-c-Abl) increases the levels of nuclear F-actin even without Adriamycin, and the increased levels of nuclear F-actin are not inhibited by inactivation of Abl kinase activity. Intriguingly, expression of NLS-c-Abl induces the formation of long and winding bundles of F-actin within the nucleus in a c-Abl kinase activity-dependent manner. Furthermore, NLS-c-AblΔC, which lacks the actin-binding domain but has the full tyrosine kinase activity, is incapable of forming nuclear F-actin and in particular long and winding nuclear F-actin bundles. These results suggest that nuclear c-Abl plays critical roles in actin dynamics within the nucleus. - Highlights: • We show the involvement of c-Abl tyrosine kinase in nuclear actin dynamics. • Nuclear F-actin is formed by nuclear-localized c-Abl and its kinase-dead version. • The c-Abl actin-binding domain is prerequisite for nuclear F-actin formation. • Formation of long nuclear F-actin bundles requires nuclear c-Abl kinase activity. • We discuss a role for nuclear F-actin bundle formation in chromatin regulation.

  5. Mitochondrial inheritance: cell cycle and actin cable dependence of polarized mitochondrial movements in Saccharomyces cerevisiae.

    PubMed

    Simon, V R; Karmon, S L; Pon, L A

    1997-01-01

    Asymmetric growth and division of budding yeast requires the vectorial transport of growth components and organelles from mother to daughter cells. Time lapse video microscopy and vital staining were used to study motility events which result in partitioning of mitochondria in dividing yeast. We identified four different stages in the mitochondrial inheritance cycle: (1) mitochondria align along the mother-bud axis prior to bud emergence in G1 phase, following polarization of the actin cytoskeleton; (2) during S phase, mitochondria undergo linear, continuous and polarized transfer from mother to bud; (3) during S and G2 phases, inherited mitochondria accumulate in the bud tip. This event occurs concomitant with accumulation of actin patches in this region; and (4) finally, during M phase prior to cytokinesis, mitochondria are released from the bud tip and redistribute throughout the bud. Previous studies showed that yeast mitochondria colocalize with actin cables and that isolated mitochondria contain actin binding and motor activities on their surface. We find that selective destabilization of actin cables in a strain lacking the tropomyosin 1 gene (TPM1) has no significant effect on the velocity of mitochondrial motor activity in vivo or in vitro. However, tpm1 delta mutants display abnormal mitochondrial distribution and morphology; loss of long distance, directional mitochondrial movement; and delayed transfer of mitochondria from the mother cell to the bud. Thus, cell cycle-linked mitochondrial motility patterns which lead to inheritance are strictly dependent on organized and properly oriented actin cables.

  6. 11. DETAIL VIEW OF NONSUBMERSIBLE TAINTER GATE, SHOWING CABLE ASSEMBLY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. DETAIL VIEW OF NON-SUBMERSIBLE TAINTER GATE, SHOWING CABLE ASSEMBLY ATTACHMENT, LOOKING EAST (DOWNSTREAM) - Upper Mississippi River 9-Foot Channel Project, Lock & Dam 26R, Alton, Madison County, IL

  7. Structure of a Longitudinal Actin Dimer Assembled by Tandem W Domains: Implications for Actin Filament Nucleation

    SciTech Connect

    Rebowski, Grzegorz; Namgoong, Suk; Boczkowska, Malgorzata; Leavis, Paul C.; Navaza, Jorge; Dominguez, Roberto

    2013-11-20

    Actin filament nucleators initiate polymerization in cells in a regulated manner. A common architecture among these molecules consists of tandem WASP homology 2 domains (W domains) that recruit three to four actin subunits to form a polymerization nucleus. We describe a low-resolution crystal structure of an actin dimer assembled by tandem W domains, where the first W domain is cross-linked to Cys374 of the actin subunit bound to it, whereas the last W domain is followed by the C-terminal pointed end-capping helix of thymosin {beta}4. While the arrangement of actin subunits in the dimer resembles that of a long-pitch helix of the actin filament, important differences are observed. These differences result from steric hindrance of the W domain with intersubunit contacts in the actin filament. We also determined the structure of the first W domain of Vibrio parahaemolyticus VopL cross-linked to actin Cys374 and show it to be nearly identical with non-cross-linked W-Actin structures. This result validates the use of cross-linking as a tool for the study of actin nucleation complexes, whose natural tendency to polymerize interferes with most structural methods. Combined with a biochemical analysis of nucleation, the structures may explain why nucleators based on tandem W domains with short inter-W linkers have relatively weak activity, cannot stay bound to filaments after nucleation, and are unlikely to influence filament elongation. The findings may also explain why nucleation-promoting factors of the Arp2/3 complex, which are related to tandem-W-domain nucleators, are ejected from branch junctions after nucleation. We finally show that the simple addition of the C-terminal pointed end-capping helix of thymosin {beta}4 to tandem W domains can change their activity from actin filament nucleation to monomer sequestration.

  8. Structure of a longitudinal actin dimer assembled by tandem w domains: implications for actin filament nucleation.

    PubMed

    Rebowski, Grzegorz; Namgoong, Suk; Boczkowska, Malgorzata; Leavis, Paul C; Navaza, Jorge; Dominguez, Roberto

    2010-10-15

    Actin filament nucleators initiate polymerization in cells in a regulated manner. A common architecture among these molecules consists of tandem WASP homology 2 domains (W domains) that recruit three to four actin subunits to form a polymerization nucleus. We describe a low-resolution crystal structure of an actin dimer assembled by tandem W domains, where the first W domain is cross-linked to Cys374 of the actin subunit bound to it, whereas the last W domain is followed by the C-terminal pointed end-capping helix of thymosin β4. While the arrangement of actin subunits in the dimer resembles that of a long-pitch helix of the actin filament, important differences are observed. These differences result from steric hindrance of the W domain with intersubunit contacts in the actin filament. We also determined the structure of the first W domain of Vibrio parahaemolyticus VopL cross-linked to actin Cys374 and show it to be nearly identical with non-cross-linked W-Actin structures. This result validates the use of cross-linking as a tool for the study of actin nucleation complexes, whose natural tendency to polymerize interferes with most structural methods. Combined with a biochemical analysis of nucleation, the structures may explain why nucleators based on tandem W domains with short inter-W linkers have relatively weak activity, cannot stay bound to filaments after nucleation, and are unlikely to influence filament elongation. The findings may also explain why nucleation-promoting factors of the Arp2/3 complex, which are related to tandem-W-domain nucleators, are ejected from branch junctions after nucleation. We finally show that the simple addition of the C-terminal pointed end-capping helix of thymosin β4 to tandem W domains can change their activity from actin filament nucleation to monomer sequestration.

  9. Single-molecule studies of actin assembly and disassembly factors.

    PubMed

    Smith, Benjamin A; Gelles, Jeff; Goode, Bruce L

    2014-01-01

    The actin cytoskeleton is very dynamic and highly regulated by multiple associated proteins in vivo. Understanding how this system of proteins functions in the processes of actin network assembly and disassembly requires methods to dissect the mechanisms of activity of individual factors and of multiple factors acting in concert. The advent of single-filament and single-molecule fluorescence imaging methods has provided a powerful new approach to discovering actin-regulatory activities and obtaining direct, quantitative insights into the pathways of molecular interactions that regulate actin network architecture and dynamics. Here we describe techniques for acquisition and analysis of single-molecule data, applied to the novel challenges of studying the filament assembly and disassembly activities of actin-associated proteins in vitro. We discuss the advantages of single-molecule analysis in directly visualizing the order of molecular events, measuring the kinetic rates of filament binding and dissociation, and studying the coordination among multiple factors. The methods described here complement traditional biochemical approaches in elucidating actin-regulatory mechanisms in reconstituted filamentous networks.

  10. Dissecting principles governing actin assembly using yeast extracts.

    PubMed

    Michelot, Alphée; Drubin, David G

    2014-01-01

    In this chapter, we describe recent protocols that we have developed to trigger actin assembly and actin-based motility in yeast cell extracts. Our method allows for the fast preparation of yeast extracts that are competent in dynamic assembly of distinct actin filament structures of biologically appropriate protein composition. Compared to previous extract-based systems using other eukaryotic cell types, yeast provides a unique advantage for combining reconstituted assays with the preparation of extracts from genetically modified yeast strains. We present a global strategy for dissecting the functions of individual proteins, where the activities of the proteins are analyzed in systems of variable complexity, ranging from simple mixtures of pure proteins to the full complexity of a cell's cytoplasm.

  11. Lamellipodin promotes actin assembly by clustering Ena/VASP proteins and tethering them to actin filaments

    PubMed Central

    Hansen, Scott D; Mullins, R Dyche

    2015-01-01

    Enabled/Vasodilator (Ena/VASP) proteins promote actin filament assembly at multiple locations, including: leading edge membranes, focal adhesions, and the surface of intracellular pathogens. One important Ena/VASP regulator is the mig-10/Lamellipodin/RIAM family of adaptors that promote lamellipod formation in fibroblasts and drive neurite outgrowth and axon guidance in neurons. To better understand how MRL proteins promote actin network formation we studied the interactions between Lamellipodin (Lpd), actin, and VASP, both in vivo and in vitro. We find that Lpd binds directly to actin filaments and that this interaction regulates its subcellular localization and enhances its effect on VASP polymerase activity. We propose that Lpd delivers Ena/VASP proteins to growing barbed ends and increases their polymerase activity by tethering them to filaments. This interaction represents one more pathway by which growing actin filaments produce positive feedback to control localization and activity of proteins that regulate their assembly. DOI: http://dx.doi.org/10.7554/eLife.06585.001 PMID:26295568

  12. Nuclear actin and protein 4.1: Essential interactions during nuclear assembly in vitro

    SciTech Connect

    Krauss, Sharon Wald; Chen, Cynthia; Penman, Sheldon; Heald, Rebecca

    2003-06-11

    Structural protein 4.1, which has crucial interactions within the spectin-actin lattice of the human red cell membrane skeleton, also is widely distributed at diverse intracellular sites in nucleated cells. We previously showed that 4.1 is essential for assembly of functional nuclei in vitro and that the capacity of 4.1 to bind actin is required. Here we report that 4.1 and actin colocalize in mammalian cell nuclei using fluorescence microscopy and, by higher resolution cell whole mount electron microscopy, are associated on nuclear filaments. We also devised a cell-free assay using Xenopus egg extract containing fluorescent actin to follow actin during nuclear assembly. By directly imaging actin under non-perturbing conditions, the total nuclear actin population is retained and is visualized in situ relative to intact chromatin. We detected actin initially when chromatin and nuclear pores began assembling. As the nuclear lamina assembled, but preceding DNA synthesis, a discrete actin network formed throughout the nucleus. Protein 4.1 epitopes also were detected when actin began to accumulate in nuclei, producing a diffuse coincident pattern. As nuclei matured, actin was detected both coincident with and also independent of 4.1 epitopes. To test whether acquisition of nuclear actin is required for nuclear assembly, the actin inhibitor latrunculin A was added to Xenopus egg extracts during nuclear assembly. Latrunculin A strongly perturbed nuclear assembly and produced distorted nuclear structures containing neither actin nor protein 4.1. Our results suggest that actin as well as 4.1 is necessary for nuclear assembly and that 4.1-actin interactions may be critical.

  13. Automated method for fabrication of parallel multifiber cable assemblies with integral connector components

    NASA Astrophysics Data System (ADS)

    Lee, Nicholas A.; Igl, Scott A.; DeBaun, Barbara A.; Henson, Gordon D.; Smith, Terry L.

    1997-04-01

    The unrelenting demand for ever-higher data transfer rates between computing devices, coupled with the emerging ability to produce robust, monolithic arrays of optical sources and detectors has fueled the development of high-speed parallel optical data links, and created a need for connectorized, parallel, multifiber cable assemblies. An innovative approach to the cable assembly manufacturing process has been developed which incorporates the connector installation process into the cable fabrication process, thus enabling the production of connectorized cable assemblies in a continuous, automated manner. This cable assembly fabrication process, as well as critical details surrounding the process, will be discussed.

  14. Fiber Optic Cable Assemblies for Space Flight 2: Thermal and Radiation Effects

    NASA Technical Reports Server (NTRS)

    Ott, Melanie N.

    1998-01-01

    Goddard Space Flight Center is conducting a search for space flight worthy fiber optic cable assemblies that will benefit all projects at all of the NASA centers. This paper is number two in a series of papers being issued as a result of this task to define and qualify space grade fiber optic cable assemblies. Though to qualify and use a fiber optic cable in space requires treatment of the cable assembly as a system, it is very important to understand the design and behavior of its parts. This paper addresses that need, providing information on cable components shrinkage testing and radiation testing results from recent experiments at Goddard Space Flight Center.

  15. Process for making RF shielded cable connector assemblies and the products formed thereby

    NASA Technical Reports Server (NTRS)

    Fisher, A.; Clatterbuck, C. H. (Inventor)

    1973-01-01

    A process for making RF shielded cable connector assemblies and the resulting structures is described. The process basically consists of potting wires of a shielded cable between the cable shield and a connector housing to fill in, support, regidize, and insulate the individual wires contained in the cable. The formed potting is coated with an electrically conductive material so as to form an entirely encompassing adhering conductive path between the cable shield and the metallic connector housing. A protective jacket is thereby formed over the conductive coating between the cable shield and the connector housing.

  16. ATP-dependent membrane assembly of F-actin facilitates membrane fusion.

    PubMed

    Jahraus, A; Egeberg, M; Hinner, B; Habermann, A; Sackman, E; Pralle, A; Faulstich, H; Rybin, V; Defacque, H; Griffiths, G

    2001-01-01

    We recently established an in vitro assay that monitors the fusion between latex-bead phagosomes and endocytic organelles in the presence of J774 macrophage cytosol (). Here, we show that different reagents affecting the actin cytoskeleton can either inhibit or stimulate this fusion process. Because the membranes of purified phagosomes can assemble F-actin de novo from pure actin with ATP (), we focused here on the ability of membranes to nucleate actin in the presence of J774 cytosolic extracts. For this, we used F-actin sedimentation, pyrene actin assays, and torsional rheometry, a biophysical approach that could provide kinetic information on actin polymerization and gel formation. We make two major conclusions. First, under our standard in vitro conditions (4 mg/ml cytosol and 1 mM ATP), the presence of membranes actively catalyzed the assembly of cytosolic F-actin, which assembled into highly viscoelastic gels. A model is discussed that links these results to how the actin may facilitate fusion. Second, cytosolic actin paradoxically polymerized more under ATP depletion than under high-ATP conditions, even in the absence of membranes; we discuss these data in the context of the well described, large increases in F-actin seen in many cells during ischemia.

  17. The Drosophila javelin Gene Encodes a Novel Actin-Associated Protein Required for Actin Assembly in the Bristle ▿

    PubMed Central

    Shapira, Shira; Bakhrat, Anna; Bitan, Amir; Abdu, Uri

    2011-01-01

    The Drosophila melanogaster bristle is a highly polarized cell that builds specialized cytoskeletal structures. Whereas actin is required for increasing bristle length, microtubules are essential for bristle axial growth. To identify new proteins involved in cytoskeleton organization during bristle development, we focused on identifying and characterizing the javelin (jv) locus. We found that in a jv mutant, the bristle tip is swollen and abnormal organization of bristle grooves is seen over the entire bristle. Using confocal and electron microscopy, we found that in jv mutant bristles, actin bundles do not form properly due to a loss of actin filaments within the bundle. We show that jv is an allele of the predicted CG32397 gene that encodes a protein with no homologs outside insects. Expression of the Jv protein fused to a green fluorescent protein (GFP) shows that the protein is colocalized with actin bundles in the bristle. Moreover, expression of Jv-GFP within the germ line led to the formation of ectopic actin bundles that surround the nucleus of nurse cells. Thus, we report that Jv is a novel actin-associated protein required for actin assembly during Drosophila bristle development. PMID:21930794

  18. Analysis of Production Lead Time for Missile Repair Parts: Contracts Dealing with Cable Assemblies and Wiring Harnesses

    DTIC Science & Technology

    1975-04-01

    contracts dealing with cable assemblies and wiring harnesses . Techniques of regression analysis and graphical analysis were employed on the data observations from thirty cable assembly and wiring harness contracts.

  19. Multiple Myosins Are Required to Coordinate Actin Assembly with Coat Compression during Compensatory Endocytosis

    PubMed Central

    Bement, William M.

    2007-01-01

    Actin is involved in endocytosis in organisms ranging from yeast to mammals. In activated Xenopus eggs, exocytosing cortical granules (CGs) are surrounded by actin “coats,” which compress the exocytosing compartments, resulting in compensatory endocytosis. Here, we examined the roles of two myosins in actin coat compression. Myosin-2 is recruited to exocytosing CGs late in coat compression. Inhibition of myosin-2 slows coat compression without affecting actin assembly. This differs from phenotype induced by inhibition of actin assembly, where exocytosing CGs are trapped at the plasma membrane (PM) completely. Thus, coat compression is likely driven in part by actin assembly itself, but it requires myosin-2 for efficient completion. In contrast to myosin-2, the long-tailed myosin-1e is recruited to exocytosing CGs immediately after egg activation. Perturbation of myosin-1e results in partial actin coat assembly and induces CG collapse into the PM. Intriguingly, simultaneous inhibition of actin assembly and myosin-1e prevents CG collapse. Together, the results show that myosin-1e and myosin-2 are part of an intricate machinery that coordinates coat compression at exocytosing CGs. PMID:17699600

  20. Inhibition of CapZ during myofibrillogenesis alters assembly of actin filaments

    PubMed Central

    1995-01-01

    The actin filaments of myofibrils are highly organized; they are of a uniform length and polarity and are situated in the sarcomere in an aligned array. We hypothesized that the barbed-end actin-binding protein, CapZ, directs the process of actin filament assembly during myofibrillogenesis. We tested this hypothesis by inhibiting the actin- binding activity of CapZ in developing myotubes in culture using two different methods. First, injection of a monoclonal antibody that prevents the interaction of CapZ and actin disrupts the non-striated bundles of actin filaments formed during the early stages of myofibril formation in skeletal myotubes in culture. The antibody, when injected at concentrations lower than that required for disrupting the actin filaments, binds at nascent Z-disks. Since the interaction of CapZ and the monoclonal antibody are mutually exclusive, this result indicates that CapZ binds nascent Z-disks independent of an interaction with actin filaments. In a second approach, expression in myotubes of a mutant form of CapZ that does not bind actin results in a delay in the appearance of actin in a striated pattern in myofibrils. The organization of alpha-actinin at Z-disks also is delayed, but the organization of titin and myosin in sarcomeres is not significantly altered. We conclude that the interaction of CapZ and actin is important for the organization of actin filaments of the sarcomere. PMID:7822423

  1. Profilin-Dependent Nucleation and Assembly of Actin Filaments Controls Cell Elongation in Arabidopsis1[OPEN

    PubMed Central

    Cao, Lingyan; Blanchoin, Laurent; Staiger, Christopher J.

    2016-01-01

    Actin filaments in plant cells are incredibly dynamic; they undergo incessant remodeling and assembly or disassembly within seconds. These dynamic events are choreographed by a plethora of actin-binding proteins, but the exact mechanisms are poorly understood. Here, we dissect the contribution of Arabidopsis (Arabidopsis thaliana) PROFILIN1 (PRF1), a conserved actin monomer-binding protein, to actin organization and single filament dynamics during axial cell expansion of living epidermal cells. We found that reduced PRF1 levels enhanced cell and organ growth. Surprisingly, we observed that the overall frequency of nucleation events in prf1 mutants was dramatically decreased and that a subpopulation of actin filaments that assemble at high rates was reduced. To test whether profilin cooperates with plant formin proteins to execute actin nucleation and rapid filament elongation in cells, we used a pharmacological approach. Here, we used Small Molecule Inhibitor of Formin FH2 (SMIFH2), after validating its mode of action on a plant formin in vitro, and observed a reduced nucleation frequency of actin filaments in live cells. Treatment of wild-type epidermal cells with SMIFH2 mimicked the phenotype of prf1 mutants, and the nucleation frequency in prf1-2 mutant was completely insensitive to these treatments. Our data provide compelling evidence that PRF1 coordinates the stochastic dynamic properties of actin filaments by modulating formin-mediated actin nucleation and assembly during plant cell expansion. PMID:26574597

  2. MARCKS actin-binding capacity mediates actin filament assembly during mitosis in human hepatic stellate cells.

    PubMed

    Rombouts, Krista; Mello, Tommaso; Liotta, Francesco; Galli, Andrea; Caligiuri, Alessandra; Annunziato, Francesco; Pinzani, Massimo

    2012-08-15

    Cross-linking between the actin cytoskeleton and plasma membrane actin-binding proteins is a key interaction responsible for the mechanical properties of the mitotic cell. Little is known about the identity, the localization, and the function of actin filament-binding proteins during mitosis in human hepatic stellate cells (hHSC). The aim of the present study was to identify and analyze the cross talk between actin and myristoylated alanine-rich kinase C substrate (MARCKS), an important PKC substrate and actin filament-binding protein, during mitosis in primary hHSC. Confocal analysis and chromosomal fraction analysis of mitotic hHSC demonstrated that phosphorylated (P)-MARCKS displays distinct phase-dependent localizations, accumulates at the perichromosomal layer, and is a centrosomal protein belonging to the chromosomal cytosolic fraction. Aurora B kinase (AUBK), an important mitotic regulator, β-actin, and P-MARCKS concentrate at the cytokinetic midbody during cleavage furrow formation. This localization is critical since MARCKS-depletion in hHSC is characterized by a significant loss in cytosolic actin filaments and cortical β-actin that induces cell cycle inhibition and dislocation of AUBK. A depletion of AUBK in hHSC affects cell cycle, resulting in multinucleation. Quantitative live cell imaging demonstrates that the actin filament-binding capacity of MARCKS is key to regulate mitosis since the cell cycle inhibitory effect in MARCKS-depleted cells caused abnormal cell morphology and an aberrant cytokinesis, resulting in a significant increase in cell cycle time. These findings implicate that MARCKS, an important PKC substrate, is essential for proper cytokinesis and that MARCKS and its partner actin are key mitotic regulators during cell cycle in hHSC.

  3. Phosphoinositides regulate membrane-dependent actin assembly by latex bead phagosomes.

    PubMed

    Defacque, Hélène; Bos, Evelyne; Garvalov, Boyan; Barret, Cécile; Roy, Christian; Mangeat, Paul; Shin, Hye-Won; Rybin, Vladimir; Griffiths, Gareth

    2002-04-01

    Actin assembly on membrane surfaces is an elusive process in which several phosphoinositides (PIPs) have been implicated. We have reconstituted actin assembly using a defined membrane surface, the latex bead phagosome (LBP), and shown that the PI(4,5)P(2)-binding proteins ezrin and/or moesin were essential for this process (). Here, we provide several lines of evidence that both preexisting and newly synthesized PI(4,5)P(2), and probably PI(4)P, are essential for phagosomal actin assembly; only these PIPs were routinely synthesized from ATP during in vitro actin assembly. Treatment of LBP with phospholipase C or with adenosine, an inhibitor of type II PI 4-kinase, as well as preincubation with anti-PI(4)P or anti-PI(4,5)P(2) antibodies all inhibited this process. Incorporation of extra PI(4)P or PI(4,5)P(2) into the LBP membrane led to a fivefold increase in the number of phagosomes that assemble actin. An ezrin mutant mutated in the PI(4,5)P(2)-binding sites was less efficient in binding to LBPs and in reconstituting actin assembly than wild-type ezrin. Our data show that PI 4- and PI 5-kinase, and under some conditions also PI 3-kinase, activities are present on LBPs and can be activated by ATP, even in the absence of GTP or cytosolic components. However, PI 3-kinase activity is not required for actin assembly, because the process was not affected by PI 3-kinase inhibitors. We suggest that the ezrin-dependent actin assembly on the LBP membrane may require active turnover of D4 and D5 PIPs on the organelle membrane.

  4. Myofibril assembly visualized by imaging N-RAP, alpha-actinin, and actin in living cardiomyocytes.

    PubMed

    Manisastry, Shyam M; Zaal, Kristien J M; Horowits, Robert

    2009-07-15

    N-RAP is a striated muscle-specific scaffolding protein that organizes alpha-actinin and actin into symmetrical I-Z-I structures in developing myofibrils. Here we determined the order of events during myofibril assembly through time-lapse confocal microscopy of cultured embryonic chick cardiomyocytes coexpressing fluorescently tagged N-RAP and either alpha-actinin or actin. During de novo myofibril assembly, N-RAP assembled in fibrillar structures within the cell, with dots of alpha-actinin subsequently organizing along these structures. The initial fibrillar structures were reminiscent of actin fibrils, and coassembly of N-RAP and actin into newly formed fibrils supported this. The alpha-actinin dots subsequently broadened to Z-lines that were wider than the underlying N-RAP fibril, and N-RAP fluorescence intensity decreased. FRAP experiments showed that most of the alpha-actinin dynamically exchanged during all stages of myofibril assembly. In contrast, less than 20% of the N-RAP in premyofibrils was exchanged during 10-20 min after photobleaching, but this value increased to 70% during myofibril maturation. The results show that N-RAP assembles into an actin containing scaffold before alpha-actinin recruitment; that the N-RAP scaffold is much more stable than the assembling structural components; that N-RAP dynamics increase as assembly progresses; and that N-RAP leaves the structure after assembly is complete.

  5. Collapsin Response Mediator Protein-1 Regulates Arp2/3-dependent Actin Assembly*

    PubMed Central

    Yu-Kemp, Hui-Chia; Brieher, William M.

    2016-01-01

    Listeria monocytogenes is a bacterial parasite that uses host proteins to assemble an Arp2/3-dependent actin comet tail to power its movement through the host cell. Initiation of comet tail assembly is more efficient in cytosol than it is under defined conditions, indicating that unknown factors contribute to the reaction. We therefore fractionated cytosol and identified CRMP-1 as a factor that facilitates Arp2/3-dependent Listeria actin cloud formation in the presence of Arp2/3 and actin alone. It also scored as an important factor for Listeria actin comet tail formation in brain cytosol. CRMP-1 does not nucleate actin assembly on its own, nor does it directly activate the Arp2/3 complex. Rather, CRMP-1 scored as an auxiliary factor that promoted the ability of Listeria ActA protein to activate the Arp2/3 complex to trigger actin assembly. CRMP-1 is one member of a family of five related proteins that modulate cell motility in response to extracellular signals. Our results demonstrate an important role for CRMP-1 in Listeria actin comet tail formation and open the possibility that CRMP-1 controls cell motility by modulating Arp2/3 activation. PMID:26598519

  6. X-ray scattering study of actin polymerization nuclei assembled by tandem W domains

    SciTech Connect

    Rebowski, Grzegorz; Boczkowska, Malgorzata; Hayes, David B.; Guo, Liang; Irving, Thomas C.; Dominguez, Roberto

    2008-08-27

    The initiation of actin polymerization in cells requires actin filament nucleators. With the exception of formins, known filament nucleators use the Wiskott-Aldrich syndrome protein (WASP) homology 2 (WH2 or W) domain for interaction with actin. A common architecture, found in Spire, Cobl, VopL, and VopF, consists of tandem W domains that tie together three to four actin monomers to form a polymerization nucleus. Uncontrollable polymerization has prevented the structural investigation of such nuclei. We have engineered stable nuclei consisting of an actin dimer and a trimer stabilized by tandem W domain hybrid constructs and studied their structures in solution by x-ray scattering. We show that Spire-like tandem W domains stabilize a polymerization nucleus by lining up actin subunits along the long-pitch helix of the actin filament. Intersubunit contacts in the polymerization nucleus, thought to involve the DNase I-binding loop of actin, coexist with the binding of the W domain in the cleft between actin subdomains 1 and 3. The successful stabilization of filament-like multiactin assemblies opens the way to the crystallographic investigation of intersubunit contacts in the actin filament.

  7. Effects of recombinant baculovirus AcMNPV-BmK IT on the formation of early cables and nuclear polymerization of actin in Sf9 cells.

    PubMed

    Fu, Yuejun; Lin, Taotao; Liang, Aihua; Hu, Fengyun

    2016-05-01

    Autographa californica nuclearpoly hedrosis virus (AcMNPV) is one of the most important baculoviridae. However, the application of AcMNPV as a biocontrol agent has been limited. Previously, we engineered Buthus martensii Karsch insect toxin (BmK IT) gene into the genome of AcMNPV. The bioassay data indicated that the recombinant baculovirus AcMNPV-BmK IT significantly enhanced the anti-insect efficacy of the virus. The actin cytoskeleton is the major component beneath the surface of eukaryotic cells. In this report, the effects of AcMNPV-BmK IT on the formation of early cables of actin and nuclear filamentous-actin (F-actin) were studied. The results indicated that these baculovirus induced rearrangement of the actin cytoskeleton of host cells during infection and actin might participate in the transportation of baculovirus from cytoplasm to the nuclei. AcMNPV-BmK IT delayed the formation of early cables of actin and nuclear F-actin and accelerated the clearance of actin in the nuclei.

  8. WAVE binds Ena/VASP for enhanced Arp2/3 complex–based actin assembly

    PubMed Central

    Havrylenko, Svitlana; Noguera, Philippe; Abou-Ghali, Majdouline; Manzi, John; Faqir, Fahima; Lamora, Audrey; Guérin, Christophe; Blanchoin, Laurent; Plastino, Julie

    2015-01-01

    The WAVE complex is the main activator of the Arp2/3 complex for actin filament nucleation and assembly in the lamellipodia of moving cells. Other important players in lamellipodial protrusion are Ena/VASP proteins, which enhance actin filament elongation. Here we examine the molecular coordination between the nucleating activity of the Arp2/3 complex and the elongating activity of Ena/VASP proteins for the formation of actin networks. Using an in vitro bead motility assay, we show that WAVE directly binds VASP, resulting in an increase in Arp2/3 complex–based actin assembly. We show that this interaction is important in vivo as well, for the formation of lamellipodia during the ventral enclosure event of Caenorhabditis elegans embryogenesis. Ena/VASP's ability to bind F-actin and profilin-complexed G-actin are important for its effect, whereas Ena/VASP tetramerization is not necessary. Our data are consistent with the idea that binding of Ena/VASP to WAVE potentiates Arp2/3 complex activity and lamellipodial actin assembly. PMID:25355952

  9. Actin-myosin network is required for proper assembly of influenza virus particles

    SciTech Connect

    Kumakura, Michiko; Kawaguchi, Atsushi Nagata, Kyosuke

    2015-02-15

    Actin filaments are known to play a central role in cellular dynamics. After polymerization of actin, various actin-crosslinking proteins including non-muscle myosin II facilitate the formation of spatially organized actin filament networks. The actin-myosin network is highly expanded beneath plasma membrane. The genome of influenza virus (vRNA) replicates in the cell nucleus. Then, newly synthesized vRNAs are nuclear-exported to the cytoplasm as ribonucleoprotein complexes (vRNPs), followed by transport to the beneath plasma membrane where virus particles assemble. Here, we found that, by inhibiting actin-myosin network formation, the virus titer tends to be reduced and HA viral spike protein is aggregated on the plasma membrane. These results indicate that the actin-myosin network plays an important role in the virus formation. - Highlights: • Actin-myosin network is important for the influenza virus production. • HA forms aggregations at the plasma membrane in the presence of blebbistatin. • M1 is recruited to the budding site through the actin-myosin network.

  10. Rocket launcher mechanism of collaborative actin assembly defined by single-molecule imaging.

    PubMed

    Breitsprecher, Dennis; Jaiswal, Richa; Bombardier, Jeffrey P; Gould, Christopher J; Gelles, Jeff; Goode, Bruce L

    2012-06-01

    Interacting sets of actin assembly factors work together in cells, but the underlying mechanisms have remained obscure. We used triple-color single-molecule fluorescence microscopy to image the tumor suppressor adenomatous polyposis coli (APC) and the formin mDia1 during filament assembly. Complexes consisting of APC, mDia1, and actin monomers initiated actin filament formation, overcoming inhibition by capping protein and profilin. Upon filament polymerization, the complexes separated, with mDia1 moving processively on growing barbed ends while APC remained at the site of nucleation. Thus, the two assembly factors directly interact to initiate filament assembly and then separate but retain independent associations with either end of the growing filament.

  11. Repeated Cycles of Rapid Actin Assembly and Disassembly on Epithelial Cell PhagosomesV⃞

    PubMed Central

    Yam, Patricia T.; Theriot, Julie A.

    2004-01-01

    We have found that early in infection of the intracellular pathogen Listeria monocytogenes in Madin-Darby canine kidney epithelial cells expressing actin conjugated to green fluorescent protein, F-actin rapidly assembles (∼25 s) and disassembles (∼30 s) around the bacteria, a phenomenon we call flashing. L. monocytogenes strains unable to perform actin-based motility or unable to escape the phagosome were capable of flashing, suggesting that the actin assembly occurs on the phagosome membrane. Cycles of actin assembly and disassembly could occur repeatedly on the same phagosome. Indirect immunofluorescence showed that most bacteria were fully internalized when flashing occurred, suggesting that actin flashing does not represent phagocytosis. Escherichia coli expressing invA, a gene product from Yersinia pseudotuberculosis that mediates cellular invasion, also induced flashing. Furthermore, polystyrene beads coated with E-cadherin or transferrin also induced flashing after internalization. This suggests that flashing occurs downstream of several distinct molecular entry mechanisms and may be a general consequence of internalization of large objects by epithelial cells. PMID:15456901

  12. Fission yeast profilin is tailored to facilitate actin assembly by the cytokinesis formin Cdc12.

    PubMed

    Bestul, Andrew J; Christensen, Jenna R; Grzegorzewska, Agnieszka P; Burke, Thomas A; Sees, Jennifer A; Carroll, Robert T; Sirotkin, Vladimir; Keenan, Robert J; Kovar, David R

    2015-01-15

    The evolutionarily conserved small actin-monomer binding protein profilin is believed to be a housekeeping factor that maintains a general pool of unassembled actin. However, despite similar primary sequences, structural folds, and affinities for G-actin and poly-L-proline, budding yeast profilin ScPFY fails to complement fission yeast profilin SpPRF temperature-sensitive mutant cdc3-124 cells. To identify profilin's essential properties, we built a combinatorial library of ScPFY variants containing either WT or SpPRF residues at multiple positions and carried out a genetic selection to isolate variants that support life in fission yeast. We subsequently engineered ScPFY(9-Mut), a variant containing nine substitutions in the actin-binding region, which complements cdc3-124 cells. ScPFY(9-Mut), but not WT ScPFY, suppresses severe cytokinesis defects in cdc3-124 cells. Furthermore, the major activity rescued by ScPFY(9-Mut) is the ability to enhance cytokinesis formin Cdc12-mediated actin assembly in vitro, which allows cells to assemble functional contractile rings. Therefore an essential role of profilin is to specifically facilitate formin-mediated actin assembly for cytokinesis in fission yeast.

  13. Control of actin filament dynamics at barbed ends by WH2 domains: from capping to permissive and processive assembly.

    PubMed

    Carlier, Marie-France; Pernier, Julien; Avvaru, Balendu Sankara

    2013-10-01

    WH2 domains are multifunctional regulators of actin assembly that can either sequester G-actin or allow polarized barbed end growth. They all bind similarly to a hydrophobic pocket at the barbed face of actin. Depending on their electrostatic environment, WH2 domains can nucleate actin assembly by facilitating the formation of prenuclei dimers along the canonical spontaneous assembly pathway. They also modulate filament barbed end dynamics in a versatile fashion, acting either as barbed end cappers or assisting barbed end growth like profilin or uncapping barbed ends and potentially mediating processive elongation like formins when they are dimerized. Tandem repeats of WH2 domains can sever filaments and either remain bound to created barbed ends like gelsolin, or strip off an ADP-actin subunit from the severed polymer end, depending on their relative affinity for terminal ADP-F-actin or ADP-G-actin. In summary, WH2 domains recapitulate all known elementary regulatory functions so far found in individual actin-binding proteins. By combining different discrete sets of these multifunctional properties, they acquire specific functions in various actin-based processes, and participate in activities as diverse as filament branching, filopodia extension, or actin remodeling in ciliogenesis and asymmetric meiotic division. They also integrate these functions with other actin-binding motifs present either in the same protein or in a complex with another protein, expanding the range of complexity in actin regulation. The details of their molecular mechanisms and the underlying structural basis provide exciting avenues in actin research.

  14. CAS-1, a C. elegans cyclase-associated protein, is required for sarcomeric actin assembly in striated muscle.

    PubMed

    Nomura, Kazumi; Ono, Kanako; Ono, Shoichiro

    2012-09-01

    Assembly of contractile apparatuses in striated muscle requires precisely regulated reorganization of the actin cytoskeletal proteins into sarcomeric organization. Regulation of actin filament dynamics is one of the essential processes of myofibril assembly, but the mechanism of actin regulation in striated muscle is not clearly understood. Actin depolymerizing factor (ADF)/cofilin is a key enhancer of actin filament dynamics in striated muscle in both vertebrates and nematodes. Here, we report that CAS-1, a cyclase-associated protein in Caenorhabditis elegans, promotes ADF/cofilin-dependent actin filament turnover in vitro and is required for sarcomeric actin organization in striated muscle. CAS-1 is predominantly expressed in striated muscle from embryos to adults. In vitro, CAS-1 binds to actin monomers and enhances exchange of actin-bound ATP/ADP even in the presence of UNC-60B, a muscle-specific ADF/cofilin that inhibits the nucleotide exchange. As a result, CAS-1 and UNC-60B cooperatively enhance actin filament turnover. The two proteins also cooperate to shorten actin filaments. A cas-1 mutation is homozygous lethal with defects in sarcomeric actin organization. cas-1-mutant embryos and worms have aggregates of actin in muscle cells, and UNC-60B is mislocalized to the aggregates. These results provide genetic and biochemical evidence that cyclase-associated protein is a critical regulator of sarcomeric actin organization in striated muscle.

  15. Antagonistic regulation of F-BAR protein assemblies controls actin polymerization during podosome formation.

    PubMed

    Tsujita, Kazuya; Kondo, Akihiro; Kurisu, Shusaku; Hasegawa, Junya; Itoh, Toshiki; Takenawa, Tadaomi

    2013-05-15

    FBP17, an F-BAR domain protein, has emerged as a crucial factor linking the plasma membrane to WASP-mediated actin polymerization. Although it is well established that FBP17 has a powerful self-polymerizing ability that promotes actin nucleation on membranes in vitro, knowledge of inhibitory factors that counteract this activity in vivo is limited. Here, we demonstrate that the assembly of FBP17 on the plasma membranes is antagonized by PSTPIP2, another F-BAR protein implicated in auto-inflammatory disorder. Knockdown of PSTPIP2 in macrophage promotes the assembly of FBP17 as well as subsequent actin nucleation at podosomes, resulting in an enhancement of matrix degradation. This phenotype is rescued by expression of PSTPIP2 in a manner dependent on its F-BAR domain. Time-lapse total internal reflection fluorescence (TIRF) microscopy observations reveal that the self-assembly of FBP17 at the podosomal membrane initiates actin polymerization, whereas the clustering of PSTPIP2 has an opposite effect. Biochemical analysis and live-cell imaging show that PSTPIP2 inhibits actin polymerization by competing with FBP17 for assembly at artificial as well as the plasma membrane. Interestingly, the assembly of FBP17 is dependent on WASP, and its dissociation by WASP inhibition strongly induces a self-organization of PSTPIP2 at podosomes. Thus, our data uncover a previously unappreciated antagonism between different F-BAR domain assemblies that determines the threshold of actin polymerization for the formation of functional podosomes and may explain how the absence of PSTPIP2 causes auto-inflammatory disorder.

  16. The integral membrane protein, ponticulin, acts as a monomer in nucleating actin assembly

    PubMed Central

    1993-01-01

    Ponticulin, an F-actin binding transmembrane glycoprotein in Dictyostelium plasma membranes, was isolated by detergent extraction from cytoskeletons and purified to homogeneity. Ponticulin is an abundant membrane protein, averaging approximately 10(6) copies/cell, with an estimated surface density of approximately 300 per microns2. Ponticulin solubilized in octylglucoside exhibited hydrodynamic properties consistent with a ponticulin monomer in a spherical or slightly ellipsoidal detergent micelle with a total molecular mass of 56 +/- 6 kD. Purified ponticulin nucleated actin polymerization when reconstituted into Dictyostelium lipid vesicles, but not when a number of commercially available lipids and lipid mixtures were substituted for the endogenous lipid. The specific activity was consistent with that expected for a protein comprising 0.7 +/- 0.4%, by mass, of the plasma membrane protein. Ponticulin in octylglucoside micelles bound F- actin but did not nucleate actin assembly. Thus, ponticulin-mediated nucleation activity was sensitive to the lipid environment, a result frequently observed with transmembrane proteins. At most concentrations of Dictyostelium lipid, nucleation activity increased linearly with increasing amounts of ponticulin, suggesting that the nucleating species is a ponticulin monomer. Consistent with previous observations of lateral interactions between actin filaments and Dictyostelium plasma membranes, both ends of ponticulin-nucleated actin filaments appeared to be free for monomer assembly and disassembly. Our results indicate that ponticulin is a major membrane protein in Dictyostelium and that, in the proper lipid matrix, it is sufficient for lateral nucleation of actin assembly. To date, ponticulin is the only integral membrane protein known to directly nucleate actin polymerization. PMID:8432731

  17. Nano-assembly of nanodiamonds by conjugation to actin filaments.

    PubMed

    Bradac, Carlo; Say, Jana M; Rastogi, Ishan D; Cordina, Nicole M; Volz, Thomas; Brown, Louise J

    2016-03-01

    Fluorescent nanodiamonds (NDs) are remarkable objects. They possess unique mechanical and optical properties combined with high surface areas and controllable surface reactivity. They are non-toxic and hence suited for use in biological environments. NDs are also readily available and commercially inexpensive. Here, the exceptional capability of controlling and tailoring their surface chemistry is demonstrated. Small, bright diamond nanocrystals (size ˜30 nm) are conjugated to protein filaments of actin (length ˜3-7 µm). The conjugation to actin filaments is extremely selective and highly target-specific. These unique features, together with the relative simplicity of the conjugation-targeting method, make functionalised nanodiamonds a powerful and versatile platform in biomedicine and quantum nanotechnologies. Applications ranging from using NDs as superior biological markers to, potentially, developing novel bottom-up approaches for the fabrication of hybrid quantum devices that would bridge across the bio/solid-state interface are presented and discussed.

  18. Junctional actin assembly is mediated by Formin-like 2 downstream of Rac1

    PubMed Central

    Grikscheit, Katharina; Frank, Tanja; Wang, Ying

    2015-01-01

    Epithelial integrity is vitally important, and its deregulation causes early stage cancer. De novo formation of an adherens junction (AJ) between single epithelial cells requires coordinated, spatial actin dynamics, but the mechanisms steering nascent actin polymerization for cell–cell adhesion initiation are not well understood. Here we investigated real-time actin assembly during daughter cell–cell adhesion formation in human breast epithelial cells in 3D environments. We identify formin-like 2 (FMNL2) as being specifically required for actin assembly and turnover at newly formed cell–cell contacts as well as for human epithelial lumen formation. FMNL2 associates with components of the AJ complex involving Rac1 activity and the FMNL2 C terminus. Optogenetic control of Rac1 in living cells rapidly drove FMNL2 to epithelial cell–cell contact zones. Furthermore, Rac1-induced actin assembly and subsequent AJ formation critically depends on FMNL2. These data uncover FMNL2 as a driver for human epithelial AJ formation downstream of Rac1. PMID:25963818

  19. Shielding of the Geomagnetic Field Alters Actin Assembly and Inhibits Cell Motility in Human Neuroblastoma Cells

    PubMed Central

    Mo, Wei-Chuan; Zhang, Zi-Jian; Wang, Dong-Liang; Liu, Ying; Bartlett, Perry F.; He, Rong-Qiao

    2016-01-01

    Accumulating evidence has shown that absence of the geomagnetic field (GMF), the so-called hypomagnetic field (HMF) environment, alters the biological functions in seemingly non-magnetosensitive cells and organisms, which indicates that the GMF could be sensed by non-iron-rich and non-photo-sensing cells. The underlying mechanisms of the HMF effects on those cells are closely related to their GMF sensation but remain poorly understood so far. Previously, we found that the HMF represses expressions of genes associated with cell migration and cytoskeleton assembly in human neuroblastoma cells (SH-SY5Y cell line). Here, we measured the HMF-induced changes on cell morphology, adhesion, motility and actin cytoskeleton in SH-SY5Y cells. The HMF inhibited cell adhesion and migration accompanied with a reduction in cellular F-actin amount. Moreover, following exposure to the HMF, the number of cell processes was reduced and cells were smaller in size and more round in shape. Furthermore, disordered kinetics of actin assembly in vitro were observed during exposure to the HMF, as evidenced by the presence of granule and meshed products. These results indicate that elimination of the GMF affects assembly of the motility-related actin cytoskeleton, and suggest that F-actin is a target of HMF exposure and probably a mediator of GMF sensation. PMID:27029216

  20. Space flight qualification on a multifiber ribbon cable and array connector assembly

    NASA Astrophysics Data System (ADS)

    Jin, Xiaodan; Ott, Melanie N.; LaRocca, Frank V.; Baker, Ronald M.; Keeler, Bianca E. N.; Friedberg, Patricia R.; Chuska, Richard F.; Malenab, Mary C.; Macmurphy, Shawn L.

    2006-09-01

    NASA's Goddard Space Flight Center (GSFC) cooperatively with Sandia National Laboratories completed a series of tests on three separate configurations of multi-fiber ribbon cable and MTP connector assemblies. These tests simulate the aging process of components during launch and long-term space environmental exposure. The multi-fiber ribbon cable assembly was constructed of non-outgassing materials, with radiation-hardened, graded index 100/140-micron optical fiber. The results of this characterization presented here include vibration testing, thermal vacuum monitoring, and extended radiation exposure testing data.

  1. Space Flight Qualification on a Multi-Fiber Ribbon Cable and Array Connector Assembly

    NASA Technical Reports Server (NTRS)

    Xiaodan, Linda Jin; Ott, Melanie N.; LaRocca, Frank V.; Baker, Ronald M.; Keeler, Bianca E. N.; Friedberg, Patricia R.; Chuska, Richard F.; Malenab, Mary C.; Macmurphy, Shawn L.

    2006-01-01

    NASA's Goddard Space Flight Center (GSFC) cooperatively with Sandia National Laboratories completed a series of tests on three separate configurations of multi-fiber ribbon cable and MTP connector assemblies. These tests simulate the aging process of components during launch and long-term space environmental exposure. The multi-fiber ribbon cable assembly was constructed of non-outgassing materials, with radiation-hardened, graded index 100/140-micron optical fiber. The results of this characterization presented here include vibration testing, thermal vacuum monitoring, and extended radiation exposure testing data.

  2. Actin-Interacting Protein 1 Contributes to Intranuclear Rod Assembly in Dictyostelium discoideum

    PubMed Central

    Ishikawa-Ankerhold, Hellen C.; Daszkiewicz, Wioleta; Schleicher, Michael; Müller-Taubenberger, Annette

    2017-01-01

    Intranuclear rods are aggregates consisting of actin and cofilin that are formed in the nucleus in consequence of chemical or mechanical stress conditions. The formation of rods is implicated in a variety of pathological conditions, such as certain myopathies and some neurological disorders. It is still not well understood what exactly triggers the formation of intranuclear rods, whether other proteins are involved, and what the underlying mechanisms of rod assembly or disassembly are. In this study, Dictyostelium discoideum was used to examine appearance, stages of assembly, composition, stability, and dismantling of rods. Our data show that intranuclear rods, in addition to actin and cofilin, are composed of a distinct set of other proteins comprising actin-interacting protein 1 (Aip1), coronin (CorA), filactin (Fia), and the 34 kDa actin-bundling protein B (AbpB). A finely tuned spatio-temporal pattern of protein recruitment was found during formation of rods. Aip1 is important for the final state of rod compaction indicating that Aip1 plays a major role in shaping the intranuclear rods. In the absence of both Aip1 and CorA, rods are not formed in the nucleus, suggesting that a sufficient supply of monomeric actin is a prerequisite for rod formation. PMID:28074884

  3. Nervous Wreck and Cdc42 cooperate to regulate endocytic actin assembly during synaptic growth

    PubMed Central

    Rodal, Avital A.; Motola-Barnes, Rebecca N.; Littleton, J. Troy

    2008-01-01

    Regulation of synaptic morphology depends on endocytosis of activated growth signal receptors, but the mechanisms regulating this membrane trafficking event are unclear. Actin polymerization mediated by WASp (Wiskott-Aldrich Syndrome Protein) and the Arp2/3 (Actin related protein 2/3) complex generates forces at multiple stages of endocytosis. F-BAR/SH3 domain proteins play key roles in this process by coordinating membrane deformation with WASp-dependent actin polymerization. However, it is not known how other WASp ligands, such as the small GTPase Cdc42, coordinate with F-BAR/SH3 proteins to regulate actin polymerization at membranes. Nervous Wreck (Nwk) is a conserved neuronal F-BAR/SH3 protein that localizes to periactive zones at the Drosophila larval neuromuscular junction (NMJ) and is required for regulation of synaptic growth via BMP signaling. Here we show that Nwk interacts with the endocytic proteins dynamin and Dap160 and functions together with Cdc42 to promote WASp-mediated actin polymerization in vitro and to regulate synaptic growth in vivo. Cdc42 function is associated with Rab11-dependent recycling endosomes, and we show that Rab11 co-localizes with Nwk at the NMJ. Taken together, our results suggest that synaptic growth activated by growth factor signaling is controlled at an endosomal compartment via coordinated Nwk and Cdc42-dependent actin assembly. PMID:18701694

  4. Membrane Tension Acts Through PLD2 and mTORC2 to Limit Actin Network Assembly During Neutrophil Migration

    PubMed Central

    Diz-Muñoz, Alba; Thurley, Kevin; Chintamen, Sana; Altschuler, Steven J.; Fletcher, Daniel A.; Weiner, Orion D.

    2016-01-01

    For efficient polarity and migration, cells need to regulate the magnitude and spatial distribution of actin assembly. This process is coordinated by reciprocal interactions between the actin cytoskeleton and mechanical forces. Actin polymerization-based protrusion increases tension in the plasma membrane, which in turn acts as a long-range inhibitor of actin assembly. These interactions form a negative feedback circuit that limits the magnitude of membrane tension in neutrophils and prevents expansion of the existing front and the formation of secondary fronts. It has been suggested that the plasma membrane directly inhibits actin assembly by serving as a physical barrier that opposes protrusion. Here we show that efficient control of actin polymerization-based protrusion requires an additional mechanosensory feedback cascade that indirectly links membrane tension with actin assembly. Specifically, elevated membrane tension acts through phospholipase D2 (PLD2) and the mammalian target of rapamycin complex 2 (mTORC2) to limit actin nucleation. In the absence of this pathway, neutrophils exhibit larger leading edges, higher membrane tension, and profoundly defective chemotaxis. Mathematical modeling suggests roles for both the direct (mechanical) and indirect (biochemical via PLD2 and mTORC2) feedback loops in organizing cell polarity and motility—the indirect loop is better suited to enable competition between fronts, whereas the direct loop helps spatially organize actin nucleation for efficient leading edge formation and cell movement. This circuit is essential for polarity, motility, and the control of membrane tension. PMID:27280401

  5. F-actin bundles in Drosophila bristles are assembled from modules composed of short filaments

    PubMed Central

    1996-01-01

    The actin bundles in Drosophila bristles run the length of the bristle cell and are accordingly 65 microns (microchaetes) or 400 microns (macrochaetes) in length, depending on the bristle type. Shortly after completion of bristle elongation in pupae, the actin bundles break down as the bristle surface becomes chitinized. The bundles break down in a bizarre way; it is as if each bundle is sawed transversely into pieces that average 3 microns in length. Disassembly of the actin filaments proceeds at the "sawed" surfaces. In all cases, the cuts in adjacent bundles appear in transverse register. From these images, we suspected that each actin bundle is made up of a series of shorter bundles or modules that are attached end-to-end. With fluorescent phalloidin staining and serial thin sections, we show that the modular design is present in nondegenerating bundles. Decoration of the actin filaments in adjacent bundles in the same bristle with subfragment 1 of myosin reveals that the actin filaments in every module have the same polarity. To study how modules form developmentally, we sectioned newly formed and elongating bristles. At the bristle tip are numerous tiny clusters of 6-10 filaments. These clusters become connected together more basally to form filament bundles that are poorly organized, initially, but with time become maximally cross-linked. Additional filaments are then added to the periphery of these organized bundle modules. All these observations make us aware of a new mechanism for the formation and elongation of actin filament bundles, one in which short bundles are assembled and attached end-to-end to other short bundles, as are the vertical girders between the floors of a skyscraper. PMID:8947552

  6. Actin-interacting protein 1 controls assembly and permeability of intestinal epithelial apical junctions

    PubMed Central

    Baranwal, Somesh

    2015-01-01

    Adherens junctions (AJs) and tight junctions (TJs) are crucial regulators of the integrity and restitution of the intestinal epithelial barrier. The structure and function of epithelial junctions depend on their association with the cortical actin cytoskeleton that, in polarized epithelial cells, is represented by a prominent perijunctional actomyosin belt. The assembly and stability of the perijunctional cytoskeleton is controlled by constant turnover (disassembly and reassembly) of actin filaments. Actin-interacting protein (Aip) 1 is an emerging regulator of the actin cytoskeleton, playing a critical role in filament disassembly. In this study, we examined the roles of Aip1 in regulating the structure and remodeling of AJs and TJs in human intestinal epithelium. Aip1 was enriched at apical junctions in polarized human intestinal epithelial cells and normal mouse colonic mucosa. Knockdown of Aip1 by RNA interference increased the paracellular permeability of epithelial cell monolayers, decreased recruitment of AJ/TJ proteins to steady-state intercellular contacts, and attenuated junctional reassembly in a calcium-switch model. The observed defects of AJ/TJ structure and functions were accompanied by abnormal organization and dynamics of the perijunctional F-actin cytoskeleton. Moreover, loss of Aip1 impaired the apico-basal polarity of intestinal epithelial cell monolayers and inhibited formation of polarized epithelial cysts in 3-D Matrigel. Our findings demonstrate a previously unanticipated role of Aip1 in regulating the structure and remodeling of intestinal epithelial junctions and early steps of epithelial morphogenesis. PMID:25792565

  7. Arf6 coordinates actin assembly through the WAVE complex, a mechanism usurped by Salmonella to invade host cells

    PubMed Central

    Humphreys, Daniel; Davidson, Anthony C.; Hume, Peter J.; Makin, Laura E.; Koronakis, Vassilis

    2013-01-01

    ADP ribosylation factor (Arf) 6 anchors to the plasma membrane, where it coordinates membrane trafficking and cytoskeleton remodelling, but how it assembles actin filaments is unknown. By reconstituting membrane-associated actin assembly mediated by the WASP family veroprolin homolog (WAVE) regulatory complex (WRC), we recapitulated an Arf6-driven actin polymerization pathway. We show that Arf6 is divergent from other Arf members, as it was incapable of directly recruiting WRC. We demonstrate that Arf6 triggers actin assembly at the membrane indirectly by recruiting the Arf guanine nucleotide exchange factor (GEF) ARNO that activates Arf1 to enable WRC-dependent actin assembly. The pathogen Salmonella usurped Arf6 for host cell invasion by recruiting its canonical GEFs EFA6 and BRAG2. Arf6 and its GEFs facilitated membrane ruffling and pathogen invasion via ARNO, and triggered actin assembly by generating an Arf1–WRC signaling hub at the membrane in vitro and in cells. This study reconstitutes Arf6-dependent actin assembly to reveal a mechanism by which related Arf GTPases orchestrate distinct steps in the WRC cytoskeleton remodelling pathway. PMID:24085844

  8. How a single residue in individual β-thymosin/WH2 domains controls their functions in actin assembly

    PubMed Central

    Didry, Dominique; Cantrelle, Francois-Xavier; Husson, Clotilde; Roblin, Pierre; Moorthy, Anna M Eswara; Perez, Javier; Le Clainche, Christophe; Hertzog, Maud; Guittet, Eric; Carlier, Marie-France; van Heijenoort, Carine; Renault, Louis

    2012-01-01

    β-Thymosin (βT) and WH2 domains are widespread, intrinsically disordered actin-binding peptides that display significant sequence variability and different regulations of actin self-assembly in motile and morphogenetic processes. Here, we reveal the structural mechanisms by which, in their 1:1 stoichiometric complexes with actin, they either inhibit assembly by sequestering actin monomers like Thymosin-β4, or enhance motility by directing polarized filament assembly like Ciboulot βT. We combined mutational, functional or structural analysis by X-ray crystallography, SAXS (small angle X-ray scattering) and NMR on Thymosin-β4, Ciboulot, TetraThymosinβ and the long WH2 domain of WASP-interacting protein. The latter sequesters G-actin with the same molecular mechanisms as Thymosin-β4. Functionally different βT/WH2 domains differ by distinct dynamics of their C-terminal half interactions with G-actin pointed face. These C-terminal interaction dynamics are controlled by the strength of electrostatic interactions with G-actin. At physiological ionic strength, a single salt bridge with actin located next to their central LKKT/V motif induces G-actin sequestration in both isolated long βT and WH2 domains. The results open perspectives for elucidating the functions of βT/WH2 domains in other modular proteins. PMID:22193718

  9. Roebel assembled coated conductor cables (RACC): Ac-Losses and current carrying potential

    NASA Astrophysics Data System (ADS)

    Frank, A.; Heller, R.; Goldacker, W.; Kling, A.; Schmidt, C.

    2008-02-01

    Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature in the range 50-77 K. Ac-field applications require cables with low ac-losses and hence twisting of the individual strands. We solved this problem using the Roebel technique. Short lengths of Roebel bar cables were prepared from industrial DyBCO and YBCO-CC. Meander shaped tapes of 4 or 5 mm width with twist pitches of 123 or 127 mm were cut from the 10 or 12 mm wide CC tapes using a specially designed tool. Eleven or twelve of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac-field were measured as a function of frequency and field amplitude as well as the coupling current decay time constant. We discuss the results in terms of available theories and compare measured time constants in transverse field with measured coupling losses. Finally the potential of this cable type for ac-use is discussed with respect to ac-losses and current carrying capability.

  10. erythro-9-[3-(2-Hydroxynonyl)]adenine is an effective inhibitor of cell motility and actin assembly.

    PubMed Central

    Schliwa, M; Ezzell, R M; Euteneuer, U

    1984-01-01

    erythro-9-[3-(2-Hydroxynonyl)]adenine (EHNA) has been reported previously to be an agent that arrests sperm motility by inhibiting the axonemal dynein ATPase activity and has been used to probe the involvement of putative cytoplasmic dyneins in mitosis and intracellular organelle transport. We report here that EHNA profoundly and reversibly affects several actin-dependent processes, both in vivo and in vitro. It induces dramatic changes in actin organization in cultured cells, inhibits cell translocation, blocks actin-dependent cytoplasmic streaming, interferes with actin-dependent gelation of cytoplasmic extracts, and inhibits actin assembly. Just as the cytochalasins, EHNA appears to be a highly effective inhibitor of actin-based motility, whose effects in complex biological systems should be interpreted with caution. Images PMID:6385006

  11. Dynamin 2 is required for actin assembly in phagocytosis in Sertoli cells

    SciTech Connect

    Otsuka, Atsushi; Abe, Tadashi; Watanabe, Masami; Yagisawa, Hitoshi; Takei, Kohji; Yamada, Hiroshi

    2009-01-16

    Dynamin 2 has been reported to be implicated in phagocytosis. However, the mode of action of dynamin is poorly understood. In this study, we examined whether dynamin 2 participates in actin assembly during phagocytosis in Sertoli cells. In the presence of dynasore, a dynamin inhibitor, phagocytosis was reduced by 60-70% in Sertoli cells and macrophages. Scanning electron microscopy revealed that Sertoli cells treated with dynasore were unable to form phagocytic cups. In addition, dysfunction of dynamin 2 reduced both actin polymerization and recruitment of actin and dynamin 2 to phosphatidylinositol (4,5) bisphosphate [PI(4,5)P{sub 2}]-containing liposomes. The formation of dynamin 2-positive ruffles of Sertoli cells was decreased by 60-70% by sequestering PI(4,5)P{sub 2} either by expression of PH domain of PLC{delta} or treatment with neomycin. These results strongly suggest that dynamin 2 is involved in actin dynamics and the formation of dynamin 2-positive ruffles during phagocytosis.

  12. Unusual Kinetic and Structural Properties Control Rapid Assembly and Turnover of Actin in the Parasite Toxoplasma gondiiD⃞

    PubMed Central

    Sahoo, Nivedita; Beatty, Wandy; Heuser, John; Sept, David; Sibley, L. David

    2006-01-01

    Toxoplasma is a protozoan parasite in the phylum Apicomplexa, which contains a number of medically important parasites that rely on a highly unusual form of motility termed gliding to actively penetrate their host cells. Parasite actin filaments regulate gliding motility, yet paradoxically filamentous actin is rarely detected in these parasites. To investigate the kinetics of this unusual parasite actin, we expressed TgACT1 in baculovirus and purified it to homogeneity. Biochemical analysis showed that Toxoplasma actin (TgACT1) rapidly polymerized into filaments at a critical concentration that was 3-4-fold lower than conventional actins, yet it failed to copolymerize with mammalian actin. Electron microscopic analysis revealed that TgACT1 filaments were 10 times shorter and less stable than rabbit actin. Phylogenetic comparison of actins revealed a limited number of apicomplexan-specific residues that likely govern the unusual behavior of parasite actin. Molecular modeling identified several key alterations that affect interactions between monomers and that are predicted to destabilize filaments. Our findings suggest that conserved molecular differences in parasite actin favor rapid cycles of assembly and disassembly that govern the unusual form of gliding motility utilized by apicomplexans. PMID:16319175

  13. Microinjected fluorescent phalloidin in vivo reveals the F-actin dynamics and assembly in higher plant mitotic cells.

    PubMed Central

    Schmit, A C; Lambert, A M

    1990-01-01

    Endosperm mitotic cells microinjected with fluorescent phalloidin enabled us to follow the in vivo dynamics of the F-actin cytoskeleton. The fluorescent probe immediately bound to plant microfilaments. First, we investigated the active rearrangement of F-actin during chromosome migration, which appeared to be slowed down in the presence of phalloidin. These findings were compared with the actin patterns observed in mitotic cells fixed at different stages. Our second aim was to determine the origin of the actin filaments that appear at the equator during anaphase-telophase transition. It is not clear whether this F-actin is newly assembled at the end of mitosis and could control plant cytokinesis or whether it corresponds to a passive redistribution of broken polymers in response to microtubule dynamics. We microinjected the same cells twice, first in metaphase with rhodamine-phalloidin and then in late anaphase with fluorescein isothiocyanate-phalloidin. This technique enabled us to visualize two F-actin populations that are not co-localized, suggesting that actin is newly assembled during cell plate development. These in vivo data shed new light on the role of actin in plant mitosis and cytokinesis. PMID:2136631

  14. Mammalian homolog of the yeast cyclase associated protein, CAP/Srv2p, regulates actin filament assembly.

    PubMed

    Freeman, N L; Field, J

    2000-02-01

    Control of cell shape and motility requires rearrangements of the actin cytoskeleton. One cytoskeletal protein that may regulate actin dynamics is CAP (cyclase associated protein; CAP/Srv2p; ASP-56). CAP was first isolated from yeast as an adenylyl cyclase associated protein required for RAS regulation of cAMP signaling. In addition, CAP also regulates the actin cytoskeleton primarily through an actin monomer binding activity. CAP homologs are found in many eukaryotes, including mammals where they also bind actin, but little is known about their biological function. We, therefore, designed experiments to address CAP1 regulation of the actin cytoskeleton. CAP1 localized to membrane ruffles and actin stress fibers in fixed cells of various types. To address localization in living cells, we constructed GFP-CAP1 fusion proteins and found that fusion proteins lacking the actin-binding region localized like the wild type protein. We also performed microinjection studies with affinity-purified anti-CAP1 antibodies in Swiss 3T3 fibroblasts and found that the antibodies attenuated serum stimulation of stress fibers. Finally, CAP1 purified from platelets through a monoclonal antibody affinity purification step stimulated the formation of stress fiber-like filaments when it was microinjected into serum-starved Swiss 3T3 cells. Taken together, these data suggest that CAP1 promotes assembly of the actin cytoskeleton.

  15. Endocytic protein intersectin-l regulates actin assembly via Cdc42 and N-WASP.

    PubMed

    Hussain, N K; Jenna, S; Glogauer, M; Quinn, C C; Wasiak, S; Guipponi, M; Antonarakis, S E; Kay, B K; Stossel, T P; Lamarche-Vane, N; McPherson, P S

    2001-10-01

    Intersectin-s is a modular scaffolding protein regulating the formation of clathrin-coated vesicles. In addition to the Eps15 homology (EH) and Src homology 3 (SH3) domains of intersectin-s, the neuronal variant (intersectin-l) also has Dbl homology (DH), pleckstrin homology (PH) and C2 domains. We now show that intersectin-l functions through its DH domain as a guanine nucleotide exchange factor (GEF) for Cdc42. In cultured cells, expression of DH-domain-containing constructs cause actin rearrangements specific for Cdc42 activation. Moreover, in vivo studies reveal that stimulation of Cdc42 by intersectin-l accelerates actin assembly via N-WASP and the Arp2/3 complex. N-WASP binds directly to intersectin-l and upregulates its GEF activity, thereby generating GTP-bound Cdc42, a critical activator of N-WASP. These studies reveal a role for intersectin-l in a novel mechanism of N-WASP activation and in regulation of the actin cytoskeleton.

  16. Activator-inhibitor coupling between Rho signaling and actin assembly make the cell cortex an excitable medium

    PubMed Central

    Bement, William M.; Leda, Marcin; Moe, Alison M.; Kita, Angela M.; Larson, Matthew E.; Golding, Adriana E.; Pfeuti, Courtney; Su, Kuan-Chung; Miller, Ann L.; Goryachev, Andrew B.; von Dassow, George

    2016-01-01

    Animal cell cytokinesis results from patterned activation of the small GTPase Rho, which directs assembly of actomyosin in the equatorial cortex. Cytokinesis is restricted to a portion of the cell cycle following anaphase onset in which the cortex is responsive to signals from the spindle. We show that shortly after anaphase onset oocytes and embryonic cells of frogs and echinoderms exhibit cortical waves of Rho activity and F-actin polymerization. The waves are modulated by cyclin-dependent kinase 1 (Cdk1) activity and require the Rho GEF (guanine nucleotide exchange factor), Ect2. Surprisingly, during wave propagation, while Rho activity elicits F-actin assembly, F-actin subsequently inactivates Rho. Experimental and modeling results show that waves represent excitable dynamics of a reaction diffusion system with Rho as the activator and F-actin the inhibitor. We propose that cortical excitability explains fundamental features of cytokinesis including its cell cycle regulation. PMID:26479320

  17. Actin-based movement of Listeria monocytogenes: actin assembly results from the local maintenance of uncapped filament barbed ends at the bacterium surface

    PubMed Central

    1995-01-01

    The thermodynamic basis for actin-based motility of Listeria monocytogenes has been investigated using cytoplasmic extracts of Xenopus eggs, initially developed by Theriot et al. (Theriot, J. A., J. Rosenblatt, D. A. Portnoy, P. J. Goldschmidt-Clermont, and T. J. Mitchison. 1994. Cell. 76:505-517) as an in vitro cell-free system. A large proportion (75%) of actin was found unpolymerized in the extracts. The amount of unassembled actin (12 microM) is accounted for by the sequestering functions of T beta 4Xen (20 microM) and profilin (5 microM), the barbed ends being capped. Movement of Listeria was not abolished by depletion of over 99% of the endogenous profilin. The proline-rich sequences of ActA are unlikely to be the target of profilin. All data support the view that actin assembly at the rear of Listeria results from a local shift in steady state due to a factor, keeping filaments uncapped, bound to the surface of the bacterium, while barbed ends are capped in the bulk cytoplasm. Movement is controlled by the energetic difference (i.e., the difference in critical concentration) between the two ends of the filaments, hence a constant ATP supply and the presence of barbed end capped F-actin in the medium are required to buffer free G-actin at a high concentration. The role of membrane components is demonstrated by the facts that: (a) Listeria movement can be reconstituted in the resuspended pellets of high speed-centrifuged extracts that are enriched in membranes; (b) Actin-based motility of endogenous vesicles, exhibiting the same rocketing movement as Listeria, can be observed in the extracts. PMID:7615635

  18. Local Arp2/3-dependent actin assembly modulates applied traction force during apCAM adhesion site maturation

    PubMed Central

    Buck, Kenneth B.; Schaefer, Andrew W.; Schoonderwoert, Vincent T.; Creamer, Matthew S.; Dufresne, Eric R.; Forscher, Paul

    2017-01-01

    Homophilic binding of immunoglobulin superfamily molecules such as the Aplysia cell adhesion molecule (apCAM) leads to actin filament assembly near nascent adhesion sites. Such actin assembly can generate significant localized forces that have not been characterized in the larger context of axon growth and guidance. We used apCAM-coated bead substrates applied to the surface of neuronal growth cones to characterize the development of forces evoked by varying stiffness of mechanical restraint. Unrestrained bead propulsion matched or exceeded rates of retrograde network flow and was dependent on Arp2/3 complex activity. Analysis of growth cone forces applied to beads at low stiffness of restraint revealed switching between two states: frictional coupling to retrograde flow and Arp2/3-dependent propulsion. Stiff mechanical restraint led to formation of an extensive actin cup matching the geometric profile of the bead target and forward growth cone translocation; pharmacological inhibition of the Arp2/3 complex or Rac attenuated F-actin assembly near bead binding sites, decreased the efficacy of growth responses, and blocked accumulation of signaling molecules associated with nascent adhesions. These studies introduce a new model for regulation of traction force in which local actin assembly forces buffer nascent adhesion sites from the mechanical effects of retrograde flow. PMID:27852899

  19. Ac-loss measurement of a DyBCO-Roebel assembled coated conductor cable (RACC)

    NASA Astrophysics Data System (ADS)

    Schuller, S.; Goldacker, W.; Kling, A.; Krempasky, L.; Schmidt, C.

    2007-10-01

    Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature around 50-77 K, which is a crucial precondition for economical cooling costs. We prepared a short length of a Roebel bar cable made of industrial DyBCO coated conductor (Theva Company, Germany). Meander shaped tapes of 4 mm width with a twist pitch of 122 mm were cut from 10 mm wide CC tapes using a specially designed tool. Eleven of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac field were measured as a function of frequency and field amplitude in transverse and parallel field orientations. In addition, the coupling current time constant of the sample was directly measured.

  20. Myosin 1b promotes the formation of post-Golgi carriers by regulating actin assembly and membrane remodelling at the trans-Golgi network.

    PubMed

    Almeida, Claudia G; Yamada, Ayako; Tenza, Danièle; Louvard, Daniel; Raposo, Graça; Coudrier, Evelyne

    2011-06-12

    The function of organelles is intimately associated with rapid changes in membrane shape. By exerting force on membranes, the cytoskeleton and its associated motors have an important role in membrane remodelling. Actin and myosin 1 have been implicated in the invagination of the plasma membrane during endocytosis. However, whether myosin 1 and actin contribute to the membrane deformation that gives rise to the formation of post-Golgi carriers is unknown. Here we report that myosin 1b regulates the actin-dependent post-Golgi traffic of cargo, generates force that controls the assembly of F-actin foci and, together with the actin cytoskeleton, promotes the formation of tubules at the TGN. Our results provide evidence that actin and myosin 1 regulate organelle shape and uncover an important function for myosin 1b in the initiation of post-Golgi carrier formation by regulating actin assembly and remodelling TGN membranes.

  1. Treponema denticola Major Outer Sheath Protein Induces Actin Assembly at Free Barbed Ends by a PIP2-Dependent Uncapping Mechanism in Fibroblasts

    PubMed Central

    Visser, Michelle B.; Koh, Adeline; Glogauer, Michael; Ellen, Richard P.

    2011-01-01

    The major outer sheath protein (Msp) of Treponema denticola perturbs actin dynamics in fibroblasts by inducing actin reorganization, including subcortical actin filament assembly, leading to defective calcium flux, diminished integrin engagement of collagen, and retarded cell migration. Yet, its mechanisms of action are unknown. We challenged Rat-2 fibroblasts with enriched native Msp. Msp activated the small GTPases Rac1, RhoA and Ras, but not Cdc42, yet only Rac1 localized to areas of actin rearrangement. We used Rac1 dominant negative transfection and chemical inhibition of phosphatidylinositol-3 kinase (PI3K) to show that even though Rac1 activation was PI3K-dependent, neither was required for Msp-induced actin rearrangement. Actin free barbed end formation (FBE) by Msp was also PI3K-independent. Immunoblotting experiments showed that gelsolin and CapZ were released from actin filaments, whereas cofilin remained in an inactive state. Msp induced phosphatidylinositol (4,5)-bisphosphate (PIP2) formation through activation of a phosphoinositide 3-phosphatase and its recruitment to areas of actin assembly at the plasma membrane. Using a PIP2 binding peptide or lipid phosphatase inhibitor, PIP2 was shown to be required for Msp-mediated actin uncapping and FBE formation. Evidently, Msp induces actin assembly in fibroblasts by production and recruitment of PIP2 and release of the capping proteins CapZ and gelsolin from actin barbed ends. PMID:21901132

  2. Qualification Testing of Solid Rocket Booster Diagonal Strut Restraint Cable Assembly Part Number 10176-0031-102/103

    NASA Technical Reports Server (NTRS)

    Malone, T. W.

    2006-01-01

    This Technical Memorandum presents qualification test results for solid rocket booster diagonal strut restraint cable part number 101276-00313-102/103. During flight this assembly is exposed to a range of temperatures. MIL-W-83420 shows the breaking strength of the cable as 798 kg (1,760 lb) at room temperature but does not define cable strength at the maximum temperature to which the cable is exposed during the first 2 min of flight; 669 C (1,236 F). The cable, which can be built from different corrosion resistant steel alloys, may also vary in its chemical, physical, and mechanical properties at temperature. Negative margins of safety were produced by analysis of the cable at temperature using standard knockdown factors. However, MSFC-HDBK-5 allows the use of a less conservative safety factor of 1.4 and knockdown factors verified by testing. Test results allowed a calculated knockdown factor of 0.1892 to be determined for the restraint cables, which provides a minimum breaking strength of 151 kg (333 lb) at 677 C (1,250 F) when combined with the minimum breaking strength of 0.317-cm (0.125- or 1/8-in) diameter, type 1 composition rope.

  3. Balancing spatially regulated β-actin translation and dynamin-mediated endocytosis is required to assemble functional epithelial monolayers.

    PubMed

    Cruz, Lissette A; Vedula, Pavan; Gutierrez, Natasha; Shah, Neel; Rodriguez, Steven; Ayee, Brian; Davis, Justin; Rodriguez, Alexis J

    2015-12-01

    Regulating adherens junction complex assembly/disassembly is critical to maintaining epithelial homeostasis in healthy epithelial tissues. Consequently, adherens junction structure and function is often perturbed in clinically advanced tumors of epithelial origin. Some of the most studied factors driving adherens junction complex perturbation in epithelial cancers are transcriptional and epigenetic down-regulation of E-cadherin expression. However, numerous reports demonstrate that post-translational regulatory mechanisms such as endocytosis also regulate early phases of epithelial-mesenchymal transition and metastatic progression. In already assembled healthy epithelia, E-cadherin endocytosis recycles cadherin-catenin complexes to regulate the number of mature adherens junctions found at cell-cell contact sites. However, following de novo epithelial cell-cell contact, endocytosis negatively regulates adherens junction assembly by removing E-cadherin from the cell surface. By contrast, following de novo epithelial cell-cell contact, spatially localized β-actin translation drives cytoskeletal remodeling and consequently E-cadherin clustering at cell-cell contact sites and therefore positively regulates adherens junction assembly. In this report we demonstrate that dynamin-mediated endocytosis and β-actin translation-dependent cadherin-catenin complex anchoring oppose each other following epithelial cell-cell contact. Consequently, the final extent of adherens junction assembly depends on which of these processes is dominant following epithelial cell-cell contact. We expressed β-actin transcripts impaired in their ability to properly localize monomer synthesis (Δ3'UTR) in MDCK cells to perturb actin filament remodeling and anchoring, and demonstrate the resulting defect in adherens junction structure and function is rescued by inhibiting dynamin mediated endocytosis. Therefore, we demonstrate balancing spatially regulated β-actin translation and dynamin

  4. Balancing spatially regulated β-actin translation and dynamin mediated endocytosis is required to assemble functional epithelial monolayers

    PubMed Central

    Cruz, Lissette A.; Vedula, Pavan; Gutierrez, Natasha; Shah, Neel; Rodriguez, Steven; Ayee, Brian; Davis, Justin; Rodriguez, Alexis J.

    2015-01-01

    Regulating adherens junction complex assembly/disassembly is critical to maintaining epithelial homeostasis in healthy epithelial tissues. Consequently, adherens junction structure and function is often perturbed in clinically advanced tumors of epithelial origin. Some of the most studied factors driving adherens junction complex perturbation in epithelial cancers are transcriptional and epigenetic down-regulation of E-cadherin expression. However, numerous reports demonstrate that post-translational regulatory mechanisms such as endocytosis also regulate early phases of epithelial-mesenchymal transition and metastatic progression. In already assembled healthy epithelia, E-cadherin endocytosis recycles cadherin-catenin complexes to regulate the number of mature adherens junctions found at cell-cell contact sites. However, following de novo epithelial cell-cell contact, endocytosis negatively regulates adherens junction assembly by removing E-cadherin from the cell surface. By contrast, following de novo epithelial cell-cell contact, spatially localized β-actin translation drives cytoskeletal remodeling and consequently E-cadherin clustering at cell-cell contact sites and therefore positively regulates adherens junction assembly. In this report we demonstrate that dynamin-mediated endocytosis and β-actin translation dependent cadherin-catenin complex anchoring oppose each other following epithelial cell-cell contact. Consequently, the final extent of adherens junction assembly depends on which of these processes is dominant following epithelial cell-cell contact. We expressed β-actin transcripts impaired in their ability to properly localize monomer synthesis (Δ3′UTR) in MDCK cells to perturb actin filament remodeling and anchoring and demonstrate the resulting defect in adherens junction structure and function is rescued by inhibiting dynamin mediated endocytosis. Therefore, we demonstrate balancing spatially regulated β-actin translation and dynamin

  5. The ability of an attaching and effacing pathogen to trigger localized actin assembly contributes to virulence by promoting mucosal attachment

    PubMed Central

    Mallick, Emily M.; Garber, John J.; Vanguri, Vijay K.; Balasubramanian, Sowmya; Blood, Timothy; Clark, Stacie; Vingadassalom, Didier; Louissaint, Christopher; McCormick, Beth; Snapper, Scott B.; Leong, John M.

    2014-01-01

    Enterohemorrhagic Escherichia coli (EHEC) adheres to intestinal epithelial cells, then stimulates the actin nucleation promoting factor N-WASP to induce localized actin assembly resulting in an actin “pedestal”, the function of which is poorly understood. EHEC also produces Shiga toxin (Stx), which penetrates the intestinal epithelium to cause a life-threatening renal and systemic disease. To assess the role of pedestal formation in colonization and disease, we utilized the murine pathogen Citrobacter rodentium, which also forms actin pedestals, and the genetically engineered C. rodentium (Φstx2dact), which additionally triggers Stx-mediated systemic disease. We found that an intestine-specific N-WASP-deficient (iNWKO) mouse suffered dramatically less colonization and disease than N-WASP-proficient littermate controls when infected with either strain. In addition, upon infection of wild type mice, mutants of C. rodentium or C. rodentium (Φstx2dact) that are specifically defective in pedestal formation demonstrated a relatively modest defect in cecal colonization and fecal shedding, but a more severe defect in colonization of the colonic mucosa. The C. rodentium (Φstx2dact) pedestal-defective mutant did not cause renal disease and, after normalizing for fecal bacterial load, was associated with a 16-fold lower risk of lethality. These findings suggest that the ability of an attaching and effacing pathogen to promote localized actin assembly contributes to virulence by promoting mucosal attachment. PMID:24780054

  6. Characterization of the Twelve Channel 100/140 Micron Optical Fiber, Ribbon Cable and MTP Array Connector Assembly for Space Flight Environments

    NASA Technical Reports Server (NTRS)

    Ott, Melanie N.; Macmurphy, Shawn; Friedberg, Patricia; Day, John H. (Technical Monitor)

    2002-01-01

    Presented here is the second set of testing conducted by the Technology Validation Laboratory for Photonics at NASA Goddard Space Flight Center on the 12 optical fiber ribbon cable with MTP array connector for space flight environments. In the first set of testing the commercial 62.5/125 cable assembly was characterized using space flight parameters. The testing showed that the cable assembly would survive a typical space flight mission with the exception of a vacuum environment. Two enhancements were conducted to the existing technology to better suit the vacuum environment as well as the existing optoelectronics and increase the reliability of the assembly during vibration. The MTP assembly characterized here has a 100/140 optical commercial fiber and non outgassing connector and cable components. The characterization for this enhanced fiber optic cable assembly involved vibration, thermal and radiation testing. The data and results of this characterization study are presented which include optical in-situ testing.

  7. Drosophila Homologues of Adenomatous Polyposis Coli (APC) and the Formin Diaphanous Collaborate by a Conserved Mechanism to Stimulate Actin Filament Assembly*

    PubMed Central

    Jaiswal, Richa; Stepanik, Vince; Rankova, Aneliya; Molinar, Olivia; Goode, Bruce L.; McCartney, Brooke M.

    2013-01-01

    Adenomatous polyposis coli (APC) is a large multidomain protein that regulates the cytoskeleton. Recently, it was shown that vertebrate APC through its Basic domain directly collaborates with the formin mDia1 to stimulate actin filament assembly in the presence of nucleation barriers. However, it has been unclear whether these activities extend to homologues of APC and Dia in other organisms. Drosophila APC and Dia are each required to promote actin furrow formation in the syncytial embryo, suggesting a potential collaboration in actin assembly, but low sequence homology between the Basic domains of Drosophila and vertebrate APC has left their functional and mechanistic parallels uncertain. To address this question, we purified Drosophila APC1 and Dia and determined their individual and combined effects on actin assembly using both bulk fluorescence assays and total internal reflection fluorescence microscopy. Our data show that APC1, similar to its vertebrate homologue, bound to actin monomers and nucleated and bundled filaments. Further, Drosophila Dia nucleated actin assembly and protected growing filament barbed ends from capping protein. Drosophila APC1 and Dia directly interacted and collaborated to promote actin assembly in the combined presence of profilin and capping protein. Thus, despite limited sequence homology, Drosophila and vertebrate APCs exhibit highly related activities and mechanisms and directly collaborate with formins. These results suggest that APC-Dia interactions in actin assembly are conserved and may underlie important in vivo functions in a broad range of animal phyla. PMID:23558679

  8. Formin-like2 regulates Rho/ROCK pathway to promote actin assembly and cell invasion of colorectal cancer.

    PubMed

    Zeng, Yuanfeng; Xie, Huijun; Qiao, Yudan; Wang, Jianmei; Zhu, Xiling; He, Guoyang; Li, Yuling; Ren, Xiaoli; Wang, Feifei; Liang, Li; Ding, Yanqing

    2015-10-01

    Formin-like2 (FMNL2) is a member of the diaphanous-related formins family, which act as effectors and upstream modulators of Rho GTPases signaling and control the actin-dependent processes, such as cell motility or invasion. FMNL2 has been identified as promoting the motility and metastasis in colorectal carcinoma (CRC). However, whether FMNL2 regulates Rho signaling to promote cancer cell invasion remains unclear. In this study, we demonstrated an essential role for FMNL2 in the activations of Rho/ROCK pathway, SRF transcription or actin assembly, and subsequent CRC cell invasion. FMNL2 could activate Rho/ROCK pathway, and required ROCK to promote CRC cell invasion. Moreover, FMNL2 promoted the formation of filopodia and stress fiber, and activated the SRF transcription in a Rho-dependent manner. We also demonstrated that FMNL2 was necessary for LPA-induced invasion, RhoA/ROCK activation, actin assembly and SRF activation. FMNL2 was an essential component of LPA signal transduction toward RhoA by directly interacting with LARG. LARG silence inhibited RhoA/ROCK pathway and CRC cell invasion. Collectively, these data indicate that FMNL2, acting as upstream of RhoA by interacting with LARG, can promote actin assembly and CRC cell invasion through a Rho/ROCK-dependent mechanism.

  9. Mimicking the mechanical properties of the cell cortex by the self-assembly of an actin cortex in vesicles

    NASA Astrophysics Data System (ADS)

    Luo, Tianzhi; Srivastava, Vasudha; Ren, Yixin; Robinson, Douglas N.

    2014-04-01

    The composite of the actin cytoskeleton and plasma membrane plays important roles in many biological events. Here, we employed the emulsion method to synthesize artificial cells with biomimetic actin cortex in vesicles and characterized their mechanical properties. We demonstrated that the emulsion method provides the flexibility to adjust the lipid composition and protein concentrations in artificial cells to achieve the desired size distribution, internal microstructure, and mechanical properties. Moreover, comparison of the cortical elasticity measured for reconstituted artificial cells to that of real cells, including those manipulated using genetic depletion and pharmacological inhibition, strongly supports that actin cytoskeletal proteins are dominant over lipid molecules in cortical mechanics. Our study indicates that the assembly of biological systems in artificial cells with purified cellular components provides a powerful way to answer biological questions.

  10. Bacterial nucleators: actin' on actin

    PubMed Central

    Bugalhão, Joana N.; Mota, Luís Jaime; Franco, Irina S.

    2015-01-01

    The actin cytoskeleton is a key target of numerous microbial pathogens, including protozoa, fungi, bacteria and viruses. In particular, bacterial pathogens produce and deliver virulence effector proteins that hijack actin dynamics to enable bacterial invasion of host cells, allow movement within the host cytosol, facilitate intercellular spread or block phagocytosis. Many of these effector proteins directly or indirectly target the major eukaryotic actin nucleator, the Arp2/3 complex, by either mimicking nucleation promoting factors or activating upstream small GTPases. In contrast, this review is focused on a recently identified class of effector proteins from Gram-negative bacteria that function as direct actin nucleators. These effector proteins mimic functional activities of formins, WH2-nucleators and Ena/VASP assembly promoting factors demonstrating that bacteria have coopted the complete set of eukaryotic actin assembly pathways. Structural and functional analyses of these nucleators have revealed several motifs and/or mechanistic activities that are shared with eukaryotic actin nucleators. However, functional effects of these proteins during infection extend beyond plain actin polymerization leading to interference with other host cell functions such as vesicle trafficking, cell cycle progression and cell death. Therefore, their use as model systems could not only help in the understanding of the mechanistic details of actin polymerization but also provide novel insights into the connection between actin dynamics and other cellular pathways. PMID:26416078

  11. A complex of ZO-1 and the BAR-domain protein TOCA-1 regulates actin assembly at the tight junction

    PubMed Central

    Van Itallie, Christina M.; Tietgens, Amber Jean; Krystofiak, Evan; Kachar, Bechara; Anderson, James M.

    2015-01-01

    Assembly and sealing of the tight junction barrier are critically dependent on the perijunctional actin cytoskeleton, yet little is known about physical and functional links between barrier-forming proteins and actin. Here we identify a novel functional complex of the junction scaffolding protein ZO-1 and the F-BAR–domain protein TOCA-1. Using MDCK epithelial cells, we show that an alternative splice of TOCA-1 adds a PDZ-binding motif, which binds ZO-1, targeting TOCA-1 to barrier contacts. This isoform of TOCA-1 recruits the actin nucleation–promoting factor N-WASP to tight junctions. CRISPR-Cas9–mediated knockout of TOCA-1 results in increased paracellular flux and delayed recovery in a calcium switch assay. Knockout of TOCA-1 does not alter FRAP kinetics of GFP ZO-1 or occludin, but longer term (12 h) time-lapse microscopy reveals strikingly decreased tight junction membrane contact dynamics in knockout cells compared with controls. Reexpression of TOCA-1 with, but not without, the PDZ-binding motif rescues both altered flux and membrane contact dynamics. Ultrastructural analysis shows actin accumulation at the adherens junction in TOCA-1–knockout cells but unaltered freeze-fracture fibril morphology. Identification of the ZO-1/TOCA-1 complex provides novel insights into the underappreciated dependence of the barrier on the dynamic nature of cell-to-cell contacts and perijunctional actin. PMID:26063734

  12. Vimentin intermediate filaments control actin stress fiber assembly through GEF-H1 and RhoA

    PubMed Central

    Peränen, Johan; Schaible, Niccole; Cheng, Fang; Eriksson, John E.; Krishnan, Ramaswamy

    2017-01-01

    ABSTRACT The actin and intermediate filament cytoskeletons contribute to numerous cellular processes, including morphogenesis, cytokinesis and migration. These two cytoskeletal systems associate with each other, but the underlying mechanisms of this interaction are incompletely understood. Here, we show that inactivation of vimentin leads to increased actin stress fiber assembly and contractility, and consequent elevation of myosin light chain phosphorylation and stabilization of tropomyosin-4.2 (see Geeves et al., 2015). The vimentin-knockout phenotypes can be rescued by re-expression of wild-type vimentin, but not by the non-filamentous ‘unit length form’ vimentin, demonstrating that intact vimentin intermediate filaments are required to facilitate the effects on the actin cytoskeleton. Finally, we provide evidence that the effects of vimentin on stress fibers are mediated by activation of RhoA through its guanine nucleotide exchange factor GEF-H1 (also known as ARHGEF2). Vimentin depletion induces phosphorylation of the microtubule-associated GEF-H1 on Ser886, and thereby promotes RhoA activity and actin stress fiber assembly. Taken together, these data reveal a new mechanism by which intermediate filaments regulate contractile actomyosin bundles, and may explain why elevated vimentin expression levels correlate with increased migration and invasion of cancer cells. PMID:28096473

  13. Eukaryotic cell locomotion depends on the propagation of self-organized reaction-diffusion waves and oscillations of actin filament assembly.

    PubMed

    Vicker, Michael G

    2002-04-15

    Actin filament (F-actin) assembly kinetics determines the locomotion and shape of crawling eukaryotic cells, but the nature of these kinetics and their determining reactions are unclear. Live BHK21 fibroblasts, mouse melanoma cells, and Dictyostelium amoebae, locomoting on glass and expressing Green Fluorescent Protein-actin fusion proteins, were examined by confocal microscopy. The cells demonstrated three-dimensional bands of F-actin, which propagated throughout the cytoplasm at rates usually ranging between 2 and 5 microm/min in each cell type and produced lamellipodia or pseudopodia at the cell boundary. F-actin's dynamic behavior and supramolecular spatial patterns resembled in detail self-organized chemical waves in dissipative, physico-chemical systems. On this basis, the present observations provide the first evidence of self-organized, and probably autocatalytic, chemical reaction-diffusion waves of reversible actin filament assembly in vertebrate cells and a comprehensive record of wave and locomotory dynamics in vegetative-stage Dictyostelium cells. The intensity and frequency of F-actin wavefronts determine locomotory cell projections and the rotating oscillatory waves, which structure the cell surface. F-actin assembly waves thus provide a fundamental, deterministic, and nonlinear mechanism of cell locomotion and shape, which complements mechanisms based exclusively on stochastic molecular reaction kinetics.

  14. Cilia assembly: a role for F-actin in IFT recruitment.

    PubMed

    Quarmby, Lynne

    2014-09-08

    Ciliary growth rates are limited by the availability of precursors at the growing tip. A new paper reveals that the early rapid growth of nascent cilia is supported by F-actin-facilitated delivery of IFT proteins to basal bodies.

  15. Capping protein regulatory cycle driven by CARMIL and V-1 may promote actin network assembly at protruding edges.

    PubMed

    Fujiwara, Ikuko; Remmert, Kirsten; Piszczek, Grzegorz; Hammer, John A

    2014-05-13

    Although capping protein (CP) terminates actin filament elongation, it promotes Arp2/3-dependent actin network assembly and accelerates actin-based motility both in vitro and in vivo. In vitro, capping protein Arp2/3 myosin I linker (CARMIL) antagonizes CP by reducing its affinity for the barbed end and by uncapping CP-capped filaments, whereas the protein V-1/myotrophin sequesters CP in an inactive complex. Previous work showed that CARMIL can readily retrieve CP from the CP:V-1 complex, thereby converting inactive CP into a version with moderate affinity for the barbed end. Here we further clarify the mechanism of this exchange reaction, and we demonstrate that the CP:CARMIL complex created by complex exchange slows the rate of barbed-end elongation by rapidly associating with, and dissociating from, the barbed end. Importantly, the cellular concentrations of V-1 and CP determined here argue that most CP is sequestered by V-1 at steady state in vivo. Finally, we show that CARMIL is recruited to the plasma membrane and only at cell edges undergoing active protrusion. Assuming that CARMIL is active only at this location, our data argue that a large pool of freely diffusing, inactive CP (CP:V-1) feeds, via CARMIL-driven complex exchange, the formation of weak-capping complexes (CP:CARMIL) at the plasma membrane of protruding edges. In vivo, therefore, CARMIL should promote Arp2/3-dependent actin network assembly at the leading edge by promoting barbed-end capping there.

  16. Capping protein regulatory cycle driven by CARMIL and V-1 may promote actin network assembly at protruding edges

    PubMed Central

    Fujiwara, Ikuko; Remmert, Kirsten; Piszczek, Grzegorz; Hammer, John A.

    2014-01-01

    Although capping protein (CP) terminates actin filament elongation, it promotes Arp2/3-dependent actin network assembly and accelerates actin-based motility both in vitro and in vivo. In vitro, capping protein Arp2/3 myosin I linker (CARMIL) antagonizes CP by reducing its affinity for the barbed end and by uncapping CP-capped filaments, whereas the protein V-1/myotrophin sequesters CP in an inactive complex. Previous work showed that CARMIL can readily retrieve CP from the CP:V-1 complex, thereby converting inactive CP into a version with moderate affinity for the barbed end. Here we further clarify the mechanism of this exchange reaction, and we demonstrate that the CP:CARMIL complex created by complex exchange slows the rate of barbed-end elongation by rapidly associating with, and dissociating from, the barbed end. Importantly, the cellular concentrations of V-1 and CP determined here argue that most CP is sequestered by V-1 at steady state in vivo. Finally, we show that CARMIL is recruited to the plasma membrane and only at cell edges undergoing active protrusion. Assuming that CARMIL is active only at this location, our data argue that a large pool of freely diffusing, inactive CP (CP:V-1) feeds, via CARMIL-driven complex exchange, the formation of weak-capping complexes (CP:CARMIL) at the plasma membrane of protruding edges. In vivo, therefore, CARMIL should promote Arp2/3-dependent actin network assembly at the leading edge by promoting barbed-end capping there. PMID:24778263

  17. F-actin assembly in Dictyostelium cell locomotion and shape oscillations propagates as a self-organized reaction-diffusion wave.

    PubMed

    Vicker, Michael G

    2002-01-02

    The crawling locomotion and shape of eukaryotic cells have been associated with the stochastic molecular dynamics of actin and its protein regulators, chiefly Arp2/3 and Rho family GTPases, in making a cytoskeleton meshwork within cell extensions. However, the cell's actin-dependent oscillatory shape and extension dynamics may also yield insights into locomotory mechanisms. Confocal observations of live Dictyostelium cells, expressing a green fluorescent protein-actin fusion protein, demonstrate oscillating supramolecular patterns of filamentous actin throughout the cell, which generate pseudopodia at the cell edge. The distinctively dissipative spatio-temporal behavior of these structures provides strong evidence that reversible actin filament assembly propagates as a self-organized, chemical reaction-diffusion wave.

  18. How Leiomodin and Tropomodulin use a common fold for different actin assembly functions

    PubMed Central

    Boczkowska, Malgorzata; Rebowski, Grzegorz; Kremneva, Elena; Lappalainen, Pekka; Dominguez, Roberto

    2015-01-01

    How proteins sharing a common fold have evolved different functions is a fundamental question in biology. Tropomodulins (Tmods) are prototypical actin filament pointed-end-capping proteins, whereas their homologues, Leiomodins (Lmods), are powerful filament nucleators. We show that Tmods and Lmods do not compete biochemically, and display similar but distinct localization in sarcomeres. Changes along the polypeptide chains of Tmods and Lmods exquisitely adapt their functions for capping versus nucleation. Tmods have alternating tropomyosin (TM)- and actin-binding sites (TMBS1, ABS1, TMBS2 and ABS2). Lmods additionally contain a C-terminal extension featuring an actin-binding WH2 domain. Unexpectedly, the different activities of Tmods and Lmods do not arise from the Lmod-specific extension. Instead, nucleation by Lmods depends on two major adaptations—the loss of pointed-end-capping elements present in Tmods and the specialization of the highly conserved ABS2 for recruitment of two or more actin subunits. The WH2 domain plays only an auxiliary role in nucleation. PMID:26370058

  19. Synaptopodin-2 induces assembly of peripheral actin bundles and immature focal adhesions to promote lamellipodia formation and prostate cancer cell migration

    PubMed Central

    Kai, FuiBoon; Fawcett, James P.; Duncan, Roy

    2015-01-01

    Synaptopodin-2 (Synpo2), an actin-binding protein and invasive cancer biomarker, induces formation of complex stress fiber networks in the cell body and promotes PC3 prostate cancer cell migration in response to serum stimulation. The role of these actin networks in enhanced cancer cell migration is unknown. Using time-course analysis and live cell imaging of mock- and Synpo2-transduced PC3 cells, we now show that Synpo2 induces assembly of actin fibers near the cell periphery and Arp2/3-dependent lamellipodia formation. Lamellipodia formed in a non-directional manner or repeatedly changed direction, explaining the enhanced chemokinetic activity of PC3 cells in response to serum stimulation. Myosin contraction promotes retrograde flow of the Synpo2-associated actin filaments at the leading edge and their merger with actin networks in the cell body. Enhanced PC3 cell migration correlates with Synpo2-induced formation of lamellipodia and immature focal adhesions (FAs), but is not dependent on myosin contraction or FA maturation. The previously reported correlation between Synpo2-induced stress fiber assembly and enhanced PC3 cell migration therefore reflects the role of Synpo2 as a newly identified regulator of actin bundle formation and nascent FA assembly near the leading cell edge. PMID:25883213

  20. In vitro assembly of the bacterial actin protein MamK from ' Candidatus Magnetobacterium casensis' in the phylum Nitrospirae.

    PubMed

    Deng, Aihua; Lin, Wei; Shi, Nana; Wu, Jie; Sun, Zhaopeng; Sun, Qinyun; Bai, Hua; Pan, Yongxin; Wen, Tingyi

    2016-04-01

    Magnetotactic bacteria (MTB), a group of phylogenetically diverse organisms that use their unique intracellular magnetosome organelles to swim along the Earth's magnetic field, play important roles in the biogeochemical cycles of iron and sulfur. Previous studies have revealed that the bacterial actin protein MamK plays essential roles in the linear arrangement of magnetosomes in MTB cells belonging to the Proteobacteria phylum. However, the molecular mechanisms of multiple-magnetosome-chain arrangements in MTB remain largely unknown. Here, we report that the MamK filaments from the uncultivated 'Candidatus Magnetobacterium casensis' (Mcas) within the phylum Nitrospirae polymerized in the presence of ATP alone and were stable without obvious ATP hydrolysis-mediated disassembly. MamK in Mcas can convert NTP to NDP and NDP to NMP, showing the highest preference to ATP. Unlike its Magnetospirillum counterparts, which form a single magnetosome chain, or other bacterial actins such as MreB and ParM, the polymerized MamK from Mcas is independent of metal ions and nucleotides except for ATP, and is assembled into well-ordered filamentous bundles consisted of multiple filaments. Our results suggest a dynamically stable assembly of MamK from the uncultivated Nitrospirae MTB that synthesizes multiple magnetosome chains per cell. These findings further improve the current knowledge of biomineralization and organelle biogenesis in prokaryotic systems.

  1. Genetically encoded photoswitching of actin assembly through the Cdc42-WASP-Arp2/3 complex pathway

    PubMed Central

    Leung, Daisy W.; Otomo, Chinatsu; Chory, Joanne; Rosen, Michael K.

    2008-01-01

    General methods to engineer genetically encoded, reversible, light-mediated control over protein function would be useful in many areas of biomedical research and technology. We describe a system that yields such photo-control over actin assembly. We fused the Rho family GTPase Cdc42 in its GDP-bound form to the photosensory domain of phytochrome B (PhyB) and fused the Cdc42 effector, the Wiskott-Aldrich Syndrome Protein (WASP), to the light-dependent PhyB-binding domain of phytochrome interacting factor 3 (Pif3). Upon red light illumination, the fusion proteins bind each other, activating WASP, and consequently stimulating actin assembly by the WASP target, the Arp2/3 complex. Binding and WASP activation are reversed by far-red illumination. Our approach, in which the biochemical specificity of the nucleotide switch in Cdc42 is overridden by the light-dependent PhyB-Pif3 interaction, should be generally applicable to other GTPase-effector pairs. PMID:18728185

  2. Kv3.3 Channels Bind Hax-1 and Arp2/3 to Assemble a Stable Local Actin Network that Regulates Channel Gating.

    PubMed

    Zhang, Yalan; Zhang, Xiao-Feng; Fleming, Matthew R; Amiri, Anahita; El-Hassar, Lynda; Surguchev, Alexei A; Hyland, Callen; Jenkins, David P; Desai, Rooma; Brown, Maile R; Gazula, Valeswara-Rao; Waters, Michael F; Large, Charles H; Horvath, Tamas L; Navaratnam, Dhasakumar; Vaccarino, Flora M; Forscher, Paul; Kaczmarek, Leonard K

    2016-04-07

    Mutations in the Kv3.3 potassium channel (KCNC3) cause cerebellar neurodegeneration and impair auditory processing. The cytoplasmic C terminus of Kv3.3 contains a proline-rich domain conserved in proteins that activate actin nucleation through Arp2/3. We found that Kv3.3 recruits Arp2/3 to the plasma membrane, resulting in formation of a relatively stable cortical actin filament network resistant to cytochalasin D that inhibits fast barbed end actin assembly. These Kv3.3-associated actin structures are required to prevent very rapid N-type channel inactivation during short depolarizations of the plasma membrane. The effects of Kv3.3 on the actin cytoskeleton are mediated by the binding of the cytoplasmic C terminus of Kv3.3 to Hax-1, an anti-apoptotic protein that regulates actin nucleation through Arp2/3. A human Kv3.3 mutation within a conserved proline-rich domain produces channels that bind Hax-1 but are impaired in recruiting Arp2/3 to the plasma membrane, resulting in growth cones with deficient actin veils in stem cell-derived neurons.

  3. Correction coil cable

    DOEpatents

    Wang, S.T.

    1994-11-01

    A wire cable assembly adapted for the winding of electrical coils is taught. A primary intended use is for use in particle tube assemblies for the Superconducting Super Collider. The correction coil cables have wires collected in wire array with a center rib sandwiched therebetween to form a core assembly. The core assembly is surrounded by an assembly housing having an inner spiral wrap and a counter wound outer spiral wrap. An alternate embodiment of the invention is rolled into a keystoned shape to improve radial alignment of the correction coil cable on a particle tube in a particle tube assembly. 7 figs.

  4. Myosin II filament assemblies in the active lamella of fibroblasts: their morphogenesis and role in the formation of actin filament bundles

    PubMed Central

    1995-01-01

    The morphogenesis of myosin II structures in active lamella undergoing net protrusion was analyzed by correlative fluorescence and electron microscopy. In rat embryo fibroblasts (REF 52) microinjected with tetramethylrhodamine-myosin II, nascent myosin spots formed close to the active edge during periods of retraction and then elongated into wavy ribbons of uniform width. The spots and ribbons initially behaved as distinct structural entities but subsequently aligned with each other in a sarcomeric-like pattern. Electron microscopy established that the spots and ribbons consisted of bipolar minifilaments associated with each other at their head-containing ends and arranged in a single row in an "open" zig-zag conformation or as a "closed" parallel stack. Ribbons also contacted each other in a nonsarcomeric, network-like arrangement as described previously (Verkhovsky and Borisy, 1993. J. Cell Biol. 123:637-652). Myosin ribbons were particularly pronounced in REF 52 cells, but small ribbons and networks were found also in a range of other mammalian cells. At the edge of the cell, individual spots and open ribbons were associated with relatively disordered actin filaments. Further from the edge, myosin filament alignment increased in parallel with the development of actin bundles. In actin bundles, the actin cross-linking protein, alpha-actinin, was excluded from sites of myosin localization but concentrated in paired sites flanking each myosin ribbon, suggesting that myosin filament association may initiate a pathway for the formation of actin filament bundles. We propose that zig-zag assemblies of myosin II filaments induce the formation of actin bundles by pulling on an actin filament network and that co-alignment of actin and myosin filaments proceeds via folding of myosin II filament assemblies in an accordion-like fashion. PMID:7490299

  5. N- and E-cadherins in Xenopus are specifically required in the neural and non-neural ectoderm, respectively, for F-actin assembly and morphogenetic movements

    PubMed Central

    Nandadasa, Sumeda; Tao, Qinghua; Menon, Nikhil R.; Heasman, Janet; Wylie, Christopher

    2009-01-01

    Summary Transmembrane cadherins are calcium-dependent intercellular adhesion molecules. Recently, they have also been shown to be sites of actin assembly during adhesive contact formation. However, the roles of actin assembly on transmembrane cadherins during development are not fully understood. We show here, using the developing ectoderm of the Xenopus embryo as a model, that F-actin assembly is a primary function of both N-cadherin in the neural ectoderm and E-cadherin in the non-neural (epidermal) ectoderm, and that each cadherin is essential for the characteristic morphogenetic movements of these two tissues. However, depletion of N-cadherin and E-cadherin did not cause dissociation in these tissues at the neurula stage, probably owing to the expression of C-cadherin in each tissue. Depletion of each of these cadherins is not rescued by the other, nor by the expression of C-cadherin, which is expressed in both tissues. One possible reason for this is that each cadherin is expressed in a different domain of the cell membrane. These data indicate the combinatorial nature of cadherin function, the fact that N- and E-cadherin play primary roles in F-actin assembly in addition to roles in cell adhesion, and that this function is specific to individual cadherins. They also show how cell adhesion and motility can be combined in morphogenetic tissue movements that generate the form and shape of the embryonic organs. PMID:19279134

  6. Cable and line inspection mechanism

    NASA Technical Reports Server (NTRS)

    Ross, Terence J. (Inventor)

    2003-01-01

    An automated cable and line inspection mechanism visually scans the entire surface of a cable as the mechanism travels along the cable=s length. The mechanism includes a drive system, a video camera, a mirror assembly for providing the camera with a 360 degree view of the cable, and a laser micrometer for measuring the cable=s diameter. The drive system includes an electric motor and a plurality of drive wheels and tension wheels for engaging the cable or line to be inspected, and driving the mechanism along the cable. The mirror assembly includes mirrors that are positioned to project multiple images of the cable on the camera lens, each of which is of a different portion of the cable. A data transceiver and a video transmitter are preferably employed for transmission of video images, data and commands between the mechanism and a remote control station.

  7. Extracellular Assembly of the Elastin Cable Line Element in the Developing Lung.

    PubMed

    Valenzuela, Cristian D; Wagner, Willi L; Bennett, Robert D; Ysasi, Alexandra B; Belle, Janeil; Molter, Karin; Straub, Beate K; Wang, Dong; Chen, Zi; Ackermann, Maximilian; Tsuda, Akira; Mentzer, Steven J

    2017-04-05

    In the normal lung, a dominant structural element is an elastic "line element" that originates in the central bronchi and inserts into the distal airspaces. Despite its structural importance, the process that leads to development of the cable line element is unknown. To investigate the morphologic events contributing to its development, we used optical clearing methods to examine the postnatal rat lung. An unexpected finding was numerous spheres, with a median diameter of 1-2µm, within the primary septa of the rat lung. The spheres demonstrated green autofluorescence, selective fluorescent eosin staining, reactivity with carboxyfluorescein succinimidyl ester, and specific labeling with anti-tropoelastin monoclonal antibody-findings consistent with tropoelastin. The sphere number peaked on rat postnatal day 4 (P4) and were rare by P14. The disappearance of the spheres was coincident with the development of the cable line element in the rat lung. Transmission electron microscopy demonstrated no consistent association between parenchymal cells and sphere alignment. In contrast, the alignment of tropoelastin spheres appeared to be the direct result of interactions of scaffold proteins including collagen fibers and fibrillin microfibrils. We conclude that the spatial organization of the cable line element appears to be independent of tropoelastin deposition, but dependent upon crosslinking to scaffold proteins within the primary septa. This article is protected by copyright. All rights reserved.

  8. A Role for Myosin-I in Actin Assembly through Interactions with Vrp1p, Bee1p, and the Arp2/3 Complex

    PubMed Central

    Evangelista, Marie; Klebl, Bert M.; Tong, Amy H.Y.; Webb, Bradley A.; Leeuw, Thomas; Leberer, Ekkehard; Whiteway, Malcolm; Thomas, David Y.; Boone, Charles

    2000-01-01

    Type I myosins are highly conserved actin-based molecular motors that localize to the actin-rich cortex and participate in motility functions such as endocytosis, polarized morphogenesis, and cell migration. The COOH-terminal tail of yeast myosin-I proteins, Myo3p and Myo5p, contains an Src homology domain 3 (SH3) followed by an acidic domain. The myosin-I SH3 domain interacted with both Bee1p and Vrp1p, yeast homologues of human WASP and WIP, adapter proteins that link actin assembly and signaling molecules. The myosin-I acidic domain interacted with Arp2/3 complex subunits, Arc40p and Arc19p, and showed both sequence similarity and genetic redundancy with the COOH-terminal acidic domain of Bee1p (Las17p), which controls Arp2/3-mediated actin nucleation. These findings suggest that myosin-I proteins may participate in a diverse set of motility functions through a role in actin assembly. PMID:10648568

  9. Signalling to actin assembly via the WASP (Wiskott-Aldrich syndrome protein)-family proteins and the Arp2/3 complex.

    PubMed Central

    Millard, Thomas H; Sharp, Stewart J; Machesky, Laura M

    2004-01-01

    The assembly of a branched network of actin filaments provides the mechanical propulsion that drives a range of dynamic cellular processes, including cell motility. The Arp2/3 complex is a crucial component of such filament networks. Arp2/3 nucleates new actin filaments while bound to existing filaments, thus creating a branched network. In recent years, a number of proteins that activate the filament nucleation activity of Arp2/3 have been identified, most notably the WASP (Wiskott-Aldrich syndrome protein) family. WASP-family proteins activate the Arp2/3 complex, and consequently stimulate actin assembly, in response to extracellular signals. Structural studies have provided a significant refinement in our understanding of the molecular detail of how the Arp2/3 complex nucleates actin filaments. There has also been much progress towards an understanding of the complicated signalling processes that regulate WASP-family proteins. In addition, the use of gene disruption in a number of organisms has led to new insights into the specific functions of individual WASP-family members. The present review will discuss the Arp2/3 complex and its regulators, in particular the WASP-family proteins. Emphasis will be placed on recent developments in the field that have furthered our understanding of actin dynamics and cell motility. PMID:15040784

  10. Vinculin Interacts with the Chlamydia Effector TarP Via a Tripartite Vinculin Binding Domain to Mediate Actin Recruitment and Assembly at the Plasma Membrane.

    PubMed

    Thwaites, Tristan R; Pedrosa, Antonio T; Peacock, Thomas P; Carabeo, Rey A

    2015-01-01

    The mammalian protein vinculin is often a target of bacterial pathogens to subvert locally host cell actin dynamics. In Chlamydia infection, vinculin has been implicated in RNA interference screens, but the molecular basis for vinculin requirement has not been characterized. In this report, we show that vinculin was involved in the actin recruitment and F-actin assembly at the plasma membrane to facilitate invasion. Vinculin was recruited to the plasma membrane via its interaction with a specific tripartite motif within TarP that resembles the vinculin-binding domain (VBD) found in the Shigella invasion factor IpaA. The TarP-mediated plasma membrane recruitment of vinculin resulted in the localized recruitment of actin. In vitro pulldown assays for protein-protein interaction and imaging-based evaluation of recruitment to the plasma membrane demonstrated the essential role of the vinculin-binding site 1 (VBS1), and the dispensability of VBS2 and VBS3. As further support for the functionality of VBD-vinculin interaction, VBD-mediated actin recruitment required vinculin. Interestingly, while both vinculin and the focal adhesion kinase (FAK) colocalized at the sites of adhesion, the recruitment of one was independent of the other; and the actin recruitment function of the VBD/vinculin signaling axis was independent of the LD/FAK pathway.

  11. Structural Analysis of Human Cofilin 2/Filamentous Actin Assemblies: Atomic-Resolution Insights from Magic Angle Spinning NMR Spectroscopy

    PubMed Central

    Yehl, Jenna; Kudryashova, Elena; Reisler, Emil; Kudryashov, Dmitri; Polenova, Tatyana

    2017-01-01

    Cellular actin dynamics is an essential element of numerous cellular processes, such as cell motility, cell division and endocytosis. Actin’s involvement in these processes is mediated by many actin-binding proteins, among which the cofilin family plays unique and essential role in accelerating actin treadmilling in filamentous actin (F-actin) in a nucleotide-state dependent manner. Cofilin preferentially interacts with older filaments by recognizing time-dependent changes in F-actin structure associated with the hydrolysis of ATP and release of inorganic phosphate (Pi) from the nucleotide cleft of actin. The structure of cofilin on F-actin and the details of the intermolecular interface remain poorly understood at atomic resolution. Here we report atomic-level characterization by magic angle spinning (MAS) NMR of the muscle isoform of human cofilin 2 (CFL2) bound to F-actin. We demonstrate that resonance assignments for the majority of atoms are readily accomplished and we derive the intermolecular interface between CFL2 and F-actin. The MAS NMR approach reported here establishes the foundation for atomic-resolution characterization of a broad range of actin-associated proteins bound to F-actin. PMID:28303963

  12. The Human Arp2/3 Complex Is Composed of Evolutionarily Conserved Subunits and Is Localized to Cellular Regions of Dynamic Actin Filament Assembly

    PubMed Central

    Welch, Matthew D.; DePace, Angela H.; Verma, Suzie; Iwamatsu, Akihiro; Mitchison, Timothy J.

    1997-01-01

    The Arp2/3 protein complex has been implicated in the control of actin polymerization in cells. The human complex consists of seven subunits which include the actin related proteins Arp2 and Arp3, and five others referred to as p41-Arc, p34-Arc, p21-Arc, p20-Arc, and p16-Arc (Arp complex). We have determined the predicted amino acid sequence of all seven subunits. Each has homologues in diverse eukaryotes, implying that the structure and function of the complex has been conserved through evolution. Human Arp2 and Arp3 are very similar to family members from other species. p41-Arc is a new member of the Sop2 family of WD (tryptophan and aspartate) repeat–containing proteins and may be posttranslationally modified, suggesting that it may be involved in regulating the activity and/or localization of the complex. p34-Arc, p21-Arc, p20-Arc, and p16-Arc define novel protein families. We sought to evaluate the function of the Arp2/3 complex in cells by determining its intracellular distribution. Arp3, p34-Arc, and p21-Arc were localized to the lamellipodia of stationary and locomoting fibroblasts, as well to Listeria monocytogenes assembled actin tails. They were not detected in cellular bundles of actin filaments. Taken together with the ability of the Arp2/3 complex to induce actin polymerization, these observations suggest that the complex promotes actin assembly in lamellipodia and may participate in lamellipodial protrusion. PMID:9230079

  13. The human Arp2/3 complex is composed of evolutionarily conserved subunits and is localized to cellular regions of dynamic actin filament assembly.

    PubMed

    Welch, M D; DePace, A H; Verma, S; Iwamatsu, A; Mitchison, T J

    1997-07-28

    The Arp2/3 protein complex has been implicated in the control of actin polymerization in cells. The human complex consists of seven subunits which include the actin related proteins Arp2 and Arp3, and five others referred to as p41-Arc, p34-Arc, p21-Arc, p20-Arc, and p16-Arc (p omplex). We have determined the predicted amino acid sequence of all seven subunits. Each has homologues in diverse eukaryotes, implying that the structure and function of the complex has been conserved through evolution. Human Arp2 and Arp3 are very similar to family members from other species. p41-Arc is a new member of the Sop2 family of WD (tryptophan and aspartate) repeat-containing proteins and may be posttranslationally modified, suggesting that it may be involved in regulating the activity and/or localization of the complex. p34-Arc, p21-Arc, p20-Arc, and p16-Arc define novel protein families. We sought to evaluate the function of the Arp2/3 complex in cells by determining its intracellular distribution. Arp3, p34-Arc, and p21-Arc were localized to the lamellipodia of stationary and locomoting fibroblasts, as well to Listeria monocytogenes assembled actin tails. They were not detected in cellular bundles of actin filaments. Taken together with the ability of the Arp2/3 complex to induce actin polymerization, these observations suggest that the complex promotes actin assembly in lamellipodia and may participate in lamellipodial protrusion.

  14. Myosin flares and actin leptomeres as myofibril assembly/disassembly intermediates in sonic muscle fibers.

    PubMed

    Nahirney, Patrick C; Fischman, Donald A; Wang, Kuan

    2006-04-01

    The sonic muscle of type 1 male midshipman fish produces loud and enduring mating calls. Each sonic muscle fiber contains a tubular contractile apparatus with radially arranged myofibrillar plates encased in a desmin-rich cytoskeleton that is anchored to broad Z bands (approximately 1.2 micro m wide). Immunomicroscopy has revealed patches of myosin-rich "flares" emanating from the contractile tubes into the peripheral sarcoplasm along the length of the fibers. These flares contain swirls of thick filaments devoid of associated thin filaments. In other regions of the sarcoplasm at the inner surface of the sarcolemma and near Z bands, abundant ladder-like leptomeres occur with rungs every 160 nm. Leptomeres consist of dense arrays of filaments (approximately 4 nm) with a structure that resembles myofibrillar Z band structure. We propose that flares and leptomeres are distinct filamentous arrays representing site-specific processing of myofibrillar components during the assembly and disassembly of the sarcomere. Recent reports that myosin assembles into filamentous aggregates before incorporating into the A band in the skeletal muscles of vertebrates and Caenorhabditis elegans suggest that sonic fibers utilize a similar pathway. Thus, sonic muscle fibers, with their tubular design and abundant sarcoplasmic space, may provide an attractive muscle model to identify myofibrillar intermediates by structural and molecular techniques.

  15. The Yeast V159N Actin Mutant Reveals Roles for Actin Dynamics In Vivo

    PubMed Central

    Belmont, Lisa D.; Drubin, David G.

    1998-01-01

    Actin with a Val 159 to Asn mutation (V159N) forms actin filaments that depolymerize slowly because of a failure to undergo a conformational change after inorganic phosphate release. Here we demonstrate that expression of this actin results in reduced actin dynamics in vivo, and we make use of this property to study the roles of rapid actin filament turnover. Yeast strains expressing the V159N mutant (act1-159) as their only source of actin have larger cortical actin patches and more actin cables than wild-type yeast. Rapid actin dynamics are not essential for cortical actin patch motility or establishment of cell polarity. However, fluid phase endocytosis is defective in act1-159 strains. act1-159 is synthetically lethal with cofilin and profilin mutants, supporting the conclusion that mutations in all of these genes impair the polymerization/ depolymerization cycle. In contrast, act1-159 partially suppresses the temperature sensitivity of a tropomyosin mutant, and the loss of cytoplasmic cables seen in fimbrin, Mdm20p, and tropomyosin null mutants, suggesting filament stabilizing functions for these actin-binding proteins. Analysis of the cables in these double-mutant cells supports a role for fimbrin in organizing cytoplasmic cables and for Mdm20p and tropomyosin in excluding cofilin from the cables. PMID:9732289

  16. The transcriptional repressor Sum1p counteracts Sir2p in regulation of the actin cytoskeleton, mitochondrial quality control and replicative lifespan in Saccharomyces cerevisiae

    PubMed Central

    Higuchi-Sanabria, Ryo; Vevea, Jason D.; Charalel, Joseph K.; Sapar, Maria L.; Pon, Liza A.

    2016-01-01

    Increasing the stability or dynamics of the actin cytoskeleton can extend lifespan in C. elegans and S. cerevisiae. Actin cables of budding yeast, bundles of actin filaments that mediate cargo transport, affect lifespan control through effects on mitochondrial quality control. Sir2p, the founding member of the Sirtuin family of lifespan regulators, also affects actin cable dynamics, assembly, and function in mitochondrial quality control. Here, we obtained evidence for novel interactions between Sir2p and Sum1p, a transcriptional repressor that was originally identified through mutations that genetically suppress sir2∆ phenotypes unrelated to lifespan. We find that deletion of SUM1 in wild-type cells results in increased mitochondrial function and actin cable abundance. Furthermore, deletion of SUM1 suppresses defects in actin cables and mitochondria of sir2∆ yeast, and extends the replicative lifespan and cellular health span of sir2∆ cells. Thus, Sum1p suppresses Sir2p function in control of specific aging determinants and lifespan in budding yeast. PMID:28357337

  17. Fission Yeast Myosin-I, Myo1p, Stimulates Actin Assembly by Arp2/3 Complex and Shares Functions with Wasp

    PubMed Central

    Lee, Wei-Lih; Bezanilla, Magdalena; Pollard, Thomas D.

    2000-01-01

    Fission yeast myo1+ encodes a myosin-I with all three tail homology domains (TH1, 2, 3) found in typical long-tailed myosin-Is. Myo1p tail also contains a COOH-terminal acidic region similar to the A-domain of WASp/Scar proteins and other fungal myosin-Is. Our analysis shows that Myo1p and Wsp1p, the fission yeast WASp-like protein, share functions and cooperate in controlling actin assembly. First, Myo1p localizes to cortical patches enriched at tips of growing cells and at sites of cell division. Myo1p patches partially colocalize with actin patches and are dependent on an intact actin cytoskeleton. Second, although deletion of myo1+ is not lethal, Δmyo1 cells have actin cytoskeletal defects, including loss of polarized cell growth, delocalized actin patches, and mating defects. Third, additional disruption of wsp1+ is synthetically lethal, suggesting that these genes may share functions. In mapping the domains of Myo1p tail that share function with Wsp1p, we discovered that a Myo1p construct with just the head and TH1 domains is sufficient for cortical localization and to rescue all Δmyo1 defects. However, it fails to rescue the Δmyo1 Δwsp1 lethality. Additional tail domains, TH2 and TH3, are required to complement the double mutant. Fourth, we show that a recombinant Myo1p tail binds to Arp2/3 complex and activates its actin nucleation activity. PMID:11076964

  18. Amplification of actin polymerization forces

    PubMed Central

    Dmitrieff, Serge; Nédélec, François

    2016-01-01

    The actin cytoskeleton drives many essential processes in vivo, using molecular motors and actin assembly as force generators. We discuss here the propagation of forces caused by actin polymerization, highlighting simple configurations where the force developed by the network can exceed the sum of the polymerization forces from all filaments. PMID:27002174

  19. Amplification of actin polymerization forces.

    PubMed

    Dmitrieff, Serge; Nédélec, François

    2016-03-28

    The actin cytoskeleton drives many essential processes in vivo, using molecular motors and actin assembly as force generators. We discuss here the propagation of forces caused by actin polymerization, highlighting simple configurations where the force developed by the network can exceed the sum of the polymerization forces from all filaments.

  20. A new F-actin structure in fungi: actin ring formation around the cell nucleus of Cryptococcus neoformans.

    PubMed

    Kopecká, Marie; Kawamoto, Susumu; Yamaguchi, Masashi

    2013-04-01

    The F-actin cytoskeleton of Cryptococcus neoformans is known to comprise actin cables, cortical patches and cytokinetic ring. Here, we describe a new F-actin structure in fungi, a perinuclear F-actin collar ring around the cell nucleus, by fluorescent microscopic imaging of rhodamine phalloidin-stained F-actin. Perinuclear F-actin rings form in Cryptococcus neoformans treated with the microtubule inhibitor Nocodazole or with the drug solvent dimethyl sulfoxide (DMSO) or grown in yeast extract peptone dextrose (YEPD) medium, but they are absent in cells treated with Latrunculin A. Perinuclear F-actin rings may function as 'funicular cabin' for the cell nucleus, and actin cables as intracellular 'funicular' suspending nucleus in the central position in the cell and moving nucleus along the polarity axis along actin cables.

  1. Power superconducting power transmission cable

    DOEpatents

    Ashworth, Stephen P.

    2003-06-10

    The present invention is for a compact superconducting power transmission cable operating at distribution level voltages. The superconducting cable is a conductor with a number of tapes assembled into a subconductor. These conductors are then mounted co-planarly in an elongated dielectric to produce a 3-phase cable. The arrangement increases the magnetic field parallel to the tapes thereby reducing ac losses.

  2. Power superconducting power transmission cable

    DOEpatents

    Ashworth, Stephen P.

    2003-01-01

    The present invention is for a compact superconducting power transmission cable operating at distribution level voltages. The superconducting cable is a conductor with a number of tapes assembled into a subconductor. These conductors are then mounted co-planarly in an elongated dielectric to produce a 3-phase cable. The arrangement increases the magnetic field parallel to the tapes thereby reducing ac losses.

  3. Single-Molecule Discrimination within Dendritic Spines of Discrete Perisynaptic Sites of Actin Filament Assembly Driving Postsynaptic Reorganization

    NASA Astrophysics Data System (ADS)

    Blanpied, Thomas A.

    2013-03-01

    In the brain, the strength of synaptic transmission between neurons is principally set by the organization of proteins within the receptive, postsynaptic cell. Synaptic strength at an individual site of contact can remain remarkably stable for months or years. However, it also can undergo diverse forms of plasticity which change the strength at that contact independent of changes to neighboring synapses. Such activity-triggered neural plasticity underlies memory storage and cognitive development, and is disrupted in pathological physiology such as addiction and schizophrenia. Much of the short-term regulation of synaptic plasticity occurs within the postsynaptic cell, in small subcompartments surrounding the synaptic contact. Biochemical subcompartmentalization necessary for synapse-specific plasticity is achieved in part by segregation of synapses to micron-sized protrusions from the cell called dendritic spines. Dendritic spines are heavily enriched in the actin cytoskeleton, and regulation of actin polymerization within dendritic spines controls both basal synaptic strength and many forms of synaptic plasticity. However, understanding the mechanism of this control has been difficult because the submicron dimensions of spines limit examination of actin dynamics in the spine interior by conventional confocal microscopy. To overcome this, we developed single-molecule tracking photoactivated localization microscopy (smtPALM) to measure the movement of individual actin molecules within living spines. This revealed inward actin flow from broad areas of the spine plasma membrane, as well as a dense central core of heterogeneous filament orientation. The velocity of single actin molecules along filaments was elevated in discrete regions within the spine, notably near the postsynaptic density but surprisingly not at the endocytic zone which is involved in some forms of plasticity. We conclude that actin polymerization is initiated at many well-separated foci within

  4. RhoA-mediated FMNL1 regulates GM130 for actin assembly and phosphorylates MAPK for spindle formation in mouse oocyte meiosis.

    PubMed

    Wang, Fei; Zhang, Liang; Duan, Xing; Zhang, Guang-Li; Wang, Zhen-Bo; Wang, Qiang; Xiong, Bo; Sun, Shao-Chen

    2015-01-01

    Formin-like 1 (FMNL1) is a member of Formin family proteins which are the actin nucleators. Although FMNL1 activities have been shown to be essential for cell adhesion, cytokinesis, cell polarization and migration in mitosis, the functional roles of mammalian FMNL1 during oocyte meiosis remain uncertain. In this study, we investigated the functions of FMNL1 in mouse oocytes using specific morpholino (MO) microinjection and live cell imaging. Immunofluorescent staining showed that in addition to its cytoplasmic distribution, FMNL1 was primarily localized at the spindle poles after germinal vesicle breakdown (GVBD). FMNL1 knockdown caused the low rate of polar body extrusion and resulted in large polar bodies. Time-lapse microscopic and immunofluorescence intensity analysis indicated that this might be due to the aberrant actin expression levels. Cortical polarity was disrupted as shown by a loss of actin cap and cortical granule free domain (CGFD) formation, which was confirmed by a failure of meiotic spindle positioning. And this might be the reason for the large polar body formation. Spindle formation was also disrupted, which might be due to the abnormal localization of p-MAPK. These results indicated that FMNL1 affected both actin dynamics and spindle formation for the oocyte polar body extrusion. Moreover, FMNL1 depletion resulted in aberrant localization and expression patterns of a cis-Golgi marker protein, GM130. Finally, we found that the small GTPase RhoA might be the upstream regulator of FMNL1. Taken together, our data indicate that FMNL1 is required for spindle organization and actin assembly through a RhoA-FMNL1-GM130 pathway during mouse oocyte meiosis.

  5. Apical domain polarization localizes actin-myosin activity to drive ratchet-like apical constriction.

    PubMed

    Mason, Frank M; Tworoger, Michael; Martin, Adam C

    2013-08-01

    Apical constriction promotes epithelia folding, which changes tissue architecture. During Drosophila gastrulation, mesoderm cells exhibit repeated contractile pulses that are stabilized such that cells apically constrict like a ratchet. The transcription factor Twist is required to stabilize cell shape. However, it is unknown how Twist spatially coordinates downstream signals to prevent cell relaxation. We find that during constriction, Rho-associated kinase (Rok) is polarized to the middle of the apical domain (medioapical cortex), separate from adherens junctions. Rok recruits or stabilizes medioapical myosin II (Myo-II), which contracts dynamic medioapical actin cables. The formin Diaphanous mediates apical actin assembly to suppress medioapical E-cadherin localization and form stable connections between the medioapical contractile network and adherens junctions. Twist is not required for apical Rok recruitment, but instead polarizes Rok medioapically. Therefore, Twist establishes radial cell polarity of Rok/Myo-II and E-cadherin and promotes medioapical actin assembly in mesoderm cells to stabilize cell shape fluctuations.

  6. Correction coil cable

    DOEpatents

    Wang, Sou-Tien

    1994-11-01

    A wire cable assembly (10, 310) adapted for the winding of electrical coils is taught. A primary intended use is for use in particle tube assemblies (532) for the superconducting super collider. The correction coil cables (10, 310) have wires (14, 314) collected in wire arrays (12, 312) with a center rib (16, 316) sandwiched therebetween to form a core assembly (18, 318 ). The core assembly (18, 318) is surrounded by an assembly housing (20, 320) having an inner spiral wrap (22, 322) and a counter wound outer spiral wrap (24, 324). An alternate embodiment (410) of the invention is rolled into a keystoned shape to improve radial alignment of the correction coil cable (410) on a particle tube (733) in a particle tube assembly (732).

  7. Cofilin-mediated actin dynamics promotes actin bundle formation during Drosophila bristle development

    PubMed Central

    Wu, Jing; Wang, Heng; Guo, Xuan; Chen, Jiong

    2016-01-01

    The actin bundle is an array of linear actin filaments cross-linked by actin-bundling proteins, but its assembly and dynamics are not as well understood as those of the branched actin network. Here we used the Drosophila bristle as a model system to study actin bundle formation. We found that cofilin, a major actin disassembly factor of the branched actin network, promotes the formation and positioning of actin bundles in the developing bristles. Loss of function of cofilin or AIP1, a cofactor of cofilin, each resulted in increased F-actin levels and severe defects in actin bundle organization, with the defects from cofilin deficiency being more severe. Further analyses revealed that cofilin likely regulates actin bundle formation and positioning by the following means. First, cofilin promotes a large G-actin pool both locally and globally, likely ensuring rapid actin polymerization for bundle initiation and growth. Second, cofilin limits the size of a nonbundled actin-myosin network to regulate the positioning of actin bundles. Third, cofilin prevents incorrect assembly of branched and myosin-associated actin filament into bundles. Together these results demonstrate that the interaction between the dynamic dendritic actin network and the assembling actin bundles is critical for actin bundle formation and needs to be closely regulated. PMID:27385345

  8. Cabling design for phased arrays

    NASA Technical Reports Server (NTRS)

    Kruger, I. D.; Turkiewicz, L.

    1972-01-01

    The ribbon-cabling system used for the AEGIS phased array which provides minimum cable bulk, complete EMI shielding, rugged mechanical design, repeatable electrical characteristics, and ease of assembly and maintenance is described. The ribbon cables are 0.040-inch thick, and in widths up to 2 1/2 inches. Their terminations are molded connectors that can be grouped in a three-tier arrangement, with cable branching accomplished by a matrix-welding technique.

  9. Gas7b (growth arrest specific protein 7b) regulates neuronal cell morphology by enhancing microtubule and actin filament assembly.

    PubMed

    Gotoh, Aina; Hidaka, Masafumi; Hirose, Keiko; Uchida, Takafumi

    2013-11-29

    Neurons undergo several morphological changes as a part of normal neuron maturation process. Alzheimer disease is associated with increased neuroproliferation and impaired neuronal maturation. In this study, we demonstrated that Gas7b (growth arrest specific protein 7b) expression in a neuronal cell line, Neuro 2A, induces cell maturation by facilitating formation of dendrite-like processes and/or filopodia projections and that Gas7b co-localizes with neurite microtubules. Molecular analysis was performed to evaluate whether Gas7b associates with actin filaments and microtubules, and the data revealed two novel roles of Gas7b in neurite outgrowth: we showed that Gas7b enhances bundling of several microtubule filaments and connects microtubules with actin filaments. These results suggest that Gas7b governs neural cell morphogenesis by enhancing the coordination between actin filaments and microtubules. We conclude that lower neuronal Gas7b levels may impact Alzheimer disease progression.

  10. Filopodia and actin arcs guide the assembly and transport of two populations of microtubules with unique dynamic parameters in neuronal growth cones

    PubMed Central

    Schaefer, Andrew W.; Kabir, Nurul; Forscher, Paul

    2002-01-01

    We have used multimode fluorescent speckle microscopy (FSM) and correlative differential interference contrast imaging to investigate the actin–microtubule (MT) interactions and polymer dynamics known to play a fundamental role in growth cone guidance. We report that MTs explore the peripheral domain (P-domain), exhibiting classical properties of dynamic instability. MT extension occurs preferentially along filopodia, which function as MT polymerization guides. Filopodial bundles undergo retrograde flow and also transport MTs. Thus, distal MT position is determined by the rate of plus-end MT assembly minus the rate of retrograde F-actin flow. Short MT displacements independent of flow are sometimes observed. MTs loop, buckle, and break as they are transported into the T-zone by retrograde flow. MT breakage results in exposure of new plus ends which can regrow, and minus ends which rapidly undergo catastrophes, resulting in efficient MT turnover. We also report a previously undetected presence of F-actin arc structures, which exhibit persistent retrograde movement across the T-zone into the central domain (C-domain) at ∼1/4 the rate of P-domain flow. Actin arcs interact with MTs and transport them into the C-domain. Interestingly, although the MTs associated with arcs are less dynamic than P-domain MTs, they elongate efficiently as a result of markedly lower catastrophe frequencies. PMID:12105186

  11. Validation of Measured Damping Trends for Flight-Like Vehicle Panel/Equipment including a Range of Cable Harness Assemblies

    NASA Technical Reports Server (NTRS)

    Smith, Andrew M.; Davis, R. Benjamin; LaVerde, Bruce T.; Fulcher, Clay W.; Jones, Douglas C.; Waldon, James M.; Craigmyle, Benjamin B.

    2012-01-01

    This validation study examines the effect on vibroacoustic response resulting from the installation of cable bundles on a curved orthogrid panel. Of interest is the level of damping provided by the installation of the cable bundles and whether this damping could be potentially leveraged in launch vehicle design. The results of this test are compared with baseline acoustic response tests without cables. Damping estimates from the measured response data are made using a new software tool that leverages a finite element model of the panel in conjunction with advanced optimization techniques. While the full test series is not yet complete, the first configuration of cable bundles that was assessed effectively increased the viscous critical damping fraction of the system by as much as 0.02 in certain frequency ranges.

  12. Specific Transformation of Assembly with Actin Filaments and Molecular Motors in a Cell-Sized Self-Emerged Liposome

    NASA Astrophysics Data System (ADS)

    Takiguchi, Kingo; Negishi, Makiko; Tanaka-Takiguchi, Yohko; Hayashi, Masahito; Yoshikawa, Kenichi

    2014-12-01

    Eukaryotes, by the same combination of cytoskeleton and molecular motor, for example actin filament and myosin, can generate a variety of movements. For this diversity, the organization of biological machineries caused by the confinement and/or crowding effects of internal living cells, may play very important roles.

  13. Actinic keratosis

    MedlinePlus

    Solar keratosis; Sun-induced skin changes - keratosis; Keratosis - actinic (solar); Skin lesion - actinic keratosis ... likely to develop it if you: Have fair skin, blue or green eyes, or blond or red ...

  14. Determining Damping Trends from a Range of Cable Harness Assemblies on a Launch Vehicle Panel from Test Measurements

    NASA Technical Reports Server (NTRS)

    Smith, Andrew; Davis, R. Ben; LaVerde, Bruce; Jones, Douglas

    2012-01-01

    The team of authors at Marshall Space Flight Center (MSFC) has been investigating estimating techniques for the vibration response of launch vehicle panels excited by acoustics and/or aero-fluctuating pressures. Validation of the approaches used to estimate these environments based on ground tests of flight like hardware is of major importance to new vehicle programs. The team at MSFC has recently expanded upon the first series of ground test cases completed in December 2010. The follow on tests recently completed are intended to illustrate differences in damping that might be expected when cable harnesses are added to the configurations under test. This validation study examines the effect on vibroacoustic response resulting from the installation of cable bundles on a curved orthogrid panel. Of interest is the level of damping provided by the installation of the cable bundles and whether this damping could be potentially leveraged in launch vehicle design. The results of this test are compared with baseline acoustic response tests without cables. Damping estimates from the measured response data are made using a new software tool that employs a finite element model (FEM) of the panel in conjunction with advanced optimization techniques. This paper will report on the \\damping trend differences. observed from response measurements for several different configurations of cable harnesses. The data should assist vibroacoustics engineers to make more informed damping assumptions when calculating vibration response estimates when using model based analysis approach. Achieving conservative estimates that have more flight like accuracy is desired. The paper may also assist analysts in determining how ground test data may relate to expected flight response levels. Empirical response estimates may also need to be adjusted if the measured response used as an input to the study came from a test article without flight like cable harnesses.

  15. Nano-ZnO leads to tubulin macrotube assembly and actin bundling, triggering cytoskeletal catastrophe and cell necrosis

    NASA Astrophysics Data System (ADS)

    García-Hevia, Lorena; Valiente, Rafael; Martín-Rodríguez, Rosa; Renero-Lecuna, Carlos; González, Jesús; Rodríguez-Fernández, Lidia; Aguado, Fernando; Villegas, Juan C.; Fanarraga, Mónica L.

    2016-05-01

    Zinc is a crucial element in biology that plays chief catalytic, structural and protein regulatory roles. Excess cytoplasmic zinc is toxic to cells so there are cell-entry and intracellular buffering mechanisms that control intracellular zinc availability. Tubulin and actin are two zinc-scavenging proteins that are essential components of the cellular cytoskeleton implicated in cell division, migration and cellular architecture maintenance. Here we demonstrate how exposure to different ZnO nanostructures, namely ZnO commercial nanoparticles and custom-made ZnO nanowires, produce acute cytotoxic effects in human keratinocytes (HaCat) and epithelial cells (HeLa) triggering a dose-dependent cell retraction and collapse. We show how engulfed ZnO nanoparticles dissolve intracellularly, triggering actin filament bundling and structural changes in microtubules, transforming these highly dynamic 25 nm diameter polymers into rigid macrotubes of tubulin, severely affecting cell proliferation and survival. Our results demonstrate that nano-ZnO causes acute cytoskeletal collapse that triggers necrosis, followed by a late reactive oxygen species (ROS)-dependent apoptotic process.Zinc is a crucial element in biology that plays chief catalytic, structural and protein regulatory roles. Excess cytoplasmic zinc is toxic to cells so there are cell-entry and intracellular buffering mechanisms that control intracellular zinc availability. Tubulin and actin are two zinc-scavenging proteins that are essential components of the cellular cytoskeleton implicated in cell division, migration and cellular architecture maintenance. Here we demonstrate how exposure to different ZnO nanostructures, namely ZnO commercial nanoparticles and custom-made ZnO nanowires, produce acute cytotoxic effects in human keratinocytes (HaCat) and epithelial cells (HeLa) triggering a dose-dependent cell retraction and collapse. We show how engulfed ZnO nanoparticles dissolve intracellularly, triggering actin

  16. Nano-ZnO leads to tubulin macrotube assembly and actin bundling, triggering cytoskeletal catastrophe and cell necrosis.

    PubMed

    García-Hevia, Lorena; Valiente, Rafael; Martín-Rodríguez, Rosa; Renero-Lecuna, Carlos; González, Jesús; Rodríguez-Fernández, Lidia; Aguado, Fernando; Villegas, Juan C; Fanarraga, Mónica L

    2016-06-07

    Zinc is a crucial element in biology that plays chief catalytic, structural and protein regulatory roles. Excess cytoplasmic zinc is toxic to cells so there are cell-entry and intracellular buffering mechanisms that control intracellular zinc availability. Tubulin and actin are two zinc-scavenging proteins that are essential components of the cellular cytoskeleton implicated in cell division, migration and cellular architecture maintenance. Here we demonstrate how exposure to different ZnO nanostructures, namely ZnO commercial nanoparticles and custom-made ZnO nanowires, produce acute cytotoxic effects in human keratinocytes (HaCat) and epithelial cells (HeLa) triggering a dose-dependent cell retraction and collapse. We show how engulfed ZnO nanoparticles dissolve intracellularly, triggering actin filament bundling and structural changes in microtubules, transforming these highly dynamic 25 nm diameter polymers into rigid macrotubes of tubulin, severely affecting cell proliferation and survival. Our results demonstrate that nano-ZnO causes acute cytoskeletal collapse that triggers necrosis, followed by a late reactive oxygen species (ROS)-dependent apoptotic process.

  17. Three-dimensional structure of actin filaments and of an actin gel made with actin-binding protein.

    PubMed

    Niederman, R; Amrein, P C; Hartwig, J

    1983-05-01

    Purified muscle actin and mixtures of actin and actin-binding protein were examined in the transmission electron microscope after fixation, critical point drying, and rotary shadowing. The three-dimensional structure of the protein assemblies was analyzed by a computer-assisted graphic analysis applicable to generalized filament networks. This analysis yielded information concerning the frequency of filament intersections, the filament length between these intersections, the angle at which filaments branch at these intersections, and the concentration of filaments within a defined volume. Purified actin at a concentration of 1 mg/ml assembled into a uniform mass of long filaments which overlap at random angles between 0 degrees and 90 degrees. Actin in the presence of macrophage actin-binding protein assembled into short, straight filaments, organized in a perpendicular branching network. The distance between branch points was inversely related to the molar ratio of actin-binding protein to actin. This distance was what would be predicted if actin filaments grew at right angles off of nucleation sites on the two ends of actin-binding protein dimers, and then annealed. The results suggest that actin in combination with actin-binding protein self-assembles to form a three-dimensional network resembling the peripheral cytoskeleton of motile cells.

  18. In Vitro Biochemical Characterization of Cytokinesis Actin-Binding Proteins.

    PubMed

    Zimmermann, Dennis; Morganthaler, Alisha N; Kovar, David R; Suarez, Cristian

    2016-01-01

    Characterizing the biochemical and biophysical properties of purified proteins is critical to understand the underlying molecular mechanisms that facilitate complicated cellular processes such as cytokinesis. Here we outline in vitro assays to investigate the effects of cytokinesis actin-binding proteins on actin filament dynamics and organization. We describe (1) multicolor single-molecule TIRF microscopy actin assembly assays, (2) "bulk" pyrene actin assembly/disassembly assays, and (3) "bulk" sedimentation actin filament binding and bundling assays.

  19. Superconductor cable

    DOEpatents

    Allais, Arnaud; Schmidt, Frank; Marzahn, Erik

    2010-05-04

    A superconductor cable is described, having a superconductive flexible cable core (1) , which is laid in a cryostat (2, 3, 4), in which the cable core (1) runs in the cryostat (2, 3, 4) in the form of a wave or helix at room temperature.

  20. Cable Television.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    The Federal Communications Commission (FCC) presents a brief description of cable television and explains some basic regulations pertaining to it. The history of cable regulation covers the initial jurisdiction, economic considerations of the regulation, court tests, and the holding of public hearings. The major provisions of new cable rules are…

  1. Cable Economics.

    ERIC Educational Resources Information Center

    Cable Television Information Center, Washington, DC.

    A guide to the economic factors that influence cable television systems is presented. Designed for local officials who must have some familiarity with cable operations in order to make optimum decisions, the guide analyzes the financial framework of a cable system, not only from the operators viewpoint, but also from the perspective of the…

  2. Formation and Destabilization of Actin Filaments with Tetramethylrhodamine-Modified Actin

    PubMed Central

    Kudryashov, Dmitry S.; Phillips, Martin; Reisler, Emil

    2004-01-01

    Actin labeling at Cys374 with tethramethylrhodamine derivatives (TMR-actin) has been widely used for direct observation of the in vitro filaments growth, branching, and treadmilling, as well as for the in vivo visualization of actin cytoskeleton. The advantage of TMR-actin is that it does not lock actin in filaments (as rhodamine-phalloidin does), possibly allowing for its use in investigating the dynamic assembly behavior of actin polymers. Although it is established that TMR-actin alone is polymerization incompetent, the impact of its copolymerization with unlabeled actin on filament structure and dynamics has not been tested yet. In this study, we show that TMR-actin perturbs the filaments structure when copolymerized with unlabeled actin; the resulting filaments are more fragile and shorter than the control filaments. Due to the increased severing of copolymer filaments, TMR-actin accelerates the polymerization of unlabeled actin in solution also at mole ratios lower than those used in most fluorescence microscopy experiments. The destabilizing and severing effect of TMR-actin is countered by filament stabilizing factors, phalloidin, S1, and tropomyosin. These results point to an analogy between the effects of TMR-actin and severing proteins on F-actin, and imply that TMR-actin may be inappropriate for investigations of actin filaments dynamics. PMID:15298916

  3. Actinous enigma or enigmatic actin

    PubMed Central

    Povarova, Olga I; Uversky, Vladimir N; Kuznetsova, Irina M; Turoverov, Konstantin K

    2014-01-01

    Being the most abundant protein of the eukaryotic cell, actin continues to keep its secrets for more than 60 years. Everything about this protein, its structure, functions, and folding, is mysteriously counterintuitive, and this review represents an attempt to solve some of the riddles and conundrums commonly found in the field of actin research. In fact, actin is a promiscuous binder with a wide spectrum of biological activities. It can exist in at least three structural forms, globular, fibrillar, and inactive (G-, F-, and I-actin, respectively). G-actin represents a thermodynamically instable, quasi-stationary state, which is formed in vivo as a result of the energy-intensive, complex posttranslational folding events controlled and driven by cellular folding machinery. The G-actin structure is dependent on the ATP and Mg2+ binding (which in vitro is typically substituted by Ca2+) and protein is easily converted to the I-actin by the removal of metal ions and by action of various denaturing agents (pH, temperature, and chemical denaturants). I-actin cannot be converted back to the G-form. Foldable and “natively folded” forms of actin are always involved in interactions either with the specific protein partners, such as Hsp70 chaperone, prefoldin, and the CCT chaperonin during the actin folding in vivo or with Mg2+ and ATP as it takes place in the G-form. We emphasize that the solutions for the mysteries of actin multifunctionality, multistructurality, and trapped unfolding can be found in the quasi-stationary nature of this enigmatic protein, which clearly possesses many features attributed to both globular and intrinsically disordered proteins.

  4. Effects of latrunculin B on the actin cytoskeleton and hyphal growth in Phytophthora infestans.

    PubMed

    Ketelaar, Tijs; Meijer, Harold J G; Spiekerman, Marjolein; Weide, Rob; Govers, Francine

    2012-12-01

    The actin cytoskeleton is conserved in all eukaryotes, but its functions vary among different organisms. In oomycetes, the function of the actin cytoskeleton has received relatively little attention. We have performed a bioinformatics study and show that oomycete actin genes fall within a distinct clade that is divergent from plant, fungal and vertebrate actin genes. To obtain a better understanding of the functions of the actin cytoskeleton in hyphal growth of oomycetes, we studied the actin organization in Phytophthora infestans hyphae and the consequences of treatment with the actin depolymerising drug latrunculin B (latB). This revealed that latB treatment causes a concentration dependent inhibition of colony expansion and aberrant hyphal growth. The most obvious aberrations observed upon treatment with 0.1 μM latB were increased hyphal branching and irregular tube diameters whereas at higher concentrations latB (0.5 and 1 μM) tips of expanding hyphae changed into balloon-like shapes. This aberrant growth correlated with changes in the organization of the actin cytoskeleton. In untreated hyphae, staining with fluorescently tagged phalloidin revealed two populations of actin filaments: long, axially oriented actin filament cables and cortical actin filament plaques. Two hyphal subtypes were recognized, one containing only plaques and the other containing both cables and plaques. In the latter, some hyphae had an apical zone without actin filament plaques. Upon latB treatment, the proportion of hyphae without actin filament cables increased and there were more hyphae with a short apical zone without actin filament plaques. In general, actin filament plaques were more resilient against actin depolymerisation than actin filament cables. Besides disturbing hyphal growth and actin organization, actin depolymerisation also affected the positioning of nuclei. In the presence of latB, the distance between nuclei and the hyphal tip decreased, suggesting that the actin

  5. Mechanical Rope and Cable

    DTIC Science & Technology

    1975-04-01

    Steel, Carbon, High Strength MIL-W-24223 Wire Rope , Aluminized MIL-W-32312 (MO) Vire Rope Assemblies, Single Log; for Medium Cableway MII-W-81002 (WP...II AD-AO13 345 MECHANICAL ROPE AND CABLE National Materials Advisory Board (NAS-NAE) I’I Prepared for: Department of Defense April 1975 DISTRIBUTED...andSubtitle) S. TYPE[ OF REPORT & PERIOD COVERED TITLE(endSubttle)Final Report Mechanical Rope and Cable FnalReport____ 4. PERFORMING ORG. REPORT

  6. Cable compliance

    NASA Technical Reports Server (NTRS)

    Kerley, J.; Eklund, W.; Burkhardt, R.; Rossoni, P.

    1992-01-01

    The object of the investigation was to solve mechanical problems using cable-in-bending and cable-in-torsion. These problems included robotic contacts, targets, and controls using cable compliance. Studies continued in the use of cable compliance for the handicapped and the elderly. These included work stations, walkers, prosthetic knee joints, elbow joints, and wrist joints. More than half of these objects were met, and models were made and studies completed on most of the others. It was concluded that the many different and versatile solutions obtained only opened the door to many future challenges.

  7. The unusual dynamics of parasite actin result from isodesmic polymerization.

    PubMed

    Skillman, Kristen M; Ma, Christopher I; Fremont, Daved H; Diraviyam, Karthikeyan; Cooper, John A; Sept, David; Sibley, L David

    2013-01-01

    Previous reports have indicated that parasite actins are short and inherently unstable, despite being required for motility. Here we re-examine the polymerization properties of actin in Toxoplasma gondii, unexpectedly finding that it exhibits isodesmic polymerization in contrast to the conventional nucleation-elongation process of all previously studied actins from both eukaryotes and bacteria. Polymerization kinetics of actin in T. gondii lacks both a lag phase and critical concentration, normally characteristic of actins. Unique among actins, the kinetics of assembly can be fit with a single set of rate constants for all subunit interactions, without need for separate nucleation and elongation rates. This isodesmic model accurately predicts the assembly, disassembly and the size distribution of actin filaments in T. gondii in vitro, providing a mechanistic explanation for actin dynamics in vivo. Our findings expand the repertoire of mechanisms by which actin polymerization is governed and offer clues about the evolution of self-assembling, stabilized protein polymers.

  8. Formin' actin in the nucleus.

    PubMed

    Baarlink, Christian; Grosse, Robert

    2014-01-01

    Many if not most proteins can, under certain conditions, change cellular compartments, such as, for example, shuttling from the cytoplasm to the nucleus. Thus, many proteins may exert functions in various and very different subcellular locations, depending on the signaling context. A large amount of actin regulatory proteins has been detected in the mammalian cell nucleus, although their potential roles are much debated and are just beginning to emerge. Recently, members of the formin family of actin nucleators were also reported to dynamically localize to the nuclear environment. Here we discuss our findings that specific diaphanous-related formins can promote nuclear actin assembly in a signal-dependent manner.

  9. G-actin regulates rapid induction of actin nucleation by mDia1 to restore cellular actin polymers.

    PubMed

    Higashida, Chiharu; Suetsugu, Shiro; Tsuji, Takahiro; Monypenny, James; Narumiya, Shuh; Watanabe, Naoki

    2008-10-15

    mDia1 belongs to the formin family of proteins that share FH1 and FH2 domains. Although formins play a critical role in the formation of many actin-based cellular structures, the physiological regulation of formin-mediated actin assembly within the cell is still unknown. Here we show that cells possess an acute actin polymer restoration mechanism involving mDia1. By using single-molecule live-cell imaging, we found that several treatments including low-dose G-actin-sequestering drugs and unpolymerizable actin mutants activate mDia1 to initiate fast directional movement. The FH2 region, the core domain for actin nucleation, is sufficient to respond to latrunculin B (LatB) to increase its actin nucleation frequency. Simulation analysis revealed an unexpected paradoxical effect of LatB that leads to a several fold increase in free G-actin along with an increase in total G-actin. These results indicate that in cells, the actin nucleation frequency of mDia1 is enhanced not only by Rho, but also strongly through increased catalytic efficiency of the FH2 domain. Consistently, frequent actin nucleation by mDia1 was found around sites of vigorous actin disassembly. Another major actin nucleator, the Arp2/3 complex, was not affected by the G-actin increase induced by LatB. Taken together, we propose that transient accumulation of G-actin works as a cue to promote mDia1-catalyzed actin nucleation to execute rapid reassembly of actin filaments.

  10. Superconducting cable-in-conduit low resistance splice

    DOEpatents

    Artman, Thomas A.

    2003-06-24

    A low resistance splice connects two cable-in-conduit superconductors to each other. Dividing collars for arranging sub-cable units from each conduit are provided, along with clamping collars for mating each sub-cable wire assembly to form mated assemblies. The mated assemblies ideally can be accomplished by way of splicing collar. The mated assemblies are cooled by way of a flow of coolant, preferably helium. A method for implementing such a splicing is also described.

  11. Actinic reticuloid

    SciTech Connect

    Marx, J.L.; Vale, M.; Dermer, P.; Ragaz, A.; Michaelides, P.; Gladstein, A.H.

    1982-09-01

    A 58-year-old man has his condition diagnosed as actinic reticuloid on the basis of clinical and histologic findings and phototesting data. He had clinical features resembling mycosis fungoides in light-exposed areas. Histologic findings disclosed a bandlike infiltrate with atypical mononuclear cells in the dermis and scattered atypical cells in the epidermis. Electron microscopy disclosed mononuclear cells with bizarre, convoluted nuclei, resembling cerebriform cells of Lutzner. Phototesting disclosed a diminished minimal erythemal threshold to UV-B and UV-A. Microscopic changes resembling actinic reticuloid were reproduced in this patient 24 and 72 hours after exposure to 15 minimal erythemal doses of UV-B.

  12. Dynamic network morphology and tension buildup in a 3D model of cytokinetic ring assembly.

    PubMed

    Bidone, Tamara C; Tang, Haosu; Vavylonis, Dimitrios

    2014-12-02

    During fission yeast cytokinesis, actin filaments nucleated by cortical formin Cdc12 are captured by myosin motors bound to a band of cortical nodes and bundled by cross-linking proteins. The myosin motors exert forces on the actin filaments, resulting in a net pulling of the nodes into a contractile ring, while cross-linking interactions help align actin filaments and nodes into a single bundle. We used these mechanisms in a three-dimensional computational model of contractile ring assembly, with semiflexible actin filaments growing from formins at cortical nodes, capturing of filaments by neighboring nodes, and cross-linking among filaments through attractive interactions. The model was used to predict profiles of actin filament density at the cell cortex, morphologies of condensing node-filament networks, and regimes of cortical tension by varying the node pulling force and strength of cross-linking among actin filaments. Results show that cross-linking interactions can lead to confinement of actin filaments at the simulated cortical boundary. We show that the ring-formation region in parameter space lies close to regions leading to clumps, meshworks or double rings, and stars/cables. Since boundaries between regions are not sharp, transient structures that resemble clumps, stars, and meshworks can appear in the process of ring assembly. These results are consistent with prior experiments with mutations in actin-filament turnover regulators, myosin motor activity, and changes in the concentration of cross-linkers that alter the morphology of the condensing network. Transient star shapes appear in some simulations, and these morphologies offer an explanation for star structures observed in prior experimental images. Finally, we quantify tension along actin filaments and forces on nodes during ring assembly and show that the mechanisms describing ring assembly can also drive ring constriction once the ring is formed.

  13. Microtubules as Platforms for Assaying Actin Polymerization In Vivo

    PubMed Central

    Oelkers, J. Margit; Vinzenz, Marlene; Nemethova, Maria; Jacob, Sonja; Lai, Frank P. L.; Block, Jennifer; Szczodrak, Malgorzata; Kerkhoff, Eugen; Backert, Steffen; Schlüter, Kai; Stradal, Theresia E. B.; Small, J. Victor

    2011-01-01

    The actin cytoskeleton is continuously remodeled through cycles of actin filament assembly and disassembly. Filaments are born through nucleation and shaped into supramolecular structures with various essential functions. These range from contractile and protrusive assemblies in muscle and non-muscle cells to actin filament comets propelling vesicles or pathogens through the cytosol. Although nucleation has been extensively studied using purified proteins in vitro, dissection of the process in cells is complicated by the abundance and molecular complexity of actin filament arrays. We here describe the ectopic nucleation of actin filaments on the surface of microtubules, free of endogenous actin and interfering membrane or lipid. All major mechanisms of actin filament nucleation were recapitulated, including filament assembly induced by Arp2/3 complex, formin and Spir. This novel approach allows systematic dissection of actin nucleation in the cytosol of live cells, its genetic re-engineering as well as screening for new modifiers of the process. PMID:21603613

  14. Superconductor cable

    DOEpatents

    Allais, Arnaud; Schmidt, Frank (Langenhagen, DE

    2009-12-15

    A superconductor cable includes a superconductive cable core (1) and a cryostat (2) enclosing the same. The cable core (1) has a superconductive conductor (3), an insulation (4) surrounding the same and a shielding (5) surrounding the insulation (4). A layer (3b) of a dielectric or semiconducting material is applied to a central element (3a) formed from a normally conducting material as a strand or tube and a layer (3c) of at least one wire or strip of superconductive material is placed helically on top. The central element (3a) and the layer (3c) are connected to each other in an electrically conducting manner at the ends of the cable core (1).

  15. Cable manufacture

    NASA Technical Reports Server (NTRS)

    Gamble, P.

    1972-01-01

    A survey is presented of flat electrical cable manufacturing, with particular reference to patented processes. The economics of manufacture based on an analysis of material and operating costs is considered for the various methods. Attention is given to the competitive advantages of the several processes and their resulting products. The historical area of flat cable manufacture is presented to give a frame of reference for the survey.

  16. Cable tester

    NASA Astrophysics Data System (ADS)

    Rammage, Robert L.

    1990-10-01

    A device for sequentially testing the plurality of connectors in a wiring harness is disclosed. The harness is attached to the tester by means of adapter cables and a rotary switch is used to sequentially, individually test the connectors by passing a current through the connector. If the connector is unbroken, a light will flash to show it is electrically sound. The adapters allow a large number of cable configurations to be tested using a single tester configuration.

  17. Labeling F-actin barbed ends with rhodamine-actin in permeabilized neuronal growth cones.

    PubMed

    Marsick, Bonnie M; Letourneau, Paul C

    2011-03-17

    for actin monomer addition to barbed ends, rhodamine-actin assembles onto free barbed ends. If the attractive cue is presented in a gradient, such as being released from a micropipette positioned to one side of a growth cone, the incorporation of rhodamine-actin onto F-actin barbed ends will be greater in the growth cone side toward the micropipette. Growth cones are small and delicate cell structures. The procedures of permeabilization, rhodamine-actin incorporation, fixation and fluorescence visualization are all carefully done and can be conducted on the stage of an inverted microscope. These methods can be applied to studying local actin polymerization in migrating neurons, other primary tissue cells or cell lines.

  18. Formin DAAM1 Organizes Actin Filaments in the Cytoplasmic Nodal Actin Network

    PubMed Central

    Luo, Weiwei; Lieu, Zi Zhao; Manser, Ed; Bershadsky, Alexander D.; Sheetz, Michael P.

    2016-01-01

    A nodal cytoplasmic actin network underlies actin cytoplasm cohesion in the absence of stress fibers. We previously described such a network that forms upon Latrunculin A (LatA) treatment, in which formin DAAM1 was localized at these nodes. Knock down of DAAM1 reduced the mobility of actin nodes but the nodes remained. Here we have investigated DAAM1 containing nodes after LatA washout. DAAM1 was found to be distributed between the cytoplasm and the plasma membrane. The membrane binding likely occurs through an interaction with lipid rafts, but is not required for F-actin assembly. Interesting the forced interaction of DAAM1 with plasma membrane through a rapamycin-dependent linkage, enhanced F-actin assembly at the cell membrane (compared to the cytoplasm) after the LatA washout. However, immediately after addition of both rapamycin and LatA, the cytoplasmic actin nodes formed transiently, before DAAM1 moved to the membrane. This was consistent with the idea that DAAM1 was initially anchored to cytoplasmic actin nodes. Further, photoactivatable tracking of DAAM1 showed DAAM1 was immobilized at these actin nodes. Thus, we suggest that DAAM1 organizes actin filaments into a nodal complex, and such nodal complexes seed actin network recovery after actin depolymerization. PMID:27760153

  19. F- and G-actin homeostasis regulates mechanosensitive actin nucleation by formins.

    PubMed

    Higashida, Chiharu; Kiuchi, Tai; Akiba, Yushi; Mizuno, Hiroaki; Maruoka, Masahiro; Narumiya, Shuh; Mizuno, Kensaku; Watanabe, Naoki

    2013-04-01

    Physical force evokes rearrangement of the actin cytoskeleton. Signalling pathways such as tyrosine kinases, stretch-activated Ca(2+) channels and Rho GTPases are involved in force sensing. However, how signals are transduced to actin assembly remains obscure. Here we show mechanosensitive actin polymerization by formins (formin homology proteins). Cells overexpressing mDia1 increased the amount of F-actin on release of cell tension. Fluorescence single-molecule speckle microscopy revealed rapid induction of processive actin assembly by mDia1 on cell cortex deformation. mDia1 lacking the Rho-binding domain and other formins exhibited mechanosensitive actin nucleation, suggesting Rho-independent activation. Mechanosensitive actin nucleation by mDia1 required neither Ca(2+) nor kinase signalling. Overexpressing LIM kinase abrogated the induction of processive mDia1. Furthermore, s-FDAPplus (sequential fluorescence decay after photoactivation) analysis revealed a rapid actin monomer increase on cell cortex deformation. Our direct visualization of the molecular behaviour reveals a mechanosensitive actin filament regeneration mechanism in which G-actin released by actin remodelling plays a pivotal role.

  20. The F-actin bundler α-actinin Ain1 is tailored for ring assembly and constriction during cytokinesis in fission yeast

    PubMed Central

    Li, Yujie; Christensen, Jenna R.; Homa, Kaitlin E.; Hocky, Glen M.; Fok, Alice; Sees, Jennifer A.; Voth, Gregory A.; Kovar, David R.

    2016-01-01

    The actomyosin contractile ring is a network of cross-linked actin filaments that facilitates cytokinesis in dividing cells. Contractile ring formation has been well characterized in Schizosaccharomyces pombe, in which the cross-linking protein α-actinin SpAin1 bundles the actin filament network. However, the specific biochemical properties of SpAin1 and whether they are tailored for cytokinesis are not known. Therefore we purified SpAin1 and quantified its ability to dynamically bind and bundle actin filaments in vitro using a combination of bulk sedimentation assays and direct visualization by two-color total internal reflection fluorescence microscopy. We found that, while SpAin1 bundles actin filaments of mixed polarity like other α-actinins, SpAin1 has lower bundling activity and is more dynamic than human α-actinin HsACTN4. To determine whether dynamic bundling is important for cytokinesis in fission yeast, we created the less dynamic bundling mutant SpAin1(R216E). We found that dynamic bundling is critical for cytokinesis, as cells expressing SpAin1(R216E) display disorganized ring material and delays in both ring formation and constriction. Furthermore, computer simulations of initial actin filament elongation and alignment revealed that an intermediate level of cross-linking best facilitates filament alignment. Together our results demonstrate that dynamic bundling by SpAin1 is important for proper contractile ring formation and constriction. PMID:27075176

  1. Exploring the Stability Limits of Actin and Its Suprastructures

    PubMed Central

    Rosin, Christopher; Erlkamp, Mirko; Ecken, Julian von der; Raunser, Stefan; Winter, Roland

    2014-01-01

    Actin is the main component of the microfilament system in eukaryotic cells and can be found in distinct morphological states. Global (G)-actin is able to assemble into highly organized, supramolecular cellular structures known as filamentous (F)-actin and bundled (B)-actin. To evaluate the structure and stability of G-, F-, and B-actin over a wide range of temperatures and pressures, we used Fourier transform infrared spectroscopy in combination with differential scanning and pressure perturbation calorimetry, small-angle x-ray scattering, laser confocal scanning microscopy, and transmission electron microscopy. Our analysis was designed to provide new (to our knowledge) insights into the stabilizing forces of actin self-assembly and to reveal the stability of the actin polymorphs, including in conditions encountered in extreme environments. In addition, we sought to explain the limited pressure stability of actin self-assembly observed in vivo. G-actin is not only the least temperature-stable but also the least pressure-stable actin species. Under abyssal conditions, where temperatures as low as 1–4°C and pressures up to 1 kbar are reached, G-actin is hardly stable. However, the supramolecular assemblies of actin are stable enough to withstand the extreme conditions usually encountered on Earth. Beyond ∼3–4 kbar, filamentous structures disassemble, and beyond ∼4 kbar, complete dissociation of F-actin structures is observed. Between ∼1 and 2 kbar, some disordering of actin assemblies commences, in agreement with in vivo observations. The limited pressure stability of the monomeric building block seems to be responsible for the suppression of actin assembly in the kbar pressure range. PMID:25517163

  2. Intrinsic, Functional, and Structural Properties of β-Thymosins and β-Thymosin/WH2 Domains in the Regulation and Coordination of Actin Self-Assembly Dynamics and Cytoskeleton Remodeling.

    PubMed

    Renault, L

    2016-01-01

    β-Thymosins are a family of heat-stable multifunctional polypeptides that are expressed as small proteins of about 5kDa (~45 amino acids) almost exclusively in multicellular animals. They were first isolated from the thymus. As full-length or truncated polypeptides, they appear to stimulate a broad range of extracellular activities in various signaling pathways, including tissue repair and regeneration, inflammation, cell migration, and immune defense. However, their cell surface receptors and structural mechanisms of regulations in these multiple pathways remain still poorly understood. Besides their extracellular activities, they belong to a larger family of small, intrinsically disordered actin-binding domains called WH2/β-thymosin domains that have been identified in more than 1800 multidomain proteins found in different taxonomic domains of life and involved in various actin-based motile processes including cell morphogenesis, motility, adhesions, tissue development, intracellular trafficking, or pathogen infections. This review briefly surveys the main recent findings to understand how these small, intrinsically disordered but functional domains can interact with many unrelated partners and can thus integrate and coordinate various intracellular activities in actin self-assembly dynamics and cell signaling pathways linked to their cytoskeleton remodeling.

  3. Joystick With Cable Springs Offers Better Feel

    NASA Technical Reports Server (NTRS)

    Kerley, James; Ecklund, Wayne

    1992-01-01

    Improved joystick allows motion in 6 degrees of freedom, biased toward central position and orientation by 16 segments of cable serving as springs. Improvement in feel and control results from nonlinear compliance of cable-spring assembly. Nonlinear variations accommodate natural reactions of hand and brain. Operator functions as part of feedback control loop. More comfortable, increases ability to exert control and reduces fatigue.

  4. Polymerization of actin by positively charged liposomes

    PubMed Central

    1988-01-01

    By cosedimentation, spectrofluorimetry, and electron microscopy, we have established that actin is induced to polymerize at low salt concentrations by positively charged liposomes. This polymerization occurs only at the surface of the liposomes, and thus monomers not in direct contact with the liposome remain monomeric. The integrity of the liposome membrane is necessary to maintain actin in its polymerized state since disruption of the liposome depolymerizes actin. Actin polymerized at the surface of the liposome is organized into two filamentous structures: sheets of parallel filaments in register and a netlike organization. Spectrofluorimetric analysis with the probe N- pyrenyl-iodoacetamide shows that actin is in the F conformation, at least in the environment of the probe. However, actin assembly induced by the liposome is not accompanied by full ATP hydrolysis as observed in vitro upon addition of salts. PMID:3360852

  5. Actin is required for IFT regulation in Chlamydomonas reinhardtii.

    PubMed

    Avasthi, Prachee; Onishi, Masayuki; Karpiak, Joel; Yamamoto, Ryosuke; Mackinder, Luke; Jonikas, Martin C; Sale, Winfield S; Shoichet, Brian; Pringle, John R; Marshall, Wallace F

    2014-09-08

    Assembly of cilia and flagella requires intraflagellar transport (IFT), a highly regulated kinesin-based transport system that moves cargo from the basal body to the tip of flagella [1]. The recruitment of IFT components to basal bodies is a function of flagellar length, with increased recruitment in rapidly growing short flagella [2]. The molecular pathways regulating IFT are largely a mystery. Because actin network disruption leads to changes in ciliary length and number, actin has been proposed to have a role in ciliary assembly. However, the mechanisms involved are unknown. In Chlamydomonas reinhardtii, conventional actin is found in both the cell body and the inner dynein arm complexes within flagella [3, 4]. Previous work showed that treating Chlamydomonas cells with the actin-depolymerizing compound cytochalasin D resulted in reversible flagellar shortening [5], but how actin is related to flagellar length or assembly remains unknown. Here we utilize small-molecule inhibitors and genetic mutants to analyze the role of actin dynamics in flagellar assembly in Chlamydomonas reinhardtii. We demonstrate that actin plays a role in IFT recruitment to basal bodies during flagellar elongation and that when actin is perturbed, the normal dependence of IFT recruitment on flagellar length is lost. We also find that actin is required for sufficient entry of IFT material into flagella during assembly. These same effects are recapitulated with a myosin inhibitor, suggesting that actin may act via myosin in a pathway by which flagellar assembly is regulated by flagellar length.

  6. 16. VIEW OF JUNCTION BETWEEN CABLE CHASE AND SHIELDING TANK. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. VIEW OF JUNCTION BETWEEN CABLE CHASE AND SHIELDING TANK. SHOWS CABLES AND LINES IN THE TRENCH, POLE OF FRAME ASSEMBLY, AND EQUIPMENT IN CONCRETE BOX ADJACENT TO CABLE CHASE. INEL PHOTO NUMBER 65-6178, TAKEN NOVEMBER 10, 1965. - Idaho National Engineering Laboratory, Advanced Reentry Vehicle Fusing System, Scoville, Butte County, ID

  7. Tool for cutting insulation from electrical cables

    DOEpatents

    Harless, Charles E.; Taylor, Ward G.

    1978-01-01

    This invention is an efficient hand tool for precisely slitting the sheath of insulation on an electrical cable--e.g., a cable two inches in diameter--in a manner facilitating subsequent peeling or stripping of the insulation. The tool includes a rigid frame which is slidably fitted on an end section of the cable. The frame carries a rigidly affixed handle and an opposed, elongated blade-and-handle assembly. The blade-and-handle assembly is pivotally supported by a bracket which is slidably mounted on the frame for movement toward and away from the cable, thus providing an adjustment for the depth of cut. The blade-and-handle assembly is mountable to the bracket in two pivotable positions. With the assembly mounted in the first position, the tool is turned about the cable to slit the insulation circumferentially. With the assembly mounted in the second position, the tool is drawn along the cable to slit the insulation axially. When cut both circumferentially and axially, the insulation can easily be peeled from the cable.

  8. Cable Television.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    This report provides information about cable television and the Federal Communications Commission's (FCC) responsibilities in regulating its operation. The initial jurisdiction and rules covered in this report pertain to the court test, public hearing, certificate of compliance, franchising, signal carriage, leapfrogging, access and origination…

  9. Underwater splice for submarine coaxial cable

    SciTech Connect

    Inouye, A.T.; Roe, T. Jr.; Tausing, W.R.; Wilson, J.V.

    1984-10-30

    The invention is a device for splicing submarine coaxial cable underwater on the seafloor with a simple push-on operation to restore and maintain electrical and mechanical strength integrity; the splice device is mateable directly with the severed ends of a coaxial cable to be repaired. Splicing assemblies comprise a dielectric pressure compensating fluid filled guide cavity, a gelled castor oil cap and wiping seals for exclusion of seawater, electrical contacts, a cable strength restoration mechanism, and a pressure compensation system for controlled extrusion of and depletion loss prevention of dielectric seal fluid during cable splicing. A splice is made underwater by directly inserting prepared ends of coaxial cable, having no connector attachments, into splicing assemblies.

  10. Actinic Prurigo.

    PubMed

    Rodríguez-Carreón, Alma Angélica; Rodríguez-Lobato, Erika; Rodríguez-Gutiérrez, Georgina; Cuevas-González, Juan Carlos; Mancheno-Valencia, Alexandra; Solís-Arias, Martha Patricia; Vega-Memije, María Elisa; Hojyo-Tomoka, María Teresa; Domínguez-Soto, Luciano

    2015-01-01

    Actinic prurigo is an idiopathic photodermatosis that affects the skin, as well as the labial and conjunctival mucosa in indigenous and mestizo populations of Latin America. It starts predominantly in childhood, has a chronic course, and is exacerbated with solar exposure. Little is known of its pathophysiology, including the known mechanisms of the participation of HLA-DR4 and an abnormal immunologic response with increase of T CD4+ lymphocytes. The presence of IgE, eosinophils, and mast cells suggests that it is a hypersensitivity reaction (likely type IVa or b). The diagnosis is clinical, and the presence of lymphoid follicles in the mucosal histopathologic study of mucosa is pathognomonic. The best available treatment to date is thalidomide, despite its secondary effects.

  11. Demonstration of prominent actin filaments in the root columella

    NASA Technical Reports Server (NTRS)

    Collings, D. A.; Zsuppan, G.; Allen, N. S.; Blancaflor, E. B.; Brown, C. S. (Principal Investigator)

    2001-01-01

    The distribution of actin filaments within the gravity-sensing columella cells of plant roots remains poorly understood, with studies over numerous years providing inconsistent descriptions of actin organization in these cells. This uncertainty in actin organization, and thus in actin's role in graviperception and gravisignaling, has led us to investigate actin arrangements in the columella cells of Zea mays L., Medicago truncatula Gaertn., Linum usitatissiilium L. and Nicotianla benthamiana Domin. Actin organization was examined using a combination of optimized immunofluorescence techniques, and an improved fluorochrome-conjugated phalloidin labeling method reliant on 3-maleimidobenzoyl-N-hydroxy-succinimide ester (MBS) cross-linking combined with glycerol permeabilization. Confocal microscopy of root sections labeled with anti-actin antibodies revealed patterns suggestive of actin throughout the columella region. These patterns included short and fragmented actin bundles, fluorescent rings around amyloplasts and intense fluorescence originating from the nucleus. Additionally, confocal microscopy of MBS-stabilized and Alexa Fluor-phalloidin-labeled root sections revealed a previously undetected state of actin organization in the columella. Discrete actin structures surrounded the amyloplasts and prominent actin cables radiated from the nuclear surface toward the cell periphery. Furthermore, the cortex of the columella cells contained fine actin bundles (or single filaments) that had a predominant transverse orientation. We also used confocal microscopy of plant roots expressing endoplasmic reticulum (ER)-targeted green fluorescent protein to demonstrate rapid ER movements within the columella cells, suggesting that the imaged actin network is functional. The successful identification of discrete actin structures in the root columella cells forms the perception and signaling.

  12. Superconducting Cable

    DOEpatents

    Hughey, Raburn L.; Sinha, Uday K.; Reece, David S.; Muller, Albert C.

    2005-07-22

    In order to provide a flexible oxide superconducting cable which is reduced in AC loss, tape-shaped superconducting wires covered with a stabilizing metal are wound on a flexible former. The superconducting wires are preferably laid on the former at a bending strain of not more than 0.2%. In laying on the former, a number of tape-shaped superconducting wires are laid on a core member in a side-by-side manner, to form a first layer. A prescribed number of tape-shaped superconducting wires are laid on top of the first layer in a side-by-side manner, to form a second layer. The former may be made of a metal, plastic, reinforced plastic, polymer, or a composite and provides flexibility to the superconducting wires and the cable formed therewith.

  13. Superconducting Cable

    DOEpatents

    Hughey, Raburn L.; Sinha, Uday K.; Reece, David S.; Muller, Albert C.

    2005-03-08

    In order to provide a flexible oxide superconducting cable which is reduced in AC loss, tape-shaped superconducting wires covered with a stabilizing metal are wound on a flexible former. The superconducting wires are preferably laid on the former at a bending strain of not more than 0.2%. In laying on the former, a number of tape-shaped superconducting wires are laid on a core member in a side-by-side manner, to form a first layer. A prescribed number of tape-shaped superconducting wires are laid on top of the first layer in a side-by-side manner, to form a second layer. The former may be made of a metal, plastic, reinforced plastic, polymer, or a composite and provides flexibility to the superconducting wires and the cable formed therewith.

  14. Architecture and Connectivity Govern Actin Network Contractility.

    PubMed

    Ennomani, Hajer; Letort, Gaëlle; Guérin, Christophe; Martiel, Jean-Louis; Cao, Wenxiang; Nédélec, François; De La Cruz, Enrique M; Théry, Manuel; Blanchoin, Laurent

    2016-03-07

    Actomyosin contractility plays a central role in a wide range of cellular processes, including the establishment of cell polarity, cell migration, tissue integrity, and morphogenesis during development. The contractile response is variable and depends on actomyosin network architecture and biochemical composition. To determine how this coupling regulates actomyosin-driven contraction, we used a micropatterning method that enables the spatial control of actin assembly. We generated a variety of actin templates and measured how defined actin structures respond to myosin-induced forces. We found that the same actin filament crosslinkers either enhance or inhibit the contractility of a network, depending on the organization of actin within the network. Numerical simulations unified the roles of actin filament branching and crosslinking during actomyosin contraction. Specifically, we introduce the concept of "network connectivity" and show that the contractions of distinct actin architectures are described by the same master curve when considering their degree of connectivity. This makes it possible to predict the dynamic response of defined actin structures to transient changes in connectivity. We propose that, depending on the connectivity and the architecture, network contraction is dominated by either sarcomeric-like or buckling mechanisms. More generally, this study reveals how actin network contractility depends on its architecture under a defined set of biochemical conditions.

  15. Regulation of Sodium Channel Activity by Capping of Actin Filaments

    PubMed Central

    Shumilina, Ekaterina V.; Negulyaev, Yuri A.; Morachevskaya, Elena A.; Hinssen, Horst; Khaitlina, Sofia Yu

    2003-01-01

    Ion transport in various tissues can be regulated by the cortical actin cytoskeleton. Specifically, involvement of actin dynamics in the regulation of nonvoltage-gated sodium channels has been shown. Herein, inside-out patch clamp experiments were performed to study the effect of the heterodimeric actin capping protein CapZ on sodium channel regulation in leukemia K562 cells. The channels were activated by cytochalasin-induced disruption of actin filaments and inactivated by G-actin under ionic conditions promoting rapid actin polymerization. CapZ had no direct effect on channel activity. However, being added together with G-actin, CapZ prevented actin-induced channel inactivation, and this effect occurred at CapZ/actin molar ratios from 1:5 to 1:100. When actin was allowed to polymerize at the plasma membrane to induce partial channel inactivation, subsequent addition of CapZ restored the channel activity. These results can be explained by CapZ-induced inhibition of further assembly of actin filaments at the plasma membrane due to the modification of actin dynamics by CapZ. No effect on the channel activity was observed in response to F-actin, confirming that the mechanism of channel inactivation does not involve interaction of the channel with preformed filaments. Our data show that actin-capping protein can participate in the cytoskeleton-associated regulation of sodium transport in nonexcitable cells. PMID:12686620

  16. CABLE CONNECTOR

    DOEpatents

    Caller, J.M.

    1962-05-01

    An electrical connector is designed for utilization in connection with either round or flat coaxial cables. The connector comprises a bayonet-type coupling arrangement with a splined movable locking sleeve adapted to lock together components of the connector. A compression spring is attached to one of the connector components and functions to forcibly separate mating components when the locking sleeve is in an unlocked condition so as to minimize the possibility of leaving the conductors electrically coupled. (AEC)

  17. Superconductor cable

    DOEpatents

    Smith, Jr., Darrell F.; Lake, Bill L.; Ballinger, Ronald G.

    1988-01-01

    A superconducting cable comprising an in-situ-formed type II superconductor, e.g. Nb.sub.3 Sn, in association with a stabilizing conductor both in heat transfer relationship with at least one passage adapted to carry liquified gaseous refrigerant. The conductor and said at least one passage are enclosed by a sheath comprising an alloy consisting essentially of about 49% nickel, about 4% chromium, about 3% niobium, about 1.4% titanium, about 1% aluminum, balance essentially iron.

  18. Actin Age Orchestrates Myosin-5 and Myosin-6 Runlengths

    PubMed Central

    Zimmermann, Dennis; Santos, Alicja; Kovar, David R.; Rock, Ronald S.

    2015-01-01

    Summary Unlike a static and immobile skeleton, the actin cytoskeleton is a highly dynamic network of filamentous actin (F-actin) polymers that continuously turn over. In addition to generating mechanical forces and sensing mechanical deformation, dynamic F-actin networks serve as cellular tracks for myosin motor traffic. However, much of our mechanistic understanding of processive myosins comes from in vitro studies where motility was studied on pre-assembled and artificially stabilized, static F-actin tracks. In this work, we examine the role of actin dynamics in single-molecule myosin motility using assembling F-actin and the two highly processive motors, myosin-5 and myosin-6. These two myosins have distinct functions in the cell and travel in opposite directions along actin filaments [1–3]. Myosin-5 walks towards the barbed ends of F-actin, traveling to sites of actin polymerization at the cell periphery [4]. Myosin-6 walks towards the pointed end of F-actin [5], traveling towards the cell center along older segments of the actin filament. We find that myosin-5 takes 1.3 to 1.5-fold longer runs on ADP•Pi (young) F-actin, while myosin-6 takes 1.7 to 3.6-fold longer runs along ADP (old) F-actin. These results suggest that conformational differences between ADP•Pi and ADP F-actin tailor these myosins to walk farther toward their preferred actin filament end. Taken together, these experiments define a new mechanism by which myosin traffic may sort to different F-actin networks depending on filament age. PMID:26190073

  19. New Insights into Mechanism and Regulation of Actin Capping Protein

    PubMed Central

    Cooper, John A.; Sept, David

    2008-01-01

    The heterodimeric actin capping protein, referred to here as “CP,” is an essential element of the actin cytoskeleton, binding to the barbed ends of actin filaments and regulating their polymerization. In vitro, CP has a critical role in the dendritic nucleation process of actin assembly mediated by Arp2/3 complex, and in vivo, CP is important for actin assembly and actin-based process of morphogenesis and differentiation. Recent studies have provided new insight into the mechanism of CP binding the barbed end, which raises new possibilities for the dynamics of CP and actin in cells. In addition, a number of molecules that bind and regulate CP have been discovered, suggesting new ideas for how CP may integrate into diverse processes of cell physiology. PMID:18544499

  20. Signalling Pathways Controlling Cellular Actin Organization.

    PubMed

    Steffen, Anika; Stradal, Theresia E B; Rottner, Klemens

    2017-01-01

    The actin cytoskeleton is essential for morphogenesis and virtually all types of cell shape changes. Reorganization is per definition driven by continuous disassembly and re-assembly of actin filaments, controlled by major, ubiquitously operating machines. These are specifically employed by the cell to tune its activities in accordance with respective environmental conditions or to satisfy specific needs.Here we sketch some fundamental signalling pathways established to contribute to the reorganization of specific actin structures at the plasma membrane. Rho-family GTPases are at the core of these pathways, and dissection of their precise contributions to actin reorganization in different cell types and tissues will thus continue to improve our understanding of these important signalling nodes. Furthermore, we will draw your attention to the emerging theme of actin reorganization on intracellular membranes, its functional relation to Rho-GTPase signalling, and its relevance for the exciting phenomenon autophagy.

  1. Actin network architecture can determine myosin motor activity.

    PubMed

    Reymann, Anne-Cécile; Boujemaa-Paterski, Rajaa; Martiel, Jean-Louis; Guérin, Christophe; Cao, Wenxiang; Chin, Harvey F; De La Cruz, Enrique M; Théry, Manuel; Blanchoin, Laurent

    2012-06-08

    The organization of actin filaments into higher-ordered structures governs eukaryotic cell shape and movement. Global actin network size and architecture are maintained in a dynamic steady state through regulated assembly and disassembly. Here, we used experimentally defined actin structures in vitro to investigate how the activity of myosin motors depends on network architecture. Direct visualization of filaments revealed myosin-induced actin network deformation. During this reorganization, myosins selectively contracted and disassembled antiparallel actin structures, while parallel actin bundles remained unaffected. The local distribution of nucleation sites and the resulting orientation of actin filaments appeared to regulate the scalability of the contraction process. This "orientation selection" mechanism for selective contraction and disassembly suggests how the dynamics of the cellular actin cytoskeleton can be spatially controlled by actomyosin contractility.

  2. Cortactin involvement in the keratinocyte growth factor and fibroblast growth factor 10 promotion of migration and cortical actin assembly in human keratinocytes

    SciTech Connect

    Ceccarelli, Simona; Cardinali, Giorgia; Aspite, Nicaela; Picardo, Mauro; Marchese, Cinzia; Torrisi, Maria Rosaria; Mancini, Patrizia . E-mail: patrizia.mancini@uniroma1.it

    2007-05-15

    Keratinocyte growth factor (KGF/FGF7) and fibroblast growth factor 10 (FGF10/KGF2) regulate keratinocyte proliferation and differentiation by binding to the tyrosine kinase KGF receptor (KGFR). KGF induces keratinocyte motility and cytoskeletal rearrangement, whereas a direct role of FGF10 on keratinocyte migration is not clearly established. Here we analyzed the motogenic activity of FGF10 and KGF on human keratinocytes. Migration assays and immunofluorescence of actin cytoskeleton revealed that FGF10 is less efficient than KGF in promoting migration and exerts a delayed effect in inducing lamellipodia and ruffles formation. Both growth factors promoted phosphorylation and subsequent membrane translocation of cortactin, an F-actin binding protein involved in cell migration; however, FGF10-induced cortactin phosphorylation was reduced, more transient and delayed with respect to that promoted by KGF. Cortactin phosphorylation induced by both growth factors was Src-dependent, while its membrane translocation and cell migration were blocked by either Src and PI3K inhibitors, suggesting that both pathways are involved in KGF- and FGF10-dependent motility. Furthermore, siRNA-mediated downregulation of cortactin inhibited KGF- and FGF10-induced migration. These results indicate that cortactin is involved in keratinocyte migration promoted by both KGF and FGF10.

  3. Dynamic reorganization of the actin cytoskeleton

    PubMed Central

    Gressin, Laurène; Théry, Manuel; Blanchoin, Laurent

    2015-01-01

    Cellular processes, including morphogenesis, polarization, and motility, rely on a variety of actin-based structures. Although the biochemical composition and filament organization of these structures are different, they often emerge from a common origin. This is possible because the actin structures are highly dynamic. Indeed, they assemble, grow, and disassemble in a time scale of a second to a minute. Therefore, the reorganization of a given actin structure can promote the formation of another. Here, we discuss such transitions and illustrate them with computer simulations. PMID:26989473

  4. Actin-Regulator Feedback Interactions during Endocytosis

    PubMed Central

    Wang, Xinxin; Galletta, Brian J.; Cooper, John A.; Carlsson, Anders E.

    2016-01-01

    Endocytosis mediated by clathrin, a cellular process by which cells internalize membrane receptors and their extracellular ligands, is an important component of cell signaling regulation. Actin polymerization is involved in endocytosis in varying degrees depending on the cellular context. In yeast, clathrin-mediated endocytosis requires a pulse of polymerized actin and its regulators, which recruit and activate the Arp2/3 complex. In this article, we seek to identify the main protein-protein interactions that 1) cause actin and its regulators to appear in pulses, and 2) determine the effects of key mutations and drug treatments on actin and regulator assembly. We perform a joint modeling/experimental study of actin and regulator dynamics during endocytosis in the budding yeast Saccharomyces cerevisiae. We treat both a stochastic model that grows an explicit three-dimensional actin network, and a simpler two-variable Fitzhugh-Nagumo type model. The models include a negative-feedback interaction of F-actin onto the Arp2/3 regulators. Both models explain the pulse time courses and the effects of interventions on actin polymerization: the surprising increase in the peak F-actin count caused by reduced regulator branching activity, the increase in F-actin resulting from slowing of actin disassembly, and the increased Arp2/3 regulator lifetime resulting from latrunculin treatment. In addition, they predict that decreases in the regulator branching activity lead to increases in accumulation of regulators, and we confirmed this prediction with experiments on yeast harboring mutations in the Arp2/3 regulators, using quantitative fluorescence microscopy. Our experimental measurements suggest that the regulators act quasi-independently, in the sense that accumulation of a particular regulator is most strongly affected by mutations of that regulator, as opposed to the others. PMID:27028652

  5. Cable Television Service; Cable Television Relay Service.

    ERIC Educational Resources Information Center

    Federal Register, 1972

    1972-01-01

    The rules and regulations of the Federal Communications Commission (FCC) concerning cable television service and cable relay service are presented along with the comments of the National Cable Television Association, the National Association of Broadcasters, the Association of Maximum Service Telecasters, and a major group of program suppliers.…

  6. Direct Observation of Tropomyosin Binding to Actin Filaments

    PubMed Central

    Schmidt, William M.; Lehman, William; Moore, Jeffrey R.

    2015-01-01

    Tropomyosin is an elongated α-helical coiled-coil that binds to seven consecutive actin subunits along the long-pitch helix of actin filaments. Once bound, tropomyosin polymerizes end-to-end and both stabilizes F-actin and regulates access of various actin binding proteins including myosin in muscle and non-muscle cells. Single tropomyosin molecules bind weakly to F-actin with millimolar Kd, whereas the end-to-end linked tropomyosin associates with about a one thousand-fold greater affinity. Despite years of study, the assembly mechanism of tropomyosin onto actin filaments remains unclear. In the current study, we used total internal reflection fluorescence (TIRF) microscopy to directly monitor the cooperative binding of fluorescently labeled tropomyosin molecules to phalloidin-stabilized actin filaments. We find that tropomyosin molecules assemble from multiple growth sites following random low affinity binding of single molecules to actin. As the length of the tropomyosin chain increases, the probability of detachment decreases, which leads to further chain growth. Tropomyosin chain extension is linearly dependent on tropomyosin concentration, occurring at approximately 100 monomers/(μM*s). The random tropomyosin binding to F-actin leads to discontinuous end-to-end association where gaps in the chain continuity smaller than the required seven sequential actin monomers are available. Direct observation of tropomyosin detachment revealed the number of gaps in actin-bound tropomyosin, the time course of gap annealing, and the eventual filament saturation process. PMID:26033920

  7. Actomyosin-dependent formation of the mechanosensitive talin-vinculin complex reinforces actin anchoring

    NASA Astrophysics Data System (ADS)

    Ciobanasu, Corina; Faivre, Bruno; Le Clainche, Christophe

    2014-01-01

    The force generated by the actomyosin cytoskeleton controls focal adhesion dynamics during cell migration. This process is thought to involve the mechanical unfolding of talin to expose cryptic vinculin-binding sites. However, the ability of the actomyosin cytoskeleton to directly control the formation of a talin-vinculin complex and the resulting activity of the complex are not known. Here we develop a microscopy assay with pure proteins in which the self-assembly of actomyosin cables controls the association of vinculin to a talin-micropatterned surface in a reversible manner. Quantifications indicate that talin refolding is limited by vinculin dissociation and modulated by the actomyosin network stability. Finally, we show that the activation of vinculin by stretched talin induces a positive feedback that reinforces the actin-talin-vinculin association. This in vitro reconstitution reveals the mechanism by which a key molecular switch senses and controls the connection between adhesion complexes and the actomyosin cytoskeleton.

  8. A dynamic formin-dependent deep F-actin network in axons

    PubMed Central

    Ganguly, Archan; Tang, Yong; Wang, Lina; Ladt, Kelsey; Loi, Jonathan; Dargent, Bénédicte; Leterrier, Christophe

    2015-01-01

    Although actin at neuronal growth cones is well-studied, much less is known about actin organization and dynamics along axon shafts and presynaptic boutons. Using probes that selectively label filamentous-actin (F-actin), we found focal “actin hotspots” along axons—spaced ∼3–4 µm apart—where actin undergoes continuous assembly/disassembly. These foci are a nidus for vigorous actin polymerization, generating long filaments spurting bidirectionally along axons—a phenomenon we call “actin trails.” Super-resolution microscopy reveals intra-axonal deep actin filaments in addition to the subplasmalemmal “actin rings” described recently. F-actin hotspots colocalize with stationary axonal endosomes, and blocking vesicle transport diminishes the actin trails, suggesting mechanistic links between vesicles and F-actin kinetics. Actin trails are formin—but not Arp2/3—dependent and help enrich actin at presynaptic boutons. Finally, formin inhibition dramatically disrupts synaptic recycling. Collectively, available data suggest a two-tier F-actin organization in axons, with stable “actin rings” providing mechanical support to the plasma membrane and dynamic "actin trails" generating a flexible cytoskeletal network with putative physiological roles. PMID:26216902

  9. Flat-cable fabrication

    NASA Astrophysics Data System (ADS)

    Groot, K. J.

    1982-11-01

    Processes, environment, designs, and materials were reviewed to lower the attrition rate and improve the manufacturing ability of flat, flexible cables. Attrition caused by foreign material, damage, and dents was lowered. A new termination was developed for two cables. An alternative design for Kapton insulated cables reduced notch sensitivity. Alternative methods of cable manufacturing and inspection are investigated.

  10. Cable-splice detector

    NASA Technical Reports Server (NTRS)

    Lee, R. D.; Iufer, E. J.; Giovannetti, A.

    1980-01-01

    Detector has possible uses in aerial cable-car systems, equipment handling in mines, boreholes, and undersea operations, and other applications where moving steel cable must be measured, monitored, or controlled. Detector consists of Hall-effect magnetic sensor located close to cable. Magnetic markings on cable are converted to electrical signals. Signals are filtered, amplified, and can actuate alarm.

  11. Cable-Twisting Machine

    NASA Technical Reports Server (NTRS)

    Kurnett, S.

    1982-01-01

    New cable-twisting machine is smaller and faster than many production units. Is useful mainly in production of short-run special cables. Already-twisted cable can be fed along axis of machine. Faster operation than typical industrial cable-twisting machines possible by using smaller spools of wire.

  12. Cable Tensiometer for Aircraft

    NASA Technical Reports Server (NTRS)

    Nunnelee, Mark (Inventor)

    2008-01-01

    The invention is a cable tensiometer that can be used on aircraft for real-time, in-flight cable tension measurements. The invention can be used on any aircraft cables with high precision. The invention is extremely light-weight, hangs on the cable being tested and uses a dual bending beam design with a high mill-volt output to determine tension.

  13. Mechanically Induced Actin-mediated Rocketing of Phagosomes

    PubMed Central

    Müller-Taubenberger, Annette; Anderson, Kurt I.; Engel, Ulrike; Gerisch, Günther

    2006-01-01

    Actin polymerization can be induced in Dictyostelium by compressing the cells to bring phagosomes filled with large particles into contact with the plasma membrane. Asymmetric actin assembly results in rocketing movement of the phagosomes. We show that the compression-induced assembly of actin at the cytoplasmic face of the plasma membrane involves the Arp2/3 complex. We also identify two other proteins associated with the mechanically induced actin assembly. The class I myosin MyoB accumulates at the plasma membrane–phagosome interface early during the initiation of the response, and coronin is recruited as the actin filaments are disassembling. The forces generated by rocketing phagosomes are sufficient to push the entire microtubule apparatus forward and to dislocate the nucleus. PMID:16971511

  14. Interactions among a Fimbrin, a Capping Protein, and an Actin-depolymerizing Factor in Organization of the Fission Yeast Actin Cytoskeleton

    PubMed Central

    Nakano, Kentaro; Satoh, Kazuomi; Morimatsu, Akeshi; Ohnuma, Masaaki; Mabuchi, Issei

    2001-01-01

    We report studies of the fission yeast fimbrin-like protein Fim1, which contains two EF-hand domains and two actin-binding domains (ABD1 and ABD2). Fim1 is a component of both F-actin patches and the F-actin ring, but not of F-actin cables. Fim1 cross-links F-actin in vitro, but a Fim1 protein lacking either EF-hand domains (Fim1A12) or both the EF-hand domains and ABD1 (Fim1A2) has no actin cross-linking activity. Overexpression of Fim1 induced the formation of F-actin patches throughout the cell cortex, whereas the F-actin patches disappear in cells overexpressing Fim1A12 or Fim1A2. Thus, the actin cross-linking activity of Fim1 is probably important for the formation of F-actin patches. The overexpression of Fim1 also excluded the actin-depolymerizing factor Adf1 from the F-actin patches and inhibited the turnover of actin in these structures. Thus, Fim1 may function in stabilizing the F-actin patches. We also isolated the gene encoding Acp1, a subunit of the heterodimeric F-actin capping protein. fim1 acp1 double null cells showed more severe defects in the organization of the actin cytoskeleton than those seen in each single mutant. Thus, Fim1 and Acp1 may function in a similar manner in the organization of the actin cytoskeleton. Finally, genetic studies suggested that Fim1 may function in cytokinesis in cooperation with Cdc15 (PSTPIP) and Rng2 (IQGAP), respectively. PMID:11694585

  15. Actin-dependent propulsion of endosomes and lysosomes byrecruitment of n-wasp

    SciTech Connect

    Taunton J; Rowning BA; Coughlin ML; Wu M; Moon RT; Mitchison TJ; Larabell CA

    2000-02-07

    We examined the spatial and temporal control of actin assembly in living Xenopus eggs. Within minutes of egg activation,dynamic actin-rich comet tails appeared on a subset of cytoplasmic vesicles that were enriched in protein kinase C (PKC), causing the vesicles to move through the cytoplasm. Actin comet tail formation in vivo was stimulated by the PKC activator phorbol myristate acetate (PMA),and this process could be reconstituted in a cell-free system. We used this system to define the characteristics that distinguish vesicles associated with actin comet tails from other vesicles in the extract. We found that the protein, N-WASP, was recruited to the surface of every vesicle associated with an actin comet tail, suggesting that vesicle movement results from actin assembly nucleated by the Arp2/3 complex, the immediate downstream target of N-WASP, The motile vesicles accumulated the dye acridine orange, a marker for endosomes and lysosomes. Furthermore, vesicles associated with actin comet tails had the morphological features of multivesicular endosomes as revealed by electron microscopy. Endosomes and lysosomes from mammalian cells preferentially nucleated actin assembly and moved in the Xenopus egg extract system. These results define endosomes and lysosomes as recruitment sites for the actin nucleation machinery and demonstrate that actin assembly contributes to organelle movement. Conversely, by nucleating actin assembly, intracellular membranes may contribute to the dynamic organization of the actin cytoskeleton.

  16. Actin and Septin Ultrastructures at the Budding Yeast Cell Cortex

    PubMed Central

    Rodal, Avital A.; Kozubowski, Lukasz; Goode, Bruce L.; Drubin, David G.; Hartwig, John H.

    2005-01-01

    Budding yeast has been a powerful model organism for studies of the roles of actin in endocytosis and septins in cell division and in signaling. However, the depth of mechanistic understanding that can be obtained from such studies has been severely hindered by a lack of ultrastructural information about how actin and septins are organized at the cell cortex. To address this problem, we developed rapid-freeze and deep-etch techniques to image the yeast cell cortex in spheroplasted cells at high resolution. The cortical actin cytoskeleton assembles into conical or mound-like structures composed of short, cross-linked filaments. The Arp2/3 complex localizes near the apex of these structures, suggesting that actin patch assembly may be initiated from the apex. Mutants in cortical actin patch components with defined defects in endocytosis disrupted different stages of cortical actin patch assembly. Based on these results, we propose a model for actin function during endocytosis. In addition to actin structures, we found that septin-containing filaments assemble into two kinds of higher order structures at the cell cortex: rings and ordered gauzes. These images provide the first high-resolution views of septin organization in cells. PMID:15525671

  17. Why is Actin Patchy?

    NASA Astrophysics Data System (ADS)

    Carlsson, Anders

    2009-03-01

    The intracellular protein actin, by reversibly polymerizing into filaments, generates forces for motion and shape changes of many types of biological cells. Fluorescence imaging studies show that actin often occurs in the form of localized patches of size roughly one micrometer at the cell membrane. Patch formation is most prevalent when the free-actin concentration is low. I investigate possible mechanisms for the formation of actin patches by numerically simulating the ``dendritic nucleation'' model of actin network growth. The simulations include filament growth, capping, branching, severing, and debranching. The attachment of membrane-bound activators to actin filaments, and subsequent membrane diffusion of unattached activators, are also included. It is found that as the actin concentration increases from zero, the actin occurs in patches at lower actin concentrations, and the size of the patches increases with increasing actin concentration. At a critical value of the actin concentration, the system undergoes a transition to complete coverage. The results are interpreted within the framework of reaction-diffusion equations in two dimensions.

  18. Resemblance of actin-binding protein/actin gels to covalently crosslinked networks

    NASA Astrophysics Data System (ADS)

    Janmey, Paul A.; Hvidt, Søren; Lamb, Jennifer; Stossel, Thomas P.

    1990-05-01

    THE maintainance of the shape of cells is often due to their surface elasticity, which arises mainly from an actin-rich cytoplasmic cortex1,2. On locomotion, phagocytosis or fission, however, these cells become partially fluid-like. The finding of proteins that can bind to actin and control the assembly of, or crosslink, actin filaments, and of intracellular messages that regulate the activities of some of these actin-binding proteins, indicates that such 'gel sol' transformations result from the rearrangement of cortical actin-rich networks3. Alternatively, on the basis of a study of the mechanical properties of mixtures of actin filaments and an Acanthamoeba actin-binding protein, α-actinin, it has been proposed that these transformations can be accounted for by rapid exchange of crosslinks between actin filaments4: the cortical network would be solid when the deformation rate is greater than the rate of crosslink exchange, but would deform or 'creep' when deformation is slow enough to permit crosslinker molecules to rearrange. Here we report, however, that mixtures of actin filaments and actin-binding protein (ABP), an actin crosslinking protein of many higher eukaryotes, form gels Theologically equivalent to covalently crosslinked networks. These gels do not creep in response to applied stress on a time scale compatible with most cell-surface movements. These findings support a more complex and controlled mechanism underlying the dynamic mechanical properties of cortical cytoplasm, and can explain why cells do not collapse under the constant shear forces that often exist in tissues.

  19. Marine cable location system

    SciTech Connect

    Zachariadis, R.G.

    1984-05-01

    An acoustic positioning system locates a marine cable at an exploration site, such cable employing a plurality of hydrophones at spaced-apart positions along the cable. A marine vessel measures water depth to the cable as the vessel passes over the cable and interrogates the hydrophones with sonar pulses along a slant range as the vessel travels in a parallel and horizontally offset path to the cable. The location of the hydrophones is determined from the recordings of water depth and slant range.

  20. Cable load sensing device

    DOEpatents

    Beus, Michael J.; McCoy, William G.

    1998-01-01

    Apparatus for sensing the magnitude of a load on a cable as the cable is employed to support the load includes a beam structure clamped to the cable so that a length of the cable lies along the beam structure. A spacer associated with the beam structure forces a slight curvature in a portion of the length of cable under a cable "no-load" condition so that the portion of the length of cable is spaced from the beam structure to define a cable curved portion. A strain gauge circuit including strain gauges is secured to the beam structure by welding. As the cable is employed to support a load the load causes the cable curved portion to exert a force normal to the cable through the spacer and on the beam structure to deform the beam structure as the cable curved portion attempts to straighten under the load. As this deformation takes place, the resistance of the strain gauges is set to a value proportional to the magnitude of the normal strain on the beam structure during such deformation. The magnitude of the normal strain is manipulated in a control device to generate a value equal to the magnitude or weight of the load supported by the cable.

  1. Actin-mediated motion of meiotic chromosomes

    PubMed Central

    Koszul, R.; Kim, K. P.; Prentiss, M.; Kleckner, N.; Kameoka, S.

    2008-01-01

    Summary Chromosome movement is prominent during meiosis. Here, using a combination of in vitro and in vivo approaches, we elucidate the basis for dynamic mid-prophase chromosome movement in budding yeast. Diverse finding reveal a process in which, at the pachytene stage, individual telomere/nuclear envelope (NE) ensembles attach passively to, and then move in concert with, nucleus-hugging actin cables that are continuous with the global cytoskeletal actin network. Other chromosomes move in concert with lead chromosome(s). The same process, in modulated form, explains the zygotene "bouquet" configuration in which, immediately preceding pachytene, chromosome ends colocalize dynamically in a restricted region of the NE. Mechanical properties of the system and biological roles of mid-prophase movement for meiosis, including recombination, are discussed. PMID:18585353

  2. Cutting Edge Cable Management.

    ERIC Educational Resources Information Center

    Peach, Roger

    1997-01-01

    Describes how one school district was able to efficiently install fragile telecommunication cabling throughout its high school and save thousands of dollars. Discusses solutions to some common cable-management problems. (GR)

  3. Actin-Based Motility of Intracellular Microbial Pathogens

    PubMed Central

    Goldberg, Marcia B.

    2001-01-01

    A diverse group of intracellular microorganisms, including Listeria monocytogenes, Shigella spp., Rickettsia spp., and vaccinia virus, utilize actin-based motility to move within and spread between mammalian host cells. These organisms have in common a pathogenic life cycle that involves a stage within the cytoplasm of mammalian host cells. Within the cytoplasm of host cells, these organisms activate components of the cellular actin assembly machinery to induce the formation of actin tails on the microbial surface. The assembly of these actin tails provides force that propels the organisms through the cell cytoplasm to the cell periphery or into adjacent cells. Each of these organisms utilizes preexisting mammalian pathways of actin rearrangement to induce its own actin-based motility. Particularly remarkable is that while all of these microbes use the same or overlapping pathways, each intercepts the pathway at a different step. In addition, the microbial molecules involved are each distinctly different from the others. Taken together, these observations suggest that each of these microbes separately and convergently evolved a mechanism to utilize the cellular actin assembly machinery. The current understanding of the molecular mechanisms of microbial actin-based motility is the subject of this review. PMID:11729265

  4. Vertex Detector Cable Considerations

    SciTech Connect

    Cooper, William E.; /Fermilab

    2009-02-01

    Vertex detector cable requirements are considered within the context of the SiD concept. Cable material should be limited so that the number of radiation lengths represented is consistent with the material budget. In order to take advantage of the proposed accelerator beam structure and allow cooling by flow of dry gas, 'pulsed power' is assumed. Potential approaches to power distribution, cable paths, and cable design for operation in a 5 T magnetic field are described.

  5. F-actin dismantling through a Redox-driven synergy between Mical and cofilin

    PubMed Central

    Grintsevich, Elena E.; Yesilyurt, Hunkar Gizem; Rich, Shannon K.; Hung, Ruei-Jiun; Terman, Jonathan R.; Reisler, Emil

    2016-01-01

    Numerous cellular functions depend on actin filament (F-actin) disassembly. The best-characterized disassembly proteins, the ADF/cofilins/twinstar, sever filaments and recycle monomers to promote actin assembly. Cofilin is also a relatively weak actin disassembler, posing questions about mechanisms of cellular F-actin destabilization. Here we uncover a key link to targeted F-actin disassembly by finding that F-actin is efficiently dismantled through a post-translational-mediated synergism between cofilin and the actin-oxidizing enzyme Mical. We find that Mical-mediated oxidation of actin improves cofilin binding to filaments, where their combined effect dramatically accelerates F-actin disassembly compared to either effector alone. This synergism is also necessary and sufficient for F-actin disassembly in vivo, magnifying the effects of both Mical and cofilin on cellular remodeling, axon guidance, and Semaphorin/Plexin repulsion. Mical and cofilin, therefore, form a Redox-dependent synergistic pair that promotes F-actin instability by rapidly dismantling F-actin and generating post-translationally modified actin that has altered assembly properties. PMID:27454820

  6. Chloroplast actin filaments organize meshwork on the photorelocated chloroplasts in the moss Physcomitrella patens.

    PubMed

    Yamashita, Hiroko; Sato, Yoshikatsu; Kanegae, Takeshi; Kagawa, Takatoshi; Wada, Masamitsu; Kadota, Akeo

    2011-02-01

    Cytoskeleton dynamics during phototropin-dependent chloroplast photorelocation movement was analyzed in protonemal cells of actin- and microtubule-visualized lines of Physcomitrella patens expressing GFP- or tdTomato-talin and GFP-tubulin. Using newly developed epi- and trans-microbeam irradiation systems that permit fluorescence observation of the cell under blue microbeam irradiation inducing chloroplast relocation, it was revealed that meshwork of actin filaments formed at the chloroplast-accumulating area both in the avoidance and accumulation movements. The structure disappeared soon when blue microbeam was turned off, and it was not induced under red microbeam irradiation that did not evoke chloroplast relocation movement. In contrast, no apparent change in microtubule organization was detected during the movements. The actin meshwork was composed of short actin filaments distinct from the cytoplasmic long actin cables and was present between the chloroplasts and plasma membrane. The short actin filaments emerged from around the chloroplast periphery towards the center of chloroplast. Showing highly dynamic behavior, the chloroplast actin filaments (cp-actin filaments) were rapidly organized into meshwork on the chloroplast surface facing plasma membrane. The actin filament configuration on a chloroplast led to the formation of actin meshwork area in the cell as the chloroplasts arrived at and occupied the area. After establishment of the meshwork, cp-actin filaments were still highly dynamic, showing appearance, disappearance, severing and bundling of filaments. These results indicate that the cp-actin filaments have significant roles in the chloroplast movement and positioning in the cell.

  7. 30 CFR 75.907 - Design of trailing cables for medium-voltage circuits.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... circuits. Trailing cables for medium-voltage circuits shall include grounding conductors, a ground check conductor, and grounded metallic shields around each power conductor or a ground metallic shield over the assembly, except that on equipment employing cable reels, cables without shields may be used if...

  8. 30 CFR 75.907 - Design of trailing cables for medium-voltage circuits.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... circuits. Trailing cables for medium-voltage circuits shall include grounding conductors, a ground check conductor, and grounded metallic shields around each power conductor or a ground metallic shield over the assembly, except that on equipment employing cable reels, cables without shields may be used if...

  9. Dynamic actin cycling through mitochondrial subpopulations locally regulates the fission–fusion balance within mitochondrial networks

    PubMed Central

    Moore, Andrew S.; Wong, Yvette C.; Simpson, Cory L.; Holzbaur, Erika L. F.

    2016-01-01

    Mitochondria form interconnected networks that dynamically remodel in response to cellular needs. Using live-cell imaging, we investigate the role of the actin cytoskeleton in regulating mitochondrial fission and fusion. We identify cycling of actin filaments onto and off of subsets of cellular mitochondria. The association of actin filaments with mitochondrial subpopulations is transient; actin quickly disassembles, then reassembles around a distinct subpopulation, efficiently cycling through all cellular mitochondria within 14 min. The focal assembly of actin induces local, Drp1-dependent fragmentation of the mitochondrial network. On actin disassembly, fragmented mitochondria undergo rapid fusion, leading to regional recovery of the tubular mitochondrial network. Cycling requires dynamic actin polymerization and is blocked by inhibitors of both Arp2/3 and formins. We propose that cyclic assembly of actin onto mitochondria modulates the fission/fusion balance, promotes network remodelling and content mixing, and thus may serve as an essential mechanism regulating mitochondrial network homeostasis. PMID:27686185

  10. Cable Television: Franchising Considerations.

    ERIC Educational Resources Information Center

    Baer, Walter S.; And Others

    This volume is a comprehensive reference guide to cable television technology and issues of planning, franchising, and regulating a cable system. It is intended for local government officials and citizens concerned with the development of cable television systems in their communities, as well as for college and university classes in…

  11. Cables and fire hazards

    NASA Technical Reports Server (NTRS)

    Zanelli, C.; Philbrick, S.; Beretta, G.

    1986-01-01

    Besides describing the experiments conducted to develop a nonflammable cable, this article discusses several considerations regarding other hazards which might result from cable fires, particularly the toxicity and opacity of the fumes emitted by the burning cable. In addition, this article examines the effects of using the Oxygen Index as a gauge of quality control during manufacture.

  12. Modeling the dynamics of dendritic actin waves in living cells

    NASA Astrophysics Data System (ADS)

    Wasnik, Vaibhav; Mukhopadhyay, Ranjan

    2014-11-01

    The actin cytoskeleton in living cells exhibits a high degree of capacity for dynamic self-organization. Recent experiments have observed propagating actin waves in Dictyostelium cells recovering from complete depolymerization of their actin cytoskeleton. The propagation of these waves appear to be dependent on a programmed recruitment of a few proteins that control actin assembly and disassembly. Such waves also arise spontaneously along the plasma membrane of the cell, and it has been suggested that actin waves enable the cell to scan a surface for particles to engulf. Based on known molecular components involved in wave propagation, we present and study a minimal reaction-diffusion model for actin wave production observed in recovering cells.

  13. Sensing actin dynamics: Structural basis for G-actin-sensitive nuclear import of MAL

    SciTech Connect

    Hirano, Hidemi; Matsuura, Yoshiyuki

    2011-10-22

    Highlights: {yields} MAL has a bipartite NLS that binds to Imp{alpha} in an extended conformation. {yields} Mutational analyses verified the functional significance of MAL-Imp{alpha} interactions. {yields} Induced folding and NLS-masking by G-actins inhibit nuclear import of MAL. -- Abstract: The coordination of cytoskeletal actin dynamics with gene expression reprogramming is emerging as a crucial mechanism to control diverse cellular processes, including cell migration, differentiation and neuronal circuit assembly. The actin-binding transcriptional coactivator MAL (also known as MRTF-A/MKL1/BSAC) senses G-actin concentration and transduces Rho GTPase signals to serum response factor (SRF). MAL rapidly shuttles between the cytoplasm and the nucleus in unstimulated cells but Rho-induced depletion of G-actin leads to MAL nuclear accumulation and activation of transcription of SRF:MAL-target genes. Although the molecular and structural basis of actin-regulated nucleocytoplasmic shuttling of MAL is not understood fully, it is proposed that nuclear import of MAL is mediated by importin {alpha}/{beta} heterodimer, and that G-actin competes with importin {alpha}/{beta} for the binding to MAL. Here we present structural, biochemical and cell biological evidence that MAL has a classical bipartite nuclear localization signal (NLS) in the N-terminal 'RPEL' domain containing Arg-Pro-X-X-X-Glu-Leu (RPEL) motifs. The NLS residues of MAL adopt an extended conformation and bind along the surface groove of importin-{alpha}, interacting with the major- and minor-NLS binding sites. We also present a crystal structure of wild-type MAL RPEL domain in complex with five G-actins. Comparison of the importin-{alpha}- and actin-complexes revealed that the binding of G-actins to MAL is associated with folding of NLS residues into a helical conformation that is inappropriate for importin-{alpha} recognition.

  14. Tropomyosin - master regulator of actin filament function in the cytoskeleton.

    PubMed

    Gunning, Peter W; Hardeman, Edna C; Lappalainen, Pekka; Mulvihill, Daniel P

    2015-08-15

    Tropomyosin (Tpm) isoforms are the master regulators of the functions of individual actin filaments in fungi and metazoans. Tpms are coiled-coil parallel dimers that form a head-to-tail polymer along the length of actin filaments. Yeast only has two Tpm isoforms, whereas mammals have over 40. Each cytoskeletal actin filament contains a homopolymer of Tpm homodimers, resulting in a filament of uniform Tpm composition along its length. Evidence for this 'master regulator' role is based on four core sets of observation. First, spatially and functionally distinct actin filaments contain different Tpm isoforms, and recent data suggest that members of the formin family of actin filament nucleators can specify which Tpm isoform is added to the growing actin filament. Second, Tpms regulate whole-organism physiology in terms of morphogenesis, cell proliferation, vesicle trafficking, biomechanics, glucose metabolism and organ size in an isoform-specific manner. Third, Tpms achieve these functional outputs by regulating the interaction of actin filaments with myosin motors and actin-binding proteins in an isoform-specific manner. Last, the assembly of complex structures, such as stress fibers and podosomes involves the collaboration of multiple types of actin filament specified by their Tpm composition. This allows the cell to specify actin filament function in time and space by simply specifying their Tpm isoform composition.

  15. 3D actin network centerline extraction with multiple active contours.

    PubMed

    Xu, Ting; Vavylonis, Dimitrios; Huang, Xiaolei

    2014-02-01

    Fluorescence microscopy is frequently used to study two and three dimensional network structures formed by cytoskeletal polymer fibers such as actin filaments and actin cables. While these cytoskeletal structures are often dilute enough to allow imaging of individual filaments or bundles of them, quantitative analysis of these images is challenging. To facilitate quantitative, reproducible and objective analysis of the image data, we propose a semi-automated method to extract actin networks and retrieve their topology in 3D. Our method uses multiple Stretching Open Active Contours (SOACs) that are automatically initialized at image intensity ridges and then evolve along the centerlines of filaments in the network. SOACs can merge, stop at junctions, and reconfigure with others to allow smooth crossing at junctions of filaments. The proposed approach is generally applicable to images of curvilinear networks with low SNR. We demonstrate its potential by extracting the centerlines of synthetic meshwork images, actin networks in 2D Total Internal Reflection Fluorescence Microscopy images, and 3D actin cable meshworks of live fission yeast cells imaged by spinning disk confocal microscopy. Quantitative evaluation of the method using synthetic images shows that for images with SNR above 5.0, the average vertex error measured by the distance between our result and ground truth is 1 voxel, and the average Hausdorff distance is below 10 voxels.

  16. DC Cable for Railway

    NASA Astrophysics Data System (ADS)

    Tomita, Masaru

    The development of a superconducting cable for railways has commenced, assuming that a DC transmission cable will be used for electric trains. The cable has been fabricated based on the results of current testing of a superconducting wire, and various evaluation tests have been performed to determine the characteristics of the cable. A superconducting transmission cable having zero electrical resistance and suitable for railway use is expected to enhance regeneration efficiency, reduce power losses, achieve load leveling and integration of sub-stations, and reduce rail potential.

  17. The yeast gene, MDM20, is necessary for mitochondrial inheritance and organization of the actin cytoskeleton.

    PubMed

    Hermann, G J; King, E J; Shaw, J M

    1997-04-07

    In Saccharomyces cerevisiae, the growing bud inherits a portion of the mitochondrial network from the mother cell soon after it emerges. Although this polarized transport of mitochondria is thought to require functions of the cytoskeleton, there are conflicting reports concerning the nature of the cytoskeletal element involved. Here we report the isolation of a yeast mutant, mdm20, in which both mitochondrial inheritance and actin cables (bundles of actin filaments) are disrupted. The MDM20 gene encodes a 93-kD polypeptide with no homology to other characterized proteins. Extra copies of TPM1, a gene encoding the actin filament-binding protein tropomyosin, suppress mitochondrial inheritance defects and partially restore actin cables in mdm20 delta cells. Synthetic lethality is also observed between mdm20 and tpm1 mutant strains. Overexpression of a second yeast tropomyosin, Tpm2p, rescues mutant phenotypes in the mdm20 strain to a lesser extent. Together, these results provide compelling evidence that mitochondrial inheritance in yeast is an actin-mediated process. MDM20 and TPM1 also exhibit the same pattern of genetic interactions; mutations in MDM20 are synthetically lethal with mutations in BEM2 and MYO2 but not SAC6. Although MDM20 and TPM1 are both required for the formation and/or stabilization of actin cables, mutations in these genes disrupt mitochondrial inheritance and nuclear segregation to different extents. Thus, Mdm20p and Tpm1p may act in vivo to establish molecular and functional heterogeneity of the actin cytoskeleton.

  18. Use of a fusion protein between GFP and an actin-binding domain to visualize transient filamentous-actin structures.

    PubMed

    Pang, K M; Lee, E; Knecht, D A

    1998-03-26

    Many important processes in eukaryotic cells involve changes in the quantity, location and the organization of actin filaments [1] [2] [3]. We have been able to visualize these changes in live cells using a fusion protein (GFP-ABD) comprising the green fluorescent protein (GFP) of Aequorea victoria and the 25 kDa highly conserved actin-binding domain (ABD) from the amino terminus of the actin cross-linking protein ABP-120 [4]. In live cells of the soil amoeba Dictyostelium that were expressing GFP-ABD, the three-dimensional architecture of the actin cortex was clearly visualized. The pattern of GFP-ABD fluorescence in these cells coincided with that of rhodamine-phalloidin, indicating that GFP-ABD specifically binds filamentous (F) actin. On the ventral surface of non-polarized vegetative cells, a broad ring of F actin periodically assembled and contracted, whereas in polarized cells there were transient punctate F-actin structures; cells cycled between the polarized and non-polarized morphologies. During the formation of pseudopods, an increase in fluorescence intensity coincided with the initial outward deformation of the membrane. This is consistent with the models of pseudopod extension that predict an increase in the local density of actin filaments. In conclusion, GFP-ABD specifically binds F actin and allows the visualization of F-actin dynamics and cellular behavior simultaneously.

  19. Global treadmilling coordinates actin turnover and controls the size of actin networks.

    PubMed

    Carlier, Marie-France; Shekhar, Shashank

    2017-03-01

    Various cellular processes (including cell motility) are driven by the regulated, polarized assembly of actin filaments into distinct force-producing arrays of defined size and architecture. Branched, linear, contractile and cytosolic arrays coexist in vivo, and cells intricately control the number, length and assembly rate of filaments in these arrays. Recent in vitro and in vivo studies have revealed novel molecular mechanisms that regulate the number of filament barbed and pointed ends and their respective assembly and disassembly rates, thus defining classes of dynamically different filaments, which coexist in the same cell. We propose that a global treadmilling process, in which a steady-state amount of polymerizable actin monomers is established by the dynamics of each network, is responsible for defining the size and turnover of coexisting actin networks. Furthermore, signal-induced changes in the partitioning of actin to distinct arrays (mediated by RHO GTPases) result in the establishment of various steady-state concentrations of polymerizable monomers, thereby globally influencing the growth rate of actin filaments.

  20. Actin-Based Feedback Circuits in Cell Migration and Endocytosis

    NASA Astrophysics Data System (ADS)

    Wang, Xinxin

    In this thesis, we study the switch and pulse functions of actin during two important cellular processes, cell migration and endocytosis. Actin is an abundant protein that can polymerize to form a dendritic network. The actin network can exert force to push or bend the cell membrane. During cell migration, the actin network behaves like a switch, assembling mostly at one end or at the other end. The end with the majority of the actin network is the leading edge, following which the cell can persistently move in the same direction. The other end, with the minority of the actin network, is the trailing edge, which is dragged by the cell as it moves forward. When subjected to large fluctuations or external stimuli, the leading edge and the trailing edge can interchange and change the direction of motion, like a motion switch. Our model of the actin network in a cell reveals that mechanical force is crucial for forming the motion switch. We find a transition from single state symmetric behavior to switch behavior, when tuning parameters such as the force. The model is studied by both stochastic simulations, and a set of rate equations that are consistent with the simulations. Endocytosis is a process by which cells engulf extracellular substances and recycle the cell membrane. In yeast cells, the actin network is transiently needed to overcome the pressure difference across the cell membrane caused by turgor pressure. The actin network behaves like a pulse, which assembles and then disassembles within about 30 seconds. Using a stochastic model, we reproduce the pulse behaviors of the actin network and one of its regulatory proteins, Las17. The model matches green fluorescence protein (GFP) experiments for wild-type cells. The model also predicts some phenotypes that modify or diminish the pulse behavior. The phenotypes are verified with both experiments performed at Washington University and with other groups' experiments. We find that several feedback mechanisms are

  1. Competition between Tropomyosin, Fimbrin, and ADF/Cofilin drives their sorting to distinct actin filament networks.

    PubMed

    Christensen, Jenna R; Hocky, Glen M; Homa, Kaitlin E; Morganthaler, Alisha N; Hitchcock-DeGregori, Sarah E; Voth, Gregory A; Kovar, David R

    2017-03-10

    The fission yeast actin cytoskeleton is an ideal, simplified system to investigate fundamental mechanisms behind cellular self-organization. By focusing on the stabilizing protein tropomyosin Cdc8, bundling protein fimbrin Fim1, and severing protein coffin Adf1, we examined how their pairwise and collective interactions with actin filaments regulate their activity and segregation to functionally diverse F-actin networks. Utilizing multi-color TIRF microscopy of in vitro reconstituted F-actin networks, we observed and characterized two distinct Cdc8 cables loading and spreading cooperatively on individual actin filaments. Furthermore, Cdc8, Fim1, and Adf1 all compete for association with F-actin by different mechanisms, and their cooperative association with actin filaments affects their ability to compete. Finally, competition between Fim1 and Adf1 for F-actin synergizes their activities, promoting rapid displacement of Cdc8 from a dense F-actin network. Our findings reveal that competitive and cooperative interactions between actin binding proteins help define their associations with different F-actin networks.

  2. Cable Television for Librarians. Cable Television Primer

    ERIC Educational Resources Information Center

    Briscoe, Wallace C.

    1973-01-01

    The development of cable television, its present state, and future prospects, including a possible role for libraries, are discussed. (Other conference materials are LI 503071 and 503073 through 503084.) (SJ)

  3. Magnet cable manufacturing

    SciTech Connect

    Royet, J.

    1990-10-01

    The cable is the heart of a superconducting accelerator magnet. Since the initial development of the Rutherford Cable more than twenty years ago, many improvements in manufacturing techniques have increased the current carrying capacity. When the Tevatron cable was specified fifteen years ago the current carrying capacity was 1800 A/mm{sup 2} at a field of 5.3T. During the intervening years it has been increased to 3000 A/mm{sup 2}. These improvements were due to refinements in the fabrication of the strands and the formation of the cable from the strands. The metallurgists were able to impart significant gains in performance by improving the homogeneity of the conductor. The engineers and technicians who designed and built the modern cabling machines made an enormous contribution by significantly reducing the degradation of wire performance that occurs when the wire was cabled. The fact that these gains were made while increasing the speed of cabling is one of the technological advances that made accelerators like the SSC possible. This article describes the cabling machines that were built to manufacture the cable for the full scale SSC prototype magnets and the low beta quadrupoles for the Fermilab Tevatron. This article also presents a compendium of the knowledge that was gained in the struggle to make high performance cable to exacting dimensional standards and at the throughput needed for the SSC. The material is an important part of the technology transfer from the Department of energy Laboratories to Industry.

  4. Spontaneous actin dynamics in contractile rings

    NASA Astrophysics Data System (ADS)

    Kruse, Karsten; Wollrab, Viktoria; Thiagarajan, Raghavan; Wald, Anne; Riveline, Daniel

    Networks of polymerizing actin filaments are known to be capable to self-organize into a variety of structures. For example, spontaneous actin polymerization waves have been observed in living cells in a number of circumstances, notably, in crawling neutrophils and slime molds. During later stages of cell division, they can also spontaneously form a contractile ring that will eventually cleave the cell into two daughter cells. We present a framework for describing networks of polymerizing actin filaments, where assembly is regulated by various proteins. It can also include the effects of molecular motors. We show that the molecular processes driven by these proteins can generate various structures that have been observed in contractile rings of fission yeast and mammalian cells. We discuss a possible functional role of each of these patterns. The work was supported by Agence Nationale de la Recherche, France, (ANR-10-LABX-0030-INRT) and by Deutsche Forschungsgemeinschaft through SFB1027.

  5. Actin Out: Regulation of the Synaptic Cytoskeleton

    PubMed Central

    Spence, Erin F.; Soderling, Scott H.

    2015-01-01

    The small size of dendritic spines belies the elaborate role they play in excitatory synaptic transmission and ultimately complex behaviors. The cytoskeletal architecture of the spine is predominately composed of actin filaments. These filaments, which at first glance might appear simple, are also surprisingly complex. They dynamically assemble into different structures and serve as a platform for orchestrating the elaborate responses of the spine during spinogenesis and experience-dependent plasticity. Multiple mutations associated with human neurodevelopmental and psychiatric disorders involve genes that encode regulators of the synaptic cytoskeleton. A major, unresolved question is how the disruption of specific actin filament structures leads to the onset and progression of complex synaptic and behavioral phenotypes. This review will cover established and emerging mechanisms of actin cytoskeletal remodeling and how this influences specific aspects of spine biology that are implicated in disease. PMID:26453304

  6. Quantitative Fluorescent Speckle Microscopy (QFSM) to Measure Actin Dynamics

    PubMed Central

    Mendoza, Michelle C.; Besson, Sebastien; Danuser, Gaudenz

    2012-01-01

    Quantitative Fluorescent Speckle Microscopy (QFSM) is a live cell imaging method to analyze the dynamics of macromolecular assemblies with high spatial and temporal resolution. Its greatest successes were in the analysis of actin filament and adhesion dynamics in the context of cell migration and microtubule dynamics in interphase and the meotic/mitotic spindle. Here, we focus on the former application to illustrate the procedures of FSM imaging and the computational image processing that extracts quantitative information from these experiments. QFSM is advantageous over other methods because it measures the movement and turnover kinetics of the actin filament (F-actin) network in living cells across the entire field of view. Experiments begin with microinjection of fluorophore-labeled actin into cells, which generate a low ratio of fluorescently-labeled:endogenous unlabeled actin monomers. Spinning disk confocal or wide-field imaging then visualizes fluorophore clusters (2–8 actin monomers) within the assembled F-actin network as speckles. QFSM software identifies and computationally tracks and utilizes the location, appearance, and disappearance of speckles to derive network flows and maps of the rate of filament assembly and disassembly. PMID:23042526

  7. Cable Tester Box

    NASA Technical Reports Server (NTRS)

    Lee, Jason H.

    2011-01-01

    Cables are very important electrical devices that carry power and signals across multiple instruments. Any fault in a cable can easily result in a catastrophic outcome. Therefore, verifying that all cables are built to spec is a very important part of Electrical Integration Procedures. Currently, there are two methods used in lab for verifying cable connectivity. (1) Using a Break-Out Box and an ohmmeter this method is time-consuming but effective for custom cables and (2) Commercial Automated Cable Tester Boxes this method is fast, but to test custom cables often requires pre-programmed configuration files, and cables used on spacecraft are often uniquely designed for specific purposes. The idea is to develop a semi-automatic continuity tester that reduces human effort in cable testing, speeds up the electrical integration process, and ensures system safety. The JPL-Cable Tester Box is developed to check every single possible electrical connection in a cable in parallel. This system indicates connectivity through LED (light emitting diode) circuits. Users can choose to test any pin/shell (test node) with a single push of a button, and any other nodes that are shorted to the test node, even if they are in the same connector, will light up with the test node. The JPL-Cable Tester Boxes offers the following advantages: 1. Easy to use: The architecture is simple enough that it only takes 5 minutes for anyone to learn how operate the Cable Tester Box. No pre-programming and calibration are required, since this box only checks continuity. 2. Fast: The cable tester box checks all the possible electrical connections in parallel at a push of a button. If a cable normally takes half an hour to test, using the Cable Tester Box will improve the speed to as little as 60 seconds to complete. 3. Versatile: Multiple cable tester boxes can be used together. As long as all the boxes share the same electrical potential, any number of connectors can be tested together.

  8. What we talk about when we talk about nuclear actin

    PubMed Central

    Belin, Brittany J; Mullins, R Dyche

    2013-01-01

    In the cytoplasm, actin filaments form crosslinked networks that enable eukaryotic cells to transport cargo, change shape, and move. Actin is also present in the nucleus but, in this compartment, its functions are more cryptic and controversial. If we distill the substantial literature on nuclear actin down to its essentials, we find four, recurring, and more-or-less independent, claims: (1) crosslinked networks of conventional actin filaments span the nucleus and help maintain its structure and organize its contents; (2) assembly or contraction of filaments regulates specific nuclear events; (3) actin monomers moonlight as subunits of chromatin remodeling complexes, independent of their ability to form filaments; and (4) modified actin monomers or oligomers, structurally distinct from canonical, cytoskeletal filaments, mediate nuclear events by unknown mechanisms. We discuss the evidence underlying these claims and as well as their strengths and weaknesses. Next, we describe our recent work, in which we built probes specific for nuclear actin and used them to describe the form and distribution of actin in somatic cell nuclei. Finally, we discuss how different forms of nuclear actin may play different roles in different cell types and physiological contexts. PMID:23934079

  9. Actin Mechanics and Fragmentation*

    PubMed Central

    De La Cruz, Enrique M.; Gardel, Margaret L.

    2015-01-01

    Cell physiological processes require the regulation and coordination of both mechanical and dynamical properties of the actin cytoskeleton. Here we review recent advances in understanding the mechanical properties and stability of actin filaments and how these properties are manifested at larger (network) length scales. We discuss how forces can influence local biochemical interactions, resulting in the formation of mechanically sensitive dynamic steady states. Understanding the regulation of such force-activated chemistries and dynamic steady states reflects an important challenge for future work that will provide valuable insights as to how the actin cytoskeleton engenders mechanoresponsiveness of living cells. PMID:25957404

  10. Bundling of actin filaments by elongation factor 1 alpha inhibits polymerization at filament ends

    PubMed Central

    1996-01-01

    Elongation factor 1 alpha (EF1 alpha) is an abundant protein that binds aminoacyl-tRNA and ribosomes in a GTP-dependent manner. EF1 alpha also interacts with the cytoskeleton by binding and bundling actin filaments and microtubules. In this report, the effect of purified EF1 alpha on actin polymerization and depolymerization is examined. At molar ratios present in the cytosol, EF1 alpha significantly blocks both polymerization and depolymerization of actin filaments and increases the final extent of actin polymer, while at high molar ratios to actin, EF1 alpha nucleates actin polymerization. Although EF1 alpha binds actin monomer, this monomer-binding activity does not explain the effects of EF1 alpha on actin polymerization at physiological molar ratios. The mechanism for the inhibition of polymerization is related to the actin-bundling activity of EF1 alpha. Both ends of the actin filament are inhibited for polymerization and both bundling and the inhibition of actin polymerization are affected by pH within the same physiological range; at high pH both bundling and the inhibition of actin polymerization are reduced. Additionally, it is seen that the binding of aminoacyl-tRNA to EF1 alpha releases EF1 alpha's inhibiting effect on actin polymerization. These data demonstrate that EF1 alpha can alter the assembly of F-actin, a filamentous scaffold on which non- membrane-associated protein translation may be occurring in vivo. PMID:8947553

  11. Coaxial cable stripping device facilitates RF cabling fabrication

    NASA Technical Reports Server (NTRS)

    Hughes, R. S.; Tobias, R. A.

    1967-01-01

    Coaxial cable stripping device assures clean, right angled shoulder for RF cable connector fabrication. This method requires minimal skill and creates a low voltage standing wave ratio and mechanical stability in the interconnecting RF Cables.

  12. Actin Polymerization is Stimulated by Actin Crosslinking Protein Palladin

    PubMed Central

    Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G.; Orlova, Albina; Egelman, Edward H.; Beck, Moriah R.

    2016-01-01

    The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the coordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. Here we show that the actin binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro crosslinking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of G-actin, akin to metal ions, either through charge neutralization or conformational changes. PMID:26607837

  13. Bacillus anthracis Edema Toxin Impairs Neutrophil Actin-Based Motility▿

    PubMed Central

    Szarowicz, Sarah E.; During, Russell L.; Li, Wei; Quinn, Conrad P.; Tang, Wei-Jen; Southwick, Frederick S.

    2009-01-01

    Inhalation anthrax results in high-grade bacteremia and is accompanied by a delay in the rise of the peripheral polymorphonuclear neutrophil (PMN) count and a paucity of PMNs in the infected pleural fluid and mediastinum. Edema toxin (ET) is one of the major Bacillus anthracis virulence factors and consists of the adenylate cyclase edema factor (EF) and protective antigen (PA). Relatively low concentrations of ET (100 to 500 ng/ml of PA and EF) significantly impair human PMN chemokinesis, chemotaxis, and ability to polarize. These changes are accompanied by a reduction in chemoattractant-stimulated PMN actin assembly. ET also causes a significant decrease in Listeria monocytogenes intracellular actin-based motility within HeLa cells. These defects in actin assembly are accompanied by a >50-fold increase in intracellular cyclic AMP and a >4-fold increase in the phosphorylation of protein kinase A. We have previously shown that anthrax lethal toxin (LT) also impairs neutrophil actin-based motility (R. L. During, W. Li, B. Hao, J. M. Koenig, D. S. Stephens, C. P. Quinn, and F. S. Southwick, J. Infect. Dis. 192:837-845, 2005), and we now find that LT combined with ET causes an additive inhibition of PMN chemokinesis, polarization, chemotaxis, and FMLP (N-formyl-met-leu-phe)-induced actin assembly. We conclude that ET alone or combined with LT impairs PMN actin assembly, resulting in paralysis of PMN chemotaxis. PMID:19349425

  14. Actin polymerization machinery: the finish line of signaling networks, the starting point of cellular movement.

    PubMed

    Disanza, A; Steffen, A; Hertzog, M; Frittoli, E; Rottner, K; Scita, G

    2005-05-01

    Dynamic assembly of actin filaments generates the forces supporting cell motility. Several recent biochemical and genetic studies have revealed a plethora of different actin binding proteins whose coordinated activity regulates the turnover of actin filaments, thus controlling a variety of actin-based processes, including cell migration. Additionally, emerging evidence is highlighting a scenario whereby the same basic set of actin regulatory proteins is also the convergent node of different signaling pathways emanating from extracellular stimuli, like those from receptor tyrosine kinases. Here, we will focus on the molecular mechanisms of how the machinery of actin polymerization functions and is regulated, in a signaling-dependent mode, to generate site-directed actin assembly leading to cell motility.

  15. A small molecule inhibitor of tropomyosin dissociates actin binding from tropomyosin-directed regulation of actin dynamics

    PubMed Central

    Bonello, Teresa T.; Janco, Miro; Hook, Jeff; Byun, Alex; Appaduray, Mark; Dedova, Irina; Hitchcock-DeGregori, Sarah; Hardeman, Edna C.; Stehn, Justine R.; Böcking, Till; Gunning, Peter W.

    2016-01-01

    The tropomyosin family of proteins form end-to-end polymers along the actin filament. Tumour cells rely on specific tropomyosin-containing actin filament populations for growth and survival. To dissect out the role of tropomyosin in actin filament regulation we use the small molecule TR100 directed against the C terminus of the tropomyosin isoform Tpm3.1. TR100 nullifies the effect of Tpm3.1 on actin depolymerisation but surprisingly Tpm3.1 retains the capacity to bind F-actin in a cooperative manner. In vivo analysis also confirms that, in the presence of TR100, fluorescently tagged Tpm3.1 recovers normally into stress fibers. Assembling end-to-end along the actin filament is thereby not sufficient for tropomyosin to fulfil its function. Rather, regulation of F-actin stability by tropomyosin requires fidelity of information communicated at the barbed end of the actin filament. This distinction has significant implications for perturbing tropomyosin-dependent actin filament function in the context of anti-cancer drug development. PMID:26804624

  16. Aging assessment of cables

    SciTech Connect

    Jacobus, M.J.

    1992-04-01

    This paper summarizes the results of aging, condition monitoring, and accident testing of Class 1E cables used in nuclear power generating stations. Three sets of cables were aged for up to 9 months under simultaneous thermal ({approximately}100{degrees}C) and radiation ({approximately}0.10 kGy/hr) conditions. After the aging, the cables were exposed to a simulated accident consisting of high dose rate irradiation ({approximately}6 kGy/hr) followed by a high temperature steam (up to 400{degrees}C) exposure. A fourth set of cables, which were unaged, was also exposed to the accident conditions. The cables that were aged for 3 months and then accident tested were subsequently exposed to a high temperature steam fragility test (up to 400{degrees}C), while the cables that were aged for 6 months and then accident tested were subsequently exposed to a 1000-hour submergence test in a chemical solution. The results of these tests do not indicate any reason to believe that many popular nuclear power plant cable products cannot inherently be qualified for 60 years of operation for conditions simulated by this testing. Mechanical measurements (primarily elongation, modulus, and density) are more effective than electrical measurements for monitoring age-related degradation. In the high temperature steam test, ethylene propylene rubber (EPR) cable materials generally survived to higher temperatures than crosslinked polyolefin (XLPO) cable materials. In dielectric testing after the submergence testing, the XLPO materials performed better than the EPR materials.

  17. Aging assessment of cables

    SciTech Connect

    Jacobus, M.J.

    1992-01-01

    This paper summarizes the results of aging, condition monitoring, and accident testing of Class 1E cables used in nuclear power generating stations. Three sets of cables were aged for up to 9 months under simultaneous thermal ({approximately}100{degrees}C) and radiation ({approximately}0.10 kGy/hr) conditions. After the aging, the cables were exposed to a simulated accident consisting of high dose rate irradiation ({approximately}6 kGy/hr) followed by a high temperature steam (up to 400{degrees}C) exposure. A fourth set of cables, which were unaged, was also exposed to the accident conditions. The cables that were aged for 3 months and then accident tested were subsequently exposed to a high temperature steam fragility test (up to 400{degrees}C), while the cables that were aged for 6 months and then accident tested were subsequently exposed to a 1000-hour submergence test in a chemical solution. The results of these tests do not indicate any reason to believe that many popular nuclear power plant cable products cannot inherently be qualified for 60 years of operation for conditions simulated by this testing. Mechanical measurements (primarily elongation, modulus, and density) are more effective than electrical measurements for monitoring age-related degradation. In the high temperature steam test, ethylene propylene rubber (EPR) cable materials generally survived to higher temperatures than crosslinked polyolefin (XLPO) cable materials. In dielectric testing after the submergence testing, the XLPO materials performed better than the EPR materials.

  18. Axonal actin in action: Imaging actin dynamics in neurons.

    PubMed

    Ladt, Kelsey; Ganguly, Archan; Roy, Subhojit

    2016-01-01

    Actin is a highly conserved, key cytoskeletal protein involved in numerous structural and functional roles. In neurons, actin has been intensively investigated in axon terminals-growth cones-and dendritic spines, but details about actin structure and dynamics in axon shafts have remained obscure for decades. A major barrier in the field has been imaging actin. Actin exists as soluble monomers (G-actin) as well as actin filaments (F-actin), and labeling actin with conventional fluorescent probes like GFP/RFP typically leads to a diffuse haze that makes it difficult to discern kinetic behaviors. In a recent publication, we used F-actin selective probes to visualize actin dynamics in axons, resolving striking actin behaviors that have not been described before. However, using these probes to visualize actin dynamics is challenging as they can cause bundling of actin filaments; thus, experimental parameters need to be strictly optimized. Here we describe some practical methodological details related to using these probes for visualizing F-actin dynamics in axons.

  19. Bulk cytoplasmic actin and its functions in meiosis and mitosis.

    PubMed

    Field, Christine M; Lénárt, Péter

    2011-10-11

    Discussions of actin cell biology generally focus on the cortex, a thin, actin-rich layer of cytoplasm under the plasma membrane. Here we review the much less studied biology of actin filaments deeper in the cytoplasm and their recently revealed functions in mitosis and meiosis that are most prominent in large oocyte, egg and early embryo cells. The cellular functions of cytoplasmic actin range from the assembly and positioning of meiotic spindles to the prevention of cytoplasmic streaming. We discuss the possible use of evolutionarily conserved mechanisms to nucleate and organize actin filaments to achieve these diverse cellular functions, the cell-cycle regulation of these functions, and the many unanswered questions about this largely unexplored mechanism of cytoplasmic organization.

  20. Cable Diagnostic Focused Initiative

    SciTech Connect

    Hartlein, R.A.; Hampton, R.N.

    2010-12-30

    This report summarizes an extensive effort made to understand how to effectively use the various diagnostic technologies to establish the condition of medium voltage underground cable circuits. These circuits make up an extensive portion of the electric delivery infrastructure in the United States. Much of this infrastructure is old and experiencing unacceptable failure rates. By deploying efficient diagnostic testing programs, electric utilities can replace or repair circuits that are about to fail, providing an optimal approach to improving electric system reliability. This is an intrinsically complex topic. Underground cable systems are not homogeneous. Cable circuits often contain multiple branches with different cable designs and a range of insulation materials. In addition, each insulation material ages differently as a function of time, temperature and operating environment. To complicate matters further, there are a wide variety of diagnostic technologies available for assessing the condition of cable circuits with a diversity of claims about the effectiveness of each approach. As a result, the benefits of deploying cable diagnostic testing programs have been difficult to establish, leading many utilities to avoid the their use altogether. This project was designed to help address these issues. The information provided is the result of a collaborative effort between Georgia Tech NEETRAC staff, Georgia Tech academic faculty, electric utility industry participants, as well as cable system diagnostic testing service providers and test equipment providers. Report topics include: •How cable systems age and fail, •The various technologies available for detecting potential failure sites, •The advantages and disadvantages of different diagnostic technologies, •Different approaches for utilities to employ cable system diagnostics. The primary deliverables of this project are this report, a Cable Diagnostic Handbook (a subset of this report) and an online

  1. Technology Validation of Optical Fiber Cables for Space Flight Environments

    NASA Technical Reports Server (NTRS)

    Ott, Melanie N.; Friedberg, Patricia; Day, John H. (Technical Monitor)

    2000-01-01

    Periodically, commercially available (COTS) optical fiber cable assemblies are characterized for space flight usage under the NASA Electronic Parts and Packaging Program (NEPP). The purpose of this is to provide a family of optical fiber cable options to a variety of different harsh environments typical to space flight missions. The optical fiber cables under test are evaluated to bring out known failure mechanisms that are expected to occur during a typical mission. The tests used to characterize COTS cables include: (1) vacuum exposure, (2) thermal cycling, and (3) radiation exposure. Presented here are the results of the testing conducted at NASA Goddard Space Flight Center on COTS optical fiber cables over this past year. Several optical fiber cables were characterized for their thermal stability both during and after thermal cycling. The results show how much preconditioning is necessary for a variety of available cables to remain thermally stable in a space flight environment. Several optical fibers of dimensions 100/140/172 microns were characterized for their radiation effects at -125 C using the dose rate requirements of International Space Station. One optical fiber cable in particular was tested for outgassing to verify whether an acrylate coated fiber could be used in a space flight optical cable configuration.

  2. Bulkiness or aromatic nature of tyrosine-143 of actin is important for the weak binding between F-actin and myosin-ADP-phosphate

    SciTech Connect

    Gomibuchi, Yuki; Uyeda, Taro Q.P.; Wakabayashi, Takeyuki

    2013-11-29

    Highlights: •The effect of mutation of Tyr143 that becomes more exposed on assembly was examined. •Mutation of tyrosine-143 of Dictyostelium actin changed actin polymerizability. •The bulkiness or aromatic nature of Tyr143 is important for the weak binding. •The weak interaction between myosin and actin strengthened by Tyr143Trp mutation. -- Abstract: Actin filaments (F-actin) interact with myosin and activate its ATPase to support force generation. By comparing crystal structures of G-actin and the quasi-atomic model of F-actin based on high-resolution cryo-electron microscopy, the tyrosine-143 was found to be exposed more than 60 Å{sup 2} to the solvent in F-actin. Because tyrosine-143 flanks the hydrophobic cleft near the hydrophobic helix that binds to myosin, the mutant actins, of which the tyrosine-143 was replaced with tryptophan, phenylalanine, or isoleucine, were generated using the Dictyostelium expression system. It polymerized significantly poorly when induced by NaCl, but almost normally by KCl. In the presence of phalloidin and KCl, the extents of the polymerization of all the mutant actins were comparable to that of the wild-type actin so that the actin-activated myosin ATPase activity could be reliably compared. The affinity of skeletal heavy meromyosin to F-actin and the maximum ATPase activity (V{sub max}) were estimated by a double reciprocal plot. The Tyr143Trp-actin showed the higher affinity (smaller K{sub app}) than that of the wild-type actin, with the V{sub max} being almost unchanged. The K{sub app} and V{sub max} of the Tyr143Phe-actin were similar to those of the wild-type actin. However, the activation by Tyr143Ile-actin was much smaller than the wild-type actin and the accurate determination of K{sub app} was difficult. Comparison of the myosin ATPase activated by the various mutant actins at the same concentration of F-actin showed that the extent of activation correlates well with the solvent-accessible surface areas (ASA

  3. Computer-Aided Engineering Of Cabling

    NASA Technical Reports Server (NTRS)

    Billitti, Joseph W.

    1989-01-01

    Program generates data sheets, drawings, and other information on electrical connections. DFACS program, centered around single data base, has built-in menus providing easy input of, and access to, data for all personnel involved in system, subsystem, and cabling. Enables parallel design of circuit-data sheets and drawings of harnesses. Also recombines raw information to generate automatically various project documents and drawings, including index of circuit-data sheets, list of electrical-interface circuits, lists of assemblies and equipment, cabling trees, and drawings of cabling electrical interfaces and harnesses. Purpose of program to provide engineering community with centralized data base for putting in, and gaining access to, functional definition of system as specified in terms of details of pin connections of end circuits of subsystems and instruments and data on harnessing. Primary objective to provide instantaneous single point of interchange of information, thus avoiding

  4. Interaction of microtubules with the actin cytoskeleton via cross-talk of EB1-containing +TIPs and γ-actin in epithelial cells

    PubMed Central

    Dugina, Vera; Alieva, Irina; Khromova, Natalya; Kireev, Igor; Gunning, Peter W.; Kopnin, Pavel

    2016-01-01

    Actin microfilaments and microtubules are both highly dynamic cytoskeleton components implicated in a wide range of intracellular processes as well as cell-cell and cell-substrate interactions. The interactions of actin filaments with the microtubule system play an important role in the assembly and maintenance of 3D cell structure. Here we demonstrate that cytoplasmic actins are differentially distributed in relation to the microtubule system. LSM, 3D-SIM, proximity ligation assay (PLA) and co-immunoprecipitation methods applied in combination with selective depletion of β- or γ-cytoplasmic actins revealed a selective interaction between microtubules and γ-, but not β-cytoplasmic actin via the microtubule +TIPs protein EB1. EB1-positive comet distribution analysis and quantification have shown more effective microtubule growth in the absence of β-actin. Our data represent the first demonstration that microtubule +TIPs protein EB1 interacts mainly with γ-cytoplasmic actin in epithelial cells. PMID:27683037

  5. Interaction of microtubules with the actin cytoskeleton via cross-talk of EB1-containing +TIPs and γ-actin in epithelial cells.

    PubMed

    Dugina, Vera; Alieva, Irina; Khromova, Natalya; Kireev, Igor; Gunning, Peter W; Kopnin, Pavel

    2016-11-08

    Actin microfilaments and microtubules are both highly dynamic cytoskeleton components implicated in a wide range of intracellular processes as well as cell-cell and cell-substrate interactions. The interactions of actin filaments with the microtubule system play an important role in the assembly and maintenance of 3D cell structure. Here we demonstrate that cytoplasmic actins are differentially distributed in relation to the microtubule system. LSM, 3D-SIM, proximity ligation assay (PLA) and co-immunoprecipitation methods applied in combination with selective depletion of β- or γ-cytoplasmic actins revealed a selective interaction between microtubules and γ-, but not β-cytoplasmic actin via the microtubule +TIPs protein EB1. EB1-positive comet distribution analysis and quantification have shown more effective microtubule growth in the absence of β-actin. Our data represent the first demonstration that microtubule +TIPs protein EB1 interacts mainly with γ-cytoplasmic actin in epithelial cells.

  6. Multistrand superconductor cable

    DOEpatents

    Borden, Albert R.

    1985-01-01

    Improved multistrand Rutherford-type superconductor cable is produced by using strands which are preformed, prior to being wound into the cable, so that each strand has a variable cross section, with successive portions having a substantially round cross section, a transitional oval cross section, a rectangular cross section, a transitional oval cross section, a round cross section and so forth, in repetitive cycles along the length of the strand. The cable is wound and flattened so that the portions of rectangular cross section extend across the two flat sides of the cable at the strand angle. The portions of round cross section are bent at the edges of the flattened cable, so as to extend between the two flat sides. The rectangular portions of the strands slide easily over one another, so as to facilitate flexing and bending of the cable, while also minimizing the possibility of causing damage to the strands by such flexing or bending. Moreover, the improved cable substantially maintains its compactness and cross-sectional shape when the cable is flexed or bent.

  7. Submarine cable route survey

    SciTech Connect

    Herrouin, G.; Scuiller, T.

    1995-12-31

    The growth of telecommunication market is very significant. From the beginning of the nineties, more and more the use of optical fiber submarine cables is privileged to that of satellites. These submarine telecommunication highways require accurate surveys in order to select the optimum route and determine the cable characteristics. Advanced technology tools used for these surveys are presented along with their implementation.

  8. Aluminum modifies the viscosity of filamentous actin solutions as measured by optical displacement microviscometry.

    PubMed

    Arnoys, E J; Schindler, M

    2000-01-01

    A microtechnique has been developed that is capable of measuring the viscosity of filamentous actin (F-actin) solutions. This method, called optical displacement microviscometry (ODM), was utilized to determine the changes in viscosity of solutions of rabbit muscle, human platelet, and maize pollen actin when measured in the absence and presence of aluminum. Measurements demonstrated that the viscosity of the different actin solutions decreased with aluminum concentration. In contrast, increases in viscosity were observed when aluminum was added to F-actin solutions containing filamin (chicken gizzard), a protein that bundles actin filaments. Confocal fluorescence imaging of pure actin solutions in the presence of aluminum showed a disrupted actin network composed of fragmented actin filaments in the form of small aggregates. In contrast, in the presence of filamin, aluminum promoted the formation of thicker actin filaments. These measurements demonstrate that aluminum can affect actin filaments differentially depending on the presence of an actin-binding protein. In addition, a strong correlation is observed between the changes in viscosity as measured by ODM and the thickness and assembled state of bundles of actin filaments.

  9. Polycation induced actin bundles.

    PubMed

    Muhlrad, Andras; Grintsevich, Elena E; Reisler, Emil

    2011-04-01

    Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon the addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100 mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4Å) MTS-1 (1,1-methanedyl bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder.

  10. Multistrand superconductor cable

    DOEpatents

    Borden, A.R.

    1984-03-08

    Improved multistrand Rutherford-type superconductor cable is produced by using strands which are preformed, prior to being wound into the cable, so that each strand has a variable cross section, with successive portions having a substantially round cross section, a transitional oval cross section, a rectangular cross section, a transitional oval cross section, a round cross section and so forth, in repetitive cycles along the length of the strand. The cable is wound and flattened so that the portions of rectangular cross section extend across the two flat sides of the cable at the strand angle. The portions of round cross section are bent at the edges of the flattened cable, so as to extend between the two flat sides. The rectangular portions of the strands slide easil

  11. In Vivo Imaging and Characterization of Actin Microridges

    PubMed Central

    Lam, Pui-ying; Mangos, Steve; Green, Julie M.; Reiser, Jochen; Huttenlocher, Anna

    2015-01-01

    Actin microridges form labyrinth like patterns on superficial epithelial cells across animal species. This highly organized assembly has been implicated in mucus retention and in the mechanical structure of mucosal surfaces, however the mechanisms that regulate actin microridges remain largely unknown. Here we characterize the composition and dynamics of actin microridges on the surface of zebrafish larvae using live imaging. Microridges contain phospho-tyrosine, cortactin and VASP, but not focal adhesion kinase. Time-lapse imaging reveals dynamic changes in the length and branching of microridges in intact animals. Transient perturbation of the microridge pattern occurs before cell division with rapid re-assembly during and after cytokinesis. Microridge assembly is maintained with constitutive activation of Rho or inhibition of myosin II activity. However, expression of dominant negative RhoA or Rac alters microridge organization, with an increase in distance between microridges. Latrunculin A treatment and photoconversion experiments suggest that the F-actin filaments are actively treadmilling in microridges. Accordingly, inhibition of Arp2/3 or PI3K signaling impairs microridge structure and length. Taken together, actin microridges in zebrafish represent a tractable in vivo model to probe pattern formation and dissect Arp2/3-mediated actin dynamics in vivo. PMID:25629723

  12. Emerin organizes actin flow for nuclear movement and centrosome orientation in migrating fibroblasts.

    PubMed

    Chang, Wakam; Folker, Eric S; Worman, Howard J; Gundersen, Gregg G

    2013-12-01

    In migrating fibroblasts, rearward movement of the nucleus orients the centrosome toward the leading edge. Nuclear movement results from coupling rearward-moving, dorsal actin cables to the nucleus by linear arrays of nesprin-2G and SUN2, termed transmembrane actin-associated nuclear (TAN) lines. A-type lamins anchor TAN lines, prompting us to test whether emerin, a nuclear membrane protein that interacts with lamins and TAN line proteins, contributes to nuclear movement. In fibroblasts depleted of emerin, nuclei moved nondirectionally or completely failed to move. Consistent with these nuclear movement defects, dorsal actin cable flow was nondirectional in cells lacking emerin. TAN lines formed normally in cells lacking emerin and were coordinated with the erratic nuclear movements, although in 20% of the cases, TAN lines slipped over immobile nuclei. Myosin II drives actin flow, and depletion of myosin IIB, but not myosin IIA, showed similar nondirectional nuclear movement and actin flow as in emerin-depleted cells. Myosin IIB specifically coimmunoprecipitated with emerin, and emerin depletion prevented myosin IIB localization near nuclei. These results show that emerin functions with myosin IIB to polarize actin flow and nuclear movement in fibroblasts, suggesting a novel function for the nuclear envelope in organizing directional actin flow and cytoplasmic polarity.

  13. A unique cabling designed to produce Rutherford-type superconducting cable for the SSC project

    SciTech Connect

    Grisel, J.; Royet, J.M.; Scanlan, R.M.; Armer, R.

    1988-08-01

    Up to 25,000 Km of keystoned flat cable must be produced for the SSC project. Starting from a specification developed by Lawrence Berkeley Laboratory (LBL), a special cabling machine has been designed by Dour Metal. It has been designed to be able to run at a speed corresponding to a maximum production rate of 10 m/min. This cabling machine is the key part of the production line which consists of a precision Turkshead equipped with a variable power drive, a caterpillar, a dimensional control bench, a data acquisition system, and a take-up unit. The main features of the cabling unit to be described are a design with nearly equal path length between spool and assembling point for all the wires, and the possibility to run the machine with several over- or under-twisting ratios between cable and wires. These requirements led Dour Metal to the choice of an unconventional mechanical concept for a cabling machine. 4 refs., 2 figs.

  14. Reconstitution of actin-based motility of Listeria and Shigella using pure proteins

    NASA Astrophysics Data System (ADS)

    Loisel, Thomas P.; Boujemaa, Rajaa; Pantaloni, Dominique; Carlier, Marie-France

    1999-10-01

    Actin polymerization is essential for cell locomotion and is thought to generate the force responsible for cellular protrusions. The Arp2/3 complex is required to stimulate actin assembly at the leading edge in response to signalling. The bacteria Listeria and Shigella bypass the signalling pathway and harness the Arp2/3 complex to induce actin assembly and to propel themselves in living cells. However, the Arp2/3 complex alone is insufficient to promote movement. Here we have used pure components of the actin cytoskeleton to reconstitute sustained movement in Listeria and Shigella in vitro. Actin-based propulsion is driven by the free energy released by ATP hydrolysis linked to actin polymerization, and does not require myosin. In addition to actin and activated Arp2/3 complex, actin depolymerizing factor (ADF, or cofilin) and capping protein are also required for motility as they maintain a high steady-state level of G-actin, which controls the rate of unidirectional growth of actin filaments at the surface of the bacterium. The movement is more effective when profilin, α-actinin and VASP (for Listeria) are also included. These results have implications for our understanding of the mechanism of actin-based motility in cells.

  15. VIEW OF CABLES AND TAPES ASSOCIATED WITH ADRIVE CONTROL ROD ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF CABLES AND TAPES ASSOCIATED WITH A-DRIVE CONTROL ROD SYSTEM, AT LEVEL +15’, DIRECTLY ABOVE PDP CONTROL ROOM, LOOKING NORTHWEST. THE CABLES FROM THE PDP ROOM GO THROUGH THE CONCRETE WALL, MAKE A RIGHT ANGLE TURN DOWNWARD, AND DESCEND INTO THE PDP CONTROL ROOM AS VERTICAL TAPES - Physics Assembly Laboratory, Area A/M, Savannah River Site, Aiken, Aiken County, SC

  16. Bringing Cable into the Classroom.

    ERIC Educational Resources Information Center

    Blubaugh, Donelle

    1999-01-01

    Cable TV may be an educationally and fiscally sound way to inspire active learning. Creative TV applications help teachers address potentially disabling social and emotional factors. The Cable in the Classroom program offers over 80,000 eligible schools free cable connections, free basic monthly cable service, and copyright clearances for off-air…

  17. Cable Television; A Bibliographic Review.

    ERIC Educational Resources Information Center

    Schoenung, James

    This bibliographic review of publications in the field of cable television begins with an introduction to cable television and an outline of the history and development of cable television. Particular attention is given to the regulatory activities of the Federal Communications Commission and the unfulfilled potential of cable television. The…

  18. The control of actin nucleotide exchange by thymosin beta 4 and profilin. A potential regulatory mechanism for actin polymerization in cells.

    PubMed Central

    Goldschmidt-Clermont, P J; Furman, M I; Wachsstock, D; Safer, D; Nachmias, V T; Pollard, T D

    1992-01-01

    We present evidence for a new mechanism by which two major actin monomer binding proteins, thymosin beta 4 and profilin, may control the rate and the extent of actin polymerization in cells. Both proteins bind actin monomers transiently with a stoichiometry of 1:1. When bound to actin, thymosin beta 4 strongly inhibits the exchange of the nucleotide bound to actin by blocking its dissociation, while profilin catalytically promotes nucleotide exchange. Because both proteins exchange rapidly between actin molecules, low concentrations of profilin can overcome the inhibitory effects of high concentrations of thymosin beta 4 on the nucleotide exchange. These reactions may allow variations in profilin concentration (which may be regulated by membrane polyphosphoinositide metabolism) to control the ratio of ATP-actin to ADP-actin. Because ATP-actin subunits polymerize more readily than ADP-actin subunits, this ratio may play a key regulatory role in the assembly of cellular actin structures, particularly under circumstances of rapid filament turnover. Images PMID:1330091

  19. Applications of optical fibre Bragg gratings sensing technology-based smart stay cables

    NASA Astrophysics Data System (ADS)

    Li, Hui; Ou, Jinping; Zhou, Zhi

    2009-10-01

    Stay cable is one of the most critical structural components of a bridge. However, it readily suffers from fatigue damage, corrosion damage, and their coupled effects. Thus, health monitoring of stay cables is important for ensuring the integrity and safety of a bridge. A smart stay cable assembled with optical fibre Bragg grating (OFBG) strain and temperature sensors was proposed in this study. To protect the OFBG sensors against breakage in application, the OFBG sensors were first incorporated into a glass-fibre-reinforced polymer (GFRP) bar (GFRP-OFBG bar) when the bar was fabricated. To fabricate cables assembled with OFBG sensors, several GFRP-OFBG bars were inserted into the hollows of steel wires and fixed with the steel wires together at the anchorages of the cable. Therefore, the GFRP-OFBG bars can consistently deform with the steel wires in a cable and the smart stay cable can sense its own strain and temperature through OFBG sensors. The fabrication procedure of the smart stay cable was developed and the self-sensing property of the smart stay cable was calibrated. Finally, the application of the smart stay cables on the Tianjing Yonghe Bridge was demonstrated. The fatigue accumulative damage of the smart stay cables was evaluated based on field monitoring strain.

  20. Critical currents of Rutherford MgB2 cables compacted by two-axial rolling

    NASA Astrophysics Data System (ADS)

    Kopera, L.; Kováč, P.; Kulich, M.; Melišek, T.; Rindfleisch, M.; Yue, J.; Hušek, I.

    2017-01-01

    Two types of Rutherford cables made of two strand layers of commercial MgB2 wires manufactured by Hyper Tech Research, Inc. have been made. Flat rectangular cables consisting of 12 single-core MgB2/Nb/Cu10Ni, or 6-filaments MgB2/Nb/Cu strands, both of diameter 390 mewm, were assembled using a back-twist cabling machine with transposition length of 20 mm. In order to analyze impact of the cable compaction on critical currents, cables were two-axially rolled, each by a single step reduction of 3.5%-29.7% to thickness range of 0.775-0.62 mm. It was found that by increasing the packing factor (PF) of cable above 0.79, the critical current begins to increase. It is improved nearly two times up to the PF limit 0.89. Compaction over the PF limit introduced cable degradation and decrease of critical current. Bending tests applied to cables showed that critical current degradation starts below the bending diameter 120 mm for 6-filaments Cu sheath and 70 mm for single-core Cu10Ni sheath cable. Tensile tests showed similar irreversible strain values for the both types of cables. Rutherford cables assembled of single-core strands are promising for low field (2.7-4 T) applications where low bending diameters are required.

  1. A Balance of Capping Protein and Profilin Functions Is Required to Regulate Actin Polymerization in Drosophila Bristle

    PubMed Central

    Hopmann, Roberta; Miller, Kathryn G.

    2003-01-01

    Profilin is a well-characterized protein known to be important for regulating actin filament assembly. Relatively few studies have addressed how profilin interacts with other actin-binding proteins in vivo to regulate assembly of complex actin structures. To investigate the function of profilin in the context of a differentiating cell, we have studied an instructive genetic interaction between mutations in profilin (chickadee) and capping protein (cpb). Capping protein is the principal protein in cells that caps actin filament barbed ends. When its function is reduced in the Drosophila bristle, F-actin levels increase and the actin cytoskeleton becomes disorganized, causing abnormal bristle morphology. chickadee mutations suppress the abnormal bristle phenotype and associated abnormalities of the actin cytoskeleton seen in cpb mutants. Furthermore, overexpression of profilin in the bristle mimics many features of the cpb loss-of-function phenotype. The interaction between cpb and chickadee suggests that profilin promotes actin assembly in the bristle and that a balance between capping protein and profilin activities is important for the proper regulation of F-actin levels. Furthermore, this balance of activities affects the association of actin structures with the membrane, suggesting a link between actin filament dynamics and localization of actin structures within the cell. PMID:12529431

  2. Cable equation for general geometry.

    PubMed

    López-Sánchez, Erick J; Romero, Juan M

    2017-02-01

    The cable equation describes the voltage in a straight cylindrical cable, and this model has been employed to model electrical potential in dendrites and axons. However, sometimes this equation might give incorrect predictions for some realistic geometries, in particular when the radius of the cable changes significantly. Cables with a nonconstant radius are important for some phenomena, for example, discrete swellings along the axons appear in neurodegenerative diseases such as Alzheimers, Parkinsons, human immunodeficiency virus associated dementia, and multiple sclerosis. In this paper, using the Frenet-Serret frame, we propose a generalized cable equation for a general cable geometry. This generalized equation depends on geometric quantities such as the curvature and torsion of the cable. We show that when the cable has a constant circular cross section, the first fundamental form of the cable can be simplified and the generalized cable equation depends on neither the curvature nor the torsion of the cable. Additionally, we find an exact solution for an ideal cable which has a particular variable circular cross section and zero curvature. For this case we show that when the cross section of the cable increases the voltage decreases. Inspired by this ideal case, we rewrite the generalized cable equation as a diffusion equation with a source term generated by the cable geometry. This source term depends on the cable cross-sectional area and its derivates. In addition, we study different cables with swelling and provide their numerical solutions. The numerical solutions show that when the cross section of the cable has abrupt changes, its voltage is smaller than the voltage in the cylindrical cable. Furthermore, these numerical solutions show that the voltage can be affected by geometrical inhomogeneities on the cable.

  3. Cable equation for general geometry

    NASA Astrophysics Data System (ADS)

    López-Sánchez, Erick J.; Romero, Juan M.

    2017-02-01

    The cable equation describes the voltage in a straight cylindrical cable, and this model has been employed to model electrical potential in dendrites and axons. However, sometimes this equation might give incorrect predictions for some realistic geometries, in particular when the radius of the cable changes significantly. Cables with a nonconstant radius are important for some phenomena, for example, discrete swellings along the axons appear in neurodegenerative diseases such as Alzheimers, Parkinsons, human immunodeficiency virus associated dementia, and multiple sclerosis. In this paper, using the Frenet-Serret frame, we propose a generalized cable equation for a general cable geometry. This generalized equation depends on geometric quantities such as the curvature and torsion of the cable. We show that when the cable has a constant circular cross section, the first fundamental form of the cable can be simplified and the generalized cable equation depends on neither the curvature nor the torsion of the cable. Additionally, we find an exact solution for an ideal cable which has a particular variable circular cross section and zero curvature. For this case we show that when the cross section of the cable increases the voltage decreases. Inspired by this ideal case, we rewrite the generalized cable equation as a diffusion equation with a source term generated by the cable geometry. This source term depends on the cable cross-sectional area and its derivates. In addition, we study different cables with swelling and provide their numerical solutions. The numerical solutions show that when the cross section of the cable has abrupt changes, its voltage is smaller than the voltage in the cylindrical cable. Furthermore, these numerical solutions show that the voltage can be affected by geometrical inhomogeneities on the cable.

  4. Optimization of cable preloading on cable-stayed bridges

    NASA Astrophysics Data System (ADS)

    Wang, Yang Cheng; Vlahinos, Andreas S.; Shu, HungShan

    1997-05-01

    Generally, geometric nonlinearities of cable-stayed bridges depend on the behaviors of cables, pylons, the bridge deck and their interactions. These are geometry change, cable sag, and the interactions of axial forces, the bending moment and their deformations in the pylons and bridge deck. Therefore, a large cable-stayed bridges system having a large number of cables can be analyzed under different load conditions. In investigating nonlinear behaviors of cable- stayed bridges, the nonlinear behavior of cables needs to be considered because it may cause the nonlinear behavior of whole bridge system. The nonlinear behavior of a cable gained from its sag. With an increasing axial load, the elongation of the cable is increased but the total cable sag is decreased. Cable-stayed bridge uses cables instead of the internal piers to support the bridge deck. Usually, cable- stayed bridge decks are straight with a little camber compared to the total length of the bridge. Keeping the bridge deck in the position where is the designer desired is not only for bridge aesthetics but also for people on the bridge in terms of psychological effect of improving confidence in structure and engineering considerations. To achieve the serviceability and engineering requirements, preloading of the cable is necessary. In this paper, one such a bridge with geometry similarly to an existing cable- stayed bridge. Quincy Bayview Bridge, located in Illinois, USA, has been considered. Quincy Bayview Bridge has 58 cables in the two planes. Four methods have been considered in this paper to make the optimum selection of cable preloading. The objective is to select appropriate method to determine cable prestrains in order to minimize the deformations and stresses due to dead load of the bridge. Thus, it is not a trivial problem since a change in the prestress of a cable influence the deformation every where in the structure. The best method would be determined by comparing the calculated bending and

  5. Infiniband Based Cable Comparison

    SciTech Connect

    Minich, Makia

    2007-07-01

    As Infiniband continues to be more broadly adopted in High Performance Computing (HPC) and datacenter applications, one major challenge still plagues implementation: cabling. With the transition to DDR (double data rate) from SDR (single datarate), currently available Infiniband implementations such as standard CX4/IB4x style copper cables severely constrain system design (10m maximum length for DDR copper cables, thermal management due to poor airflow, etc.). This paper will examine some of the options available and compare performance with the newly released Intel Connects Cables. In addition, we will take a glance at Intel's dual-core and quad-core systems to see if core counts have noticeable effect on expected IO patterns.

  6. The Discrete Hanging Cable

    ERIC Educational Resources Information Center

    Peters, James V.

    2004-01-01

    Using the methods of finite difference equations the discrete analogue of the parabolic and catenary cable are analysed. The fibonacci numbers and the golden ratio arise in the treatment of the catenary.

  7. Robotic Arm Biobarrier Cable

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This image, taken by the Surface Stereo Imager on NASA's Phoenix Mars Lander on the 14th Martian day of the mission (June 7, 2008), shows the cable that held the Robotic Arm's biobarrier in place during flight has snapped. The cable's springs retracted to release the biobarrier right after landing.

    To the lower right of the image a spring is visible. Extending from that spring is a length of cable that snapped during the biobarrier's release. A second spring separated from the cable when it snapped and has been photographed on the ground under the lander near one of the legs.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  8. AC Cable: Yokohama Project

    NASA Astrophysics Data System (ADS)

    Masuda, Takato

    High Temperature Superconducting (HTS) cables can transmit large amounts of electricity in a compact size with minimal losses. Therefore, they are expected to save the construction cost of underground lines in urban areas and decrease transmission losses. Several HTS cables have recently been demonstrated in networks around the world, and full-scale commercialization is expected in the near future. In Japan, the development of compact HTS cables suitable for urban deployment has been underway since the early 1990s. In 2007, a national project was started to verify their operational performance and long-term reliability in the grid. An HTS cable 240 m long was installed at the Asahi substation of the Tokyo Electric Power Company (TEPCO) in Yokohama; then a joint, terminations and cooling system was constructed in 2011. After successful performance tests, the cable was connected to the grid for the first time in Japan, and started to deliver electricity to 70,000 households in October 2012. This trouble-free in-grid service continued for over a year. We can conclude that the HTS cable system performs well and has the stability required for long-term in-grid operations.

  9. Actinic keratosis. Current treatment options.

    PubMed

    Jeffes, E W; Tang, E H

    2000-01-01

    Actinic keratoses are hyperkeratotic skin lesions that represent focal abnormal proliferation of epidermal keratinocytes. Some actinic keratoses evolve into squamous cell carcinoma of the skin, while others resolve spontaneously. The conversion rate of actinic keratosis to squamous cell carcinoma is not accurately known, but appears to be in the range of 0.25 to 1% per year. Although there is a low rate of conversion of actinic keratoses to squamous cell carcinoma, 60% of squamous cell carcinomas of the skin probably arise from actinic keratoses. The main cause of actinic keratoses in otherwise healthy Caucasians appears to be the sun. Therapy for actinic keratoses begins with prevention which starts with sun avoidance and physical protection. Sunprotection with sunscreens actually slows the return of actinic keratoses in patients already getting actinic keratoses. Interestingly, a few studies are available that demonstrate that a high fat diet is associated with the production of more actinic keratoses than is a low fat diet. One of the mainstays of therapy has been local destruction of the actinic keratoses with cryotherapy, and curettage and electrodesiccation. A new addition to this group of therapies to treat individual actinic keratoses is photodynamic therapy with topical aminolevulinic acid and light. In patients who have numerous actinic keratoses in an area of severely sun damaged skin, therapies which are applied to the whole actinic keratosis area are used. The goal of treating such an area of skin is to treat all of the early as well as the numerous clinically evident actinic keratoses at the same time. The classical approaches for treating areas of photodamaged skin without treating actinic keratoses individually include: the use of topically applied fluorouracil cream, dermabrasion, and cutaneous peels with various agents like trichloroacetic acid. Both topically as well as orally administered retinoids have been used to treat actinic keratoses but

  10. An actin-binding protein, LlLIM1, mediates calcium and hydrogen regulation of actin dynamics in pollen tubes.

    PubMed

    Wang, Huei-Jing; Wan, Ai-Ru; Jauh, Guang-Yuh

    2008-08-01

    Actin microfilaments are crucial for polar cell tip growth, and their configurations and dynamics are regulated by the actions of various actin-binding proteins (ABPs). We explored the function of a lily (Lilium longiflorum) pollen-enriched LIM domain-containing protein, LlLIM1, in regulating the actin dynamics in elongating pollen tube. Cytological and biochemical assays verified LlLIM1 functioning as an ABP, promoting filamentous actin (F-actin) bundle assembly and protecting F-actin against latrunculin B-mediated depolymerization. Overexpressed LlLIM1 significantly disturbed pollen tube growth and morphology, with multiple tubes protruding from one pollen grain and coaggregation of FM4-64-labeled vesicles and Golgi apparatuses at the subapex of the tube tip. Moderate expression of LlLIM1 induced an oscillatory formation of asterisk-shaped F-actin aggregates that oscillated with growth period but in different phases at the subapical region. These results suggest that the formation of LlLIM1-mediated overstabilized F-actin bundles interfered with endomembrane trafficking to result in growth retardation. Cosedimentation assays revealed that the binding affinity of LlLIM1 to F-actin was simultaneously regulated by both pH and Ca(2+): LlLIM1 showed a preference for F-actin binding under low pH and low Ca(2+) concentration. The potential functions of LlLIM1 as an ABP sensitive to pH and calcium in integrating endomembrane trafficking, oscillatory pH, and calcium circumstances to regulate tip-focused pollen tube growth are discussed.

  11. Recruitment Kinetics of Tropomyosin Tpm3.1 to Actin Filament Bundles in the Cytoskeleton Is Independent of Actin Filament Kinetics

    PubMed Central

    Appaduray, Mark A.; Masedunskas, Andrius; Lucas, Christine A.; Warren, Sean C.; Timpson, Paul; Stear, Jeffrey H.

    2016-01-01

    The actin cytoskeleton is a dynamic network of filaments that is involved in virtually every cellular process. Most actin filaments in metazoa exist as a co-polymer of actin and tropomyosin (Tpm) and the function of an actin filament is primarily defined by the specific Tpm isoform associated with it. However, there is little information on the interdependence of these co-polymers during filament assembly and disassembly. We addressed this by investigating the recovery kinetics of fluorescently tagged isoform Tpm3.1 into actin filament bundles using FRAP analysis in cell culture and in vivo in rats using intracellular intravital microscopy, in the presence or absence of the actin-targeting drug jasplakinolide. The mobile fraction of Tpm3.1 is between 50% and 70% depending on whether the tag is at the C- or N-terminus and whether the analysis is in vivo or in cultured cells. We find that the continuous dynamic exchange of Tpm3.1 is not significantly impacted by jasplakinolide, unlike tagged actin. We conclude that tagged Tpm3.1 may be able to undergo exchange in actin filament bundles largely independent of the assembly and turnover of actin. PMID:27977753

  12. The centrosome is an actin-organizing center

    PubMed Central

    Farina, Francesca; Gaillard, Jérémie; Guérin, Christophe; Couté, Yohann; Sillibourne, James; Blanchoin, Laurent; Théry, Manuel

    2016-01-01

    Microtubules and actin filaments are the two main cytoskeleton networks supporting intracellular architecture and cell polarity. The centrosome nucleates and anchors microtubules and is therefore considered to be the main microtubule-organizing center. However, recurring, yet unexplained, observations have pointed towards a connection between the centrosome and actin filaments. Here we have used isolated centrosomes to demonstrate that the centrosome can directly promote actin filament assembly. A cloud of centrosome-associated actin filaments could be identified in living cells as well. Actin-filament nucleation at the centrosome was mediated by the nucleation promoting factor WASH in combination with the Arp2/3 complex. Pericentriolar material 1 (PCM1) appeared to modulate the centrosomal actin network by regulating Arp2/3 complex and WASH recruitment to the centrosome. Hence our results reveal an additional facet of the centrosome as an intracellular organizer and provide mechanistic insights into how the centrosome can function as an actin filament-organizing center. PMID:26655833

  13. Induction of anti-actin drug resistance in Tetrahymena.

    PubMed

    Zackroff, Robert V; Hufnagel, Linda A

    2002-01-01

    Both cytochalasin D and latrunculin B reversibly inhibited Tetrahymena phagocytosis at concentrations similar to those effective in mammalian systems, even though ciliate actins are known to be highly divergent from mammalian actins. Overnight exposure to relatively low (0.25 microM) concentrations of latrunculin B induced resistance in Tetrahymena to the inhibitory effects of that drug, as well as cross-resistance to cytochalasin D. However, much higher (> 30 microM) concentrations of cytochalasin D were required for induction of cross-resistance to latrunculin B. Anti-actin drug resistance in Tetrahymena may involve a general multidrug resistance mechanism and/or specific feedback regulation of F-actin assembly and stability.

  14. Lamellipodial actin mechanically links myosin activity with adhesion site formation

    PubMed Central

    Giannone, Gregory; Dubin-Thaler, Benjamin; Rossier, Olivier; Cai, Yunfei; Chaga, Oleg; Jiang, Guoying; Beaver, William; Döbereiner, Hans-Günther; Freund, Yoav; Borisy, Gary; Sheetz, Michael P.

    2013-01-01

    Summary Cell motility proceeds by cycles of edge protrusion, adhesion and retraction. Whether these functions are coordinated by biochemical or biomechanical processes is unknown. We find that myosin II pulls the rear of the lamellipodial actin network, causing upward bending, edge retraction and initiation of new adhesion sites. The network then separates from the edge and condenses over the myosin. Protrusion resumes as lamellipodial actin regenerates from the front and extends rearward until it reaches newly assembled myosin, initiating the next cycle. Upward bending, observed by evanescence and electron microscopy, results in ruffle formation when adhesion strength is low. Correlative fluorescence and electron microscopy shows that the regenerating lamellipodium forms a cohesive, separable layer of actin above the lamellum. Thus, actin polymerization periodically builds a mechanical link, the lamellipodium, connecting myosin motors with the initiation of adhesion sites, suggesting that the major functions driving motility are coordinated by a biomechanical process. PMID:17289574

  15. Fiber optical cable and connector system (FOCCoS) for PFS/ Subaru

    NASA Astrophysics Data System (ADS)

    de Oliveira, Antonio Cesar; de Oliveira, Lígia Souza; de Arruda, Marcio V.; Souza Marrara, Lucas; dos Santos, Leandro H.; Ferreira, Décio; dos Santos, Jesulino B.; Rosa, Josimar A.; Junior, Orlando V.; Pereira, Jeferson M.; Castilho, Bruno; Gneiding, Clemens; Junior, Laerte S.; de Oliveira, Claudia M.; Gunn, James; Ueda, Akitoshi; Takato, Naruhisa; Shimono, Atsushi; Sugai, Hajime; Karoji, Hiroshi; Kimura, Masahiko; Tamura, Naoyuki; Wang, Shiang-Yu; Murray, Graham; Le Mignant, David; Madec, Fabrice; Jaquet, Marc; Vives, Sebastien; Fisher, Charlie; Braun, David; Schwochert, Mark; Reiley, Daniel J.

    2014-07-01

    FOCCoS, "Fiber Optical Cable and Connector System" has the main function of capturing the direct light from the focal plane of Subaru Telescope using optical fibers, each one with a microlens in its tip, and conducting this light through a route containing connectors to a set of four spectrographs. The optical fiber cable is divided in 3 different segments called Cable A, Cable B and Cable C. Multi-fibers connectors assure precise connection among all optical fibers of the segments, providing flexibility for instrument changes. To assure strong and accurate connection, these sets are arranged inside two types of assemblies: the Tower Connector, for connection between Cable C and Cable B; and the Gang Connector, for connection between Cable B and Cable A. Throughput tests were made to evaluate the efficiency of the connections. A lifetime test connection is in progress. Cable C is installed inside the PFI, Prime Focus Instrument, where each fiber tip with a microlens is bonded to the end of the shaft of a 2-stage piezo-electric rotatory motor positioner; this assembly allows each fiber to be placed anywhere within its patrol region, which is 9.5mm diameter.. Each positioner uses a fiber arm to support the ferrule, the microlens, and the optical fiber. 2400 of these assemblies are arranged on a motor bench plate in a hexagonal-closed-packed disposition. All optical fibers from Cable C, protected by tubes, pass through the motors' bench plate, three modular plates and a strain relief box, terminating at the Tower Connector. Cable B is permanently installed at Subaru Telescope structure, as a link between Cable C and Cable A. This cable B starts at the Tower Connector device, placed on a lateral structure of the telescope, and terminates at the Gang Connector device. Cable B will be routed to minimize the compression, torsion and bending caused by the cable weight and telescope motion. In the spectrograph room, Cable A starts at the Gang Connector, crosses a

  16. Actin stress in cell reprogramming

    PubMed Central

    Guo, Jun; Wang, Yuexiu; Sachs, Frederick; Meng, Fanjie

    2014-01-01

    Cell mechanics plays a role in stem cell reprogramming and differentiation. To understand this process better, we created a genetically encoded optical probe, named actin–cpstFRET–actin (AcpA), to report forces in actin in living cells in real time. We showed that stemness was associated with increased force in actin. We reprogrammed HEK-293 cells into stem-like cells using no transcription factors but simply by softening the substrate. However, Madin-Darby canine kidney (MDCK) cell reprogramming required, in addition to a soft substrate, Harvey rat sarcoma viral oncogene homolog expression. Replating the stem-like cells on glass led to redifferentiation and reduced force in actin. The actin force probe was a FRET sensor, called cpstFRET (circularly permuted stretch sensitive FRET), flanked by g-actin subunits. The labeled actin expressed efficiently in HEK, MDCK, 3T3, and bovine aortic endothelial cells and in multiple stable cell lines created from those cells. The viability of the cell lines demonstrated that labeled actin did not significantly affect cell physiology. The labeled actin distribution was similar to that observed with GFP-tagged actin. We also examined the stress in the actin cross-linker actinin. Actinin force was not always correlated with actin force, emphasizing the need for addressing protein specificity when discussing forces. Because actin is a primary structural protein in animal cells, understanding its force distribution is central to understanding animal cell physiology and the many linked reactions such as stress-induced gene expression. This new probe permits measuring actin forces in a wide range of experiments on preparations ranging from isolated proteins to transgenic animals. PMID:25422450

  17. Instrumentation Cables Test Plan

    SciTech Connect

    Muna, Alice Baca; LaFleur, Chris Bensdotter

    2016-10-01

    A fire at a nuclear power plant (NPP) has the potential to damage structures, systems, and components important to safety, if not promptly detected and suppressed. At Browns Ferry Nuclear Power Plant on March 22, 1975, a fire in the reactor building damaged electrical power and control systems. Damage to instrumentation cables impeded the function of both normal and standby reactor coolant systems, and degraded the operators’ plant monitoring capability. This event resulted in additional NRC involvement with utilities to ensure that NPPs are properly protected from fire as intended by the NRC principle design criteria (i.e., general design criteria 3, Fire Protection). Current guidance and methods for both deterministic and performance based approaches typically make conservative (bounding) assumptions regarding the fire-induced failure modes of instrumentation cables and those failure modes effects on component and system response. Numerous fire testing programs have been conducted in the past to evaluate the failure modes and effects of electrical cables exposed to severe thermal conditions. However, that testing has primarily focused on control circuits with only a limited number of tests performed on instrumentation circuits. In 2001, the Nuclear Energy Institute (NEI) and the Electric Power Research Institute (EPRI) conducted a series of cable fire tests designed to address specific aspects of the cable failure and circuit fault issues of concern1. The NRC was invited to observe and participate in that program. The NRC sponsored Sandia National Laboratories to support this participation, whom among other things, added a 4-20 mA instrumentation circuit and instrumentation cabling to six of the tests. Although limited, one insight drawn from those instrumentation circuits tests was that the failure characteristics appeared to depend on the cable insulation material. The results showed that for thermoset insulated cables, the instrument reading tended to drift

  18. Cable-Dispensing Cart

    NASA Technical Reports Server (NTRS)

    Bredberg, Alan S.

    2003-01-01

    A versatile cable-dispensing cart can support as many as a few dozen reels of cable, wire, and/or rope. The cart can be adjusted to accommodate reels of various diameters and widths, and can be expanded, contracted, or otherwise reconfigured by use of easily installable and removable parts that can be carried onboard. Among these parts are dispensing rods and a cable guide that enables dispensing of cables without affecting the direction of pull. Individual reels can be mounted on or removed from the cart without affecting the other reels: this feature facilitates the replacement or reuse of partially depleted reels, thereby helping to reduce waste. Multiple cables, wires, or ropes can be dispensed simultaneously. For maneuverability, the cart is mounted on three wheels. Once it has been positioned, the cart is supported by rubber mounts for stability and for prevention of sliding or rolling during dispensing operations. The stability and safety of the cart are enhanced by a low-center-of-gravity design. The cart can readily be disassembled into smaller units for storage or shipping, then reassembled in the desired configuration at a job site.

  19. Direct actin binding to A- and B-type lamin tails and actin filament bundling by the lamin A tail

    PubMed Central

    Simon, Dan N; Zastrow, Michael S

    2010-01-01

    by which lamins, particularly lamin A, might impact the concentration of free actin in the nucleus or pathways including transcription, nuclear export, chromatin remodeling, chromatin movement and nuclear assembly that require nuclear myosin 1c and polymerizable actin. PMID:21327074

  20. Hypervelocity impact testing of cables

    NASA Technical Reports Server (NTRS)

    Jex, D. W.; Adkinson, A. B.; English, J. E.; Linebaugh, C. E.

    1973-01-01

    The physics and electrical results obtained from simulated micrometeoroid testing of certain Skylab cables are presented. The test procedure, electrical circuits, test equipment, and cable types utilized are also explained.

  1. And the dead shall rise: Actin and myosin return to the spindle

    PubMed Central

    Sandquist, Joshua C.; Kita, Angela M.; Bement, William M.

    2011-01-01

    The spindle directs chromosome partitioning in eukaryotes and, for the last three decades, has been considered primarily a structure based on microtubules, microtubule motors, and other microtubule binding proteins. However, a surprisingly large body of both old and new studies suggests roles for actin filaments (F-actin) and myosins (F-actin-based motor proteins) in spindle assembly and function. Here we review these data, and conclude that in several cases the evidence for F-actin and myosins participation in spindle function is very strong, and in the situations where it is less strong, there is nevertheless enough evidence to warrant further investigation. PMID:21920311

  2. Coaxial cable cutter

    DOEpatents

    Hall, Leslie C.; Hedges, Robert S.

    1990-04-10

    A cutting device is provided which is useful in trimming the jackets from semi-rigid coaxial cables and wire having a cutting bit and support attached to movable jaws. A thumbpiece is provided to actuate the opening of the jaws for receiving the cable to be trimmed, and a spring member is provided to actuate the closing of the jaws when thumbpiece is released. The cutting device utilizes one moving part during the cutting operation by using a rolling cut action. The nature of the jaws allows the cutting device to work in space having clearances less than 0.160 inches.

  3. A cable SGEMP tutorial :

    SciTech Connect

    Liscum-Powell, Jennifer L.; Bohnhoff, William J.; Turner, C. David

    2007-05-01

    This tutorial is aimed at guiding a user through the process of performing a cable SGEMP simulation. The tutorial starts with processing a differential photon spectrum obtained from a Monte Carlo code such as ITS into a discrete (multi-group) spectrum used in CEPXS and CEPTRE. Guidance is given in the creation of a nite element mesh of the cable geometry. The set-up of a CEPTRE simulation is detailed. Users are instructed in evaluating the quality of the CEPTRE radiation transport results. The post-processing of CEPTRE results using Exostrip is detailed. And finally, an EMPHASIS/CABANA simulation is detailed including the interpretation of the output.

  4. Direct observation of motion of single F-actin filaments in the presence of myosin

    NASA Astrophysics Data System (ADS)

    Yanagida, Toshio; Nakase, Michiyuki; Nishiyama, Katsumi; Oosawa, Fumio

    1984-01-01

    Actin is found in almost all kinds of non-muscle cells where it is thought to have an important role in cell motility. A proper understanding of that role will only be possible when reliable in vitro systems are available for investigating the interaction of cellular actin and myosin. A start has been made on several systems1-4, most recently by Sheetz and Spudich who demonstrated unidirectional movement of HMM-coated beads along F-actin cables on arrays of chloroplasts exposed by dissection of a Nitella cell5. As an alternative approach, we report here the direct observation by fluorescence microscopy of the movements of single F-actin filaments interacting with soluble myosin fragments energized by Mg2+-ATP.

  5. George W. Cable and Tradition.

    ERIC Educational Resources Information Center

    Trotman, C. James

    There have been no critical studies of Cable's fiction treated for its own sake; and, without such studies, readers may not become aware of these stories or of their possible value. The absence of a critical position on Cable is due to the decline in his reputation as an artist when he became a writer of popular literature. Before 1925 Cable and…

  6. High Temperature Superconducting Underground Cable

    SciTech Connect

    Farrell, Roger, A.

    2010-02-28

    The purpose of this Project was to design, build, install and demonstrate the technical feasibility of an underground high temperature superconducting (HTS) power cable installed between two utility substations. In the first phase two HTS cables, 320 m and 30 m in length, were constructed using 1st generation BSCCO wire. The two 34.5 kV, 800 Arms, 48 MVA sections were connected together using a superconducting joint in an underground vault. In the second phase the 30 m BSCCO cable was replaced by one constructed with 2nd generation YBCO wire. 2nd generation wire is needed for commercialization because of inherent cost and performance benefits. Primary objectives of the Project were to build and operate an HTS cable system which demonstrates significant progress towards commercial progress and addresses real world utility concerns such as installation, maintenance, reliability and compatibility with the existing grid. Four key technical areas addressed were the HTS cable and terminations (where the cable connects to the grid), cryogenic refrigeration system, underground cable-to-cable joint (needed for replacement of cable sections) and cost-effective 2nd generation HTS wire. This was the world’s first installation and operation of an HTS cable underground, between two utility substations as well as the first to demonstrate a cable-to-cable joint, remote monitoring system and 2nd generation HTS.

  7. Economical Aspects of Superconducting Cable

    NASA Astrophysics Data System (ADS)

    Ohya, Masayoshi

    High-temperature superconducting (HTS) cables are expected to resolve technical problems with power grids because they put large-capacity, low-loss power transmission into a compact package. One problem is replacing old 275-kV oil filled (OF) cables with cross-linked polyethylene insulated vinyl sheath cables (XLPE cables). This is difficult because XLPE cable has a lower transmission capacity than OF cable. In addition, the high concentration of public infrastructure underground makes it extremely difficult to build new ones. However, if 66-kV HTS cables can be installed inside existing underground conduits and can achieve a power capacity equivalent to conventional 275-kV cables, construction costs could be significantly reduced. Moreover, if XLPE cables are used for a 1,000 MVA-class transmission line, then three circuits of nine 275-kV single-core cables would be required, which would incur a transmission loss of 90 W/m/cct. Three circuits of three 66-kV Three-in-One HTS cables, however, with an AC loss of 1 W/m/ph@3 kA, heat invasion of 2 W/m, and cooling system efficiency of 0.1, would reduce transmission loss to less than three-fifths that of XLPE cables.

  8. A mitochondria-anchored isoform of the actin-nucleating spire protein regulates mitochondrial division

    PubMed Central

    Manor, Uri; Bartholomew, Sadie; Golani, Gonen; Christenson, Eric; Kozlov, Michael; Higgs, Henry; Spudich, James; Lippincott-Schwartz, Jennifer

    2015-01-01

    Mitochondrial division, essential for survival in mammals, is enhanced by an inter-organellar process involving ER tubules encircling and constricting mitochondria. The force for constriction is thought to involve actin polymerization by the ER-anchored isoform of the formin protein inverted formin 2 (INF2). Unknown is the mechanism triggering INF2-mediated actin polymerization at ER-mitochondria intersections. We show that a novel isoform of the formin-binding, actin-nucleating protein Spire, Spire1C, localizes to mitochondria and directly links mitochondria to the actin cytoskeleton and the ER. Spire1C binds INF2 and promotes actin assembly on mitochondrial surfaces. Disrupting either Spire1C actin- or formin-binding activities reduces mitochondrial constriction and division. We propose Spire1C cooperates with INF2 to regulate actin assembly at ER-mitochondrial contacts. Simulations support this model's feasibility and demonstrate polymerizing actin filaments can induce mitochondrial constriction. Thus, Spire1C is optimally positioned to serve as a molecular hub that links mitochondria to actin and the ER for regulation of mitochondrial division. DOI: http://dx.doi.org/10.7554/eLife.08828.001 PMID:26305500

  9. A mitochondria-anchored isoform of the actin-nucleating spire protein regulates mitochondrial division.

    PubMed

    Manor, Uri; Bartholomew, Sadie; Golani, Gonen; Christenson, Eric; Kozlov, Michael; Higgs, Henry; Spudich, James; Lippincott-Schwartz, Jennifer

    2015-08-25

    Mitochondrial division, essential for survival in mammals, is enhanced by an inter-organellar process involving ER tubules encircling and constricting mitochondria. The force for constriction is thought to involve actin polymerization by the ER-anchored isoform of the formin protein inverted formin 2 (INF2). Unknown is the mechanism triggering INF2-mediated actin polymerization at ER-mitochondria intersections. We show that a novel isoform of the formin-binding, actin-nucleating protein Spire, Spire1C, localizes to mitochondria and directly links mitochondria to the actin cytoskeleton and the ER. Spire1C binds INF2 and promotes actin assembly on mitochondrial surfaces. Disrupting either Spire1C actin- or formin-binding activities reduces mitochondrial constriction and division. We propose Spire1C cooperates with INF2 to regulate actin assembly at ER-mitochondrial contacts. Simulations support this model's feasibility and demonstrate polymerizing actin filaments can induce mitochondrial constriction. Thus, Spire1C is optimally positioned to serve as a molecular hub that links mitochondria to actin and the ER for regulation of mitochondrial division.

  10. Feedback Interactions of Polymerized Actin with the Cell Membrane: Waves, Pulses, and Oscillations

    NASA Astrophysics Data System (ADS)

    Carlsson, Anders

    Polymerized filaments of the protein actin have crucial functions in cell migration, and in bending the cell membrane to drive endocytosis or the formation of protrusions. The nucleation and polymerization of actin filaments are controlled by upstream agents in the cell membrane, including nucleation-promoting factors (NPFs) that activate the Arp2/3 complex to form new branches on pre-existing filaments. But polymerized actin (F-actin) also feeds back on the assembly of NPFs. We explore the effects of the resulting feedback loop of F-actin and NPFs on two phenomena: actin pulses that drive endocytosis in yeast, and actin waves traveling along the membrane of several cell types. In our model of endocytosis in yeast, the actin network is grown explicitly in three dimensions, exerts a negative feedback interaction on localized patch of NPFs in the membrane, and bends the membrane by exerting a distribution of forces. This model explains observed actin and NPF pulse dynamics, and the effects of several interventions including i) NPF mutations, ii) inhibition of actin polymerization, and iii) deletion of a protein that allows F-actin to bend the cell membrane. The model predicts that mutation of the active region of an NPF will enhance the accumulation of that NPF, and we confirm this prediction by quantitative fluorescence microscopy. For actin waves, we treat a similar model, with NPFs distributed over a larger region of the cell membrane. This model naturally generates actin waves, and predicts a transition from wave behavior to spatially localized oscillations when NPFs are confined to a small region. We also predict a transition from waves to static polarization as the negative-feedback coupling between F-actin and the NPFs is reduced. Supported by NIGMS Grant R01 GM107667.

  11. Cables and connectors for Large Space System Technology (LSST)

    NASA Technical Reports Server (NTRS)

    Dunbar, W. G.

    1980-01-01

    The effect of the environment and extravehicular activity/remote assembly operations on the cables and connectors for spacecraft with metallic and/or nonmetallic structures was examined. Cable and connector philosophy was outlined for the electrical systems and electronic compartments which contain high-voltage, high-power electrical and electronic equipment. The influence of plasma and particulates on the system is analyzed and the effect of static buildup on the spacecraft electrical system discussed. Conceptual cable and connector designs are assessed for capability to withstand high current and high voltage without danger of arcs and electromagnetic interference. The extravehicular activites required of the space station and/or supply spacecraft crew members to join and inspect the electrical system, using manual or remote assembly construction are also considered.

  12. Pediatrics and Cable Television.

    ERIC Educational Resources Information Center

    Wallerstein, Edward; And Others

    The Department of Community Medicine of the Mount Sinai School of Medicine (New York City), in cooperation with the TelePrompTer Corporation and with funding from the Health Services and Mental Health Administration of the Department of Health, Education, and Welfare, has developed a bidirectional television system using coaxial cable which links…

  13. Cable indenter aging monitor

    SciTech Connect

    Shook, T.A.; Gardner, J.B.

    1988-07-01

    This project was undertaken to develop a hand-held, nondestructive test device to assess the aged condition of electrical cable by in situ measurement of mechanical properties of polymeric jackets and insulations. The device is an indenter similar to those used to make hardness measurements. Comparison of measurements made on installed cables with previous measurements serving as baseline aging/mechanical property data will determine the state of aging of the field cables. Such a device will be valuable in nuclear and fossil plant life extension programs. Preliminary laboratory tests on cables covered with ethylene propylene rubber (EPR) and chlorosulfated polyethylene (CSPE) point to the measurement of the rate of force increase resulting from constant rate deformation as having the best correlation with progressive thermal aging. This first phase of the work has demonstrated the technical feasibility of the method. A second phase will include the generation of additional groundwork data and the design of the portable indenter for in situ plant measurements.

  14. Cable TV: Now What?

    ERIC Educational Resources Information Center

    Ohio Educational Library/Media Association, Columbus.

    Designed to aid in planning the best use of cable television in a particular educational situation, this pamphlet was prepared by a joint committee of the Ohio Educational Library Media Association and the Greater Miami Valley Instructional Television Council in order to share their plans, experiences, problems, and solutions with others who are…

  15. Lightweight Electric Power Cable.

    DTIC Science & Technology

    1982-09-01

    8I~ .4 111 162 MICROCi Pi RL’ LUHION TESI CHARI "LIGHTWEIGHT ELECTRIC POWER CABLE" FINAL TECHNICAL REPORT SEPTEMBER 30, 1981 to SEPTEMBER 30, 1982... Vulcanized by heat to crosslink. TPE (Thermoplastic Elastomer) - Polymers having elastomeric proper- ties. Used as thermoplastics - melt formed by

  16. Multilayer flat electrical cable

    NASA Technical Reports Server (NTRS)

    Silverman, P. G.

    1973-01-01

    Flat electrical cable is lightweight, flexible over wide temperature range, withstands continuous exposure to high levels of nuclear radiation, and can carry high currents with minimum of temperature rise. Its magnetic cleanliness is equal to or better than twisted pair of wires, and it can be terminated in conventional electrical connector.

  17. Comparison of cable ageing

    NASA Astrophysics Data System (ADS)

    Plaček, Vít; Kohout, Tomáš

    2010-03-01

    Two cable types, which currently are used in nuclear power plants (NPP) and which are composed by jacket/insulation materials, i.e. PVC/PVC and PVC/PE, were exposed to accelerated ageing conditions, in order to simulate their behavior after 10 years in service. The cables were aged under two different test conditions: With relatively high accelerating ageing speed:Radiation ageing was carried out at room temperature at a dose rate of 2900 Gy/h, followed by thermal ageing at 100 °C. This accelerated ageing condition was fairly fast, but still in compliance with the standards. With moderate ageing speed:The radiation and thermal ageing was performed simultaneously (superimposed) at a dose rate of 2.7-3.7Gy/h and a temperature of 68-70 °C. Such a test condition seems to be very close to the radiation and temperature impact onto the cables in the real NPP service. Finally, mechanical properties were measured to characterize the ageing status of the cables. The purpose of this study was to compare degradation effects, derived from both ageing methods, and to demonstrate that results obtained from high values of accelerating parameters and from fast ageing simulation can be very different from reality. The observed results corroborated this assumption.

  18. Schools and Cable Television.

    ERIC Educational Resources Information Center

    National Education Association, Washington, DC. Educational Technology Div.

    The papers gathered here are designed to provide a foundation of background information for those charged with the responsibility of formulating school district goals regarding cable television (CATV) and of obtaining the necessary cooperation from the local CATV franchise operators to reach these goals. The position of the National Education…

  19. Superconducting Cable Termination

    DOEpatents

    Sinha, Uday K.; Tolbert, Jerry

    2005-08-30

    Disclosed is a termination that connects high temperature superconducting (HTS) cable immersed in pressurized liquid nitrogen to high voltage and neutral (shield) external bushings at ambient temperature and pressure. The termination consists of a splice between the HTS power (inner) and shield (outer) conductors and concentric copper pipes which are the conductors in the termination. There is also a transition from the dielectric tape insulator used in the HTS cable to the insulators used between and around the copper pipe conductors in the termination. At the warm end of the termination the copper pipes are connected via copper braided straps to the conventional warm external bushings which have low thermal stresses. This termination allows for a natural temperature gradient in the copper pipe conductors inside the termination which enables the controlled flashing of the pressurized liquid coolant (nitrogen) to the gaseous state. Thus the entire termination is near the coolant supply pressure and the high voltage and shield cold bushings, a highly stressed component used in most HTS cables, are eliminated. A sliding seal allows for cable contraction as it is cooled from room temperature to ˜72-82 K. Seals, static vacuum, and multi-layer superinsulation minimize radial heat leak to the environment.

  20. Urban Cable Systems.

    ERIC Educational Resources Information Center

    Mason, William F.; And Others

    Analysis of demographic, social, municipal and commercial characteristics of Washington, D.C., indicate that a sophisticated three-stage cable television (CATV) system could be economically viable. The first stage would provide one-way CATV service offering 30 video channels and local program origination at a monthly fee of $3.50. The second stage…

  1. Regulators of Actin Dynamics in Gastrointestinal Tract Tumors

    PubMed Central

    Steinestel, Konrad; Wardelmann, Eva; Hartmann, Wolfgang; Grünewald, Inga

    2015-01-01

    Reorganization of the actin cytoskeleton underlies cell migration in a wide variety of physiological and pathological processes, such as embryonic development, wound healing, and tumor cell invasion. It has been shown that actin assembly and disassembly are precisely regulated by intracellular signaling cascades that respond to changes in the cell microenvironment, ligand binding to surface receptors, or oncogenic transformation of the cell. Actin-nucleating and actin-depolymerizing (ANFs/ADFs) and nucleation-promoting factors (NPFs) regulate cytoskeletal dynamics at the leading edge of migrating cells, thereby modulating cell shape; these proteins facilitate cellular movement and mediate degradation of the surrounding extracellular matrix by secretion of lytic proteases, thus eliminating barriers for tumor cell invasion. Accordingly, expression and activity of these actin-binding proteins have been linked to enhanced metastasis and poor prognosis in a variety of malignancies. In this review, we will summarize what is known about expression patterns and the functional role of actin regulators in gastrointestinal tumors and evaluate first pharmacological approaches to prevent invasion and metastatic dissemination of malignant cells. PMID:26345720

  2. Self-organization of actin networks by a monomeric myosin

    PubMed Central

    Saczko-Brack, Dario; Warchol, Ewa; Rogez, Benoit; Kröss, Markus; Heissler, Sarah M.; Sellers, James R.; Batters, Christopher; Veigel, Claudia

    2016-01-01

    The organization of actomyosin networks lies at the center of many types of cellular motility, including cell polarization and collective cell migration during development and morphogenesis. Myosin-IXa is critically involved in these processes. Using total internal reflection fluorescence microscopy, we resolved actin bundles assembled by myosin-IXa. Electron microscopic data revealed that the bundles consisted of highly ordered lattices with parallel actin polarity. The myosin-IXa motor domains aligned across the network, forming cross-links at a repeat distance of precisely 36 nm, matching the helical repeat of actin. Single-particle image processing resolved three distinct conformations of myosin-IXa in the absence of nucleotide. Using cross-correlation of a modeled actomyosin crystal structure, we identified sites of additional mass, which can only be accounted for by the large insert in loop 2 exclusively found in the motor domain of class IX myosins. We show that the large insert in loop 2 binds calmodulin and creates two coordinated actin-binding sites that constrain the actomyosin interactions generating the actin lattices. The actin lattices introduce orientated tracks at specific sites in the cell, which might install platforms allowing Rho-GTPase–activating protein (RhoGAP) activity to be focused at a definite locus. In addition, the lattices might introduce a myosin-related, force-sensing mechanism into the cytoskeleton in cell polarization and collective cell migration. PMID:27956608

  3. Accelerated actin filament polymerization from microtubule plus-ends

    PubMed Central

    Henty-Ridilla, Jessica L.; Rankova, Aneliya; Eskin, Julian A.; Kenny, Katelyn; Goode, Bruce L.

    2016-01-01

    Microtubules govern actin network remodeling in a wide range of biological processes, yet the mechanisms underlying this cytoskeletal crosstalk have remained obscure. Here we used single-molecule fluorescence microscopy to show that the microtubule plus-end associated protein CLIP-170 binds tightly to formins to accelerate actin filament elongation. Furthermore, we observed mDia1 dimers and CLIP-170 dimers co-tracking growing filament ends for minutes. CLIP-170-mDia1 complexes promoted actin polymerization approximately 18 times faster than free barbed end growth, while simultaneously enhancing protection from capping protein. We used a microtubule-actin dynamics co-reconstitution system to observe CLIP-170-mDia1 complexes being recruited to growing microtubule ends by EB1. The complexes triggered rapid growth of actin filaments that remained attached to the microtubule surface. These activities of CLIP-170 were required in primary neurons for normal dendritic morphology. Thus, our results reveal a cellular mechanism whereby growing microtubule plus-ends direct rapid actin assembly. PMID:27199431

  4. Actin kinetics shapes cortical network structure and mechanics

    PubMed Central

    Fritzsche, Marco; Erlenkämper, Christoph; Moeendarbary, Emad; Charras, Guillaume; Kruse, Karsten

    2016-01-01

    The actin cortex of animal cells is the main determinant of cellular mechanics. The continuous turnover of cortical actin filaments enables cells to quickly respond to stimuli. Recent work has shown that most of the cortical actin is generated by only two actin nucleators, the Arp2/3 complex and the formin Diaph1. However, our understanding of their interplay, their kinetics, and the length distribution of the filaments that they nucleate within living cells is poor. Such knowledge is necessary for a thorough comprehension of cellular processes and cell mechanics from basic polymer physics principles. We determined cortical assembly rates in living cells by using single-molecule fluorescence imaging in combination with stochastic simulations. We find that formin-nucleated filaments are, on average, 10 times longer than Arp2/3-nucleated filaments. Although formin-generated filaments represent less than 10% of all actin filaments, mechanical measurements indicate that they are important determinants of cortical elasticity. Tuning the activity of actin nucleators to alter filament length distribution may thus be a mechanism allowing cells to adjust their macroscopic mechanical properties to their physiological needs. PMID:27152338

  5. Internal coaxial cable seal system

    DOEpatents

    Hall, David R.; Sneddon, Cameron; Dahlgren, Scott Steven; Briscoe, Michael A.

    2006-07-25

    The invention is a seal system for a coaxial cable and is placed within the coaxial cable and its constituent components. A series of seal stacks including load ring components and elastomeric rings are placed on load bearing members within the coaxial cable sealing the annular space between the coaxial cable and an electrical contact passing there through. The coaxial cable is disposed within drilling components to transmit electrical signals between drilling components within a drill string. The seal system can be used in a variety of downhole components, such as sections of pipe in a drill string, drill collars, heavy weight drill pipe, and jars.

  6. Disposable telemetry cable deployment system

    DOEpatents

    Holcomb, David Joseph

    2000-01-01

    A disposable telemetry cable deployment system for facilitating information retrieval while drilling a well includes a cable spool adapted for insertion into a drill string and an unarmored fiber optic cable spooled onto the spool cable and having a downhole end and a stinger end. Connected to the cable spool is a rigid stinger which extends through a kelly of the drilling apparatus. A data transmission device for transmitting data to a data acquisition system is disposed either within or on the upper end of the rigid stinger.

  7. Flat conductor cable commercialization project

    NASA Technical Reports Server (NTRS)

    Hogarth, P.; Wadsworth, E.

    1977-01-01

    An undercarpet flat conductor cable and a baseboard flat conductor cable system were studied for commercialization. The undercarpet system is designed for use in office and commercial buildings. It employs a flat power cable, protected by a grounded metal shield, that terminates in receptacles mounted on the floor. It is designed to interface with a flat conductor cable telephone system. The baseboard system consists of a flat power cable mounted in a plastic raceway; both the raceway and the receptacles are mounted on the surface of the baseboard. It is designed primarily for use in residential buildings, particularly for renovation and concrete and masonry construction.

  8. Tapping the television cable.

    PubMed

    Clarke, M; Findlay, A; Canac, J F; Vergez, A

    1996-01-01

    Immediate access to patient data is essential to support good clinical decision making and support. However, away from the surgery, the doctor is currently unable to have any access to the clinical database. Solutions exist to support remote access, such as modems or radio data networks, but these are slow, with typical speeds in the 2-10 kbaud region. We propose a novel solution, to use the TV cable already installed in many homes. Using this technology, a suitably equipped computer (RF modern) is capable of connecting at speeds in excess of 500 kbaud and will run applications in exactly the same way as if connected to a surgery network: the cable TV becomes a LAN, but on a metropolitan scale. Brunel University, in collaboration with the Cable Corporation, has been piloting such a network. Issues include not only levels of service, but also security on the network and access, since the data are being effectively received in every home. However, close scrutiny of channel use can create closed networks reserved for specific users. The technology involves use of an RF modem to transmit data on a reverse channel (based at 16 MHz) on each subnet to a router at the head end of the cable network. This frequency translates the packet and retransmits it to all the subnets on a forward channel (based at 178 MHz). Each channel occupies the bandwidth normally allocated to one TV channel. Access is based on a modified CSMA/CD protocol, so treating the cable network as single multiple access network. The modem comes as a standard card installed in a PC and appears much as an ethernet card, but at reduced speed. With an NDIS driver it is quite able to support almost any network software, and has successfully demonstrated Novell and TCP/IP. We describe the HomeWorker network and the results from a pilot study being undertaken to determine the performance of the system and its impact on working practice.

  9. Reorganization of actin filaments by ADF/cofilin is involved in formation of microtubule structures during Xenopus oocyte maturation

    PubMed Central

    Yamagishi, Yuka; Abe, Hiroshi

    2015-01-01

    We examined the reorganization of actin filaments and microtubules during Xenopus oocyte maturation. Surrounding the germinal vesicle (GV) in immature oocytes, the cytoplasmic actin filaments reorganized to accumulate beneath the vegetal side of the GV, where the microtubule-organizing center and transient microtubule array (MTOC-TMA) assembled, just before GV breakdown (GVBD). Immediately after GVBD, both Xenopus ADF/cofilin (XAC) and its phosphatase Slingshot (XSSH) accumulated into the nuclei and intranuclear actin filaments disassembled from the vegetal side with the shrinkage of the GV. As the MTOC-TMA developed well, cytoplasmic actin filaments were retained at the MTOC-TMA base region. Suppression of XAC dephosphorylation by anti-XSSH antibody injection inhibited both actin filament reorganization and proper formation and localization of both the MTOC-TMA and meiotic spindles. Stabilization of actin filaments by phalloidin also inhibited formation of the MTOC-TMA and disassembly of intranuclear actin filaments without affecting nuclear shrinkage. Nocodazole also caused the MTOC-TMA and the cytoplasmic actin filaments at its base region to disappear, which further impeded disassembly of intranuclear actin filaments from the vegetal side. XAC appears to reorganize cytoplasmic actin filaments required for precise assembly of the MTOC and, together with the MTOC-TMA, regulate the intranuclear actin filament disassembly essential for meiotic spindle formation. PMID:26424802

  10. Proposed technique for vertical alignment of a crane's cable

    NASA Technical Reports Server (NTRS)

    Gera, J., Jr.

    1969-01-01

    Proposed vertical alignment technique senses the attitude of a cranes cable and displays any deviation from the vertical. The system consists of a detector assembly fixed to the boom and a display scope located in the cabin. It has potential application with either fixed-boom cranes or gantries.

  11. NMR solution structures of actin depolymerizing factor homology domains

    PubMed Central

    Goroncy, Alexander K; Koshiba, Seizo; Tochio, Naoya; Tomizawa, Tadashi; Sato, Manami; Inoue, Makato; Watanabe, Satoru; Hayashizaki, Yoshihide; Tanaka, Akiko; Kigawa, Takanori; Yokoyama, Shigeyuki

    2009-01-01

    Actin is one of the most conserved proteins in nature. Its assembly and disassembly are regulated by many proteins, including the family of actin-depolymerizing factor homology (ADF-H) domains. ADF-H domains can be divided into five classes: ADF/cofilin, glia maturation factor (GMF), coactosin, twinfilin, and Abp1/drebrin. The best-characterized class is ADF/cofilin. The other four classes have drawn much less attention and very few structures have been reported. This study presents the solution NMR structure of the ADF-H domain of human HIP-55-drebrin-like protein, the first published structure of a drebrin-like domain (mammalian), and the first published structure of GMF β (mouse). We also determined the structures of mouse GMF γ, the mouse coactosin-like domain and the C-terminal ADF-H domain of mouse twinfilin 1. Although the overall fold of the five domains is similar, some significant differences provide valuable insights into filamentous actin (F-actin) and globular actin (G-actin) binding, including the identification of binding residues on the long central helix. This long helix is stabilized by three or four residues. Notably, the F-actin binding sites of mouse GMF β and GMF γ contain two additional β-strands not seen in other ADF-H structures. The G-actin binding site of the ADF-H domain of human HIP-55-drebrin-like protein is absent and distorted in mouse GMF β and GMF γ. PMID:19768801

  12. Periodic actin structures in neuronal axons are required to maintain microtubules

    PubMed Central

    Qu, Yue; Hahn, Ines; Webb, Stephen E.D.; Pearce, Simon P.; Prokop, Andreas

    2017-01-01

    Axons are cable-like neuronal processes wiring the nervous system. They contain parallel bundles of microtubules as structural backbones, surrounded by regularly spaced actin rings termed the periodic membrane skeleton (PMS). Despite being an evolutionarily conserved, ubiquitous, highly ordered feature of axons, the function of PMS is unknown. Here we studied PMS abundance, organization, and function, combining versatile Drosophila genetics with superresolution microscopy and various functional readouts. Analyses with 11 actin regulators and three actin-targeting drugs suggest that PMS contains short actin filaments that are depolymerization resistant and sensitive to spectrin, adducin, and nucleator deficiency, consistent with microscopy-derived models proposing PMS as specialized cortical actin. Upon actin removal, we observed gaps in microtubule bundles, reduced microtubule polymerization, and reduced axon numbers, suggesting a role of PMS in microtubule organization. These effects become strongly enhanced when carried out in neurons lacking the microtubule-stabilizing protein Short stop (Shot). Combining the aforementioned actin manipulations with Shot deficiency revealed a close correlation between PMS abundance and microtubule regulation, consistent with a model in which PMS-dependent microtubule polymerization contributes to their maintenance in axons. We discuss potential implications of this novel PMS function along axon shafts for axon maintenance and regeneration. PMID:27881663

  13. Workers in the VAB remove cable covers from STS-98 SRB's for inspection

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- In the Vehicle Assembly Building, Richard Bruns, a United Space Alliance SRB technician, pulls cables out of the solid rocket booster system tunnel. The SRB is part of Space Shuttle Atlantis, rolled back from Launch Pad 39A in order to conduct tests on the cables. A prior extensive evaluation of NASA'''s SRB cable inventory on the shelf revealed conductor damage in four (of about 200) cables. Shuttle managers decided to prove the integrity of the system tunnel cables already on Atlantis before launching. Workers are conducting inspections, making continuity checks and conducting X-ray analysis on the cables. The launch has been rescheduled no earlier than Feb. 6.

  14. Workers in the VAB remove cable covers from STS-98 SRB's for inspection

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- Near the bottom of the solid rocket booster, a United Space Alliance SRB technician in the Vehicle Assembly Building detaches the SRB system tunnel cover of the 36 cables inside. Above and to the left is the bottom of the external tank. The SRB is part of Space Shuttle Atlantis, rolled back from Launch Pad 39A in order to conduct tests on the cables. A prior extensive evaluation of NASA'''s SRB cable inventory on the shelf revealed conductor damage in four (of about 200) cables. Shuttle managers decided to prove the integrity of the system tunnel cables already on Atlantis before launching. Workers are conducting inspections, making continuity checks and conducting X-ray analysis on the cables. The launch has been rescheduled no earlier than Feb. 6.

  15. Workers in the VAB remove cable covers from STS-98 SRB's for inspection

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- In the Vehicle Assembly Building, near the top of the solid rocket booster, Henry Jones and Richard Bruns begin to detach the SRB system tunnel cover on the 36 cables inside. Jones and Bruns are United Space Alliance SRB technicians. The SRB is part of Space Shuttle Atlantis, rolled back from Launch Pad 39A in order to conduct tests on the cables. A prior extensive evaluation of NASA'''s SRB cable inventory on the shelf revealed conductor damage in four (of about 200) cables. Shuttle managers decided to prove the integrity of the system tunnel cables already on Atlantis before launching. Workers are conducting inspections, making continuity checks and conducting X-ray analysis on the cables. The launch has been rescheduled no earlier than Feb. 6.

  16. Workers in the VAB remove cable covers from STS-98 SRB's for inspection

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- In the Vehicle Assembly Building, Richard Bruns, a United Space Alliance SRB technician, begins to detach the SRB system tunnel cover on the 36 cables inside. The SRB is part of Space Shuttle Atlantis, rolled back from Launch Pad 39A in order to conduct tests on the cables. A prior extensive evaluation of NASA'''s SRB cable inventory on the shelf revealed conductor damage in four (of about 200) cables. Shuttle managers decided to prove the integrity of the system tunnel cables already on Atlantis before launching. Workers are conducting inspections, making continuity checks and conducting X-ray analysis on the cables. The launch has been rescheduled no earlier than Feb. 6.

  17. Workers in the VAB remove cable covers from STS-98 SRB's for inspection

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- Near the bottom of the solid rocket booster, a worker in the Vehicle Assembly Building begins to detach the SRB system tunnel cover on the 36 cables inside. The SRB is part of Space Shuttle Atlantis, rolled back from Launch Pad 39A in order to conduct tests on the cables. A prior extensive evaluation of NASA'''s SRB cable inventory on the shelf revealed conductor damage in four (of about 200) cables. Shuttle managers decided to prove the integrity of the system tunnel cables already on Atlantis before launching. Workers are conducting inspections, making continuity checks and conducting X-ray analysis on the cables. The launch has been rescheduled no earlier than Feb. 6.

  18. Workers in the VAB remove cable covers from STS-98 SRB's for inspection

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- In the Vehicle Assembly Building, Richard Bruns and Henry Jones, United Space Alliance SRB technicians, begin to detach the SRB system tunnel cover on the 36 cables inside. The SRB is part of Space Shuttle Atlantis, rolled back from Launch Pad 39A in order to conduct tests on the cables. A prior extensive evaluation of NASA'''s SRB cable inventory on the shelf revealed conductor damage in four (of about 200) cables. Shuttle managers decided to prove the integrity of the system tunnel cables already on Atlantis before launching. Workers are conducting inspections, making continuity checks and conducting X-ray analysis on the cables. The launch has been rescheduled no earlier than Feb. 6.

  19. Workers in the VAB remove cable covers from STS-98 SRB's for inspection

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- Near the bottom of the solid rocket booster in the Vehicle Assembly Building, a United Space Alliance SRB technician detaches the SRB system tunnel cover on the 36 cables inside. The SRB is part of Space Shuttle Atlantis, rolled back from Launch Pad 39A in order to conduct tests on the cables. A prior extensive evaluation of NASA'''s SRB cable inventory on the shelf revealed conductor damage in four (of about 200) cables. Shuttle managers decided to prove the integrity of the system tunnel cables already on Atlantis before launching. Workers are conducting inspections, making continuity checks and conducting X-ray analysis on the cables. The launch has been rescheduled no earlier than Feb. 6.

  20. Actin and Endocytosis in Budding Yeast

    PubMed Central

    Goode, Bruce L.; Eskin, Julian A.; Wendland, Beverly

    2015-01-01

    Endocytosis, the process whereby the plasma membrane invaginates to form vesicles, is essential for bringing many substances into the cell and for membrane turnover. The mechanism driving clathrin-mediated endocytosis (CME) involves > 50 different protein components assembling at a single location on the plasma membrane in a temporally ordered and hierarchal pathway. These proteins perform precisely choreographed steps that promote receptor recognition and clustering, membrane remodeling, and force-generating actin-filament assembly and turnover to drive membrane invagination and vesicle scission. Many critical aspects of the CME mechanism are conserved from yeast to mammals and were first elucidated in yeast, demonstrating that it is a powerful system for studying endocytosis. In this review, we describe our current mechanistic understanding of each step in the process of yeast CME, and the essential roles played by actin polymerization at these sites, while providing a historical perspective of how the landscape has changed since the preceding version of the YeastBook was published 17 years ago (1997). Finally, we discuss the key unresolved issues and where future studies might be headed. PMID:25657349

  1. Investigation of Shielded and Unshielded Cables.

    DTIC Science & Technology

    1980-11-11

    increase the yield strength of cables. Table 2 lists the required and measured strengths of the test cables. Both shielded and unshielded Size 2 cables do...selected for evaluation, five shielded and five unshielded, and were examined, dissected and the internal components measured . A list of the cables and...components were measured following the testing parameters shown in Table 17. All complete cables, cables less jacket and cables less jacket and shield

  2. Development of Inspection Robots for Bridge Cables

    PubMed Central

    Kim, Se-Hoon; Lee, Jong-Jae

    2013-01-01

    This paper presents the bridge cable inspection robot developed in Korea. Two types of the cable inspection robots were developed for cable-suspension bridges and cable-stayed bridge. The design of the robot system and performance of the NDT techniques associated with the cable inspection robot are discussed. A review on recent advances in emerging robot-based inspection technologies for bridge cables and current bridge cable inspection methods is also presented. PMID:24459453

  3. Ring closure in actin polymers

    NASA Astrophysics Data System (ADS)

    Sinha, Supurna; Chattopadhyay, Sebanti

    2017-03-01

    We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers.

  4. The role of actin networks in cellular mechanosensing

    NASA Astrophysics Data System (ADS)

    Azatov, Mikheil

    Physical processes play an important role in many biological phenomena, such as wound healing, organ development, and tumor metastasis. During these processes, cells constantly interact with and adapt to their environment by exerting forces to mechanically probe the features of their surroundings and generating appropriate biochemical responses. The mechanisms underlying how cells sense the physical properties of their environment are not well understood. In this thesis, I present my studies to investigate cellular responses to the stiffness and topography of the environment. In order to sense the physical properties of their environment, cells dynamically reorganize the structure of their actin cytoskeleton, a dynamic network of biopolymers, altering the shape and spatial distribution of protein assemblies. Several observations suggest that proteins that crosslink actin filaments may play an important role in cellular mechanosensitivity. Palladin is an actin-crosslinking protein that is found in the lamellar actin network, stress fibers and focal adhesions, cellular structures that are critical for mechanosensing of the physical environment. By virtue of its close interactions with these structures in the cell, palladin may play an important role in cell mechanics. However, the role of actin crosslinkers in general, and palladin in particular, in cellular force generation and mechanosensing is not well known. I have investigated the role of palladin in regulating the plasticity of the actin cytoskeleton and cellular force generation in response to alterations in substrate stiffness. I have shown that the expression levels of palladin modulate the forces exerted by cells and their ability to sense substrate stiffness. Perturbation experiments also suggest that palladin levels in cells altered myosin motor activity. These results suggest that the actin crosslinkers, such as palladin, and myosin motors coordinate for optimal cell function and to prevent aberrant

  5. Identification of Arabidopsis cyclase-associated protein 1 as the first nucleotide exchange factor for plant actin.

    PubMed

    Chaudhry, Faisal; Guérin, Christophe; von Witsch, Matthias; Blanchoin, Laurent; Staiger, Christopher J

    2007-08-01

    The actin cytoskeleton powers organelle movements, orchestrates responses to abiotic stresses, and generates an amazing array of cell shapes. Underpinning these diverse functions of the actin cytoskeleton are several dozen accessory proteins that coordinate actin filament dynamics and construct higher-order assemblies. Many actin-binding proteins from the plant kingdom have been characterized and their function is often surprisingly distinct from mammalian and fungal counterparts. The adenylyl cyclase-associated protein (CAP) has recently been shown to be an important regulator of actin dynamics in vivo and in vitro. The disruption of actin organization in cap mutant plants indicates defects in actin dynamics or the regulated assembly and disassembly of actin subunits into filaments. Current models for actin dynamics maintain that actin-depolymerizing factor (ADF)/cofilin removes ADP-actin subunits from filament ends and that profilin recharges these monomers with ATP by enhancing nucleotide exchange and delivery of subunits onto filament barbed ends. Plant profilins, however, lack the essential ability to stimulate nucleotide exchange on actin, suggesting that there might be a missing link yet to be discovered from plants. Here, we show that Arabidopsis thaliana CAP1 (AtCAP1) is an abundant cytoplasmic protein; it is present at a 1:3 M ratio with total actin in suspension cells. AtCAP1 has equivalent affinities for ADP- and ATP-monomeric actin (Kd approximately 1.3 microM). Binding of AtCAP1 to ATP-actin monomers inhibits polymerization, consistent with AtCAP1 being an actin sequestering protein. However, we demonstrate that AtCAP1 is the first plant protein to increase the rate of nucleotide exchange on actin. Even in the presence of ADF/cofilin, AtCAP1 can recharge actin monomers and presumably provide a polymerizable pool of subunits to profilin for addition onto filament ends. In turnover assays, plant profilin, ADF, and CAP act cooperatively to promote flux

  6. Mechanical reinforcement for RACC cables in high magnetic background fields

    NASA Astrophysics Data System (ADS)

    Bayer, C. M.; Gade, P. V.; Barth, C.; Preuß, A.; Jung, A.; Weiß, K. P.

    2016-02-01

    Operable in liquid helium, liquid hydrogen or liquid nitrogen, high temperature superconductor (HTS) cables are investigated as future alternatives to low temperature superconductor (LTS) cables in magnet applications. Different high current HTS cable concepts have been developed and optimized in the last years—each coming with its own benefits and challenges. As the Roebel assembled coated conductor (RACC) is the only fully transposed HTS cable investigated so far, it is attractive for large scale magnet and accelerator magnet applications when field quality and alternating current (AC) losses are of highest importance. However, due to its filamentary character, the RACC is very sensitive to Lorentz forces. In order to increase the mechanical strength of the RACC, each of the HTS strands was covered by an additional copper tape. After investigating the maximum applicable transverse pressure on the strand composition, the cable was clamped into a stainless steel structure to reinforce it against Lorentz forces. A comprehensive test has been carried out in the FBI facility at 4.2 K in a magnetic field of up to 12 T. This publication discusses the maximum applicable pressure as well as the behaviour of the RACC cable as a function of an external magnetic field.

  7. Long Cable Deployments During Martian Touchdown: Lessons Learned

    NASA Technical Reports Server (NTRS)

    Shafer, Michael W.; Sell, Steven W.

    2009-01-01

    The launch of NASA/JPL's next generation Mars rover is planned for the fall of 2011. The landing scheme chosen for this rover represents a step forward in unmanned payload delivery. The rover will be lowered from a rocket powered descent stage and then placed onto the surface while hanging from three bridles. During this touchdown event, the communication between the rover and descent stage is maintained by an electrical umbilical cable which is deployed in parallel with the structural bridles. During the development of the deployment device for the electrical umbilical, many obstacles were identified and overcome. Many of these challenges were due in large part to the helical nature of the packing geometry of the umbilical cable. And although none of these issues resulted in the failure of the design, they increased both development and assembly time. Many of the issues and some of the benefits of a helical deployment were not immediately apparent during the trade studies carried out during the deployment selection process. Tests were conducted upon completion of the device in order to characterize both the deployment and separation characteristics of the cable. Extraction loads were needed for inputs to touchdown models and separation dynamics were required to assess cable-rover recontact risk. Understanding the pros and cons surrounding the deployment of a helically packed cable would most certainly influence the outcome of future trade studies surrounding the selection of cable deployment options.

  8. Pipe-type cable floated into place across river

    SciTech Connect

    Not Available

    1994-07-01

    In 1992, the 60-yr-old Portland Bridge across the Fore River in Maine had to be replaced with a completely new structure. Unfortunately for Central Maine Power Co, three 34.5-kV submarine cables and a 115-kV pipe-type cable (plus spare pipe), which paralleled the old structure, were directly in the path planned for the footing of the new bridge. Before construction could begin, these had to be relocated to the other side of the old bridge. Because of space limitations in the crossing area, the two 1200-ft replacement pipes were assembled one mile upstream and floated down to the bridge using specially made polystyrene floats. The trench, measuring 20 ft wide and 20 ft deep, was dredged across the river bottom and designed to accommodate both the submarine and pipe-type cables with adequate spacing. First, the two pipes were floated into position and sunk into the trench. Then the three submarine cables were laid simultaneously from a cable barge. Divers ensured that there was adequate spacing between the medium- and high-voltage cables. 10 figs.

  9. Method to improve superconductor cable

    DOEpatents

    Borden, A.R.

    1984-03-08

    A method is disclosed of making a stranded superconductor cable having improved flexing and bending characteristics. In such method, a plurality of superconductor strands are helically wound around a cylindrical portion of a mandrel which tapers along a transitional portion to a flat end portion. The helically wound strands form a multistrand hollow cable which is partially flattened by pressure rollers as the cable travels along the transitional portion. The partially flattened cable is impacted with repeated hammer blows as the hollow cable travels along the flat end portion. The hammer blows flatten both the internal and the external surfaces of the strands. The cable is fully flattened and compacted by two sets of pressure rollers which engage the flat sides and the edges of the cable after it has traveled away from the flat end portion of the mandrel. The flattened internal surfaces slide easily over one another when the cable is flexed or bent so that there is very little possibility that the cable will be damaged by the necessary flexing and bending required to wind the cable into magnet coils.

  10. Cable shield connecting device

    DOEpatents

    Silva, Frank A.

    1979-01-01

    A cable shield connecting device for installation on a high voltage cable of the type having a metallic shield, the device including a relatively conformable, looped metal bar for placement around a bared portion of the metallic shield to extend circumferentially around a major portion of the circumference of the metallic shield while being spaced radially therefrom, a plurality of relatively flexible metallic fingers affixed to the bar, projecting from the bar in an axial direction and spaced circumferentially along the bar, each finger being attached to the metallic shield at a portion located remote from the bar to make electrical contact with the metallic shield, and a connecting conductor integral with the bar.

  11. Cellular Levels of Signaling Factors Are Sensed by β-actin Alleles to Modulate Transcriptional Pulse Intensity.

    PubMed

    Kalo, Alon; Kanter, Itamar; Shraga, Amit; Sheinberger, Jonathan; Tzemach, Hadar; Kinor, Noa; Singer, Robert H; Lionnet, Timothée; Shav-Tal, Yaron

    2015-04-21

    The transcriptional response of β-actin to extra-cellular stimuli is a paradigm for transcription factor complex assembly and regulation. Serum induction leads to a precisely timed pulse of β-actin transcription in the cell population. Actin protein is proposed to be involved in this response, but it is not known whether cellular actin levels affect nuclear β-actin transcription. We perturbed the levels of key signaling factors and examined the effect on the induced transcriptional pulse by following endogenous β-actin alleles in single living cells. Lowering serum response factor (SRF) protein levels leads to loss of pulse integrity, whereas reducing actin protein levels reveals positive feedback regulation, resulting in elevated gene activation and a prolonged transcriptional response. Thus, transcriptional pulse fidelity requires regulated amounts of signaling proteins, and perturbations in factor levels eliminate the physiological response, resulting in either tuning down or exaggeration of the transcriptional pulse.

  12. High conductance surge cable

    DOEpatents

    Murray, M.M.; Wilfong, D.H.; Lomax, R.E.

    1998-12-08

    An electrical cable for connecting transient voltage surge suppressors to electrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation. 6 figs.

  13. High conductance surge cable

    DOEpatents

    Murray, Matthew M.; Wilfong, Dennis H.; Lomax, Ralph E.

    1998-01-01

    An electrical cable for connecting transient voltage surge suppressers to ectrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation.

  14. Non-Intrusive Cable Tester

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J. (Inventor); Simpson, Howard J. (Inventor)

    1999-01-01

    A cable tester is described for low frequency testing of a cable for faults. The tester allows for testing a cable beyond a point where a signal conditioner is installed, minimizing the number of connections which have to be disconnected. A magnetic pickup coil is described for detecting a test signal injected into the cable. A narrow bandpass filter is described for increasing detection of the test signal. The bandpass filter reduces noise so that a high gain amplifier provided for detecting a test signal is not completely saturate by noise. To further increase the accuracy of the cable tester, processing gain is achieved by comparing the signal from the amplifier with at least one reference signal emulating the low frequency input signal injected into the cable. Different processing techniques are described evaluating a detected signal.

  15. Novel actin depolymerizing macrolide aplyronine A.

    PubMed

    Saito, S; Watabe, S; Ozaki, H; Kigoshi, H; Yamada, K; Fusetani, N; Karaki, H

    1996-09-01

    Aplyronine A is a macrolide isolated from Aplysia kurodai. By monitoring fluorescent intensity of pyrenyl-actin, it was found that aplyronine A inhibited both the velocity and the degree of actin polymerization. Aplyronine A also quickly depolymerized F-actin. The kinetics of depolymerization suggest that aplyronine A severs F-actin. The relationship between the concentration of total actin and F-actin at different concentrations of aplyronine A suggests that aplyronine A forms a 1:1 complex with G-actin. From these results, it is concluded that aplyronine A inhibits actin polymerization and depolymerizes F-actin by nibbling. Comparison of the chemical structure of aplyronine A and another actin-depolymerizing macrolide, mycalolide B, suggests that the side-chain but not the macrolide ring of aplyronine A may account for its actin binding and severing activity.

  16. Bacterial Actins and Their Interactors.

    PubMed

    Gayathri, Pananghat

    2017-01-01

    Bacterial actins polymerize in the presence of nucleotide (preferably ATP), form a common arrangement of monomeric interfaces within a protofilament, and undergo ATP hydrolysis-dependent change in stability of the filament-all of which contribute to performing their respective functions. The relative stability of the filament in the ADP-bound form compared to that of ATP and the rate of addition of monomers at the two ends decide the filament dynamics. One of the major differences between eukaryotic actin and bacterial actins is the variety in protofilament arrangements and dynamics exhibited by the latter. The filament structure and the polymerization dynamics enable them to perform various functions such as shape determination in rod-shaped bacteria (MreB), cell division (FtsA), plasmid segregation (ParM family of actin-like proteins), and organelle positioning (MamK). Though the architecture and dynamics of a few representative filaments have been studied, information on the effect of interacting partners on bacterial actin filament dynamics is not very well known. The chapter reviews some of the structural and functional aspects of bacterial actins, with special focus on the effect that interacting partners exert on the dynamics of bacterial actins, and how these assist them to carry out the functions within the bacterial cell.

  17. Cable structures and lunar environment

    NASA Astrophysics Data System (ADS)

    Ettouney, Mohammed; Benaroya, Haym; Agassi, Nissim

    1992-07-01

    The feasibility of using cable-based structural systems for lunar bases is examined. Small, medium, and long structural spans are considered, and it is shown that each span category dictates the use of a different structural system. It is demonstrated that efficient cable and secondary support systems and foundations are feasible for each span group. The advantages and possibilities offered by cable structures for lunar bases are discussed.

  18. Rotating Connection for Electrical Cables

    NASA Technical Reports Server (NTRS)

    Manges, D. R.

    1986-01-01

    Cable reel provides electrical connections between fixed structure and rotating one. Reel carries power and signal lines while allowing rotating structure to turn up to 360 degrees with respect to fixed structure. Reel replaces sliprings. Can be used to electrically connect arm of robot with body. Reel releases cable to rotating part as it turns and takes up cable as rotating part comes back to its starting position, without tangling, twisting, or kinking.

  19. Monitoring cables for local degradation

    SciTech Connect

    Bustard, L.D.; Sliter, G.E.

    1989-01-01

    Recent experiences in operating nuclear plants in the United States have demonstrated the need for an in situ cable condition monitoring technique that can assess whether installed, low-voltage, unshielded cables have local damage that could compromise their ability to function under normal and accident service conditions. This paper summarizes current US programs that have been initiated to develop a technological basis for monitoring cables with local degradation. 7 refs.

  20. Actin cytoskeleton: putting a CAP on actin polymerization.

    PubMed

    Stevenson, V A; Theurkauf, W E

    2000-10-05

    Two recent studies have identified a Drosophila homolog of cyclase-associated protein (CAP) as a developmentally important negative regulator of actin polymerization that may also directly mediate signal transduction.

  1. A high-affinity interaction with ADP-actin monomers underlies the mechanism and in vivo function of Srv2/cyclase-associated protein.

    PubMed

    Mattila, Pieta K; Quintero-Monzon, Omar; Kugler, Jamie; Moseley, James B; Almo, Steven C; Lappalainen, Pekka; Goode, Bruce L

    2004-11-01

    Cyclase-associated protein (CAP), also called Srv2 in Saccharomyces cerevisiae, is a conserved actin monomer-binding protein that promotes cofilin-dependent actin turnover in vitro and in vivo. However, little is known about the mechanism underlying this function. Here, we show that S. cerevisiae CAP binds with strong preference to ADP-G-actin (Kd 0.02 microM) compared with ATP-G-actin (Kd 1.9 microM) and competes directly with cofilin for binding ADP-G-actin. Further, CAP blocks actin monomer addition specifically to barbed ends of filaments, in contrast to profilin, which blocks monomer addition to pointed ends of filaments. The actin-binding domain of CAP is more extensive than previously suggested and includes a recently solved beta-sheet structure in the C-terminus of CAP and adjacent sequences. Using site-directed mutagenesis, we define evolutionarily conserved residues that mediate binding to ADP-G-actin and demonstrate that these activities are required for CAP function in vivo in directing actin organization and polarized cell growth. Together, our data suggest that in vivo CAP competes with cofilin for binding ADP-actin monomers, allows rapid nucleotide exchange to occur on actin, and then because of its 100-fold weaker binding affinity for ATP-actin compared with ADP-actin, allows other cellular factors such as profilin to take the handoff of ATP-actin and facilitate barbed end assembly.

  2. Superconducting flat tape cable magnet

    DOEpatents

    Takayasu, Makoto

    2015-08-11

    A method for winding a coil magnet with the stacked tape cables, and a coil so wound. The winding process is controlled and various shape coils can be wound by twisting about the longitudinal axis of the cable and bending following the easy bend direction during winding, so that sharp local bending can be obtained by adjusting the twist pitch. Stack-tape cable is twisted while being wound, instead of being twisted in a straight configuration and then wound. In certain embodiments, the straight length should be half of the cable twist-pitch or a multiple of it.

  3. Actin dynamics and cofilin-actin rods in Alzheimer disease

    PubMed Central

    Bamburg, James R.; Bernstein, Barbara W.

    2017-01-01

    Cytoskeletal abnormalities and synaptic loss, typical of both familial and sporadic Alzheimer disease (AD), are induced by diverse stresses such as neuroinflammation, oxidative stress, and energetic stress, each of which may be initiated or enhanced by proinflammatory cytokines or amyloid-β (Aβ) peptides. Extracellular Aβ-containing plaques and intracellular phospho-tau-containing neurofibrillary tangles are postmortem pathologies required to confirm AD and have been the focus of most studies. However, AD brain, but not normal brain, also have increased levels of cytoplasmic rod-shaped bundles of filaments composed of ADF/cofilin-actin in a 1:1 complex (rods). Cofilin, the major ADF/cofilin isoform in mammalian neurons, severs actin filaments at low cofilin/actin ratios and stabilizes filaments at high cofilin/actin ratios. It binds cooperatively to ADP-actin subunits in F-actin. Cofilin is activated by dephosphorylation and may be oxidized in stressed neurons to form disulfide-linked dimers, required for bundling cofilin-actin filaments into stable rods. Rods form within neurites causing synaptic dysfunction by sequestering cofilin, disrupting normal actin dynamics, blocking transport, and exacerbating mitochondrial membrane potential loss. Aβ and proinflammatory cytokines induce rods through a cellular prion protein-dependent activation of NADPH oxidase and production of reactive oxygen species. Here we review recent advances in our understanding of cofilin biochemistry, rod formation, and the development of cognitive deficits. We will then discuss rod formation as a molecular pathway for synapse loss that may be common between all three prominent current AD hypotheses, thus making rods an attractive therapeutic target. PMID:26873625

  4. Cofilin cooperates with fascin to disassemble filopodial actin filaments

    PubMed Central

    Breitsprecher, Dennis; Koestler, Stefan A.; Chizhov, Igor; Nemethova, Maria; Mueller, Jan; Goode, Bruce L.; Small, J. Victor; Rottner, Klemens; Faix, Jan

    2011-01-01

    Cells use a large repertoire of proteins to remodel the actin cytoskeleton. Depending on the proteins involved, F-actin is organized in specialized protrusions such as lamellipodia or filopodia, which serve diverse functions in cell migration and sensing. Although factors responsible for directed filament assembly in filopodia have been extensively characterized, the mechanisms of filament disassembly in these structures are mostly unknown. We investigated how the actin-depolymerizing factor cofilin-1 affects the dynamics of fascincrosslinked actin filaments in vitro and in live cells. By multicolor total internal reflection fluorescence microscopy and fluorimetric assays, we found that cofilin-mediated severing is enhanced in fascin-crosslinked bundles compared with isolated filaments, and that fascin and cofilin act synergistically in filament severing. Immunolabeling experiments demonstrated for the first time that besides its known localization in lamellipodia and membrane ruffles, endogenous cofilin can also accumulate in the tips and shafts of filopodia. Live-cell imaging of fluorescently tagged proteins revealed that cofilin is specifically targeted to filopodia upon stalling of protrusion and during their retraction. Subsequent electron tomography established filopodial actin filament and/or bundle fragmentation to precisely correlate with cofilin accumulation. These results identify a new mechanism of filopodium disassembly involving both fascin and cofilin. PMID:21940796

  5. Triggering signaling pathways using F-actin self-organization

    PubMed Central

    Colin, A.; Bonnemay, L.; Gayrard, C.; Gautier, J.; Gueroui, Z.

    2016-01-01

    The spatiotemporal organization of proteins within cells is essential for cell fate behavior. Although it is known that the cytoskeleton is vital for numerous cellular functions, it remains unclear how cytoskeletal activity can shape and control signaling pathways in space and time throughout the cell cytoplasm. Here we show that F-actin self-organization can trigger signaling pathways by engineering two novel properties of the microfilament self-organization: (1) the confinement of signaling proteins and (2) their scaffolding along actin polymers. Using in vitro reconstitutions of cellular functions, we found that both the confinement of nanoparticle-based signaling platforms powered by F-actin contractility and the scaffolding of engineered signaling proteins along actin microfilaments can drive a signaling switch. Using Ran-dependent microtubule nucleation, we found that F-actin dynamics promotes the robust assembly of microtubules. Our in vitro assay is a first step towards the development of novel bottom-up strategies to decipher the interplay between cytoskeleton spatial organization and signaling pathway activity. PMID:27698406

  6. Novel actin-like filament structure from Clostridium tetani.

    PubMed

    Popp, David; Narita, Akihiro; Lee, Lin Jie; Ghoshdastider, Umesh; Xue, Bo; Srinivasan, Ramanujam; Balasubramanian, Mohan K; Tanaka, Toshitsugu; Robinson, Robert C

    2012-06-15

    Eukaryotic F-actin is constructed from two protofilaments that gently wind around each other to form a helical polymer. Several bacterial actin-like proteins (Alps) are also known to form F-actin-like helical arrangements from two protofilaments, yet with varied helical geometries. Here, we report a unique filament architecture of Alp12 from Clostridium tetani that is constructed from four protofilaments. Through fitting of an Alp12 monomer homology model into the electron microscopy data, the filament was determined to be constructed from two antiparallel strands, each composed of two parallel protofilaments. These four protofilaments form an open helical cylinder separated by a wide cleft. The molecular interactions within single protofilaments are similar to F-actin, yet interactions between protofilaments differ from those in F-actin. The filament structure and assembly and disassembly kinetics suggest Alp12 to be a dynamically unstable force-generating motor involved in segregating the pE88 plasmid, which encodes the lethal tetanus toxin, and thus a potential target for drug design. Alp12 can be repeatedly cycled between states of polymerization and dissociation, making it a novel candidate for incorporation into fuel-propelled nanobiopolymer machines.

  7. Slow down of actin depolymerization by cross-linking molecules.

    PubMed

    Schmoller, Kurt M; Semmrich, Christine; Bausch, Andreas R

    2011-02-01

    The ability to control the assembly and disassembly dynamics of actin filaments is an essential property of the cellular cytoskeleton. While many different proteins are known which accelerate the polymerization of monomers into filaments or promote their disintegration, much less is known on mechanisms which guarantee the kinetic stability of the cytoskeletal filaments. Previous studies indicate that cross-linking molecules might fulfill these stabilizing tasks, which in addition facilitates their ability to regulate the organization of cytoskeletal structures in vivo. The effect of depolymerization factors on such structures or the mechanism which leads finally to their disintegration remain unknown. Here, we use multiple depolymerization methods in order to directly demonstrate that cross-linking and bundling proteins effectively suppress the actin depolymerization in a concentration dependent manner. Even the actin depolymerizing factor cofilin is not sufficient to facilitate a fast disintegration of highly cross-linked actin networks unless molecular motors are used simultaneously. The drastic modification of actin kinetics by cross-linking molecules can be expected to have wide-ranging implications for our understanding of the cytoskeleton, where cross-linking molecules are omnipresent and essential.

  8. Plasma Membrane Calcium ATPase Activity Is Regulated by Actin Oligomers through Direct Interaction*

    PubMed Central

    Dalghi, Marianela G.; Fernández, Marisa M.; Ferreira-Gomes, Mariela; Mangialavori, Irene C.; Malchiodi, Emilio L.; Strehler, Emanuel E.; Rossi, Juan Pablo F. C.

    2013-01-01

    As recently described by our group, plasma membrane calcium ATPase (PMCA) activity can be regulated by the actin cytoskeleton. In this study, we characterize the interaction of purified G-actin with isolated PMCA and examine the effect of G-actin during the first polymerization steps. As measured by surface plasmon resonance, G-actin directly interacts with PMCA with an apparent 1:1 stoichiometry in the presence of Ca2+ with an apparent affinity in the micromolar range. As assessed by the photoactivatable probe 1-O-hexadecanoyl-2-O-[9-[[[2-[125I]iodo-4-(trifluoromethyl-3H-diazirin-3-yl)benzyl]oxy]carbonyl]nonanoyl]-sn-glycero-3-phosphocholine, the association of PMCA to actin produced a shift in the distribution of the conformers of the pump toward a calmodulin-activated conformation. G-actin stimulates Ca2+-ATPase activity of the enzyme when incubated under polymerizing conditions, displaying a cooperative behavior. The increase in the Ca2+-ATPase activity was related to an increase in the apparent affinity for Ca2+ and an increase in the phosphoenzyme levels at steady state. Although surface plasmon resonance experiments revealed only one binding site for G-actin, results clearly indicate that more than one molecule of G-actin was needed for a regulatory effect on the pump. Polymerization studies showed that the experimental conditions are compatible with the presence of actin in the first stages of assembly. Altogether, these observations suggest that the stimulatory effect is exerted by short oligomers of actin. The functional interaction between actin oligomers and PMCA represents a novel regulatory pathway by which the cortical actin cytoskeleton participates in the regulation of cytosolic Ca2+ homeostasis. PMID:23803603

  9. Plasma membrane calcium ATPase activity is regulated by actin oligomers through direct interaction.

    PubMed

    Dalghi, Marianela G; Fernández, Marisa M; Ferreira-Gomes, Mariela; Mangialavori, Irene C; Malchiodi, Emilio L; Strehler, Emanuel E; Rossi, Juan Pablo F C

    2013-08-09

    As recently described by our group, plasma membrane calcium ATPase (PMCA) activity can be regulated by the actin cytoskeleton. In this study, we characterize the interaction of purified G-actin with isolated PMCA and examine the effect of G-actin during the first polymerization steps. As measured by surface plasmon resonance, G-actin directly interacts with PMCA with an apparent 1:1 stoichiometry in the presence of Ca(2+) with an apparent affinity in the micromolar range. As assessed by the photoactivatable probe 1-O-hexadecanoyl-2-O-[9-[[[2-[(125)I]iodo-4-(trifluoromethyl-3H-diazirin-3-yl)benzyl]oxy]carbonyl]nonanoyl]-sn-glycero-3-phosphocholine, the association of PMCA to actin produced a shift in the distribution of the conformers of the pump toward a calmodulin-activated conformation. G-actin stimulates Ca(2+)-ATPase activity of the enzyme when incubated under polymerizing conditions, displaying a cooperative behavior. The increase in the Ca(2+)-ATPase activity was related to an increase in the apparent affinity for Ca(2+) and an increase in the phosphoenzyme levels at steady state. Although surface plasmon resonance experiments revealed only one binding site for G-actin, results clearly indicate that more than one molecule of G-actin was needed for a regulatory effect on the pump. Polymerization studies showed that the experimental conditions are compatible with the presence of actin in the first stages of assembly. Altogether, these observations suggest that the stimulatory effect is exerted by short oligomers of actin. The functional interaction between actin oligomers and PMCA represents a novel regulatory pathway by which the cortical actin cytoskeleton participates in the regulation of cytosolic Ca(2+) homeostasis.

  10. Dual pools of actin at presynaptic terminals.

    PubMed

    Bleckert, Adam; Photowala, Huzefa; Alford, Simon

    2012-06-01

    We investigated actin's function in vesicle recycling and exocytosis at lamprey synapses and show that FM1-43 puncta and phalloidin-labeled filamentous actin (F-actin) structures are colocalized, yet recycling vesicles are not contained within F-actin clusters. Additionally, phalloidin also labels a plasma membrane-associated cortical actin. Injection of fluorescent G-actin revealed activity-independent dynamic actin incorporation into presynaptic synaptic vesicle clusters but not into cortical actin. Latrunculin-A, which sequesters G-actin, dispersed vesicle-associated actin structures and prevented subsequent labeled G-actin and phalloidin accumulation at presynaptic puncta, yet cortical phalloidin labeling persisted. Dispersal of presynaptic F-actin structures by latrunculin-A did not disrupt vesicle clustering or recycling or alter the amplitude or kinetics of excitatory postsynaptic currents (EPSCs). However, it slightly enhanced release during repetitive stimulation. While dispersal of presynaptic actin puncta with latrunculin-A failed to disperse synaptic vesicles or inhibit synaptic transmission, presynaptic phalloidin injection blocked exocytosis and reduced endocytosis measured by action potential-evoked FM1-43 staining. Furthermore, phalloidin stabilization of only cortical actin following pretreatment with latrunculin-A was sufficient to inhibit synaptic transmission. Conversely, treatment of axons with jasplakinolide, which induces F-actin accumulation but disrupts F-actin structures in vivo, resulted in increased synaptic transmission accompanied by a loss of phalloidin labeling of cortical actin but no loss of actin labeling within vesicle clusters. Marked synaptic deficits seen with phalloidin stabilization of cortical F-actin, in contrast to the minimal effects of disruption of a synaptic vesicle-associated F-actin, led us to conclude that two structurally and functionally distinct pools of actin exist at presynaptic sites.

  11. 5. VIEW OF CABLE SHED AND CABLE TRAY EMANATING FROM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. VIEW OF CABLE SHED AND CABLE TRAY EMANATING FROM SOUTH FACE OF LAUNCH OPERATIONS BUILDING. MICROWAVE DISH IN FOREGROUND. METEOROLOGICAL TOWER IN BACKGROUND. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Operations Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  12. 51. View of sitdown cable car and cable way for ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    51. View of sit-down cable car and cable way for stream gaging, looking west. Photo by Robin Lee Tedder, Puget Power, 1989. - Puget Sound Power & Light Company, White River Hydroelectric Project, 600 North River Avenue, Dieringer, Pierce County, WA

  13. 52. View of sitdown cable car, cable way, and stream ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. View of sit-down cable car, cable way, and stream gaging station, looking southeast. Photo by Robin Lee Tedder, Puget Power, 1989. - Puget Sound Power & Light Company, White River Hydroelectric Project, 600 North River Avenue, Dieringer, Pierce County, WA

  14. [Photodynamic therapy for actinic cheilitis].

    PubMed

    Castaño, E; Comunión, A; Arias, D; Miñano, R; Romero, A; Borbujo, J

    2009-12-01

    Actinic cheilitis is a subtype of actinic keratosis that mainly affects the lower lip and has a higher risk of malignant transformation. Its location on the labial mucosa influences the therapeutic approach. Vermilionectomy requires local or general anesthetic and is associated with a risk of an unsightly scar, and the treatment with 5-fluorouracil or imiquimod lasts for several weeks and the inflammatory reaction can be very intense. A number of authors have used photodynamic therapy as an alternative to the usual treatments. We present 3 patients with histologically confirmed actinic cheilitis treated using photodynamic therapy with methyl aminolevulinic acid as the photosensitizer and red light at 630 nm. The clinical response was good, with no recurrences after 3 to 6 months of follow-up. Our experience supports the use of photodynamic therapy as a good alternative for the treatment of actinic cheilitis.

  15. Arg/Abl2 modulates the affinity and stoichiometry of binding of cortactin to F-actin.

    PubMed

    MacGrath, Stacey M; Koleske, Anthony J

    2012-08-21

    The Abl family nonreceptor tyrosine kinase Arg/Abl2 interacts with cortactin, an Arp2/3 complex activator, to promote actin-driven cell edge protrusion. Both Arg and cortactin bind directly to filamentous actin (F-actin). While protein-protein interactions between Arg and cortactin have well-characterized downstream effects on the actin cytoskeleton, it is unclear whether and how Arg and cortactin affect each other's actin binding properties. We employ actin cosedimentation assays to show that Arg increases the stoichiometry of binding of cortactin to F-actin at saturation. Using a series of Arg deletion mutants and fragments, we demonstrate that the Arg C-terminal calponin homology domain is necessary and sufficient to increase the stoichiometry of binding of cortactin to F-actin. We also show that interactions between Arg and cortactin are required for optimal affinity between cortactin and the actin filament. Our data suggest a mechanism for Arg-dependent stimulation of binding of cortactin to F-actin, which may facilitate the recruitment of cortactin to sites of local actin network assembly.

  16. Chemotaxis and Actin Oscillations

    NASA Astrophysics Data System (ADS)

    Bodenschatz, Eberhard; Hsu, Hsin-Fang; Negrete, Jose; Beta, Carsten; Pumir, Alain; Gholami, Azam; Tarantola, Marco; Westendorf, Christian; Zykov, Vladimir

    Recently, self-oscillations of the cytoskeletal actin have been observed in Dictyostelium, a model system for studying chemotaxis. Here we report experimental results on the self-oscillation mechanism and the role of regulatory proteins and myosin II. We stimulate cells rapidly and periodically by using photo un-caging of the chemoattractant in a micro-fluidic device and measured the cellular responses. We found that the response amplitude grows with stimulation strength only in a very narrow region of stimulation, after which the response amplitude reaches a plateau. Moreover, the frequency-response is not constant but rather varies with the strength of external stimuli. To understand the underlying mechanism, we analyzed the polymerization and de-polymerization time in the single cell level. Despite of the large cell-to-cell variability, we found that the polymerization time is independent of external stimuli and the de-polymerization time is prolonged as the stimulation strength increases. Our conclusions will be summarized and the role of noise in the signaling network will be discussed. German Science Foundation CRC 937.

  17. Universal cable head for a multiconductor logging cable

    SciTech Connect

    Ip, M.

    1989-10-17

    This patent describes a universal cable head. It comprises: an armored logging cable having up to seven electrical conductors therein and incorporating a woven wire rope, and a surrounding armor wrap; stress relieving stinger means on the cable; an encircling housing to transfer axial loads from the cable to the housing; an internal transverse bulkhead within the housing adjacent to an internal cavity therein; electrical feedthrus for connection of conductors in the logging cable; exposed mating connectors electrically connected to the feedthrus; the housing extending past and encircling the mating connectors; and a rotatable, shoulder limited sleeve on the exterior of the housing having threading means thereon for connecting with a mating female connector.

  18. Ultrastructure and behavior of actin cytoskeleton during cell wall formation in the fission yeast Schizosaccharomyces pombe.

    PubMed

    Takagi, Tomoko; Ishijima, Sanae A; Ochi, Hisako; Osumi, Masako

    2003-01-01

    Fluorescence microscopy has shown that F-actin of the fission yeast Schizosaccharomyces pombe forms patch, cable and ring structures. To study the relationship between cell wall formation and the actin cytoskeleton, the process of cell wall regeneration from the protoplast was investigated by transmission electron microscopy (TEM), immunoelectron microscopy (IEM) and three-dimensional reconstruction analysis. During cell wall regeneration from the protoplast, localization of F-actin patches was similar to that of the newly synthesized cell wall materials, as shown by confocal laser scanning microscopy (CLSM). In serial sectioned TEM images, filasomes were spherical, 100-300 nm in diameter and consisted of a single microvesicle (35-70 nm diameter) surrounded by fine filaments. Filasomes were adjacent to the newly formed glucan fibrils in single, cluster or rosary forms. By IEM analysis, we found that colloidal gold particles indicating actin molecules were present in the filamentous area of filasomes. Three-dimensional reconstruction images of serial sections clarified that the distribution of filasomes corresponded to the distribution of F-actin patches revealed by CLSM. Thus, a filasome is one of the F-actin patch structures appearing in the cytoplasm at the site of the initial formation of the cell wall and it may play an important role in this action.

  19. Proper regulation of Cdc42 activity is required for tight actin concentration at the equator during cytokinesis in adherent mammalian cells.

    PubMed

    Zhu, Xiaodong; Wang, Junxia; Moriguchi, Kazuki; Liow, Lu Ting; Ahmed, Sohail; Kaverina, Irina; Murata-Hori, Maki

    2011-10-01

    Cytokinesis in mammalian cells requires actin assembly at the equatorial region. Although functions of RhoA in this process have been well established, additional mechanisms are likely involved. We have examined if Cdc42 is involved in actin assembly during cytokinesis. Depletion of Cdc42 had no apparent effects on the duration of cytokinesis, while overexpression of constitutively active Cdc42 (CACdc42) caused cytokinesis failure in normal rat kidney epithelial cells. Cells depleted of Cdc42 displayed abnormal cell morphology and caused a failure of tight accumulation of actin and RhoA at the equator. In contrast, in cells overexpressing CACdc42, actin formed abnormal bundles and RhoA was largely eliminated from the equator. Our results suggest that accurate regulation of Cdc42 activity is crucial for proper equatorial actin assembly and RhoA localization during cytokinesis. Notably, our observations also suggest that tight actin concentration is not essential for cytokinesis in adherent mammalian cells.

  20. Connecting high-performance carbon-fiber-reinforced polymer cables of suspension and cable-stayed bridges through the use of gradient materials

    NASA Astrophysics Data System (ADS)

    Meier, Urs; Farshad, Mehdi

    1996-08-01

    Carbon-fiber-reinforced polymer (CFRP) cables offer a very attractive combination of high specific strength and modulus (ratio of strength or modulus to density), outstanding fatigue performance, good corrosion resistance, and low axial thermal expansion. The high specific strength permits the design of structures with highly increased spans. The high specific modulus translates into a high relative equivalent modulus. This factor is very important in view of the deflection constraints imposed on large bridges. A relative high modulus coupled with a low mass density offer CFRP cables already an advantage for spans above 1000 m. Since 1980 EMPA has been developing CFRP cables for cable-stayed and suspension bridges that are produced as assemblies of parallel CFRP wires. The key problem facing the application of CFRP cables, and thus their widespread use in the future, is how to connect them. A new reliable anchoring scheme developed with computer-aided materials design and produced with advanced gradient materials based on ceramics and polymers is described. Early 1996 such CFRP cables with a load-carrying capacity of 12 MN (1200 metric tons) have been applied for the first time on a cable-stayed road bridge with a 124-m span. Each cable is built up from 241 CFRP wires having a diameter of 5 mm.

  1. Engineering an artificial amoeba propelled by nanoparticle-triggered actin polymerization

    NASA Astrophysics Data System (ADS)

    Yi, Jinsoo; Schmidt, Jacob; Chien, Aichi; Montemagno, Carlo D.

    2009-02-01

    We have engineered an amoeba system combining nanofabricated inorganic materials with biological components, capable of propelling itself via actin polymerization. The nanofabricated materials have a mechanism similar to the locomotion of the Listeria monocytogenes, food poisoning bacteria. The propulsive force generation utilizes nanoparticles made from nickel and gold functionalized with the Listeria monocytogenes transmembrane protein, ActA. These Listeria-mimic nanoparticles were in concert with actin, actin binding proteins, ATP (adenosine triphosphate) and encapsulated within a lipid vesicle. This system is an artificial cell, such as a vesicle, where artificial nanobacteria and actin polymerization machinery are used in driving force generators inside the cell. The assembled structure was observed to crawl on a glass surface analogously to an amoeba, with the speed of the movement dependent on the amount of actin monomers and ATP present.

  2. Self-organizing actin patterns shape membrane architecture but not cell mechanics

    PubMed Central

    Fritzsche, M.; Li, D.; Colin-York, H.; Chang, V. T.; Moeendarbary, E.; Felce, J. H.; Sezgin, E.; Charras, G.; Betzig, E.; Eggeling, C.

    2017-01-01

    Cell-free studies have demonstrated how collective action of actin-associated proteins can organize actin filaments into dynamic patterns, such as vortices, asters and stars. Using complementary microscopic techniques, we here show evidence of such self-organization of the actin cortex in living HeLa cells. During cell adhesion, an active multistage process naturally leads to pattern transitions from actin vortices over stars into asters. This process is primarily driven by Arp2/3 complex nucleation, but not by myosin motors, which is in contrast to what has been theoretically predicted and observed in vitro. Concomitant measurements of mechanics and plasma membrane fluidity demonstrate that changes in actin patterning alter membrane architecture but occur functionally independent of macroscopic cortex elasticity. Consequently, tuning the activity of the Arp2/3 complex to alter filament assembly may thus be a mechanism allowing cells to adjust their membrane architecture without affecting their macroscopic mechanical properties. PMID:28194011

  3. Engineering an artificial amoeba propelled by nanoparticle-triggered actin polymerization.

    PubMed

    Yi, Jinsoo; Schmidt, Jacob; Chien, Aichi; Montemagno, Carlo D

    2009-02-25

    We have engineered an amoeba system combining nanofabricated inorganic materials with biological components, capable of propelling itself via actin polymerization. The nanofabricated materials have a mechanism similar to the locomotion of the Listeria monocytogenes, food poisoning bacteria. The propulsive force generation utilizes nanoparticles made from nickel and gold functionalized with the Listeria monocytogenes transmembrane protein, ActA. These Listeria-mimic nanoparticles were in concert with actin, actin binding proteins, ATP (adenosine triphosphate) and encapsulated within a lipid vesicle. This system is an artificial cell, such as a vesicle, where artificial nanobacteria and actin polymerization machinery are used in driving force generators inside the cell. The assembled structure was observed to crawl on a glass surface analogously to an amoeba, with the speed of the movement dependent on the amount of actin monomers and ATP present.

  4. As functional nuclear actin comes into view, is it globular, filamentous, or both?

    PubMed Central

    Pederson, Thoru

    2008-01-01

    The idea that actin may have an important function in the nucleus has undergone a rapid transition from one greeted with skepticism to a now rapidly advancing research field. Actin has now been implicated in transcription by all three RNA polymerases, but the structural form it adopts in these processes remains unclear. Recently, a claim was made that monomeric nuclear actin plays a role in signal transduction, while a just-published study of RNA polymerase I transcription has implicated polymeric actin, consorting with an isoform of its classical partner myosin. Both studies are critically discussed here, and although there are several issues to be resolved, it now seems reasonable to start thinking about functions for both monomeric and assembled actin in the nucleus. PMID:18347069

  5. Self-organizing actin patterns shape membrane architecture but not cell mechanics

    NASA Astrophysics Data System (ADS)

    Fritzsche, M.; Li, D.; Colin-York, H.; Chang, V. T.; Moeendarbary, E.; Felce, J. H.; Sezgin, E.; Charras, G.; Betzig, E.; Eggeling, C.

    2017-02-01

    Cell-free studies have demonstrated how collective action of actin-associated proteins can organize actin filaments into dynamic patterns, such as vortices, asters and stars. Using complementary microscopic techniques, we here show evidence of such self-organization of the actin cortex in living HeLa cells. During cell adhesion, an active multistage process naturally leads to pattern transitions from actin vortices over stars into asters. This process is primarily driven by Arp2/3 complex nucleation, but not by myosin motors, which is in contrast to what has been theoretically predicted and observed in vitro. Concomitant measurements of mechanics and plasma membrane fluidity demonstrate that changes in actin patterning alter membrane architecture but occur functionally independent of macroscopic cortex elasticity. Consequently, tuning the activity of the Arp2/3 complex to alter filament assembly may thus be a mechanism allowing cells to adjust their membrane architecture without affecting their macroscopic mechanical properties.

  6. Shape adjustment of cable mesh reflector antennas considering modeling uncertainties

    NASA Astrophysics Data System (ADS)

    Du, Jingli; Bao, Hong; Cui, Chuanzhen

    2014-04-01

    Cable mesh antennas are the most important implement to construct large space antennas nowadays. Reflector surface of cable mesh antennas has to be carefully adjusted to achieve required accuracy, which is an effective way to compensate manufacturing and assembly errors or other imperfections. In this paper shape adjustment of cable mesh antennas is addressed. The required displacement of the reflector surface is determined with respect to a modified paraboloid whose axial vertex offset is also considered as a variable. Then the adjustment problem is solved by minimizing the RMS error with respect to the desired paraboloid using minimal norm least squares method. To deal with the modeling uncertainties, the adjustment is achieved by solving a simple worst-case optimization problem instead of directly using the least squares method. A numerical example demonstrates the worst-case method is of good convergence and accuracy, and is robust to perturbations.

  7. Rho GTPases, phosphoinositides, and actin

    PubMed Central

    Croisé, Pauline; Estay-Ahumada, Catherine; Gasman, Stéphane; Ory, Stéphane

    2014-01-01

    Rho GTPases are well known regulators of the actin cytoskeleton that act by binding and activating actin nucleators. They are therefore involved in many actin-based processes, including cell migration, cell polarity, and membrane trafficking. With the identification of phosphoinositide kinases and phosphatases as potential binding partners or effectors, Rho GTPases also appear to participate in the regulation of phosphoinositide metabolism. Since both actin dynamics and phosphoinositide turnover affect the efficiency and the fidelity of vesicle transport between cell compartments, Rho GTPases have emerged as critical players in membrane trafficking. Rho GTPase activity, actin remodeling, and phosphoinositide metabolism need to be coordinated in both space and time to ensure the progression of vesicles along membrane trafficking pathways. Although most molecular pathways are still unclear, in this review, we will highlight recent advances made in our understanding of how Rho-dependent signaling pathways organize actin dynamics and phosphoinositides and how phosphoinositides potentially provide negative feedback to Rho GTPases during endocytosis, exocytosis and membrane exchange between intracellular compartments. PMID:24914539

  8. Cable Television and Public Safety.

    ERIC Educational Resources Information Center

    Cranberg, Gilbert

    One of the most promising applications of cable television (CATV) is municipal surveillance of public areas for protection against crime, fire detection, control of air pollution, and traffic. Thus far, however, the CATV industry has made minimal efforts to realize the potential of CATV for community protection--the use of cable for public safety…

  9. What Belongs On the Cable.

    ERIC Educational Resources Information Center

    Ward, John E.

    Many papers and articles over the past few years have suggested that the coaxial cable television (CATV) cable carries sufficient bandwidth into and out of the home that it can serve almost every conceivable communications need--providing many television viewing channels; two-way data, audio and data services; the functions of the present…

  10. Cable Television in Sedalia, Missouri.

    ERIC Educational Resources Information Center

    Lamkin, Kathryn Janel

    A field study was conducted of the status of cable television in Sedalia, Missouri. Based on interviews of city council members and staff members of Cablevision, the Sedalia cable franchise holder, the following issues were investigated: (1) subscription rates; (2) franchise negotiations; (3) quality of existing services; and (4) possible…

  11. Cable Television: Notebook Number Five.

    ERIC Educational Resources Information Center

    Notebook, 1973

    1973-01-01

    Cable television has been introduced to the public as a revolutionary development in communications, but its history, evolving structure, and present operation indicate otherwise. A few large industrial conglomerates have come to dominate the field of cable television and studies by private institutions and the regulatory activities of the Federal…

  12. Polarized Exocytosis Induces Compensatory Endocytosis by Sec4p-Regulated Cortical Actin Polymerization

    PubMed Central

    Johansen, Jesper; Alfaro, Gabriel; Beh, Christopher T.

    2016-01-01

    Polarized growth is maintained by both polarized exocytosis, which transports membrane components to specific locations on the cell cortex, and endocytosis, which retrieves these components before they can diffuse away. Despite functional links between these two transport pathways, they are generally considered to be separate events. Using live cell imaging, in vivo and in vitro protein binding assays, and in vitro pyrene-actin polymerization assays, we show that the yeast Rab GTPase Sec4p couples polarized exocytosis with cortical actin polymerization, which induces endocytosis. After polarized exocytosis to the plasma membrane, Sec4p binds Las17/Bee1p (yeast Wiskott—Aldrich Syndrome protein [WASp]) in a complex with Sla1p and Sla2p during actin patch assembly. Mutations that inactivate Sec4p, or its guanine nucleotide exchange factor (GEF) Sec2p, inhibit actin patch formation, whereas the activating sec4-Q79L mutation accelerates patch assembly. In vitro assays of Arp2/3-dependent actin polymerization established that GTPγS-Sec4p overrides Sla1p inhibition of Las17p-dependent actin nucleation. These results support a model in which Sec4p relocates along the plasma membrane from polarized sites of exocytic vesicle fusion to nascent sites of endocytosis. Activated Sec4p then promotes actin polymerization and triggers compensatory endocytosis, which controls surface expansion and kinetically refines cell polarization. PMID:27526190

  13. A DOCK8-WIP-WASp complex links T cell receptors to the actin cytoskeleton

    PubMed Central

    Janssen, Erin; Tohme, Mira; Hedayat, Mona; Leick, Marion; Kumari, Sudha; Ramesh, Narayanaswamy; Massaad, Michel J.; Ullas, Sumana; Azcutia, Veronica; Goodnow, Christopher C.; Randall, Katrina L.; Qiao, Qi; Wu, Hao; Al-Herz, Waleed; Cox, Dianne; Hartwig, John; Irvine, Darrell J.; Luscinskas, Francis W.; Geha, Raif S.

    2016-01-01

    Wiskott-Aldrich syndrome (WAS) is associated with mutations in the WAS protein (WASp), which plays a critical role in the initiation of T cell receptor–driven (TCR-driven) actin polymerization. The clinical phenotype of WAS includes susceptibility to infection, allergy, autoimmunity, and malignancy and overlaps with the symptoms of dedicator of cytokinesis 8 (DOCK8) deficiency, suggesting that the 2 syndromes share common pathogenic mechanisms. Here, we demonstrated that the WASp-interacting protein (WIP) bridges DOCK8 to WASp and actin in T cells. We determined that the guanine nucleotide exchange factor activity of DOCK8 is essential for the integrity of the subcortical actin cytoskeleton as well as for TCR-driven WASp activation, F-actin assembly, immune synapse formation, actin foci formation, mechanotransduction, T cell transendothelial migration, and homing to lymph nodes, all of which also depend on WASp. These results indicate that DOCK8 and WASp are in the same signaling pathway that links TCRs to the actin cytoskeleton in TCR-driven actin assembly. Further, they provide an explanation for similarities in the clinical phenotypes of WAS and DOCK8 deficiency. PMID:27599296

  14. Workers in the VAB remove cable covers from STS-98 SRB's for inspection

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- In the Vehicle Assembly Building, United Space Alliance SRB technicians Robert G. Williams and Frank Meyer remove the cover of the solid rocket booster system tunnel. The SRB is part of Space Shuttle Atlantis, rolled back from Launch Pad 39A in order to conduct tests on the cables. A prior extensive evaluation of NASA'''s SRB cable inventory on the shelf revealed conductor damage in four (of about 200) cables. Shuttle managers decided to prove the integrity of the system tunnel cables already on Atlantis before launching. Workers are conducting inspections, making continuity checks and conducting X-ray analysis on the cables. The launch has been rescheduled no earlier than Feb. 6.

  15. Reaction-diffusion waves of actin filament polymerization/depolymerization in Dictyostelium pseudopodium extension and cell locomotion.

    PubMed

    Vicker, M G

    2000-04-14

    Cell surface movements and the intracellular spatial patterns and dynamics of actin filament (F-actin) were investigated in living and formalin-fixed cells of Dictyostelium discoideum by confocal microscopy. Excitation waves of F-actin assembly developed and propagated several micrometers at up to 26 microm/min in cells which had been intracellularly loaded with fluorescently labeled actin monomer. Wave propagation and extinction corresponded with the initiation and attenuation of pseudopodium extension and cell advance, respectively. The identification of chemical waves was supported by the ring, sphere, spiral and scroll wave patterns, which were observed in the extensions of fixed cells stained with phalloidin-rhodamine, and by the similar, asymmetrical [F-actin] distribution in wavefronts in living and fixed cells. These F-actin patterns and dynamics in Dictyostelium provide evidence for a new supramolecular state of actin, which propagates as a self-organized, reaction-diffusion wave of reversible F-actin assembly and affects pseudopodium extension. Actin's properties of oscillation and self-organization might also fundamentally determine the nature of the eukaryotic cell's reactions of adaptation, timing and signal response.

  16. Site-specific cation release drives actin filament severing by vertebrate cofilin

    PubMed Central

    Kang, Hyeran; Bradley, Michael J.; Cao, Wenxiang; Zhou, Kaifeng; Grintsevich, Elena E.; Michelot, Alphée; Sindelar, Charles V.; Hochstrasser, Mark; De La Cruz, Enrique M.

    2014-01-01

    Actin polymerization powers the directed motility of eukaryotic cells. Sustained motility requires rapid filament turnover and subunit recycling. The essential regulatory protein cofilin accelerates network remodeling by severing actin filaments and increasing the concentration of ends available for elongation and subunit exchange. Although cofilin effects on actin filament assembly dynamics have been extensively studied, the molecular mechanism of cofilin-induced filament severing is not understood. Here we demonstrate that actin filament severing by vertebrate cofilin is driven by the linked dissociation of a single cation that controls filament structure and mechanical properties. Vertebrate cofilin only weakly severs Saccharomyces cerevisiae actin filaments lacking this “stiffness cation” unless a stiffness cation-binding site is engineered into the actin molecule. Moreover, vertebrate cofilin rescues the viability of a S. cerevisiae cofilin deletion mutant only when the stiffness cation site is simultaneously introduced into actin, demonstrating that filament severing is the essential function of cofilin in cells. This work reveals that site-specific interactions with cations serve a key regulatory function in actin filament fragmentation and dynamics. PMID:25468977

  17. A coat of filamentous actin prevents clustering of late-endosomal vacuoles in vivo.

    PubMed

    Drengk, Anja; Fritsch, Jürgen; Schmauch, Christian; Rühling, Harald; Maniak, Markus

    2003-10-14

    The endocytic pathway depends on the actin cytoskeleton. Actin contributes to internalization at the plasma membrane and to subsequent trafficking steps like propulsion through the cytoplasm, fusion of phagosomes with early endosomes, and transport from early to late endosomes. In vitro studies with mammalian endosomes and yeast vacuoles implicate actin in membrane fusion. Here, we investigate the function of the actin coat that surrounds late endosomes in Dictyostelium. Latrunculin treatment leads to aggregation of these endosomes into grape-like clusters and completely blocks progression of endocytic marker. In addition, the cells round up and stop moving. Because this drug treatment perturbs all actin assemblies in the cell simultaneously, we used a novel targeting approach to specifically study the function of the cytoskeleton in one subcellular location. To this end, we constructed a hybrid protein targeting cofilin, an actin depolymerizing protein, to late endosomes. As a consequence, the endosomal compartments lost their actin coats and aggregated, but these cells remained morphologically normal, and the kinetics of endocytic marker trafficking were unaltered. Therefore, the actin coat prevents the clustering of endosomes, which could be one safeguard mechanism precluding their docking and fusion.

  18. Nucleus-associated actin in Amoeba proteus.

    PubMed

    Berdieva, Mariia; Bogolyubov, Dmitry; Podlipaeva, Yuliya; Goodkov, Andrew

    2016-10-01

    The presence, spatial distribution and forms of intranuclear and nucleus-associated cytoplasmic actin were studied in Amoeba proteus with immunocytochemical approaches. Labeling with different anti-actin antibodies and staining with TRITC-phalloidin and fluorescent deoxyribonuclease I were used. We showed that actin is abundant within the nucleus as well as in the cytoplasm of A. proteus cells. According to DNase I experiments, the predominant form of intranuclear actin is G-actin which is associated with chromatin strands. Besides, unpolymerized actin was shown to participate in organization of a prominent actin layer adjacent to the outer surface of nuclear envelope. No significant amount of F-actin was found in the nucleus. At the same time, the amoeba nucleus is enclosed in a basket-like structure formed by circumnuclear actin filaments and bundles connected with global cytoplasmic actin cytoskeleton. A supposed architectural function of actin filaments was studied by treatment with actin-depolymerizing agent latrunculin A. It disassembled the circumnuclear actin system, but did not affect the intranuclear chromatin structure. The results obtained for amoeba cells support the modern concept that actin is involved in fundamental nuclear processes that have evolved in the cells of multicellular organisms.

  19. Role of actin filaments in fusopod formation and osteoclastogenesis.

    PubMed

    Wang, Yongqiang; Brooks, Patricia Joyce; Jang, Janet Jinyoung; Silver, Alexandra Shade; Arora, Pamma D; McCulloch, Christopher A; Glogauer, Michael

    2015-07-01

    Cell fusion process is a critical, rate-limiting step in osteoclastogenesis but the mechanisms that regulate fusopod formation are not defined. We characterized fusopod generation in cultured pre-osteoclasts derived from cells stably transfected with a plasmid that expressed a short, actin filament binding peptide (Lifeact) fused to mEGFP that enables localization of actin filaments in living cells. Fusion was initiated at fusopods, which are cell extensions of width >2 μm and that are immunostained for myosin-X at the extension tips. Fusopods formed at the leading edge of larger migrating cells and from the tail of adjacent smaller cells, both of which migrated in the same direction. Staining for DC-STAMP was circumferential and did not localize to cell-cell fusion sites. Compared with wild-type cells, monocytes null for Rac1 exhibited 6-fold fewer fusopods and formed 4-fold fewer multinucleated osteoclasts. From time-lapse images we found that fusion was temporally related to the formation of coherent and spatially isolated bands of actin filaments that originated in cell bodies and extended into the fusopods. These bands of actin filaments were involved in cell fusion after approaching cells formed initial contacts. We conclude that the formation of fusopods is regulated by Rac1 to initiate intercellular contact during osteoclastogenesis. This step is followed by the tightly regulated assembly of bands of actin filaments in fusopods, which lead to closure of the intercellular gap and finally, cell fusion. These novel, actin-dependent processes are important for fusion processes in osteoclastogenesis.

  20. Contractile properties of thin (actin) filament-reconstituted muscle fibers.

    PubMed

    Ishiwata, S; Funatsu, T; Fujita, H

    1998-01-01

    Selective removal and reconstitution of the components of muscle fibers (fibrils) is a useful means of examining the molecular mechanism underlying the formation of the contractile apparatus. In addition, this approach is powerful for examining the structure-function relationship of a specific component of the contractile system. In previous studies, we have achieved the partial structural and functional reconstitution of thin filaments in the skeletal contractile apparatus and full reconstitution in the cardiac contractile apparatus. First, all thin filaments other than short fragments at the Z line were removed by treatment with plasma gelsolin, an actin filament-severing protein. Under these conditions, no active tension could be generated. By incorporating exogenous actin into these thin filament-free fibers, actin filaments were reconstituted by polymerization on the short actin fragments remaining at the Z line, and active tension, which was insensitive to Ca2+, was restored. The active tension after the reconstitution of thin filaments reached as high as 30% of the original level in skeletal muscle, while it reached 140% in cardiac muscle. The augmentation of tension in cardiac muscle is mainly attributable to the elongation of reconstituted filaments, longer than the average length of thin filaments in an intact muscle. These results indicate that a muscle contractile apparatus with a high order structure and function can be constructed by the self-assembly of constituent proteins. Recently, we applied this reconstitution system to the study of the mechanism of spontaneous oscillatory contraction (SPOC) in thin (actin) filament-reconstituted cardiac muscle fibers. As a result, we found that SPOC occurs even in regulatory protein-free actin filament-reconstituted fibers (Fujita & Ishiwata, manuscript submitted), although the SPOC conditions were slightly different from the standard SPOC conditions. This result strongly suggests that spontaneous oscillation

  1. Boolean gates on actin filaments

    NASA Astrophysics Data System (ADS)

    Siccardi, Stefano; Tuszynski, Jack A.; Adamatzky, Andrew

    2016-01-01

    Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications.

  2. Dual chemotaxis signalling regulates Dictyostelium development: intercellular cyclic AMP pulses and intracellular F-actin disassembly waves induce each other.

    PubMed

    Vicker, Michael G; Grutsch, James F

    2008-10-01

    Aggregating Dictyostelium discoideum amoebae periodically emit and relay cAMP, which regulates their chemotaxis and morphogenesis into a multicellular, differentiated organism. Cyclic AMP also stimulates F-actin assembly and chemotactic pseudopodium extension. We used actin-GFP expression to visualise for the first time intracellular F-actin assembly as a spatio-temporal indicator of cell reactions to cAMP, and thus the kinematics of cell communication, in aggregating streams. Every natural cAMP signal pulse induces an autowave of F-actin disassembly, which propagates from each cell's leading end to its trailing end at a linear rate, much slower than the calculated and measured velocities of cAMP diffusion in aggregating Dictyostelium. A sequence of transient reactions follows behind the wave, including anterior F-actin assembly, chemotactic pseudopodium extension and cell advance at the cell front and, at the back, F-actin assembly, extension of a small retrograde pseudopodium (forcing a brief cell retreat) and chemotactic stimulation of the following cell, yielding a 20s cAMP relay delay. These dynamics indicate that stream cell behaviour is mediated by a dual signalling system: a short-range cAMP pulse directed from one cell tail to an immediately following cell front and a slower, long-range wave of intracellular F-actin disassembly, each inducing the other.

  3. Competition in the Pay Cable Industry.

    ERIC Educational Resources Information Center

    Albarran, Alan B.

    This paper analyzes the state of competition in the pay cable industry. The analysis conceptualizes competition in pay cable and discusses the current structure of the pay cable industry and the competition for subscribers and programming. The competition for audiences that pay cable faces from both pay-per-view services and the video cassette…

  4. Cable Television: Citizen Participation in Planning.

    ERIC Educational Resources Information Center

    Yin, Robert K.

    The historical background of citizen participation in local affairs and its relevance at the onset of community concern about cable television are briefly discussed in this report. The participation of citizens, municipal officials, and cable operators in laying the groundwork for a cable system as well as the pros and cons of cable television as…

  5. Cable in Connecticut; a Citizen's Handbook.

    ERIC Educational Resources Information Center

    Cleland, Margaret

    This handbook for Connecticut cable television consumers addresses a variety of topics, including: (1) a definition of cable television services; (2) the public stake in cable television; (3) program variety; (4) pay cable service; (5) public satellites; (6) government regulation; (7) proposed regulation; (8) role of the Connecticut Public…

  6. 14 CFR 27.1365 - Electric cables.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Electric cables. 27.1365 Section 27.1365... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1365 Electric cables. (a) Each electric connecting cable must be of adequate capacity. (b) Each cable that would...

  7. 14 CFR 27.1365 - Electric cables.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Electric cables. 27.1365 Section 27.1365... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1365 Electric cables. (a) Each electric connecting cable must be of adequate capacity. (b) Each cable that would...

  8. 14 CFR 27.1365 - Electric cables.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Electric cables. 27.1365 Section 27.1365... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1365 Electric cables. (a) Each electric connecting cable must be of adequate capacity. (b) Each cable that would...

  9. 14 CFR 27.1365 - Electric cables.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Electric cables. 27.1365 Section 27.1365... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1365 Electric cables. (a) Each electric connecting cable must be of adequate capacity. (b) Each cable that would...

  10. 14 CFR 27.1365 - Electric cables.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Electric cables. 27.1365 Section 27.1365... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1365 Electric cables. (a) Each electric connecting cable must be of adequate capacity. (b) Each cable that would...

  11. Cable Modem Technology Implementation: Challenges and Prospects.

    ERIC Educational Resources Information Center

    Littman, Marlyn Kemper

    1998-01-01

    Describes cable modem technology (i.e., an external device that facilitates high-speed access to the Internet via the same network configuration employed for cable television). Examples of cable field trials carried out in collaboration with educational user communities are presented, and cable technical capabilities, advantages, and constraints…

  12. Technical advance: identification of plant actin-binding proteins by F-actin affinity chromatography

    NASA Technical Reports Server (NTRS)

    Hu, S.; Brady, S. R.; Kovar, D. R.; Staiger, C. J.; Clark, G. B.; Roux, S. J.; Muday, G. K.

    2000-01-01

    Proteins that interact with the actin cytoskeleton often modulate the dynamics or organization of the cytoskeleton or use the cytoskeleton to control their localization. In plants, very few actin-binding proteins have been identified and most are thought to modulate cytoskeleton function. To identify actin-binding proteins that are unique to plants, the development of new biochemical procedures will be critical. Affinity columns using actin monomers (globular actin, G-actin) or actin filaments (filamentous actin, F-actin) have been used to identify actin-binding proteins from a wide variety of organisms. Monomeric actin from zucchini (Cucurbita pepo L.) hypocotyl tissue was purified to electrophoretic homogeneity and shown to be native and competent for polymerization to actin filaments. G-actin, F-actin and bovine serum albumin affinity columns were prepared and used to separate samples enriched in either soluble or membrane-associated actin-binding proteins. Extracts of soluble actin-binding proteins yield distinct patterns when eluted from the G-actin and F-actin columns, respectively, leading to the identification of a putative F-actin-binding protein of approximately 40 kDa. When plasma membrane-associated proteins were applied to these columns, two abundant polypeptides eluted selectively from the F-actin column and cross-reacted with antiserum against pea annexins. Additionally, a protein that binds auxin transport inhibitors, the naphthylphthalamic acid binding protein, which has been previously suggested to associate with the actin cytoskeleton, was eluted in a single peak from the F-actin column. These experiments provide a new approach that may help to identify novel actin-binding proteins from plants.

  13. 105. VIEW NORTH FROM SLC3W CABLE TUNNEL INTO CABLE VAULT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    105. VIEW NORTH FROM SLC-3W CABLE TUNNEL INTO CABLE VAULT AND SLC-3E CABLE TUNNEL. NOTE WOODEN PLANKING ON FLOOR OF TUNNEL AND CABLE TRAYS LINING TUNNEL WALLS. STAIRS ON EAST WALL OF CABLE VAULT LEAD INTO LANDLINE INSTRUMENTATION ROOM. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Operations Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  14. Fully synthetic taped insulation cables

    DOEpatents

    Forsyth, E.B.; Muller, A.C.

    1983-07-15

    The present invention is a cable which, although constructed from inexpensive polyolefin tapes and using typical impregnating oils, furnishes high voltage capability up to 765 kV, and has such excellent dielectric characteristics and heat transfer properties that it is capable of operation at capacities equal to or higher than presently available cables at a given voltage. This is accomplished by using polyethylene, polybutene or polypropylene insulating tape which has been specially processed to attain properties which are not generally found in these materials, but are required for their use in impregnated electrical cables. Chief among these properties is compatibility with impregnating oil.

  15. IntelliCable Interface Specification

    DTIC Science & Technology

    2016-07-14

    Specification Page 9 Layer 1 – Physical Each IntelliCable shall identify its capabilities and needed output using a 1- Wire storage and signaling...device. Some informative sites are listed below:  Dallas Semi / Maxim – http://www.maxim-ic.com/products/1- wire /  1- Wire industry standards – http...www.1wire.org A typical IntelliCable will use a simple memory device, such as a DS2431. Other cables may use 1- Wire devices with built-in sense

  16. Robot cable-compliant devices

    NASA Technical Reports Server (NTRS)

    Kerley, James J., Jr. (Inventor)

    1990-01-01

    A cable compliant robotic joint includes two U configuration cross section brackets with their U cross sections lying in different planes, one of their brackets being connected to a robot arm and the other to a tool. Additional angle brackets are displaced from the other brackets at corners of the robotic joint. All the brackets are connected by cable segments which lie in one or more planes which are perpendicular to the direction of tool travel as it approaches a work object. The compliance of the joint is determined by the cable segment characteristics, such as their length, material, angle, stranding, pretwisting, and prestressing.

  17. The role of cyclase-associated protein in regulating actin filament dynamics - more than a monomer-sequestration factor.

    PubMed

    Ono, Shoichiro

    2013-08-01

    Dynamic reorganization of the actin cytoskeleton is fundamental to a number of cell biological events. A variety of actin-regulatory proteins modulate polymerization and depolymerization of actin and contribute to actin cytoskeletal reorganization. Cyclase-associated protein (CAP) is a conserved actin-monomer-binding protein that has been studied for over 20 years. Early studies have shown that CAP sequesters actin monomers; recent studies, however, have revealed more active roles of CAP in actin filament dynamics. CAP enhances the recharging of actin monomers with ATP antagonistically to ADF/cofilin, and also promotes the severing of actin filaments in cooperation with ADF/cofilin. Self-oligomerization and binding to other proteins regulate activities and localization of CAP. CAP has crucial roles in cell signaling, development, vesicle trafficking, cell migration and muscle sarcomere assembly. This Commentary discusses the recent advances in our understanding of the functions of CAP and its implications as an important regulator of actin cytoskeletal dynamics, which are involved in various cellular activities.

  18. Phosphatidylinositol 3-Kinase-Associated Protein (PI3KAP)/XB130 Crosslinks Actin Filaments through Its Actin Binding and Multimerization Properties In Vitro and Enhances Endocytosis in HEK293 Cells

    PubMed Central

    Yamanaka, Daisuke; Akama, Takeshi; Chida, Kazuhiro; Minami, Shiro; Ito, Koichi; Hakuno, Fumihiko; Takahashi, Shin-Ichiro

    2016-01-01

    Actin-crosslinking proteins control actin filament networks and bundles and contribute to various cellular functions including regulation of cell migration, cell morphology, and endocytosis. Phosphatidylinositol 3-kinase-associated protein (PI3KAP)/XB130 has been reported to be localized to actin filaments (F-actin) and required for cell migration in thyroid carcinoma cells. Here, we show a role for PI3KAP/XB130 as an actin-crosslinking protein. First, we found that the carboxyl terminal region of PI3KAP/XB130 containing amino acid residues 830–840 was required and sufficient for localization to F-actin in NIH3T3 cells, and this region is directly bound to F-actin in vitro. Moreover, actin-crosslinking assay revealed that recombinant PI3KAP/XB130 crosslinked F-actin. In general, actin-crosslinking proteins often multimerize to assemble multiple actin-binding sites. We then investigated whether PI3KAP/XB130 could form a multimer. Blue native-PAGE analysis showed that recombinant PI3KAP/XB130 was detected at 250–1200 kDa although the molecular mass was approximately 125 kDa, suggesting that PI3KAP/XB130 formed multimers. Furthermore, we found that the amino terminal 40 amino acids were required for this multimerization by co-immunoprecipitation assay in HEK293T cells. Deletion mutants of PI3KAP/XB130 lacking the actin-binding region or the multimerizing region did not crosslink actin filaments, indicating that actin binding and multimerization of PI3KAP/XB130 were necessary to crosslink F-actin. Finally, we examined roles of PI3KAP/XB130 on endocytosis, an actin-related biological process. Overexpression of PI3KAP/XB130 enhanced dextran uptake in HEK 293 cells. However, most of the cells transfected with the deletion mutant lacking the actin-binding region incorporated dextran to a similar extent as control cells. Taken together, these results demonstrate that PI3KAP/XB130 crosslinks F-actin through both its actin-binding region and multimerizing region and

  19. Bacterial Actins? An Evolutionary Perspective

    NASA Technical Reports Server (NTRS)

    Doolittle, Russell F.; York, Amanda L.

    2003-01-01

    According to the conventional wisdom, the existence of a cytoskeleton in eukaryotes and its absence in prokaryotes constitute a fundamental divide between the two domains of life. An integral part of the dogma is that a cytoskeleton enabled an early eukaryote to feed upon prokaryotes, a consequence of which was the occasional endosymbiosis and the eventual evolution of organelles. Two recent papers present compelling evidence that actin, one of the principal components of a cytoskeleton, has a homolog in Bacteria that behaves in many ways like eukaryotic actin. Sequence comparisons reveml that eukaryotic actin and the bacterial homolog (mreB protein), unlike many other proteins common to eukaryotes and Bacteria, have very different and more highly extended evolutionary histories.

  20. Actin polymerization is stimulated by actin cross-linking protein palladin.

    PubMed

    Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G; Orlova, Albina; Egelman, Edward H; Beck, Moriah R

    2016-02-15

    The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the co-ordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. In the present study, we show that the actin-binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro cross-linking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of globular or monomeric actin (G-actin), akin to metal ions, either through charge neutralization or through conformational changes.

  1. Optimal treatment of actinic keratoses

    PubMed Central

    Uhlenhake, Elizabeth E

    2013-01-01

    The most compelling reason and primary goal of treating actinic keratoses is to prevent malignant transformation into invasive squamous cell carcinoma, and although there are well established guidelines outlining treatment modalities and regimens for squamous cell carcinoma, the more commonly encountered precancerous actinic lesions have no such standard. Many options are available with variable success and patient compliance rates. Prevention of these lesions is key, with sun protection being a must in treating aging patients with sun damage as it is never too late to begin protecting the skin. PMID:23345970

  2. Fascin regulates nuclear actin during Drosophila oogenesis

    PubMed Central

    Kelpsch, Daniel J.; Groen, Christopher M.; Fagan, Tiffany N.; Sudhir, Sweta; Tootle, Tina L.

    2016-01-01

    Drosophila oogenesis provides a developmental system with which to study nuclear actin. During Stages 5–9, nuclear actin levels are high in the oocyte and exhibit variation within the nurse cells. Cofilin and Profilin, which regulate the nuclear import and export of actin, also localize to the nuclei. Expression of GFP-tagged Actin results in nuclear actin rod formation. These findings indicate that nuclear actin must be tightly regulated during oogenesis. One factor mediating this regulation is Fascin. Overexpression of Fascin enhances nuclear GFP-Actin rod formation, and Fascin colocalizes with the rods. Loss of Fascin reduces, whereas overexpression of Fascin increases, the frequency of nurse cells with high levels of nuclear actin, but neither alters the overall nuclear level of actin within the ovary. These data suggest that Fascin regulates the ability of specific cells to accumulate nuclear actin. Evidence indicates that Fascin positively regulates nuclear actin through Cofilin. Loss of Fascin results in decreased nuclear Cofilin. In addition, Fascin and Cofilin genetically interact, as double heterozygotes exhibit a reduction in the number of nurse cells with high nuclear actin levels. These findings are likely applicable beyond Drosophila follicle development, as the localization and functions of Fascin and the mechanisms regulating nuclear actin are widely conserved. PMID:27535426

  3. Process of modifying a cable end

    DOEpatents

    Roose, L.D.

    1995-08-01

    End moldings for high-voltage cables are described wherein the dielectric insulator of the cable is heated and molded to conform to a desired shape. As a consequence, high quality substantially bubble-free cable connectors suitable for mating to premanufactured fittings are made. Disclosed are a method for making the cable connectors either in the field or in a factory, molds suitable for use with the method, and the molded cable connectors, themselves. 5 figs.

  4. Crystallization of fluorescent quantum dots within a three-dimensional bio-organic template of actin filaments and lipid membranes.

    PubMed

    Henry, Etienne; Dif, Aurélien; Schmutz, Marc; Legoff, Loic; Amblard, François; Marchi-Artzner, Valérie; Artzner, Franck

    2011-12-14

    Biological molecules and molecular self-assemblies are promising templates to organize well-defined inorganic nanostructures. We demonstrate the ability of a self-assembled three-dimensional crystal template of helical actin protein filaments and lipids bilayers to generate a hierarchical self-assembly of quantum dots. Functionnalized tricystein peptidic quantum dots (QDs) are incorporated during the dynamical self-assembly of this actin/lipid template resulting in the formation of crystalline fibers. The crystal parameters, 26.5×18.9×35.5 nm3, are imposed by the membrane thickness, the diameter, and the pitch of the actin self-assembly. This process ensures the high quality of the crystal and results in unexpected fluorescence properties. This method of preparation offers opportunities to generate crystals with new symmetries and a large range of distance parameters.

  5. Cable Television in Extension Education.

    ERIC Educational Resources Information Center

    Waldron, Mark W.

    1978-01-01

    The experience of producing and presenting two continuing education courses on cable television proved that this technique can be a valuable additional means of presenting courses, complementing classroom discussions, and efficiently extending the university into the community. (Author)

  6. Cable SGEMP Code Validation Study

    SciTech Connect

    Ballard, William Parker

    2013-05-01

    This report compared data taken on the Modular Bremsstrahlung Simulator using copper jacketed (cujac) cables with calculations using the RHSD-RA Cable SGEMP analysis tool. The tool relies on CEPXS/ONBFP to perform radiation transport in a series of 1D slices through the cable, and then uses a Green function technique to evaluate the expected current drive on the center conductor. The data were obtained in 2003 as part of a Cabana verification and validation experiment using 1-D geometries, but were not evaluated until now. The agreement between data and model is not adequate unless gaps between the dielectric and outer conductor (ground) are assumed, and these gaps are large compared with what is believed to be in the actual cable.

  7. Plant villin, lily P-135-ABP, possesses G-actin binding activity and accelerates the polymerization and depolymerization of actin in a Ca2+-sensitive manner.

    PubMed

    Yokota, Etsuo; Tominaga, Motoki; Mabuchi, Issei; Tsuji, Yasunori; Staiger, Christopher J; Oiwa, Kazuhiro; Shimmen, Teruo

    2005-10-01

    From germinating pollen of lily, two types of villins, P-115-ABP and P-135-ABP, have been identified biochemically. Ca(2+)-CaM-dependent actin-filament binding and bundling activities have been demonstrated for both villins previously. Here, we examined the effects of lily villins on the polymerization and depolymerization of actin. P-115-ABP and P-135-ABP present in a crude protein extract prepared from germinating pollen bound to a DNase I affinity column in a Ca(2+)-dependent manner. Purified P-135-ABP reduced the lag period that precedes actin filament polymerization from monomers in the presence of either Ca(2+) or Ca(2+)-CaM. These results indicated that P-135-ABP can form a complex with G-actin in the presence of Ca(2+) and this complex acts as a nucleus for polymerization of actin filaments. However, the nucleation activity of P-135-ABP is probably not relevant in vivo because the assembly of G-actin saturated with profilin, a situation that mimics conditions found in pollen, was not accelerated in the presence of P-135-ABP. P-135-ABP also enhanced the depolymerization of actin filaments during dilution-mediated disassembly. Growth from filament barbed ends in the presence of Ca(2+)-CaM was also prevented, consistent with filament capping activity. These results suggested that lily villin is involved not only in the arrangement of actin filaments into bundles in the basal and shank region of the pollen tube, but also in regulating and modulating actin dynamics through its capping and depolymerization (or fragmentation) activities in the apical region of the pollen tube, where there is a relatively high concentration of Ca(2+).

  8. miR-24 triggers epidermal differentiation by controlling actin adhesion and cell migration

    PubMed Central

    Amelio, Ivano; Lena, Anna Maria; Viticchiè, Giuditta; Shalom-Feuerstein, Ruby; Terrinoni, Alessandro; Dinsdale, David; Russo, Giandomenico; Fortunato, Claudia; Bonanno, Elena; Spagnoli, Luigi Giusto; Aberdam, Daniel; Knight, Richard Austen

    2012-01-01

    During keratinocyte differentiation and stratification, cells undergo extensive remodeling of their actin cytoskeleton, which is important to control cell mobility and to coordinate and stabilize adhesive structures necessary for functional epithelia. Limited knowledge exists on how the actin cytoskeleton is remodeled in epithelial stratification and whether cell shape is a key determinant to trigger terminal differentiation. In this paper, using human keratinocytes and mouse epidermis as models, we implicate miR-24 in actin adhesion dynamics and demonstrate that miR-24 directly controls actin cable formation and cell mobility. miR-24 overexpression in proliferating cells was sufficient to trigger keratinocyte differentiation both in vitro and in vivo and directly repressed cytoskeletal modulators (PAK4, Tks5, and ArhGAP19). Silencing of these targets recapitulated the effects of miR-24 overexpression. Our results uncover a new regulatory pathway involving a differentiation-promoting microribonucleic acid that regulates actin adhesion dynamics in human and mouse epidermis. PMID:23071155

  9. Fully synthetic taped insulation cables

    DOEpatents

    Forsyth, Eric B.; Muller, Albert C.

    1984-01-01

    A high voltage oil-impregnated electrical cable with fully polymer taped insulation operable to 765 kV. Biaxially oriented, specially processed, polyethylene, polybutene or polypropylene tape with an embossed pattern is wound in multiple layers over a conductive core with a permeable screen around the insulation. Conventional oil which closely matches the dielectric constant of the tape is used, and the cable can be impregnated after field installation because of its excellent impregnation characteristics.

  10. Nuclear instrumentation cable end seal

    DOEpatents

    Cannon, Collins P.; Brown, Donald P.

    1979-01-01

    An improved coaxial end seal for hermetically sealed nuclear instrumentation cable exhibiting an improved breakdown pulse noise characteristic under high voltage, high temperature conditions. A tubular insulator body has metallized interior and exterior surface portions which are braze sealed to a center conductor and an outer conductive sheath. The end surface of the insulator body which is directed toward the coaxial cable to which it is sealed has a recessed surface portion within which the braze seal material terminates.

  11. ATP-dependent regulation of actin monomer-filament equilibrium by cyclase-associated protein and ADF/cofilin.

    PubMed

    Nomura, Kazumi; Ono, Shoichiro

    2013-07-15

    CAP (cyclase-associated protein) is a conserved regulator of actin filament dynamics. In the nematode Caenorhabditis elegans, CAS-1 is an isoform of CAP that is expressed in striated muscle and regulates sarcomeric actin assembly. In the present study, we report that CAS-2, a second CAP isoform in C. elegans, attenuates the actin-monomer-sequestering effect of ADF (actin depolymerizing factor)/cofilin to increase the steady-state levels of actin filaments in an ATP-dependent manner. CAS-2 binds to actin monomers without a strong preference for either ATP- or ADP-actin. CAS-2 strongly enhances the exchange of actin-bound nucleotides even in the presence of UNC-60A, a C. elegans ADF/cofilin that inhibits nucleotide exchange. UNC-60A induces the depolymerization of actin filaments and sequesters actin monomers, whereas CAS-2 reverses the monomer-sequestering effect of UNC-60A in the presence of ATP, but not in the presence of only ADP or the absence of ATP or ADP. A 1:100 molar ratio of CAS-2 to UNC-60A is sufficient to increase actin filaments. CAS-2 has two independent actin-binding sites in its N- and C-terminal halves, and the C-terminal half is necessary and sufficient for the observed activities of the full-length CAS-2. These results suggest that CAS-2 (CAP) and UNC-60A (ADF/cofilin) are important in the ATP-dependent regulation of the actin monomer-filament equilibrium.

  12. Motility of Electric Cable Bacteria

    PubMed Central

    Damgaard, Lars Riis; Holm, Simon Agner; Schramm, Andreas; Nielsen, Lars Peter

    2016-01-01

    ABSTRACT Cable bacteria are filamentous bacteria that electrically couple sulfide oxidation and oxygen reduction at centimeter distances, and observations in sediment environments have suggested that they are motile. By time-lapse microscopy, we found that cable bacteria used gliding motility on surfaces with a highly variable speed of 0.5 ± 0.3 μm s−1 (mean ± standard deviation) and time between reversals of 155 ± 108 s. They frequently moved forward in loops, and formation of twisted loops revealed helical rotation of the filaments. Cable bacteria responded to chemical gradients in their environment, and around the oxic-anoxic interface, they curled and piled up, with straight parts connecting back to the source of sulfide. Thus, it appears that motility serves the cable bacteria in establishing and keeping optimal connections between their distant electron donor and acceptors in a dynamic sediment environment. IMPORTANCE This study reports on the motility of cable bacteria, capable of transmitting electrons over centimeter distances. It gives us a new insight into their behavior in sediments and explains previously puzzling findings. Cable bacteria greatly influence their environment, and this article adds significantly to the body of knowledge about this organism. PMID:27084019

  13. Antibodies to Actin in Autoimmune Neutropenia

    DTIC Science & Technology

    1990-02-01

    protein as actin. Purified Acanthamoeba actin by anti-neutrophil antibodies in autoimmune neutropenia, comigrated with the protein and was specifically...anti-rabbit IgG were obtained from ICN Immunobiolog- formed using purified Acanthamoeba actin (gift of Dr Blair Bowers. icals, Naperville, IL. Cells...preparations𔃼 1 - was the protein recognized by these anti-neutrophil antibody 6 .2- positive sera, lgG, and F(ab’) 2. Purified Acanthamoeba actin

  14. An actin cytoskeleton with evolutionarily conserved functions in the absence of canonical actin-binding proteins

    PubMed Central

    Paredez, Alexander R.; Assaf, Zoe June; Sept, David; Timofejeva, Ljudmilla; Dawson, Scott C.; Wang, Chung-Ju Rachel; Cande, W. Z.

    2011-01-01

    Giardia intestinalis, a human intestinal parasite and member of what is perhaps the earliest-diverging eukaryotic lineage, contains the most divergent eukaryotic actin identified to date and is the first eukaryote known to lack all canonical actin-binding proteins (ABPs). We sought to investigate the properties and functions of the actin cytoskeleton in Giardia to determine whether Giardia actin (giActin) has reduced or conserved roles in core cellular processes. In vitro polymerization of giActin produced filaments, indicating that this divergent actin is a true filament-forming actin. We generated an anti-giActin antibody to localize giActin throughout the cell cycle. GiActin localized to the cortex, nuclei, internal axonemes, and formed C-shaped filaments along the anterior of the cell and a flagella-bundling helix. These structures were regulated with the cell cycle and in encysting cells giActin was recruited to the Golgi-like cyst wall processing vesicles. Knockdown of giActin demonstrated that giActin functions in cell morphogenesis, membrane trafficking, and cytokinesis. Additionally, Giardia contains a single G protein, giRac, which affects the Giardia actin cytoskeleton independently of known target ABPs. These results imply that there exist ancestral and perhaps conserved roles for actin in core cellular processes that are independent of canonical ABPs. Of medical significance, the divergent giActin cytoskeleton is essential and commonly used actin-disrupting drugs do not depolymerize giActin structures. Therefore, the giActin cytoskeleton is a promising drug target for treating giardiasis, as we predict drugs that interfere with the Giardia actin cytoskeleton will not affect the mammalian host. PMID:21444821

  15. An actin cytoskeleton with evolutionarily conserved functions in the absence of canonical actin-binding proteins.

    PubMed

    Paredez, Alexander R; Assaf, Zoe June; Sept, David; Timofejeva, Ljudmilla; Dawson, Scott C; Wang, Chung-Ju Rachel; Cande, W Z

    2011-04-12

    Giardia intestinalis, a human intestinal parasite and member of what is perhaps the earliest-diverging eukaryotic lineage, contains the most divergent eukaryotic actin identified to date and is the first eukaryote known to lack all canonical actin-binding proteins (ABPs). We sought to investigate the properties and functions of the actin cytoskeleton in Giardia to determine whether Giardia actin (giActin) has reduced or conserved roles in core cellular processes. In vitro polymerization of giActin produced filaments, indicating that this divergent actin is a true filament-forming actin. We generated an anti-giActin antibody to localize giActin throughout the cell cycle. GiActin localized to the cortex, nuclei, internal axonemes, and formed C-shaped filaments along the anterior of the cell and a flagella-bundling helix. These structures were regulated with the cell cycle and in encysting cells giActin was recruited to the Golgi-like cyst wall processing vesicles. Knockdown of giActin demonstrated that giActin functions in cell morphogenesis, membrane trafficking, and cytokinesis. Additionally, Giardia contains a single G protein, giRac, which affects the Giardia actin cytoskeleton independently of known target ABPs. These results imply that there exist ancestral and perhaps conserved roles for actin in core cellular processes that are independent of canonical ABPs. Of medical significance, the divergent giActin cytoskeleton is essential and commonly used actin-disrupting drugs do not depolymerize giActin structures. Therefore, the giActin cytoskeleton is a promising drug target for treating giardiasis, as we predict drugs that interfere with the Giardia actin cytoskeleton will not affect the mammalian host.

  16. F-actin buckling coordinates contractility and severing in a biomimetic actomyosin cortex

    PubMed Central

    Murrell, Michael P.; Gardel, Margaret L.

    2012-01-01

    Here we develop a minimal model of the cell actomyosin cortex by forming a quasi-2D cross-linked filamentous actin (F-actin) network adhered to a model cell membrane and contracted by myosin thick filaments. Myosin motors generate both compressive and tensile stresses on F-actin and consequently induce large bending fluctuations, which reduces their effective persistence length to <1 μm. Over a large range of conditions, we show the extent of network contraction corresponds exactly to the extent of individual F-actin shortening via buckling. This demonstrates an essential role of buckling in breaking the symmetry between tensile and compressive stresses to facilitate mesoscale network contraction of up to 80% strain. Portions of buckled F-actin with a radius of curvature ∼300 nm are prone to severing and thus compressive stresses mechanically coordinate contractility with F-actin severing, the initial step of F-actin turnover. Finally, the F-actin curvature acquired by myosin-induced stresses can be further constrained by adhesion of the network to a membrane, accelerating filament severing but inhibiting the long-range transmission of the stresses necessary for network contractility. Thus, the extent of membrane adhesion can regulate the coupling between network contraction and F-actin severing. These data demonstrate the essential role of the nonlinear response of F-actin to compressive stresses in potentiating both myosin-mediated contractility and filament severing. This may serve as a general mechanism to mechanically coordinate contractility and cortical dynamics across diverse actomyosin assemblies in smooth muscle and nonmuscle cells. PMID:23213249

  17. Installation and Assembly, Electrical Ground Support Equipment (GSE), Specification for

    NASA Technical Reports Server (NTRS)

    Denson, Erik C.

    2014-01-01

    This specification covers the general workmanship requirements and procedures for the complete installation and assembly of electrical ground support equipment (EGSE) such as terminal distributors, junction boxes, conduit and fittings, cable trays and accessories, interconnecting cables (including routing requirements), motor-control equipment, and necessary hardware as specified by the applicable contract and drawings.

  18. Actinic cheilitis in dental practice.

    PubMed

    Savage, N W; McKay, C; Faulkner, C

    2010-06-01

    Actinic cheilitis is a potentially premalignant condition involving predominantly the vermilion of the lower lip. The aim of the current paper was to review the clinical presentation of actinic cheilitis and demonstrate the development of management plans using a series of cases. These are designed to provide immediate treatment where required but also to address the medium and long-term requirements of the patient. The authors suggest that the clinical examination of lips and the assessment of actinic cheilitis and other lip pathology become a regular part of the routine soft tissue examination undertaken as a part of the periodic examination of dental patients. Early recognition of actinic cheilitis can allow the development of strategies for individual patients that prevent progression. These are based on past sun exposure, future lifestyle changes and the daily use of emollient sunscreens, broad-brimmed hats and avoidance of sun exposure during the middle of the day. This is a service that is not undertaken as a matter of routine in general medical practice as patients are not seen with the regularity of dental patients and generally not under the ideal examination conditions available in the dental surgery.

  19. Actin Polymerization Is Essential for Pollen Tube GrowthV⃞

    PubMed Central

    Vidali, Luis; McKenna, Sylvester T.; Hepler, Peter K.

    2001-01-01

    Actin microfilaments, which are prominent in pollen tubes, have been implicated in the growth process; however, their mechanism of action is not well understood. In the present work we have used profilin and DNAse I injections, as well as latrunculin B and cytochalasin D treatments, under quantitatively controlled conditions, to perturb actin microfilament structure and assembly in an attempt to answer this question. We found that a ∼50% increase in the total profilin pool was necessary to half-maximally inhibit pollen tube growth, whereas a ∼100% increase was necessary for half-maximal inhibition of cytoplasmic streaming. DNAse I showed a similar inhibitory activity but with a threefold more pronounced effect on growth than streaming. Latrunculin B, at only 1–4 nM in the growth medium, has a similar proportion of inhibition of growth over streaming to that of profilin. The fact that tip growth is more sensitive than streaming to the inhibitory substances and that there is no correlation between streaming and growth rates suggests that tip growth requires actin assembly in a process independent of cytoplasmic streaming. PMID:11514633

  20. Coaxial cable connector swaging technique. Final report

    SciTech Connect

    Stephens, J.M.

    1986-03-01

    This project was established to investigate swaging small copper tubes onto the ends of the braided shield and twisted center conductor of a coaxial cable. The physical size, electrical characteristics, and mechanical strength of the swaged connection are the important parameters. A market search revealed that the swaging should be done in-house. The necessary tooling was purchased, and a formula was derived for designing the tubes. Subsequently, tubes were swaged onto appropriate wire, cut to specific lengths, and the electrical and mechanical characteristics tested. The testing done was insufficient to optimize the final connection versus assembly parameters. However, an approach was determined for any further work in developing and improving the connection as well as providing a connection that satisfies the preliminary drawing requirements.

  1. Fluid assisted installation of electrical cable accessories

    DOEpatents

    Mayer, Robert W.; Silva, Frank A.

    1977-01-01

    An electrical cable accessory includes a generally tubular member of elastomeric material which is to be installed by placement over a cylindrical surface to grip the cylindrical surface, when in appropriate assembled relation therewith, with a predetermined gripping force established by dilation of the tubular member, the installation being facilitated by introducing fluid under pressure, through means provided in the tubular member, between the tubular member and the cylindrical surface, and simultaneously impeding the escape of the fluid under pressure from between the tubular member and the cylindrical surface by means adjacent one of the ends of the tubular member to cause dilation of the tubular member and establish a fluid layer between the tubular member and the cylindrical surface, thereby reducing the gripping force during installation.

  2. Actin crosslinkers: repairing the sense of touch.

    PubMed

    Sun, Sean X; Walcott, Sam

    2010-10-26

    Cells use actin bundles infused with myosin to exert contractile forces on the extracellular environment. This active tension is essential for cellular mechanosensation. Now, the role of actin crosslinkers in stabilizing and repairing the actin bundles is coming into clearer view.

  3. Characterization of hyaluronan cable structure and function in renal proximal tubular epithelial cells.

    PubMed

    Selbi, W; de la Motte, C A; Hascall, V C; Day, A J; Bowen, T; Phillips, A O

    2006-10-01

    Alteration in the glycosaminoglycan hyaluronan (HA) has been demonstrated in numerous renal diseases. We have demonstrated that renal proximal tubular epithelial cells (PTCs) surround themselves in vitro with HA in an organized pericellular matrix or 'coat', which is associated with cell migration, and also form pericellular HA cable-like structures which modulate PTC-mononuclear leukocytes interactions. The aim of this study was to characterize potential regulatory mechanism in the assembly of PTC-HA into pericellular cables. HA cables are generated by PTCs in the absence of serum. Immunohistochemical analysis demonstrates the incorporation of components of the inter-alpha-inhibitor (IalphaI) family of proteins and versican into HA cables. Addition of an antibody to IalphaI/PalphaI (pre-alpha-inhibitor) inhibits cable formation. In contrast, inhibition of tumor necrosis factor-alpha-stimulated gene 6 (TSG-6) has no effect on cable formation, suggesting that their generation is independent of the known heavy-chain transfer activity of TSG-6. Overexpression of HAS3 is associated with induction of HA cable formation, and also increased incorporation of HA into pericellular coats. Functionally, this resulted in enhanced HA-dependent monocyte binding and cell migration, respectively. Cell surface expression of CD44 and trypsin-released cell-associated HA were increased in HAS3-overexpressing cells. In addition, hyaluronidase (hyal1 and hyal2) and bikunin mRNA expression were increased, whereas PalphaI HC3 mRNA expression was unchanged in the transfected cells. The data demonstrate the importance of IalphaI/PalphaI in cable formation and suggest that expression of HAS3 may be critical for HA cable assembly.

  4. Direct interaction between two actin nucleators is required in Drosophila oogenesis

    PubMed Central

    Quinlan, Margot E.

    2013-01-01

    Controlled actin assembly is crucial to a wide variety of cellular processes, including polarity establishment during early development. The recently discovered actin mesh, a structure that traverses the Drosophila oocyte during mid-oogenesis, is essential for proper establishment of the major body axes. Genetic experiments indicate that at least two proteins, Spire (Spir) and Cappuccino (Capu), are required to build this mesh. The spire and cappuccino genetic loci were first identified as maternal effect genes in Drosophila. Mutation in either locus results in the same phenotypes, including absence of the mesh, linking them functionally. Both proteins nucleate actin filaments. Spir and Capu also interact directly with each other in vitro, suggesting a novel synergistic mode of regulating actin. In order to understand how and why proteins with similar biochemical activity would be required in the same biological pathway, genetic experiments were designed to test whether a direct interaction between Spir and Capu is required during oogenesis. Indeed, data in this study indicate that Spir and Capu must interact directly with one another and then separate to function properly. Furthermore, these actin regulators are controlled by a combination of mechanisms, including interaction with one another, functional inhibition and regulation of their protein levels. Finally, this work demonstrates for the first time in a multicellular organism that the ability of a formin to assemble actin filaments is required for a specific structure. PMID:24089467

  5. High-speed depolymerization at actin filament ends jointly catalysed by Twinfilin and Srv2/CAP.

    PubMed

    Johnston, Adam B; Collins, Agnieszka; Goode, Bruce L

    2015-11-01

    Purified actin filaments depolymerize slowly, and cytosolic conditions strongly favour actin assembly over disassembly, which has left our understanding of how actin filaments are rapidly turned over in vivo incomplete. One mechanism for driving filament disassembly is severing by factors such as Cofilin. However, even after severing, pointed-end depolymerization remains slow and unable to fully account for observed rates of actin filament turnover in vivo. Here we describe a mechanism by which Twinfilin and Cyclase-associated protein work in concert to accelerate depolymerization of actin filaments by 3-fold and 17-fold at their barbed and pointed ends, respectively. This mechanism occurs even under assembly conditions, allowing reconstitution and direct visualization of individual filaments undergoing tunable, accelerated treadmilling. Further, we use specific mutations to demonstrate that this activity is critical for Twinfilin function in vivo. These findings fill a major gap in our knowledge of cellular disassembly mechanisms, and suggest that depolymerization and severing may be deployed separately or together to control the dynamics and architecture of distinct actin networks.

  6. High Speed Depolymerization at Actin Filament Ends Jointly Catalyzed by Twinfilin and Srv2/CAP

    PubMed Central

    Johnston, Adam B.; Collins, Agnieszka; Goode, Bruce L.

    2015-01-01

    Purified actin filaments depolymerize slowly, and cytosolic conditions strongly favor actin assembly over disassembly, which has left our understanding of how actin filaments are rapidly turned over in vivo incomplete 1,2. One mechanism for driving filament disassembly is severing by factors such as Cofilin. However, even after severing, pointed end depolymerization remains slow and unable to fully account for observed rates of actin filament turnover in vivo. Here we describe a mechanism by which Twinfilin and Cyclase-associated protein work in concert to accelerate depolymerization of actin filaments by 3-fold and 17-fold at their barbed and pointed ends, respectively. This mechanism occurs even under assembly conditions, allowing reconstitution and direct visualization of individual filaments undergoing tunable, accelerated treadmilling. Further, we use specific mutations to demonstrate that this activity is critical for Twinfilin function in vivo. These findings fill a major gap in our knowledge of mechanisms, and suggest that depolymerization and severing may be deployed separately or together to control the dynamics and architecture of distinct actin networks. PMID:26458246

  7. Direct interaction between two actin nucleators is required in Drosophila oogenesis.

    PubMed

    Quinlan, Margot E

    2013-11-01

    Controlled actin assembly is crucial to a wide variety of cellular processes, including polarity establishment during early development. The recently discovered actin mesh, a structure that traverses the Drosophila oocyte during mid-oogenesis, is essential for proper establishment of the major body axes. Genetic experiments indicate that at least two proteins, Spire (Spir) and Cappuccino (Capu), are required to build this mesh. The spire and cappuccino genetic loci were first identified as maternal effect genes in Drosophila. Mutation in either locus results in the same phenotypes, including absence of the mesh, linking them functionally. Both proteins nucleate actin filaments. Spir and Capu also interact directly with each other in vitro, suggesting a novel synergistic mode of regulating actin. In order to understand how and why proteins with similar biochemical activity would be required in the same biological pathway, genetic experiments were designed to test whether a direct interaction between Spir and Capu is required during oogenesis. Indeed, data in this study indicate that Spir and Capu must interact directly with one another and then separate to function properly. Furthermore, these actin regulators are controlled by a combination of mechanisms, including interaction with one another, functional inhibition and regulation of their protein levels. Finally, this work demonstrates for the first time in a multicellular organism that the ability of a formin to assemble actin filaments is required for a specific structure.

  8. Neural Wiskott-Aldrich syndrome protein is implicated in the actin-based motility of Shigella flexneri.

    PubMed Central

    Suzuki, T; Miki, H; Takenawa, T; Sasakawa, C

    1998-01-01

    Shigella, the causative agent of bacillary dysentery, is capable of directing its own movement in the cytoplasm of infected epithelial cells. The bacterial surface protein VirG recruits host components mediating actin polymerization, which is thought to serve as the propulsive force. Here, we show that neural Wiskott-Aldrich syndrome protein (N-WASP), which is a critical target for filopodium formation downstream of Cdc42, is required for assembly of the actin tail generated by intracellular S.flexneri. N-WASP accumulates at the front of the actin tail and is capable of interacting with VirG in vitro and in vivo, a phenomenon that is not observed in intracellular Listeria monocytogenes. The verprolin-homology region in N-WASP was required for binding to the glycine-rich repeats domain of VirG, an essential domain for recruitment of F-actin on intracellular S.flexneri. Overexpression of a dominant-negative N-WASP mutant greatly inhibited formation of the actin tail by intracellular S.flexneri. Furthermore, depletion of N-WASP from Xenopus egg extracts shut off Shigella actin tail assembly, and this was restored upon addition of N-WASP protein, suggesting that N-WASP is a critical host factor for the assembly of the actin tail by intracellular Shigella. PMID:9582270

  9. Transmission shift control assembly

    SciTech Connect

    Dzioba, D.L.

    1989-04-18

    This patent describes a transmission shift control assembly mounted on a steering column having a longitudinal axis comprising: bracket means secured to the steering column; transmission shift cable means having a portion secured to the bracket means and a portion linearly movable relative to the secured portion; mounting means on the bracket cable drive arm means having an axis and being rotatably mounted on the rotary axis on the mounting means oblique to the longitudinal axis and including a cable connecting portion secured to the movable portion of the cable means and lever mounting means adjacent the mounting means; operator control means including lever means, pin means for pivotally mounting the lever means on the lever mounting means on an axis substantially perpendicular to the rotary axis and positioning arm means formed on the lever means and extending from the pin means; and detent gate means disposed on the bracket means in position to abut the positioning arm means for limiting the extent of pivotal movement of the lever means.

  10. Subversion of the actin cytoskeleton during viral infection

    PubMed Central

    Taylor, Matthew P.; Koyuncu, Orkide O.; Enquist, Lynn W.

    2011-01-01

    Viral infection converts the normal functions of a cell to optimize viral replication and virion production. One striking observation of this conversion is the reconfiguration and reorganization of cellular actin, affecting every stage of the viral life cycle, from entry through assembly to egress. The extent and degree of cytoskeletal reorganization varies among different viral infections, suggesting the evolution of myriad viral strategies. In this Review, we describe how the interaction of viral proteins with the cell modulates the structure and function of the actin cytoskeleton to initiate, sustain and spread infections. The molecular biology of such interactions continues to engage virologists in their quest to understand viral replication and informs cell biologists about the role of the cytoskeleton in the uninfected cell. PMID:21522191

  11. Profilin Interaction with Actin Filament Barbed End Controls Dynamic Instability, Capping, Branching, and Motility

    PubMed Central

    Pernier, Julien; Shekhar, Shashank; Jegou, Antoine; Guichard, Bérengère; Carlier, Marie-France

    2016-01-01

    Summary Cell motility and actin homeostasis depend on the control of polarized growth of actin filaments. Profilin, an abundant regulator of actin dynamics, supports filament assembly at barbed ends by binding G-actin. Here, we demonstrate how, by binding and destabilizing filament barbed ends at physiological concentrations, profilin also controls motility, cell migration, and actin homeostasis. Profilin enhances filament length fluctuations. Profilin competes with Capping Protein at barbed ends, which generates a lower amount of profilin-actin than expected if barbed ends were tightly capped. Profilin competes with barbed end polymerases, such as formins and VopF, and inhibits filament branching by WASP-Arp2/3 complex by competition for filament barbed ends, accounting for its as-yet-unknown effects on motility and metastatic cell migration observed in this concentration range. In conclusion, profilin is a major coordinator of polarized growth of actin filaments, controlled by competition between barbed end cappers, trackers, destabilizers, and filament branching machineries. PMID:26812019

  12. KDM3A coordinates actin dynamics with intraflagellar transport to regulate cilia stability.

    PubMed

    Yeyati, Patricia L; Schiller, Rachel; Mali, Girish; Kasioulis, Ioannis; Kawamura, Akane; Adams, Ian R; Playfoot, Christopher; Gilbert, Nick; van Heyningen, Veronica; Wills, Jimi; von Kriegsheim, Alex; Finch, Andrew; Sakai, Juro; Schofield, Christopher J; Jackson, Ian J; Mill, Pleasantine

    2017-02-28

    Cilia assembly and disassembly are coupled to actin dynamics, ensuring a coherent cellular response during environmental change. How these processes are integrated remains undefined. The histone lysine demethylase KDM3A plays important roles in organismal homeostasis. Loss-of-function mouse models of Kdm3a phenocopy features associated with human ciliopathies, whereas human somatic mutations correlate with poor cancer prognosis. We demonstrate that absence of KDM3A facilitates ciliogenesis, but these resulting cilia have an abnormally wide range of axonemal lengths, delaying disassembly and accumulating intraflagellar transport (IFT) proteins. KDM3A plays a dual role by regulating actin gene expression and binding to the actin cytoskeleton, creating a responsive "actin gate" that involves ARP2/3 activity and IFT. Promoting actin filament formation rescues KDM3A mutant ciliary defects. Conversely, the simultaneous depolymerization of actin networks and IFT overexpression mimics the abnormal ciliary traits of KDM3A mutants. KDM3A is thus a negative regulator of ciliogenesis required for the controlled recruitment of IFT proteins into cilia through the modulation of actin dynamics.

  13. A glycolytic metabolon in Saccharomyces cerevisiae is stabilized by F-actin.

    PubMed

    Araiza-Olivera, Daniela; Chiquete-Felix, Natalia; Rosas-Lemus, Mónica; Sampedro, José G; Peña, Antonio; Mujica, Adela; Uribe-Carvajal, Salvador

    2013-08-01

    In the Saccharomyces cerevisiae glycolytic pathway, 11 enzymes catalyze the stepwise conversion of glucose to two molecules of ethanol plus two CO₂ molecules. In the highly crowded cytoplasm, this pathway would be very inefficient if it were dependent on substrate/enzyme diffusion. Therefore, the existence of a multi-enzymatic glycolytic complex has been suggested. This complex probably uses the cytoskeleton to stabilize the interaction of the various enzymes. Here, the role of filamentous actin (F-actin) in stabilization of a putative glycolytic metabolon is reported. Experiments were performed in isolated enzyme/actin mixtures, cytoplasmic extracts and permeabilized yeast cells. Polymerization of actin was promoted using phalloidin or inhibited using cytochalasin D or latrunculin. The polymeric filamentous F-actin, but not the monomeric globular G-actin, stabilized both the interaction of isolated glycolytic pathway enzyme mixtures and the whole fermentation pathway, leading to higher fermentation activity. The associated complexes were resistant against inhibition as a result of viscosity (promoted by the disaccharide trehalose) or inactivation (using specific enzyme antibodies). In S. cerevisiae, a glycolytic metabolon appear to assemble in association with F-actin. In this complex, fermentation activity is enhanced and enzymes are partially protected against inhibition by trehalose or by antibodies.

  14. KDM3A coordinates actin dynamics with intraflagellar transport to regulate cilia stability

    PubMed Central

    Schiller, Rachel; Kawamura, Akane; Gilbert, Nick; Wills, Jimi; von Kriegsheim, Alex

    2017-01-01

    Cilia assembly and disassembly are coupled to actin dynamics, ensuring a coherent cellular response during environmental change. How these processes are integrated remains undefined. The histone lysine demethylase KDM3A plays important roles in organismal homeostasis. Loss-of-function mouse models of Kdm3a phenocopy features associated with human ciliopathies, whereas human somatic mutations correlate with poor cancer prognosis. We demonstrate that absence of KDM3A facilitates ciliogenesis, but these resulting cilia have an abnormally wide range of axonemal lengths, delaying disassembly and accumulating intraflagellar transport (IFT) proteins. KDM3A plays a dual role by regulating actin gene expression and binding to the actin cytoskeleton, creating a responsive “actin gate” that involves ARP2/3 activity and IFT. Promoting actin filament formation rescues KDM3A mutant ciliary defects. Conversely, the simultaneous depolymerization of actin networks and IFT overexpression mimics the abnormal ciliary traits of KDM3A mutants. KDM3A is thus a negative regulator of ciliogenesis required for the controlled recruitment of IFT proteins into cilia through the modulation of actin dynamics. PMID:28246120

  15. Gelsolin, a protein that caps the barbed ends and severs actin filaments, enhances the actin-based motility of Listeria monocytogenes in host cells.

    PubMed

    Laine, R O; Phaneuf, K L; Cunningham, C C; Kwiatkowski, D; Azuma, T; Southwick, F S

    1998-08-01

    The actin-based motility of Listeria monocytogenes requires the addition of actin monomers to the barbed or plus ends of actin filaments. Immunofluorescence micrographs have demonstrated that gelsolin, a protein that both caps barbed ends and severs actin filaments, is concentrated directly behind motile bacteria at the junction between the actin filament rocket tail and the bacterium. In contrast, CapG, a protein that strictly caps actin filaments, fails to localize near intracellular Listeria. To explore the effect of increasing concentrations of gelsolin on bacterial motility, NIH 3T3 fibroblasts stably transfected with gelsolin cDNA were infected with Listeria. The C5 cell line containing 2.25 times control levels of gelsolin supported significantly higher velocities of bacterial movement than did control fibroblasts (mean +/- standard error of the mean, 0.09 +/- 0.003 micro(m)/s [n = 176] versus 0.05 +/- 0.003 micro(m)/s [n = 65]). The rate of disassembly of the Listeria-induced actin filament rocket tail was found to be independent of gelsolin content. Therefore, if increases in gelsolin content result in increases in Listeria-induced rocket tail assembly rates, a positive correlation between gelsolin content and tail length would be expected. BODIPY-phalloidin staining of four different stably transfected NIH 3T3 fibroblast cell lines confirmed this expectation (r = 0.92). Rocket tails were significantly longer in cells with a high gelsolin content. Microinjection of gelsolin 1/2 (consisting of the amino-terminal half of native gelsolin) also increased bacterial velocity by more than 2.2 times. Microinjection of CapG had no effect on bacterial movement. Cultured skin fibroblasts derived from gelsolin-null mice were capable of supporting intracellular Listeria motility at velocities comparable to those supported by wild-type skin fibroblasts. These experiments demonstrated that the surface of Listeria contains a polymerization zone that can block the barbed

  16. Single-filament kinetic studies provide novel insights into regulation of actin-based motility

    PubMed Central

    Shekhar, Shashank; Carlier, Marie-France

    2016-01-01

    Polarized assembly of actin filaments forms the basis of actin-based motility and is regulated both spatially and temporally. Cells use a variety of mechanisms by which intrinsically slower processes are accelerated, and faster ones decelerated, to match rates observed in vivo. Here we discuss how kinetic studies of individual reactions and cycles that drive actin remodeling have provided a mechanistic and quantitative understanding of such processes. We specifically consider key barbed-end regulators such as capping protein and formins as illustrative examples. We compare and contrast different kinetic approaches, such as the traditional pyrene-polymerization bulk assays, as well as more recently developed single-filament and single-molecule imaging approaches. Recent development of novel biophysical methods for sensing and applying forces will in future allow us to address the very important relationship between mechanical stimulus and kinetics of actin-based motility. PMID:26715420

  17. Coronin 3 involvement in F-actin-dependent processes at the cell cortex

    SciTech Connect

    Rosentreter, Andre; Hofmann, Andreas; Xavier, Charles-Peter; Stumpf, Maria; Noegel, Angelika A.; Clemen, Christoph S. . E-mail: christoph.clemen@uni-koeln.de

    2007-03-10

    The actin interaction of coronin 3 has been mainly documented by in vitro experiments. Here, we discuss coronin 3 properties in the light of new structural information and focus on assays that reflect in vivo roles of coronin 3 and its impact on F-actin-associated functions. Using GFP-tagged coronin 3 fusion proteins and RNAi silencing we show that coronin 3 has roles in wound healing, protrusion formation, cell proliferation, cytokinesis, endocytosis, axonal growth, and secretion. During formation of cell protrusions actin accumulation precedes the focal enrichment of coronin 3 suggesting a role for coronin 3 in events that follow the initial F-actin assembly. Moreover, we show that coronin 3 similar to other coronins interacts with the Arp2/3-complex and cofilin indicating that this family in general is involved in regulating Arp2/3-mediated events.

  18. Actin Polymerization Driven Mitochondrial Transport in Mating S. cerevisiae by Fourier Imaging Correlation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Senning, Eric; Marcus, Andrew

    2010-03-01

    The dynamic microenvironment of cells depends on macromolecular architecture, equilibrium fluctuations, and non-equilibrium forces generated by cytoskeletal proteins. We studied the influence of these factors on the motions of mitochondria in mating S. cerevisiae using Fourier imaging correlation spectroscopy (FICS). Our measurements provide detailed, length scale dependent information about the dynamic behavior of mitochondria. We investigate the influence of the actin cytoskeleton on mitochondrial motion, and make comparisons between conditions in which actin network assembly and disassembly is varied, either by using disruptive pharmacological agents, or mutations that alter the rates of actin polymerization. We find that non-equilibrium forces associated with actin polymerization lead to a 1.5-fold enhancement of the long-time mitochondrial diffusion coefficient, and a transient sub-diffusive temporal scaling of the mean-square displacement. Our results lend support to an existing model in which these forces are directly coupled to mitochondrial membrane surfaces.

  19. Membrane Supply and Demand Regulates F-Actin in a Cell Surface Reservoir.

    PubMed

    Figard, Lauren; Wang, Mengyu; Zheng, Liuliu; Golding, Ido; Sokac, Anna Marie

    2016-05-09

    Cells store membrane in surface reservoirs of pits and protrusions. These membrane reservoirs facilitate cell shape change and buffer mechanical stress, but we do not know how reservoir dynamics are regulated. During cellularization, the first cytokinesis in Drosophila embryos, a reservoir of microvilli unfolds to fuel cleavage furrow ingression. We find that regulated exocytosis adds membrane to the reservoir before and during unfolding. Dynamic F-actin deforms exocytosed membrane into microvilli. Single microvilli extend and retract in ∼20 s, while the overall reservoir is depleted in sync with furrow ingression over 60-70 min. Using pharmacological and genetic perturbations, we show that exocytosis promotes microvillar F-actin assembly, while furrow ingression controls microvillar F-actin disassembly. Thus, reservoir F-actin and, consequently, reservoir dynamics are regulated by membrane supply from exocytosis and membrane demand from furrow ingression.

  20. Cardiac myosin-binding protein C decorates F-actin: Implications for cardiac function

    PubMed Central

    Whitten, Andrew E.; Jeffries, Cy M.; Harris, Samantha P.; Trewhella, Jill

    2008-01-01

    Cardiac myosin-binding protein C (cMyBP-C) is an accessory protein of striated muscle sarcomeres that is vital for maintaining regular heart function. Its 4 N-terminal regulatory domains, C0-C1-m-C2 (C0C2), influence actin and myosin interactions, the basic contractile proteins of muscle. Using neutron contrast variation data, we have determined that C0C2 forms a repeating assembly with filamentous actin, where the C0 and C1 domains of C0C2 attach near the DNase I-binding loop and subdomain 1 of adjacent actin monomers. Direct interactions between the N terminus of cMyBP-C and actin thereby provide a mechanism to modulate the contractile cycle by affecting the regulatory state of the thin filament and its ability to interact with myosin. PMID:19011110

  1. Nuclear envelope rupture is induced by actin-based nucleus confinement.

    PubMed

    Hatch, Emily M; Hetzer, Martin W

    2016-10-10

    Repeated rounds of nuclear envelope (NE) rupture and repair have been observed in laminopathy and cancer cells and result in intermittent loss of nucleus compartmentalization. Currently, the causes of NE rupture are unclear. Here, we show that NE rupture in cancer cells relies on the assembly of contractile actin bundles that interact with the nucleus via the linker of nucleoskeleton and cytoskeleton (LINC) complex. We found that the loss of actin bundles or the LINC complex did not rescue nuclear lamina defects, a previously identified determinant of nuclear membrane stability, but did decrease the number and size of chromatin hernias. Finally, NE rupture inhibition could be rescued in cells treated with actin-depolymerizing drugs by mechanically constraining nucleus height. These data suggest a model of NE rupture where weak membrane areas, caused by defects in lamina organization, rupture because of an increase in intranuclear pressure from actin-based nucleus confinement.

  2. Flat conductor cable design, manufacture, and installation

    NASA Technical Reports Server (NTRS)

    Angele, W.; Hankins, J. D.

    1973-01-01

    Pertinent information for hardware selection, design, manufacture, and quality control necessary for flat conductor cable interconnecting harness application is presented. Comparisons are made between round wire cable and flat conductor cable. The flat conductor cable interconnecting harness systems show major cost, weight, and space savings, plus increased system performance and reliability. The design application section includes electrical characteristics, harness design and development, and a full treatise on EMC considerations. Manufacturing and quality control sections pertain primarily to the developed conductor-contact connector system and special flat conductor cable to round wire cable transitions.

  3. Mechanism of Actin-Based Motility

    NASA Astrophysics Data System (ADS)

    Pantaloni, Dominique; Le Clainche, Christophe; Carlier, Marie-France

    2001-05-01

    Spatially controlled polymerization of actin is at the origin of cell motility and is responsible for the formation of cellular protrusions like lamellipodia. The pathogens Listeria monocytogenes and Shigella flexneri, which undergo actin-based propulsion, are acknowledged models of the leading edge of lamellipodia. Actin-based motility of the bacteria or of functionalized microspheres can be reconstituted in vitro from only five pure proteins. Movement results from the regulated site-directed treadmilling of actin filaments, consistent with observations of actin dynamics in living motile cells and with the biochemical properties of the components of the synthetic motility medium.

  4. A single charge in the actin binding domain of fascin can independently tune the linear and non-linear response of an actin bundle network.

    PubMed

    Maier, M; Müller, K W; Heussinger, C; Köhler, S; Wall, W A; Bausch, A R; Lieleg, O

    2015-05-01

    Actin binding proteins (ABPs) not only set the structure of actin filament assemblies but also mediate the frequency-dependent viscoelastic moduli of cross-linked and bundled actin networks. Point mutations in the actin binding domain of those ABPs can tune the association and dissociation dynamics of the actin/ABP bond and thus modulate the network mechanics both in the linear and non-linear response regime. We here demonstrate how the exchange of a single charged amino acid in the actin binding domain of the ABP fascin triggers such a modulation of the network rheology. Whereas the overall structure of the bundle networks is conserved, the transition point from strain-hardening to strain-weakening sensitively depends on the cross-linker off-rate and the applied shear rate. Our experimental results are consistent both with numerical simulations of a cross-linked bundle network and a theoretical description of the bundle network mechanics which is based on non-affine bending deformations and force-dependent cross-link dynamics.

  5. Effects of solution crowding on actin polymerization reveal the energetic basis for nucleotide-dependent filament stability

    PubMed Central

    Frederick, Kendra B.; Sept, David; De La Cruz, Enrique M.

    2008-01-01

    Actin polymerization is a fundamental cellular process involved in cell structure maintenance, force generation, and motility. Phosphate release from filament subunits following ATP hydrolysis destabilizes the filament lattice and increases the critical concentration (Cc) for assembly. The structural differences between ATP- and ADP-actin are still debated, as well as the energetic factors that underlie nucleotide-dependent filament stability, particularly under crowded intracellular conditions. Here, we investigate the effect of crowding agents on ATP- and ADP-actin polymerization, and find that ATP-actin polymerization is largely unaffected by solution crowding, while crowding agents lower the Cc of ADP-actin in a concentration-dependent manner. The stabilities of ATP- and ADP-actin filaments are comparable in the presence of physiological amounts (~30% w/v) and types (sorbitol) of low molecular weight crowding agents. Crowding agents act to stabilize ADP-F-actin by slowing subunit dissociation. These observations suggest that nucleotide hydrolysis and phosphate release per se do not introduce intrinsic differences in the in vivo filament stability. Rather, the preferential disassembly of ADP-actin filaments in cells is driven through interactions with regulatory proteins. Interpretation of the experimental data according to osmotic stress theory implicates water as an allosteric regulator of actin activity and hydration as the molecular basis for nucleotide-dependent filament stability. PMID:18374941

  6. FEM Analysis of Nb-Sn Rutherford-type Cables

    SciTech Connect

    Barzi, Emanuela; Gallo, Giuseppe; Neri, Paolo; /Fermilab

    2011-01-01

    An important part of superconducting accelerator magnet work is the conductor. To produce magnetic fields larger than 10 T, brittle conductors are typically used. For instance, for Nb{sub 3}Sn the original round wire, in the form of a composite of Copper, Niobium and Tin, is assembled into a so-called Rutherford-type cable, which is used to wind the magnet. The magnet is then subjected to a high temperature heat treatment to produce the chemical reactions that make the material superconducting. At this stage the superconductor is brittle and its superconducting properties sensitive to strain. This work is based on the development of a 2D finite element model, which simulates the mechanical behavior of Rutherford-type cable before heat treatment. The model was applied to a number of different cable architectures. To validate a critical criterion adopted into the single Nb-Sn wire analysis, the results of the model were compared with those measured experimentally on cable cross sections.

  7. [Alterations in actin cytoskeleton and rate of reparation of human endothelium (the wound-healing model) under the condition of clinostatting].

    PubMed

    Romanov, Iu A; Kabaeva, N V; Buravkova, L B

    2001-01-01

    Effects of long-term simulation of hypogravity on actin cytoskeleton and cell migration were investigated in cultured human endothelium cells (EC). In control, F-actin resided predominantly on the periphery of cell forming an array of parallel bundles with "dense bodies" along the edge. A small number of actin cable fibers was found in the center. Already after 1-2 hrs of clinostatting at 5 RPM the cell cytoskeleton showed actin filament thinning and displacement toward the cell edges. In subsequent 6-18 hrs, almost all actin fibers had left the center part of EC and had ranged themselves in a continuous F-actin line in the intercellular contact area. In most cases, these changes resulted in the so-called "ruff-edge". Since both the disappearance of cable fibers and formation of the "ruff-edge" add to the cell migration activity, this parameter was studied with the would-healing model. According to our data, 24-48 hrs of exposure to hypogravity stimulates cell migration and expedites 2-3 times reparation of mechanically damaged monolayer. The results suggest that effects of hypogravity on cultured human EC are likely to be consequent to alterations in the activity of protein kinase C and/or adenylate cyclase involving many members of the cellular metabolism.

  8. Nuclear Actin in Development and Transcriptional Reprogramming.

    PubMed

    Misu, Shinji; Takebayashi, Marina; Miyamoto, Kei

    2017-01-01

    Actin is a highly abundant protein in eukaryotic cells and dynamically changes its polymerized states with the help of actin-binding proteins. Its critical function as a constituent of cytoskeleton has been well-documented. Growing evidence demonstrates that actin is also present in nuclei, referred to as nuclear actin, and is involved in a number of nuclear processes, including transcriptional regulation and chromatin remodeling. The contribution of nuclear actin to transcriptional regulation can be explained by its direct interaction with transcription machineries and chromatin remodeling factors and by controlling the activities of transcription factors. In both cases, polymerized states of nuclear actin affect the transcriptional outcome. Nuclear actin also plays an important role in activating strongly silenced genes in somatic cells for transcriptional reprogramming. When these nuclear functions of actin are considered, it is plausible to speculate that nuclear actin is also implicated in embryonic development, in which numerous genes need to be activated in a well-coordinated manner. In this review, we especially focus on nuclear actin's roles in transcriptional activation, reprogramming and development, including stem cell differentiation and we discuss how nuclear actin can be an important player in development and cell differentiation.

  9. Regulation of structure and function of sarcomeric actin filaments in striated muscle of the nematode Caenorhabditis elegans

    PubMed Central

    Ono, Shoichiro

    2014-01-01

    The nematode Caenorhabditis elegans has been used as a valuable system to study structure and function of striated muscle. The body wall muscle of C. elegans is obliquely striated muscle with highly organized sarcomeric assembly of actin, myosin, and other accessary proteins. Genetic and molecular biological studies in C. elegans have identified a number of genes encoding structural and regulatory components for the muscle contractile apparatuses, and many of them have counterparts in mammalian cardiac and skeletal muscles or striated muscles in other invertebrates. Applicability of genetics, cell biology, and biochemistry has made C. elegans an excellent system to study mechanisms of muscle contractility and assembly and maintenance of myofibrils. This review focuses on the regulatory mechanisms of structure and function of actin filaments in the C. elegans body wall muscle. Sarcomeric actin filaments in C. elegans muscle are associated with the troponin-tropomyosin system that regulates the actin-myosin interaction. Proteins that bind to the side and ends of actin filaments support ordered assembly of thin filaments. Furthermore, regulators of actin dynamics play important roles in initial assembly, growth, and maintenance of sarcomeres. The knowledge acquired in C. elegans can serve as bases to understand the basic mechanisms of muscle structure and function. PMID:25125169

  10. Actin Dynamics: From Nanoscale to Microscale

    PubMed Central

    Carlsson, Anders E.

    2010-01-01

    The dynamic nature of actin in cells manifests itself in many ways: Polymerization near the cell edge is balanced by depolymerization in the interior, externally induced actin polymerization is followed by depolymerization, and spontaneous oscillations of the cell periphery are frequently seen. I discuss how mathematical modeling relates quantitative measures of actin dynamics to the rates of underlying molecular level processes. The rate of actin incorporation at the leading edge of a moving cell is roughly consistent with existing theories, and the factors determining the characteristic time of actin polymerization are fairly well understood. However, our understanding of actin disassembly is limited, in particular the interplay between severing and depolymerization and the role of specific combinations of proteins in implementing disassembly events. The origins of cell-edge oscillations, and their possible relation to actin waves, are a fruitful area of future research. PMID:20462375

  11. Retraction statement: ‘Formin‐like2 regulates Rho/ROCK pathway to promote actin assembly and cell invasion of colorectal cancer’ by Yuanfeng Zeng, Huijun Xie, Yudan Qiao, Jianmei Wang, Xiling Zhu, Guoyang He, Yuling Li, Xiaoli Ren, Feifei Wang, Li Liang and Yanqing Ding

    PubMed Central

    2016-01-01

    The above article in Cancer Science (doi: 10.1111/cas.12768), published online on 26 October 2015 in Wiley Online Library (http://wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief, Yusuke Nakamura, and Wiley Publishing Asia Pty Ltd. The retraction has been agreed as Panels +C3 and +Y27632 of SW480 Mock shown in Figure 2a appear to have been taken from the same image, Panels + C3 and +Y27632 of HT29 FMNL2 shown in Figure 2a appear to have been taken from the same image, Panels shFMNL2‐1 and shmDial1‐1 in Figure 3a appear to have been taken from the same image, shFMNL2‐2 and shmDial1‐2 in Figure 3a appear to have been taken from the same image, Panels of shFMNL2‐1 + shmDial1‐1 and shFMNL2‐1 + shmDial1‐2 of +LPA appear to have been taken from the same image, gel bands of FLAG in Figure 4e appear to have been have been manipulated by erasing gel bands. Reference ZengY , XieH , QiaoY , WangJ , ZhuX , HeG , LiY , RenX , WangF , LiangL , DingY . Formin‐like2 regulates Rho/ROCK pathway to promote actin assembly and cell invasion of colorectal cancer. Cancer Sci 2015; 106: 1385–93. doi: 10.1111/cas.12768 26258642 PMID:27420476

  12. Retraction statement: 'Formin-like2 regulates Rho/ROCK pathway to promote actin assembly and cell invasion of colorectal cancer' by Yuanfeng Zeng, Huijun Xie, Yudan Qiao, Jianmei Wang, Xiling Zhu, Guoyang He, Yuling Li, Xiaoli Ren, Feifei Wang, Li Liang and Yanqing Ding.

    PubMed

    2016-07-01

    The above article in Cancer Science (doi: 10.1111/cas.12768), published online on 26 October 2015 in Wiley Online Library (http://wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief, Yusuke Nakamura, and Wiley Publishing Asia Pty Ltd. The retraction has been agreed as Panels +C3 and +Y27632 of SW480 Mock shown in Figure 2a appear to have been taken from the same image, Panels + C3 and +Y27632 of HT29 FMNL2 shown in Figure 2a appear to have been taken from the same image, Panels shFMNL2-1 and shmDial1-1 in Figure 3a appear to have been taken from the same image, shFMNL2-2 and shmDial1-2 in Figure 3a appear to have been taken from the same image, Panels of shFMNL2-1 + shmDial1-1 and shFMNL2-1 + shmDial1-2 of +LPA appear to have been taken from the same image, gel bands of FLAG in Figure 4e appear to have been have been manipulated by erasing gel bands. Reference Zeng Y, Xie H, Qiao Y, Wang J, Zhu X, He G, Li Y, Ren X, Wang F, Liang L, Ding Y. Formin-like2 regulates Rho/ROCK pathway to promote actin assembly and cell invasion of colorectal cancer. Cancer Sci 2015; 106: 1385-93. doi: 10.1111/cas.12768.

  13. Stability and 3-D spatial dynamics analysis of a three cable crane

    NASA Technical Reports Server (NTRS)

    Yang, Li-Farn; Mikulas, Martin M., Jr.; Chiou, Jin-Chern

    1992-01-01

    A 3-cable crane mechanism has been designed for incorporation into a highly loaded Lunar crane for planetary construction. This 3-cable crane must maintain a positive stability margin in all phases of the loading/unloading, assembly, or installation operations. A 2D kinematic curvature theory is applied to: (1) derive a general stability criterion to prevent the 3-cable crane from instability; and (2) determine a simple equation of natural frequency for two planar models of 3-cable crane. Investigation of the 2D vibrational characteristics of the planar models provides valuable insight toward understanding of 3D dynamic behavior of the 3-cable crane. Also, precision in natural frequency from this simple kinematic equation due to the exclusion of the radius-of-gyration of a suspended article is discussed. Multibody dynamics of the 3D 3-cable crane is presented and simulated to study the resulting vibrational characteristics under external disturbances and to verify the feasibility of the stability criterion for the 3-cable crane.

  14. Chlamydia trachomatis Tarp harbors distinct G and F actin binding domains that bundle actin filaments.

    PubMed

    Jiwani, Shahanawaz; Alvarado, Stephenie; Ohr, Ryan J; Romero, Adriana; Nguyen, Brenda; Jewett, Travis J

    2013-02-01

    All species of Chlamydia undergo a unique developmental cycle that transitions between extracellular and intracellular environments and requires the capacity to invade new cells for dissemination. A chlamydial protein called Tarp has been shown to nucleate actin in vitro and is implicated in bacterial entry into human cells. Colocalization studies of ectopically expressed enhanced green fluorescent protein (EGFP)-Tarp indicate that actin filament recruitment is restricted to the C-terminal half of the effector protein. Actin filaments are presumably associated with Tarp via an actin binding alpha helix that is also required for actin nucleation in vitro, but this has not been investigated. Tarp orthologs from C. pneumoniae, C. muridarum, and C. caviae harbor between 1 and 4 actin binding domains located in the C-terminal half of the protein, but C. trachomatis serovar L2 has only one characterized domain. In this work, we examined the effects of domain-specific mutations on actin filament colocalization with EGFP-Tarp. We now demonstrate that actin filament colocalization with Tarp is dependent on two novel F-actin binding domains that endow the Tarp effector with actin-bundling activity. Furthermore, Tarp-mediated actin bundling did not require actin nucleation, as the ability to bundle actin filaments was observed in mutant Tarp proteins deficient in actin nucleation. These data shed molecular insight on the complex cytoskeletal rearrangements required for C. trachomatis entry into host cells.

  15. Umbilical cable recovery load analysis

    NASA Astrophysics Data System (ADS)

    Yan, Shu-wang; Jia, Zhao-lin; Feng, Xiao-wei; Li, Shi-tao

    2013-06-01

    Umbilical cable is a kind of integrated subsea cable widely used in the exploration and exploitation of oil and gas field. The severe ocean environment makes great challenges to umbilical maintenance and repair work. Damaged umbilical is usually recovered for the regular operation of the offshore production system. Analysis on cables in essence is a two-point boundary problem. The tension load at the mudline must be known first, and then the recovery load and recovery angle on the vessel can be solved by use of catenary equation. The recovery analysis also involves umbilical-soil interaction and becomes more complicated. Calculation methods for recovery load of the exposed and buried umbilical are established and the relationship between the position of touch down point and the recovery load as well as the recovery angle and recovery load are analyzed. The analysis results provide a theoretical reference for offshore on-deck operation.

  16. Cable Television: From Here to Where?

    ERIC Educational Resources Information Center

    Canadian Cable Television Association, Ottawa (Ontario).

    A brief description is presented of the present uses, regulatory structure, and future potentials of cable television for Canada. Some 30% of Canada is already wired for cable, as opposed to 9% in the United States. (RH)

  17. Ames Lab 101: Reinventing the Power Cable

    SciTech Connect

    Russell, Alan

    2013-09-27

    Ames Laboratory researchers are working to develop new electrical power cables that are stronger and lighter than the cables currently used in the nation's power grid. Nano Tube animation by Iain Goodyear

  18. 30 CFR 18.45 - Cable reels.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., hydraulically, or electrically driven reel upon which to wind the portable cable. (b) The enclosure for moving... of travel of a machine when receiving power through a portable (trailing) cable shall not exceed...

  19. 30 CFR 18.45 - Cable reels.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., hydraulically, or electrically driven reel upon which to wind the portable cable. (b) The enclosure for moving... of travel of a machine when receiving power through a portable (trailing) cable shall not exceed...

  20. Folding tools for flat conductor cable harnesses

    NASA Technical Reports Server (NTRS)

    Loggins, R.

    1971-01-01

    Vise grip pliers have detachable metal gripping plates which are changed to accommodate cables from 1 to 3 in. wide and to form any desired fold angle. A second tool squeezes cable along crease to complete the fold.

  1. New sensitive seismic cable with imbedded geophones

    NASA Astrophysics Data System (ADS)

    Pakhomov, Alex; Pisano, Dan; Goldburt, Tim

    2005-10-01

    Seismic detection systems for homeland security applications are an important additional layer to perimeter and border protection and other security systems. General Sensing Systems has been developing low mass, low cost, highly sensitive geophones. These geophones are being incorporated within a seismic cable. This article reports on the concept of a seismic sensitive cable and seismic sensitive ribbon design. Unlike existing seismic cables with sensitivity distributed along their lengths, the GSS new cable and ribbon possesses high sensitivity distributed in several points along the cable/ribbon with spacing of about 8-12 to 100 meters between geophones. This cable/ribbon is highly suitable for design and installation in extended perimeter protection systems. It allows the use of a mechanical cable layer for high speed installation. We show that any installation mistakes in using the GSS seismic sensitive cable/ribbon have low impact on output seismic signal value and detection range of security systems.

  2. Ames Lab 101: Reinventing the Power Cable

    ScienceCinema

    Russell, Alan

    2016-07-12

    Ames Laboratory researchers are working to develop new electrical power cables that are stronger and lighter than the cables currently used in the nation's power grid. Nano Tube animation by Iain Goodyear

  3. The yeast dynamin-like protein Vps1:vps1 mutations perturb the internalization and the motility of endocytic vesicles and endosomes via disorganization of the actin cytoskeleton.

    PubMed

    Nannapaneni, Srikant; Wang, Daobing; Jain, Sandhya; Schroeder, Blake; Highfill, Chad; Reustle, Lindsay; Pittsley, Delilah; Maysent, Adam; Moulder, Shawn; McDowell, Ryan; Kim, Kyoungtae

    2010-07-01

    Mammalian dynamin is responsible for scission of endocytic vesicles from the plasma membrane. A previous study showed that Vps1, a yeast dynamin-like protein, plays an important role in pheromone receptor internalization (Yu and Cai, 2004; J. Cell Sci. 117, 3839-3853). However, the details of how Vps1 acts in various phases of endocytosis including early internalization of the endocytic vesicle are poorly understood. To investigate the potential roles of Vps1 in both endocytic vesicle formation/maturation on the plasma membrane and endocytic vesicle internalization, time-lapse fluorescent images of GFP-tagged endocytic markers in live cells were analyzed using a particle tracking software. The loss of Vps1 leads to a robust increase in the lifespan of newly forming cortical endocytic vesicles carrying Las17-GFP, Ede1-GFP, Sla1-GFP, and Abp1-GFP, indicating that Vps1 is required for the proper assembly and maturation of endocytic vesicles. Particle track analysis revealed that Abp1-GFP vesicles in vps1 null cells moved a relatively short distance away from the cell membrane due to their non-directional movement. Furthermore, we found that the GTPase and the GED domains of Vps1 are required for the proper endocytic function of Vps1. Our tracking analysis data also revealed that the post-internalized vesicle motility en route to the vacuole was decreased significantly, perhaps due to severe disruption of the actin cables in Vps1 mutant cells.

  4. Mechanism synthesis and 2-D control designs of an active three cable crane

    NASA Technical Reports Server (NTRS)

    Yang, Li-Farn; Mikulas, Martin M., Jr.

    1992-01-01

    A Lunar Crane with a suspension system based on a three cable mechanism is investigated to provide a stable end-effector for hoisting, positioning, and assembling large components during construction and servicing of a Lunar Base. The three cable suspension mechanism consists of a structural framework of three cables pointing to a common point that closely coincides with the suspended payload's center of gravity. The vibrational characteristics of this three cable suspension system are investigated by comparing a simple 2-D symmetric suspension model and a swinging pendulum in terms of their analytical natural frequency equations. A study is also made of actively controlling the dynamics of the crane using two different actuator concepts. Also, Lyapunov-based control algorithms are developed to determine two regulator-type control laws performing the system vibrational suppression for both system dynamics. Simulations including initial-valued dynamic responses as well as control performances for two different system dynamics are also presented.

  5. Interaction of rabbit skeletal muscle troponin T and F-actin at physiological ionic strength

    SciTech Connect

    Heeley, D.H.; Smillie, L.B. )

    1988-10-18

    Troponin T has been shown to interact significantly with F-actin at 150 mM KC1 by using an F-actin pelleting assay and {sup 125}I-labeled proteins. While troponin T fragment T1 (residues 1-158) fails to pellet with F-actin, fragment T2 (residues 159-259) mimics the binding properties of the intact molecule. The weak competition of T2 binding to F-actin, shown by subfragments of T2, indicates that the interaction site(s) encompass(es) an extensive segment of troponin T. The extent of pelleting of troponin T (or T2) with F-actin is only marginally altered in the binary complex troponin IT (or T2), indicating that the direct interactions either of troponin T (or T2) or of troponin I, or both, with F-actin are weakened when these components are incorporated into a binary complex. The binding of troponin T (or T2) is moderately ({minus}Ca{sup 2+}) or more extensively reduced (+Ca{sup 2+}) in the presence of troponin C. The pelleting of Tn-T seen in the presence of Tn-C ({minus}Ca{sup 2+}) and Tn-I was further reduced when either Tn-I or Tn-C ({minus}Ca{sup 2+}) was added, respectively, to form a fully reconstituted Tn complex. As noted by others, whole troponin shows little sensitivity to Ca{sup 2+} in its binding to F-actin ({minus}tropomyosin). These and other observations, taken together with the restoration of troponin IC ({plus minus}Ca{sup 2+}) binding to F-actin by troponin T, implicate a role for the interaction of troponin T and F-actin in the thin filament assembly.

  6. Yeast Rsp5 ubiquitin ligase affects the actin cytoskeleton in vivo and in vitro.

    PubMed

    Kaminska, Joanna; Spiess, Matthias; Stawiecka-Mirota, Marta; Monkaityte, Rasa; Haguenauer-Tsapis, Rosine; Urban-Grimal, Daniele; Winsor, Barbara; Zoladek, Teresa

    2011-12-01

    Yeast Rsp5 ubiquitin ligase is involved in several cellular processes, including endocytosis. Actin patches are sites of endocytosis, a process involving actin assembly and disassembly. Here we show Rsp5 localization in cortical patches and demonstrate its involvement in actin cytoskeleton organization and dynamics. We found that the Rsp5-F1-GFP2 N-terminal fragment and full length GFP-Rsp5 were recruited to peripheral patches that temporarily co-localized with Abp1-mCherry, a marker of actin patches. Actin cytoskeleton organization was defective in a strain lacking RSP5 or overexpressing RSP5, and this phenotype was accompanied by morphological abnormalities. Overexpression of RSP5 caused hypersensitivity of cells to Latrunculin A, an actin-depolymerizing drug and was toxic to cells lacking Las17, an activator of actin nucleation. Moreover, Rsp5 was required for efficient actin polymerization in a whole cell extract based in vitro system. Rsp5 interacted with Las17 and Las17-binding proteins, Lsb1 and Lsb2, in a GST-Rsp5-WW2/3 pull down assay. Rsp5 ubiquitinated Lsb1-HA and Lsb2-HA without directing them for degradation. Overexpression of RSP5 increased the cellular level of HA-Las17 in wild type and in lsb1Δ lsb2Δ strains in which the basal level of Las17 was already elevated. This increase was prevented in a strain devoid of Las17-binding protein Sla1 which is also a target of Rsp5 ubiquitination. Thus, Rsp5 together with Lsb1, Lsb2 and Sla1 regulate the level of Las17, an important activator of actin polymerization.

  7. Early nucleation events in the polymerization of actin, probed by time-resolved small-angle x-ray scattering

    PubMed Central

    Oda, Toshiro; Aihara, Tomoki; Wakabayashi, Katsuzo

    2016-01-01

    Nucleators generating new F-actin filaments play important roles in cell activities. Detailed information concerning the events involved in nucleation of actin alone in vitro is fundamental to understanding these processes, but such information has been hard to come by. We addressed the early process of salt-induced polymerization of actin using the time-resolved synchrotron small-angle X-ray scattering (SAXS). Actin molecules in low salt solution maintain a monomeric state by an electrostatic repulsive force between molecules. On mixing with salts, the repulsive force was rapidly screened, causing an immediate formation of many of non-polymerizable dimers. SAXS kinetic analysis revealed that tetramerization gives the highest energetic barrier to further polymerization, and the major nucleation is the formation of helical tetramers. Filaments start to grow rapidly with the formation of pentamers. These findings suggest an acceleration mechanism of actin assembly by a variety of nucleators in cells. PMID:27775032

  8. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  9. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  10. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  11. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of electric... to reduce contact resistance. (7) Energize all power conductors of the test specimen with...

  12. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of electric... to reduce contact resistance. (7) Energize all power conductors of the test specimen with...

  13. 47 CFR 76.640 - Support for unidirectional digital cable products on digital cable systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Support for unidirectional digital cable products on digital cable systems. 76.640 Section 76.640 Telecommunication FEDERAL COMMUNICATIONS... Standards § 76.640 Support for unidirectional digital cable products on digital cable systems. (a)...

  14. 47 CFR 76.640 - Support for unidirectional digital cable products on digital cable systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Support for unidirectional digital cable products on digital cable systems. 76.640 Section 76.640 Telecommunication FEDERAL COMMUNICATIONS... Standards § 76.640 Support for unidirectional digital cable products on digital cable systems. (a)...

  15. 47 CFR 76.990 - Small cable operators.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Small cable operators. 76.990 Section 76.990... CABLE TELEVISION SERVICE Cable Rate Regulation § 76.990 Small cable operators. (a) Effective February 8, 1996, a small cable operator is exempt from rate regulation on its cable programming services tier,...

  16. 47 CFR 76.990 - Small cable operators.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Small cable operators. 76.990 Section 76.990... CABLE TELEVISION SERVICE Cable Rate Regulation § 76.990 Small cable operators. (a) Effective February 8, 1996, a small cable operator is exempt from rate regulation on its cable programming services tier,...

  17. Online Cable Tester and Rerouter

    NASA Technical Reports Server (NTRS)

    Lewis, Mark; Medelius, Pedro

    2012-01-01

    Hardware and algorithms have been developed to transfer electrical power and data connectivity safely, efficiently, and automatically from an identified damaged/defective wire in a cable to an alternate wire path. The combination of online cable testing capabilities, along with intelligent signal rerouting algorithms, allows the user to overcome the inherent difficulty of maintaining system integrity and configuration control, while autonomously rerouting signals and functions without introducing new failure modes. The incorporation of this capability will increase the reliability of systems by ensuring system availability during operations.

  18. Equalization of data transmission cable

    NASA Technical Reports Server (NTRS)

    Zobrist, G. W.

    1975-01-01

    The paper describes an equalization approach utilizing a simple RLC network which can obtain a maximum slope of -12dB/octave for reshaping the frequency characteristics of a data transmission cable, so that data may be generated and detected at the receiver. An experimental procedure for determining equalizer design specifications using distortion analysis is presented. It was found that for lengths of 16 PEV-L cable of up to 5 miles and data transmission rates of up to 1 Mbs, the equalization scheme proposed here is sufficient for generation of the data with acceptable error rates.

  19. ERK and phosphoinositide 3-kinase temporally coordinate different modes of actin-based motility during embryonic wound healing.

    PubMed

    Li, Jingjing; Zhang, Siwei; Soto, Ximena; Woolner, Sarah; Amaya, Enrique

    2013-11-01

    Embryonic wound healing provides a perfect example of efficient recovery of tissue integrity and homeostasis, which is vital for survival. Tissue movement in embryonic wound healing requires two functionally distinct actin structures: a contractile actomyosin cable and actin protrusions at the leading edge. Here, we report that the discrete formation and function of these two structures is achieved by the temporal segregation of two intracellular upstream signals and distinct downstream targets. The sequential activation of ERK and phosphoinositide 3-kinase (PI3K) signalling divides Xenopus embryonic wound healing into two phases. In the first phase, activated ERK suppresses PI3K activity, and is responsible for the activation of Rho and myosin-2, which drives actomyosin cable formation and constriction. The second phase is dominated by restored PI3K signalling, which enhances Rac and Cdc42 activity, leading to the formation of actin protrusions that drive migration and zippering. These findings reveal a new mechanism for coordinating different modes of actin-based motility in a complex tissue setting, namely embryonic wound healing.

  20. Hawaii Deep Water Cable Program: Executive Summary

    SciTech Connect

    1990-09-01

    The Hawaii Deep Water Cable Program has succeeded unequivocally in determining the feasibility of deploying a submarine power cable system between the islands of Hawaii and Oahu. Major accomplishments of the program include designing, fabricating and testing an appropriate power cable, developing an integrated system to control all aspects of the cable laying operation, and testing all deployment systems at sea in the most challenging sections of the route.

  1. NEMA wire and cable standards development programs

    NASA Technical Reports Server (NTRS)

    Baird, Robert W.

    1994-01-01

    The National Electrical Manufacturers Association (NEMA) is the nation's largest trade association for manufacturers of electrical equipment. Its member companies produce components, end-use equipment and systems for the generation, transmission, distribution, control and use of electricity. The wire and cable division is presented in 6 sections: building wire and cable, fabricated conductors, flexible cords, high performance wire and cable, magnet wire, and power and control cable. Participating companies are listed.

  2. Open Source Cable Models for EMI Simulations

    NASA Astrophysics Data System (ADS)

    Greedy, S.; Smartt, C.; Thomas, D. W. P.

    2016-05-01

    This paper describes the progress of work towards an Open Source software toolset suitable for developing Spice based multi-conductor cable models. The issues related to creating a transmission line model for implementation in Spice which include the frequency dependent properties of real cables are presented and the viability of spice cable models is demonstrated through application to a three conductor crosstalk model. Development of the techniques to include models of shielded cables and incident field excitation has been demonstrated.

  3. Nuclear Actin in Development and Transcriptional Reprogramming

    PubMed Central

    Misu, Shinji; Takebayashi, Marina; Miyamoto, Kei

    2017-01-01

    Actin is a highly abundant protein in eukaryotic cells and dynamically changes its polymerized states with the help of actin-binding proteins. Its critical function as a constituent of cytoskeleton has been well-documented. Growing evidence demonstrates that actin is also present in nuclei, referred to as nuclear actin, and is involved in a number of nuclear processes, including transcriptional regulation and chromatin remodeling. The contribution of nuclear actin to transcriptional regulation can be explained by its direct interaction with transcription machineries and chromatin remodeling factors and by controlling the activities of transcription factors. In both cases, polymerized states of nuclear actin affect the transcriptional outcome. Nuclear actin also plays an important role in activating strongly silenced genes in somatic cells for transcriptional reprogramming. When these nuclear functions of actin are considered, it is plausible to speculate that nuclear actin is also implicated in embryonic development, in which numerous genes need to be activated in a well-coordinated manner. In this review, we especially focus on nuclear actin’s roles in transcriptional activation, reprogramming and development, including stem cell differentiation and we discuss how nuclear actin can be an important player in development and cell differentiation. PMID:28326098

  4. Development of termination and utilization concepts for flat conductor cables. Volume 3: Cost study comparison, flat versus round conductor cable

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A cost study comparing flat conductor cable (FCC) with small-gage wire (SGW) and conventional round conductor cable (RCC) is presented. This study was based on a vehicle wiring system consisting of 110,000 ft of conventional RCC equally divided between AWG sizes 20,22, and 24 using MIL-W-81044-type wire and MIL-C-26500 circular connectors. Basic cost data were developed on a similar-sized commercial jet airplane wiring system on a previous company R&D program in which advanced wiring techniques were carried through equivalent installations on an airplane mockup; and on data developed on typical average bundles during this program. Various cost elements included were engineering labor, operations (manufacturing) labor, material costs, and cost impact on payload. Engineering labor includes design, wiring system integration, wiring diagrams and cable assembly drawings, wire installations, and other related supporting functions such as the electronic data processing for the wiring. Operations labor includes mockup, tooling and production planning, fabrication, assembly, installation, and quality control cost impact on payload is the conversion of wiring system weight variations through use of different wiring concepts to program payload benefits in terms of dollars.

  5. Dynamic Termination On Radiating Coaxial Cable

    NASA Technical Reports Server (NTRS)

    Lombardi, Robert; Stern, Jon; Rassweiler, George

    1993-01-01

    Radiation pattern dithered to reduce adverse effect of nulls. In improved system for radio communication between base station and portable units within building, tunnel, ship, or other large structure, radiating or "leaky" coaxial cable serves as base-station antenna, and radiation pattern of cable dithered by dithering impedance of termination at end of cable remote from base station.

  6. Your Personal Genie in the Cable.

    ERIC Educational Resources Information Center

    Schlafly, Hubert J.

    The technology necessary for the use of cable television (TV) has been invented; it simply must be put to use. By the 1970's, cable TV should be commonplace in this country. Its rapid growth was caused in part by its appearance at a time of explosive expansion of related technologies like data theory and computer design. The coaxial cable system…

  7. Cable: Report to the President, 1974.

    ERIC Educational Resources Information Center

    Office of Telecommunications Policy, Washington, DC.

    A comprehensive, new national policy for cable communications is recommended by the Cabinet Committee on Cable Communications. The goal of the policy is to achieve the orderly integration of cable with other existing communications media so that information may flow freely, protected from both private and governmental barriers. The first two…

  8. 47 CFR 32.2422 - Underground cable.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Underground cable. 32.2422 Section 32.2422 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES UNIFORM SYSTEM OF ACCOUNTS..., Buried Cable. (d) The cost of cables leading from the main distributing frame or equivalent to...

  9. 47 CFR 32.2421 - Aerial cable.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... the original cost of single or paired conductor cable, wire and other associated material used in... cable or aerial wire as well as the cost of other material used in construction of such plant... cost of optical fiber cable and other associated material used in constructing a physical path for...

  10. F-actin rearrangement is regulated by mTORC2/Akt/Girdin in mouse fertilized eggs.

    PubMed

    Wu, Didi; Yu, Dahai; Wang, Xiuxia; Yu, Bingzhi

    2016-12-01

    In mouse fertilized eggs, correct assembly and distribution of the actin cytoskeleton are intimately related to cleavage in early-stage embryos. However, in mouse fertilized eggs, mechanisms and involved factors responsible for regulating the actin cytoskeleton are poorly defined. In this study, mTORC2, PKB/Akt and Girdin were found to modulate division of mouse fertilized eggs by regulating distribution of the actin cytoskeleton. RNA interference (RNAi)-mediated depletion of mTORC2, Akt1 or Girdin disrupted F-actin rearrangement and strongly inhibited egg development. PKB/Akt has been proven to be a downstream target of the mTORC2 signalling pathway. Girdin, a newly found actin cross-linker, has been proven to be a downstream target of the Akt signalling pathway. Furthermore, phosphorylation of both Akt1 and girdin was affected by knockdown of mTORC2. Akt1 positively regulated development of the mouse fertilized eggs by girdin-mediated F-actin rearrangement. Thus it seems that girdin could be a downstream target of the Akt1-mediated signalling pathway. Collectively, this study aimed to prove participation of mTORC2/Akt in F-actin assembly in early-stage cleavage of mouse fertilized eggs via the function of girdin.

  11. Actin dynamics in mouse fibroblasts in microgravity

    NASA Astrophysics Data System (ADS)

    Moes, Maarten J. A.; Bijvelt, Jose J.; Boonstra, Johannes

    2007-09-01

    After stimulating with the growth factor PDGF, cells exhibit abundant membrane ruffling and other morphological changes under normal gravity conditions. These morphological changes are largely determined by the actin microfilament system. Now these actin dynamics were studied under microgravity conditions in mouse fibroblasts during the DELTA mission. The aim of the present study was to describe the actin morphology in detail, to establish the effect of PDGF on actin morphology and to study the role of several actin-interacting proteins involved in introduced actin dynamics in microgravity. Identical experiments were conducted at 1G on earth as a reference. No results in microgravity were obtained due to a combination of malfunctioning hardware and unfulfilled temperature requirements.

  12. The actin cytoskeleton in endothelial cell phenotypes

    PubMed Central

    Prasain, Nutan; Stevens, Troy

    2009-01-01

    Endothelium forms a semi-permeable barrier that separates blood from the underlying tissue. Barrier function is largely determined by cell-cell and cell-matrix adhesions that define the limits of cell borders. Yet, such cell-cell and cell-matrix tethering is critically reliant upon the nature of adherence within the cell itself. Indeed, the actin cytoskeleton fulfills this essential function, to provide a strong, dynamic intracellular scaffold that organizes integral membrane proteins with the cell’s interior, and responds to environmental cues to orchestrate appropriate cell shape. The actin cytoskeleton is comprised of three distinct, but interrelated structures, including actin cross-linking of spectrin within the membrane skeleton, the cortical actin rim, and actomyosin-based stress fibers. This review addresses each of these actin-based structures, and discusses cellular signals that control the disposition of actin in different endothelial cell phenotypes. PMID:19028505

  13. Cable Television: Developing Community Services.

    ERIC Educational Resources Information Center

    Carpenter-Huffman, Polly; And Others

    The final volume of a four-volume study focuses on community use of cable television systems. Four separate aspects are discussed extensively: the possibilities of public access, use in municipal service applications, uses in education, and a guide for education planners. Each section contains several appendixes and the education sections include…

  14. Educational Uses of Cable Television.

    ERIC Educational Resources Information Center

    Cable Television Information Center, Washington, DC.

    The different educational uses of cable television as well as the methods and problems of that use are described in a state of the art review. The Federal Communications Commission regulations and related franchise activity are described, and the methods of using the educational channel as open or closed circuit TV or pay TV are indicated for…

  15. Optical Fiber Communications Cable Connector.

    DTIC Science & Technology

    1981-07-01

    incorp- oration of the TRW Cinch Optalign 4 double elbow " fiber alignment guide concept. Means for connecting either Siecor or ITT six fiber cable were...the guide, and forced toward the top cusp by the double elbow con- figuration. The geometry of the guide is such that normal tolerances of molded or

  16. Cable Television and Satellite Broadcasting

    DTIC Science & Technology

    1990-05-31

    a TV set from manufacturer A of the interconnection agreement negotiated with Mer- can talk to a VCR from manufacturer B and a compact cury or...Broadcasting Structure for the Next Decade, sion of cable’s unique programing. The expansion began Madame Catherine Tasca, Ministre Delegue Charge de with

  17. Selecting a Cable System Operator.

    ERIC Educational Resources Information Center

    Cable Television Information Center, Washington, DC.

    Intended to assist franchising authorities with the process of selecting a cable television system operator from franchise applicants, this document provides a framework for analysis of individual applications. Section 1 deals with various methods which can be used to select an operator. The next section covers the application form, the vehicle a…

  18. Interactive Cable Television. Final Report.

    ERIC Educational Resources Information Center

    Active Learning Systems, Inc., Minneapolis, MN.

    This report describes an interactive video system developed by Active Learning Systems which utilizes a cable television (TV) network as its delivery system to transmit computer literacy lessons to high school and college students. The system consists of an IBM PC, Pioneer LDV 4000 videodisc player, and Whitney Supercircuit set up at the head end…

  19. 300 Area signal cable study

    SciTech Connect

    Whattam, J.W.

    1994-09-15

    This report was prepared to discuss the alternatives available for removing the 300 Area overhead signal cable system. This system, installed in 1969, has been used for various monitoring and communication signaling needs throughout the 300 Area. Over the years this cabling system has deteriorated, has been continually reconfigured, and has been poorly documented to the point of nonreliability. The first step was to look at the systems utilizing the overhead signal cable that are still required for operation. Of the ten systems that once operated via the signal cable, only five are still required; the civil defense evacuation alarms, the public address (PA) system, the criticality alarms, the Pacific Northwest Laboratory Facilities Management Control System (FMCS), and the 384 annunciator panel. Of these five, the criticality alarms and the FMCS have been dealt with under other proposals. Therefore, this study focused on the alternatives available for the remaining three systems (evacuation alarms, PA system, and 384 panel) plus the accountability aid phones. Once the systems to be discussed were determined, then three alternatives for providing the signaling pathway were examined for each system: (1) re-wire using underground communication ducts, (2) use the Integrated Voice/Data Telecommunications System (IVDTS) already installed and operated by US West, and (3) use radio control. Each alternative was developed with an estimated cost, advantages, and disadvantages. Finally, a recommendation was provided for the best alternative for each system.

  20. COUPLER FOR TOOL AND CABLE

    DOEpatents

    Cawley, W.E.; Frantz, C.E.

    1962-02-27

    A two-part device is designed for pulling a splitting tool through a fuel tube. The device can be readily disconnected by unthreading the parts by means of a movable head carrying a transverse key which fits into a slot in the threaded part attached to the cable. (AEC)