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Sample records for growth cone motility

  1. Mechanochemical regulation of growth cone motility

    PubMed Central

    Kerstein, Patrick C.; Nichol, Robert H.; Gomez, Timothy M.

    2015-01-01

    Neuronal growth cones are exquisite sensory-motor machines capable of transducing features contacted in their local extracellular environment into guided process extension during development. Extensive research has shown that chemical ligands activate cell surface receptors on growth cones leading to intracellular signals that direct cytoskeletal changes. However, the environment also provides mechanical support for growth cone adhesion and traction forces that stabilize leading edge protrusions. Interestingly, recent work suggests that both the mechanical properties of the environment and mechanical forces generated within growth cones influence axon guidance. In this review we discuss novel molecular mechanisms involved in growth cone force production and detection, and speculate how these processes may be necessary for the development of proper neuronal morphogenesis. PMID:26217175

  2. Actin Dynamics in Growth Cone Motility and Navigation

    PubMed Central

    Gomez, Timothy M.; Letourneau, Paul C.

    2014-01-01

    Motile growth cones lead growing axons through developing tissues to synaptic targets. These behaviors depend on the organization and dynamics of actin filaments that fill the growth cone leading margin (peripheral (P-) domain). Actin filament organization in growth cones is regulated by actin-binding proteins that control all aspects of filament assembly, turnover, interactions with other filaments and cytoplasmic components, and participation in producing mechanical forces. Actin filament polymerization drives protrusion of sensory filopodia and lamellipodia, and actin filament connections to the plasma membrane link the filament network to adhesive contacts of filopodia and lamellipodia with other surfaces. These contacts stabilize protrusions and transduce mechanical forces generated by actomyosin activity into traction that pulls an elongating axon along the path towards its target. Adhesive ligands and extrinsic guidance cues bind growth cone receptors and trigger signaling activities involving Rho GTPases, kinases, phosphatases, cyclic nucleotides and [Ca++] fluxes. These signals regulate actin binding proteins to locally modulate actin polymerization, interactions and force transduction to steer the growth cone leading margin towards the sources of attractive cues and away from repellent guidance cues. PMID:24164353

  3. The role of microtubule dynamics in growth cone motility and axonal growth

    PubMed Central

    1995-01-01

    The growth cone contains dynamic and relatively stable microtubule populations, whose function in motility and axonal growth is uncharacterized. We have used vinblastine at low doses to inhibit microtubule dynamics without appreciable depolymerization to probe the role of these dynamics in growth cone behavior. At doses of vinblastine that interfere only with dynamics, the forward and persistent movement of the growth cone is inhibited and the growth cone wanders without appreciable forward translocation; it quickly resumes forward growth after the vinblastine is washed out. Direct visualization of fluorescently tagged microtubules in these neurons shows that in the absence of dynamic microtubules, the remaining mass of polymer does not invade the peripheral lamella and does not undergo the usual cycle of bundling and splaying and the growth cone stops forward movement. These experiments argue for a role for dynamic microtubules in allowing microtubule rearrangements in the growth cone. These rearrangements seem to be necessary for microtubule bundling, the subsequent coalescence of the cortex around the bundle to form new axon, and forward translocation of the growth cone. PMID:7822411

  4. Live cell imaging of neuronal growth cone motility and guidance in vitro

    PubMed Central

    Suter, Daniel M.

    2013-01-01

    Summary The neuronal growth cone, a highly motile structure at the tip of neuronal processes, is an excellent model system for studying directional cell movements. While biochemical and genetic approaches unveiled molecular interactions between ligand, receptor, signaling and cytoskeleton-associated proteins controlling axonal growth and guidance, in vitro live cell imaging has emerged as a crucial approach for dissecting cellular mechanisms of growth cone motility and guidance. Important insights into these mechanisms have been gained from studies using the large growth cones elaborated by Aplysia californica neurons, an outstanding model system for live cell imaging for a number of reasons. Identified neurons can be isolated and imaged at room temperature. Aplysia growth cones are 5–10 times larger than growth cones from other species, making them suitable for quantitative high-resolution imaging of cytoskeletal protein dynamics and biophysical approaches. Lastly, protein, RNA, fluorescent probes and small molecules can be microinjected into the neuronal cell body for localization and functional studies. The following chapter describes culturing of Aplysia bag cell neurons, live cell imaging of neuronal growth cones using differential interference contrast and fluorescent speckle microscopy as well as the restrained bead interaction assay to induce adhesion-mediated growth cone guidance in vitro. PMID:21748670

  5. Control of neurite outgrowth and growth cone motility by phosphatidylinositol-3-kinase.

    PubMed

    Tornieri, Karine; Welshhans, Kristy; Geddis, Matthew S; Rehder, Vincent

    2006-04-01

    Phosphatidylinositol-3-kinase (PI-3K) has been reported to affect neurite outgrowth both in vivo and in vitro. Here we investigated the signaling pathways by which PI-3K affects neurite outgrowth and growth cone motility in identified snail neurons in vitro. Inhibition of PI-3K with wortmannin (2 microM) or LY 294002 (25 microM) resulted in a significant elongation of filopodia and in a slow-down of neurite outgrowth. Experiments using cytochalasin and blebbistatin, drugs that interfere with actin polymerization and myosin II activity, respectively, demonstrated that filopodial elongation resulting from PI-3K inhibition was dependent on actin polymerization. Inhibition of strategic kinases located downstream of PI-3K, such as Akt, ROCK, and MEK, also caused significant filopodial elongation and a slow-down in neurite outgrowth. Another growth cone parameter, filopodial number, was not affected by inhibition of PI-3K, Akt, ROCK, or MEK. A detailed study of growth cone behavior showed that the filopodial elongation induced by inhibiting PI-3K, Akt, ROCK, and MEK was achieved by increasing two motility parameters: the rate with which filopodia extend (extension rate) and the time that filopodia spend elongating. Whereas the inhibition of ROCK or Akt (both activated by the lipid kinase activity of PI-3K) and MEK (activated by the protein kinase activity of PI-3K) had additive effects, simultaneous inhibition of Akt and ROCK showed no additive effect. We further demonstrate that the effects on filopodial dynamics investigated were calcium-independent. Taken together, our results suggest that inhibition of PI-3K signaling results in filopodial elongation and a slow-down of neurite advance, reminiscent of growth cone searching behavior.

  6. Talin and vinculin play distinct roles in filopodial motility in the neuronal growth cone

    PubMed Central

    1996-01-01

    Filopodial motility is critical for many biological processes, particularly for axon guidance. This motility is based on altering the F-actin-based cytoskeleton, but the mechanisms of how this occurs and the actin-associated proteins that function in this process remain unclear. We investigated two of these proteins found in filopodia, talin and vinculin, by inactivating them in subregions of chick dorsal root ganglia neuronal growth cones and by observing subsequent behavior by video-enhanced microscopy and quantitative morphometry. Microscale chromophore-assisted laser inactivation of talin resulted in the temporary cessation of filopodial extension and retraction. Inactivation of vinculin caused an increased incidence of filopodial bending and buckling within the laser spot but had no effect on extension or retraction. These findings show that talin acts in filopodial motility and may couple both extension and retraction to actin dynamics. They also suggest that vinculin is not required for filopodial extension and retraction but plays a role in the structural integrity of filopodia. PMID:8794861

  7. The SH2/SH3 adaptor protein dock interacts with the Ste20-like kinase misshapen in controlling growth cone motility.

    PubMed

    Ruan, W; Pang, P; Rao, Y

    1999-11-01

    Recent studies suggest that the SH2/SH3 adaptor Dock/Nck transduces tyrosine phosphorylation signals to the actin cytoskeleton in regulating growth cone motility. The signaling cascade linking the action of Dock/Nck to the reorganization of cytoskeleton is poorly understood. We now demonstrate that Dock interacts with the Ste20-like kinase Misshapen (Msn) in the Drosophila photoreceptor (R cell) growth cones. Loss of msn causes a failure of growth cones to stop at the target, a phenotype similar to loss of dock, whereas overexpression of msn induces pretarget growth cone termination. Physical and genetic interactions between Msn and Dock indicate a role for Msn in the Dock signaling pathway. We propose that Msn functions as a key controller of growth cone cytoskeleton in response to Dock-mediated signals.

  8. Transient receptor potential vanilloid 2 activation by focal mechanical stimulation requires interaction with the actin cytoskeleton and enhances growth cone motility.

    PubMed

    Sugio, Shouta; Nagasawa, Masami; Kojima, Itaru; Ishizaki, Yasuki; Shibasaki, Koji

    2017-04-01

    We have previously reported that transient receptor potential vanilloid 2 (TRPV2) can be activated by mechanical stimulation, which enhances axonal outgrowth in developing neurons; however, the molecular mechanisms that govern the contribution of TRPV2 activation to axonal outgrowth remain unclear. In the present study, we examined this mechanism by using PC12 cells as a neuronal model. Overexpression of TRPV2 enhanced axonal outgrowth in a mechanical stimulus-dependent manner. Accumulation of TRPV2 at the cell surface was 4-fold greater in the growth cone compared with the soma. In the growth cone, TRPV2 is not static, but dynamically accumulates (within ∼100 ms) to the site of mechanical stimulation. The dynamic and acute clustering of TRPV2 can enhance very weak mechanical stimuli via focal accumulation of TRPV2. Focal application of mechanical stimuli dramatically increased growth cone motility and caused actin reorganization via activation of TRPV2. We also found that TRPV2 physically interacts with actin and that changes in the actin cytoskeleton are required for its activation. Here, we demonstrated for the first time to our knowledge that TRPV2 clustering is induced by mechanical stimulation generated by axonal outgrowth and that TRPV2 activation is triggered by actin rearrangements that result from mechanical stimulation. Moreover, TRPV2 activation enhances growth cone motility and actin accumulation to promote axonal outgrowth. Sugio, S., Nagasawa, M., Kojima, I., Ishizaki, Y., Shibasaki, K. Transient receptor potential vanilloid 2 activation by focal mechanical stimulation requires interaction with the actin cytoskeleton and enhances growth cone motility. © FASEB.

  9. Motility flow and growth-cone navigation analysis during in vitro neuronal development by long-term bright-field imaging.

    PubMed

    Aviv, Maya Shalev; Pesce, Mattia; Tilve, Sharada; Chieregatti, Evelina; Zalevsky, Zeev; Difato, Francesco

    2013-11-01

    A long-term live-imaging workstation to follow the development of cultured neurons during the first few days in vitro (DIV) is developed. In order to monitor neuronal polarization and axonal growth by live imaging, we built a micro-incubator system that provides stable temperature, pH, and osmolarity in the culture dish under the microscope, while preserving environment sterility. We are able to image living neurons at 2 DIVs for 48 h with a temporal resolution of one frame for every 2 min. The main features of this system are its ability to adapt to every cell-culture support, to integrate in any optical microscope, because of the relatively small dimensions (9.5×6.5×2.5  cm) and low weight of the system (<200  g), and to monitor the physiological parameters in situ. Moreover, we developed an image-analysis algorithm to quantify the cell motility, in order to characterize its complex temporal-spatial pattern. The algorithm applies morphological image processing operations on the temporal variations occurring in the inspected region of interest. Here, it is used to automatically detect cellular motility in three distinct morphological regions of the neurons: around the soma, along the neurites, and in the growth cone.

  10. Vesicular movements in the growth cone.

    PubMed

    Nozumi, Motohiro; Igarashi, Michihiro

    2017-09-27

    Growth cones, which are the highly motile tips of extending neuronal processes in developing neurons, have many vesicles. These vesicles are likely essential for the membrane expansion that is required for nerve growth, and probably coordinate with rearrangement of the cytoskeletons. Such mechanisms are poorly understood from molecular and cell biological aspects. Recently, we used superresolution microscopic approaches and described new mechanisms that are involved in the interaction between the vesicles and F-actin in the leading edge of the peripheral domain. Vesicles mainly accumulate in the central domain of growth cones. However, the dynamics of vesicles in each domain, for example, clathrin dependency, are totally distinct from each other. Here, we discuss the diversity of the dynamics of vesicular and related proteins that play different roles in nerve growth. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Actin-binding proteins take the reins in growth cones.

    PubMed

    Pak, Chi W; Flynn, Kevin C; Bamburg, James R

    2008-02-01

    Higher-order actin-based networks (actin superstructures) are important for growth-cone motility and guidance. Principles for generating, organizing and remodelling actin superstructures have emerged from recent findings in cell-free systems, non-neuronal cells and growth cones. This Review examines how actin superstructures are initiated de novo at the leading-edge membrane and how the spontaneous organization of actin superstructures is driven by ensembles of actin-binding proteins. How the regulation of actin-binding proteins can affect growth-cone turning and axonal regeneration is also discussed.

  12. Autonomous regulation of growth cone filopodia.

    PubMed

    Rehder, V; Cheng, S

    1998-02-05

    The fan-shaped array of filopodia is the first site of contact of a neuronal growth cone with molecules encountered during neuronal pathfinding. Filopodia are highly dynamic structures, and the "action radius" of a growth cone is strongly determined by the length and number of its filopodia. Since interactions of filopodia with instructive cues in the vicinity of the growth cone can have effects on growth cone morphology within minutes, it has to be assumed that a large part of the signaling underlying such morphological changes resides locally within the growth cone proper. In this study, we tested the hypothesis that two important growth cone parameters-namely, the length and number of its filopodia-are regulated autonomously in the growth cone. We previously demonstrated in identified neurons from the snail Helisoma trivolvis that filopodial length and number are regulated by intracellular calcium. Here, we investigated filopodial dynamics and their regulation by the second-messenger calcium in growth cones which were physically isolated from their parent neuron by neurite transection. Our results show that isolated growth cones have longer but fewer filopodia than growth cones attached to their parent cell. These isolated growth cones, however, are fully capable of undergoing calcium-induced cytoskeletal changes, suggesting that the machinery necessary to perform changes in filopodial length and number is fully intrinsic to the growth cone proper.

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

    PubMed

    Marsick, Bonnie M; Letourneau, Paul C

    2011-03-17

    The motile tips of growing axons are called growth cones. Growth cones lead navigating axons through developing tissues by interacting with locally expressed molecular guidance cues that bind growth cone receptors and regulate the dynamics and organization of the growth cone cytoskeleton. The main target of these navigational signals is the actin filament meshwork that fills the growth cone periphery and that drives growth cone motility through continual actin polymerization and dynamic remodeling. Positive or attractive guidance cues induce growth cone turning by stimulating actin filament (F-actin) polymerization in the region of the growth cone periphery that is nearer the source of the attractant cue. This actin polymerization drives local growth cone protrusion, adhesion of the leading margin and axonal elongation toward the attractant. Actin filament polymerization depends on the availability of sufficient actin monomer and on polymerization nuclei or actin filament barbed ends for the addition of monomer. Actin monomer is abundantly available in chick retinal and dorsal root ganglion (DRG) growth cones. Consequently, polymerization increases rapidly when free F-actin barbed ends become available for monomer addition. This occurs in chick DRG and retinal growth cones via the local activation of the F-actin severing protein actin depolymerizing factor (ADF/cofilin) in the growth cone region closer to an attractant. This heightened ADF/cofilin activity severs actin filaments to create new F-actin barbed ends for polymerization. The following method demonstrates this mechanism. Total content of F-actin is visualized by staining with fluorescent phalloidin. F-actin barbed ends are visualized by the incorporation of rhodamine-actin within growth cones that are permeabilized with the procedure described in the following, which is adapted from previous studies of other motile cells. When rhodamine-actin is added at a concentration above the critical concentration

  14. Growth cone travel in space and time: the cellular ensemble of cytoskeleton, adhesion, and membrane.

    PubMed

    Vitriol, Eric A; Zheng, James Q

    2012-03-22

    Growth cones, found at the tip of axonal projections, are the sensory and motile organelles of developing neurons that enable axon pathfinding and target recognition for precise wiring of the neural circuitry. To date, many families of conserved guidance molecules and their corresponding receptors have been identified that work in space and time to ensure billions of axons to reach their targets. Research in the past two decades has also gained significant insight into the ways in which growth cones translate extracellular signals into directional migration. This review aims to examine new progress toward understanding the cellular mechanisms underlying directional motility of the growth cone and to discuss questions that remain to be addressed. Specifically, we will focus on the cellular ensemble of cytoskeleton, adhesion, and membrane and examine how the intricate interplay between these processes orchestrates the directed movement of growth cones.

  15. Growth Cone Biomechanics in Peripheral and Central Nervous System Neurons

    NASA Astrophysics Data System (ADS)

    Urbach, Jeffrey; Koch, Daniel; Rosoff, Will; Geller, Herbert

    2012-02-01

    The growth cone, a highly motile structure at the tip of an axon, integrates information about the local environment and modulates outgrowth and guidance, but little is known about effects of external mechanical cues and internal mechanical forces on growth-cone mediated guidance. We have investigated neurite outgrowth, traction forces and cytoskeletal substrate coupling on soft elastic substrates for dorsal root ganglion (DRG) neurons (from the peripheral nervous system) and hippocampal neurons (from the central) to see how the mechanics of the microenvironment affect different populations. We find that the biomechanics of DRG neurons are dramatically different from hippocampal, with DRG neurons displaying relatively large, steady traction forces and maximal outgrowth and forces on substrates of intermediate stiffness, while hippocampal neurons display weak, intermittent forces and limited dependence of outgrowth and forces on substrate stiffness. DRG growth cones have slower rates of retrograde actin flow and higher density of localized paxillin (a protein associated with substrate adhesion complexes) compared to hippocampal neurons, suggesting that the difference in force generation is due to stronger adhesions and therefore stronger substrate coupling in DRG growth cones.

  16. Substrate Deformation Predicts Neuronal Growth Cone Advance

    PubMed Central

    Athamneh, Ahmad I.M.; Cartagena-Rivera, Alexander X.; Raman, Arvind; Suter, Daniel M.

    2015-01-01

    Although pulling forces have been observed in axonal growth for several decades, their underlying mechanisms, absolute magnitudes, and exact roles are not well understood. In this study, using two different experimental approaches, we quantified retrograde traction force in Aplysia californica neuronal growth cones as they develop over time in response to a new adhesion substrate. In the first approach, we developed a novel method, to our knowledge, for measuring traction forces using an atomic force microscope (AFM) with a cantilever that was modified with an Aplysia cell adhesion molecule (apCAM)-coated microbead. In the second approach, we used force-calibrated glass microneedles coated with apCAM ligands to guide growth cone advance. The traction force exerted by the growth cone was measured by monitoring the microneedle deflection using an optical microscope. Both approaches showed that Aplysia growth cones can develop traction forces in the 100–102 nN range during adhesion-mediated advance. Moreover, our results suggest that the level of traction force is directly correlated to the stiffness of the microneedle, which is consistent with a reinforcement mechanism previously observed in other cell types. Interestingly, the absolute level of traction force did not correlate with growth cone advance toward the adhesion site, but the amount of microneedle deflection did. In cases of adhesion-mediated growth cone advance, the mean needle deflection was 1.05 ± 0.07 μm. By contrast, the mean deflection was significantly lower (0.48 ± 0.06 μm) when the growth cones did not advance. Our data support a hypothesis that adhesion complexes, which can undergo micron-scale elastic deformation, regulate the coupling between the retrogradely flowing actin cytoskeleton and apCAM substrates, stimulating growth cone advance if sufficiently abundant. PMID:26445437

  17. Kinematics of Cone-In-Cone Growth, with Implications for Timing and Formation Mechanism

    NASA Astrophysics Data System (ADS)

    Hooker, J. N.; Cartwright, J. A.

    2015-12-01

    Cone-in-cone is an enigmatic structure. Similar to many fibrous calcite veins, cone-in-cone is generally formed of calcite and present in bedding-parallel vein-like accumulations within fine-grained rocks. Unlike most fibrous veins, cone-in-cone contains conical inclusions of host-rock material, creating nested, parallel cones throughout. A long-debated aspect of cone-in-cone structures is whether the calcite precipitated with its conical form (primary cone-in-cone), or whether the cones formed afterwards (secondary cone-in-cone). Trace dolomite within a calcite cone-in-cone structure from the Cretaceous of Jordan supports the primary hypothesis. The host sediment is a siliceous mud containing abundant rhombohedral dolomite grains. Dolomite rhombohedra are also distributed throughout the cone-in-cone. The rhombohedra within the cones are randomly oriented yet locally have dolomite overgrowths having boundaries that are aligned with calcite fibers. Evidence that dolomite co-precipitated with calcite, and did not replace calcite, includes (i) preferential downward extension of dolomite overgrowths, in the presumed growth-direction of the cone-in-cone, and (ii) planar, vertical borders between dolomite crystals and calcite fibers. Because dolomite overgrows host-sediment rhombohedra and forms fibers within the cones, it follows that the host-sediment was included within the growing cone-in-cone as the calcite precipitated, and not afterward. The host-sediment was not injected into the cone-in-cone along fractures, as the secondary-origin hypothesis suggests. This finding implies that cone-in-cone in general does not form over multiple stages, and thus has greater potential to preserve the chemical signature of its original precipitation. Because cone-in-cone likely forms before complete lithification of the host, and because the calcite displaces the host material against gravity, this chemical signature can preserve information about early overpressures in fine

  18. Forces from the rear: deformed microtubules in neuronal growth cones influence retrograde flow and advancement

    NASA Astrophysics Data System (ADS)

    Rauch, Philipp; Heine, Paul; Goettgens, Barbara; Käs, Josef A.

    2013-01-01

    The directed motility of growth cones at the tip of neuronal processes is a key function in neuronal path-finding and relies on a complex system of interacting cytoskeletal components. Despite intensive research in this field, many aspects of the mechanical roles of actin structures and, in particular, of microtubules throughout this process remain unclear. Mostly, force generation is ascribed to actin-myosin-based structures such as filopodia bundles and the dynamic polymer gel within the lamellipodium. Our analysis of microtubule buckling and deformation in motile growth cones reveals that extending microtubule filaments contribute significantly to the overall protrusion force. In this study, we establish a relationship of the local variations in stored bending energy and deformation characteristics to growth cone morphology and retrograde actin flow. This implies the relevance of microtubule pushing and deformation for general neurite advancement as well as steering processes.

  19. Domain requirements for the Dock adapter protein in growth- cone signaling.

    PubMed

    Rao, Y; Zipursky, S L

    1998-03-03

    Tyrosine phosphorylation has been implicated in growth-cone guidance through genetic, biochemical, and pharmacological studies. Adapter proteins containing src homology 2 (SH2) domains and src homology 3 (SH3) domains provide a means of linking guidance signaling through phosphotyrosine to downstream effectors regulating growth-cone motility. The Drosophila adapter, Dreadlocks (Dock), the homolog of mammalian Nck containing three N-terminal SH3 domains and a single SH2 domain, is highly specialized for growth-cone guidance. In this paper, we demonstrate that Dock can couple signals in either an SH2-dependent or an SH2-independent fashion in photoreceptor (R cell) growth cones, and that Dock displays different domain requirements in different neurons.

  20. Domain requirements for the Dock adapter protein in growth- cone signaling

    PubMed Central

    Rao, Yong; Zipursky, S. Lawrence

    1998-01-01

    Tyrosine phosphorylation has been implicated in growth-cone guidance through genetic, biochemical, and pharmacological studies. Adapter proteins containing src homology 2 (SH2) domains and src homology 3 (SH3) domains provide a means of linking guidance signaling through phosphotyrosine to downstream effectors regulating growth-cone motility. The Drosophila adapter, Dreadlocks (Dock), the homolog of mammalian Nck containing three N-terminal SH3 domains and a single SH2 domain, is highly specialized for growth-cone guidance. In this paper, we demonstrate that Dock can couple signals in either an SH2-dependent or an SH2-independent fashion in photoreceptor (R cell) growth cones, and that Dock displays different domain requirements in different neurons. PMID:9482841

  1. New Light on Growth Cone Navigation.

    PubMed

    Pollard, Thomas D

    2015-12-21

    Growth cones on neuronal process navigate over long distances to their targets in the developing nervous system. New work by Menon et al., 2015 in the current issue of Developmental Cell reveals that reversible ubiquitination of the actin filament polymerase called VASP is part of the guidance system. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Growth cone behavior and production of traction force

    PubMed Central

    1990-01-01

    The growth cone must push its substrate rearward via some traction force in order to propel itself forward. To determine which growth cone behaviors produce traction force, we observed chick sensory growth cones under conditions in which force production was accommodated by movement of obstacles in the environment, namely, neurites of other sensory neurons or glass fibers. The movements of these obstacles occurred via three, different, stereotyped growth cone behaviors: (a) filopodial contractions, (b) smooth rearward movement on the dorsal surface of the growth cone, and (c) interactions with ruffling lamellipodia. More than 70% of the obstacle movements were caused by filopodial contractions in which the obstacle attached at the extreme distal end of a filopodium and moved only as the filopodium changed its extension. Filopodial contractions were characterized by frequent changes of obstacle velocity and direction. Contraction of a single filopodium is estimated to exert 50-90 microdyn of force, which can account for the pull exerted by chick sensory growth cones. Importantly, all five cases of growth cones growing over the top of obstacle neurites (i.e., geometry that mimics the usual growth cone/substrate interaction), were of the filopodial contraction type. Some 25% of obstacle movements occurred by a smooth backward movement along the top surface of growth cones. Both the appearance and rate of movements were similar to that reported for retrograde flow of cortical actin near the dorsal growth cone surface. Although these retrograde flow movements also exerted enough force to account for growth cone pulling, we did not observe such movements on ventral growth cone surfaces. Occasionally obstacles were moved by interaction with ruffling lamellipodia. However, we obtained no evidence for attachment of the obstacles to ruffling lamellipodia or for directed obstacle movements by this mechanism. These data suggest that chick sensory growth cones move forward by

  3. Colony Expansion of Socially Motile Myxococcus xanthus Cells Is Driven by Growth, Motility, and Exopolysaccharide Production

    PubMed Central

    Patra, Pintu; Kissoon, Kimberley; Cornejo, Isabel; Kaplan, Heidi B.; Igoshin, Oleg A.

    2016-01-01

    Myxococcus xanthus, a model organism for studies of multicellular behavior in bacteria, moves exclusively on solid surfaces using two distinct but coordinated motility mechanisms. One of these, social (S) motility is powered by the extension and retraction of type IV pili and requires the presence of exopolysaccharides (EPS) produced by neighboring cells. As a result, S motility requires close cell-to-cell proximity and isolated cells do not translocate. Previous studies measuring S motility by observing the colony expansion of cells deposited on agar have shown that the expansion rate increases with initial cell density, but the biophysical mechanisms involved remain largely unknown. To understand the dynamics of S motility-driven colony expansion, we developed a reaction-diffusion model describing the effects of cell density, EPS deposition and nutrient exposure on the expansion rate. Our results show that at steady state the population expands as a traveling wave with a speed determined by the interplay of cell motility and growth, a well-known characteristic of Fisher’s equation. The model explains the density-dependence of the colony expansion by demonstrating the presence of a lag phase–a transient period of very slow expansion with a duration dependent on the initial cell density. We propose that at a low initial density, more time is required for the cells to accumulate enough EPS to activate S-motility resulting in a longer lag period. Furthermore, our model makes the novel prediction that following the lag phase the population expands at a constant rate independent of the cell density. These predictions were confirmed by S motility experiments capturing long-term expansion dynamics. PMID:27362260

  4. The trip of the tip: understanding the growth cone machinery

    PubMed Central

    Lowery, Laura Anne; Van Vactor, David

    2009-01-01

    Preface The central player in the road trip of axon guidance is the growth cone, a dynamic structure located at the tip of the growing axon. During its journey, the growth cone comprises both `vehicle' and `navigator'. Whereas the `vehicle' maintains growth cone movement and provides the cytoskeletal structural elements of its framework, a motor to move forward, and a mechanism to provide traction on the road, the `navigator' aspect guides this system in a spatially-biased way to translate environmental signals into directional movement. Understanding the functions and regulation of the vehicle and navigator provides new insights into the cell biology of growth cone guidance. PMID:19373241

  5. Oxygen radicals elicit paralysis and collapse of spinal cord neuron growth cones upon exposure to proinflammatory cytokines.

    PubMed

    Kuhn, Thomas B

    2014-01-01

    A persistent inflammatory and oxidative stress is a hallmark of most chronic CNS pathologies (Alzheimer's (ALS)) as well as the aging CNS orchestrated by the proinflammatory cytokines tumor necrosis factor alpha (TNFα) and interleukin-1 beta (IL-1β). Loss of the integrity and plasticity of neuronal morphology and connectivity comprises an early step in neuronal degeneration and ultimate decline of cognitive function. We examined in vitro whether TNFα or IL-1β impaired morphology and motility of growth cones in spinal cord neuron cultures. TNFα and IL-1β paralyzed growth cone motility and induced growth cone collapse in a dose-dependent manner reflected by complete attenuation of neurite outgrowth. Scavenging reactive oxygen species (ROS) or inhibiting NADPH oxidase activity rescued loss of neuronal motility and morphology. TNFα and IL-1β provoked rapid, NOX-mediated generation of ROS in advancing growth cones, which preceded paralysis of motility and collapse of morphology. Increases in ROS intermediates were accompanied by an aberrant, nonproductive reorganization of actin filaments. These findings suggest that NADPH oxidase serves as a pivotal source of oxidative stress in neurons and together with disruption of actin filament reorganization contributes to the progressive degeneration of neuronal morphology in the diseased or aging CNS.

  6. Oxygen Radicals Elicit Paralysis and Collapse of Spinal Cord Neuron Growth Cones upon Exposure to Proinflammatory Cytokines

    PubMed Central

    Kuhn, Thomas B.

    2014-01-01

    A persistent inflammatory and oxidative stress is a hallmark of most chronic CNS pathologies (Alzheimer's (ALS)) as well as the aging CNS orchestrated by the proinflammatory cytokines tumor necrosis factor alpha (TNFα) and interleukin-1 beta (IL-1β). Loss of the integrity and plasticity of neuronal morphology and connectivity comprises an early step in neuronal degeneration and ultimate decline of cognitive function. We examined in vitro whether TNFα or IL-1β impaired morphology and motility of growth cones in spinal cord neuron cultures. TNFα and IL-1β paralyzed growth cone motility and induced growth cone collapse in a dose-dependent manner reflected by complete attenuation of neurite outgrowth. Scavenging reactive oxygen species (ROS) or inhibiting NADPH oxidase activity rescued loss of neuronal motility and morphology. TNFα and IL-1β provoked rapid, NOX-mediated generation of ROS in advancing growth cones, which preceded paralysis of motility and collapse of morphology. Increases in ROS intermediates were accompanied by an aberrant, nonproductive reorganization of actin filaments. These findings suggest that NADPH oxidase serves as a pivotal source of oxidative stress in neurons and together with disruption of actin filament reorganization contributes to the progressive degeneration of neuronal morphology in the diseased or aging CNS. PMID:25050325

  7. Can hippocampal neurites and growth cones climb over obstacles?

    PubMed

    Lien, Thuy Linh; Ban, Jelena; Tormen, Massimo; Migliorini, Elisa; Grenci, Gianluca; Pozzato, Alessandro; Torre, Vincent

    2013-01-01

    Guidance molecules, such as Sema3A or Netrin-1, can induce growth cone (GC) repulsion or attraction in the presence of a flat surface, but very little is known of the action of guidance molecules in the presence of obstacles. Therefore we combined chemical and mechanical cues by applying a steady Netrin-1 stream to the GCs of dissociated hippocampal neurons plated on polydimethylsiloxane (PDMS) surfaces patterned with lines 2 µm wide, with 4 µm period and with a height varying from 100 to 600 nm. GC turning experiments performed 24 hours after plating showed that filopodia crawl over these lines within minutes. These filopodia do not show staining for the adhesion marker Paxillin. GCs and neurites crawl over lines 100 nm high, but less frequently and on a longer time scale over lines higher than 300 nm; neurites never crawl over lines 600 nm high. When neurons are grown for 3 days over patterned surfaces, also neurites can cross lines 300 nm and 600 nm high, grow parallel to and on top of these lines and express Paxillin. Axons - selectively stained with SMI 312 - do not differ from dendrites in their ability to cross these lines. Our results show that highly motile structures such as filopodia climb over high obstacle in response to chemical cues, but larger neuronal structures are less prompt and require hours or days to climb similar obstacles.

  8. Local calcium changes regulate the length of growth cone filopodia.

    PubMed

    Cheng, Su; Geddis, Matthew S; Rehder, Vincent

    2002-03-01

    Previous studies have demonstrated that the free intracellular calcium concentration ([Ca(2+)](i)) in growth cones can act as an important regulator of growth cone behavior. Here we investigated whether there is a spatial and temporal correlation between [Ca(2+)](i) and one particular aspect of growth cone behavior, namely the regulation of growth cone filopodia. Calcium was released from the caged compound NP-EGTA (o-nitrophenyl EGTA tetrapotassium salt) to simulate a signaling event in the form of a transient increase in [Ca(2+)](i). In three different experimental paradigms, we released calcium either globally (within an entire growth cone), regionally (within a small area of the lamellipodium), or locally (within a single filopodium). We demonstrate that global photolysis of NP-EGTA in growth cones caused a transient increase in [Ca(2+)](i) throughout the growth cone and elicited subsequent filopodial elongation that was restricted to the stimulated growth cone. Pharmacological blockage of either calmodulin or the Ca(2+)-dependent phosphatase, calcineurin, inhibited the effect of uncaging calcium, suggesting that these enzymes are acting downstream of calcium. Regional uncaging of calcium in the lamellipodium caused a regional increase in [Ca(2+)](i), but induced filopodial elongation on the entire growth cone. Elevation of [Ca(2+)](i) locally within an individual filopodium resulted in the elongation of only the stimulated filopodium. These findings suggest that the effect of an elevation of [Ca(2+)](i) on filopodial behavior depends on the spatial distribution of the calcium signal. In particular, calcium signals within filopodia can cause filopodial length changes that are likely a first step towards directed filopodial steering events seen during pathfinding in vivo.

  9. Syndecan promotes axon regeneration by stabilizing growth cone migration

    PubMed Central

    Edwards, Tyson J.; Hammarlund, Marc

    2014-01-01

    SUMMARY Growth cones facilitate the repair of nervous system damage by providing the driving force for axon regeneration. Using single-neuron laser axotomy and in vivo time-lapse imaging, we show that syndecan, a heparan sulfate (HS) proteoglycan, is required for growth cone function during axon regeneration in C. elegans. In the absence of syndecan, regenerating growth cones form but are unstable and collapse, decreasing the effective growth rate and impeding regrowth to target cells. We provide evidence that syndecan has two distinct functions during axon regeneration: 1) a canonical function in axon guidance that requires expression outside the nervous system and depends on HS chains, and 2) a novel intrinsic function in growth cone stabilization that is mediated by the syndecan core protein, independently of HS. Thus, syndecan is a novel regulator of a critical choke point in nervous system repair. PMID:25001284

  10. Growth cones as soft and weak force generators

    PubMed Central

    Betz, Timo; Koch, Daniel; Lu, Yun-Bi; Franze, Kristian; Käs, Josef A.

    2011-01-01

    Many biochemical processes in the growth cone finally target its biomechanical properties, such as stiffness and force generation, and thus permit and control growth cone movement. Despite the immense progress in our understanding of biochemical processes regulating neuronal growth, growth cone biomechanics remains poorly understood. Here, we combine different experimental approaches to measure the structural and mechanical properties of a growth cone and to simultaneously determine its actin dynamics and traction force generation. Using fundamental physical relations, we exploited these measurements to determine the internal forces generated by the actin cytoskeleton in the lamellipodium. We found that, at timescales longer than the viscoelastic relaxation time of τ = 8.5 ± 0.5 sec, growth cones show liquid-like characteristics, whereas at shorter time scales they behaved elastically with a surprisingly low elastic modulus of E = 106 ± 21 Pa. Considering the growth cone’s mechanical properties and retrograde actin flow, we determined the internal stress to be on the order of 30 pN per μm2. Traction force measurements confirmed these values. Hence, our results indicate that growth cones are particularly soft and weak structures that may be very sensitive to the mechanical properties of their environment. PMID:21813757

  11. Functional Complexity of the Axonal Growth Cone: A Proteomic Analysis

    PubMed Central

    Estrada-Bernal, Adriana; Sanford, Staci D.; Sosa, Lucas J.; Simon, Glenn C.; Hansen, Kirk C.; Pfenninger, Karl H.

    2012-01-01

    The growth cone, the tip of the emerging neurite, plays a crucial role in establishing the wiring of the developing nervous system. We performed an extensive proteomic analysis of axonal growth cones isolated from the brains of fetal Sprague-Dawley rats. Approximately 2000 proteins were identified at ≥99% confidence level. Using informatics, including functional annotation cluster and KEGG pathway analysis, we found great diversity of proteins involved in axonal pathfinding, cytoskeletal remodeling, vesicular traffic and carbohydrate metabolism, as expected. We also found a large and complex array of proteins involved in translation, protein folding, posttranslational processing, and proteasome/ubiquitination-dependent degradation. Immunofluorescence studies performed on hippocampal neurons in culture confirmed the presence in the axonal growth cone of proteins representative of these processes. These analyses also provide evidence for rough endoplasmic reticulum and reveal a reticular structure equipped with Golgi-like functions in the axonal growth cone. Furthermore, Western blot revealed the growth cone enrichment, relative to fetal brain homogenate, of some of the proteins involved in protein synthesis, folding and catabolism. Our study provides a resource for further research and amplifies the relatively recently developed concept that the axonal growth cone is equipped with proteins capable of performing a highly diverse range of functions. PMID:22384089

  12. Surface growth of a motile bacterial population resembles growth in a chemostat.

    PubMed

    Koster, Daniel A; Mayo, Avraham; Bren, Anat; Alon, Uri

    2012-12-07

    The growth behavior in well-mixed bacterial cultures is relatively well understood. However, bacteria often grow in heterogeneous conditions on surfaces where their growth is dependent on spatial position, especially in the case of motile populations. For such populations, the relation between growth, motility and spatial position is unclear. We developed a microscope-based assay for quantifying in situ growth and gene expression in space and time, and we observe these parameters in populations of Escherichia coli swimming in galactose soft agar plates. We find that the bacterial density and the shape of the motile population, after an initial transient, are constant in time. By considering not only the advancing population but also the fraction that lags behind, we propose a growth model that relates spatial distribution, motility and growth rate. This model, that is similar to bacterial growth in a chemostat predicts that the fraction of the population lagging behind is inversely proportional to the velocity of the motile population. We test this prediction by modulating motility using inducible expression of the flagellar sigma factor FliA. Finally, we observe that bacteria in the chemotactic ring express higher relative levels of the chemotaxis and galactose metabolism genes fliC, fliL and galE than those that stay behind in the center of the plate. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Regulation of neuronal growth cone filopodia by nitric oxide.

    PubMed

    Van Wagenen, S; Rehder, V

    1999-05-01

    Nitric oxide (NO) has been proposed to play an important role during neuronal development. Since many of its effects occur during the time of growth cone pathfinding and target interaction, we here test the hypothesis that part of NO's effects might be exerted at the growth cone. We found that low concentrations of the NO-donors DEA/NO, SIN-1, and SNP caused a rapid and transient elongation of filopodia as well as a reduction in filopodial number. These effects resulted from distinct changes in filopodial extension and retraction rates. Our novel findings suggest that NO could play a physiological role by temporarily changing a growth cone's morphology and switching its behavior from a close-range to a long-range exploratory mode. We subsequently dissected the pathway by which NO acted on growth cones. The effect of NO donors on filopodial length could be blocked by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of soluble guanylyl cyclase (sGC), indicating that NO acted via sGC. Supporting this idea, injection of cyclic GMP (cGMP) mimicked the effect of NO donors on growth cone filopodia. Moreover, application of NO-donors as well as injection of cGMP elicited a rapid and transient rise in intracellular calcium in growth cones, indicating that NO acted via cGMP to elevate calcium. This calcium rise, as well as the morphological effects of SIN-1 on filopodia, were blocked by preventing calcium entry. Given the role of filopodia in axonal guidance, our new data suggest that NO could function at the neuronal growth cone as an intracellular and/or intercellular signaling molecule by affecting steering decisions during neuronal pathfinding.

  14. Src and cortactin promote lamellipodia protrusion and filopodia formation and stability in growth cones

    PubMed Central

    He, Yingpei; Ren, Yuan; Wu, Bingbing; Decourt, Boris; Lee, Aih Cheun; Taylor, Aaron; Suter, Daniel M.

    2015-01-01

    Src tyrosine kinases have been implicated in axonal growth and guidance; however, the underlying cellular mechanisms are not well understood. Specifically, it is unclear which aspects of actin organization and dynamics are regulated by Src in neuronal growth cones. Here, we investigated the function of Src2 and one of its substrates, cortactin, in lamellipodia and filopodia of Aplysia growth cones. We found that up-regulation of Src2 activation state or cortactin increased lamellipodial length, protrusion time, and actin network density, whereas down-regulation had opposite effects. Furthermore, Src2 or cortactin up-regulation increased filopodial density, length, and protrusion time, whereas down-regulation promoted lateral movements of filopodia. Fluorescent speckle microscopy revealed that rates of actin assembly and retrograde flow were not affected in either case. In summary, our results support a model in which Src and cortactin regulate growth cone motility by increasing actin network density and protrusion persistence of lamellipodia by controlling the state of actin-driven protrusion versus retraction. In addition, both proteins promote the formation and stability of actin bundles in filopodia. PMID:26224308

  15. Simultaneous optical measurements of cell motility and growth.

    PubMed

    Sridharan, Shamira; Mir, Mustafa; Popescu, Gabriel

    2011-10-01

    It has recently been shown that spatial light interference microscopy (SLIM) developed in our laboratory can be used to quantify the dry mass growth of single cells with femtogram sensitivity [M. Mir et al., Proc. Nat. Acad. Sci. 108, 32 (2011)]. Here we show that it is possible to measure the motility of single cells in conjunction with the dry mass measurements. Specifically the effect of poly-L-lysine substrate on the dry mass growth of Drosophila S2 cells is studied. By measuring the mean square displacement of single cells and clusters it is shown that cells that adhere better to the surface are unable to grow. Using such a technique it is possible to measure both growth and morphogenesis, two of the cornerstones of developmental biology.

  16. Ultra-short pulses to signal neuronal growth cone machinery

    NASA Astrophysics Data System (ADS)

    Mathew, Manoj; Amat-Roldan, Ivan; Andres, Rosa; Cormack, Iain G.; Artigas, David; Soriano, Eduardo; Loza-Alvarez, Pablo

    2007-02-01

    Measurable change in the sensory motor machinery of growth cones are induced by non contact femtosecond laser. The focused laser beam with an average power of 3 mW was positioned at some distance away from the closest fillopodia of cortical neurons from primary cell cultures (mice E15). By identifying a set of preliminary parameters we were able to statistically analyze the phenomenological behavior of the fillopodia and classify the effects different conditions of laser light has on the growth cone. Results show that fillopodia become significantly biased towards the focused femtosecond laser light. The same experiment performed with continuous wave (CW) produced results which were indistinguishable from the case where there is no laser light present (placebo condition) indicating no clear effects of the CW laser light on the fillopodia at a distance. These findings show the potential for ultrashort pulsed light to become a new type of pathfinding cue for neuronal growth cones.

  17. Variability and Reliabiltiy in Axon Growth Cone Navigation Decision Making

    NASA Astrophysics Data System (ADS)

    Garnelo, Marta; Ricoult, Sébastien G.; Juncker, David; Kennedy, Timothy E.; Faisal, Aldo A.

    2015-03-01

    The nervous system's wiring is a result of axon growth cones navigating through specific molecular environments during development. In order to reach their target, growth cones need to make decisions under uncertainty as they are faced with stochastic sensory information and probabilistic movements. The overall system therefore exhibits features of whole organisms (perception, decision making, action) in the subset of a single cell. We aim to characterise growth cone navigation in defined nano-dot guidance cue environments, by using the tools of computational neuroscience to conduct ``molecular psychophysics.'' We start with a generative model of growth cone behaviour and we 1. characterise sensory and internal sources of noise contributing to behavioural variables, by combining knowledge of the underlying stochastic dynamics in cue sensing and the growth of the cytoskeleton. This enables us to 2. produce bottom-up lower limit estimates of behavioural response reliability and visualise it as probability distributions over axon growth trajectories. Given this information we can match our in silico model's ``psychometric'' decision curves with empirical data. Finally we use a Monte-Carlo approach to predict response distributions of axon trajectories from our model.

  18. Filopodial dynamics and growth cone stabilization in Drosophila visual circuit development.

    PubMed

    Özel, Mehmet Neset; Langen, Marion; Hassan, Bassem A; Hiesinger, P Robin

    2015-10-29

    Filopodial dynamics are thought to control growth cone guidance, but the types and roles of growth cone dynamics underlying neural circuit assembly in a living brain are largely unknown. To address this issue, we have developed long-term, continuous, fast and high-resolution imaging of growth cone dynamics from axon growth to synapse formation in cultured Drosophila brains. Using R7 photoreceptor neurons as a model we show that >90% of the growth cone filopodia exhibit fast, stochastic dynamics that persist despite ongoing stepwise layer formation. Correspondingly, R7 growth cones stabilize early and change their final position by passive dislocation. N-Cadherin controls both fast filopodial dynamics and growth cone stabilization. Surprisingly, loss of N-Cadherin causes no primary targeting defects, but destabilizes R7 growth cones to jump between correct and incorrect layers. Hence, growth cone dynamics can influence wiring specificity without a direct role in target recognition and implement simple rules during circuit assembly.

  19. Local translation of RhoA regulates growth cone collapse

    PubMed Central

    Cox, Llewellyn J.; Macosko, Evan Z.; Jeromin, Andreas; Urquhart, Erica R.; Jaffrey, Samie R.

    2005-01-01

    Neuronal development requires highly coordinated regulation of the cytoskeleton within the developing axon. This dynamic regulation manifests itself in axonal branching, turning, and pathfinding, presynaptic differentiation, and growth cone collapse and extension. Semaphorin 3A (Sema3A), a secreted guidance cue that primarily acts to repel axons from inappropriate targets, induces cytoskeletal rearrangements that results in growth cone collapse 1. These effects require intra-axonal mRNA translation. Here we show that transcripts for RhoA, a small GTPase that regulates the actin cytoskeleton, are localized to developing axons and growth cones, and this localization is mediated by an axonal targeting element located in the RhoA 3’UTR. Sema3A induces intra-axonal translation of RhoA mRNA and this local translation of RhoA is necessary and sufficient for Sema3A-mediated growth cone collapse. These studies indicate that local RhoA translation regulates the neuronal cytoskeleton and identify a novel mechanism for the regulation of RhoA signaling. PMID:16107849

  20. Lipoprotein Uptake by Neuronal Growth Cones in Vitro

    NASA Astrophysics Data System (ADS)

    Ignatius, Michael J.; Shooter, Eric M.; Pitas, Robert E.; Mahley, Robert W.

    1987-05-01

    Macrophages that rapidly enter injured peripheral nerve synthesize and secrete large quantities of apolipoprotein E. This protein may be involved in the redistribution of lipid, including cholesterol released during degeneration, to the regenerating axons. To test this postulate, apolipoprotein E-associated lipid particles released from segments of injured rat sciatic nerve and apolipoprotein E-containing lipoproteins from plasma were used to determine whether sprouting neurites, specifically their growth cones, possessed lipoprotein receptors. Pheochromocytoma (PC12) cells, which can be stimulated to produce neurites in vitro, were used as a model system. Apolipoprotein E-containing lipid particles and lipoproteins, which had been labeled with fluorescent dye, were internalized by the neurites and their growth cones; the unmetabolized dye appeared to be localized to the lysosomes. The rapid rate of accumulation in the growth cones precludes the possibility of orthograde transport of the fluorescent particles from the PC12 cell bodies. Thus, receptor-mediated lipoprotein uptake is performed by the apolipoprotein B,E(LDL) (low density lipoprotein) receptors, and in the regenerating peripheral nerve apolipoprotein E may deliver lipids to the neurites and their growth cones for membrane biosynthesis.

  1. Effects of roundabout on growth cone dynamics, filopodial length, and growth cone morphology at the midline and throughout the neuropile.

    PubMed

    Murray, M J; Whitington, P M

    1999-09-15

    roundabout (robo) encodes an axon guidance receptor that controls midline crossing in the Drosophila CNS. In robo mutants, axons that normally project ipsilaterally can cross and recross the midline. Growth cones expressing Robo are believed to be repelled from the midline by the interaction of Robo and its ligand Slit, an extracellular protein expressed by the midline glia. To help understand the cellular basis for the midline repulsion mediated by Robo, we used time-lapse observations to compare the growth cone behavior of the ipsilaterally projecting motorneuron RP2 in robo and wild-type embyros. In wild-type embryos, filopodia can project across the midline but are quickly retracted. In robo mutants, medial filopodia can remain extended for longer periods and can develop into contralateral branches. In many cases RP2 produces both ipsilateral and contralateral branches, both of which can extend into the periphery. The growth cone also exhibits longer filopodia and more extensive branching both at the midline and throughout the neuropile. Cell injections in fixed stage 13 embryos confirmed and quantified these results for both RP2 and the interneuron pCC. The results suggest that Robo both repels growth cones at the midline and inhibits branching throughout the neuropile by promoting filopodial retraction.

  2. ETHANOL ALTERS CALCIUM SIGNALING IN AXONAL GROWTH CONES

    PubMed Central

    Mah, Stephanie J.; Fleck, Mark W.

    2011-01-01

    Calcium (Ca2+) channels are sensitive to ethanol and Ca2+ signaling is a critical regulator of axonal growth and guidance. Effects of acute and chronic exposure to ethanol (22, 43, or 87 mM) on voltage-gated Ca2+ channels (VGCCs) in whole cells, and KCl-induced Ca2+ transients in axonal growth cones, were examined using dissociated hippocampal cultures. Whole-cell patch-clamp analysis in neurons with newly-formed axons (Stage 3) revealed that rapidly inactivating, low-voltage activated (LVA) and non-inactivating, high-voltage activated (HVA) currents were both inhibited in a dose-dependent manner by acute ethanol, with relatively greater inhibition of HVA currents. When assessed by Fluo-4-AM imaging, baseline fluorescence and Ca2+ response to ethanol in Stage 3 neurons was similar compared to neurons without axons, but peak Ca2+ transient amplitudes in response to bath-applied KCl were greater in Stage 3 neurons and were decreased by acute ethanol. The amplitude of Ca2+ transients elicited specifically in axonal growth cones by focal application of KCl was also inhibited by acute exposure to moderate-to-high concentrations of ethanol (43 or 87 mM), whereas a lower concentration (22 mM) had no effect. When 43 or 87 mM ethanol was present continuously in the medium, KCl-evoked Ca2+ transient amplitudes were also reduced in growth cones. In contrast, Ca2+ transients were increased by continuous exposure to 22 mM ethanol. Visualization using a fluorescent dihydropyridine analog revealed that neurons continuously exposed to ethanol expressed increased amounts of L-type Ca2+ channels, with greater increases in axonal growth cones than cell bodies. Thus, acute ethanol reduces Ca2+ current and KCl-induced Ca2+ responses in whole cells and axonal growth cones, respectively, and chronic exposure is also generally inhibitory despite apparent up-regulation of L-type channel expression. These results are consistent with a role for altered growth cone Ca2+ signaling in abnormal

  3. Two-tiered coupling between flowing actin and immobilized N-cadherin/catenin complexes in neuronal growth cones

    PubMed Central

    Garcia, Mikael; Leduc, Cécile; Lagardère, Matthieu; Argento, Amélie; Sibarita, Jean-Baptiste; Thoumine, Olivier

    2015-01-01

    Neuronal growth cones move forward by dynamically connecting actin-based motility to substrate adhesion, but the mechanisms at the individual molecular level remain unclear. We cultured primary neurons on N-cadherin–coated micropatterned substrates, and imaged adhesion and cytoskeletal proteins at the ventral surface of growth cones using single particle tracking combined to photoactivated localization microscopy (sptPALM). We demonstrate transient interactions in the second time scale between flowing actin filaments and immobilized N-cadherin/catenin complexes, translating into a local reduction of the actin retrograde flow. Normal actin flow on micropatterns was rescued by expression of a dominant negative N-cadherin construct competing for the coupling between actin and endogenous N-cadherin. Fluorescence recovery after photobleaching (FRAP) experiments confirmed the differential kinetics of actin and N-cadherin, and further revealed a 20% actin population confined at N-cadherin micropatterns, contributing to local actin accumulation. Computer simulations with relevant kinetic parameters modeled N-cadherin and actin turnover well, validating this mechanism. Such a combination of short- and long-lived interactions between the motile actin network and spatially restricted adhesive complexes represents a two-tiered clutch mechanism likely to sustain dynamic environment sensing and provide the force necessary for growth cone migration. PMID:26038554

  4. MIG-15 and ERM-1 promote growth cone directional migration in parallel to UNC-116 and WVE-1

    PubMed Central

    Teulière, Jérôme; Gally, Christelle; Garriga, Gian; Labouesse, Michel; Georges-Labouesse, Elisabeth

    2011-01-01

    Neurons require precise targeting of their axons to form a connected network and a functional nervous system. Although many guidance receptors have been identified, much less is known about how these receptors signal to direct growth cone migration. We used Caenorhabditis elegans motoneurons to study growth cone directional migration in response to a repellent UNC-6 (netrin homolog) guidance cue. The evolutionarily conserved kinase MIG-15 [homolog of Nck-interacting kinase (NIK)] regulates motoneuron UNC-6-dependent repulsion through unknown mechanisms. Using genetics and live imaging techniques, we show that motoneuron commissural axon morphology defects in mig-15 mutants result from impaired growth cone motility and subsequent failure to migrate across longitudinal obstacles or retract extra processes. To identify new genes acting with mig-15, we screened for genetic enhancers of the mig-15 commissural phenotype and identified the ezrin/radixin/moesin ortholog ERM-1, the kinesin-1 motor UNC-116 and the actin regulator WVE-1 complex. Genetic analysis indicates that mig-15 and erm-1 act in the same genetic pathway to regulate growth cone migration and that this pathway functions in parallel to the UNC-116/WVE-1 pathway. Further, time-lapse imaging of growth cones in mutants suggests that UNC-116 might be required to stimulate protrusive activity at the leading edge, whereas MIG-15 and ERM-1 maintain low activity at the rear edge. Together, these results support a model in which the MIG-15 kinase and the UNC-116–WVE-1 complex act on opposite sides of the growth cone to promote robust directional migration. PMID:21937599

  5. MIG-15 and ERM-1 promote growth cone directional migration in parallel to UNC-116 and WVE-1.

    PubMed

    Teulière, Jérôme; Gally, Christelle; Garriga, Gian; Labouesse, Michel; Georges-Labouesse, Elisabeth

    2011-10-01

    Neurons require precise targeting of their axons to form a connected network and a functional nervous system. Although many guidance receptors have been identified, much less is known about how these receptors signal to direct growth cone migration. We used Caenorhabditis elegans motoneurons to study growth cone directional migration in response to a repellent UNC-6 (netrin homolog) guidance cue. The evolutionarily conserved kinase MIG-15 [homolog of Nck-interacting kinase (NIK)] regulates motoneuron UNC-6-dependent repulsion through unknown mechanisms. Using genetics and live imaging techniques, we show that motoneuron commissural axon morphology defects in mig-15 mutants result from impaired growth cone motility and subsequent failure to migrate across longitudinal obstacles or retract extra processes. To identify new genes acting with mig-15, we screened for genetic enhancers of the mig-15 commissural phenotype and identified the ezrin/radixin/moesin ortholog ERM-1, the kinesin-1 motor UNC-116 and the actin regulator WVE-1 complex. Genetic analysis indicates that mig-15 and erm-1 act in the same genetic pathway to regulate growth cone migration and that this pathway functions in parallel to the UNC-116/WVE-1 pathway. Further, time-lapse imaging of growth cones in mutants suggests that UNC-116 might be required to stimulate protrusive activity at the leading edge, whereas MIG-15 and ERM-1 maintain low activity at the rear edge. Together, these results support a model in which the MIG-15 kinase and the UNC-116-WVE-1 complex act on opposite sides of the growth cone to promote robust directional migration.

  6. Rac regulates vascular endothelial growth factor stimulated motility.

    PubMed

    Soga, N; Connolly, J O; Chellaiah, M; Kawamura, J; Hruska, K A

    2001-01-01

    During angiogenesis endothelial cells migrate towards a chemotactic stimulus. Understanding the mechanism of endothelial cell migration is critical to the therapeutic manipulation of angiogenesis and ultimately cancer prevention. Vascular endothelial growth factor (VEGF) is a potent chemotactic stimulus of endothelial cells during angiogenesis. The endothelial cell signal transduction pathway of VEGF represents a potential target for cancer therapy, but the mechanisms of post-receptor signal transduction including the roles of rho family GTPases in regulating the cytoskeletal effects of VEGF in endothelial cells are not understood. Here we analyze the mechanisms of cell migration in the mouse brain endothelial cell line (bEND3). Stable transfectants containing a tetracycline repressible expression vector were used to induce expression of Rac mutants. Endothelial cell haptotaxis was stimulated by constitutively active V12Rac on collagen and vitronectin coated supports, and chemotaxis was further stimulated by VEGF. Osteopontin coated supports were the most stimulatory to bEND3 haptotaxis, but VEGF was not effective in further increasing migration on osteopontin coated supports. Haptotaxis on support coated with collagen, vitronectin, and to a lesser degree osteopontin was inhibited by N17 Rac. N17 Rac expression blocked stimulation of endothelial cell chemotaxis by VEGF. As part of the chemotactic stimulation, VEGF caused a loss of actin organization at areas of cell-cell contact and increased stress fiber expression in endothelial cells which were directed towards pores in the transwell membrane. N17 Rac prevented the stimulation of cell-cell contact disruption and the stress fiber stimulation by VEGF. These data demonstrate two pathways of regulating endothelial cell motility, one in which Rac is activated by matrix/integrin stimulation and is a crucial modulator of endothelial cell haptotaxis. The other pathway, in the presence of osteopontin, is Rac independent

  7. Src family kinases differentially influence glioma growth and motility.

    PubMed

    Lewis-Tuffin, Laura J; Feathers, Ryan; Hari, Priya; Durand, Nisha; Li, Zhimin; Rodriguez, Fausto J; Bakken, Katie; Carlson, Brett; Schroeder, Mark; Sarkaria, Jann N; Anastasiadis, Panos Z

    2015-11-01

    Src-family kinase (SFK) signaling impacts multiple tumor-related properties, particularly in the context of the brain tumor glioblastoma. Consequently, the pan-SFK inhibitor dasatinib has emerged as a therapeutic strategy, despite physiologic limitations to its effectiveness in the brain. We investigated the importance of individual SFKs (Src, Fyn, Yes, and Lyn) to glioma tumor biology by knocking down individual SFK expression both in culture (LN229, SF767, GBM8) and orthotopic xenograft (GBM8) contexts. We evaluated the effects of these knockdowns on tumor cell proliferation, migration, and motility-related signaling in culture, as well as overall survival in the orthotopic xenograft model. The four SFKs differed significantly in their importance to these properties. In culture, Src, Fyn, and Yes knockdown generally reduced growth and migration and altered motility-related phosphorylation patterns while Lyn knockdown did so to a lesser extent. However the details of these effects varied significantly depending on the cell line: in no case were conclusions about the role of a particular SFK applicable to all of the measures or all of the cell types examined. In the orthotopic xenograft model, mice implanted with non-target or Src or Fyn knockdown cells showed no differences in survival. In contrast, mice implanted with Yes knockdown cells had longer survival, associated with reduced tumor cell proliferation. Those implanted with Lyn knockdown cells had shorter survival, associated with higher overall tumor burden. Together, our results suggest that Yes signaling directly affects tumor cell biology in a pro-tumorigenic manner, while Lyn signaling affects interactions between tumor cells and the microenvironment in an anti-tumor manner. In the context of therapeutic targeting of SFKs, these results suggest that pan-SFK inhibitors may not produce the intended therapeutic benefit when Lyn is present. Copyright © 2015 Federation of European Biochemical Societies

  8. Protein Kinase C Activation Promotes Microtubule Advance in Neuronal Growth Cones by Increasing Average Microtubule Growth Lifetimes

    PubMed Central

    Kabir, Nurul; Schaefer, Andrew W.; Nakhost, Arash; Sossin, Wayne S.; Forscher, Paul

    2001-01-01

    We describe a novel mechanism for protein kinase C regulation of axonal microtubule invasion of growth cones. Activation of PKC by phorbol esters resulted in a rapid, robust advance of distal microtubules (MTs) into the F-actin rich peripheral domain of growth cones, where they are normally excluded. In contrast, inhibition of PKC activity by bisindolylmaleimide and related compounds had no perceptible effect on growth cone motility, but completely blocked phorbol ester effects. Significantly, MT advance occurred despite continued retrograde F-actin flow—a process that normally inhibits MT advance. Polymer assembly was necessary for PKC-mediated MT advance since it was highly sensitive to a range of antagonists at concentrations that specifically interfere with microtubule dynamics. Biochemical evidence is presented that PKC activation promotes formation of a highly dynamic MT pool. Direct assessment of microtubule dynamics and translocation using the fluorescent speckle microscopy microtubule marking technique indicates PKC activation results in a nearly twofold increase in the typical lifetime of a MT growth episode, accompanied by a 1.7-fold increase and twofold decrease in rescue and catastrophe frequencies, respectively. No significant effects on instantaneous microtubule growth, shortening, or sliding rates (in either anterograde or retrograde directions) were observed. MTs also spent a greater percentage of time undergoing retrograde transport after PKC activation, despite overall MT advance. These results suggest that regulation of MT assembly by PKC may be an important factor in determining neurite outgrowth and regrowth rates and may play a role in other cellular processes dependent on directed MT advance. PMID:11238458

  9. A pioneering growth cone in the embryonic zebrafish brain.

    PubMed Central

    Wilson, S W; Easter, S S

    1991-01-01

    During development of the nervous system, growth cones navigate very precisely to their appropriate, often distant, targets. In insects, the task of establishing the earliest pathways is accomplished by a small number of neurons, termed pioneers. These neurons have axons that lay down an early scaffold, which provides a substrate for many later-developing axons. Here we show that a similar type of cell exists in the embryonic vertebrate brain. Using light- and electron-microscopic techniques we have examined the formation of one of the earliest tracts in the zebrafish brain. We find that it is pioneered at a precise time by the growth cone of a single neuron present in a predictable location. These observations show a fundamental similarity in the establishment of axonal pathways in the central nervous systems of both invertebrates and vertebrates. Images PMID:2006169

  10. Calmodulin disruption impacts growth and motility in juvenile liver fluke.

    PubMed

    McCammick, Erin M; McVeigh, Paul; McCusker, Paul; Timson, David J; Morphew, Russell M; Brophy, Peter M; Marks, Nikki J; Mousley, Angela; Maule, Aaron G

    2016-01-27

    Deficiencies in effective flukicide options and growing issues with drug resistance make current strategies for liver fluke control unsustainable, thereby promoting the need to identify and validate new control targets in Fasciola spp. parasites. Calmodulins (CaMs) are small calcium-sensing proteins with ubiquitous expression in all eukaryotic organisms and generally use fluctuations in intracellular calcium levels to modulate cell signalling events. CaMs are essential for fundamental processes including the phosphorylation of protein kinases, gene transcription, calcium transport and smooth muscle contraction. In the blood fluke Schistosoma mansoni, calmodulins have been implicated in egg hatching, miracidial transformation and larval development. Previously, CaMs have been identified amongst liver fluke excretory-secretory products and three CaM-like proteins have been characterised biochemically from adult Fasciola hepatica, although their functions remain unknown. In this study, we set out to investigate the biological function and control target potential of F. hepatica CaMs (FhCaMs) using RNAi methodology alongside novel in vitro bioassays. Our results reveal that: (i) FhCaMs are widely expressed in parenchymal cells throughout the forebody region of juvenile fluke; (ii) significant transcriptional knockdown of FhCaM1-3 was inducible by exposure to either long (~200 nt) double stranded (ds) RNAs or 27 nt short interfering (si) RNAs, although siRNAs were less effective than long dsRNAs; (iii) transient long dsRNA exposure-induced RNA interference (RNAi) of FhCaMs triggered transcript knockdown that persisted for ≥ 21 days, and led to detectable suppression of FhCaM proteins; (iv) FhCaM RNAi significantly reduced the growth of juvenile flukes maintained in vitro; (v) FhCaM RNAi juveniles also displayed hyperactivity encompassing significantly increased migration; (vi) both the reduced growth and increased motility phenotypes were recapitulated in juvenile

  11. Frizzled receptors in neurons: from growth cones to the synapse.

    PubMed

    Varela-Nallar, Lorena; Ramirez, Valerie T; Gonzalez-Billault, Christian; Inestrosa, Nibaldo C

    2012-07-01

    The Wnt signaling pathway has been implicated in several different aspects of neural development and function, including dendrite morphogenesis, axonal growth and guidance, synaptogenesis and synaptic plasticity. Here, we studied several Frizzled Wnt receptors and determined their differential expression during hippocampal development. In cultured hippocampal neurons, the cellular distributions of Frizzleds vary greatly, some of them being localized at neurites, growth cones or synaptic sites. These findings suggest that the Wnt signaling pathway might be temporally and spatially fine tuned during the development of neuronal circuits through specific Frizzled receptors. Copyright © 2012 Wiley Periodicals, Inc.

  12. Growth of multicrystalline silicon in a cone-shaped crucible

    NASA Astrophysics Data System (ADS)

    Schmid, E.; Poklad, A.; Heinze, V.; Meier, D.; Pätzold, O.; Stelter, M.

    2015-04-01

    In this paper, a novel, vertical Bridgman-type technique for growing multicrystalline silicon (mc-Si) ingots in an induction furnace is described. In contrast to conventional growth, a modified setup with a cone-shaped crucible and susceptor is used for the first time. The temperature field and melt flow in the modified setup are calculated numerically and compared with the situation in a cylindrical standard setup. A cone-shaped mc-Si ingot is presented and analyzed with focus on the microstructure (inclusions, dislocations, grains) and the minority carrier lifetime, which are compared with the properties of a cylindrical ingot grown under similar conditions. Results of numerical simulations and growth experiments are discussed with respect to the influence of the cone-shaped setup on the temperature and flow fields in the melt, as well as on the microstructure and the minority carrier lifetime in the crystal. They indicate the potential of the novel technology to produce mc-Si ingots with a globular grain structure, low dislocation density, and high carrier lifetime.

  13. Retrograde degeneration of neurite membrane structural integrity of nerve growth cones following in vitro exposure to mercury.

    PubMed

    Leong, C C; Syed, N I; Lorscheider, F L

    2001-03-26

    Inhalation of mercury vapor (Hg0) inhibits binding of GTP to rat brain tubulin, thereby inhibiting tubulin polymerization into microtubules. A similar molecular lesion has also been observed in 80% of brains from patients with Alzheimer disease (AD) compared to age-matched controls. However the precise site and mode of action of Hg ions remain illusive. Therefore, the present study examined whether Hg ions could affect membrane dynamics of neurite growth cone morphology and behavior. Since tubulin is a highly conserved cytoskeletal protein in both vertebrates and invertebrates, we hypothesized that growth cones from animal species could be highly susceptible to Hg ions. To test this possibility, the identified, large Pedal A (PeA) neurons from the central ring ganglia of the snail Lymnoea stagnalis were cultured for 48 h in 2 ml brain conditioned medium (CM). Following neurite outgrowth, metal chloride solution (2 microl) of Hg, Al, Pb, Cd, or Mn (10(-7) M) was pressure applied directly onto individual growth cones. Time-lapse images with inverted microscopy were acquired prior to, during, and after the metal ion exposure. We demonstrate that Hg ions markedly disrupted membrane structure and linear growth rates of imaged neurites in 77% of all nerve growth cones. When growth cones were stained with antibodies specific for both tubulin and actin, it was the tubulin/microtubule structure that disintegrated following Hg exposure. Moreover, some denuded neurites were also observed to form neurofibrillary aggregates. In contrast, growth cone exposure to other metal ions did not effect growth cone morphology, nor was their motility rate compromised. To determine the growth suppressive effects of Hg ions on neuronal sprouting, cells were cultured either in the presence or absence of Hg ions. We found that in the presence of Hg ions, neuronal somata failed to sprout, whereas other metalic ions did not effect growth patterns of cultured PeA cells. We conclude that this

  14. Correlating single cell motility with population growth dynamics for flagellated bacteria.

    PubMed

    Arora, Sucheta; Bhat, Vidya; Mittal, Aditya

    2007-08-15

    Many bacteria used for biotechnological applications are naturally motile. Their "bio-nanopropeller" driven movement allows searching for better environments in a process called chemotaxis. Since bacteria are extremely small in size compared to the bulk fluid volumes in bioreactors, single cell motility is not considered to influence bioreactor operations. However, with increasing interest in localized fluid flow inside reactors, it is important to ask whether individual motility characteristics of bacteria are important in bioreactor operations. The first step in this direction is to try to correlate single cell measurements with population data of motile bacteria in a bioreactor. Thus, we observed the motility behavior of individual bacterial cells, using video microscopy with 33 ms time resolution, as a function of population growth dynamics of batch cultures in shake flasks. While observing the motility behavior of the most intensively studied bacteria, Escherichia coli, we find that overall bacterial motility decreases with progression of the growth curve. Remarkably, this is due to a decrease in a specific motility behavior called "running". Our results not only have direct implications on biofilm formations, but also provide a new direction in bioprocess design research highlighting the role of individual bacterial cell motility as an important parameter.

  15. Growth cones stall and collapse during axon outgrowth in Caenorhabditis elegans.

    PubMed

    Knobel, K M; Jorgensen, E M; Bastiani, M J

    1999-10-01

    During nervous system development, neurons form synaptic contacts with distant target cells. These connections are formed by the extension of axonal processes along predetermined pathways. Axon outgrowth is directed by growth cones located at the tips of these neuronal processes. Although the behavior of growth cones has been well-characterized in vitro, it is difficult to observe growth cones in vivo. We have observed motor neuron growth cones migrating in living Caenorhabditis elegans larvae using time-lapse confocal microscopy. Specifically, we observed the VD motor neurons extend axons from the ventral to dorsal nerve cord during the L2 stage. The growth cones of these neurons are round and migrate rapidly across the epidermis if they are unobstructed. When they contact axons of the lateral nerve fascicles, growth cones stall and spread out along the fascicle to form anvil-shaped structures. After pausing for a few minutes, they extend lamellipodia beyond the fascicle and resume migration toward the dorsal nerve cord. Growth cones stall again when they contact the body wall muscles. These muscles are tightly attached to the epidermis by narrowly spaced circumferential attachment structures. Stalled growth cones extend fingers dorsally between these hypodermal attachment structures. When a single finger has projected through the body wall muscle quadrant, the growth cone located on the ventral side of the muscle collapses and a new growth cone forms at the dorsal tip of the predominating finger. Thus, we observe that complete growth cone collapse occurs in vivo and not just in culture assays. In contrast to studies indicating that collapse occurs upon contact with repulsive substrata, collapse of the VD growth cones may result from an intrinsic signal that serves to maintain growth cone primacy and conserve cellular material.

  16. DSCR1 is required for both axonal growth cone extension and steering

    PubMed Central

    Wang, Wei; Rai, Asit; Hur, Eun-Mi; Smilansky, Zeev; Chang, Karen T.

    2016-01-01

    Local information processing in the growth cone is essential for correct wiring of the nervous system. As an axon navigates through the developing nervous system, the growth cone responds to extrinsic guidance cues by coordinating axon outgrowth with growth cone steering. It has become increasingly clear that axon extension requires proper actin polymerization dynamics, whereas growth cone steering involves local protein synthesis. However, molecular components integrating these two processes have not been identified. Here, we show that Down syndrome critical region 1 protein (DSCR1) controls axon outgrowth by modulating growth cone actin dynamics through regulation of cofilin activity (phospho/dephospho-cofilin). Additionally, DSCR1 mediates brain-derived neurotrophic factor–induced local protein synthesis and growth cone turning. Our study identifies DSCR1 as a key protein that couples axon growth and pathfinding by dually regulating actin dynamics and local protein synthesis. PMID:27185837

  17. The Role of Rac1 in the Growth Cone Dynamics and Force Generation of DRG Neurons

    PubMed Central

    Sayyad, Wasim A.; Fabris, Paolo; Torre, Vincent

    2016-01-01

    We used optical tweezers, video imaging, immunocytochemistry and a variety of inhibitors to analyze the role of Rac1 in the motility and force generation of lamellipodia and filopodia from developing growth cones of isolated Dorsal Root Ganglia neurons. When the activity of Rac1 was inhibited by the drug EHop-016, the period of lamellipodia protrusion/retraction cycles increased and the lamellipodia retrograde flow rate decreased; moreover, the axial force exerted by lamellipodia was reduced dramatically. Inhibition of Arp2/3 by a moderate amount of the drug CK-548 caused a transient retraction of lamellipodia followed by a complete recovery of their usual motility. This recovery was abolished by the concomitant inhibition of Rac1. The filopodia length increased upon inhibition of both Rac1 and Arp2/3, but the speed of filopodia protrusion increased when Rac1 was inhibited and decreased instead when Arp2/3 was inhibited. These results suggest that Rac1 acts as a switch that activates upon inhibition of Arp2/3. Rac1 also controls the filopodia dynamics necessary to explore the environment. PMID:26766136

  18. NCS-1 differentially regulates growth cone and somata calcium channels in Lymnaea neurons.

    PubMed

    Hui, Kwokyin; Feng, Zhong-Ping

    2008-02-01

    Local voltage-gated calcium channels, which regulate intracellular Ca2+ levels by allowing Ca2+ influx, play an important role in guiding and shaping growth cones, and in regulating the outgrowth and branching of neurites. Therefore, elucidating the mechanisms that regulate the biophysical properties of whole-cell calcium currents in the growth cones and somata of growing neurons is important to improving our understanding of neuronal development and regeneration. In this study, taking advantage of the large size of the pedal A (PeA) neurons in Lymnaea stagnalis, we compared the biophysical properties of somata and growth cone whole-cell calcium channel currents using Ba2+ and Ca2+ as current carriers. We found that somata and growth cone currents exhibit similar high-voltage activation properties. However, Ba2+ and Ca2+ currents in growth cones and somata are differentially affected by a dominant-negative peptide containing the C-terminal amino acid sequence of neuronal calcium sensor-1 (NCS-1). The peptide selectively reduces the peak and sustained components of current densities and the slope conductance in growth cones, and shifts the reversal potential of the growth cone currents to more hyperpolarized voltages. In contrast, the peptide had no significant effect on the somata calcium channels. Thus, we conclude that NCS-1 differentially modulates Ca2+ currents in the somata and growth cones of regenerating neurons, and may serve as a key regulator to facilitate the growth cone calcium channel activity.

  19. The Growth Cone Cytoskeleton in Axon Outgrowth and Guidance

    PubMed Central

    Dent, Erik W.; Gupton, Stephanie L.; Gertler, Frank B.

    2011-01-01

    Axon outgrowth and guidance to the proper target requires the coordination of filamentous (F)-actin and microtubules (MTs), the dynamic cytoskeletal polymers that promote shape change and locomotion. Over the past two decades, our knowledge of the many guidance cues, receptors, and downstream signaling cascades involved in neuronal outgrowth and guidance has increased dramatically. Less is known, however, about how those cascades of information converge and direct appropriate remodeling and interaction of cytoskeletal polymers, the ultimate effectors of movement and guidance. During development, much of the communication that occurs between environmental guidance cues and the cytoskeleton takes place at the growing tip of the axon, the neuronal growth cone. Several articles on this topic focus on the “input” to the growth cone, the myriad of receptor types, and their corresponding cognate ligands. Others investigate the signaling cascades initiated by receptors and propagated by second messenger pathways (i.e., kinases, phosphatases, GTPases). Ultimately, this plethora of information converges on proteins that associate directly with the actin and microtubule cytoskeletons. The role of these cytoskeletal-associated proteins, as well as the cytoskeleton itself in axon outgrowth and guidance, is the subject of this article. PMID:21106647

  20. Asynchrony in the growth and motility responses to environmental changes by individual bacterial cells

    SciTech Connect

    Umehara, Senkei; Hattori, Akihiro; Inoue, Ippei; Yasuda, Kenji . E-mail: yasuda.bmi@tmd.ac.jp

    2007-05-04

    Knowing how individual cells respond to environmental changes helps one understand phenotypic diversity in a bacterial cell population, so we simultaneously monitored the growth and motility of isolated motile Escherichia coli cells over several generations by using a method called on-chip single-cell cultivation. Starved cells quickly stopped growing but remained motile for several hours before gradually becoming immotile. When nutrients were restored the cells soon resumed their growth and proliferation but remained immotile for up to six generations. A flagella visualization assay suggested that deflagellation underlies the observed loss of motility. This set of results demonstrates that single-cell transgenerational study under well-characterized environmental conditions can provide information that will help us understand distinct functions within individual cells.

  1. Role of the actin bundling protein fascin in growth cone morphogenesis: localization in filopodia and lamellipodia.

    PubMed

    Cohan, C S; Welnhofer, E A; Zhao, L; Matsumura, F; Yamashiro, S

    2001-02-01

    Growth cones at the distal tips of growing nerve axons contain bundles of actin filaments distributed throughout the lamellipodium and that project into filopodia. The regulation of actin bundling by specific actin binding proteins is likely to play an important role in many growth cone behaviors. Although the actin binding protein, fascin, has been localized in growth cones, little information is available on its functional significance. We used the large growth cones of the snail Helisoma to determine whether fascin was involved in temporal changes in actin filaments during growth cone morphogenesis. Fascin localized to radially oriented actin bundles in lamellipodia (ribs) and filopodia. Using a fascin antibody and a GFP fascin construct, we found that fascin incorporated into actin bundles from the beginning of growth cone formation at the cut end of axons. Fascin associated with most of the actin bundle except the proximal 6--12% adjacent to the central domain, which is the region associated with actin disassembly. Later, during growth cone morphogenesis when actin ribs shortened, the proximal fascin-free zone of bundles increased, but fascin was retained in the distal, filopodial portion of bundles. Treatment with tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), which phosphorylates fascin and decreases its affinity for actin, resulted in loss of all actin bundles from growth cones. Our findings suggest that fascin may be particularly important for the linear structure and dynamics of filopodia and for lamellipodial rib dynamics by regulating filament organization in bundles.

  2. Nerve growth cone lamellipodia contain two populations of actin filaments that differ in organization and polarity

    PubMed Central

    1992-01-01

    The organization and polarity of actin filaments in neuronal growth cones was studied with negative stain and freeze-etch EM using a permeabilization protocol that caused little detectable change in morphology when cultured nerve growth cones were observed by video- enhanced differential interference contrast microscopy. The lamellipodial actin cytoskeleton was composed of two distinct subpopulations: a population of 40-100-nm-wide filament bundles radiated from the leading edge, and a second population of branching short filaments filled the volume between the dorsal and ventral membrane surfaces. Together, the two populations formed the three- dimensional structural network seen within expanding lamellipodia. Interaction of the actin filaments with the ventral membrane surface occurred along the length of the filaments via membrane associated proteins. The long bundled filament population was primarily involved in these interactions. The filament tips of either population appeared to interact with the membrane only at the leading edge; this interaction was mediated by a globular Triton-insoluble material. Actin filament polarity was determined by decoration with myosin S1 or heavy meromyosin. Previous reports have suggested that the polarity of the actin filaments in motile cells is uniform, with the barbed ends toward the leading edge. We observed that the actin filament polarity within growth cone lamellipodia is not uniform; although the predominant orientation was with the barbed end toward the leading edge (47-56%), 22-25% of the filaments had the opposite orientation with their pointed ends toward the leading edge, and 19-31% ran parallel to the leading edge. The two actin filament populations display distinct polarity profiles: the longer filaments appear to be oriented predominantly with their barbed ends toward the leading edge, whereas the short filaments appear to be randomly oriented. The different length, organization and polarity of the two filament

  3. Proteomic analysis of mouse mammary terminal end buds identifies axonal growth cone proteins.

    PubMed

    Morris, Joanna S; Davies, Claire R; Griffiths, Matthew R; Page, Martin J; Bruce, James A; Patel, Thakor; Herath, Athula; Gusterson, Barry A

    2004-06-01

    Ductal morphogenesis in the mouse mammary gland occurs mainly postnatally and is driven by specialized structures at the ends of the developing ducts, the terminal end buds (TEBs), which later regress once ductal growth is complete. To identify proteins that are specifically associated with migration of TEBs we developed a novel method of isolating TEBs, which eliminated the mammary stroma. The protein expression profile of the TEBs was then compared with that of isolates taken from the 4th inguinal mammary gland of adult virgin mice using two-dimensional (2-D) gel electrophoresis and mass spectrometry (MS) analysis (matrix-assisted laser desorption/ionization and quadrupole time of flight). Following construction of an integrated protein expression database, 44 protein features which showed differential expression levels between the two sets were chosen for MS analysis. Of these, 24 gave protein annotations whereas the other 20 produced unidentified peptides. Fourteen unequivocal proteins were identified from these 24, whereas the remaining 10 matched more than one protein within a single 2-D gel feature. Several of the identified proteins were associated with the cytoskeleton and have previously been reported in axonal growth cones, suggesting that they may influence cell shape and motility within the advancing TEBs, in a similar fashion to migrating axons.

  4. Bioconvective patterns, synchrony, and survival. [in light-limited growth model of motile algae culture

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1990-01-01

    With and without bioconvective pattern formation, a theoretical model predicts growth in light-limited cultures of motile algae. At the critical density for pattern formation, the resulting doubly exponential population curves show an inflection. Such growth corresponds quantitatively to experiments in mechanically unstirred cultures. This attaches survival value to synchronized pattern formation.

  5. Bioconvective patterns, synchrony, and survival. [in light-limited growth model of motile algae culture

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1990-01-01

    With and without bioconvective pattern formation, a theoretical model predicts growth in light-limited cultures of motile algae. At the critical density for pattern formation, the resulting doubly exponential population curves show an inflection. Such growth corresponds quantitatively to experiments in mechanically unstirred cultures. This attaches survival value to synchronized pattern formation.

  6. The phosphorylation state of neuronal processes determines growth cone formation after neuronal injury.

    PubMed

    Geddis, Matthew S; Rehder, Vincent

    2003-10-15

    Growth cones are essential for neuronal pathfinding during embryonic development and again after injury, when they aid in neuronal regeneration. This study was aimed at investigating the role of kinases in the earliest events in neuronal regeneration, namely, the formation of new growth cones from injured neuronal processes. Neurites of identified snail neurons grown in vitro were severed, and the formation of growth cones was observed from the ends of such transected processes. Under control conditions, all neurites formed a new growth cone within 45 min of transection. In contrast, growth cone formation in the presence of a general kinase inhibitor, K252a, was significantly inhibited. Moreover, decreasing the phosphorylation state of neurites by activating protein phosphatases with C2-ceramide also reduced growth cone formation. Pharmacological analysis with specific kinase inhibitors suggested that targets of protein kinase C (PKC) and tyrosine kinase (PTK) phosphorylation control growth cone formation. Inhibition of PKC with calphostin C and cerebroside completely blocked growth cone formation, whereas the inhibition of PTK with erbstatin analog significantly reduced growth cone formation. In contrast, inhibitors of protein kinase A, protein kinase G, CaM-kinase II, myosin light-chain kinase, Rho kinase, and PI-3 kinase had little or no effect 45 min after transection. These results suggest that the transformation underlying the formation of a growth cone from an injured (transected) neurite stump is highly sensitive to the phosphorylation state of key target proteins. Therefore, injury-induced signaling events will determine the outcome of neuronal regeneration through their action on kinase and phosphatase activities.

  7. Actin disruption alters the localization of tau in the growth cones of cerebellar granule neurons.

    PubMed

    Zmuda, J F; Rivas, R J

    2000-08-01

    Cultured cerebellar granule neurons initially extend a single axon, followed by the extension of a second axon to attain a bipolar morphology. Differentiation culminates with the extension of several short dendrites from the cell body. In the present study, we determined the location of the dephosphorylated form of the microtubule-associated protein tau (dtau) within the growth cones of newly forming axons and examined whether this localization was influenced by the actin cytoskeleton. Following elongation of the initial axon at 2-3 days in vitro, dtau immunoreactivity was present along the entire length of the axon, becoming most intense just proximal to the growth cone. Dtau labeling dropped off dramatically along the microtubules of the growth cone and was undetectable along the most distal tips of these microtubules. As the initial axon continued to elongate at 3-4 days in vitro, the actin-rich growth cone peripheral domain characteristically underwent a dramatic reduction in size. Dtau immunoreactivity extended all the way to the most distal tips of the microtubules in the growth cones of these cells. Cytochalasin D and latrunculin A mimicked the effects of this characteristic reduction in growth cone size with regard to dtau localization in the growth cone. Depolymerization of filamentous actin caused the collapse of the peripheral domain and allowed dtau to bind all the way to the most distal tips of microtubules in the axon. Upon removal of the drugs, the peripheral domain of the growth cone rapidly re-formed and dtau was once again excluded from the most distal regions of growth cone microtubules. These findings suggest a novel role for actin in determining the localization of the microtubule-associated protein &tgr; within the growth cones of neurons.

  8. Melanoma Proteoglycan Modifies Gene Expression to Stimulate Tumor Cell Motility, Growth and Epithelial to Mesenchymal Transition

    PubMed Central

    Yang, Jianbo; Price, Matthew A.; Li, GuiYuan; Bar-Eli, Menashe; Salgia, Ravi; Jagedeeswaran, Ramasamy; Carlson, Jennifer H.; Ferrone, Soldano; Turley, Eva A.; McCarthy, James B.

    2009-01-01

    Melanoma chondroitin sulfate proteoglycan (MCSP) is a plasma membrane-associated proteoglycan that facilitates the growth, motility and invasion of tumor cells. MCSP expression in melanoma cells enhances integrin function and constitutive activation of Erk 1,2. The current studies were performed to determine the mechanism by which MCSP expression promotes tumor growth and motility. The results demonstrate that MCSP expression in radial growth phase (RGP), vertical growth phase (VGP) or metastatic cell lines causes sustained activation of Erk 1,2, enhanced growth and motility which all require the cytoplasmic domain of the MCSP core protein. MCSP expression in an RGP cell line also promotes an epithelial to mesenchymal transition (EMT) based on changes in cell morphology and the expression of several EMT markers. Finally MCSP enhances the expression of c-Met and HGF, and inhibiting c-Met expression or activation limits the increased growth and motility of multiple melanoma cell lines. The studies collectively demonstrate an importance for MCSP in promoting progression by an epigenetic mechanism and they indicate that MCSP could be targeted to delay or inhibit tumor progression in patients. PMID:19738072

  9. Cone production, seed dispersal, germination in...old-growth redwood cut and uncut stands

    Treesearch

    Kenneth N. Boe

    1968-01-01

    Records of 5 and 6 years' cone crops in old-growth redwood (Sequoia sempervirens [D. Don Endl.] stands in northern California were studied for silvical facts. They show that (a) the principal trees in both cut and uncut stands bore fair to good cone crops for 5 consecutive years, (b) maximum seed dispersal of both total and sound seed occurred in winter, (c)...

  10. Second messengers and membrane trafficking direct and organize growth cone steering

    PubMed Central

    Tojima, Takuro; Hines, Jacob H.; Henley, John R.; Kamiguchi, Hiroyuki

    2011-01-01

    Graded distributions of extracellular cues guide developing axons toward their targets. A network of second messengers, Ca2+ and cyclic nucleotides, shapes cue-derived information into either attractive or repulsive signals that steer growth cones bidirectionally. Emerging evidence suggests that such guidance signals create a localized imbalance between exocytosis and endocytosis, which in turn redirects membrane, adhesion and cytoskeletal components asymmetrically across the growth cone to bias the direction of axon extension. These recent advances allow us to propose a unifying model of how the growth cone translates shallow gradients of environmental information into polarized activity of the steering machinery for axon guidance. PMID:21386859

  11. Mutation of Growth Arrest Specific 8 Reveals a Role in Motile Cilia Function and Human Disease

    PubMed Central

    Lewis, Wesley R.; Malarkey, Erik B.; Tritschler, Douglas; Bower, Raqual; Pasek, Raymond C.; Porath, Jonathan D.; Birket, Susan E.; Saunier, Sophie; Antignac, Corinne; Leigh, Margaret W.; Zariwala, Maimoona A.; Drummond, Iain A.; Parant, John M.; Hildebrandt, Friedhelm; Yoder, Bradley K.

    2016-01-01

    Ciliopathies are genetic disorders arising from dysfunction of microtubule-based cellular appendages called cilia. Different cilia types possess distinct stereotypic microtubule doublet arrangements with non-motile or ‘primary’ cilia having a 9+0 and motile cilia have a 9+2 array of microtubule doublets. Primary cilia are critical sensory and signaling centers needed for normal mammalian development. Defects in their structure/function result in a spectrum of clinical and developmental pathologies including abnormal neural tube and limb patterning. Altered patterning phenotypes in the limb and neural tube are due to perturbations in the hedgehog (Hh) signaling pathway. Motile cilia are important in fluid movement and defects in motility result in chronic respiratory infections, altered left-right asymmetry, and infertility. These features are the hallmarks of Primary Ciliary Dyskinesia (PCD, OMIM 244400). While mutations in several genes are associated with PCD in patients and animal models, the genetic lesion in many cases is unknown. We assessed the in vivo functions of Growth Arrest Specific 8 (GAS8). GAS8 shares strong sequence similarity with the Chlamydomonas Nexin-Dynein Regulatory Complex (NDRC) protein 4 (DRC4) where it is needed for proper flagella motility. In mammalian cells, the GAS8 protein localizes not only to the microtubule axoneme of motile cilia, but also to the base of non-motile cilia. Gas8 was recently implicated in the Hh signaling pathway as a regulator of Smoothened trafficking into the cilium. Here, we generate the first mouse with a Gas8 mutation and show that it causes severe PCD phenotypes; however, there were no overt Hh pathway phenotypes. In addition, we identified two human patients with missense variants in Gas8. Rescue experiments in Chlamydomonas revealed a subtle defect in swim velocity compared to controls. Further experiments using CRISPR/Cas9 homology driven repair (HDR) to generate one of these human missense variants

  12. 2D motility tracking of Pseudomonas putida KT2440 in growth phases using video microscopy

    PubMed Central

    Davis, Michael L.; Mounteer, Leslie C.; Stevens, Lindsey K.; Miller, Charles D.; Zhou, Anhong

    2011-01-01

    Pseudomonas putida KT2440 is a gram negative motile soil bacterium important in bioremediation and biotechnology. Thus, it is important to understand its motility characteristics as individuals and in populations. Population characteristics were determined using a modified Gompertz model. Video microscopy and imaging software were utilized to analyze two dimensional (2D) bacteria movement tracks to quantify individual bacteria behavior. It was determined that inoculum density increased the lag time as seeding densities decreased, and that the maximum specific growth rate decreased as seeding densities increased. Average bacterial velocity remained relatively similar throughout exponential growth phase (~20.9 µm/sec), while maximum velocities peak early in exponential growth phase at a velocity of 51.2 µm/sec. Pseudomonas putida KT2440 also favor smaller turn angles indicating they often continue in the same direction after a change in flagella rotation throughout the exponential growth phase. PMID:21334971

  13. Thinning and fertilizing red pine to increase growth and cone production.

    Treesearch

    John H. Cooley

    1970-01-01

    Cone production and growth were increased more by heavy thinning than by fertilizing in 53- and 55-year-old natural red pine stands growing on medium sites, and in a 20-year-old plantation on a good site.

  14. Concentration of membrane antigens by forward transport and trapping in neuronal growth cones.

    PubMed

    Sheetz, M P; Baumrind, N L; Wayne, D B; Pearlman, A L

    1990-04-20

    Formation of the nervous system requires that neuronal growth cones follow specific paths and then stop at recognition signals, sensed at the growth cone's leading edge. We used antibody-coated gold particles viewed by video-enhanced differential interference contrast microscopy to observe the distribution and movement of two cell surface molecules, N-CAM and the 2A1 antigen, on growth cones of cultured cortical neurons. Gold particles are occasionally transported forward at 1-2 microns/s to the leading edge where they are trapped but continue to move. Concentration at the edge persists after cytochalasin D treatment or ATP depletion, but active movements to and along edges cease. We also observed a novel outward movement of small cytoplasmic aggregates at 1.8 microns/s in filopodia. We suggest that active forward transport and trapping involve reversible attachment of antigens to and transport along cytoskeletal elements localized to edges of growth cones.

  15. The Ig Superfamily Cell Adhesion Molecule, apCAM, Mediates Growth Cone Steering by Substrate–Cytoskeletal Coupling

    PubMed Central

    Suter, Daniel M.; Errante, Laura D.; Belotserkovsky, Victoria; Forscher, Paul

    1998-01-01

    Dynamic cytoskeletal rearrangements are involved in neuronal growth cone motility and guidance. To investigate how cell surface receptors translate guidance cue recognition into these cytoskeletal changes, we developed a novel in vitro assay where beads, coated with antibodies to the immunoglobulin superfamily cell adhesion molecule apCAM or with purified native apCAM, replaced cellular substrates. These beads associated with retrograde F-actin flow, but in contrast to previous studies, were then physically restrained with a microneedle to simulate interactions with noncompliant cellular substrates. After a latency period of ∼10 min, we observed an abrupt increase in bead-restraining tension accompanied by direct extension of the microtubule-rich central domain toward sites of apCAM bead binding. Most importantly, we found that retrograde F-actin flow was attenuated only after restraining tension had increased and only in the bead interaction axis where preferential microtubule extension occurred. These cytoskeletal and structural changes are very similar to those reported for growth cone interactions with physiological targets. Immunolocalization using an antibody against the cytoplasmic domain of apCAM revealed accumulation of the transmembrane isoform of apCAM around bead-binding sites. Our results provide direct evidence for a mechanical continuum from apCAM bead substrates through the peripheral domain to the central cytoplasmic domain. By modulating functional linkage to the underlying actin cytoskeleton, cell surface receptors such as apCAM appear to enable the application of tensioning forces to extracellular substrates, providing a mechanism for transducing retrograde flow into guided growth cone movement. PMID:9531561

  16. Microtubule redistribution in growth cones elicited by focal inactivation of kinesin-5.

    PubMed

    Nadar, Vidya C; Lin, Shen; Baas, Peter W

    2012-04-25

    In order for growth cones to turn, microtubules from the central domain must preferentially invade the peripheral domain in the direction of the turn. Recent studies suggest that kinesin-5 (also called Eg5 or kif11) suppresses the invasion of microtubules into the peripheral domain on the side of the growth cone opposite the direction of turning. In theory, kinesin-5 could elicit these effects by acting on the microtubules within the peripheral domain itself, by acting on microtubules in the central domain, or in the transition zone between these two domains. In rat neurons expressing kinesin-5, we documented the presence of kinesin-5 in both domains of the growth cone and especially enriched in the transition zone. We then focally inactivated kinesin-5 in various regions of the growth cone, using micro-chromophore-assisted laser inactivation. We found that a greater invasion of microtubules into the peripheral domain occurred when kinesin-5 was inactivated specifically in the transition zone. However, there was no effect on microtubule invasion into the peripheral domain when kinesin-5 was inactivated in the peripheral domain itself or in the central domain. In other experiments, frog growth cones were observed to turn toward a gradient of a drug that inhibits kinesin-5, confirming that asymmetric inactivation of kinesin-5 can cause the growth cone to turn. Finally, expression of a phospho-mutant of kinesin-5 resulted in greater microtubule invasion throughout the peripheral domain and an inhibition of growth cone turning, implicating phosphorylation as a means by which kinesin-5 is regulated in the growth cone.

  17. Regulated release of serotonin from axonal growth cones isolated from the fetal rat brain.

    PubMed

    Mercado, R; Floran, B; Hernandez, J

    1998-01-01

    In the present work we propose an hypothetical model related to a molecular recognizing system for serotonin in isolated growth cone particles. This model is supported by previous results from our laboratory plus new ones which show that growth cones release serotonin tonically and such release can be stimulated by potassium in a calcium-dependent manner. The present results, together with other author's data, suggest a physiological basis for the putative role of serotonin as a trophic factor during nervous system development.

  18. Focal loss of actin bundles causes microtubule redistribution and growth cone turning.

    PubMed

    Zhou, Feng-Quan; Waterman-Storer, Clare M; Cohan, Christopher S

    2002-05-27

    It is commonly believed that growth cone turning during pathfinding is initiated by reorganization of actin filaments in response to guidance cues, which then affects microtubule structure to complete the turning process. However, a major unanswered question is how changes in actin cytoskeleton are induced by guidance cues and how these changes are then translated into microtubule rearrangement. Here, we report that local and specific disruption of actin bundles from the growth cone peripheral domain induced repulsive growth cone turning. Meanwhile, dynamic microtubules within the peripheral domain were oriented into areas where actin bundles remained and were lost from areas where actin bundles disappeared. This resulted in directional microtubule extension leading to axon bending and growth cone turning. In addition, this local actin bundle loss coincided with localized growth cone collapse, as well as asymmetrical lamellipodial protrusion. Our results provide direct evidence, for the first time, that regional actin bundle reorganization can steer the growth cone by coordinating actin reorganization with microtubule dynamics. This suggests that actin bundles can be potential targets of signaling pathways downstream of guidance cues, providing a mechanism for coupling changes in leading edge actin with microtubules at the central domain during turning.

  19. Microtubule and Cell Contact Dependency of ER-bound PTP1B Localization in Growth Cones

    PubMed Central

    Fuentes, Federico

    2009-01-01

    PTP1B is an ER-bound protein tyrosine phosphatase implied in the regulation of cell adhesion. Here we investigated mechanisms involved in the positioning and dynamics of PTP1B in axonal growth cones and evaluated the role of this enzyme in axons. In growth cones, PTP1B consistently localizes in the central domain, and occasionally at the peripheral region and filopodia. Live imaging of GFP-PTP1B reveals dynamic excursions of fingerlike processes within the peripheral region and filopodia. PTP1B and GFP-PTP1B colocalize with ER markers and coalign with microtubules at the peripheral region and redistribute to the base of the growth cone after treatment with nocodazole, a condition that is reversible. Growth cone contact with cellular targets is accompanied by invasion of PTP1B and stable microtubules in the peripheral region aligned with the contact axis. Functional impairment of PTP1B causes retardation of axon elongation, as well as reduction of growth cone filopodia lifetime and Src activity. Our results highlight the role of microtubules and cell contacts in the positioning of ER-bound PTP1B to the peripheral region of growth cones, which may be required for the positive role of PTP1B in axon elongation, filopodia stabilization, and Src activity. PMID:19158394

  20. Redistribution of GAP-43 during growth cone development in vitro; immunocytochemical studies.

    PubMed

    Burry, R W; Lah, J J; Hayes, D M

    1991-02-01

    The growth-associated protein GAP-43 (B-50, F1, pp46), has been found in elongating axons during development and regeneration, and has also been associated with synaptic plasticity in mature neurons. We have examined the loss of GAP-43 labelling from cerebellar granule cells with immunocytochemical localization of a polyclonal antibody to GAP-43. One day after plating, the plasma membrane of cell bodies, neurites and growth cones were all labelled with anti-GAP-43. By 10 days, most of the cell body labelling was lost, and by 20 days the neuritic and growth cone labelling was greatly reduced. Beginning at six days, anti-GAP-43 labelling of growth cones, which was initially uniform, became clustered. When growth cones were double-labelled with antibodies to GAP-43 and the synaptic vesicle protein, p65, inverse changes in the distribution of label was observed. While growth cone labelling with anti-p65 increased from three to 20 days in culture, GAP-43 label began to be lost from some growth cones by six days and showed continuing decline through 20 days. For individual growth cones, the loss of GAP-43 appeared to parallel the accumulation of p65, and first growth cones to lose GAP-43 appeared to be the first to accumulate p65 label. When cultures were grown on a substrate of basement membrane material, the time frames of neuritic outgrowth, loss of GAP-43 labelling, and increase in p65 labelling were all accelerated. At five days, labelling for GAP-43 was weak and labelling for p65 was strong, in a pattern comparable to that seen in older cultures on a polylysine substrate. These results suggest several conclusions concerning the expression and loss of GAP-43 in cultured cerebellar granule neurons. First, GAP-43 label is initially distributed in all parts of these cells. With increasing time in culture the label is first lost from cell bodies and later from neurites and growth cones. Second, the loss of GAP-43 label from growth cones is correlated with the appearance

  1. Acetylcholine elongates neuronal growth cone filopodia via activation of nicotinic acetylcholine receptors.

    PubMed

    Zhong, Lei Ray; Estes, Stephen; Artinian, Liana; Rehder, Vincent

    2013-07-01

    In addition to acting as a classical neurotransmitter in synaptic transmission, acetylcholine (ACh) has been shown to play a role in axonal growth and growth cone guidance. What is not well understood is how ACh acts on growth cones to affect growth cone filopodia, structures known to be important for neuronal pathfinding. We addressed this question using an identified neuron (B5) from the buccal ganglion of the pond snail Helisoma trivolvis in cell culture. ACh treatment caused pronounced filopodial elongation within minutes, an effect that required calcium influx and resulted in the elevation of the intracellular calcium concentration ([Ca]i ). Whole-cell patch clamp recordings showed that ACh caused a reduction in input resistance, a depolarization of the membrane potential, and an increase in firing frequency in B5 neurons. These effects were mediated via the activation of nicotinic acetylcholine receptors (nAChRs), as the nAChR agonist dimethylphenylpiperazinium (DMPP) mimicked the effects of ACh on filopodial elongation, [Ca]i elevation, and changes in electrical activity. Moreover, the nAChR antagonist tubucurarine blocked all DMPP-induced effects. Lastly, ACh acted locally at the growth cone, because growth cones that were physically isolated from their parent neuron responded to ACh by filopodial elongation with a similar time course as growth cones that remained connected to their parent neuron. Our data revealed a critical role for ACh as a modulator of growth cone filopodial dynamics. ACh signaling was mediated via nAChRs and resulted in Ca influx, which, in turn, caused filopodial elongation.

  2. Growth cone morphology and spreading are regulated by a dynamin–cortactin complex at point contacts in hippocampal neurons

    PubMed Central

    Kurklinsky, Svetlana; Chen, Jing; McNiven, Mark A.

    2011-01-01

    Neuronal growth cone (GC) migration and targeting are essential processes for the formation of a neural network during embryonic development. Currently, the mechanisms that support directed motility of GCs are not fully defined. The large GTPase dynamin and an interacting actin-binding protein, cortactin, have been localized to GCs, although the function performed by this complex is unclear. We have found that cortactin and the ubiquitous form of dynamin (Dyn) 2 exhibit a striking co-localization at the base of the transition zone of advancing GCs of embryonic hippocampal neurons. Confocal and total internal reflection fluorescence microscopies demonstrate that this basal localization represents point contacts. Exogenous expression of wild-type Dyn2 and cortactin leads to large, exceptionally flat, and static GCs, whereas disrupting this complex has no such effect. We find that excessive GC spreading is induced by Dyn2 and cortactin over-expression and substantial recruitment of the point contact-associated, actin-binding protein α-actinin1 to the ventral GC membrane. The distributions of other point contact proteins such as vinculin or paxillin appear unchanged. Immunoprecipitation experiments show that both Dyn2 and cortactin reside in a complex with α-actinin1. These findings provide new insights into the role of Dyn2 and the actin cytoskeleton in GC adhesion and motility. PMID:21210813

  3. Growth cone morphology and spreading are regulated by a dynamin-cortactin complex at point contacts in hippocampal neurons.

    PubMed

    Kurklinsky, Svetlana; Chen, Jing; McNiven, Mark A

    2011-04-01

    Neuronal growth cone (GC) migration and targeting are essential processes for the formation of a neural network during embryonic development. Currently, the mechanisms that support directed motility of GCs are not fully defined. The large GTPase dynamin and an interacting actin-binding protein, cortactin, have been localized to GCs, although the function performed by this complex is unclear. We have found that cortactin and the ubiquitous form of dynamin (Dyn) 2 exhibit a striking co-localization at the base of the transition zone of advancing GCs of embryonic hippocampal neurons. Confocal and total internal reflection fluorescence microscopies demonstrate that this basal localization represents point contacts. Exogenous expression of wild-type Dyn2 and cortactin leads to large, exceptionally flat, and static GCs, whereas disrupting this complex has no such effect. We find that excessive GC spreading is induced by Dyn2 and cortactin over-expression and substantial recruitment of the point contact-associated, actin-binding protein α-actinin1 to the ventral GC membrane. The distributions of other point contact proteins such as vinculin or paxillin appear unchanged. Immunoprecipitation experiments show that both Dyn2 and cortactin reside in a complex with α-actinin1. These findings provide new insights into the role of Dyn2 and the actin cytoskeleton in GC adhesion and motility. © 2011 Mayo Clinic. Journal of Neurochemistry © 2011 International Society for Neurochemistry.

  4. Bladder cancer cell growth and motility implicate cannabinoid 2 receptor-mediated modifications of sphingolipids metabolism

    PubMed Central

    Bettiga, Arianna; Aureli, Massimo; Colciago, Giorgia; Murdica, Valentina; Moschini, Marco; Lucianò, Roberta; Canals, Daniel; Hannun, Yusuf; Hedlund, Petter; Lavorgna, Giovanni; Colombo, Renzo; Bassi, Rosaria; Samarani, Maura; Montorsi, Francesco; Salonia, Andrea; Benigni, Fabio

    2017-01-01

    The inhibitory effects demonstrated by activation of cannabinoid receptors (CB) on cancer proliferation and migration may also play critical roles in controlling bladder cancer (BC). CB expression on human normal and BC specimens was tested by immunohistochemistry. Human BC cells RT4 and RT112 were challenged with CB agonists and assessed for proliferation, apoptosis, and motility. Cellular sphingolipids (SL) constitution and metabolism were evaluated after metabolic labelling. CB1-2 were detected in BC specimens, but only CB2 was more expressed in the tumour. Both cell lines expressed similar CB2. Exposure to CB2 agonists inhibited BC growth, down-modulated Akt, induced caspase 3-activation and modified SL metabolism. Baseline SL analysis in cell lines showed differences linked to unique migratory behaviours and cytoskeletal re-arrangements. CB2 activation changed the SL composition of more aggressive RT112 cells by reducing (p < 0.01) Gb3 ganglioside (−50 ± 3%) and sphingosine 1-phosphate (S1P, −40 ± 4%), which ended up to reduction in cell motility (−46 ± 5%) with inhibition of p-SRC. CB2-selective antagonists, gene silencing and an inhibitor of SL biosynthesis partially prevented CB2 agonist-induced effects on cell viability and motility. CB2 activation led to ceramide-mediated BC cell apoptosis independently of SL constitutive composition, which instead was modulated by CB2 agonists to reduce cell motility. PMID:28191815

  5. Steering neuronal growth cones by shifting the imbalance between exocytosis and endocytosis.

    PubMed

    Tojima, Takuro; Itofusa, Rurika; Kamiguchi, Hiroyuki

    2014-05-21

    Extracellular molecular cues guide migrating growth cones along specific routes during development of axon tracts. Such processes rely on asymmetric elevation of cytosolic Ca(2+) concentrations across the growth cone that mediates its attractive or repulsive turning toward or away from the side with Ca(2+) elevation, respectively. Downstream of these Ca(2+) signals, localized activation of membrane trafficking steers the growth cone bidirectionally, with endocytosis driving repulsion and exocytosis causing attraction. However, it remains unclear how Ca(2+) can differentially regulate these opposite membrane-trafficking events. Here, we show that growth cone turning depends on localized imbalance between exocytosis and endocytosis and identify Ca(2+)-dependent signaling pathways mediating such imbalance. In embryonic chicken dorsal root ganglion neurons, repulsive Ca(2+) signals promote clathrin-mediated endocytosis through a 90 kDa splice variant of phosphatidylinositol-4-phosphate 5-kinase type-1γ (PIPKIγ90). In contrast, attractive Ca(2+) signals facilitate exocytosis but suppress endocytosis via Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and cyclin-dependent kinase 5 (Cdk5) that can inactivate PIPKIγ90. Blocking CaMKII or Cdk5 leads to balanced activation of both exocytosis and endocytosis that causes straight growth cone migration even in the presence of guidance signals, whereas experimentally perturbing the balance restores the growth cone's turning response. Remarkably, the direction of this resumed turning depends on relative activities of exocytosis and endocytosis, but not on the type of guidance signals. Our results suggest that navigating growth cones can be redirected by shifting the imbalance between exocytosis and endocytosis, highlighting the importance of membrane-trafficking imbalance for axon guidance and, possibly, for polarized cell migration in general.

  6. Fibroblast growth factor 2 (FGF2) is present in human spermatozoa and is related with sperm motility. The use of recombinant FGF2 to improve motile sperm recovery.

    PubMed

    Garbarino Azúa, D J; Saucedo, L; Giordana, S; Magri, M L; Buffone, M G; Neuspiller, F; Vazquez-Levin, M H; Marín-Briggiler, C I

    2017-09-01

    Fibroblast growth factors (FGFs) and their receptors (FGFRs) regulate several functions of somatic cells. In a previous work, we reported FGFR expression in human spermatozoa and their involvement in motility. This study aimed to evaluate the presence and localization of fibroblast growth factor 2 (FGF2) in human spermatozoa, to determine the relationship of FGF2 levels with conventional semen parameters and to assess the effect of recombinant FGF2 (rFGF2) on sperm recovery in a selection procedure. Western immunoblotting analysis using an antibody against FGF2 revealed an 18-kDa band in sperm protein extracts. The protein was immunolocalized in the sperm flagellum and acrosomal region, as well as in all germ cells. Sperm FGF2 levels, assessed by flow cytometry, showed a positive (p < 0.05) correlation with sperm concentration, motility, total sperm number and total motile cells per ejaculate. Moreover, samples with abnormal motility depicted diminished (p < 0.01) FGF2 levels compared to those with normal motility. Spermatozoa exposed to rFGF2 bound the protein, exhibited higher (p < 0.05) total and motile sperm recoveries, and increased (p < 0.01) kinematic parameters after the swim-up. Findings herein presented lead to consider sperm FGF2 level as a potential marker of sperm quality, and rFGF2 as a supplement for improving sperm recovery in selection techniques. © 2017 American Society of Andrology and European Academy of Andrology.

  7. The growth and erosion of cinder cones in Guatemala and El Salvador: Models and statistics

    NASA Astrophysics Data System (ADS)

    Bemis, Karen; Walker, Jim; Borgia, Andrea; Turrin, Brent; Neri, Marco; Swisher, Carl, III

    2011-04-01

    Morphologic data for 147 cinder cones in southern Guatemala and western El Salvador are compared with data from the San Francisco volcanic field, Arizona (USA), Cima volcanic field, California (USA), Michoácan-Guanajuato volcanic field, Mexico, and the Lamongan volcanic field, East Java. The Guatemala cones have an average height of 110 +/- 50 m, an average basal diameter of 660 +/- 230 m and an average top diameter of 180 +/- 150 m. The general morphology of these cones can be described by their average cone angle of slope (24 +/- 7), average height-to-radius ratio (0.33 +/- 0.09) and their flatness (0.24 +/- 0.18). Although the mean values for the Guatemalan cones are similar to those for other volcanic fields (e.g., San Francisco volcanic field, Arizona; Cima volcanic field, California; Michoácan-Guanajuato volcanic field, Mexico; and Lamongan volcanic field, East Java), the range of morphologies encompasses almost all of those observed worldwide for cinder cones. Three new 40Ar/ 39Ar age dates are combined with 19 previously published dates for cones in Guatemala and El Salvador. There is no indication that the morphologies of these cones have changed over the last 500-1000 ka. Furthermore, a re-analysis of published data for other volcanic fields suggests that only in the Cima volcanic field (of those studied) is there clear evidence of degradation with age. Preliminary results of a numerical model of cinder cone growth are used to show that the range of morphologies observed in the Guatemalan cinder cones could all be primary, that is, due to processes occurring at the time of eruption.

  8. A novel role for doublecortin and doublecortin-like kinase in regulating growth cone microtubules

    PubMed Central

    Jean, Daphney C.; Baas, Peter W.; Black, Mark M.

    2012-01-01

    Doublecortin (DCX) and doublecortin-like kinase (DCLK), closely related family members, are microtubule-associated proteins with overlapping functions in both neuronal migration and axonal outgrowth. In growing axons, these proteins appear to have their primary functions in the growth cone. Here, we used siRNA to deplete these proteins from cultured rat sympathetic neurons. Normally, microtubules in the growth cone exhibit a gently curved contour as they extend from the base of the cone toward its periphery. However, following depletion of DCX and DCLK, microtubules throughout the growth cone become much more curvy, with many microtubules exhibiting multiple prominent bends over relatively short distances, creating a configuration that we termed wave-like folds. Microtubules with these folds appeared as if they were buckling in response to powerful forces. Indeed, inhibition of myosin-II, which generates forces on the actin cytoskeleton to push microtubules in the growth cone back toward the axonal shaft, significantly decreases the frequency of these wave-like folds. In addition, in the absence of DCX and DCLK, the depth of microtubule invasion into filopodia is reduced compared with controls, and at a functional level, growth cone responses to substrate guidance cues are altered. Conversely, overexpression of DCX results in microtubules that are straighter than usual, suggesting that higher levels of these proteins can enable an even greater resistance to folding. These findings support a role for DCX and DCLK in enabling microtubules to overcome retrograde actin-based forces, thereby facilitating the ability of the growth cone to carry out its crucial path-finding functions. PMID:23001563

  9. A novel role for doublecortin and doublecortin-like kinase in regulating growth cone microtubules.

    PubMed

    Jean, Daphney C; Baas, Peter W; Black, Mark M

    2012-12-15

    Doublecortin (DCX) and doublecortin-like kinase (DCLK), closely related family members, are microtubule-associated proteins with overlapping functions in both neuronal migration and axonal outgrowth. In growing axons, these proteins appear to have their primary functions in the growth cone. Here, we used siRNA to deplete these proteins from cultured rat sympathetic neurons. Normally, microtubules in the growth cone exhibit a gently curved contour as they extend from the base of the cone toward its periphery. However, following depletion of DCX and DCLK, microtubules throughout the growth cone become much more curvy, with many microtubules exhibiting multiple prominent bends over relatively short distances, creating a configuration that we termed wave-like folds. Microtubules with these folds appeared as if they were buckling in response to powerful forces. Indeed, inhibition of myosin-II, which generates forces on the actin cytoskeleton to push microtubules in the growth cone back toward the axonal shaft, significantly decreases the frequency of these wave-like folds. In addition, in the absence of DCX and DCLK, the depth of microtubule invasion into filopodia is reduced compared with controls, and at a functional level, growth cone responses to substrate guidance cues are altered. Conversely, overexpression of DCX results in microtubules that are straighter than usual, suggesting that higher levels of these proteins can enable an even greater resistance to folding. These findings support a role for DCX and DCLK in enabling microtubules to overcome retrograde actin-based forces, thereby facilitating the ability of the growth cone to carry out its crucial path-finding functions.

  10. Birth order dependent growth cone segregation determines synaptic layer identity in the Drosophila visual system.

    PubMed

    Kulkarni, Abhishek; Ertekin, Deniz; Lee, Chi-Hon; Hummel, Thomas

    2016-03-17

    The precise recognition of appropriate synaptic partner neurons is a critical step during neural circuit assembly. However, little is known about the developmental context in which recognition specificity is important to establish synaptic contacts. We show that in the Drosophila visual system, sequential segregation of photoreceptor afferents, reflecting their birth order, lead to differential positioning of their growth cones in the early target region. By combining loss- and gain-of-function analyses we demonstrate that relative differences in the expression of the transcription factor Sequoia regulate R cell growth cone segregation. This initial growth cone positioning is consolidated via cell-adhesion molecule Capricious in R8 axons. Further, we show that the initial growth cone positioning determines synaptic layer selection through proximity-based axon-target interactions. Taken together, we demonstrate that birth order dependent pre-patterning of afferent growth cones is an essential pre-requisite for the identification of synaptic partner neurons during visual map formation in Drosophila.

  11. Evaluation of the effects of propylisopropylacetic acid (PIA) on neuronal growth cone morphology.

    PubMed

    Shimshoni, Jakob A; Dalton, Emma C; Watson, Peter; Boris, Yagen; Bialer, Meir; Harwood, Adrian J

    2009-03-01

    Propylisopropylacetic acid (PIA) is a constitutional isomer of valproic acid (VPA). It has previously been found to be a weak antiepileptic, but in common with mood stabilizers, causes inositol depletion and growth cone spreading, suggesting the basis of a new series of mood stabilizers. To assess this possibility, we have compared the effects of racemic (R,S)-PIA and its individual enantiomers to those of the mood stabilizers lithium (Li+), VPA and carbamazepine (CBZ). Unlike Li+ and VPA, but in common with CBZ and (R,S)-PIA, neither (R)-PIA nor (S)-PIA enantiomer induces T-cell factor (TCF)-mediated gene expression. However, as seen for other mood stabilizers, both enantiomers are potent inducers of growth cone spreading. To investigate the mechanism for these effects, we examined changes in the actin cytoskeleton following drug treatment with Li+, VPA, CBZ, (R,S)-PIA or its individual enantiomers. All exhibit a redistribution of F-actin to the growth cone periphery, a feature of spread growth cones. (R,S)-PIA has the strongest effect as it also elevates F-actin polymerization at the cell periphery. This change in the actin cytoskeleton is associated with a substantial increase in F-actin-rich protrusions on the surface of the growth cone and in its close vicinity. These results demonstrate an effect of (R,S)-PIA on the neuronal actin cytoskeleton shared in common with other mood stabilizers, and suggest a potential to induce structural changes within the CNS.

  12. Birth order dependent growth cone segregation determines synaptic layer identity in the Drosophila visual system

    PubMed Central

    Kulkarni, Abhishek; Ertekin, Deniz; Lee, Chi-Hon; Hummel, Thomas

    2016-01-01

    The precise recognition of appropriate synaptic partner neurons is a critical step during neural circuit assembly. However, little is known about the developmental context in which recognition specificity is important to establish synaptic contacts. We show that in the Drosophila visual system, sequential segregation of photoreceptor afferents, reflecting their birth order, lead to differential positioning of their growth cones in the early target region. By combining loss- and gain-of-function analyses we demonstrate that relative differences in the expression of the transcription factor Sequoia regulate R cell growth cone segregation. This initial growth cone positioning is consolidated via cell-adhesion molecule Capricious in R8 axons. Further, we show that the initial growth cone positioning determines synaptic layer selection through proximity-based axon-target interactions. Taken together, we demonstrate that birth order dependent pre-patterning of afferent growth cones is an essential pre-requisite for the identification of synaptic partner neurons during visual map formation in Drosophila. DOI: http://dx.doi.org/10.7554/eLife.13715.001 PMID:26987017

  13. The effects of collapsing factors on F-actin content and microtubule distribution of Helisoma growth cones.

    PubMed

    Torreano, Paul J; Waterman-Storer, Clare M; Cohan, Christopher S

    2005-03-01

    Growth cone collapsing factors induce growth cone collapse or repulsive growth cone turning by interacting with membrane receptors that induce alterations in the growth cone cytoskeleton. A common change induced by collapsing factors in the cytoskeleton of the peripheral domain, the thin lamellopodial area of growth cones, is a decline in the number of radially aligned F-actin bundles that form the core of filopodia. The present study examined whether ML-7, a myosin light chain kinase inhibitor, serotonin, a neurotransmitter and TPA, an activator of protein kinase C, which induce growth cone collapse of Helisoma growth cones, depolymerized or debundled F-actin. We report that these collapsing factors had different effects. ML-7 induced F-actin reorganization consistent with debundling whereas serotonin and TPA predominately depolymerized and possibly debundled F-actin. Additionally, these collapsing factors induced the formation of a dense actin-ring around the central domain, the thicker proximal area of growth cones [Zhou and Cohan, 2001: J. Cell Biol. 153:1071-1083]. The formation of the actin-ring occurred subsequent to the loss of actin bundles. The ML-7-induced actin-ring was found to inhibit microtubule extension into the P-domain. Thus, ML-7, serotonin, and TPA induce growth cone collapse associated with a decline in radially aligned F-actin bundles through at least two mechanisms involving debundling of actin filaments and/or actin depolymerization.

  14. Neurotrophins enhance electric field-directed growth cone guidance and directed nerve branching.

    PubMed

    McCaig, C D; Sangster, L; Stewart, R

    2000-03-01

    Neurotrophins play major roles in the developing nervous system in controlling neuronal differentiation, neurite outgrowth, guidance and branching, synapse formation and maturation, and neuronal survival or death. There is increasing evidence that nervous system construction takes place in the presence of dc electric fields, which fluctuate dynamically in space and time during embryonic development. These have their origins in the neural tube itself, as well as in surrounding skin and gut. Early disruption of these endogenous electric fields causes failure of the nervous system to form, or else it forms aberrantly. Nerve growth, guidance, and branching are controlled tightly during pathway construction and in vitro dc electric fields have profound effects on each of these behaviours. We have used cultured neurones to ask whether neurotrophins and dc electric fields might interact in shaping neuronal growth, given their coexistence in vivo. Electric field-directed nerve growth generally was enhanced by the simultaneous presentation of several neurotrophins to the growth cone. Under certain circumstances, more nerves turned cathodally, they turned faster, further, and in lower field strengths. Intriguingly, other combinations of dc electric field and neurotrophins (low field strength and neurotrophin 3 (NT-3) switched the direction of growth cone turning. Additionally, cathodally directed nerve growth was faster and directed branching was much more common when electric fields and neurotrophins interacted with neuronal growth cones. Given such profound changes in growth cone behaviour in vitro, neurotrophins and endogenous electric fields are likely to interact in vivo.

  15. A novel, nongenomic mechanism underlies retinoic acid-induced growth cone turning.

    PubMed

    Farrar, Nathan R; Dmetrichuk, Jennifer M; Carlone, Robert L; Spencer, Gaynor E

    2009-11-11

    The vitamin A metabolite, retinoic acid (RA), is well known for its roles in neural development and regeneration. We have previously shown that RA can induce positive growth cone turning in regenerating neurons in vitro. In this study, we address the subcellular mechanisms underlying this chemo-attractive response, using identified central neurons from the adult mollusc, Lymnaea stagnalis. We show that the RA-induced positive growth cone turning was maintained in the presence of the transcriptional inhibitor, actinomycin D. We also physically transected the neurites from the cell body and showed that isolated growth cones retain the capacity to turn toward a gradient of RA. Moreover, this attractive turning is dependent on de novo local protein synthesis and Ca(2+) influx. Most of RA's actions during neurite outgrowth and regeneration require gene transcription, although these data show for the first time in any species, that the chemotropic action of RA in guiding neurite outgrowth, involves a novel, nongenomic mechanism.

  16. Growth cone-like waves transport actin and promote axonogenesis and neurite branching

    PubMed Central

    Flynn, Kevin C.; Pak, Chi W.; Shaw, Alisa E.; Bradke, Frank; Bamburg, James R.

    2010-01-01

    Axonogenesis involves a shift from uniform delivery of materials to all neurites to preferential delivery to the putative axon, supporting its more rapid extension. Waves, growth cone-like structures that propagate down the length of neurites, were shown previously to correlate with neurite growth in dissociated cultured hippocampal neurons. Waves are similar to growth cones in their structure, composition and dynamics. Here, we report that waves form in all undifferentiated neurites, but occur more frequently in the future axon during initial neuronal polarization. Moreover, wave frequency and their impact on neurite growth are altered in neurons treated with stimuli that enhance axonogenesis. Coincident with wave arrival, growth cones enlarge and undergo a marked increase in dynamics. Through their engorgement of filopodia along the neurite shaft, waves can induce de novo neurite branching. Actin in waves maintains much of its cohesiveness during transport whereas actin in non-wave regions of the neurite rapidly diffuses as measured by live cell imaging of photoactivated GFP-actin and photoconversion of Dendra-actin. Thus, waves represent an alternative axonal transport mechanism for actin. Waves also occur in neurons in organotypic hippocampal slices where they propagate along neurites in the dentate gyrus and the CA regions and induce branching. Taken together, our results indicate that waves are physiologically relevant and contribute to axon growth and branching via the transport of actin and by increasing growth cone dynamics. PMID:19513994

  17. Using Computer Simulations to Model Scoria Cone Growth

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Mehta, R. D.

    2016-12-01

    Scoria cones form from the accumulation of scoria delivered by either bursting lava bubbles (Strombolian style eruptions) or the gas thrust of an eruption column (Hawaiian to sub-Plinian style eruption). In this study, we focus on connecting the distribution of scoria delivery to the eventual cone shape rather than the specifics of the mechanism of delivery. For simplicity, we choose to model ballistic paths, that follow the scoria from ejection from crater to landing on the surface and then avalanching down slope. The first stage corresponds to Strombolian-like bursts of the bubble. The second stage only occurs if the angle of repose is greater than 30 degrees. After this condition is met, the scoria particles grain flow downwards until a stable slope is formed. These two stages of the volcanic eruption repeat themselves in the number of phases. We hypothesize that the horizontal travel distance of the ballistic paths, and as a result the width of the volcano, is primarily dependent of the velocity of the particles bursting from the bubble in the crater. Other parameters that may affect the shape of cinder cones are air resistance on ballistic paths, ranges in particle size, ballistic ejection angles, and the total number of particles. Ejection velocity, ejection angle, particle size and air resistance control the delivery distribution of scoria; a similar distribution of scoria can be obtained by sedimentation from columns and the controlling parameters of such (gas thrust velocity, particle density, etc.) can be related to the ballistic delivery in terms of eruption energy and particle characteristics. We present a series of numerical experiments that test our hypotheses by varying different parameters one or more at a time in sets each designed to test a specific hypothesis. Volcano width increases as ejection velocity, ejection angle (measured from surface), or the total number of scoria particles increases. Ongoing investigations seek the controls on crater

  18. BMP promotes motility and represses growth of smooth muscle cells by activation of tandem Wnt pathways

    PubMed Central

    de Jesus Perez, Vinicio A.; Ali, Ziad; Alastalo, Tero-Pekka; Ikeno, Fumiaki; Sawada, Hirofumi; Lai, Ying-Ju; Kleisli, Thomas; Spiekerkoetter, Edda; Qu, Xiumei; Rubinos, Laura H.; Ashley, Euan; Amieva, Manuel; Dedhar, Shoukat

    2011-01-01

    We present a novel cell-signaling paradigm in which bone morphogenetic protein 2 (BMP-2) consecutively and interdependently activates the wingless (Wnt)–β-catenin (βC) and Wnt–planar cell polarity (PCP) signaling pathways to facilitate vascular smooth muscle motility while simultaneously suppressing growth. We show that BMP-2, in a phospho-Akt–dependent manner, induces βC transcriptional activity to produce fibronectin, which then activates integrin-linked kinase 1 (ILK-1) via α4-integrins. ILK-1 then induces the Wnt–PCP pathway by binding a proline-rich motif in disheveled (Dvl) and consequently activating RhoA-Rac1–mediated motility. Transfection of a Dvl mutant that binds βC without activating RhoA-Rac1 not only prevents BMP-2–mediated vascular smooth muscle cell motility but promotes proliferation in association with persistent βC activity. Interfering with the Dvl-dependent Wnt–PCP activation in a murine stented aortic graft injury model promotes extensive neointima formation, as shown by optical coherence tomography and histopathology. We speculate that, in response to injury, factors that subvert BMP-2–mediated tandem activation of Wnt–βC and Wnt–PCP pathways contribute to obliterative vascular disease in both the systemic and pulmonary circulations. PMID:21220513

  19. Fibroblast Growth Factor Receptors (FGFRs) in Human Sperm: Expression, Functionality and Involvement in Motility Regulation

    PubMed Central

    Saucedo, Lucía; Buffa, Gabriela N.; Rosso, Marina; Guillardoy, Tomás; Góngora, Adrian; Munuce, María J.

    2015-01-01

    Fibroblast growth factors receptors (FGFRs) have been widely characterized in somatic cells, but there is scarce evidence of their expression and function in mammalian gametes. The objective of the present study was to evaluate the expression of FGFRs in human male germ cells, to determine sperm FGFR activation by the FGF2 ligand and their participation in the regulation of sperm motility. The expression of FGFR1, 2, 3 and 4 mRNAs and proteins in human testis and localization of these receptors in germ cells of the seminiferous epithelium was demonstrated. In ejaculated sperm, FGFRs were localized to the acrosomal region and flagellum. Sperm exposure to FGF2 caused an increase in flagellar FGFR phosphorylation and activation of extracellular signal-regulated kinase (ERK) and protein kinase B (PKB or Akt) signaling pathways. Incubation with FGF2 led to a significant increase in the percentage of total and progressive sperm motility, as well as in sperm kinematics. All responses were prevented by sperm preincubation with BGJ398, a specific inhibitor of FGFR tyrosine kinase activity. In addition to confirming the expression of FGFRs in germ cells of the human testis, our study describes for the first time the presence, localization and functionality of human sperm FGFRs, and provides evidence of the beneficial effect of FGF2 upon sperm motility. PMID:25970615

  20. Fibroblast Growth Factor Receptors (FGFRs) in Human Sperm: Expression, Functionality and Involvement in Motility Regulation.

    PubMed

    Saucedo, Lucía; Buffa, Gabriela N; Rosso, Marina; Guillardoy, Tomás; Góngora, Adrian; Munuce, María J; Vazquez-Levin, Mónica H; Marín-Briggiler, Clara

    2015-01-01

    Fibroblast growth factors receptors (FGFRs) have been widely characterized in somatic cells, but there is scarce evidence of their expression and function in mammalian gametes. The objective of the present study was to evaluate the expression of FGFRs in human male germ cells, to determine sperm FGFR activation by the FGF2 ligand and their participation in the regulation of sperm motility. The expression of FGFR1, 2, 3 and 4 mRNAs and proteins in human testis and localization of these receptors in germ cells of the seminiferous epithelium was demonstrated. In ejaculated sperm, FGFRs were localized to the acrosomal region and flagellum. Sperm exposure to FGF2 caused an increase in flagellar FGFR phosphorylation and activation of extracellular signal-regulated kinase (ERK) and protein kinase B (PKB or Akt) signaling pathways. Incubation with FGF2 led to a significant increase in the percentage of total and progressive sperm motility, as well as in sperm kinematics. All responses were prevented by sperm preincubation with BGJ398, a specific inhibitor of FGFR tyrosine kinase activity. In addition to confirming the expression of FGFRs in germ cells of the human testis, our study describes for the first time the presence, localization and functionality of human sperm FGFRs, and provides evidence of the beneficial effect of FGF2 upon sperm motility.

  1. L1CAM stimulates glioma cell motility and proliferation through the fibroblast growth factor receptor.

    PubMed

    Mohanan, Vishnu; Temburni, Murali K; Kappes, John C; Galileo, Deni S

    2013-04-01

    The L1CAM cell adhesion/recognition molecule (L1, CD171) and fibroblast growth factor receptor (FGFR) both are expressed by human high-grade glioma cells, but their potential actions in controlling cell behavior have not been linked. L1 actions in cancer cells have been attributed mainly to integrin receptors, and we demonstrated previously that L1-stimulated glioma cell migration correlates with integrin expression, increased focal adhesion kinase activation and focal complex turnover. Our analyses of datasets revealed FGFR is overexpressed in glioma regardless of grade, while ADAM10 metalloprotease expression increases with glioma grade. Here, we used dominant-negative and short hairpin RNA approaches to inhibit the activation of FGFR1 and expression of L1, respectively. An L1 peptide that inhibits L1-FGFR interaction and PD173074, a chemical inhibitor of FGFR1 activity, also were used to elucidate the involvement of L1-FGFR interactions on glioma cell behavior. Time-lapse cell motility studies and flow cytometry cell cycle analyses showed that L1 operates to increase glioma cell motility and proliferation through FGFR activation. Shutdown of both L1 expression and FGFR activity in glioma cells resulted in a complete termination of cell migration in vitro. These studies show for the first time that soluble L1 ectodomain (L1LE) acts on glioma cells through FGFRs, and that FGFRs are used by glioma cells for increasing motility as well as proliferation in response to activation by L1LE ligand. Thus, effective treatment of high-grade glioma may require simultaneous targeting of L1, FGFRs, and integrin receptors, which would reduce glioma cell motility as well as proliferation.

  2. Protein synthesis dependence of growth cone collapse induced by different Nogo-A-domains.

    PubMed

    Manns, Richard; Schmandke, Andre; Schmandke, Antonio; Jareonsettasin, Prem; Cook, Geoffrey; Schwab, Martin E; Holt, Christine; Keynes, Roger

    2014-01-01

    The protein Nogo-A regulates axon growth in the developing and mature nervous system, and this is carried out by two distinct domains in the protein, Nogo-A-Δ20 and Nogo-66. The differences in the signalling pathways engaged in axon growth cones by these domains are not well characterized, and have been investigated in this study. We analyzed growth cone collapse induced by the Nogo-A domains Nogo-A-Δ20 and Nogo-66 using explanted chick dorsal root ganglion neurons growing on laminin/poly-lysine substratum. Collapse induced by purified Nogo-A-Δ20 peptide is dependent on protein synthesis whereas that induced by Nogo-66 peptide is not. Nogo-A-Δ20-induced collapse is accompanied by a protein synthesis-dependent rise in RhoA expression in the growth cone, but is unaffected by proteasomal catalytic site inhibition. Conversely Nogo-66-induced collapse is inhibited ∼ 50% by proteasomal catalytic site inhibition. Growth cone collapse induced by the Nogo-A domains Nogo-A-Δ20 and Nogo-66 is mediated by signalling pathways with distinguishable characteristics concerning their dependence on protein synthesis and proteasomal function.

  3. Functional proteomic analysis reveals the involvement of KIAA1199 in breast cancer growth, motility and invasiveness

    PubMed Central

    2014-01-01

    Background KIAA1199 is a recently identified novel gene that is up-regulated in human cancer with poor survival. Our proteomic study on signaling polarity in chemotactic cells revealed KIAA1199 as a novel protein target that may be involved in cellular chemotaxis and motility. In the present study, we examined the functional significance of KIAA1199 expression in breast cancer growth, motility and invasiveness. Methods We validated the previous microarray observation by tissue microarray immunohistochemistry using a TMA slide containing 12 breast tumor tissue cores and 12 corresponding normal tissues. We performed the shRNA-mediated knockdown of KIAA1199 in MDA-MB-231 and HS578T cells to study the role of this protein in cell proliferation, migration and apoptosis in vitro. We studied the effects of KIAA1199 knockdown in vivo in two groups of mice (n = 5). We carried out the SILAC LC-MS/MS based proteomic studies on the involvement of KIAA1199 in breast cancer. Results KIAA1199 mRNA and protein was significantly overexpressed in breast tumor specimens and cell lines as compared with non-neoplastic breast tissues from large-scale microarray and studies of breast cancer cell lines and tumors. To gain deeper insights into the novel role of KIAA1199 in breast cancer, we modulated KIAA1199 expression using shRNA-mediated knockdown in two breast cancer cell lines (MDA-MB-231 and HS578T), expressing higher levels of KIAA1199. The KIAA1199 knockdown cells showed reduced motility and cell proliferation in vitro. Moreover, when the knockdown cells were injected into the mammary fat pads of female athymic nude mice, there was a significant decrease in tumor incidence and growth. In addition, quantitative proteomic analysis revealed that knockdown of KIAA1199 in breast cancer (MDA-MB-231) cells affected a broad range of cellular functions including apoptosis, metabolism and cell motility. Conclusions Our findings indicate that KIAA1199 may play an important role in breast

  4. Tubulin Tyrosination Is Required for the Proper Organization and Pathfinding of the Growth Cone

    PubMed Central

    Marcos, Séverine; Job, Didier; Andrieux, Annie; Bloch-Gallego, Evelyne

    2009-01-01

    Background During development, neuronal growth cones integrate diffusible and contact guidance cues that are conveyed to both actin and microtubule (MT) cytoskeletons and ensure axon outgrowth and pathfinding. Although several post-translational modifications of tubulin have been identified and despite their strong conservation among species, their physiological roles during development, especially in the nervous sytem, are still poorly understood. Methodology/Findings Here, we have dissected the role of a post-translational modification of the last amino acid of the α-tubulin on axonal growth by analyzing the phenotype of precerebellar neurons in Tubulin tyrosin ligase knock-out mice (TTL−/−) through in vivo, ex vivo and in vitro analyses. TTL−/− neurons are devoid of tyrosinated tubulin. Their pathway shows defects in vivo, ex vivo, in hindbrains open-book preparations or in vitro, in a collagen matrix. Their axons still orient toward tropic cues, but they emit supernumerary branches and their growth cones are enlarged and exhibit an emission of mis-oriented filopodia. Further analysis of the TTL−/− growth cone intracellular organization also reveals that the respective localization of actin and MT filaments is disturbed, with a decrease in the distal accumulation of Myosin IIB, as well as a concomitant Rac1 over-activation in the hindbrain. Pharmacological inhibition of Rac1 over-activation in TTL−/− neurons can rescue Myosin IIB localization. Conclusions/Significance In the growth cone, we propose that tubulin tyrosination takes part in the relative arrangement of actin and MT cytoskeletons, in the regulation of small GTPases activity, and consequently, in the proper morphogenesis, organization and pathfinding of the growth cone during development. PMID:19404406

  5. Tubulin tyrosination is required for the proper organization and pathfinding of the growth cone.

    PubMed

    Marcos, Séverine; Moreau, Julie; Backer, Stéphanie; Job, Didier; Andrieux, Annie; Bloch-Gallego, Evelyne

    2009-01-01

    During development, neuronal growth cones integrate diffusible and contact guidance cues that are conveyed to both actin and microtubule (MT) cytoskeletons and ensure axon outgrowth and pathfinding. Although several post-translational modifications of tubulin have been identified and despite their strong conservation among species, their physiological roles during development, especially in the nervous sytem, are still poorly understood. Here, we have dissected the role of a post-translational modification of the last amino acid of the alpha-tubulin on axonal growth by analyzing the phenotype of precerebellar neurons in Tubulin tyrosin ligase knock-out mice (TTL(-/-)) through in vivo, ex vivo and in vitro analyses. TTL(-/-) neurons are devoid of tyrosinated tubulin. Their pathway shows defects in vivo, ex vivo, in hindbrains open-book preparations or in vitro, in a collagen matrix. Their axons still orient toward tropic cues, but they emit supernumerary branches and their growth cones are enlarged and exhibit an emission of mis-oriented filopodia. Further analysis of the TTL(-/-) growth cone intracellular organization also reveals that the respective localization of actin and MT filaments is disturbed, with a decrease in the distal accumulation of Myosin IIB, as well as a concomitant Rac1 over-activation in the hindbrain. Pharmacological inhibition of Rac1 over-activation in TTL(-/-) neurons can rescue Myosin IIB localization. In the growth cone, we propose that tubulin tyrosination takes part in the relative arrangement of actin and MT cytoskeletons, in the regulation of small GTPases activity, and consequently, in the proper morphogenesis, organization and pathfinding of the growth cone during development.

  6. Multi-phasic bi-directional chemotactic responses of the growth cone

    PubMed Central

    Naoki, Honda; Nishiyama, Makoto; Togashi, Kazunobu; Igarashi, Yasunobu; Hong, Kyonsoo; Ishii, Shin

    2016-01-01

    The nerve growth cone is bi-directionally attracted and repelled by the same cue molecules depending on the situations, while other non-neural chemotactic cells usually show uni-directional attraction or repulsion toward their specific cue molecules. However, how the growth cone differs from other non-neural cells remains unclear. Toward this question, we developed a theory for describing chemotactic response based on a mathematical model of intracellular signaling of activator and inhibitor. Our theory was first able to clarify the conditions of attraction and repulsion, which are determined by balance between activator and inhibitor, and the conditions of uni- and bi-directional responses, which are determined by dose-response profiles of activator and inhibitor to the guidance cue. With biologically realistic sigmoidal dose-responses, our model predicted tri-phasic turning response depending on intracellular Ca2+ level, which was then experimentally confirmed by growth cone turning assays and Ca2+ imaging. Furthermore, we took a reverse-engineering analysis to identify balanced regulation between CaMKII (activator) and PP1 (inhibitor) and then the model performance was validated by reproducing turning assays with inhibitions of CaMKII and PP1. Thus, our study implies that the balance between activator and inhibitor underlies the multi-phasic bi-directional turning response of the growth cone. PMID:27808115

  7. Differing Semaphorin 3A concentrations trigger distinct signaling mechanisms in growth cone collapse

    PubMed Central

    Manns, Richard P.C.; Cook, Geoffrey M.W.; Holt, Christine E.; Keynes, Roger J.

    2012-01-01

    Semaphorin-3A (Sema3A) is a major guidance cue in the developing nervous system. Previous studies have revealed a dependence of responses to Sema3A on local protein synthesis (PS) in axonal growth cones, but a recent study has called this dependence into question. To understand the basis of this discrepancy we used the growth cone collapse assay on chick dorsal root ganglion (DRG) neurons. We show that the dependence of growth cone collapse on protein synthesis varies according to Sema3A concentration, from near-total at low concentration (<100ng/ml) to minimal at high concentration (>625ng/ml). Further, we show that neuropilin-1 (NP-1) mediates both PS-dependent and PS–independent collapse. Our findings are consistent with the operation of at least two distinct Sema3A signaling pathways: one that is PS-dependent, involving mammalian target of rapamycin (mTOR), and one that is PS-independent, involving GSK-3β activation and operative at all concentrations of Sema3A examined. The results provide a plausible explanation for the discrepancy in PS-dependence reported in the literature, and indicate that different signaling pathways activated within growth cones can be modulated by changing the concentration of the same guidance cue. PMID:22723695

  8. Membrane potential shifts caused by diffusible guidance signals direct growth-cone turning.

    PubMed

    Nishiyama, Makoto; von Schimmelmann, Melanie J; Togashi, Kazunobu; Findley, William M; Hong, Kyonsoo

    2008-07-01

    Plasma membrane potentials gate the ion channel conductance that controls external signal-induced neuronal functions. We found that diffusible guidance molecules caused membrane potential shifts that resulted in repulsion or attraction of Xenopus laevis spinal neuron growth cones. The repellents Sema3A and Slit2 caused hyperpolarization, and the attractants netrin-1 and BDNF caused depolarization. Clamping the growth-cone potential at the resting state prevented Sema3A-induced repulsion; depolarizing potentials converted the repulsion to attraction, whereas hyperpolarizing potentials had no effect. Sema3A increased the intracellular concentration of guanosine 3',5'-cyclic monophosphate ([cGMP]i) by soluble guanylyl cyclase, resulting in fast onset and long-lasting hyperpolarization. Pharmacological increase of [cGMP](i) caused protein kinase G (PKG)-mediated depolarization, switching Sema3A-induced repulsion to attraction. This bimodal switch required activation of either Cl(-) or Na+ channels, which, in turn, regulated the differential intracellular Ca2+ concentration increase across the growth cone. Thus, the polarity of growth-cone potential shifts imposes either attraction or repulsion, and Sema3A achieves this through cGMP signaling.

  9. The growth cone as seen through Cajal's original histological preparations and publications.

    PubMed

    Garcia-Marin, Virginia; Garcia-Lopez, Pablo; Freire, Miguel

    2009-01-01

    During the development of the nervous system, each neuron must contact its appropriate target cell in order to establish its specific connections. More than a century ago, Ramon y Cajal discovered an amoeboid-like structure at the end of the axon of developing nerve cells. He called this structure the growth cone [cono de crecimiento] and he proposed that this structure was guided towards its target tissue by chemical substances secreted by the different cells that line its course. We have reviewed the discovery of the growth cone by Cajal using his original publications, his original scientific drawings, and by studying his histological preparations conserved at the "Instituto Cajal" (Madrid, Spain).(1) We found a very good correlation between the structure of the growth cone in the Golgi-impregnated and reduced silver-nitrate-stained material used by Cajal, and that which is revealed with present-day methods. Finally, Cajal's view of the function of the growth cone and his chemotactic hypothesis will also be considered in the light of present-day knowledge.

  10. Multi-phasic bi-directional chemotactic responses of the growth cone

    NASA Astrophysics Data System (ADS)

    Naoki, Honda; Nishiyama, Makoto; Togashi, Kazunobu; Igarashi, Yasunobu; Hong, Kyonsoo; Ishii, Shin

    2016-11-01

    The nerve growth cone is bi-directionally attracted and repelled by the same cue molecules depending on the situations, while other non-neural chemotactic cells usually show uni-directional attraction or repulsion toward their specific cue molecules. However, how the growth cone differs from other non-neural cells remains unclear. Toward this question, we developed a theory for describing chemotactic response based on a mathematical model of intracellular signaling of activator and inhibitor. Our theory was first able to clarify the conditions of attraction and repulsion, which are determined by balance between activator and inhibitor, and the conditions of uni- and bi-directional responses, which are determined by dose-response profiles of activator and inhibitor to the guidance cue. With biologically realistic sigmoidal dose-responses, our model predicted tri-phasic turning response depending on intracellular Ca2+ level, which was then experimentally confirmed by growth cone turning assays and Ca2+ imaging. Furthermore, we took a reverse-engineering analysis to identify balanced regulation between CaMKII (activator) and PP1 (inhibitor) and then the model performance was validated by reproducing turning assays with inhibitions of CaMKII and PP1. Thus, our study implies that the balance between activator and inhibitor underlies the multi-phasic bi-directional turning response of the growth cone.

  11. Identification of axon-enriched microRNAs localized to growth cones of cortical neurons.

    PubMed

    Sasaki, Yukio; Gross, Christina; Xing, Lei; Goshima, Yoshio; Bassell, Gary J

    2014-03-01

    There is increasing evidence that localized mRNAs in axons and growth cones play an important role in axon extension and pathfinding via local translation. A few studies have revealed the presence of microRNAs (miRNAs) in axons, which may control local protein synthesis during axon development. However, so far, there has been no attempt to screen for axon-enriched miRNAs and to validate their possible localization to growth cones of developing axons from neurons of the central nervous system. In this study, the localization of miRNAs in axons and growth cones in cortical neurons was examined using a "neuron ball" culture method that is suitable to prepare axonal miRNAs with high yield and purity. Axonal miRNAs prepared from the neuron ball cultures of mouse cortical neurons were analyzed by quantitative real-time RT-PCR. Among 375 miRNAs that were analyzed, 105 miRNAs were detected in axons, and six miRNAs were significantly enriched in axonal fractions when compared with cell body fractions. Fluorescence in situ hybridization revealed that two axon-enriched miRNAs, miR-181a-1* and miR-532, localized as distinct granules in distal axons and growth cones. The association of these miRNAs with the RNA-induced silencing complex further supported their function to regulate mRNA levels or translation in the brain. These results suggest a mechanism to localize specific miRNAs to distal axons and growth cones, where they could be involved in local mRNA regulation. These findings provide new insight into the presence of axonal miRNAs and motivate further analysis of their function in local protein synthesis underlying axon guidance.

  12. Regulation of neuronal growth cone filopodia by nitric oxide depends on soluble guanylyl cyclase.

    PubMed

    Van Wagenen, S; Rehder, V

    2001-02-15

    Nitric oxide has been proposed to play an important role in neuronal development. We have previously shown that growth cones from an identified neuron, B5, in the snail Helisoma trivolvis, respond to nitric oxide (NO) donors by increasing the length of their filopodia within minutes of application (Van Wagenen and Rehder, 1999). This effect was mediated through a cGMP-induced increase in [Ca2+]i and resulted in an enlargement of the growth cone's action radius, suggesting that NO could function as a signaling molecule during neuronal pathfinding. We show here that NO functions as a specific rather than a general regulator of growth cone filopodia, because another identified neuron from the same ganglion, B19, failed to respond to NO with an increase in filopodial length. We found that, contrary to B5 neurons, B19 growth cones contained little or no soluble guanylyl cyclase (sGC) immunoreactivity, presumably preventing their response to NO. This hypothesis was supported by the finding that the sGC activator YC-1 (10 microM) had no effect on B19 filopodia but induced elongation of B5 filopodia. These results indicate that the effects of NO can be quite specific, and raise the interesting possibility that neurons could selectively tune in to NO by differentially expressing the target enzyme sGC in the appropriate cellular location during critical developmental stages. In addition, our NADPH-diaphorase staining and anti-NOS immunohistochemisty suggest that growth cones of B5 neurons, but not of B19 neurons, could be a source of NO, making NO a potential intra- and transcellular messenger.

  13. L1/Laminin modulation of growth cone response to EphB triggers growth pauses and regulates the microtubule destabilizing protein SCG10.

    PubMed

    Suh, Leejee H; Oster, Stephen F; Soehrman, Sophia S; Grenningloh, Gabriele; Sretavan, David W

    2004-02-25

    During development, EphB proteins serve as axon guidance molecules for retinal ganglion cell axon pathfinding toward the optic nerve head and in midbrain targets. To better understand the mechanisms by which EphB proteins influence retinal growth cone behavior, we investigated how axon responses to EphB were modulated by laminin and L1, two guidance molecules that retinal axons encounter during in vivo pathfinding. Unlike EphB stimulation in the presence of laminin, which triggers typical growth cone collapse, growth cones co-stimulated by L1 did not respond to EphB. Moreover, EphB exposure in the presence of both laminin and L1 resulted in a novel growth cone inhibition manifested as a pause in axon elongation with maintenance of normal growth cone morphology and filopodial activity. Pauses were not associated with loss of growth cone actin but were accompanied by a redistribution of the microtubule cytoskeleton with increased numbers of microtubules extending into filopodia and to the peripheral edge of the growth cone. This phenomenon was accompanied by reduced levels of the growth cone microtubule destabilizing protein SCG10. Antibody blockade of SCG10 function in growth cones resulted in both changes in microtubule distribution and pause responses mirroring those elicited by EphB in the presence of laminin and L1. These results demonstrate that retinal growth cone responsiveness to EphB is regulated by co-impinging signals from other axon guidance molecules. Furthermore, the results are consistent with EphB-mediated axon guidance mechanisms that involve the SCG10-mediated regulation of the growth cone microtubule cytoskeleton.

  14. DNA Supercoiling Regulates the Motility of Campylobacter jejuni and Is Altered by Growth in the Presence of Chicken Mucus.

    PubMed

    Shortt, Claire; Scanlan, Eoin; Hilliard, Amber; Cotroneo, Chiara E; Bourke, Billy; Ó Cróinín, Tadhg

    2016-09-13

    Campylobacter jejuni is the leading cause of bacterial gastroenteritis in humans, but relatively little is known about the global regulation of virulence factors during infection of chickens or humans. This study identified DNA supercoiling as playing a key role in regulating motility and flagellar protein production and found that this supercoiling-controlled regulon is induced by growth in chicken mucus. A direct correlation was observed between motility and resting DNA supercoiling levels in different strains of C. jejuni, and relaxation of DNA supercoiling resulted in decreased motility. Transcriptional analysis and Western immunoblotting revealed that a reduction in motility and DNA supercoiling affected the two-component regulatory system FlgRS and was associated with reduced FlgR expression, increased FlgS expression, and aberrant expression of flagellin subunits. Electron microscopy revealed that the flagellar structure remained intact. Growth in the presence of porcine mucin resulted in increased negative supercoiling, increased motility, increased FlgR expression, and reduced FlgS expression. Finally, this supercoiling-dependent regulon was shown to be induced by growth in chicken mucus, and the level of activation was dependent on the source of the mucus from within the chicken intestinal tract. In conclusion, this study reports for the first time the key role played by DNA supercoiling in regulating motility in C. jejuni and indicates that the induction of this supercoiling-induced regulon in response to mucus from different sources could play a critical role in regulating motility in vivo Although Campylobacter jejuni is the leading cause of bacterial gastroenteritis, very little is understood about how this pathogen controls the expression of genes involved in causing disease. This study for the first time identifies DNA supercoiling as a key regulator of motility in C. jejuni, which is essential for both pathogenesis and colonization. Altering the

  15. Quantitative genetic parameters for yield, plant growth and cone chemical traits in hop (Humulus lupulus L.)

    PubMed Central

    2014-01-01

    Background Most traits targeted in the genetic improvement of hop are quantitative in nature. Improvement based on selection of these traits requires a comprehensive understanding of their inheritance. This study estimated quantitative genetic parameters for 20 traits related to three key objectives for the genetic improvement of hop: cone chemistry, cone yield and agronomic characteristics. Results Significant heritable genetic variation was identified for α-acid and β-acid, as well as their components and relative proportions. Estimates of narrow-sense heritability for these traits (h 2  = 0.15 to 0.29) were lower than those reported in previous hop studies, but were based on a broader suite of families (108 from European, North American and hybrid origins). Narrow-sense heritabilities are reported for hop growth traits for the first time (h 2  = 0.04 to 0.20), relating to important agronomic characteristics such as emergence, height and lateral morphology. Cone chemistry and growth traits were significantly genetically correlated, such that families with more vigorous vegetative growth were associated with lower α-acid and β-acid levels. This trend may reflect the underlying population structure of founder genotypes (European and North American origins) as well as past selection in the Australian environment. Although male and female hop plants are thought to be indistinguishable until flowering, sex was found to influence variation in many growth traits, with male and female plants displaying differences in vegetative morphology from emergence to cone maturity. Conclusions This study reveals important insights into the genetic control of quantitative hop traits. The information gained will provide hop breeders with a greater understanding of the additive genetic factors which affect selection of cone chemistry, yield and agronomic characteristics in hop, aiding in the future development of improved cultivars. PMID:24524684

  16. Growth, collapse, and stalling in a mechanical model for neurite motility

    NASA Astrophysics Data System (ADS)

    Recho, Pierre; Jerusalem, Antoine; Goriely, Alain

    2016-03-01

    Neurites, the long cellular protrusions that form the routes of the neuronal network, are capable of actively extending during early morphogenesis or regenerating after trauma. To perform this task, they rely on their cytoskeleton for mechanical support. In this paper, we present a three-component active gel model that describes neurites in the three robust mechanical states observed experimentally: collapsed, static, and motile. These states arise from an interplay between the physical forces driven by growth of the microtubule-rich inner core of the neurite and the acto-myosin contractility of its surrounding cortical membrane. In particular, static states appear as a mechanical traction or compression balance of these two parallel structures. The model predicts how the response of a neurite to a towing force depends on the force magnitude and recovers the response of neurites to several drug treatments that modulate the cytoskeleton active and passive properties.

  17. MiR-25 promotes gastric cancer cells growth and motility by targeting RECK.

    PubMed

    Zhao, Hongying; Wang, Yu; Yang, Liu; Jiang, Rongke; Li, Wenqing

    2014-01-01

    Gastric cancer (GC) is the second leading cause of cancer-related death worldwide. Recently, accumulating evidence suggests that microRNAs (miRNAs) play prominent roles in tumorigenesis and metastasis. Here, we confirmed that miR-25 was significantly increased in human GC tissues and cell lines. Forced expression of miR-25 remarkably enhanced cell proliferation, migration, and invasion in GC cells, whereas inhibition of miR-25 by inhibitor caused significant suppression of proliferation and significant increase of apoptosis. Moreover, inhibition of miR-25 significantly decreased migration and invasion of GC cells. Finally, reversion-inducing-cysteine-rich protein with kazal motifs (RECK) was found to be a target of miR-25. Overexpression of RECK could significantly reverse the oncogenic effect of miR-25. Taken together, miR-25 might promote GC cells growth and motility partially by targeting RECK.

  18. Piperine inhibits the growth and motility of triple-negative breast cancer cells.

    PubMed

    Greenshields, Anna L; Doucette, Carolyn D; Sutton, Kimberly M; Madera, Laurence; Annan, Henry; Yaffe, Paul B; Knickle, Allison F; Dong, Zhongmin; Hoskin, David W

    2015-02-01

    Piperine, an alkaloid from black pepper, is reported to have anticancer activities. In this study, we investigated the effect of piperine on the growth and motility of triple-negative breast cancer (TNBC) cells. Piperine inhibited the in vitro growth of TNBC cells, as well as hormone-dependent breast cancer cells, without affecting normal mammary epithelial cell growth. Exposure to piperine decreased the percentage of TNBC cells in the G2 phase of the cell cycle. In addition, G1- and G2-associated protein expression was decreased and p21(Waf1/Cip1) expression was increased in piperine-treated TNBC cells. Piperine also inhibited survival-promoting Akt activation in TNBC cells and caused caspase-dependent apoptosis via the mitochondrial pathway. Interestingly, combined treatment with piperine and γ radiation was more cytotoxic for TNBC cells than γ radiation alone. The in vitro migration of piperine-treated TNBC cells was impaired and expression of matrix metalloproteinase-2 and -9 mRNA was decreased, suggesting an antimetastatic effect by piperine. Finally, intratumoral administration of piperine inhibited the growth of TNBC xenografts in immune-deficient mice. Taken together, these findings suggest that piperine may be useful in the treatment of TNBC. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  19. Growth of a young, frequently active composite cone: Ngauruhoe volcano, New Zealand

    NASA Astrophysics Data System (ADS)

    Hobden, Barbara J.; Houghton, Bruce F.; Nairn, Ian A.

    2002-09-01

    Ngauruhoe cone, in southern Taupo Volcanic Zone, New Zealand, has grown rapidly over the last 2,500 years in an alternation of effusive, strombolian, vulcanian, and sub-plinian eruptions of andesitic magma. At times growth has been 'staccato' in fashion as evidenced in the historical record. Each historical eruption typically lasted days to months, alternating with repose periods of years to decades. Major historic eruptions occurred in 1870 1949 1954-1955 and 1973-1975, encompassing wide variations in eruptive style over short timescales. The early period of cone building appears to have been dominated by a more continuous form of activity characterised by a series of numerous frequent explosive eruptions, with associated lava flows. The 2.2-km3 cone has grown in a piecemeal sectorial manner reflecting constant modification to the morphology of the summit, which has funnelled eruption products to specific sectors of the cone. Eruption rates can be calculated on several different timescales. Discharge rates averaged over individual eruptive pulses vary by two orders of magnitude (2.7-280 m3 s-1), reflecting variations in high level magma ascent rates and processes such as degassing, which are, in turn, reflected in contrasting eruptive styles. Lower rates (e.g. 0.65 m3 s-1) are obtained by averaging the discharge over an entire eruption lasting several months and may correspond to the ascent rate of magma batch(es) feeding the eruption. The long-term growth rate of Ngauruhoe is 0.9 km3 ky-1. This is an average rate reflecting the long-term deep supply rate of magma to crustal reservoirs. By looking at eruption rates on these different timescales we are better able to constrain processes occurring at various depths within the plumbing system. There are few detailed studies of the growth patterns of young volcanic cones, but such data are essential in understanding the dynamics of andesitic systems. More than 60 lavas and pyroclastic units mapped on different sectors

  20. The growth cones of living neurons probed by the atomic force microscope.

    PubMed

    Ricci, Davide; Grattarola, Massimo; Tedesco, Mariateresa

    2011-01-01

    A detailed report of experimental findings concerning the use of atomic force microscopy to probe growth cones of chick embryo spinal cord neurons under vital conditions is given.The role played by indentation in the making of images and force-versus-distance curves is critically discussed. As a result, the thickness of growth cone regions is quantitatively estimated. By comparing the obtained images with descriptions given in the literature on the basis of other microscopy techniques, a central (C) region and a peripheral (P) region are identified, characterized by a different thickness and a different structural organization. Moreover, clusters of adhesion molecules are tentatively identified in regions where neuron arborizations were challenged by the atomic force microscope (AFM) tip.

  1. Organization of cytoskeletal elements and organelles preceding growth cone emergence from an identified neuron in situ

    PubMed Central

    1989-01-01

    The purpose of this study was to investigate the arrangement of cytoskeletal elements and organelles in an identified neuron in situ at the site of emergence of its growth cone just before and concurrent with the onset of axonogenesis. The Ti1 pioneer neurons are the first pair of afferent neurons to differentiate in embryonic grasshopper limbs. They arise at the distal tip of the limb bud epithelium, the daughter cells of a single precursor cell, the Pioneer Mother Cell (PMC). Using immunohistochemical markers, we characterized the organization of microtubules, centrosomes, Golgi apparatus, midbody, actin filaments, and chromatin from mitosis in the PMC through axonogenesis in the Tils. Just before and concurrent with the onset of axonogenesis, a characteristic arrangement of tubulin, actin filaments, and Golgi apparatus is localized at the proximal pole of the proximal pioneer neuron. The growth cone of the proximal cell stereotypically arises from this site. Although the distal cell's axon generally grows proximally, occasionally it arises from its distal pole; in such limbs, the axons from the sister cells extend from mirror symmetric locations on their somata. In the presence of cytochalasin D, the PMC undergoes nuclear division but not cytokinesis and although other neuronal phenotypes are expressed, axongenesis is inhibited. Our data suggest that intrinsic information determines the site of growth cone emergence of an identified neuron in situ. PMID:2654140

  2. Using plusTipTracker software to measure microtubule dynamics in Xenopus laevis growth cones.

    PubMed

    Stout, Alina; D'Amico, Salvatore; Enzenbacher, Tiffany; Ebbert, Patrick; Lowery, Laura Anne

    2014-09-07

    Microtubule (MT) plus-end-tracking proteins (+TIPs) localize to the growing plus-ends of MTs and regulate MT dynamics(1,2). One of the most well-known and widely-utilized +TIPs for analyzing MT dynamics is the End-Binding protein, EB1, which binds all growing MT plus-ends, and thus, is a marker for MT polymerization(1). Many studies of EB1 behavior within growth cones have used time-consuming and biased computer-assisted, hand-tracking methods to analyze individual MTs(1-3). Our approach is to quantify global parameters of MT dynamics using the software package, plusTipTracker(4), following the acquisition of high-resolution, live images of tagged EB1 in cultured embryonic growth cones(5). This software is a MATLAB-based, open-source, user-friendly package that combines automated detection, tracking, visualization, and analysis for movies of fluorescently-labeled +TIPs. Here, we present the protocol for using plusTipTracker for the analysis of fluorescently-labeled +TIP comets in cultured Xenopus laevis growth cones. However, this software can also be used to characterize MT dynamics in various cell types(6-8).

  3. Different receptors mediate the electrophysiological and growth cone responses of an identified neuron to applied dopamine.

    PubMed

    Dobson, K S; Dmetrichuk, J M; Spencer, G E

    2006-09-15

    Neurotransmitters are among the many cues that may guide developing axons toward appropriate targets in the developing nervous system. We have previously shown in the mollusk Lymnaea stagnalis that dopamine, released from an identified pre-synaptic cell, differentially affects growth cone behavior of its target and non-target cells in vitro. Here, we describe a group of non-target cells that also produce an inhibitory electrophysiological response to applied dopamine. We first determined, using pharmacological blockers, which receptors mediate this physiological response. We demonstrated that the dopaminergic electrophysiological responses of non-target cells were sensitive to a D2 receptor antagonist, as are known target cell responses. However, the non-target cell receptors were linked to different G-proteins and intracellular signaling pathways than the target cell receptors. Despite the presence of a D2-like receptor at the soma, the growth cone collapse of these non-target cells was mediated by D1-like receptors. This study shows that different dopamine receptor sub-types mediated the inhibitory physiological and growth cone responses of an identified cell type. We therefore not only provide further evidence that D2- and D1-like receptors can be present on the same neuron in invertebrates, but also show that these receptors are likely involved in very different cellular functions.

  4. Ect2, an ortholog of Drosophila Pebble, regulates formation of growth cones in primary cortical neurons

    PubMed Central

    Tsuji, Takahiro; Higashida, Chiharu; Aoki, Yoshihiko; Islam, Mohammad Saharul; Dohmoto, Mitsuko; Higashida, Haruhiro

    2016-01-01

    In collaboration with Marshall Nirenberg, we performed in vivo RNA interference (RNAi) genome-wide screening in Drosophila embryos. Pebble has been shown to be involved in Drosophila neuronal development. We have also reported that depletion of Ect2, a mammalian ortholog of Pebble, induces differentiation in NG108-15 neuronal cells. However, the precise role of Ect2 in neuronal development has yet to be studied. Here, we confirmed in PC12 pheochromocytoma cells that inhibition of Ect2 expression by RNAi stimulated neurite outgrowth, and in the mouse embryonic cortex that Ect2 was accumulated throughout the ventricular and subventricular zones with neuronal progenitor cells. Next, the effects of Ect2 depletion were studied in primary cultures of mouse embryonic cortical neurons: Loss of Ect2 did not affect the differentiation stages of neuritogenesis, the number of neurites, or axon length, while the numbers of growth cones and growth cone-like structures were increased. Taken together, our results suggest that Ect2 contributes to neuronal morphological differentiation through regulation of growth cone dynamics. PMID:22366651

  5. Ect2, an ortholog of Drosophila Pebble, regulates formation of growth cones in primary cortical neurons.

    PubMed

    Tsuji, Takahiro; Higashida, Chiharu; Aoki, Yoshihiko; Islam, Mohammad Saharul; Dohmoto, Mitsuko; Higashida, Haruhiro

    2012-11-01

    In collaboration with Marshall Nirenberg, we performed in vivo RNA interference (RNAi) genome-wide screening in Drosophila embryos. Pebble has been shown to be involved in Drosophila neuronal development. We have also reported that depletion of Ect2, a mammalian ortholog of Pebble, induces differentiation in NG108-15 neuronal cells. However, the precise role of Ect2 in neuronal development has yet to be studied. Here, we confirmed in PC12 pheochromocytoma cells that inhibition of Ect2 expression by RNAi stimulated neurite outgrowth, and in the mouse embryonic cortex that Ect2 was accumulated throughout the ventricular and subventricular zones with neuronal progenitor cells. Next, the effects of Ect2 depletion were studied in primary cultures of mouse embryonic cortical neurons: Loss of Ect2 did not affect the differentiation stages of neuritogenesis, the number of neurites, or axon length, while the numbers of growth cones and growth cone-like structures were increased. Taken together, our results suggest that Ect2 contributes to neuronal morphological differentiation through regulation of growth cone dynamics.

  6. Deiodinase knockdown during early zebrafish development affects growth, development, energy metabolism, motility and phototransduction.

    PubMed

    Bagci, Enise; Heijlen, Marjolein; Vergauwen, Lucia; Hagenaars, An; Houbrechts, Anne M; Esguerra, Camila V; Blust, Ronny; Darras, Veerle M; Knapen, Dries

    2015-01-01

    Thyroid hormone (TH) balance is essential for vertebrate development. Deiodinase type 1 (D1) and type 2 (D2) increase and deiodinase type 3 (D3) decreases local intracellular levels of T3, the most important active TH. The role of deiodinase-mediated TH effects in early vertebrate development is only partially understood. Therefore, we investigated the role of deiodinases during early development of zebrafish until 96 hours post fertilization at the level of the transcriptome (microarray), biochemistry, morphology and physiology using morpholino (MO) knockdown. Knockdown of D1+D2 (D1D2MO) and knockdown of D3 (D3MO) both resulted in transcriptional regulation of energy metabolism and (muscle) development in abdomen and tail, together with reduced growth, impaired swim bladder inflation, reduced protein content and reduced motility. The reduced growth and impaired swim bladder inflation in D1D2MO could be due to lower levels of T3 which is known to drive growth and development. The pronounced upregulation of a large number of transcripts coding for key proteins in ATP-producing pathways in D1D2MO could reflect a compensatory response to a decreased metabolic rate, also typically linked to hypothyroidism. Compared to D1D2MO, the effects were more pronounced or more frequent in D3MO, in which hyperthyroidism is expected. More specifically, increased heart rate, delayed hatching and increased carbohydrate content were observed only in D3MO. An increase of the metabolic rate, a decrease of the metabolic efficiency and a stimulation of gluconeogenesis using amino acids as substrates may have been involved in the observed reduced protein content, growth and motility in D3MO larvae. Furthermore, expression of transcripts involved in purine metabolism coupled to vision was decreased in both knockdown conditions, suggesting that both may impair vision. This study provides new insights, not only into the role of deiodinases, but also into the importance of a correct TH balance

  7. Generation of the membrane potential and its impact on the motility, ATP production and growth in Campylobacter jejuni

    USDA-ARS?s Scientific Manuscript database

    The generation of an electrical membrane potential (''), the major constituent of the proton motive force (pmf) is crucial for the ATP synthesis, bacterial growth and motility. The pmf drives the rotation of flagella and is vital for the microaerophilic human pathogen Campylobacter jejuni to coloniz...

  8. TGFβ (transforming growth factor β) and keratocyte motility in 24 h zebrafish explant cultures.

    PubMed

    Tan, Benjamin; Pascual, Agnes; de Beus, Alexander; Cooper, Kimbal; Hull, Elizabeth

    2011-11-01

    Fish keratocytes are used as a model system for the study of the mechanics of cell motility because of their characteristic rapid, smooth gliding motion, but little work has been done on the regulation of fish keratocyte movement. As TGFβ (transforming growth factor β) plays multiple roles in primary human keratinocyte cell migration, we investigated the possible involvement of TGFβ in fish keratocyte migration. Studying the involvement of TGFβ1 in 24 h keratocyte explant allows the examination of the cells before alterations in cellular physiology occur due to extended culture times. During this initial period, TGFβ levels increase 6.2-fold in SFM (serum-free medium) and 2.4-fold in SFM+2% FBS (fetal bovine serum), while TGFβ1 and TGFβRII (TGFβ receptor II) mRNA levels increase ∼3- and ∼5-fold respectively in each culture condition. Two measures of motility, cell sheet area and migration distance, vary with the amount of exogenous TGFβ1 and culture media. The addition of 100 ng/ml exogenous TGFβ1 in SFM increases both measures [3.3-fold (P = 4.5×10-5) and 26% (P = 2.1×10-2) respectively]. In contrast, 100 ng/ml of exogenous TGFβ1 in medium containing 2% FBS decreases migration distance by 2.1-fold (P = 1.7×10-7), but does not affect sheet area. TGFβ1 (10 ng/ml) has little effect on cell sheet area in SFM cultures, but leads to a 1.8-fold increase (P = 1.5×10-2) with 2% FBS. The variable response to TGFβ1 may be, at least in part, explained by the effect of 2% FBS on cell morphology, mode of motility and expression of endogenous TGFβ1 and TGFβRII. Together, these results suggest that expression of TGFβ and its receptor are up-regulated during zebrafish keratocyte explant culture and that TGFβ promotes fish keratocyte migration.

  9. A Fungal Kinesin Required for Organelle Motility, Hyphal Growth, and Morphogenesis

    PubMed Central

    Wu, Qindong; Sandrock, Tanya M.; Turgeon, B. Gillian; Yoder, Olen C.; Wirsel, Stefan G.; Aist, James R.

    1998-01-01

    A gene (NhKIN1) encoding a kinesin was cloned from Nectria haematococca genomic DNA by polymerase chain reaction amplification, using primers corresponding to conserved regions of known kinesin-encoding genes. Sequence analysis showed that NhKIN1 belongs to the subfamily of conventional kinesins and is distinct from any of the currently designated kinesin-related protein subfamilies. Deletion of NhKIN1 by transformation-mediated homologous recombination caused several dramatic phenotypes: a 50% reduction in colony growth rate, helical or wavy hyphae with reduced diameter, and subcellular abnormalities including withdrawal of mitochondria from the growing hyphal apex and reduction in the size of the Spitzenkörper, an apical aggregate of secretory vesicles. The effects on mitochondria and Spitzenkörper were not due to altered microtubule distribution, as microtubules were abundant throughout the length of hyphal tip cells of the mutant. The rate of spindle elongation during anaphase B of mitosis was reduced 11%, but the rate was not significantly different from that of wild type. This lack of a substantial mitotic phenotype is consistent with the primary role of the conventional kinesins in organelle motility rather than mitosis. Our results provide further evidence that the microtubule-based motility mechanism has a direct role in apical transport of secretory vesicles and the first evidence for its role in apical transport of mitochondria in a filamentous fungus. They also include a unique demonstration that a microtubule-based motor protein is essential for normal positioning of the Spitzenkörper, thus providing a new insight into the cellular basis for the aberrant hyphal morphology. PMID:9436993

  10. Linear growth rates of types I and II convective modes within the rotating-cone boundary layer

    NASA Astrophysics Data System (ADS)

    Garrett, S. J.

    2010-04-01

    Experimental observations have shown that the transition characteristics of the boundary-layer flow over rotating cones depends on the cone half-angle. In particular, pairs of counter-rotating Görtler-type vortices are observed over cones with slender half-angles and co-rotating vortices are observed over broad cones. Garrett et al (2009 J. Fluid Mech. 622 209-32) have hypothesized the existence of a centrifugal instability mode over slender cones that is more dangerous than the types I (crossflow) and II (streamline curvature) modes which dominate over rotating disks and broad cones. Work is currently underway to clarify this alternative mode; however, a clear understanding of the growth rates of types I and II modes is crucial to the ultimate understanding of how the dominant mode changes with half-angle. In this paper, we demonstrate that the maximum growth rate for types I and II modes decreases with reduced half-angle, which clears the way for the dominance of the alternative instability mode. Furthermore, it is suggested that vortices travelling at 75% of the cone surface speed will be selected over smooth, clean rotating cones with half-angle such that the type I mode is dominant. Interestingly, this vortex speed has been experimentally observed by Kobayashi and Arai within the rotating-sphere boundary layer.

  11. Marked stimulation of growth and motility of human keratinocytes by hepatocyte growth factor

    SciTech Connect

    Matsumoto, K.; Hashimoto, K.; Yoshikawa, K.; Nakamura, T. )

    1991-09-01

    Effect of hepatocyte growth factor (HGF) on normal human epidermal keratinocytes cultured under conditions of low Ca2+ (0.1 mM, growth-promoting condition) and physiological Ca2+ (1.8 mM, differentiation-promoting condition) was investigated. In low Ca2+, HGF markedly enhanced the migration of keratinocytes while it suppressed cell growth and DNA synthesis in a dose-dependent manner. In contrast, HGF enhanced the migration, cell growth, and DNA synthesis of keratinocytes cultured under conditions of physiological Ca2+. The maximal stimulation of DNA synthesis (2.4-fold stimulation) in physiological Ca2+ was seen at 2.5-5 ng/ml HGF and the stimulatory effect of HGF was suppressed by transforming growth factor-beta 1. Analysis of the HGF receptor using 125I-HGF as a ligand showed that human keratinocytes expressed a single class of specific, saturable receptor for HGF in both low and physiological Ca2+ conditions, exhibiting a Kd = 17.3 pM and approximately 690 binding sites/cell under physiological Ca2+. Thus, HGF is a potent factor which enhances growth and migration of normal human keratinocytes under conditions of physiological Ca2+. HGF may play an important role in epidermal tissue repair as it enhances both the migration and growth of keratinocytes.

  12. Light and electron microscopical visualization of anterogradely labelled corticospinal growth cones using a new combination of HRP staining techniques.

    PubMed

    Joosten, E A

    1991-05-01

    Up until now, the ultrastructural visualization of growth cones of developing long fibre tracts could only be achieved by horseradish peroxidase (HRP) application 'en route', resulting in axonal damage, which in turn may affect growth cone morphology. Besides, this technique results in labelling of passing fibres, thus hampering the identification of axon origin as well as the interpretation of growth cone configuration. In the present investigation a new combination of HRP staining and intensification techniques is presented which makes it possible to visualize anterogradely labelled corticospinal growth cones over long distances in developing rat spinal cord at the light as well as the electron microscopical level. HRP was applied to the originating cells of the corticospinal tract, located in the sensorimotor cortex, and after 24 h was visualized using a procedure which essentially consists of 3 subsequent steps: first a tetramethylbenzidine (TMB)/ammoniumheptamolybdate (AHM) reaction; second diaminobenzidine (DAB)/nickel (Ni) stabilization and finally glucose oxidase intensification. As was verified at the EM level, the staining procedure here described reveals a complete intense black staining of HRP-labelled growth cones of outgrowing corticospinal axons. Therefore, the method described here guarantees a correct analysis of growth cone morphology at the light microscopical and the ultrastructural level. The present procedure is especially valuable in studying the development of long central nervous fibre systems.

  13. The discovery of the growth cone and its influence on the study of axon guidance

    PubMed Central

    Tamariz, Elisa; Varela-Echavarría, Alfredo

    2015-01-01

    For over a century, there has been a great deal of interest in understanding how neural connectivity is established during development and regeneration. Interest in the latter arises from the possibility that knowledge of this process can be used to re-establish lost connections after lesion or neurodegeneration. At the end of the XIX century, Santiago Ramón y Cajal discovered that the distal tip of growing axons contained a structure that he called the growth cone. He proposed that this structure enabled the axon’s oriented growth in response to attractants, now known as chemotropic molecules. He further proposed that the physical properties of the surrounding tissues could influence the growth cone and the direction of growth. This seminal discovery afforded a plausible explanation for directed axonal growth and has led to the discovery of axon guidance mechanisms that include diffusible attractants and repellants and guidance cues anchored to cell membranes or extracellular matrix. In this review the major events in the development of this field are discussed. PMID:26029056

  14. The metalloproteinase stromelysin-1 (transin) mediates PC12 cell growth cone invasiveness through basal laminae.

    PubMed

    Nordstrom, L A; Lochner, J; Yeung, W; Ciment, G

    1995-02-01

    Matrix metalloproteinases have been implicated in various extracellular matrix remodeling events that occur during normal development and in a number of pathologies. In previous work with PC12 rat pheochromocytoma cells, we found that the matrix metalloproteinase stromelysin-1 (ST1) was highly induced by nerve growth factor (NGF), but not by epidermal growth factor (EGF). Here, we show that ST1 immunoreactivity is present in growth cones of NGF-treated PC12 cells, but not EGF-treated or untreated cells. To determine whether ST1 expression confers neurite invasiveness, three lines of PC12 cells were produced that constitutively express ST1 antisense mRNA. These lines expressed and secreted significantly reduced levels of ST1 protein, as determined by immunoblot and immunocytochemical methods, but otherwise responded normally to NGF-treatment by elaborating neurites. We found, however, that the neurites of these ST1 antisense cells showed a significantly reduced ability to penetrate a Matrigel reconstituted basal lamina, as compared to the parental cells, suggesting that ST1 confers neurite invasiveness. Finally, we show that ST1 is also expressed in vivo in sections through Embryonic Day 15 rat embryos, including neurons of both the peripheral and central nervous systems. These data indicate that ST1 may play a role in axonal growth in vivo, including a role in growth cone invasiveness.

  15. Whisker/Cone growth on the thermal control surfaces experiment no. S0069

    SciTech Connect

    Zwiener, J.M.; Coston, J.E. Jr.; Miller, E.R.; Mell, R.J.; Wilkes, D.R.

    1995-02-01

    An unusual surface `growth` was found during scanning electron microscope (SEM) investigations of the Thermal Control Surface Experiment (TCSE) S0069 front thermal cover. This `growth` is similar to the cone type whisker growth phenomena as studied by G. K. Wehner beginning in the 1960`s. Extensive analysis has identified the most probable composition of the whiskers to be a silicate type glass. Sources of the growth material are outgassing products from the experiment and orbital atomic oxygen, which occurs naturally at the orbital altitudes of the LDEF mission in the form of neutral atomic oxygen. The highly ordered symmetry and directionality of the whiskers are attributed to the long term (5.8 year) stable flight orientation of the LDEF.

  16. Automated laser guidance of neuronal growth cones using a spatial light modulator.

    PubMed

    Carnegie, David J; Cizmár, Tomás; Baumgartl, Jörg; Gunn-Moore, Frank J; Dholakia, Kishan

    2009-11-01

    The growth cone of a developing neuron can be guided using a focused infra-red (IR) laser beam [1]. In previous setups this process has required a significant amount of user intervention to adjust continuously the laser beam to guide the growing neuron. Previously, a system using an acousto-optical deflector (AOD) has been developed to steer the beam [2]. However, to enhance the controllability of this system, here we demonstrate the use of a computer controlled spatial light modulator (SLM) to steer and manipulate the shape of a laser beam for use in guided neuronal growth. This new experimental setup paves the way to enable a comprehensive investigation into beam shaping effects on neuronal growth and we show neuronal growth initiated by a Bessel light mode. This is a robust platform to explore the biochemistry of this novel phenomenon.

  17. Whisker/Cone growth on the thermal control surfaces experiment no. S0069

    NASA Technical Reports Server (NTRS)

    Zwiener, James M.; Coston, James E., Jr.; Miller, Edgar R.; Mell, Richard J.; Wilkes, Donald R.

    1995-01-01

    An unusual surface 'growth' was found during scanning electron microscope (SEM) investigations of the Thermal Control Surface Experiment (TCSE) S0069 front thermal cover. This 'growth' is similar to the cone type whisker growth phenomena as studied by G. K. Wehner beginning in the 1960's. Extensive analysis has identified the most probable composition of the whiskers to be a silicate type glass. Sources of the growth material are outgassing products from the experiment and orbital atomic oxygen, which occurs naturally at the orbital altitudes of the LDEF mission in the form of neutral atomic oxygen. The highly ordered symmetry and directionality of the whiskers are attributed to the long term (5.8 year) stable flight orientation of the LDEF.

  18. Ephrin-B2 elicits differential growth cone collapse and axon retraction in retinal ganglion cells from distinct retinal regions

    PubMed Central

    Petros, Timothy J.; Bryson, J. Barney; Mason, Carol

    2010-01-01

    The circuit for binocular vision and stereopsis is established at the optic chiasm, where retinal ganglion cell (RGC) axons diverge into the ipsilateral and contralateral optic tracts. In the mouse retina, ventrotemporal (VT) RGCs express the guidance receptor EphB1, which interacts with the repulsive guidance cue ephrin-B2 on radial glia at the optic chiasm to direct VT RGC axons ipsilaterally. RGCs in the ventral retina also express EphB2, which interacts with ephrin-B2, whereas dorsal RGCs express low levels of EphB receptors. To investigate how growth cones of RGCs from different retinal regions respond upon initial contact with ephrin-B2, we utilized time-lapse imaging to characterize the effects of ephrin-B2 on growth cone collapse and axon retraction in real time. We demonstrate that bath application of ephrin-B2 induces rapid and sustained growth cone collapse and axon retraction in VT RGC axons, whereas contralaterally-projecting dorsotemporal RGCs display moderate growth cone collapse and little axon retraction. Dose response curves reveal that contralaterally-projecting ventronasal axons are less sensitive to ephrin-B2 treatment compared to VT axons. Additionally, we uncovered a specific role for Rho kinase signaling in the retraction of VT RGC axons but not in growth cone collapse. The detailed characterization of growth cone behavior in this study comprises an assay for the study of Eph signaling in RGCs, and provides insight into the phenomena of growth cone collapse and axon retraction in general. PMID:20629048

  19. Hepatocyte growth factor/scatter factor modulates cell motility, proliferation, and proteoglycan synthesis of chondrocytes.

    PubMed

    Takebayashi, T; Iwamoto, M; Jikko, A; Matsumura, T; Enomoto-Iwamoto, M; Myoukai, F; Koyama, E; Yamaai, T; Matsumoto, K; Nakamura, T

    1995-06-01

    Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional growth factor that promotes proliferation, motility, and morphogenesis in epithelial cells. Recently the HGF receptor, c-met protooncogene product, has been shown to be expressed in developing limb buds (Sonnenberg, E., D. Meyer, M. Weidner, and C. Birchmeiyer, 1993. J. Cell Biol. 123: 223-235), suggesting that some populations of mesenchymal cells in limb buds respond to HGF/SF. To test the possibility that HGF/SF is involved in regulation of cartilage development, we isolated chondrocytes from knee joints and costal cartilages of 23-d embryonic and 4-wk-old rabbits, and analyzed the effects of HGF/SF on migration and proliferation of these cells. We found that HGF/SF stimulated migration of cultured articular chondrocytes but did not scatter limb mesenchymal fibroblasts or synovial fibroblasts in culture. HGF/SF also stimulated proliferation of chondrocytes; a maximum three-fold stimulation in DNA synthesis was observed at the concentration of 3 ng/ml of HGF/SF. Moreover, HGF/SF had the ability to enhance proteoglycan synthesis in chondrocytes. The responsiveness of chondrocytes to HGF/SF was also supported by the observation that they expressed the HGF/SF receptor. Addition of the neutralizing antibody to rat HGF/SF affected neither DNA synthesis nor proteoglycan synthesis in rat chondrocytes, suggesting a paracine mechanism of action of HGF/SF on these cells. In situ hybridization analysis showed that HGF/SF mRNA was restrictively expressed in the areas of future joint regions in developing limb buds and in the intercostal spaces of developing costal cartilages. These findings suggest that HGF/SF plays important roles in cartilage development through its multiple activities.

  20. Hepatocyte growth factor/scatter factor modulates cell motility, proliferation, and proteoglycan synthesis of chondrocytes

    PubMed Central

    1995-01-01

    Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional growth factor that promotes proliferation, motility, and morphogenesis in epithelial cells. Recently the HGF receptor, c-met protooncogene product, has been shown to be expressed in developing limb buds (Sonnenberg, E., D. Meyer, M. Weidner, and C. Birchmeiyer, 1993. J. Cell Biol. 123: 223-235), suggesting that some populations of mesenchymal cells in limb buds respond to HGF/SF. To test the possibility that HGF/SF is involved in regulation of cartilage development, we isolated chondrocytes from knee joints and costal cartilages of 23-d embryonic and 4-wk-old rabbits, and analyzed the effects of HGF/SF on migration and proliferation of these cells. We found that HGF/SF stimulated migration of cultured articular chondrocytes but did not scatter limb mesenchymal fibroblasts or synovial fibroblasts in culture. HGF/SF also stimulated proliferation of chondrocytes; a maximum three-fold stimulation in DNA synthesis was observed at the concentration of 3 ng/ml of HGF/SF. Moreover, HGF/SF had the ability to enhance proteoglycan synthesis in chondrocytes. The responsiveness of chondrocytes to HGF/SF was also supported by the observation that they expressed the HGF/SF receptor. Addition of the neutralizing antibody to rat HGF/SF affected neither DNA synthesis nor proteoglycan synthesis in rat chondrocytes, suggesting a paracine mechanism of action of HGF/SF on these cells. In situ hybridization analysis showed that HGF/SF mRNA was restrictively expressed in the areas of future joint regions in developing limb buds and in the intercostal spaces of developing costal cartilages. These findings suggest that HGF/SF plays important roles in cartilage development through its multiple activities. PMID:7775584

  1. Mechanical properties of neuronal growth cone membranes studied by tether formation with laser optical tweezers.

    PubMed Central

    Dai, J.; Sheetz, M. P.

    1995-01-01

    Many cell phenomena involve major morphological changes, particularly in mitosis and the process of cell migration. For cells or neuronal growth cones to migrate, they must extend the leading edge of the plasma membrane as a lamellipodium or filopodium. During extension of filopodia, membrane must move across the surface creating shear and flow. Intracellular biochemical processes driving extension must work against the membrane mechanical properties, but the forces required to extend growth cones have not been measured. In this paper, laser optical tweezers and a nanometer-level analysis system were used to measure the neuronal growth cone membrane mechanical properties through the extension of filopodia-like tethers with IgG-coated beads. Although the probability of a bead attaching to the membrane was constant irrespective of treatment; the probability of forming a tether with a constant force increased dramatically with cytochalasin B or D and dimethylsulfoxide (DMSO). These are treatments that alter the organization of the actin cytoskeleton. The force required to hold a tether at zero velocity (F0) was greater than forces generated by single molecular motors, kinesin and myosin; and F0 decreased with cytochalasin B or D and DMSO in correlation with the changes in the probability of tether formation. The force of the tether on the bead increased linearly with the velocity of tether elongation. From the dependency of tether force on velocity of tether formation, we calculated a parameter related to membrane viscosity, which decreased with cytochalasin B or D, ATP depletion, nocodazole, and DMSO. These results indicate that the actin cytoskeleton affects the membrane mechanical properties, including the force required for membrane extension and the viscoelastic behavior. Images FIGURE 4 PMID:7756561

  2. Membrane proteins of the nerve growth cone and their developmental regulation

    SciTech Connect

    Simkowitz, P.; Ellis, L.; Pfenninger, K.H.

    1989-03-01

    The membrane polypeptides of growth cone fragments (growth cone particles, GCPs) isolated from fetal rat brain by subcellular fractionation have been analyzed in further detail. The major polypeptides of salt-washed GCP membranes detected by 1-dimensional gel electrophoresis resolve in 2-dimensional gels as a spot of 52 kDa that comigrates with beta-tubulin and reacts with anti-beta-tubulin; a 46 kDa, pl 4.3, polypeptide (pp46) that has no equivalent in the soluble fraction and is identical to one of the GCP's major phosphoproteins and to GAP43; a spot of 42 kDa that comigrates with actin; and a species of 34 kDa (p34) without soluble equivalent. The prominent 38 kDa doublet identified in 1-dimensional gels is difficult to resolve in 2-dimensional gels. The major phosphoproteins pp80ac, pp46, and pp40, as well as p34 partition into the oil phase of Triton X-114 extracts, suggesting that they are integral membrane proteins, at least in our experimental conditions. The properties of pp46 reported here are in conflict with the highly hydrophilic amino acid sequence predicted for GAP43/B50/F1. Growth-cone and presynaptic membrane proteins are compared as follows. After eye injection of 35S-methionine, GCPs and synaptosomes are isolated from the target areas of optic nerve of fetal and adult rats, respectively. Polypeptides are separated by 1- and 2-dimensional gel electrophoresis and the radiolabeled species identified fluorographically. The comparison of labeled GCP and synaptosome polypeptides shows that all 5 major Coomassie blue-stained polypeptides of GCP membranes (52, 46, 42, 38, 34 kDa) are intensely labeled after eye injection. However, in synaptosomes, these polypeptides are weakly labeled if at all; instead, an intensely labeled polypeptide of 28 kDa, and several additional species not seen in GCPs, have appeared.

  3. Akt1-Inhibitor of DNA binding2 is essential for growth cone formation and axon growth and promotes central nervous system axon regeneration

    PubMed Central

    Ko, Hyo Rim; Kwon, Il-Sun; Hwang, Inwoo; Jin, Eun-Ju; Shin, Joo-Ho; Brennan-Minnella, Angela M; Swanson, Raymond; Cho, Sung-Woo; Lee, Kyung-Hoon; Ahn, Jee-Yin

    2016-01-01

    Mechanistic studies of axon growth during development are beneficial to the search for neuron-intrinsic regulators of axon regeneration. Here, we discovered that, in the developing neuron from rat, Akt signaling regulates axon growth and growth cone formation through phosphorylation of serine 14 (S14) on Inhibitor of DNA binding 2 (Id2). This enhances Id2 protein stability by means of escape from proteasomal degradation, and steers its localization to the growth cone, where Id2 interacts with radixin that is critical for growth cone formation. Knockdown of Id2, or abrogation of Id2 phosphorylation at S14, greatly impairs axon growth and the architecture of growth cone. Intriguingly, reinstatement of Akt/Id2 signaling after injury in mouse hippocampal slices redeemed growth promoting ability, leading to obvious axon regeneration. Our results suggest that Akt/Id2 signaling is a key module for growth cone formation and axon growth, and its augmentation plays a potential role in CNS axonal regeneration. DOI: http://dx.doi.org/10.7554/eLife.20799.001 PMID:27938661

  4. Akt1-Inhibitor of DNA binding2 is essential for growth cone formation and axon growth and promotes central nervous system axon regeneration.

    PubMed

    Ko, Hyo Rim; Kwon, Il-Sun; Hwang, Inwoo; Jin, Eun-Ju; Shin, Joo-Ho; Brennan-Minnella, Angela M; Swanson, Raymond; Cho, Sung-Woo; Lee, Kyung-Hoon; Ahn, Jee-Yin

    2016-12-12

    Mechanistic studies of axon growth during development are beneficial to the search for neuron-intrinsic regulators of axon regeneration. Here, we discovered that, in the developing neuron from rat, Akt signaling regulates axon growth and growth cone formation through phosphorylation of serine 14 (S14) on Inhibitor of DNA binding 2 (Id2). This enhances Id2 protein stability by means of escape from proteasomal degradation, and steers its localization to the growth cone, where Id2 interacts with radixin that is critical for growth cone formation. Knockdown of Id2, or abrogation of Id2 phosphorylation at S14, greatly impairs axon growth and the architecture of growth cone. Intriguingly, reinstatement of Akt/Id2 signaling after injury in mouse hippocampal slices redeemed growth promoting ability, leading to obvious axon regeneration. Our results suggest that Akt/Id2 signaling is a key module for growth cone formation and axon growth, and its augmentation plays a potential role in CNS axonal regeneration.

  5. A hybrid computational model to predict chemotactic guidance of growth cones

    PubMed Central

    Roccasalvo, Iolanda Morana; Micera, Silvestro; Sergi, Pier Nicola

    2015-01-01

    The overall strategy used by growing axons to find their correct paths during the nervous system development is not yet completely understood. Indeed, some emergent and counterintuitive phenomena were recently described during axon pathfinding in presence of chemical gradients. Here, a novel computational model is presented together with its ability to reproduce both regular and counterintuitive axonal behaviours. In this model, the key role of intracellular calcium was phenomenologically modelled through a non standard Gierer-Meinhardt system, as a crucial factor influencing the growth cone behaviour both in regular and complex conditions. This model was able to explicitly reproduce neuritic paths accounting for the complex interplay between extracellular and intracellular environments, through the sensing capability of the growth cone. The reliability of this approach was proven by using quantitative metrics, numerically supporting the similarity between in silico and biological results in regular conditions (control and attraction). Finally, the model was able to qualitatively predict emergent and counterintuitive phenomena resulting from complex boundary conditions. PMID:26086936

  6. Transient Directed Motions of GABAA Receptors in Growth Cones Detected by a Speed Correlation Index

    PubMed Central

    Bouzigues, Cédric; Dahan, Maxime

    2007-01-01

    Single-molecule tracking of membrane proteins has become an important tool for investigating dynamic processes in live cells, such as cell signaling, membrane compartmentation or trafficking. The extraction of relevant parameters, such as interaction times between molecular partners or confinement-zone sizes, from the trajectories of single molecules requires appropriate statistical methods. Here we report a new tool, the speed correlation index, designed to detect transient periods of directed motion within trajectories of diffusing molecules. The ability to detect such events in a wide range of biologically relevant parameter values (speed, diffusion coefficient, and durations of the directed period) was first established on simulated data. The method was next applied to analyze the trajectories of quantum-dot-labeled GABAA receptors in nerve growth cones. The use of the speed correlation index revealed that the receptors had a “conveyor belt” type of motion due to temporary interactions (∼4.0 s) between the receptors and the microtubules, leading to an average directed motion (velocity ∼0.3 μm s−1) in the growth-cone membrane. Our observations point to the possibility of a cytoskeleton-dependent redistribution of the sensing molecules in the membrane, which could play a role in the modulation of the cell response to external signals. PMID:17071660

  7. Retinoic acid induces neurite outgrowth and growth cone turning in invertebrate neurons.

    PubMed

    Dmetrichuk, Jennifer M; Carlone, Robert L; Spencer, Gaynor E

    2006-06-01

    Identification of molecules involved in neurite outgrowth during development and/or regeneration is a major goal in the field of neuroscience. Retinoic acid (RA) is a biologically important metabolite of vitamin A that acts as a trophic factor and has been implicated in neurite outgrowth and regeneration in many vertebrate species. Although abundant in the CNS of many vertebrates, the precise role of RA in neural regeneration has yet to be determined. Moreover, very little information is available regarding the role of RA in invertebrate nervous systems. Here, we demonstrate for the first time that RA induces neurite outgrowth from invertebrate neurons. Using individually identified neurons isolated from the CNS of Lymnaea stagnalis, we demonstrated that a significantly greater proportion of cells produced neurite outgrowth in RA. RA also extended the duration of time that cells remained electrically excitable in vitro, and we showed that exogenously applied RA acted as a chemoattractive factor and induced growth cone turning toward the source of RA. This is the first demonstration that RA can induce turning of an individual growth cone. These data strongly suggest that the actions of RA on neurite outgrowth and cell survival are highly conserved across species.

  8. Glutamate restores growth but not motility in the absence of chloride in the moderate halophile Halobacillus halophilus.

    PubMed

    Saum, Stephan H; Roessler, Markus; Koller, Christiane; Sydow, Jasmin F; Müller, Volker

    2007-09-01

    Halobacillus halophilus is a strictly chloride-dependent, moderately halophilic bacterium that synthesizes glutamate and glutamine as the major compatible solutes at intermediate NaCl concentrations. The key enzyme in production of the compatible solutes glutamine and glutamate, glutamine synthetase, is dependent on chloride on a transcriptional and activity level. This led us to ask whether exogenous supply of glutamate may relief the chloride dependence of growth of H. halophilus. Growth of H. halophilus in minimal medium at 1 M NaCl was stimulated by exogenous glutamate and transport experiments revealed a chloride-independent glutamate uptake by whole cells. Growth was largely impaired in the absence of chloride and, at the same time, glutamate and glutamine pools were reduced by 90%. Exogenous glutamate fully restored growth, and cellular glutamate and glutamine pools were refilled. Although glutamate could restore growth in the absence of chloride, another chloride-dependent process, flagellum synthesis and motility, was not restored by glutamate. The differential effect of glutamate on the two chloride-dependent processes, growth and motility, indicates that glutamate can not substitute chloride in general but apparently bypasses one function of the chloride regulon, the adjustment of pool sizes of compatible solutes.

  9. Heparin Inhibits Hepatocyte Growth Factor Induced Motility and Invasion of Hepatocellular Carcinoma Cells through Early Growth Response Protein 1

    PubMed Central

    Ozen, Evin; Gozukizil, Aysim; Erdal, Esra; Uren, Aykut; Bottaro, Donald P.; Atabey, Nese

    2012-01-01

    The Hepatocyte Growth Factor (HGF)/c-Met signaling pathway regulates hepatocyte proliferation, and pathway aberrations are implicated in the invasive and metastatic behaviors of hepatocellular carcinoma (HCC). In addition to c-Met, heparin acts as a co-receptor to modulate pathway activity. Recently, anti-metastatic and anti-cancer effects of heparin have been reported. However, the role of heparin in the regulation of HGF signaling remains controversial and the effects of heparin on HGF-induced biological responses during hepatocarcinogenesis is not yet defined. In this study we determined the effects of heparin on HGF-induced activities of HCC cells and the underlying molecular mechanisms. Here, we report for the first time that heparin inhibits HGF-induced adhesion, motility and invasion of HCC cells. In addition, heparin reduced HGF-induced activation of c-Met and MAPK in a dose-dependent manner, as well as decreased transcriptional activation and expression of Early growth response factor 1 (Egr1). HGF-induced MMP-2 and MMP-9 activation, and MT1-MMP expression, also were inhibited by heparin. Stable knockdown of Egr1 caused a significant decrease in HGF-induced invasion, as well as the activation and expression of MMPs. Parallel to these findings, the overexpression of Egr1 increased the invasiveness of HCC cells. Our results suggest that Egr1 activates HGF-induced cell invasion through the regulation of MMPs in HCC cells and heparin inhibits HGF-induced cellular invasion via the downregulation of Egr1. Therefore, heparin treatment might be a therapeutic approach to inhibit invasion and metastasis of HCC, especially for patients with active HGF/c-Met signaling. PMID:22912725

  10. Substrate Availability of Mutant SPT Alters Neuronal Branching and Growth Cone Dynamics in Dorsal Root Ganglia

    PubMed Central

    Jun, Byung Kyu; Chandra, Ankush; Kuljis, Dika; Schmidt, Brian P.

    2015-01-01

    Serine palmitoyltransferase (SPT) is a key enzyme in the first step of sphingolipid biosynthesis. Mutations in the SPTLC1 gene that encodes for SPT subunits cause hereditary sensory neuropathy type 1. However, little is understood about how mutant SPT regulates mechanisms of sensory neuron and axonal growth. Using transgenic mice overexpressing the C133W SPT mutant, we found that mutant dorsal root ganglia (DRG) during growth in vitro exhibit increased neurite length and branching, coinciding with elevated expression of actin-cross-linking proteins at the neuronal growth cone, namely phosphorylated Ezrin/Radixin/Moesin. In addition, inhibition of SPT was able to reverse the mutant phenotype. Because mutant SPT preferentially uses l-alanine over its canonical substrate l-serine, we also investigated the effects of substrate availability on DRG neurons. Supplementation with l-serine or removal of l-alanine independently restored normal growth patterns in mutant SPTLC1C133W DRG. Therefore, we report that substrate availability and selectivity of SPT influence the regulation of neurite growth in DRG neurons. SIGNIFICANCE STATEMENT Hereditary sensory neuropathy type 1 is an autosomal-dominant disorder that leads to a sensory neuropathy due to mutations in the serine palmitoyltransferase (SPT) enzyme. We investigated how mutant SPT and substrate levels regulate neurite growth. Because SPT is an important enzyme in the synthesis of sphingolipids, our data are of broader significance to other peripheral and metabolic disorders. PMID:26446223

  11. Multiple factors underlying the maximum motility of Escherichia coli as cultures enter post-exponential growth.

    PubMed Central

    Amsler, C D; Cho, M; Matsumura, P

    1993-01-01

    Motility and chemotaxis allow cells to move away from stressful microenvironments. Motility of Escherichia coli in batch cultures, as measured by cell swimming speed, was low in early-exponential-phase cells, peaked as the cells entered post-exponential phase, and declined into early stationary phase. Transcription from the flhB operon and synthesis of flagellin protein similarly peaked in late exponential and early post-exponential phases, respectively. The increase in swimming speed between early-exponential and post-exponential phases was correlated with twofold increases in both flagellar length and flagellar density per cell volume. This increased investment in flagella probably reflects the increased adaptive value of motility in less favorable environments. The decrease in speed between post-exponential and stationary phases was correlated with a threefold decrease in torque produced by the flagellar motors and presumably reflects decreased proton motive force available to stationary-phase cells. Images PMID:8407796

  12. The growth cones of Aplysia sensory neurons: Modulation by serotonin of action potential duration and single potassium channel currents.

    PubMed

    Belardetti, F; Schacher, S; Kandel, E R; Siegelbaum, S A

    1986-09-01

    Serotonin (5-HT) closes a specific K channel ("S") in the cell body of Aplysia sensory neurons, resulting in a slow excitatory postsynaptic potential and spike broadening. To determine whether the S channel is present and can be modulated in processes of the neuron other than the cell body, we studied the effects of 5-HT on growth cones of sensory neurons in culture by using the patch-clamp technique. Simultaneous application of 5-HT to the cell body and to the growth cones of sensory neurons produced, in both, a slow depolarization of approximately 5 mV. Also, 5-HT produced a lengthening of the duration of action potential in the growth cone and cell body by 20-30%. Similar effects were observed in isolated growth cones that had been severed from the rest of the neuron, implying that the growth cones contain all the molecular components (i.e., receptors, channels, cAMP cascade) necessary for 5-HT action. Cell-attached patch-clamp recordings demonstrated the presence of S channels in sensory neuron growth cones. Application of serotonin to the bath produced long-lasting all-or-none closures of these channels in a manner identical to the previously characterized action of 5-HT in the cell body. Thus, channel modulation is not restricted to the cell body and probably occurs throughout the sensory neuron. This strengthens the view that S-channel modulation may also occur at the sensory neuron presynaptic terminal, where it could play a role in the presynaptic facilitation produced by 5-HT.

  13. A phenotypic screening platform to identify small molecule modulators of Chlamydomonas reinhardtii growth, motility and photosynthesis

    PubMed Central

    2012-01-01

    Chemical biology, the interfacial discipline of using small molecules as probes to investigate biology, is a powerful approach of developing specific, rapidly acting tools that can be applied across organisms. The single-celled alga Chlamydomonas reinhardtii is an excellent model system because of its photosynthetic ability, cilia-related motility and simple genetics. We report the results of an automated fitness screen of 5,445 small molecules and subsequent assays on motility/phototaxis and photosynthesis. Cheminformatic analysis revealed active core structures and was used to construct a naïve Bayes model that successfully predicts algal bioactive compounds. PMID:23158586

  14. Ganglioside GM3 exerts opposite effects on motility via epidermal growth factor receptor and hepatocyte growth factor receptor-mediated migration signaling.

    PubMed

    Li, Ying; Huang, Xiaohua; Wang, Congcong; Li, Yuzhong; Luan, Mingchun; Ma, Keli

    2015-04-01

    The ganglioside GM3 exerts its different effects via various growth factor receptors. The present study investigated and comparatively analyzed the opposing effects exerted by GM3 on the migration of mouse hepatocellular carcinoma Hepa1‑6 cells via epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor (HGFR/cMet). The results demonstrated that GM3 inhibited EGF‑stimulated motility, but promoted HGF‑stimulated motility of the Hepa1‑6 cells via phosphatidylinositol 3‑kinase/Akt‑mediated migration signaling. It is well established that the main cytokines modulating cell proliferation, invasion and metastasis are different in different types of tumor. This difference may, at least in part, explain why GM3 exerted its actions in a tumor‑type specific manner.

  15. Nerve growth factor promotes human sperm motility in vitro by increasing the movement distance and the number of A grade spermatozoa.

    PubMed

    Lin, Kai; Ding, Xue-Feng; Shi, Cui-Ge; Zeng, Dan; QuZong, SuoLang; Liu, Shu-Hong; Wu, Yan; LuoBu, GeSang; Fan, Ming; Zhao, Y-Q

    2015-11-01

    Nerve growth factor (NGF) was first found in the central nervous system and is now well known for its multiple pivotal roles in the nervous system and immune system. However, more and more evidences showed that NGF and its receptors TrkA and p75 were also found in the head and tail of spermatozoa, which indicate the possible effect of NGF on the sperm motility. Nevertheless, the exact role of NGF in the human sperm motility remains unclear until now. In this study, we investigated the effect of NGF on human sperm motility, and the results showed that NGF could promote human sperm motility in vitro by increasing the movement distance and the number of A grade spermatozoa. Further analysis demonstrated that NGF promoted the sperm motility in a dose-dependent manner in vitro. These results may facilitate the further studies on human fertility and assisted reproduction techniques.

  16. R-Type Calcium Channels Are Crucial for Semaphorin 3A–Induced DRG Axon Growth Cone Collapse

    PubMed Central

    Jover, Emmanuel; Bagnard, Dominique; Šatkauskas, Saulius

    2014-01-01

    Semaphorin 3A (Sema3A) is a secreted protein involved in axon path-finding during nervous system development. Calcium signaling plays an important role during axonal growth in response to different guidance cues; however it remains unclear whether this is also the case for Sema3A. In this study we used intracellular calcium imaging to figure out whether Sema3A-induced growth cone collapse is a Ca2+ dependent process. Intracellular Ca2+ imaging results using Fura-2 AM showed Ca2+ increase in E15 mice dorsal root ganglia neurons upon Sema3A treatment. Consequently we analyzed Sema3A effect on growth cones after blocking or modifying intracellular and extracellular Ca2+ channels that are expressed in E15 mouse embryos. Our results demonstrate that Sema3A increased growth cone collapse rate is blocked by the non-selective R- and T- type Ca2+ channel blocker NiCl2 and by the selective R-type Ca2+ channel blocker SNX482. These Ca2+ channel blockers consistently decreased the Sema3A-induced intracellular Ca2+ concentration elevation. Overall, our results demonstrate that Sema3A-induced growth cone collapses are intimately related with increase in intracellular calcium concentration mediated by R-type calcium channels. PMID:25032951

  17. R-type calcium channels are crucial for semaphorin 3A-induced DRG axon growth cone collapse.

    PubMed

    Treinys, Rimantas; Kaselis, Andrius; Jover, Emmanuel; Bagnard, Dominique; Šatkauskas, Saulius

    2014-01-01

    Semaphorin 3A (Sema3A) is a secreted protein involved in axon path-finding during nervous system development. Calcium signaling plays an important role during axonal growth in response to different guidance cues; however it remains unclear whether this is also the case for Sema3A. In this study we used intracellular calcium imaging to figure out whether Sema3A-induced growth cone collapse is a Ca2+ dependent process. Intracellular Ca2+ imaging results using Fura-2 AM showed Ca2+ increase in E15 mice dorsal root ganglia neurons upon Sema3A treatment. Consequently we analyzed Sema3A effect on growth cones after blocking or modifying intracellular and extracellular Ca2+ channels that are expressed in E15 mouse embryos. Our results demonstrate that Sema3A increased growth cone collapse rate is blocked by the non-selective R- and T- type Ca2+ channel blocker NiCl2 and by the selective R-type Ca2+ channel blocker SNX482. These Ca2+ channel blockers consistently decreased the Sema3A-induced intracellular Ca2+ concentration elevation. Overall, our results demonstrate that Sema3A-induced growth cone collapses are intimately related with increase in intracellular calcium concentration mediated by R-type calcium channels.

  18. α-Synuclein regulates the partitioning between tubulin dimers and microtubules at neuronal growth cone

    PubMed Central

    Cartelli, Daniele; Cappelletti, Graziella

    2017-01-01

    ABSTRACT The partitioning between tubulin dimers and microtubules is fundamental for the regulation of several neuronal activities, from neuronal polarization and processes extension to growth cone remodelling. This phenomenon is modulated by several proteins, including the well-known microtubule destabilizer Stathmin. We recently demonstrated that α-Synuclein, a presynaptic protein associated to Parkinson's disease, shares structural and functional properties with Stathmin, and we showed that α-Synuclein acts as a foldable dynamase. Here, we pinpoint the impact of wild type α-Synuclein on the partitioning between tubulin dimers and microtubules and show that Parkinson's disease-linked mutants lose this capability. Thus, our results indicate a new role for α-Synuclein in regulating microtubule system and support the concept that microtubules and α-Synuclein are partners in the modulation of neuronal health and degenerative processes. Furthermore, these data strengthen our hypothesis of the existence of a functional redundancy between α-Synuclein and Stathmin.

  19. Deformation and flow of membrane into tethers extracted from neuronal growth cones.

    PubMed Central

    Hochmuth, F M; Shao, J Y; Dai, J; Sheetz, M P

    1996-01-01

    Membrane tethers are extracted at constant velocity from neuronal growth cones using a force generated by a laser tweezers trap. A thermodynamic analysis shows that as the tether is extended, energy is stored in the tether as bending and adhesion energies and in the cell body as "nonlocal" bending. It is postulated that energy is dissipated by three viscous mechanisms including membrane flow, slip between the two monolayers that form the bilayer, and slip between membrane and cytoskeleton. The analysis predicts and the experiments show a linear relation between tether force and tether velocity. Calculations based on the analytical results and the experimental measurements of a tether radius of approximately 0.2 micron and a tether force at zero velocity of approximately 8 pN give a bending modulus for the tether of 2.7 x 10(-19) N.m and an extraordinarily small "apparent surface tension" in the growth cone of 0.003 mN/m, where the apparent surface tension is the sum of the far-field, in-plane tension and the energy of adhesion. Treatments with cytochalasin B and D, ethanol, and nocodazole affect the apparent surface tension but not bending. ATP depletion affects neither, whereas large concentrations of DMSO affect both. Under conditions of flow, data are presented to show that the dominant viscous mechanism comes from the slip that occurs when the membrane flows over the cytoskeleton. ATP depletion and the treatment with DMSO cause a dramatic drop in the effective viscosity. If it is postulated that the slip between membrane and cytoskeleton occurs in a film of water, then this water film has a mean thickness of only approximately 10 A. Images FIGURE 1 FIGURE 4 FIGURE 7 FIGURE 8 PMID:8770212

  20. α-TEA inhibits the growth and motility of human colon cancer cells via targeting RhoA/ROCK signaling

    PubMed Central

    Yao, Jialin; Gao, Peng; Xu, Yang; Li, Zhaozhu

    2016-01-01

    Colon or colorectal cancer is a common type of human cancer, which originates in the intestine crassum or the rectum. In the United States, colorectal cancer has one of the highest rates of cancer-related mortality. Investigating novel chemotherapeutic approaches is significant in the treatment of cancers, such as colorectal cancer. α-tocopherol ether-linked acetic acid (α-TEA) is a potent anticancer agent in multiple types of human cancer. However, its effect remains to be determined in colon cancer. In this study, HCT116 and SW480 human colon cancer cells were used to investigate the anticancer role of α-TEA. It was demonstrated that α-TEA inhibited cell proliferation, migration and invasion in colon cancer cells. Furthermore, it was shown that α-TEA downregulated the activity of RhoA and phosphorylated Rho-associated protein kinase (ROCK) substrate myosin light chain (MLC) using a pull-down assay and western blotting, respectively, implying that the RhoA/ROCK pathway is involved in α-TEA-mediated cell growth and motility inhibition. In order to confirm this hypothesis a RhoA inhibitor (clostridium botulinum C3 exoenzyme), a ROCK inhibitor (Y27632) and RhoA small interfering (si)RNA were applied to block RhoA/ROCK signaling. This resulted in the attenuation of MLC phosphorylation, and augmentation of α-TEA-mediated growth and motility inhibition in colon cancer cells. In conclusion, these results indicate that α-TEA inhibits growth and motility in colon cancer cells possibly by targeting RhoA/ROCK signaling. Moreover, combined with RhoA or ROCK inhibitors, α-TEA may exhibit a more effective inhibitory role in colon cancer. PMID:27432222

  1. α-TEA inhibits the growth and motility of human colon cancer cells via targeting RhoA/ROCK signaling.

    PubMed

    Yao, Jialin; Gao, Peng; Xu, Yang; Li, Zhaozhu

    2016-09-01

    Colon or colorectal cancer is a common type of human cancer, which originates in the intestine crassum or the rectum. In the United States, colorectal cancer has one of the highest rates of cancer‑related mortality. Investigating novel chemotherapeutic approaches is significant in the treatment of cancers, such as colorectal cancer. α-tocopherol ether-linked acetic acid (α-TEA) is a potent anticancer agent in multiple types of human cancer. However, its effect remains to be determined in colon cancer. In this study, HCT116 and SW480 human colon cancer cells were used to investigate the anticancer role of α-TEA. It was demonstrated that α-TEA inhibited cell proliferation, migration and invasion in colon cancer cells. Furthermore, it was shown that α-TEA downregulated the activity of RhoA and phosphorylated Rho-associated protein kinase (ROCK) substrate myosin light chain (MLC) using a pull-down assay and western blotting, respectively, implying that the RhoA/ROCK pathway is involved in α-TEA-mediated cell growth and motility inhibition. In order to confirm this hypothesis a RhoA inhibitor (clostridium botulinum C3 exoenzyme), a ROCK inhibitor (Y27632) and RhoA small interfering (si)RNA were applied to block RhoA/ROCK signaling. This resulted in the attenuation of MLC phosphorylation, and augmentation of α-TEA-mediated growth and motility inhibition in colon cancer cells. In conclusion, these results indicate that α-TEA inhibits growth and motility in colon cancer cells possibly by targeting RhoA/ROCK signaling. Moreover, combined with RhoA or ROCK inhibitors, α-TEA may exhibit a more effective inhibitory role in colon cancer.

  2. Corneal sulfated glycosaminoglycans and their effects on trigeminal nerve growth cone behavior in vitro: roles for ECM in cornea innervation.

    PubMed

    Schwend, Tyler; Deaton, Ryan J; Zhang, Yuntao; Caterson, Bruce; Conrad, Gary W

    2012-12-13

    Sensory trigeminal nerve growth cones innervate the cornea in a highly coordinated fashion. The purpose of this study was to determine if extracellular matrix glycosaminoglycans (ECM-GAGs), including keratan sulfate (KS), dermatan sulfate (DS), and chondroitin sulfate A (CSA) and C (CSC), polymerized in developing eyefronts, may provide guidance cues to nerves during cornea innervation. Immunostaining using antineuron-specific-β-tubulin and monoclonal antibodies for KS, DS, and CSA/C was performed on eyefronts from embryonic day (E) 9 to E14 and staining visualized by confocal microscopy. Effects of purified GAGs on trigeminal nerve growth cone behavior were tested using in vitro neuronal explant cultures. At E9 to E10, nerves exiting the pericorneal nerve ring grew as tight fascicles, advancing straight toward the corneal stroma. In contrast, upon entering the stroma, nerves bifurcated repeatedly as they extended anteriorly toward the epithelium. KS was localized in the path of trigeminal nerves, whereas DS and CSA/C-rich areas were avoided by growth cones. When E10 trigeminal neurons were cultured on different substrates comprised of purified GAG molecules, their neurite growth cone behavior varied depending on GAG type, concentration, and mode of presentation (immobilized versus soluble). High concentrations of immobilized KS, DS, and CSA/C inhibited neurite growth to varying degrees. Neurites traversing lower, permissive concentrations of immobilized DS and CSA/C displayed increased fasciculation and decreased branching, whereas KS caused decreased fasciculation and increased branching. Enzymatic digestion of sulfated GAGs canceled their effects on trigeminal neurons. Data herein suggest that GAGs may direct the movement of trigeminal nerve growth cones innervating the cornea.

  3. Corneal Sulfated Glycosaminoglycans and Their Effects on Trigeminal Nerve Growth Cone Behavior In Vitro: Roles for ECM in Cornea Innervation

    PubMed Central

    Schwend, Tyler; Deaton, Ryan J.; Zhang, Yuntao; Caterson, Bruce; Conrad, Gary W.

    2012-01-01

    Purpose. Sensory trigeminal nerve growth cones innervate the cornea in a highly coordinated fashion. The purpose of this study was to determine if extracellular matrix glycosaminoglycans (ECM–GAGs), including keratan sulfate (KS), dermatan sulfate (DS), and chondroitin sulfate A (CSA) and C (CSC), polymerized in developing eyefronts, may provide guidance cues to nerves during cornea innervation. Methods. Immunostaining using antineuron-specific-β-tubulin and monoclonal antibodies for KS, DS, and CSA/C was performed on eyefronts from embryonic day (E) 9 to E14 and staining visualized by confocal microscopy. Effects of purified GAGs on trigeminal nerve growth cone behavior were tested using in vitro neuronal explant cultures. Results. At E9 to E10, nerves exiting the pericorneal nerve ring grew as tight fascicles, advancing straight toward the corneal stroma. In contrast, upon entering the stroma, nerves bifurcated repeatedly as they extended anteriorly toward the epithelium. KS was localized in the path of trigeminal nerves, whereas DS and CSA/C–rich areas were avoided by growth cones. When E10 trigeminal neurons were cultured on different substrates comprised of purified GAG molecules, their neurite growth cone behavior varied depending on GAG type, concentration, and mode of presentation (immobilized versus soluble). High concentrations of immobilized KS, DS, and CSA/C inhibited neurite growth to varying degrees. Neurites traversing lower, permissive concentrations of immobilized DS and CSA/C displayed increased fasciculation and decreased branching, whereas KS caused decreased fasciculation and increased branching. Enzymatic digestion of sulfated GAGs canceled their effects on trigeminal neurons. Conclusions. Data herein suggest that GAGs may direct the movement of trigeminal nerve growth cones innervating the cornea. PMID:23132805

  4. Arginyltransferase ATE1 is targeted to the neuronal growth cones and regulates neurite outgrowth during brain development.

    PubMed

    Wang, Junling; Pavlyk, Iuliia; Vedula, Pavan; Sterling, Stephanie; Leu, N Adrian; Dong, Dawei W; Kashina, Anna

    2017-10-01

    Arginylation is an emerging protein modification mediated by arginyltransferase ATE1, shown to regulate embryogenesis and actin cytoskeleton, however its functions in different physiological systems are not well understood. Here we analyzed the role of ATE1 in brain development and neuronal growth by producing a conditional mouse knockout with Ate1 deletion in the nervous system driven by Nestin promoter (Nes-Ate1 mice). These mice were weaker than wild type, resulting in low postnatal survival rates, and had abnormalities in the brain that suggested defects in neuronal migration. Cultured Ate1 knockout neurons showed a reduction in the neurite outgrowth and the levels of doublecortin and F-actin in the growth cones. In wild type, ATE1 prominently localized to the growth cones, in addition to the cell bodies. Examination of the Ate1 mRNA sequence reveals the existence of putative zipcode-binding sequences involved in mRNA targeting to the cell periphery and local translation at the growth cones. Fluorescence in situ hybridization showed that Ate1 mRNA localized to the tips of the growth cones, likely due to zipcode-mediated targeting, and this localization coincided with spots of localization of arginylated β-actin, which disappeared in the presence of protein synthesis inhibitors. We propose that zipcode-mediated co-targeting of Ate1 and β-actin mRNA leads to localized co-translational arginylation of β-actin that drives the growth cone migration and neurite outgrowth. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  5. Involvement of gangliosides in the process of Cbp/PAG phosphorylation by Lyn in developing cerebellar growth cones.

    PubMed

    Sekino-Suzuki, Naoko; Yuyama, Kohei; Miki, Toshiaki; Kaneda, Mizuho; Suzuki, Hidenori; Yamamoto, Naomasa; Yamamoto, Tadashi; Oneyama, Chitose; Okada, Masato; Kasahara, Kohji

    2013-02-01

    The association of gangliosides with specific proteins in the central nervous system was examined by coimmunoprecipitation with an anti-ganglioside antibody. The monoclonal antibody to the ganglioside GD3 (R24) immunoprecipitated the Csk (C-terminal src kinase)-binding protein (Cbp). Sucrose density gradient analysis showed that Cbp of rat cerebellum was detected in detergent-resistant membrane (DRM) raft fractions. R24 treatment of the rat primary cerebellar cultures induced Lyn activation and tyrosine phosphorylation of Cbp. Treatment with anti-ganglioside GD1b antibody also induced tyrosine phosphorylation. Furthermore, over-expressions of Lyn and Cbp in Chinese hamster ovary (CHO) cells resulted in tyrosine 314 phosphorylation of Cbp, which indicates that Cbp is a substrate for Lyn. Immunoblotting analysis showed that the active form of Lyn and the Tyr314-phosphorylated form of Cbp were highly accumulated in the DRM raft fraction prepared from the developing cerebellum compared with the DRM raft fraction of the adult one. In addition, Lyn and the Tyr314-phosphorylated Cbp were highly concentrated in the growth cone fraction prepared from the developing cerebellum. Immunoelectron microscopy showed that Cbp and GAP-43, a growth cone marker, are localized in the same vesicles of the growth cone fraction. These results suggest that Cbp functionally associates with gangliosides on growth cone rafts in developing cerebella. © 2012 International Society for Neurochemistry.

  6. CRMP4 and CRMP2 Interact to Coordinate Cytoskeleton Dynamics, Regulating Growth Cone Development and Axon Elongation

    PubMed Central

    Tan, Minghui; Cha, Caihui; Ye, Yongheng; Zhang, Jifeng; Li, Sumei; Wu, Fengming; Gong, Sitang; Guo, Guoqing

    2015-01-01

    Cytoskeleton dynamics are critical phenomena that underpin many fundamental cellular processes. Collapsin response mediator proteins (CRMPs) are highly expressed in the developing nervous system, mediating growth cone guidance, neuronal polarity, and axonal elongation. However, whether and how CRMPs associate with microtubules and actin coordinated cytoskeletal dynamics remain unknown. In this study, we demonstrated that CRMP2 and CRMP4 interacted with tubulin and actin in vitro and colocalized with the cytoskeleton in the transition-zone in developing growth cones. CRMP2 and CRMP4 also interacted with one another coordinately to promote growth cone development and axonal elongation. Genetic silencing of CRMP2 enhanced, whereas overexpression of CRMP2 suppressed, the inhibitory effects of CRMP4 knockdown on axonal development. In addition, knockdown of CRMP2 or overexpression of truncated CRMP2 reversed the promoting effect of CRMP4. With the overexpression of truncated CRMP2 or CRMP4 lacking the cytoskeleton interaction domain, the promoting effect of CRMP was suppressed. These data suggest a model in which CRMP2 and CRMP4 form complexes to bridge microtubules and actin and thus work cooperatively to regulate growth cone development and axonal elongation. PMID:26064693

  7. Potential anthelmintic: D-psicose inhibits motility, growth and reproductive maturity of L1 larvae of Caenorhabditis elegans.

    PubMed

    Sato, Masashi; Kurose, Hiroyuki; Yamasaki, Toru; Izumori, Ken

    2008-04-01

    No anthelmintic sugars have yet been identified. Eight ketohexose stereoisomers (D- and L-forms of psicose, fructose, tagatose and sorbose), along with D-galactose and D-glucose, were examined for potency against L1 stage Caenorhabditis elegans fed Escherichia coli. Of the sugars, D-psicose specifically inhibited the motility, growth and reproductive maturity of the L1 stage. D-Psicose probably interferes with the nematode nutrition. The present results suggest that D-psicose, one of the rare sugars, is a potential anthelmintic.

  8. Identification of protein-bound oligosaccharides on the surface of growth cones that bind to muscle cells.

    PubMed

    Ambron, R T; Protic, J; Den, H; Gabel, C A

    1989-09-01

    In the accompanying paper (Gabel, Den, and Ambron, in press) it was shown that eight populations of glycopeptides are synthesized by single neurons of Aplysia californica. To see which glycopeptides might mediate interactions with target cells, we first identified glycopeptides that are transported selectively to synapses and growth cones. The giant neuron R2 was injected intrasomatically with 3H-glucosamine. Twenty-four hours later, 3H-glycopeptides in the axon and cell body were isolated and resolved by serial lectin affinity chromatography. Of the eight populations, the biantennary-type glycopeptides (GPbi) and those that bind to WGA (GPwga) were preferentially associated with rapidly transported glycoproteins. In contrast, the glycopeptide that consists of N-acetylglucosamine O-linked to ser/thr was mostly retained in the cell body. GPbi and GPwga were also preferentially transported to growth cones. Analyses of RUQ cells, exposed to 3H-glucosamine in vitro for 36 h showed an enrichment of GPbi and GPwga at the growth cone relative to the cell body. The disposition of the various glycopeptides in growing neurons was also examined using FITC lectins. FITC-coupled WGA, Vicia vellosa, and lentil lectin showed extensive staining of the cell body, but only WGA stained the growth cones. To investigate if GPwga interacts specifically with target cells, these glycopeptides were isolated from the neurons of 180 abdominal ganglia. GPwga, other Aplysia glycopeptides, and glycopeptides prepared from ovalbumin were coupled separately to fluorescent spheres. The spheres were then added to muscle cells isolated from the auricle of the heart, which is innervated by many neurons from the ganglion. While spheres coupled to GPwga bound to the muscle cell surface, the other glycopeptides did not. These results indicate that glycopeptides class GPwga, found among rapidly transported glycoproteins and on the growth cone surface, is able to bind to muscle cells and may therefore play

  9. Growth of microscopic cones on titanium cathodes of sputter-ion pumps driven by sorption of large argon quantities

    SciTech Connect

    Porcelli, Tommaso; Siviero, Fabrizio; Bongiorno, Gero A.; Michelato, Paolo; Pagani, Carlo

    2015-09-15

    Microscopic cones have been observed on titanium cathodes of sputter-ion pumps (SIPs) after pump operation. The cones were studied by means of scanning electron microscopy and energy dispersive x-ray analysis. Size and morphology of these cones are clearly correlated with the nature and the relative amount of each gas species pumped by each SIP during its working life. In particular, their growth was found to be fed by sputtering mechanisms, mostly during Ar pumping, and to be driven by the electromagnetic field applied to the Penning cells of each SIP. Experimental findings suggest that the formation and extent of such conic structures on cathode surfaces might play a leading role in the onset of phenomena typically related to the functioning of SIPs, e.g., the so-called argon instability.

  10. Influence of lysogeny of Tectiviruses GIL01 and GIL16 on Bacillus thuringiensis growth, biofilm formation, and swarming motility.

    PubMed

    Gillis, Annika; Mahillon, Jacques

    2014-12-01

    Bacillus thuringiensis is an entomopathogenic bacterium that has been used as an efficient biopesticide worldwide. Despite the fact that this bacterium is usually described as an insect pathogen, its life cycle in the environment is still largely unknown. B. thuringiensis belongs to the Bacillus cereus group of bacteria, which has been associated with many mobile genetic elements, such as species-specific temperate or virulent bacteriophages (phages). Temperate (lysogenic) phages are able to establish a long-term relationship with their host, providing, in some cases, novel ecological traits to the bacterial lysogens. Therefore, this work focuses on evaluating the potential influence of temperate tectiviruses GIL01 and GIL16 on the development of different life traits of B. thuringiensis. For this purpose, a B. thuringiensis serovar israelensis plasmid-cured (nonlysogenic) strain was used to establish bacterial lysogens for phages GIL01 and GIL16, and, subsequently, the following life traits were compared among the strains: kinetics of growth, metabolic profiles, antibiotics susceptibility, biofilm formation, swarming motility, and sporulation. The results revealed that GIL01 and GIL16 lysogeny has a significant influence on the bacterial growth, sporulation rate, biofilm formation, and swarming motility of B. thuringiensis. No changes in metabolic profiles or antibiotic susceptibilities were detected. These findings provide evidence that tectiviruses have a putative role in the B. thuringiensis life cycle as adapters of life traits with ecological advantages. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  11. Influence of Lysogeny of Tectiviruses GIL01 and GIL16 on Bacillus thuringiensis Growth, Biofilm Formation, and Swarming Motility

    PubMed Central

    Gillis, Annika

    2014-01-01

    Bacillus thuringiensis is an entomopathogenic bacterium that has been used as an efficient biopesticide worldwide. Despite the fact that this bacterium is usually described as an insect pathogen, its life cycle in the environment is still largely unknown. B. thuringiensis belongs to the Bacillus cereus group of bacteria, which has been associated with many mobile genetic elements, such as species-specific temperate or virulent bacteriophages (phages). Temperate (lysogenic) phages are able to establish a long-term relationship with their host, providing, in some cases, novel ecological traits to the bacterial lysogens. Therefore, this work focuses on evaluating the potential influence of temperate tectiviruses GIL01 and GIL16 on the development of different life traits of B. thuringiensis. For this purpose, a B. thuringiensis serovar israelensis plasmid-cured (nonlysogenic) strain was used to establish bacterial lysogens for phages GIL01 and GIL16, and, subsequently, the following life traits were compared among the strains: kinetics of growth, metabolic profiles, antibiotics susceptibility, biofilm formation, swarming motility, and sporulation. The results revealed that GIL01 and GIL16 lysogeny has a significant influence on the bacterial growth, sporulation rate, biofilm formation, and swarming motility of B. thuringiensis. No changes in metabolic profiles or antibiotic susceptibilities were detected. These findings provide evidence that tectiviruses have a putative role in the B. thuringiensis life cycle as adapters of life traits with ecological advantages. PMID:25261525

  12. The effects of cell compressibility, motility and contact inhibition on the growth of tumor cell clusters using the Cellular Potts Model.

    PubMed

    Li, Jonathan F; Lowengrub, John

    2014-02-21

    There are numerous biological examples where genes associated with migratory ability of cells also confer the cells with an increased fitness even though these genes may not have any known effect on the cell mitosis rates. Here, we provide insight into these observations by analyzing the effects of cell migration, compression, and contact inhibition on the growth of tumor cell clusters using the Cellular Potts Model (CPM) in a monolayer geometry. This is a follow-up of a previous study (Thalhauser et al. 2010) in which a Moran-type model was used to study the interaction of cell proliferation, migratory potential and death on the emergence of invasive phenotypes. Here, we extend the study to include the effects of cell size and shape. In particular, we investigate the interplay between cell motility and compressibility within the CPM and find that the CPM predicts that increased cell motility leads to smaller cells. This is an artifact in the CPM. An analysis of the CPM reveals an explicit inverse-relationship between the cell stiffness and motility parameters. We use this relationship to compensate for motility-induced changes in cell size in the CPM so that in the corrected CPM, cell size is independent of the cell motility. We find that subject to comparable levels of compression, clusters of motile cells grow faster than clusters of less motile cells, in qualitative agreement with biological observations and our previous study. Increasing compression tends to reduce growth rates. Contact inhibition penalizes clumped cells by halting their growth and gives motile cells an even greater advantage. Finally, our model predicts cell size distributions that are consistent with those observed in clusters of neuroblastoma cells cultured in low and high density conditions. © 2013 Elsevier Ltd. Published by Elsevier Ltd. All rights reserved.

  13. Distribution of GAP-43, beta-III tubulin and F-actin in developing and regenerating axons and their growth cones in vitro, following neurotrophin treatment.

    PubMed

    Avwenagha, Ovokeloye; Campbell, Gregor; Bird, Margaret M

    2003-11-01

    Brain derived neurotrophic factor (BDNF) when added to explant cultures of both embryonic and adult retinal ganglion cell (RGC) axons exerted a marked effect on their growth cone size and complexity and also on the intensity of GAP-43, beta-III tubulin and F-actin immunoreaction product in their axons. GAP-43 was distributed in axons, lamellipodia, and filopodia whereas beta-III tubulin was distributed along the length of developing and adult regenerating axons and also in the C-domain of their growth cones. BDNF-treated developing RGC growth cones were larger and displayed increased numbers of GAP-43 and microtubule-containing branches. Although filopodia and lamellipodia were lost from both developing and adult RGC growth cones following trkB-IgG treatment, the intensity of the immunoreaction product of all these molecules was reduced and trkB-IgGs had no effect on the axonal distribution of betas-III tubulin and GAP-43. BDNF-treated growth cones also displayed increased numbers of F-actin containing filopodia and axonal protrusions. This study demonstrates, for the first time, that trkB-IgG treatment causes the loss of F-actin in the P-domain of growth cone tips in developing and regenerating RGC axons. Although microtubules and F-actin domains normally remained distinct in cultured growth cones, beta-III tubulin and F-actin overlapped within the growth cone C-domain, and within axonal protrusions of adult RGC axons, under higher concentrations of BDNF. The collapse of RGC growth cones appeared to correlate with the loss of F-actin. In vitro, trkB signalling may therefore be involved in the maintenance and stabilisation of RGC axons, by influencing F-actin polymerisation, stabilisation and distribution.

  14. Biophysical Properties and Motility of Human Mature Dendritic Cells Deteriorated by Vascular Endothelial Growth Factor through Cytoskeleton Remodeling

    PubMed Central

    Hu, Zu-Quan; Xue, Hui; Long, Jin-Hua; Wang, Yun; Jia, Yi; Qiu, Wei; Zhou, Jing; Wen, Zong-Yao; Yao, Wei-Juan; Zeng, Zhu

    2016-01-01

    Dendritic cells (DCs), the most potent antigen-presenting cells, play a central role in the initiation, regulation, and maintenance of the immune responses. Vascular endothelial growth factor (VEGF) is one of the important cytokines in the tumor microenvironment (TME) and can inhibit the differentiation and functional maturation of DCs. To elucidate the potential mechanisms of DC dysfunction induced by VEGF, the effects of VEGF on the biophysical characteristics and motility of human mature DCs (mDCs) were investigated. The results showed that VEGF had a negative influence on the biophysical properties, including electrophoretic mobility, osmotic fragility, viscoelasticity, and transmigration. Further cytoskeleton structure analysis by confocal microscope and gene expression profile analyses by gene microarray and real-time PCR indicated that the abnormal remodeling of F-actin cytoskeleton may be the main reason for the deterioration of biophysical properties, motility, and stimulatory capability of VEGF-treated mDCs. This is significant for understanding the biological behavior of DCs and the immune escape mechanism of tumors. Simultaneously, the therapeutic efficacies may be improved by blocking the signaling pathway of VEGF in an appropriate manner before the deployment of DC-based vaccinations against tumors. PMID:27809226

  15. Biophysical Properties and Motility of Human Mature Dendritic Cells Deteriorated by Vascular Endothelial Growth Factor through Cytoskeleton Remodeling.

    PubMed

    Hu, Zu-Quan; Xue, Hui; Long, Jin-Hua; Wang, Yun; Jia, Yi; Qiu, Wei; Zhou, Jing; Wen, Zong-Yao; Yao, Wei-Juan; Zeng, Zhu

    2016-10-31

    Dendritic cells (DCs), the most potent antigen-presenting cells, play a central role in the initiation, regulation, and maintenance of the immune responses. Vascular endothelial growth factor (VEGF) is one of the important cytokines in the tumor microenvironment (TME) and can inhibit the differentiation and functional maturation of DCs. To elucidate the potential mechanisms of DC dysfunction induced by VEGF, the effects of VEGF on the biophysical characteristics and motility of human mature DCs (mDCs) were investigated. The results showed that VEGF had a negative influence on the biophysical properties, including electrophoretic mobility, osmotic fragility, viscoelasticity, and transmigration. Further cytoskeleton structure analysis by confocal microscope and gene expression profile analyses by gene microarray and real-time PCR indicated that the abnormal remodeling of F-actin cytoskeleton may be the main reason for the deterioration of biophysical properties, motility, and stimulatory capability of VEGF-treated mDCs. This is significant for understanding the biological behavior of DCs and the immune escape mechanism of tumors. Simultaneously, the therapeutic efficacies may be improved by blocking the signaling pathway of VEGF in an appropriate manner before the deployment of DC-based vaccinations against tumors.

  16. Semaphorin 3A growth cone collapse requires a sequence homologous to tarantula hanatoxin.

    PubMed

    Behar, O; Mizuno, K; Badminton, M; Woolf, C J

    1999-11-09

    Axonal guidance is key to the formation of neuronal circuitry. Semaphorin 3A (Sema 3A; previously known as semaphorin III, semaphorin D, and collapsin-1), a secreted subtype of the semaphorin family, is an important axonal guidance molecule in vitro and in vivo. The molecular mechanisms of the repellent activity of semaphorins are, however, poorly understood. We have now found that the secreted semaphorins contain a short sequence of high homology to hanatoxin, a tarantula K(+) and Ca(2+) ion channel blocker. Point mutations in the hanatoxin-like sequence of Sema 3A reduce its capacity to repel embryonic dorsal root ganglion axons. Sema 3A growth cone collapse activity is inhibited by hanatoxin, general Ca(2+) channel blockers, a reduction in extracellular or intracellular Ca(2+), and a calmodulin inhibitor, but not by K(+) channel blockers. Our data support an important role for Ca(2+) in mediating the Sema 3A response and suggest that Sema 3A may produce its effects by causing the opening of Ca(2+) channels.

  17. Semaphorin 3A growth cone collapse requires a sequence homologous to tarantula hanatoxin

    PubMed Central

    Behar, Oded; Mizuno, Keiko; Badminton, Mike; Woolf, Clifford J.

    1999-01-01

    Axonal guidance is key to the formation of neuronal circuitry. Semaphorin 3A (Sema 3A; previously known as semaphorin III, semaphorin D, and collapsin-1), a secreted subtype of the semaphorin family, is an important axonal guidance molecule in vitro and in vivo. The molecular mechanisms of the repellent activity of semaphorins are, however, poorly understood. We have now found that the secreted semaphorins contain a short sequence of high homology to hanatoxin, a tarantula K+ and Ca2+ ion channel blocker. Point mutations in the hanatoxin-like sequence of Sema 3A reduce its capacity to repel embryonic dorsal root ganglion axons. Sema 3A growth cone collapse activity is inhibited by hanatoxin, general Ca2+ channel blockers, a reduction in extracellular or intracellular Ca2+, and a calmodulin inhibitor, but not by K+ channel blockers. Our data support an important role for Ca2+ in mediating the Sema 3A response and suggest that Sema 3A may produce its effects by causing the opening of Ca2+ channels. PMID:10557350

  18. Val66Met Polymorphism of BDNF Alters Prodomain Structure to Induce Neuronal Growth Cone Retraction

    PubMed Central

    Anastasia, Agustin; Deinhardt, Katrin; Chao, Moses V.; Will, Nathan E.; Irmady, Krithi; Lee, Francis S.; Hempstead, Barbara L.; Bracken, Clay

    2013-01-01

    A common single-nucleotide polymorphism in the human brain-derived neurotrophic factor (BDNF) gene results in a Val66Met substitution in the BDNF prodomain region. This single-nucleotide polymorphism is associated with alterations in memory and with enhanced risk to develop depression and anxiety disorders in humans. Here we show that the isolated BDNF prodomain is detected in the hippocampus and that it can be secreted from neurons in an activity-dependent manner. Using nuclear magnetic resonance spectroscopy and circular dichroism we find that the prodomain is intrinsically disordered, and the Val66Met substitution induces structural changes. Surprisingly, application of Met66 (but not Val66) BDNF prodomain induces acute growth cone retraction and a decrease in Rac activity in hippocampal neurons. Expression of p75NTR and differential engagement of the Met66 prodomain to the SorCS2 receptor are required for this effect. These results identify the Met66 prodomain as a new active ligand which modulates neuronal morphology. PMID:24048383

  19. LRRK2 guides the actin cytoskeleton at growth cones together with ARHGEF7 and Tropomyosin 4.

    PubMed

    Häbig, Karina; Gellhaar, Sandra; Heim, Birgit; Djuric, Verena; Giesert, Florian; Wurst, Wolfgang; Walter, Carolin; Hentrich, Thomas; Riess, Olaf; Bonin, Michael

    2013-12-01

    Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene represent the most common genetic cause of Parkinson's disease (PD). However, LRRK2 function and molecular mechanisms causing the parkinsonian phenotype remain widely unknown. Most of LRRK2 knockdown and overexpression models strengthen the relevance of LRRK2 in regulating neurite outgrowth. We have recently identified ARHGEF7 as the first guanine nucleotide exchange factor (GEF) of LRRK2. This GEF is influencing neurite outgrowth through regulation of actin polymerization. Here, we examined the expression profile of neuroblastoma cells with reduced LRRK2 and ARHGEF7 levels to identify additional partners of LRRK2 in this process. Tropomyosins (TPMs), and in particular TPM4, were the most interesting candidates next to other actin cytoskeleton regulating transcripts in this dataset. Subsequently, enhanced neurite branching was shown using primary hippocampal neurons of LRRK2 knockdown animals. Furthermore, we observed an enhanced number of growth cones per neuron and a mislocalization and dysregulation of ARHGEF7 and TPM4 in these neuronal compartments. Our results reveal a fascinating connection between the neurite outgrowth phenotype of LRRK2 models and the regulation of actin polymerization directing further investigations of LRRK2-related pathogenesis.

  20. Amplification and Temporal Filtering during Gradient Sensing by Nerve Growth Cones Probed with a Microfluidic Assay

    PubMed Central

    Morel, Mathieu; Shynkar, Vasyl; Galas, Jean-Christophe; Dupin, Isabelle; Bouzigues, Cedric; Studer, Vincent; Dahan, Maxime

    2012-01-01

    Nerve growth cones (GCs) are chemical sensors that convert graded extracellular cues into oriented axonal motion. To ensure a sensitive and robust response to directional signals in complex and dynamic chemical landscapes, GCs are presumably able to amplify and filter external information. How these processing tasks are performed remains however poorly known. Here, we probe the signal-processing capabilities of single GCs during γ-Aminobutyric acid (GABA) directional sensing with a shear-free microfluidic assay that enables systematic measurements of the GC output response to variable input gradients. By measuring at the single molecule level the polarization of GABAA chemoreceptors at the GC membrane, as a function of the external GABA gradient, we find that GCs act as i), signal amplifiers over a narrow range of concentrations, and ii), low-pass temporal filters with a cutoff frequency independent of stimuli conditions. With computational modeling, we determine that these systems-level properties arise at a molecular level from the saturable occupancy response and the lateral dynamics of GABAA receptors. PMID:23083707

  1. An Automated Strategy for Unbiased Morphometric Analyses and Classifications of Growth Cones In Vitro

    PubMed Central

    Chitsaz, Daryan; Morales, Daniel; Law, Chris; Kania, Artur

    2015-01-01

    During neural circuit development, attractive or repulsive guidance cue molecules direct growth cones (GCs) to their targets by eliciting cytoskeletal remodeling, which is reflected in their morphology. The experimental power of in vitro neuronal cultures to assay this process and its molecular mechanisms is well established, however, a method to rapidly find and quantify multiple morphological aspects of GCs is lacking. To this end, we have developed a free, easy to use, and fully automated Fiji macro, Conographer, which accurately identifies and measures many morphological parameters of GCs in 2D explant culture images. These measurements are then subjected to principle component analysis and k-means clustering to mathematically classify the GCs as “collapsed” or “extended”. The morphological parameters measured for each GC are found to be significantly different between collapsed and extended GCs, and are sufficient to classify GCs as such with the same level of accuracy as human observers. Application of a known collapse-inducing ligand results in significant changes in all parameters, resulting in an increase in ‘collapsed’ GCs determined by k-means clustering, as expected. Our strategy provides a powerful tool for exploring the relationship between GC morphology and guidance cue signaling, which in particular will greatly facilitate high-throughput studies of the effects of drugs, gene silencing or overexpression, or any other experimental manipulation in the context of an in vitro axon guidance assay. PMID:26496644

  2. Natural plant products inhibits growth and alters the swarming motility, biofilm formation, and expression of virulence genes in enteroaggregative and enterohemorrhagic Escherichia coli.

    PubMed

    García-Heredia, Alam; García, Santos; Merino-Mascorro, José Ángel; Feng, Peter; Heredia, Norma

    2016-10-01

    The purpose of this study was to determine the effects of plant products on the growth, swarming motility, biofilm formation and virulence gene expression in enterohemorrhagic Escherichia coli O157:H7 and enteroaggregative E. coli strain 042 and a strain of O104:H4 serotype. Extracts of Lippia graveolens and Haematoxylon brassiletto, and carvacrol, brazilin were tested by an antimicrobial microdilution method using citral and rifaximin as controls. All products showed bactericidal activity with minimal bactericidal concentrations ranging from 0.08 to 8.1 mg/ml. Swarming motility was determined in soft LB agar. Most compounds reduced swarming motility by 7%-100%; except carvacrol which promoted motility in two strains. Biofilm formation studies were done in microtiter plates. Rifaximin inhibited growth and reduced biofilm formation, but various concentrations of other compounds actually induced biofilm formation. Real time PCR showed that most compounds decreased stx2 expression. The expression of pic and rpoS in E. coli 042 were suppressed but in E. coli O104:H4 they varied depending on compounds. In conclusion, these extracts affect E. coli growth, swarming motility and virulence gene expression. Although these compounds were bactericidal for pathogenic E. coli, sublethal concentrations had varied effects on phenotypic and genotypic traits, and some increased virulence gene expression.

  3. Control of cell motility by interaction of gangliosides, tetraspanins, and epidermal growth factor receptor in A431 versus KB epidermoid tumor cells.

    PubMed

    Park, Seung-Yeol; Yoon, Seon-Joo; Freire-de-Lima, Leonardo; Kim, Jung-Hoe; Hakomori, Sen-itiroh

    2009-08-17

    Growth of epidermoid carcinoma cell lines, A431 and KB, has been known to be controlled by the interaction of epidermal growth factor (EGF) and its receptor (EGFR) with tyrosine kinase. Ganglioside GM3 was previously found to interact with EGFR and to inhibit EGFR tyrosine kinase. However, motility of these cells, controlled by EGFR and ganglioside, was not studied. The present study is focused on the control mechanism of the motility of these cells through interaction of ganglioside, tetraspanin (TSP), and EGFR. Key results are as follows: (i) The level of EGFR expressed in A431 cells is approximately 6 times higher than that expressed in KB cells, and motility of A431 cells is also much higher than that of KB cells, yet growth of A431 cells is either not affected or is inhibited by EGF. In contrast, growth of KB cells is enhanced by EGF. (ii) Levels of TSPs (CD9, CD82, and CD81) expressed in A431 cells are much higher than those expressed in KB cells, and TSPs expressed in A431 cells are reduced by treatment of cells with EtDO-P4, which inhibits the synthesis of glycosphingolipids (GSLs) and gangliosides. (iii) These TSPs are co-immunoprecipitated with EGFR in both A431 and KB cells, indicating that TSPs are closely associated with EGFR. (iv) High motility of A431 cells is greatly reduced, while low motility of KB cells is not affected, by treatment of cells with EtDO-P4. These results, taken together, suggest that there is a close correlation between high motility of A431 cells and high expression of EGFR and TSPs, and between ganglioside GM3/GM2 and TSP. A similar correlation was suggested between the low motility of KB cells and low levels of EGFR and TSP. The correlation between high motility and high level of EGFR with the ganglioside-TSP complex in A431 cells is unique. This is in contrast to our previous studies that indicate that motility of many types of tumor cells is inhibited by a high level of CD9 or CD82, together with growth factor receptors and

  4. Ganglioside GD3 monoclonal antibody-induced paxillin tyrosine phosphorylation and filamentous actin assembly in cerebellar growth cones.

    PubMed

    Yuyama, Kohei; Sekino-Suzuki, Naoko; Yamamoto, Naomasa; Kasahara, Kohji

    2011-03-01

    We have demonstrated that antibody to ganglioside GD3 (R24) immunoprecipitates src-family tyrosine kinase Lyn from primary cerebellar granule cells and R24 treatment of the intact cells induces Lyn activation and rapid tyrosine phosphorylation of several substrates, suggesting the functional association of ganglioside GD3 with Lyn. In this study, R24 treatment of primary cerebellar granule cells enhances phosphorylation of paxillin at tyrosine residue 118 and induces filamentous actin assembly and neurite outgrowth. R24 treatment of cerebellar growth cone membrane fraction induces prominent tyrosine phosphorylation of 68 kDa protein which comigrates with phosphopaxillin at tyrosine residue 118. Tyrosine phosphorylation of paxillin is known to regulate actin cytoskeleton-dependent changes in cell morphology. Signal transduction by ganglioside GD3 is involved in growth cone morphology via tyrosine phosphorylation of paxillin. © 2011 The Authors. Journal of Neurochemistry © 2011 International Society for Neurochemistry.

  5. A molecular recognizing system of serotonin in rat fetal axonal growth cones: uptake and high affinity binding.

    PubMed

    Mercado, R; Hernández, J

    1992-09-18

    Axonal growth cone particles (AGCP) isolated from prenatal and postnatal rat brain had different high-affinity 5-HT uptake characteristics. In postnatal AGCP the uptake behaves as in the adult rat brain, while in the prenatal AGCP the uptake characteristics seem to be in a transitional stage. Also in prenatal AGCP we observed specific, high-affinity 5-HT binding sites. These results support the idea of an important role for 5-HT during axogenesis.

  6. The in vitro effect of prolactin on the growth, motility and expression of prolactin receptors in larvae of Toxocara canis.

    PubMed

    Chávez-Güitrón, L E; Morales-Montor, J; Muñoz-Guzmán, M A; Nava-Castro, K E; Ramírez-Álvarez, H; Moreno-Méndoza, N A; Hernández-Cervantes, R; Alba-Hurtado, F

    2016-07-15

    The in vitro effect of prolactin (PRL) on the growth and motility of Toxocara canis larvae was assessed. Additionally, the expression and location of prolactin receptors (PRL-Rs) were determined in the larvae. Larvae of T. canis were incubated with different concentrations of PRL for different periods of time. The stimulated larvae accelerated their enlargement and increased their motility. The mean percentage of PRL-R+ cells in non-stimulated larvae, measured by flow cytometry was 7.3±0.3%. Compared with non-stimulated larvae, the mean fluorescence intensity (p<0.05) increased in larvae incubated with 40ng/mL of PRL for 10 days. A 465-bp length fragment was amplified from larvae gDNA by PCR. The sequence of this fragment showed 99% similarity with the gene fragment that codes for the PRL-R of the domestic dog. A high concentration of PRL-Rs was immune-located in the posterior region of the larval intestine; therefore, the intestinal cells in this region were most likely the targets for this hormone. Based on these results, PRL-Rs were identified in T. canis larvae, and the in vitro stimulation with PRL increased the number of these receptors, accelerated the growth and modified the activity of larvae. All of the above suggest that T. canis larvae are evolutionarily adapted to recognize the PRL of their definitive host and furthermore might explain the reactivation of tissue-arrested larvae during the gestation of bitches, which does not occur in gestating females of other species.

  7. Regulation of neurite outgrowth mediated by neuronal calcium sensor-1 and inositol 1,4,5-trisphosphate receptor in nerve growth cones.

    PubMed

    Iketani, M; Imaizumi, C; Nakamura, F; Jeromin, A; Mikoshiba, K; Goshima, Y; Takei, K

    2009-07-07

    Calcium acts as an important second messenger in the intracellular signal pathways in a variety of cell functions. Strictly controlled intracellular calcium is required for proper neurite outgrowth of developing neurons. However, the molecular mechanisms of this process are still largely unknown. Neuronal calcium sensor-1 (NCS-1) is a high-affinity and low-capacity calcium binding protein, which is specifically expressed in the nervous system. NCS-1 was distributed throughout the entire region of growth cones located at a distal tip of neurite in cultured chick dorsal root ganglion neurons. In the central domain of the growth cone, however, NCS-1 was distributed in a clustered specific pattern and co-localized with the type 1 inositol 1,4,5-trisphosphate receptor (InsP(3)R1). The pharmacological inhibition of InsP(3) receptors decreased the clustered specific distribution of NCS-1 in the growth cones and inhibited neurite outgrowth but did not change the growth cone morphology. The acute and localized loss of NCS-1 function in the growth cone induced by chromophore-assisted laser inactivation (CALI) resulted in the growth arrest of neurites and lamellipodial and filopodial retractions. These findings suggest that NCS-1 is involved in the regulation of both neurite outgrowth and growth cone morphology. In addition, NCS-1 is functionally linked to InsP(3)R1, which may play an important role in the regulation of neurite outgrowth.

  8. Novel inhibitory action of tunicamycin homologues suggests a role for dynamic protein fatty acylation in growth cone-mediated neurite extension

    PubMed Central

    1994-01-01

    In neuronal growth cones, the advancing tips of elongating axons and dendrites, specific protein substrates appear to undergo cycles of posttranslational modification by covalent attachment and removal of long-chain fatty acids. We show here that ongoing fatty acylation can be inhibited selectively by long-chain homologues of the antibiotic tunicamycin, a known inhibitor of N-linked glycosylation. Tunicamycin directly inhibits transfer of palmitate to protein in a cell-free system, indicating that tunicamycin inhibition of protein palmitoylation reflects an action of the drug separate from its previously established effects on glycosylation. Tunicamycin treatment of differentiated PC12 cells or dissociated rat sensory neurons, under conditions in which protein palmitoylation is inhibited, produces a prompt cessation of neurite elongation and induces a collapse of neuronal growth cones. These growth cone responses are rapidly reversed by washout of the antibiotic, even in the absence of protein synthesis, or by addition of serum. Two additional lines of evidence suggest that the effects of tunicamycin on growth cones arise from its ability to inhibit protein long-chain acylation, rather than its previously established effects on protein glycosylation and synthesis. (a) The abilities of different tunicamycin homologues to induce growth cone collapse very systematically with the length of the fatty acyl side- chain of tunicamycin, in a manner predicted and observed for the inhibition of protein palmitoylation. Homologues with fatty acyl moieties shorter than palmitic acid (16 hydrocarbons), including potent inhibitors of glycosylation, are poor inhibitors of growth cone function. (b) The tunicamycin-induced impairment of growth cone function can be reversed by the addition of excess exogenous fatty acid, which reverses the inhibition of protein palmitoylation but has no effect on the inhibition of protein glycosylation. These results suggest an important role for

  9. Temporally and spatially coordinated roles for Rho, Rac, Cdc42 and their effectors in growth cone guidance by a physiological electric field.

    PubMed

    Rajnicek, Ann M; Foubister, Louise E; McCaig, Colin D

    2006-05-01

    Although it is known that neuronal growth cones migrate towards the cathode of an applied direct current (DC) electric field (EF), resembling the EF present in the developing nervous system, the underlying mechanism remains unclear. Here, we demonstrate temporally and spatially coordinated roles for the GTPases Rac, Cdc42 and Rho and their effectors. Growth cones of cultured Xenopus embryonic spinal neurons turned towards the cathode but collective inhibition of Rho, Rac and Cdc42 attenuated turning. Selective inhibition of Rho, Cdc42 or Rac signalling revealed temporally distinct roles in steering by an electrical gradient. Rho, Rac and Cdc42 are each essential for turning within the initial 2 hours (early phase). Later, Rho and Cdc42 signals remain important but Rac signalling dominates. The EF increased Rho immunofluorescence anodally. This correlated spatially with collapsed growth cone morphology and reduced anodal migration rates, which were restored by Rho inhibition. These data suggest that anodally increased Rho activity induces local cytoskeletal collapse, biasing growth cone advance cathodally. Collapse might be mediated by the Rho effectors p160 Rho kinase and myosin light chain kinase since their inhibition attenuated early turning. Inhibitors of phosphoinositide 3-kinase, MEK1/2 or p38 mitogen-activated protein kinase (MAPK) did not affect turning behaviour, eliminating them mechanistically. We propose a mechanism whereby Rac and Cdc42 activities dominate cathodally and Rho activity dominates anodally to steer growth cones towards the cathode. The interaction between Rho GTPases, the cytoskeleton and growth cone dynamics is explored in the companion paper published in this issue. Our results complement studies of growth cone guidance by diffusible chemical gradients and suggest that growth cones might interpret these co-existing guidance cues selectively.

  10. Functional role of glycosphingolipids and gangliosides in control of cell adhesion, motility, and growth, through glycosynaptic microdomains.

    PubMed

    Regina Todeschini, Adriane; Hakomori, Sen-itiroh

    2008-03-01

    At cell surface microdomains, glycosyl epitopes, carried either by glycosphingolipids, N- or O-linked oligosaccharides, are recognized by carbohydrate-binding proteins or complementary carbohydrates. In both cases, the carbohydrate epitopes may be clustered with specific signal transducers, tetraspanins, adhesion receptors or growth factor receptors. Through this framework, carbohydrates can mediate cell signaling leading to changes in cellular phenotype. Microdomains involved in carbohydrate-dependent cell adhesion inducing cell activation, motility, and growth are termed "glycosynapse". In this review a historical synopsis of glycosphingolipids-enriched microdomains study leading to the concept of glycosynapse is presented. Examples of glycosynapse as signaling unit controlling the tumor cell phenotype are discussed in three contexts: (i) Cell-to-cell adhesion mediated by glycosphingolipids-to-glycosphingolipids interaction between interfacing glycosynaptic domains, through head-to-head (trans) carbohydrate-to-carbohydrate interaction. (ii) Functional role of GM3 complexed with tetraspanin CD9, and interaction of such complex with integrins, or with fibroblast growth factor receptor, to control tumor cell phenotype and its reversion to normal cell phenotype. (iii) Inhibition of integrin-dependent Met kinase activity by GM2/tetraspanin CD82 complex in glycosynaptic microdomain. Data present here suggest that the organizational status of glycosynapse strongly affects cellular phenotype influencing tumor cell malignancy.

  11. WAVE2-Abi2 complex controls growth cone activity and regulates the multipolar-bipolar transition as well as the initiation of glia-guided migration.

    PubMed

    Xie, Min-Jue; Yagi, Hideshi; Kuroda, Kazuki; Wang, Chen-Chi; Komada, Munekazu; Zhao, Hong; Sakakibara, Akira; Miyata, Takaki; Nagata, Koh-Ichi; Oka, Yuichiro; Iguchi, Tokuichi; Sato, Makoto

    2013-06-01

    Glia-guided migration (glia-guided locomotion) during radial migration is a characteristic yet unique mode of migration. In this process, the directionality of migration is predetermined by glial processes and not by growth cones. Prior to the initiation of glia-guided migration, migrating neurons transform from multipolar to bipolar, but the molecular mechanisms underlying this multipolar-bipolar transition and the commencement of glia-guided migration are not fully understood. Here, we demonstrate that the multipolar-bipolar transition is not solely a cell autonomous event; instead, the interaction of growth cones with glial processes plays an essential role. Time-lapse imaging with lattice assays reveals the importance of vigorously active growth cones in searching for appropriate glial scaffolds, completing the transition, and initiating glia-guided migration. These growth cone activities are regulated by Abl kinase and Cdk5 via WAVE2-Abi2 through the phosphorylation of tyrosine 150 and serine 137 of WAVE2. Neurons that do not display such growth cone activities are mispositioned in a more superficial location in the neocortex, suggesting the significance of growth cones for the final location of the neurons. This process occurs in spite of the "inside-out" principle in which later-born neurons are situated more superficially.

  12. ECM Composition and Rheology Regulate Growth, Motility, and Response to Photodynamic Therapy in 3D Models of Pancreatic Ductal Adenocarcinoma.

    PubMed

    Cramer, Gwendolyn M; Jones, Dustin P; El-Hamidi, Hamid; Celli, Jonathan P

    2017-01-01

    Pancreatic ductal adenocarcinoma is characterized by prominent stromal involvement, which plays complex roles in regulating tumor growth and therapeutic response. The extracellular matrix (ECM)-rich stroma associated with this disease has been implicated as a barrier to drug penetration, although stromal depletion strategies have had mixed clinical success. It remains less clear how interactions with ECM, acting as a biophysical regulator of phenotype, not only a barrier to drug perfusion, regulate susceptibilities and resistance to specific therapies. In this context, an integrative approach is used to evaluate invasive behavior and motility in rheologically characterized ECM as determinants of chemotherapy and photodynamic therapy (PDT) responses. We show that in 3D cultures with ECM conditions that promote invasive progression, response to PDT is markedly enhanced in the most motile ECM-infiltrating populations, whereas the same cells exhibit chemoresistance. Conversely, drug-resistant sublines with enhanced invasive potential were generated to compare differential treatment response in identical ECM conditions, monitored by particle tracking microrheology measurements of matrix remodeling. In both scenarios, ECM-infiltrating cell populations exhibit increased sensitivity to PDT, whether invasion is consequent to selection of chemoresistance, or whether chemoresistance is correlated with acquisition of invasive behavior. However, while ECM-invading, chemoresistant cells exhibit mesenchymal phenotype, induction of EMT in monolayers without ECM was not sufficient to enhance PDT sensitivity, yet does impart chemoresistance as expected. In addition to containing platform development with broader applicability to inform microenvironment-dependent therapeutics, these results reveal the efficacy of PDT for targeting the most aggressive, chemoresistant, invasive pancreatic ductal adenocarcinoma associated with dismal outcomes for this disease.

  13. Cell motility and ECM proteolysis regulate tumor growth and tumor relapse by altering the fraction of cancer stem cells and their spatial scattering

    NASA Astrophysics Data System (ADS)

    Kumar, Sandeep; Kulkarni, Rahul; Sen, Shamik

    2016-06-01

    Tumors consist of multiple cell sub-populations including cancer stem cells (CSCs), transiently amplifying cells and terminally differentiated cells (TDCs), with the CSC fraction dictating the aggressiveness of the tumor and drug sensitivity. In epithelial cancers, tumor growth is influenced greatly by properties of the extracellular matrix (ECM), with cancer progression associated with an increase in ECM density. However, the extent to which increased ECM confinement induced by an increase in ECM density influences tumor growth and post treatment relapse dynamics remains incompletely understood. In this study, we use a cellular automata-based discrete modeling approach to study the collective influence of ECM density, cell motility and ECM proteolysis on tumor growth, tumor heterogeneity, and tumor relapse after drug treatment. We show that while increased confinement suppresses tumor growth and the spatial scattering of CSCs, this effect can be reversed when cells become more motile and proteolytically active. Our results further suggest that, in addition to the absolute number of CSCs, their spatial positioning also plays an important role in driving tumor growth. In a nutshell, our study suggests that, in confined environments, cell motility and ECM proteolysis are two key factors that regulate tumor growth and tumor relapse dynamics by altering the number and spatial distribution of CSCs.

  14. Cell motility and ECM proteolysis regulate tumor growth and tumor relapse by altering the fraction of cancer stem cells and their spatial scattering.

    PubMed

    Kumar, Sandeep; Kulkarni, Rahul; Sen, Shamik

    2016-04-29

    Tumors consist of multiple cell sub-populations including cancer stem cells (CSCs), transiently amplifying cells and terminally differentiated cells (TDCs), with the CSC fraction dictating the aggressiveness of the tumor and drug sensitivity. In epithelial cancers, tumor growth is influenced greatly by properties of the extracellular matrix (ECM), with cancer progression associated with an increase in ECM density. However, the extent to which increased ECM confinement induced by an increase in ECM density influences tumor growth and post treatment relapse dynamics remains incompletely understood. In this study, we use a cellular automata-based discrete modeling approach to study the collective influence of ECM density, cell motility and ECM proteolysis on tumor growth, tumor heterogeneity, and tumor relapse after drug treatment. We show that while increased confinement suppresses tumor growth and the spatial scattering of CSCs, this effect can be reversed when cells become more motile and proteolytically active. Our results further suggest that, in addition to the absolute number of CSCs, their spatial positioning also plays an important role in driving tumor growth. In a nutshell, our study suggests that, in confined environments, cell motility and ECM proteolysis are two key factors that regulate tumor growth and tumor relapse dynamics by altering the number and spatial distribution of CSCs.

  15. Effect of tannic and gallic acids alone or in combination with carbenicillin or tetracycline on Chromobacterium violaceum CV026 growth, motility, and biofilm formation.

    PubMed

    Dusane, Devendra H; O'May, Che; Tufenkji, Nathalie

    2015-07-01

    Chromobacterium violaceum is an opportunistic pathogen that causes infections that are difficult to treat. The goal of this research was to evaluate the effect of selected tannins (tannic acid (TA) and gallic acid (GA)) on bacterial growth, motility, antibiotic (carbenicillin, tetracycline) susceptibility, and biofilm formation. Both tannins, particularly TA, impaired bacterial growth levels and swimming motilities at sub-minimum inhibitory concentrations (sub-MICs). In combination with tannins, antibiotics showed increased MICs, suggesting that tannins interfered with antibacterial activity. Sub-MICs of tetracycline or TA alone enhanced biofilm formation of C. violaceum; however, in combination, these compounds inhibited biofilm formation. In contrast, carbenicillin at sub-MICs was effective in inhibiting C. violaceum biofilm formation; however, in combination with lower concentrations of TA or GA, biofilms were enhanced. These results provide insights into the effects of tannins on C. violaceum growth and their varying interaction with antibiotics used to target C. violaceum infections.

  16. Secreted or nonsecreted forms of acidic fibroblast growth factor produced by transfected epithelial cells influence cell morphology, motility, and invasive potential.

    PubMed Central

    Jouanneau, J; Gavrilovic, J; Caruelle, D; Jaye, M; Moens, G; Caruelle, J P; Thiery, J P

    1991-01-01

    Addition of exogenous acidic fibroblast growth factor (aFGF) to NBT-II epithelial carcinoma cells results in fibroblastic transformation and cell motility. We have generated aFGF-producing NBT-II cells by transfection with recombinant expression vectors containing human aFGF cDNA, or the human aFGF cDNA coupled to a signal peptide (SP) sequence. The effects of the nonsecreted and the secreted 16-kDa growth factor on the morphology, motility, and cell invasive potential (gelatinase activity) were compared. aFGF coupled to a SP was actively secreted out of the producing cells. The secretion of aFGF was not necessary for induction of gelatinase activity, as this was observed in NBT-II cells producing aFGF with or without SP. Production of aFGF, whether secreted or not secreted, resulted in increased in vitro motility of most isolated clones; however, there was no correlation between aFGF level and motility rate. The data suggest that expression of aFGF in NBT-II cells induces metastatic potential through an autocrine or intracrine mechanism. Images PMID:1707175

  17. Faster voltage-dependent activation of Na+ channels in growth cones versus somata of neuroblastoma N1E-115 cells.

    PubMed Central

    Zhang, J; Loew, L M; Davidson, R M

    1996-01-01

    Kinetics of voltage-gated ionic channels fundamentally reflect the response of the channels to local electric fields. In this report cell-attached patch-clamp studies reveal that the voltage-dependent activation rate of sodium channels residing in the growth cone membrane differs from that of soma sodium channels in differentiating N1E-115 neuroblastoma cells. Because other electrophysiological properties of these channels do not differ, this finding may be a reflection of the difference in intramembrane electric field in these two regions of the cell. This represents a new mechanism for channels to attain a range of activities both within and between cells. PMID:8913589

  18. Cytoskeletal social networking in the growth cone: how +TIPs mediate microtubule-actin cross-linking to drive axon outgrowth and guidance

    PubMed Central

    Cammarata, Garrett M.; Bearce, Elizabeth A.; Lowery, Laura Anne

    2016-01-01

    The growth cone is a unique structure capable of guiding axons to their proper destinations. Within the growth cone, extracellular guidance cues are interpreted and then transduced into physical changes in the actin filament (F-actin) and microtubule cytoskeletons, providing direction and movement. While both cytoskeletal networks individually possess important growth cone-specific functions, recent data over the past several years point towards a more cooperative role between the two systems. Facilitating this interaction between F-actin and microtubules, microtubule plus-end tracking proteins (+TIPs) have been shown to link the two cytoskeletons together. Evidence suggests that many +TIPs can couple microtubules to F-actin dynamics, supporting both microtubule advance and retraction in the growth cone periphery. In addition, growing in vitro and in vivo data support a secondary role for +TIPs in which they may participate as F-actin nucleators, thus directly influencing F-actin dynamics and organization. This review focuses on how +TIPs may link F-actin and microtubules together in the growth cone, and how these interactions may influence axon guidance. PMID:26783725

  19. Frazzled promotes growth cone attachment at the source of a Netrin gradient in the Drosophila visual system

    PubMed Central

    Akin, Orkun; Zipursky, S Lawrence

    2016-01-01

    Axon guidance is proposed to act through a combination of long- and short-range attractive and repulsive cues. The ligand-receptor pair, Netrin (Net) and Frazzled (Fra) (DCC, Deleted in Colorectal Cancer, in vertebrates), is recognized as the prototypical effector of chemoattraction, with roles in both long- and short-range guidance. In the Drosophila visual system, R8 photoreceptor growth cones were shown to require Net-Fra to reach their target, the peak of a Net gradient. Using live imaging, we show, however, that R8 growth cones reach and recognize their target without Net, Fra, or Trim9, a conserved binding partner of Fra, but do not remain attached to it. Thus, despite the graded ligand distribution along the guidance path, Net-Fra is not used for chemoattraction. Based on findings in other systems, we propose that adhesion to substrate-bound Net underlies both long- and short-range Net-Fra-dependent guidance in vivo, thereby eroding the distinction between them. DOI: http://dx.doi.org/10.7554/eLife.20762.001 PMID:27743477

  20. Epidermal growth factor promotes a mesenchymal over an amoeboid motility of MDA-MB-231 cells embedded within a 3D collagen matrix

    NASA Astrophysics Data System (ADS)

    Geum, Dongil T.; Kim, Beum Jun; Chang, Audrey E.; Hall, Matthew S.; Wu, Mingming

    2016-01-01

    The receptor of epidermal growth factor (EGFR) critically regulates tumor cell invasion and is a potent therapeutic target for treatment of many types of cancers, including carcinomas and glioblastomas. It is known that EGF regulates cell motility when tumor cells are embedded within a 3D biomatrix. However, roles of EGF in modulating tumor cell motility phenotype are largely unknown. In this article, we report that EGF promotes a mesenchymal over an amoeboid motility phenotype using a malignant breast tumor cell line, MDA-MB-231, embedded within a 3D collagen matrix. Amoeboid cells are rounded in shape, while mesenchymal cells are elongated, and their migrations are governed by a distinctly different set of biomolecules. Using single cell tracking analysis, we also show that EGF promotes cell dissemination through a significant increase in cell persistence along with a moderate increase of speed. The increase of persistence is correlated with the increase of the percentage of the mesenchymal cells within the population. Our work reveals a novel role of microenvironmental cue, EGF, in modulating heterogeneity and plasticity of tumor cell motility phenotype. In addition, it suggests a potential visual cue for diagnosing invasive states of breast cancer cells. This work can be easily extended beyond breast cancer cells.

  1. Cold knife cone biopsy

    MedlinePlus

    ... biopsy; Pap smear - cone biopsy; HPV - cone biopsy; Human papilloma virus - cone biopsy; Cervix - cone biopsy; Colposcopy - cone biopsy Images Female reproductive anatomy Cold cone biopsy Cold cone removal References American ...

  2. Learn About GI Motility

    MedlinePlus

    ... Disorders of the Large Intestine Disorders of the Pelvic Floor Motility Testing Personal Stories Contact About GI Motility ... Disorders of the Large Intestine Disorders of the Pelvic Floor Motility Testing Personal Stories Contact About GI Motility ...

  3. About GI Motility

    MedlinePlus

    ... Disorders of the Large Intestine Disorders of the Pelvic Floor Motility Testing Personal Stories Contact About GI Motility ... Disorders of the Large Intestine Disorders of the Pelvic Floor Motility Testing Personal Stories Contact About GI Motility ...

  4. Biochemical properties of Na+/K(+)-ATPase in axonal growth cone particles isolated from fetal rat brain.

    PubMed

    Mercado, R; Hernández, J

    1994-08-01

    Axonal growth cones (AGC) isolated from fetal rat brain have an important specific activity of N+/K(+)-ATPase. Kinetic assays of the enzyme in AGC showed that Km values for ATP or K+ are similar to those reported for the adult brain enzyme. For Na+ the affinity (Km) was lower. Vmax for the three substrates was several times lower in AGC as compared to the adult value. We also observed two apparent inhibition constants of Na+/K(+)-ATPase by ouabain, one of low affinity, possibly corresponding to the alpha 1 isoform and another of high affinity which is different to that described for the alpha 2 isoform of the enzyme. These results support an important role for the sodium pump in the maintainance of volume and cationic balance in neuronal differentiating structures. The functional differences observed also suggest that the enzymatic complex of Na+/K(+)-ATPase in AGC is in a transitional state towards the adult configuration.

  5. Three-dimensional longitudinal changes in craniofacial growth in untreated hemifacial microsomia patients with cone-beam computed tomography.

    PubMed

    Shibazaki-Yorozuya, Reiko; Yamada, Akira; Nagata, Satoru; Ueda, Kouichi; Miller, Arthur J; Maki, Koutaro

    2014-05-01

    The purpose of this study was to evaluate the concept that the affected and contralateral sides do not grow at the same rate in patients with hemifacial microsomia. Changes in the cranial base, maxilla, mandible, and occlusal plane were evaluated on 3-dimensional images from cone-beam computed tomography data in untreated patients. Six patients were classified as having mandibular Pruzansky/Kaban type I, IIA, or IIB hemifacial microsomia. Cone-beam computed tomography (MercuRay; Hitachi, Tokyo, Japan) scans were taken before orthodontic treatment during both growth and postpuberty periods. The cranial base as defined by the position of the mastoid process was in a different position between the affected and contralateral control sides. The nasomaxillary length or height was shorter on the affected side for all 6 patients with hemifacial microsomia regardless of its severity, and it grew less than on the contralateral control side in 5 of the 6 patients. The occlusal plane angle became more inclined in 4 of the 6 patients. The mandibular ramus was shorter on the affected side in all patients and grew less on the affected side in 5 of the 6 patients. The mandibular body grew slower, the same, or faster than on the control side. The cranial base, position of the condyle, lengths of the condyle and ramus, and positions of the gonial angle and condyle can vary between the affected and contralateral control sides of patients with hemifacial microsomia, with the ramus and nasomaxillary length usually growing slower than they grow on the control side. These results suggest that many factors affect the growth rate of the craniofacial region and, specifically, the mandible in patients with hemifacial microsomia. Copyright © 2014 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

  6. Semaphorin 3A activates the guanosine triphosphatase Rab5 to promote growth cone collapse and organize callosal axon projections

    PubMed Central

    Wu, Kong-Yan; He, Miao; Hou, Qiong-Qiong; Sheng, Ai-Li; Yuan, Lei; Liu, Fei; Liu, Wen-Wen; Li, Guangpu; Jiang, Xing-Yu; Luo, Zhen-Ge

    2015-01-01

    Axon guidance (pathfinding) wires the brain during development and is regulated by various attractive and repulsive cues. Semaphorin 3A (Sema3A) is a repulsive cue, inducing the collapse of axon growth cones. In the mammalian forebrain, the corpus callosum is the major commissure that transmits information flow between the two hemispheres, and contralateral axons assemble into well-defined tracts. We found that the patterning of callosal axon projections in rodent layer II and III (L2/3) cortical neurons in response to Sema3A was mediated by the activation of Rab5, a small guanosine triphosphatase (GTPase) that mediates endocytosis, through the membrane fusion protein Rabaptin-5 and the Rab5 guanine nucleotide exchange factor (GEF) Rabex-5. Rabaptin-5 bound directly to Plexin-A1 in the Sema3A receptor complex [an obligate heterodimer formed by Plexin-A1 and neuropilin 1 (NP1)]; Sema3A enhanced this interaction in cultured neurons. Rabaptin-5 bridged the interaction between Rab5 and Plexin-A1. Sema3A stimulated endocytosis from the cell surface of callosal axon growth cones. In utero electroporation to reduce Rab5 or Rabaptin-5 impaired axon fasciculation or caused mistargeting of L2/3 callosal projections in rats. Over-expression of Rabaptin-5 or Rab5 rescued the defective callosal axon fasciculation or mistargeting of callosal axons caused by the loss of Sema3A–Plexin-A1 signaling in rats expressing dominant-negative Plexin-A1 or in NP1-deficient mice. Thus, our findings suggest that Rab5, its effector Rabaptin-5, and its regulator Rabex-5 mediate Sema3A-induced axon guidance during brain development. PMID:25161316

  7. A signaling mechanism coupling netrin-1/deleted in colorectal cancer chemoattraction to SNARE-mediated exocytosis in axonal growth cones.

    PubMed

    Cotrufo, Tiziana; Pérez-Brangulí, Francesc; Muhaisen, Ashraf; Ros, Oriol; Andrés, Rosa; Baeriswyl, Thomas; Fuschini, Giulia; Tarrago, Teresa; Pascual, Marta; Ureña, Jesús; Blasi, Joan; Giralt, Ernest; Stoeckli, Esther T; Soriano, Eduardo

    2011-10-12

    Directed cell migration and axonal guidance are essential steps in neural development. Both processes are controlled by specific guidance cues that activate the signaling cascades that ultimately control cytoskeletal dynamics. Another essential step in migration and axonal guidance is the regulation of plasmalemma turnover and exocytosis in leading edges and growth cones. However, the cross talk mechanisms linking guidance receptors and membrane exocytosis are not understood. Netrin-1 is a chemoattractive cue required for the formation of commissural pathways. Here, we show that the Netrin-1 receptor deleted in colorectal cancer (DCC) forms a protein complex with the t-SNARE (target SNARE) protein Syntaxin-1 (Sytx1). This interaction is Netrin-1 dependent both in vitro and in vivo, and requires specific Sytx1 and DCC domains. Blockade of Sytx1 function by using botulinum toxins abolished Netrin-1-dependent chemoattraction of axons in mouse neuronal cultures. Similar loss-of-function experiments in the chicken spinal cord in vivo using dominant-negative Sytx1 constructs or RNAi led to defects in commissural axon pathfinding reminiscent to those described in Netrin-1 and DCC loss-of-function models. We also show that Netrin-1 elicits exocytosis at growth cones in a Sytx1-dependent manner. Moreover, we demonstrate that the Sytx1/DCC complex associates with the v-SNARE (vesicle SNARE) tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP) and that knockdown of TI-VAMP in the commissural pathway in the spinal cord results in aberrant axonal guidance phenotypes. Our data provide evidence of a new signaling mechanism that couples chemotropic Netrin-1/DCC axonal guidance and Sytx1/TI-VAMP SNARE proteins regulating membrane turnover and exocytosis.

  8. A microfluidics-based turning assay reveals complex growth cone responses to integrated gradients of substrate-bound ECM molecules and diffusible guidance cues.

    PubMed

    Joanne Wang, C; Li, Xiong; Lin, Benjamin; Shim, Sangwoo; Ming, Guo-Li; Levchenko, Andre

    2008-02-01

    Neuronal growth cones contain sophisticated molecular machinery precisely regulating their migration in response to complex combinatorial gradients of diverse external cues. The details of this regulation are still largely unknown, in part due to limitations of the currently available experimental techniques. Microfluidic devices have been shown to be capable of generating complex, stable and precisely controlled chemical gradients, but their use in studying growth cone migration has been limited in part due to the effects of shear stress. Here we describe a microfluidics-based turning-assay chip designed to overcome this issue. In addition to generating precise gradients of soluble guidance cues, the chip can also fabricate complex composite gradients of diffusible and surface-bound guidance cues that mimic the conditions the growth cones realistically counter in vivo. Applying this assay to Xenopus embryonic spinal neurons, we demonstrate that the presence of a surface-bound laminin gradient can finely tune the polarity of growth cone responses (repulsion or attraction) to gradients of brain-derived neurotrophic factor (BDNF), with the guidance outcome dependent on the mean BDNF concentration. The flexibility inherent in this assay holds significant potential for refinement of our understanding of nervous system development and regeneration, and can be extended to elucidate other cellular processes involving chemotaxis of shear sensitive cells.

  9. Cdc42 and actin control polarized expression of TI-VAMP vesicles to neuronal growth cones and their fusion with the plasma membrane.

    PubMed

    Alberts, Philipp; Rudge, Rachel; Irinopoulou, Theano; Danglot, Lydia; Gauthier-Rouvière, Cécile; Galli, Thierry

    2006-03-01

    Tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP)-mediated fusion of intracellular vesicles with the plasma membrane is crucial for neurite outgrowth, a pathway not requiring synaptobrevin-dependent exocytosis. Yet, it is not known how the TI-VAMP membrane trafficking pathway is regulated or how it is coordinated with cytoskeletal dynamics within the growth cone that guide neurite outgrowth. Here, we demonstrate that TI-VAMP, but not synaptobrevin 2, concentrates in the peripheral, F-actin-rich region of the growth cones of hippocampal neurons in primary culture. Its accumulation correlates with and depends upon the presence of F-actin. Moreover, acute stimulation of actin remodeling by homophilic activation of the adhesion molecule L1 induces a site-directed, actin-dependent recruitment of the TI-VAMP compartment. Expression of a dominant-positive mutant of Cdc42, a key regulator of cell polarity, stimulates formation of F-actin- and TI-VAMP-rich filopodia outside the growth cone. Furthermore, we report that Cdc42 activates exocytosis of pHLuorin tagged TI-VAMP in an actin-dependent manner. Collectively, our data suggest that Cdc42 and regulated assembly of the F-actin network control the accumulation and exocytosis of TI-VAMP-containing membrane vesicles in growth cones to coordinate membrane trafficking and actin remodeling during neurite outgrowth.

  10. Cdc42 and Actin Control Polarized Expression of TI-VAMP Vesicles to Neuronal Growth Cones and Their Fusion with the Plasma MembraneV⃞

    PubMed Central

    Alberts, Philipp; Rudge, Rachel; Irinopoulou, Theano; Danglot, Lydia; Gauthier-Rouvière, Cécile; Galli, Thierry

    2006-01-01

    Tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP)-mediated fusion of intracellular vesicles with the plasma membrane is crucial for neurite outgrowth, a pathway not requiring synaptobrevin-dependent exocytosis. Yet, it is not known how the TI-VAMP membrane trafficking pathway is regulated or how it is coordinated with cytoskeletal dynamics within the growth cone that guide neurite outgrowth. Here, we demonstrate that TI-VAMP, but not synaptobrevin 2, concentrates in the peripheral, F-actin-rich region of the growth cones of hippocampal neurons in primary culture. Its accumulation correlates with and depends upon the presence of F-actin. Moreover, acute stimulation of actin remodeling by homophilic activation of the adhesion molecule L1 induces a site-directed, actin-dependent recruitment of the TI-VAMP compartment. Expression of a dominant-positive mutant of Cdc42, a key regulator of cell polarity, stimulates formation of F-actin- and TI-VAMP-rich filopodia outside the growth cone. Furthermore, we report that Cdc42 activates exocytosis of pHLuorin tagged TI-VAMP in an actin-dependent manner. Collectively, our data suggest that Cdc42 and regulated assembly of the F-actin network control the accumulation and exocytosis of TI-VAMP-containing membrane vesicles in growth cones to coordinate membrane trafficking and actin remodeling during neurite outgrowth. PMID:16381811

  11. Motility imaging via optical coherence phase microscopy enables label-free monitoring of tissue growth and viability in 3D tissue-engineering scaffolds.

    PubMed

    Holmes, Christina; Tabrizian, Maryam; Bagnaninchi, Pierre O

    2015-05-01

    As the field of tissue engineering continues to progress, there is a deep need for non-invasive, label-free imaging technologies that can monitor tissue growth and health within thick three-dimensional (3D) constructs. Amongst the many imaging modalities under investigation, optical coherence tomography (OCT) has emerged as a promising tool, enabling non-destructive in situ characterization of scaffolds and engineered tissues. However, the lack of optical contrast between cells and scaffold materials using this technique remains a challenge. In this communication, we show that mapping the optical phase fluctuations resulting from cellular viability and motility allows for the distinction of live cells from their surrounding scaffold environment. Motility imaging was performed via a common-path optical coherence phase microscope (OCPM), an OCT modality that has been shown to be sensitive to nanometer-level fluctuations. More specifically, we examined the development of human adipose-derived stem cells and/or murine pre-osteoblasts within two distinct scaffold systems, commercially available alginate sponges and custom-microfabricated poly(d, l-lactic-co-glycolic acid) fibrous scaffolds. Cellular motility is demonstrated as an endogenous source of contrast for OCPM, enabling real-time, label-free monitoring of 3D engineered tissue development.

  12. S100A4 is frequently overexpressed in lung cancer cells and promotes cell growth and cell motility

    SciTech Connect

    Chen, Na; Sato, Daisuke; Saiki, Yuriko; Sunamura, Makoto; Fukushige, Shinichi; Horii, Akira

    2014-05-09

    Highlights: • We observed frequent overexpression of S100A4 in lung cancer cell lines. • Knockdown of S100A4 suppressed proliferation in lung cancer cells. • Forced expression of S100A4 accelerated cell motility in lung cancer cells. • PRDM2 was found to be one of the downstream suppressed genes of S100A4. - Abstract: S100A4, a small calcium-binding protein belonging to the S100 protein family, is commonly overexpressed in a variety of tumor types and is widely accepted to associate with metastasis by regulating the motility and invasiveness of cancer cells. However, its biological role in lung carcinogenesis is largely unknown. In this study, we found that S100A4 was frequently overexpressed in lung cancer cells, irrespective of histological subtype. Then we performed knockdown and forced expression of S100A4 in lung cancer cell lines and found that specific knockdown of S100A4 effectively suppressed cell proliferation only in lung cancer cells with S100A4-overexpression; forced expression of S100A4 accelerated cell motility only in S100A4 low-expressing lung cancer cells. PRDM2 and VASH1, identified as novel upregulated genes by microarray after specific knockdown of S100A4 in pancreatic cancer, were also analyzed, and we found that PRDM2 was significantly upregulated after S100A4-knockdown in one of two analyzed S100A4-overexpressing lung cancer cells. Our present results suggest that S100A4 plays an important role in lung carcinogenesis by means of cell proliferation and motility by a pathway similar to that in pancreatic cancer.

  13. Cell Guidance on Nanogratings: A Computational Model of the Interplay between PC12 Growth Cones and Nanostructures

    PubMed Central

    Tonazzini, Ilaria; Cecchini, Marco; Micera, Silvestro

    2013-01-01

    Background Recently, the effects of nanogratings have been investigated on PC12 with respect to cell polarity, neuronal differentiation, migration, maturation of focal adhesions and alignment of neurites. Methodology/Principal Findings A synergistic procedure was used to study the mechanism of alignment of PC12 neurites with respect to the main direction of nanogratings. Finite Element simulations were used to qualitatively assess the distribution of stresses at the interface between non-spread growth cones and filopodia, and to study their dependence on filopodial length and orientation. After modelling all adhesions under non-spread growth cone and filopodial protrusions, the values of local stress maxima resulted from the length of filopodia. Since the stress was assumed to be the main triggering cause leading to the increase and stabilization of filopodia, the position of the local maxima was directly related to the orientation of neurites. An analytic closed form equation was then written to quantitatively assess the average ridge width needed to achieve a given neuritic alignment (R2 = 0.96), and the alignment course, when the ridge depth varied (R2 = 0.97). A computational framework was implemented within an improved free Java environment (CX3D) and in silico simulations were carried out to reproduce and predict biological experiments. No significant differences were found between biological experiments and in silico simulations (alignment, p = 0.3571; tortuosity, p = 0.2236) with a standard level of confidence (95%). Conclusions/Significance A mechanism involved in filopodial sensing of nanogratings is proposed and modelled through a synergistic use of FE models, theoretical equations and in silico simulations. This approach shows the importance of the neuritic terminal geometry, and the key role of the distribution of the adhesion constraints for the cell/substrate coupling process. Finally, the effects of the geometry of nanogratings were

  14. Differential growth factor regulation of N-cadherin expression and motility in normal and malignant oral epithelium.

    PubMed

    Diamond, Michelle E; Sun, Limin; Ottaviano, Adam J; Joseph, Mathew J; Munshi, Hidayatullah G

    2008-07-01

    Aberrant expression of N-cadherin is associated with tumor progression in squamous cell carcinomas (SCCs). Consequently, we examined the regulation of N-cadherin by TGFbeta1, an important mediator of keratinocyte and SCC function. N-cadherin expression was increased in oral SCC (OSCC) cell lines, regulating motility and correlating with TGFbeta1 production. Moreover, in normal keratinocytes TGFbeta1 increased expression of N-cadherin to regulate motility. TGFbeta1-mediated N-cadherin expression in the oral keratinocytes was blocked using siRNA targeting Smads. Unexpectedly, we found that EGF blocked TGFbeta1-mediated N-cadherin expression in oral keratinocytes and not in OSCC cells. Mechanistically, EGF enhanced Smad phosphorylation in the linker region, and attenuated TGFbeta1-mediated phosphorylation of Smad at the C-terminus, localization of Smad to the nucleus as well as Smad-driven promoter activity exclusively in oral keratinocytes but not in OSCC cells. The effect of EGF on TGFbeta1-mediated Smad-driven promoter activity and N-cadherin expression was reversed when activation of ERK1/2 was blocked. Although EGF and TGFbeta1 independently promoted migration of both oral keratinocytes and OSCC cells, EGF decreased TGFbeta1-mediated migration of oral keratinocytes but enhanced migration of OSCC cells. Together, these data support a model wherein EGF signaling has an important negative regulatory role on TGFbeta1-mediated N-cadherin expression and motility in normal oral keratinocytes, and in which loss of this regulatory mechanism accompanies malignant transformation of the oral epithelium.

  15. Learn About GI Motility

    MedlinePlus

    ... eNewsletter Sidebar × MOBILE MENU About Us Learn About GI Motility Digestive Tract Disorders of the Esophagus Disorders ... Pelvic Floor Motility Testing Personal Stories Contact About GI Motility Twitter Facebook YouTube Search Search ... About Us ...

  16. About GI Motility

    MedlinePlus

    ... eNewsletter Sidebar × MOBILE MENU About Us Learn About GI Motility Digestive Tract Disorders of the Esophagus Disorders ... Pelvic Floor Motility Testing Personal Stories Contact About GI Motility Twitter Facebook YouTube Search Search ... About Us ...

  17. The dynein inhibitor Ciliobrevin D inhibits the bidirectional transport of organelles along sensory axons and impairs NGF-mediated regulation of growth cones and axon branches.

    PubMed

    Sainath, Rajiv; Gallo, Gianluca

    2015-07-01

    The axonal transport of organelles is critical for the development, maintenance, and survival of neurons, and its dysfunction has been implicated in several neurodegenerative diseases. Retrograde axon transport is mediated by the motor protein dynein. In this study, using embryonic chicken dorsal root ganglion neurons, we investigate the effects of Ciliobrevin D, a pharmacological dynein inhibitor, on the transport of axonal organelles, axon extension, nerve growth factor (NGF)-induced branching and growth cone expansion, and axon thinning in response to actin filament depolymerization. Live imaging of mitochondria, lysosomes, and Golgi-derived vesicles in axons revealed that both the retrograde and anterograde transport of these organelles was inhibited by treatment with Ciliobrevin D. Treatment with Ciliobrevin D reversibly inhibits axon extension and transport, with effects detectable within the first 20 min of treatment. NGF induces growth cone expansion, axonal filopodia formation and branching. Ciliobrevin D prevented NGF-induced formation of axonal filopodia and branching but not growth cone expansion. Finally, we report that the retrograde reorganization of the axonal cytoplasm which occurs on actin filament depolymerization is inhibited by treatment with Ciliobrevin D, indicating a role for microtubule based transport in this process, as well as Ciliobrevin D accelerating Wallerian degeneration. This study identifies Ciliobrevin D as an inhibitor of the bidirectional transport of multiple axonal organelles, indicating this drug may be a valuable tool for both the study of dynein function and a first pass analysis of the role of axonal transport.

  18. Mediator of ERBB2-driven cell motility (MEMO) promotes extranuclear estrogen receptor signaling involving the growth factor receptors IGF1R and ERBB2.

    PubMed

    Jiang, Kai; Yang, Zhihong; Cheng, Long; Wang, Shibin; Ning, Kang; Zhou, Lei; Lin, Jing; Zhong, Hui; Wang, Lisheng; Li, Yang; Huang, Junjian; Zhang, Hao; Ye, Qinong

    2013-08-23

    In addition to nuclear estrogen receptor (ER) acting as a transcription factor, extranuclear ER also plays an important role in cancer cell growth regulation through activation of kinase cascades. However, the molecular mechanisms by which extranuclear ER exerts its function are still poorly understood. Here, we report that mediator of ERBB2-driven cell motility (MEMO) regulates extranuclear functions of ER. MEMO physically and functionally interacted with ER. Through its interaction with the growth factor receptors IGF1R and ERBB2, MEMO mediated extranuclear functions of ER, including activation of mitogen-activated protein kinase (MAPK) and protein kinase B/AKT, two important growth regulatory protein kinases, and integration of function with nuclear ER. Activation of MAPK and AKT was responsible for MEMO modulation of ER phosphorylation and estrogen-responsive gene expression. Moreover, MEMO increased anchorage-dependent and -independent growth of ER-positive breast cancer cells in vitro and was required for estrogen-induced breast tumor growth in nude mice. Together, our studies identified MEMO as a new component of extranuclear ER signalosome and suggest an essential role for MEMO in the regulation of ER-positive breast cancer cell growth.

  19. Secreted Human Amyloid Precursor Protein Binds Semaphorin 3a and Prevents Semaphorin-Induced Growth Cone Collapse

    PubMed Central

    Guerreiro, Luiz H.; Beltrão, Paulo José I.; Carvalho, Milena M. V. F.; da S. Santos, Luís Eduardo; de Mello, Fernando G.; Reis, Ricardo A. M.; Ferreira, Sérgio T.

    2011-01-01

    The amyloid precursor protein (APP) is well known for giving rise to the amyloid-β peptide and for its role in Alzheimer's disease. Much less is known, however, on the physiological roles of APP in the development and plasticity of the central nervous system. We have used phage display of a peptide library to identify high-affinity ligands of purified recombinant human sAPPα695 (the soluble, secreted ectodomain from the main neuronal APP isoform). Two peptides thus selected exhibited significant homologies with the conserved extracellular domain of several members of the semaphorin (Sema) family of axon guidance proteins. We show that sAPPα695 binds both purified recombinant Sema3A and Sema3A secreted by transfected HEK293 cells. Interestingly, sAPPα695 inhibited the collapse of embryonic chicken (Gallus gallus domesticus) dorsal root ganglia growth cones promoted by Sema3A (Kd≤8·10−9 M). Two Sema3A-derived peptides homologous to the peptides isolated by phage display blocked sAPPα binding and its inhibitory action on Sema3A function. These two peptides are comprised within a domain previously shown to be involved in binding of Sema3A to its cellular receptor, suggesting a competitive mechanism by which sAPPα modulates the biological action of semaphorins. PMID:21829538

  20. Differential requirement of F-actin and microtubule cytoskeleton in cue-induced local protein synthesis in axonal growth cones.

    PubMed

    Piper, Michael; Lee, Aih Cheun; van Horck, Francisca P G; McNeilly, Heather; Lu, Trina Bo; Harris, William A; Holt, Christine E

    2015-02-25

    Local protein synthesis (LPS) via receptor-mediated signaling plays a role in the directional responses of axons to extrinsic cues. An intact cytoskeleton is critical to enact these responses, but it is not known whether the two major cytoskeletal elements, F-actin and microtubules, have any roles in regulating axonal protein synthesis. Here, we show that pharmacological disruption of either microtubules or actin filaments in growth cones blocks netrin-1-induced de novo synthesis of proteins, as measured by metabolic incorporation of labeled amino acids, implicating both elements in axonal synthesis. However, comparative analysis of the activated translation initiation regulator, eIF4E-BP1, revealed a striking difference in the point of action of the two elements: actin disruption completely inhibited netrin-1-induced eIF4E-BP1 phosphorylation while microtubule disruption had no effect. An intact F-actin, but not microtubule, cytoskeleton was also required for netrin-1-induced activation of the PI3K/Akt/mTOR pathway, upstream of translation initiation. Downstream of translation initiation, microtubules were required for netrin-1-induced activation of eukaryotic elongation factor 2 kinase (eEF2K) and eEF2. Taken together, our results show that while actin and microtubules are both crucial for cue-induced axonal protein synthesis, they serve distinct roles with F-actin being required for the initiation of translation and microtubules acting later at the elongation step.

  1. EMA: a developmentally regulated cell-surface glycoprotein of CNS neurons that is concentrated at the leading edge of growth cones.

    PubMed

    Baumrind, N L; Parkinson, D; Wayne, D B; Heuser, J E; Pearlman, A L

    1992-08-01

    To identify cell-surface molecules that mediate interactions between neurons and their environment during neural development, we used monoclonal antibody techniques to define a developmentally regulated antigen in the central nervous system of the mouse. The antibody we produced (2A1) immunolabels cells throughout the central nervous system; we analyzed its distribution in the developing cerebral cortex, where it is expressed on cells very soon after they complete mitosis and leave the periventricular proliferative zone. Expression continues into adult life. The antibody also labels the epithelium of the choroid plexus and the renal proximal tubules, but does not label neurons of the peripheral nervous system in the dorsal root ganglia. In dissociated cell culture of embryonic cerebral cortex, 2A1 labels the surface of neurons but not glia. Immunolabeling of neurons in tissue culture is particularly prominent on the edge of growth cones, including filopodia and the leading edge of lamellipodia, when observed with either immunofluorescence or freeze-etch immunoelectron microscopy. Immunopurification with 2A1 of a CHAPS-extracted membrane preparation from brains of neonatal mice produces a broad (32-36 kD) electrophoretic band and a less prominent 70 kD band that are sensitive to N-glycosidase but not endoglycosidase H. Thus the 2A1 antibody recognizes a developmentally regulated, neuronal cell surface glycoprotein (or glycoproteins) with complex N-linked oligosaccharide side chains. We have termed the glycoprotein antigen EMA because of its prominence on the edge membrane of growth cones. EMA is similar to the M6 antigen (Lagenaur et al: J. Neurobiol. 23:71-88, 1992) in apparent molecular weight, distribution in tissue sections, and immunoreactivity on Western blots, suggesting that the two antigens are similar or identical. Expression of EMA is a very early manifestation of neuronal differentiation; its distribution on growth cones suggests a role in mediating the

  2. Cone Heads

    ERIC Educational Resources Information Center

    Coy, Mary

    2005-01-01

    The author, a middle school art teacher, describes a sculpture project lesson involving Cone Heads (sculptures made from cardboard cones). Discussion of caricatures with exaggerated facial features and interesting profiles helped students understand that the more expressive the face, the better. This project took approximately four to five…

  3. Effects of crystallographic plane and co-deposited element on the growth of ion-sputter induced Si nano-cone arrays: a mechanism study

    NASA Astrophysics Data System (ADS)

    Song, Sheng-Chi; Qiu, Ying; Hao, Hong-Chen; Lu, Ming

    2015-06-01

    Self-organized Si nano-cone arrays induced by Ar+ ion sputtering on different Si crystallographic planes with different co-deposited alien atoms are investigated. The Si planes are (100), (110), and (111) ones, and the alien elements are Ta, Mo, Fe, and C, respectively. It is found that the growth of Si nano-cone arrays is insensitive to the initial crystallographic plane, but depends strongly on the co-deposited element. For the same Ar+ ion dose and sample temperature, the smaller the activation energy between the co-deposited element and Si is, the larger the average cone height and base diameter are. It is found that the preferential sputtering does not play an important role in the nano-cone formation. A model based on the concepts of classical surface-curvature-dependent sputtering yield and the formation of stationary silicide is proposed, which explains the observed results. The results of microstructural and compositional analysis support the proposed model.

  4. Phosphorylation of the adaptor protein SH2B1β regulates its ability to enhance growth hormone-dependent macrophage motility.

    PubMed

    Su, Hsiao-Wen; Lanning, Nathan J; Morris, David L; Argetsinger, Lawrence S; Lumeng, Carey N; Carter-Su, Christin

    2013-04-15

    Previous studies have shown that growth hormone (GH) recruits the adapter protein SH2B1β to the GH-activated, GH receptor-associated tyrosine kinase JAK2, implicating SH2B1β in GH-dependent actin cytoskeleton remodeling, and suggesting that phosphorylation at serines 161 and 165 in SH2B1β releases SH2B1β from the plasma membrane. Here, we examined the role of SH2B1β in GH regulation of macrophage migration. We show that GH stimulates migration of cultured RAW264.7 macrophages, and primary cultures of peritoneal and bone marrow-derived macrophages. SH2B1β overexpression enhances, whereas SH2B1 knockdown inhibits, GH-dependent motility of RAW macrophages. At least two independent mechanisms regulate the SH2B1β-mediated changes in motility. In response to GH, tyrosines 439 and 494 in SH2B1β are phosphorylated. Mutating these tyrosines in SH2B1β decreases both basal and GH-stimulated macrophage migration. In addition, mutating the polybasic nuclear localization sequence (NLS) in SH2B1β or creating the phosphomimetics SH2B1β(S161E) or SH2B1β(S165E), all of which release SH2B1β from the plasma membrane, enhances macrophage motility. Conversely, SH2B1β(S161/165A) exhibits increased localization at the plasma membrane and decreased macrophage migration. Mutating the NLS or the nearby serine residues does not alter GH-dependent phosphorylation on tyrosines 439 and 494 in SH2B1β. Mutating tyrosines 439 and 494 does not affect localization of SH2B1β at the plasma membrane or movement of SH2B1β into focal adhesions. Taken together, these results suggest that SH2B1β enhances GH-stimulated macrophage motility via mechanisms involving phosphorylation of SH2B1β on tyrosines 439 and 494 and movement of SH2B1β out of the plasma membrane (e.g. as a result of phosphorylation of serines 161 and 165).

  5. The Stringent Response Regulator DksA Is Required for Salmonella enterica Serovar Typhimurium Growth in Minimal Medium, Motility, Biofilm Formation, and Intestinal Colonization

    PubMed Central

    Azriel, Shalhevet; Goren, Alina; Rahav, Galia

    2015-01-01

    Salmonella enterica serovar Typhimurium is a facultative intracellular human and animal bacterial pathogen posing a major threat to public health worldwide. Salmonella pathogenicity requires complex coordination of multiple physiological and virulence pathways. DksA is a conserved Gram-negative regulator that belongs to a distinct group of transcription factors that bind directly to the RNA polymerase secondary channel, potentiating the effect of the signaling molecule ppGpp during a stringent response. Here, we established that in S. Typhimurium, dksA is induced during the logarithmic phase and DksA is essential for growth in minimal defined medium and plays an important role in motility and biofilm formation. Furthermore, we determined that DksA positively regulates the Salmonella pathogenicity island 1 and motility-chemotaxis genes and is necessary for S. Typhimurium invasion of human epithelial cells and uptake by macrophages. In contrast, DksA was found to be dispensable for S. Typhimurium host cell adhesion. Finally, using the colitis mouse model, we found that dksA is spatially induced at the midcecum during the early stage of the infection and required for gastrointestinal colonization and systemic infection in vivo. Taken together, these data indicate that the ancestral stringent response regulator DksA coordinates various physiological and virulence S. Typhimurium programs and therefore is a key virulence regulator of Salmonella. PMID:26553464

  6. The Disruption of the Cytoskeleton during Semaphorin 3A induced Growth Cone Collapse Correlates with Differences in Actin Organization and Associated Binding Proteins

    PubMed Central

    Brown, Jacquelyn A; Bridgman, Paul C

    2010-01-01

    Repulsive guidance cues induce growth cone collapse or collapse and retraction. Collapse results from disruption and loss of the actin cytoskeleton. Actin rich regions of growth cones contain binding proteins that influence filament organization, such as Arp2/3, cortactin, and fascin, but little is known about the role that these proteins play in collapse. Here we show that Semaphorin 3A (Sema 3A), which is repulsive to mouse dorsal root ganglion neurons, has unequal effects on actin binding proteins and their associated filaments. The immunofluorescence staining intensity of Arp-2 and cortactin decreases relative to total protein, while in unextracted growth cones fascin increases. Fascin and myosin IIB staining redistribute and show increased overlap. The degree of actin filament loss during collapse correlates with filament superstructures detected by rotary shadow electron microscopy. Collapse results in the loss of branched f-actin meshworks, while actin bundles are partially retained to varying degrees. Taken together with the known affects of Sema 3A on actin, this suggests a model for collapse that follows a sequence; depolymerization of actin meshworks followed by partial depolymerization of fascin associated actin bundles and their movement to the neurite to complete collapse. The relocated fascin associated actin bundles may provide the substrate for actomyosin contractions that produce retraction. PMID:19513995

  7. RNA-binding proteins and translational regulation in axons and growth cones

    PubMed Central

    Hörnberg, Hanna; Holt, Christine

    2013-01-01

    RNA localization and regulation play an important role in the developing and adult nervous system. In navigating axons, extrinsic cues can elicit rapid local protein synthesis that mediates directional or morphological responses. The mRNA repertoire in axons is large and dynamically changing, yet studies suggest that only a subset of these mRNAs are translated after cue stimulation, suggesting the need for a high level of translational regulation. Here, we review the role of RNA-binding proteins (RBPs) as local regulators of translation in developing axons. We focus on their role in growth, guidance, and synapse formation, and discuss the mechanisms by which they regulate translation in axons. PMID:23734093

  8. Serum response factor mediated gene activity in physiological and pathological processes of neuronal motility.

    PubMed

    Knöll, Bernd

    2011-01-01

    In recent years, the transcription factor serum response factor (SRF) was shown to contribute to various physiological processes linked to neuronal motility. The latter include cell migration, axon guidance, and, e.g., synapse function relying on cytoskeletal dynamics, neurite outgrowth, axonal and dendritic differentiation, growth cone motility, and neurite branching. SRF teams up with myocardin related transcription factors (MRTFs) and ternary complex factors (TCFs) to mediate cellular actin cytoskeletal dynamics and the immediate-early gene (IEG) response, a bona fide indicator of neuronal activation. Herein, I will discuss how SRF and cofactors might modulate physiological processes of neuronal motility. Further, potential mechanisms engaged by neurite growth promoting molecules and axon guidance cues to target SRF's transcriptional machinery in physiological neuronal motility will be presented. Of note, altered cytoskeletal dynamics and rapid initiation of an IEG response are a hallmark of injured neurons in various neurological disorders. Thus, SRF and its MRTF and TCF cofactors might emerge as a novel trio modulating peripheral and central axon regeneration.

  9. Serum Response Factor Mediated Gene Activity in Physiological and Pathological Processes of Neuronal Motility

    PubMed Central

    Knöll, Bernd

    2011-01-01

    In recent years, the transcription factor serum response factor (SRF) was shown to contribute to various physiological processes linked to neuronal motility. The latter include cell migration, axon guidance, and, e.g., synapse function relying on cytoskeletal dynamics, neurite outgrowth, axonal and dendritic differentiation, growth cone motility, and neurite branching. SRF teams up with myocardin related transcription factors (MRTFs) and ternary complex factors (TCFs) to mediate cellular actin cytoskeletal dynamics and the immediate-early gene (IEG) response, a bona fide indicator of neuronal activation. Herein, I will discuss how SRF and cofactors might modulate physiological processes of neuronal motility. Further, potential mechanisms engaged by neurite growth promoting molecules and axon guidance cues to target SRF’s transcriptional machinery in physiological neuronal motility will be presented. Of note, altered cytoskeletal dynamics and rapid initiation of an IEG response are a hallmark of injured neurons in various neurological disorders. Thus, SRF and its MRTF and TCF cofactors might emerge as a novel trio modulating peripheral and central axon regeneration. PMID:22164132

  10. Ecophysiological strategies for growth under varying light and organic carbon supply in two species of green microalgae differing in their motility.

    PubMed

    Spijkerman, Elly; Lukas, Marcus; Wacker, Alexander

    2017-09-04

    Mixing events in stratified lakes result in microalgae being exposed to varying conditions in light and organic carbon concentrations. Stratified lakes consist of an upper illuminated strata and a lower, darker strata where organic carbon accumulates. Therefore, in this contribution we explore the importance of dissolved organic carbon for growth under various light intensities by measuring some ecophysiological adaptations in two green microalgae. We compared the non-motile Chlorella vulgaris with the flagellated Chlamydomonas acidophila under auto-, mixo-, and heterotrophic growth conditions. In both algae the maximum photosynthetic and growth rates were highest under mixotrophy, and both algae appeared inhibited in their phosphorus acquisition under heterotrophy. Heterotrophic conditions provoked the largest differences as C. vulgaris produced chlorophyll a in darkness and grew as well as in autotrophic conditions, whereas Chl. acidophila bleached and could not grow heterotrophically. Although the fatty acid composition of both phytoplankton species differed, both species reacted in a similar way to changes in their growth conditions, mainly by a decrease of C18:3n-3 and an increase of C18:1n-9 from auto- to heterotrophic conditions. The two contrasting responses within the group of green microalgae suggest that dissolved organic carbon has a high deterministic potential to explain the survival and behaviour of green algae in the deeper strata of lakes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Effect of drugs affecting microtubular assembly on microtubules, phospholipid synthesis and physiological indices (signalling, growth, motility and phagocytosis) in Tetrahymena pyriformis.

    PubMed

    Kovács, P; Csaba, G

    2006-01-01

    Structural changes of microtubules, incorporation of radioactively labelled components into phospholipids, cell motility, growth and phagocytosis were studied under the effect of four drugs affecting microtubular assembly: colchicine, nocodazole, vinblastine and taxol. Although the first three agents influence microtubules in the direction of depolymerization and the fourth stabilizes them, their effects on the structure of microtubules cannot be explained by this. Using confocal microscopy after an acetylated anti-tubulin label, in nocodazole- and colchicine-treated cells, the basal body cages disappear and longitudinal microtubules (LM) became thinner without changing transversal microtubules (TM). After taxol treatment LM also became thinner, however TM disappeared. Under the effect of vinblastine TM became thinner, without influencing LM. These drugs influence the incorporation of components ([(3)H]-serine, [(3)H]-palmitic acid and (32)P) into phospholipids, however their effect is equivocal and cannot be consequently coupled with the effect on the microtubules. Nocodazole, vinblastine and taxol significantly reduced the cell's motility, however colchicine did so to a lesser degree. Vinblastine and nocodazole totally inhibited, and taxol significantly decreased cell growth, while colchicine in a lower concentration increased the multiplication of cells. Phagocytosis was not significantly influenced after 1 min, but after 5 min all the agents studied (except colchicine) significantly inhibited phagocytosis. After 15 and 30 min each molecule caused highly significant inhibition. The experiments demonstrate that drugs affecting microtubular assembly dynamics influence differently the diverse (longitudinal, transversal etc.) microtubular systems of Tetrahymena and also differently influence microtubule-dependent physiological processes. The latter are more dependent on microtubular dynamics than are changes in phospholipid signalling.

  12. Procyanidin B2 3,3″-di-O-gallate inhibits endothelial cells growth and motility by targeting VEGFR2 and integrin signaling pathways.

    PubMed

    Kumar, Rahul; Deep, Gagan; Wempe, Michael F; Agarwal, Rajesh; Agarwal, Chapla

    2015-01-01

    Targeting angiogenesis, one of the hallmarks of carcinogenesis, using non-toxic phytochemicals has emerged as a translational opportunity for angioprevention and to control advanced stages of malignancy. Herein, we investigated the inhibitory effects and associated mechanism/s of action of Procyanidin B2-3,3″-di- O-gallate (B2G2), a major component of grape seed extract, on human umbilical vein endothelial cells (HUVECs) and human prostate microvascular endothelial cells (HPMECs). Our results showed that B2G2 (10-40 μM) inhibits growth and induces death in both HUVECs and HPMECs. Additional studies revealed that B2G2 causes a G1 arrest in cell cycle progression of HUVECs by down-regulating cyclins (D1 and A), CDKs (Cdk2 and Cdc2) and Cdc25c phosphatase and up-regulating CDK inhibitors (p21 and p27) expression. B2G2 also induced strong apoptotic death in HUVECs through increasing p53, Bax and Smac/Diablo expression while decreasing Bcl-2 and survivin levels. Additionally, B2G2 inhibited the growth factors-induced capillary tube formation in HUVECs and HPMECs. Interestingly, conditioned media (CCM) from prostate cancer (PCA) cells (LNCaP and PC3) grown under normoxic (~21% O2) and hypoxic (1% O2) conditions significantly enhanced the tube formation in HUVECs, which was compromised in presence of conditioned media from B2G2-treated PCA cells. B2G2 also inhibited the motility and invasiveness of both HUVECs and HPMECs. Mechanistic studies showed that B2G2 targets VEGFR2/PI3K/Akt and integrin signaling molecules which are important for endothelial cells survival, proliferation, tube formation and motility. Overall, we report that B2G2 inhibits several attributes of angiogenesis in cell culture; therefore, it warrants further investigation for efficacy for angioprevention and cancer control.

  13. Polar Cone

    NASA Image and Video Library

    2006-07-10

    This MOC image shows a cone-shaped hill, perhaps a remnant of a material that was once more laterally extensive across the area, on a textured plain in the Hyperboreus Labyrinthus region in the north polar region of Mars

  14. Chronic herbivory negatively impacts cone and seed production, seed quality and seedling growth of susceptible pinyon pines.

    PubMed

    Mueller, Rebecca C; Wade, Brian D; Gehring, Catherine A; Whitham, Thomas G

    2005-05-01

    Although herbivory often reduces the reproduction of attacked trees, few studies have examined how naturally occurring insect-resistant and susceptible trees differ in their reproduction, nor have these effects been experimentally examined through long-term herbivore removals. In addition, few studies have examined the effects of herbivory on the quality of seeds produced and the implications of reduced seed quality on seedling establishment. We evaluated the impact of chronic herbivory by the stem-boring moth, Dioryctria albovittella, on cone and seed production of the pinyon pine (Pinus edulis) during two mast years. Three patterns emerged. First, moth herbivory was associated with reductions in cone production, viable seed production and seed mass. Specifically, pinyons susceptible to moth attack had 93-95% lower cone production, and surviving cones produced 31-37% fewer viable seeds, resulting in a 96-97% reduction in whole tree viable seed production. In addition, surviving seeds from susceptible trees had 18% lower mass than resistant trees. Second, long-term experimental removal of the herbivore resulted in increased rates of cone and seed production and quality, indicating that moth herbivory was the driver of these reductions. Third, seed size was positively associated with seed germination and seedling biomass and height, suggesting that trees suffering chronic herbivory produce poorer quality offspring. Thus, the resistance traits of pinyons can affect the quality of offspring, which in turn may affect subsequent seedling establishment and population dynamics.

  15. Platelet-Rich Plasma Increases Growth and Motility of Adipose Tissue-Derived Mesenchymal Stem Cells and Controls Adipocyte Secretory Function.

    PubMed

    D'Esposito, Vittoria; Passaretti, Federica; Perruolo, Giuseppe; Ambrosio, Maria Rosaria; Valentino, Rossella; Oriente, Francesco; Raciti, Gregory A; Nigro, Cecilia; Miele, Claudia; Sammartino, Gilberto; Beguinot, Francesco; Formisano, Pietro

    2015-10-01

    Adipose tissue-derived mesenchymal stem cells (Ad-MSC) and platelet derivatives have been used alone or in combination to achieve regeneration of injured tissues. We have tested the effect of platelet-rich plasma (PRP) on Ad-MSC and adipocyte function. PRP increased Ad-MSC viability, proliferation rate and G1-S cell cycle progression, by at least 7-, 2-, and 2.2-fold, respectively, and reduced caspase 3 cleavage. Higher PRP concentrations or PRPs derived from individuals with higher platelet counts were more effective in increasing Ad-MSC growth. PRP also accelerated cell migration by at least 1.5-fold. However, PRP did not significantly affect mature adipocyte viability, differentiation and expression levels of PPAR-γ and AP-2 mRNAs, while it increased leptin production by 3.5-fold. Interestingly, PRP treatment of mature adipocytes also enhanced the release of Interleukin (IL)-6, IL-8, IL-10, Interferon-γ, and Vascular Endothelial Growth Factor. Thus, data are consistent with a stimulatory effect of platelet derivatives on Ad-MSC growth and motility. Moreover, PRP did not reduce mature adipocyte survival and increased the release of pro-angiogenic factors, which may facilitate tissue regeneration processes.

  16. Surface orientation affects the direction of cone growth by Leptolyngbya sp. strain C1, a likely architect of coniform structures Octopus Spring (Yellowstone National Park).

    PubMed

    Reyes, Kristina; Gonzalez, Nicolas I; Stewart, Joshua; Ospino, Frank; Nguyen, Dickie; Cho, David T; Ghahremani, Nahal; Spear, John R; Johnson, Hope A

    2013-02-01

    Laminated, microbially produced stromatolites within the rock record provide some of the earliest evidence for life on Earth. The chemical, physical, and biological factors that lead to the initiation of these organosedimentary structures and shape their morphology are unclear. Modern coniform structures with morphological features similar to stromatolites are found on the surface of cyanobacterial/microbial mats. They display a vertical element of growth, can have lamination, can be lithified, and observably grow with time. To begin to understand the microbial processes and interactions required for cone formation, we determined the phylogenetic composition of the microbial community of a coniform structure from a cyanobacterial mat at Octopus Spring, Yellowstone National Park, and reconstituted coniform structures in vitro. The 16S rRNA clone library from the coniform structure was dominated by Leptolyngbya sp. Other cyanobacteria and heterotrophic bacteria were present in much lower abundance. The same Leptolyngbya sp. identified in the clone library was also enriched in the laboratory and could produce cones in vitro. When coniform structures were cultivated in the laboratory, the initial incubation conditions were found to influence coniform morphology. In addition, both the angle of illumination and the orientation of the surface affected the angle of cone formation demonstrating how external factors can influence coniform, and likely, stromatolite morphology.

  17. Surface Orientation Affects the Direction of Cone Growth by Leptolyngbya sp. Strain C1, a Likely Architect of Coniform Structures Octopus Spring (Yellowstone National Park)

    PubMed Central

    Reyes, Kristina; Gonzalez, Nicolas I.; Stewart, Joshua; Ospino, Frank; Nguyen, Dickie; Cho, David T.; Ghahremani, Nahal; Spear, John R.

    2013-01-01

    Laminated, microbially produced stromatolites within the rock record provide some of the earliest evidence for life on Earth. The chemical, physical, and biological factors that lead to the initiation of these organosedimentary structures and shape their morphology are unclear. Modern coniform structures with morphological features similar to stromatolites are found on the surface of cyanobacterial/microbial mats. They display a vertical element of growth, can have lamination, can be lithified, and observably grow with time. To begin to understand the microbial processes and interactions required for cone formation, we determined the phylogenetic composition of the microbial community of a coniform structure from a cyanobacterial mat at Octopus Spring, Yellowstone National Park, and reconstituted coniform structures in vitro. The 16S rRNA clone library from the coniform structure was dominated by Leptolyngbya sp. Other cyanobacteria and heterotrophic bacteria were present in much lower abundance. The same Leptolyngbya sp. identified in the clone library was also enriched in the laboratory and could produce cones in vitro. When coniform structures were cultivated in the laboratory, the initial incubation conditions were found to influence coniform morphology. In addition, both the angle of illumination and the orientation of the surface affected the angle of cone formation demonstrating how external factors can influence coniform, and likely, stromatolite morphology. PMID:23241986

  18. Conciliating efficiency and dynamical consistency in the simulation of the effects of proliferation and motility of transforming growth factor β on cancer cells

    NASA Astrophysics Data System (ADS)

    Macías-Díaz, J. E.

    2016-11-01

    In this work, we provide some discretizations of a partial differential equation that generalizes the well-known Fisher's equation from population dynamics. The mathematical model of interest is a nonlinear diffusion-reaction equation that appears in the investigation of the proliferation and motility effect of transforming growth factor β on cancer cells. Only positive and bounded solutions are physically relevant in this context, and the discretizations that we provide in this manuscript are able to preserve both properties. One of the techniques is an implicit linear method that is motivated by previous approaches of the author. On the other hand, the second method is a novel explicit exponential technique which has the advantage of requiring less computational resources and less computer time. Similar qualitative results are obtained with both methods, but the latter one is able to handle finer grid meshes. Some qualitative and quantitative comparisons are carried out in support of the advantages of the exponential scheme. It is worthwhile to note that the explicit technique used in the present manuscript has the advantage over other exponential methodologies that it yields no singularities. In addition, the preservation of the properties of non-negativity and boundedness of both the solution and the total mass are distinctive features which are established analytically in this work. The numerical simulations on cancer growth obtained with the exponential method are found to be in good agreement with the experimental results available in the literature.

  19. Bacillus cereus ATCC 14579 RpoN (Sigma 54) Is a Pleiotropic Regulator of Growth, Carbohydrate Metabolism, Motility, Biofilm Formation and Toxin Production.

    PubMed

    Hayrapetyan, Hasmik; Tempelaars, Marcel; Nierop Groot, Masja; Abee, Tjakko

    2015-01-01

    Sigma 54 is a transcriptional regulator predicted to play a role in physical interaction of bacteria with their environment, including virulence and biofilm formation. In order to study the role of Sigma 54 in Bacillus cereus, a comparative transcriptome and phenotypic study was performed using B. cereus ATCC 14579 WT, a markerless rpoN deletion mutant, and its complemented strain. The mutant was impaired in many different cellular functions including low temperature and anaerobic growth, carbohydrate metabolism, sporulation and toxin production. Additionally, the mutant showed lack of motility and biofilm formation at air-liquid interphase, and this correlated with absence of flagella, as flagella staining showed only WT and complemented strain to be highly flagellated. Comparative transcriptome analysis of cells harvested at selected time points during growth in aerated and static conditions in BHI revealed large differences in gene expression associated with loss of phenotypes, including significant down regulation of genes in the mutant encoding enzymes involved in degradation of branched chain amino acids, carbohydrate transport and metabolism, flagella synthesis and virulence factors. Our study provides evidence for a pleiotropic role of Sigma 54 in B. cereus supporting its adaptive response and survival in a range of conditions and environments.

  20. Fast Turnover of L1 Adhesions in Neuronal Growth Cones Involving Both Surface Diffusion and Exo/Endocytosis of L1 Molecules

    PubMed Central

    Dequidt, Caroline; Danglot, Lydia; Alberts, Philipp; Galli, Thierry; Choquet, Daniel

    2007-01-01

    We investigated the interplay between surface trafficking and binding dynamics of the immunoglobulin cell adhesion molecule L1 at neuronal growth cones. Primary neurons were transfected with L1 constructs bearing thrombin-cleavable green fluorescent protein (GFP), allowing visualization of newly exocytosed L1 or labeling of membrane L1 molecules by Quantum dots. Intracellular L1–GFP vesicles showed preferential centrifugal motion, whereas surface L1–GFP diffused randomly, revealing two pathways to address L1 to adhesive sites. We triggered L1 adhesions using microspheres coated with L1–Fc protein or anti-L1 antibodies, manipulated by optical tweezers. Microspheres coupled to the actin retrograde flow at the growth cone periphery while recruiting L1–GFP molecules, of which 50% relied on exocytosis. Fluorescence recovery after photobleaching experiments revealed a rapid recycling of L1–GFP molecules at L1–Fc (but not anti-L1) bead contacts, attributed to a high lability of L1–L1 bonds at equilibrium. L1–GFP molecules truncated in the intracellular tail as well as neuronal cell adhesion molecules (NrCAMs) missing the clathrin adaptor binding sequence showed both little internalization and reduced turnover rates, indicating a role of endocytosis in the recycling of mature L1 contacts at the base of the growth cone. Thus, unlike for other molecules such as NrCAM or N-cadherin, diffusion/trapping and exo/endocytosis events cooperate to allow the fast renewal of L1 adhesions. PMID:17538021

  1. 2D protrusion but not motility predicts growth factor-induced cancer cell migration in 3D collagen.

    PubMed

    Meyer, Aaron S; Hughes-Alford, Shannon K; Kay, Jennifer E; Castillo, Amalchi; Wells, Alan; Gertler, Frank B; Lauffenburger, Douglas A

    2012-06-11

    Growth factor-induced migration is a critical step in the dissemination and metastasis of solid tumors. Although differences in properties characterizing cell migration on two-dimensional (2D) substrata versus within three-dimensional (3D) matrices have been noted for particular growth factor stimuli, the 2D approach remains in more common use as an efficient surrogate, especially for high-throughput experiments. We therefore were motivated to investigate which migration properties measured in various 2D assays might be reflective of 3D migratory behavioral responses. We used human triple-negative breast cancer lines stimulated by a panel of receptor tyrosine kinase ligands relevant to mammary carcinoma progression. Whereas 2D migration properties did not correlate well with 3D behavior across multiple growth factors, we found that increased membrane protrusion elicited by growth factor stimulation did relate robustly to enhanced 3D migration properties of the MDA-MB-231 and MDA-MB-157 lines. Interestingly, we observed this to be a more reliable relationship than cognate receptor expression or activation levels across these and two additional mammary tumor lines.

  2. Human Axonal Survival of Motor Neuron (a-SMN) Protein Stimulates Axon Growth, Cell Motility, C-C Motif Ligand 2 (CCL2), and Insulin-like Growth Factor-1 (IGF1) Production*

    PubMed Central

    Locatelli, Denise; Terao, Mineko; Fratelli, Maddalena; Zanetti, Adriana; Kurosaki, Mami; Lupi, Monica; Barzago, Maria Monica; Uggetti, Andrea; Capra, Silvia; D'Errico, Paolo; Battaglia, Giorgio S.; Garattini, Enrico

    2012-01-01

    Spinal muscular atrophy is a fatal genetic disease of motoneurons due to loss of full-length survival of motor neuron protein, the main product of the disease gene SMN1. Axonal SMN (a-SMN) is an alternatively spliced isoform of SMN1, generated by retention of intron 3. To study a-SMN function, we generated cellular clones for the expression of the protein in mouse motoneuron-like NSC34 cells. The model was instrumental in providing evidence that a-SMN decreases cell growth and plays an important role in the processes of axon growth and cellular motility. In our conditions, low levels of a-SMN expression were sufficient to trigger the observed biological effects, which were not modified by further increasing the amounts of the expressed protein. Differential transcriptome analysis led to the identification of novel a-SMN-regulated factors, i.e. the transcripts coding for the two chemokines, C-C motif ligands 2 and 7 (CCL2 and CCL7), as well as the neuronal and myotrophic factor, insulin-like growth factor-1 (IGF1). a-SMN-dependent induction of CCL2 and IGF1 mRNAs resulted in increased intracellular levels and secretion of the respective protein products. Induction of CCL2 contributes to the a-SMN effects, mediating part of the action on axon growth and random cell motility, as indicated by chemokine knockdown and re-addition studies. Our results shed new light on a-SMN function and the underlying molecular mechanisms. The data provide a rational framework to understand the role of a-SMN deficiency in the etiopathogenesis of spinal muscular atrophy. PMID:22669976

  3. Growth hormone (GH) therapy markedly increases the motility of spermatozoa and the concentration of insulin-like growth factor-I in seminal vesicle fluid in the male GH-deficient dwarf rat.

    PubMed

    Breier, B H; Vickers, M H; Gravance, C G; Casey, P J

    1996-09-01

    There is increasing evidence for an important role of the somatotropic axis in male reproductive function. We investigated the effect of recombinant bovine GH (rbGH) treatment for 21 days on semen characteristics in post-pubertal GH-deficient dwarf (dw/dw) rats. Male dw/dw rats at an age of 75-80 days were divided into two groups (n = 10 per group) and injected twice per day with either rbGH (2 micrograms/g/day) or saline. While the concentration (96.4 +/- 51.3 x 10(6) per ml) and morphology of spermatozoa (spermatozoa with normal morphology 73.5 +/- 6.3%) in the dw/dw rat were within the normal range, the motility of spermatozoa was very low (27.5 +/- 11.7%), establishing a state of sub-fertility. The rbGH treatment markedly increased (p < 0.01) motility of spermatozoa (44.5 +/- 10.7%) but did not change the concentration (144 +/- 80.3 x 10(6) per ml) and morphology (spermatozoa with normal morphology 79.5 +/- 6.0%). The rbGH treatment also significantly increased the concentration of insulin-like growth factor-I (IGF-I) in blood plasma (control 389.1 +/- 65 ng/ml, rbGH 813.9 ng/ml, p < 0.001) and in seminal vesicle fluid (control 11.3 +/- 3.0 ng/ml, rbGH 16.1 +/- 5.4 ng/ml, p < 0.05). We conclude that rbGH therapy markedly increases motility of spermatozoa in sub-fertile male GH-deficient dw/dw rats. Thus, GH therapy may offer considerable potential for the treatment of impaired male reproductive performance.

  4. Tenascin-C enhances pancreatic cancer cell growth and motility and affects cell adhesion through activation of the integrin pathway.

    PubMed

    Paron, Igor; Berchtold, Sonja; Vörös, Julia; Shamarla, Madhavi; Erkan, Mert; Höfler, Heinz; Esposito, Irene

    2011-01-01

    Pancreatic cancer (PDAC) is characterized by an abundant fibrous tissue rich in Tenascin-C (TNC), a large ECM glycoprotein mainly synthesized by pancreatic stellate cells (PSCs). In human pancreatic tissues, TNC expression increases in the progression from low-grade precursor lesions to invasive cancer. Aim of this study was the functional characterization of the effects of TNC on biologic relevant properties of pancreatic cancer cells. Proliferation, migration and adhesion assays were performed on pancreatic cancer cell lines treated with TNC or grown on a TNC-rich matrix. Stable transfectants expressing the large TNC splice variant were generated to test the effects of endogenous TNC. TNC-dependent integrin signaling was investigated by immunoblotting, immunofluorescence and pharmacological inhibition. Endogenous TNC promoted pancreatic cancer cell growth and migration. A TNC-rich matrix also enhanced migration as well as the adhesion to the uncoated growth surface of poorly differentiated cell lines. In contrast, adhesion to fibronectin was significantly decreased in the presence of TNC. The effects of TNC on cell adhesion were paralleled by changes in the activation state of paxillin and Akt. TNC affects proliferation, migration and adhesion of poorly differentiated pancreatic cancer cell lines and might therefore play a role in PDAC spreading and metastasis in vivo.

  5. Deficiency of the Survival of Motor Neuron Protein Impairs mRNA Localization and Local Translation in the Growth Cone of Motor Neurons.

    PubMed

    Fallini, Claudia; Donlin-Asp, Paul G; Rouanet, Jeremy P; Bassell, Gary J; Rossoll, Wilfried

    2016-03-30

    Spinal muscular atrophy (SMA) is a neurodegenerative disease primarily affecting spinal motor neurons. It is caused by reduced levels of the survival of motor neuron (SMN) protein, which plays an essential role in the biogenesis of spliceosomal small nuclear ribonucleoproteins in all tissues. The etiology of the specific defects in the motor circuitry in SMA is still unclear, but SMN has also been implicated in mediating the axonal localization of mRNA-protein complexes, which may contribute to the axonal degeneration observed in SMA. Here, we report that SMN deficiency severely disrupts local protein synthesis within neuronal growth cones. We also identify the cytoskeleton-associated growth-associated protein 43 (GAP43) mRNA as a new target of SMN and show that motor neurons from SMA mouse models have reduced levels ofGAP43mRNA and protein in axons and growth cones. Importantly, overexpression of two mRNA-binding proteins, HuD and IMP1, restoresGAP43mRNA and protein levels in growth cones and rescues axon outgrowth defects in SMA neurons. These findings demonstrate that SMN plays an important role in the localization and local translation of mRNAs with important axonal functions and suggest that disruption of this function may contribute to the axonal defects observed in SMA. The motor neuron disease spinal muscular atrophy (SMA) is caused by reduced levels of the survival of motor neuron (SMN) protein, which plays a key role in assembling RNA/protein complexes that are essential for mRNA splicing. It remains unclear whether defects in this well characterized housekeeping function cause the specific degeneration of spinal motor neurons observed in SMA. Here, we describe an additional role of SMN in regulating the axonal localization and local translation of the mRNA encoding growth-associated protein 43 (GAP43). This study supports a model whereby SMN deficiency impedes transport and local translation of mRNAs important for neurite outgrowth and stabilization

  6. Deficiency of the Survival of Motor Neuron Protein Impairs mRNA Localization and Local Translation in the Growth Cone of Motor Neurons

    PubMed Central

    Fallini, Claudia; Donlin-Asp, Paul G.; Rouanet, Jeremy P.

    2016-01-01

    Spinal muscular atrophy (SMA) is a neurodegenerative disease primarily affecting spinal motor neurons. It is caused by reduced levels of the survival of motor neuron (SMN) protein, which plays an essential role in the biogenesis of spliceosomal small nuclear ribonucleoproteins in all tissues. The etiology of the specific defects in the motor circuitry in SMA is still unclear, but SMN has also been implicated in mediating the axonal localization of mRNA-protein complexes, which may contribute to the axonal degeneration observed in SMA. Here, we report that SMN deficiency severely disrupts local protein synthesis within neuronal growth cones. We also identify the cytoskeleton-associated growth-associated protein 43 (GAP43) mRNA as a new target of SMN and show that motor neurons from SMA mouse models have reduced levels of GAP43 mRNA and protein in axons and growth cones. Importantly, overexpression of two mRNA-binding proteins, HuD and IMP1, restores GAP43 mRNA and protein levels in growth cones and rescues axon outgrowth defects in SMA neurons. These findings demonstrate that SMN plays an important role in the localization and local translation of mRNAs with important axonal functions and suggest that disruption of this function may contribute to the axonal defects observed in SMA. SIGNIFICANCE STATEMENT The motor neuron disease spinal muscular atrophy (SMA) is caused by reduced levels of the survival of motor neuron (SMN) protein, which plays a key role in assembling RNA/protein complexes that are essential for mRNA splicing. It remains unclear whether defects in this well characterized housekeeping function cause the specific degeneration of spinal motor neurons observed in SMA. Here, we describe an additional role of SMN in regulating the axonal localization and local translation of the mRNA encoding growth-associated protein 43 (GAP43). This study supports a model whereby SMN deficiency impedes transport and local translation of mRNAs important for neurite

  7. The ratio of 'deleted in colorectal cancer' to 'uncoordinated-5A' netrin-1 receptors on the growth cone regulates mossy fibre directionality.

    PubMed

    Muramatsu, Rieko; Nakahara, Soichiro; Ichikawa, Junya; Watanabe, Keisuke; Matsuki, Norio; Koyama, Ryuta

    2010-01-01

    Proper axonal targeting is fundamental to the establishment of functional neural circuits. The hippocampal mossy fibres normally project towards the CA3 region. In the hippocampi of patients with temporal lobe epilepsy and related animal models, however, mossy fibres project towards the molecular layer and produce the hyperexcitable recurrent networks. The cellular and molecular mechanisms underlying this aberrant axonal targeting, known as mossy fibre sprouting, remain unclear. Netrin-1 attracts or repels axons depending on the composition of its attraction-mediating receptor, deleted in colorectal cancer, and its repulsion-mediating receptor, uncoordinated-5, on the growth cone; but the roles of netrin-1-dependent guidance in pathological conditions are largely unknown. In this study, we examined the role of netrin-1 and its receptors in mossy fibre guidance and report that enhanced neuronal activity changes netrin-1-mediated cell targeting by the axons under hyperexcitable conditions. Netrin-1 antibody or Dcc ribonucleic acid interference attenuated mossy fibre growth towards CA3 in slice overlay assays. The axons were repelled from CA3 and ultimately innervated the molecular layer when hyperactivity was pharmacologically introduced. We first hypothesized that a reduction in netrin-1 expression in CA3 underlies the phenomenon, but found that its expression was increased. We then examined two possible activity-dependent changes in netrin-1 receptor expression: a reduction in the deleted in colorectal cancer receptor and induction of uncoordinated-5 receptor. Hyperactivity did not affect the surface expression of the deleted in colorectal cancer receptor on the growth cone, but it increased that of uncoordinated-5A, which was suppressed by blocking cyclic adenosine monophosphate signalling. In addition, Dcc knockdown did not affect hyperactivity-induced mossy fibre sprouting in the slice cultures, whereas Unc5a knockdown rescued the mistargeting. Thus, netrin-1

  8. EphrinA/EphA-induced ectodomain shedding of neural cell adhesion molecule regulates growth cone repulsion through ADAM10 metalloprotease.

    PubMed

    Brennaman, Leann H; Moss, Marcia L; Maness, Patricia F

    2014-01-01

    EphrinA/EphA-dependent axon repulsion is crucial for synaptic targeting in developing neurons but downstream molecular mechanisms remain obscure. Here, it is shown that ephrinA5/EphA3 triggers proteolysis of the neural cell adhesion molecule (NCAM) by the metalloprotease a disintegrin and metalloprotease (ADAM)10 to promote growth cone collapse in neurons from mouse neocortex. EphrinA5 induced ADAM10 activity to promote ectodomain shedding of polysialic acid-NCAM in cortical neuron cultures, releasing a ~ 250 kDa soluble fragment consisting of most of its extracellular region. NCAM shedding was dependent on ADAM10 and EphA3 kinase activity as shown in HEK293T cells transfected with dominant negative ADAM10 and kinase-inactive EphA3 (K653R) mutants. Purified ADAM10 cleaved NCAM at a sequence within the E-F loop of the second fibronectin type III domain (Leu(671) -Lys(672) /Ser(673) -Leu(674) ) identified by mass spectrometry. Mutations of NCAM within the ADAM10 cleavage sequence prevented EphA3-induced shedding of NCAM in HEK293T cells. EphrinA5-induced growth cone collapse was dependent on ADAM10 activity, was inhibited in cortical cultures from NCAM null mice, and was rescued by WT but not ADAM10 cleavage site mutants of NCAM. Regulated proteolysis of NCAM through the ephrin5/EphA3/ADAM10 mechanism likely impacts synapse development, and may lead to excess NCAM shedding when disrupted, as implicated in neurodevelopmental disorders such as schizophrenia. PSA-NCAM and ephrinA/EphA3 coordinately regulate inhibitory synapse development. Here, we have found that ephrinA5 stimulates EphA3 kinase and ADAM10 activity to promote PSA-NCAM cleavage at a site in its second FNIII repeat, which regulates ephrinA5-induced growth cone collapse in GABAergic and non-GABAergic neurons. These findings identify a new regulatory mechanism which may contribute to inhibitory connectivity.

  9. rpoN1, but not rpoN2, is required for twitching motility, natural competence, growth on nitrate, and virulence of Ralstonia solanacearum

    PubMed Central

    Ray, Suvendra K.; Kumar, Rahul; Peeters, Nemo; Boucher, Christian; Genin, Stephane

    2015-01-01

    The plant pathogen Ralstonia solanacearum has two genes encoding for the sigma factor σ54: rpoN1, located in the chromosome and rpoN2, located in a distinct “megaplasmid” replicon. In this study, individual mutants as well as a double mutant of rpoN were created in R. solanacearum strain GMI1000 in order to determine the extent of functional overlap between these two genes. By virulence assay we observed that rpoN1 is required for virulence whereas rpoN2 is not. In addition rpoN1 controls other important functions such twitching motility, natural transformation and growth on nitrate, unlike rpoN2. The rpoN1 and rpoN2 genes have different expression pattern, the expression of rpoN1 being constitutive whereas rpoN2 expression is induced in minimal medium and in the presence of plant cells. Moreover, the expression of rpoN2 is dependent upon rpoN1. Our work therefore reveals that the two rpoN genes are not functionally redundant in R. solanacearum. A list of potential σ54 targets was identified in the R. solanacearum genome and suggests that multiple traits are under the control of these regulators. Based on these findings, we provide a model describing the functional connection between RpoN1 and the PehR pathogenicity regulator and their dual role in the control of several R. solanacearum virulence determinants. PMID:25852679

  10. Cross-talk between LPA1 and Epidermal Growth Factor Receptors Mediates Up-regulation of Sphingosine Kinase 1 to Promote Gastric Cancer Cell Motility and Invasion

    PubMed Central

    Shida, Dai; Fang, Xianjun; Kordula, Tomasz; Takabe, Kazuaki; Lépine, Sandrine; Alvarez, Sergio E.; Milstien, Sheldon; Spiegel, Sarah

    2009-01-01

    Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are lysophospholipid mediators of diverse cellular processes important for cancer progression. S1P is produced by two sphingosine kinases, SphK1 and SphK2. Expression of SphK1 is elevated in many cancers. Here, we report that LPA markedly enhanced SphK1 mRNA and protein in gastric cancer MKN1 cells but had no effect on SphK2. LPA also up-regulated SphK1 expression in other human cancer cells that endogenously express the LPA1 receptor, such as DLD1 colon cancer cells and MDA-MB-231 breast cancer cells, but not in HT29 colon cancer cells or MDA-MB-453 breast cancer cells, which do not express the LPA1 receptor. An LPA1 receptor antagonist or down-regulation of its expression prevented SphK1 and S1P3 receptor up-regulation by LPA. LPA transactivated the epidermal growth factor receptor (EGFR) in these cells, and the EGFR inhibitor AG1478 attenuated the increased SphK1 and S1P3 expression induced by LPA. Moreover, down-regulation of SphK1 attenuated LPA-stimulated migration and invasion of MNK1 cells yet had no effect on expression of neovascularizing factors, such as interleukin (IL)-8, IL-6, urokinase-type plasminogen activator (uPA), or uPA receptor induced by LPA. Finally, down-regulation of S1P3, but not S1P1, also reduced LPA-stimulated migration and invasion of MKN1 cells. Collectively, our results suggest that SphK1 is a convergence point of multiple cell surface receptors for three different ligands, LPA, EGF, and S1P, which have all been implicated in regulation of motility and invasiveness of cancer cells. PMID:18701480

  11. Sedimentary Biosignatures of Social Organization in Cone-Forming Filamentous Bacteria

    NASA Astrophysics Data System (ADS)

    Tice, M. M.; Gong, J.; Zeng, Z.; Sneed, J.; Wehner, M.; Sparks, D. W.

    2013-12-01

    Conical mats consisting of centimeter-scale steep-sided cones growing above flat basal films form some of the most distinctive fossil microbial communities in the geologic record. Cones have been hypothesized to form by the initially random motion of filamentous bacteria into small tangled clumps followed by the phototactic motion of the same bacteria up resulting slopes. More recent models of cone development suggest that they form in response to growth in stagnant fluids where diffusion limits exchange of nutrients and wastes with the environment. Determining the biological and environmental factors that promote cone formation will be important for interpreting the geological record of fossil mats and stromatolites, on Earth and potentially on Mars. Here we report the results of new experiments demonstrating complex social organization of cone-forming communities and a novel biosignature of the growth of such communities on sandy sediments, as well as detection of that biosignature in 3.2 Ga fossil mats of the Moodies Group (Barberton greenstone belt, South Africa). In order to investigate the processes involved in cone formation, we grew cultures of a filamentous cyanobacterium originally isolated from tufted cones in Yellowstone National Park, Montana, U.S.A. (Leptolyngbya sp. Y-WT-2000 Cl 1). During early mat development, filaments coat sand grain surfaces and aggregate into ~100-μm-long tufts, or mutually aligned bundles of filaments. Tufts are highly motile, bridging sand grains and merging to form larger tufts. After 10-14 days of growth, tufts aggregate during the early morning into centers composed of many tufts that wave vertically and along the sand surface. Centers move across the sediment surface during the middle of the day and merge along bridging tufts. These bridges transmit force to the underlying sediment and are capable of rolling sand grains. At this stage, mats are composed of small mobile centers that disperse along streams of co

  12. SKI-606 decreases growth and motility of colorectal cancer cells by preventing pp60(c-Src)-dependent tyrosine phosphorylation of beta-catenin and its nuclear signaling.

    PubMed

    Coluccia, Addolorata Maria Luce; Benati, Daniela; Dekhil, Hafedh; De Filippo, Annamaria; Lan, Cathy; Gambacorti-Passerini, Carlo

    2006-02-15

    Inhibition of deregulated protein tyrosine kinases represents an attractive strategy for controlling cancer growth. However, target specificity is an essential aim of this strategy. In this report, pp60(c-Src) kinase and beta-catenin were found physically associated and constitutively activated on tyrosine residues in human colorectal cancer cells. The use of specific small-interfering RNAs (siRNA) validated pp60(c-Src) as the major kinase responsible for beta-catenin tyrosine phosphorylation in colorectal cancer. Src-dependent activation of beta-catenin was prevented by SKI-606, a novel Src family kinase inhibitor, which also abrogated beta-catenin nuclear function by impairing its binding to the TCF4 transcription factor and its trans-activating ability in colorectal cancer cells. These effects were seemingly specific, as cyclin D1, a crucial beta-catenin/TCF4 target gene, was also down-regulated by SKI-606 in a dose-dependent manner accounting, at least in part, for the reduced growth (IC50, 1.5-2.4 micromol/L) and clonogenic potential of colorectal cancer cells. Protein levels of beta-catenin remained substantially unchanged by SKI-606, which promoted instead a cytosolic/membranous retention of beta-catenin as judged by immunoblotting analysis of cytosolic/nuclear extracts and cell immunofluorescence staining. The SKI-606-mediated relocalization of beta-catenin increased its binding affinity to E-cadherin and adhesion of colorectal cancer cells, with ensuing reduced motility in a wound healing assay. Interestingly, the siRNA-driven knockdown of beta-catenin removed the effect of SKI-606 on cell-to-cell adhesion, which was associated with prolonged stability of E-cadherin protein in a pulse-chase experiment. Thus, our results show that SKI-606 operates a switch between the transcriptional and adhesive function of beta-catenin by inhibiting its pp60(c-Src)-dependent tyrosine phosphorylation; this could constitute a new therapeutic target in colorectal cancer.

  13. GENERALIZED CONVEXITY CONES.

    DTIC Science & Technology

    Contents: Introduction The dual cone of C (psi sub 1,..., psi sub n) Extreme rays The cone dual to an intersection of generalized convexity cones... Generalized difference quotients and multivariate convexity Miscellaneous applications of generalized convexity.

  14. Regulation of flagellar motility during biofilm formation

    PubMed Central

    Guttenplan, Sarah B.; Kearns, Daniel B.

    2013-01-01

    Many bacteria swim in liquid or swarm over solid surfaces by synthesizing rotary flagella. The same bacteria that are motile also commonly form non-motile multicellular aggregates held together by an extracellular matrix called biofilms. Biofilms are an important part of the lifestyle of pathogenic bacteria and it is assumed that there is a motility-to-biofilm transition wherein the inhibition of motility promotes biofilm formation. The transition is largely inferred from regulatory mutants that reveal the opposite regulation of the two phenotypes. Here we review the regulation of motility during biofilm formation in Bacillus, Pseudomonas, Vibrio, and Escherichia, and we conclude that the motility-to-biofilm transition, if necessary, likely involves two steps. In the short term, flagella are functionally regulated to either inhibit rotation or modulate the basal flagellar reversal frequency. Over the long term, flagellar gene transcription is inhibited and in the absence of de novo synthesis, flagella are likely diluted to extinction through growth. Both short term and long term control is likely important to the motility-to-biofilm transition to stabilize aggregates and optimize resource investment. We emphasize the newly discovered classes of flagellar functional regulators and speculate that others await discovery in the context of biofilm formation. PMID:23480406

  15. Specificity of the effects of cytochalasin B on transport and motile processes.

    PubMed Central

    Lin, S; Lin, D C; Flanagan, M D

    1978-01-01

    The effects of cytochalasin B (CB) and dihydrocytochalasin B (H2CB) on a variety of transport and motile processes have been compared. CB inhibited transport of D-glucose and L-glucose but not transport of thymidine in human erythrocytes. In contrast, H2CB, which differs from CB by the absence of a single double bond, had little or no effect on any of these processes. Both cytochalasins, however, affected the morphology of cultured fibroblasts and inhibited motile processes such as membrane ruffling, axon growth cone activity, blood clot retraction, cytoplasmic streaming, photodinesis, and cytokinesis. Determination of the partition coefficient of the two cytochalasins in several organic solvent/phosphate-buffered saline systems showed that H2CB has a higher affinity for the hydrophobic phase than CB. These results indicate that the inhibitory effects of CB on sugar transport and on cell motility and morphology are separable and independent events, mediated by the binding of the drug to specific cellular receptors. Images PMID:272649

  16. Evaluation of maxillary sinus volume and dimensions in different vertical face growth patterns: a study of cone-beam computed tomography.

    PubMed

    Okşayan, Rıdvan; Sökücü, Oral; Yeşildal, Seher

    2017-07-01

    This study aimed to compare sinus volume and dimensions in patients with high-, low-, and normal-angle vertical growth patterns using cone-beam computed tomography (CBCT). According to skeletal vertical face growth patterns, 60 adults (31 female, 29 male, average age: 29.90 ± 10.91 years) were divided into three groups equally: high-angle, low-angle, and normal-angle groups. Cephalometric tracings were obtained from CBCT images and SN-GoGn (angle between Sella-Nasion line and Gonion-Gnathion line) cephalometric angular measurements used for the classification of skeletal vertical pattern evaluations. Morphological and dimensional changes in the maxillary sinuses were evaluated on CBCT images. Data were analyzed using the one-way ANOVA, Kruskall-Wallis, and Mann-Whitney U statistical tests. There were no statistically significant differences among the groups in terms of age (p > .05). The low-angle vertical growth pattern group showed significantly better results than the high-angle group in the right maxillary sinus length parameter (p < .05). According to the results, the high-angle subjects showed statistically lower values in terms of maxillary sinus length and width than the low-angle subjects. There were no effects of vertical face development on right and left maxillary sinus volumes. The results of this study may be useful in maxillary sinus evaluation when planning for orthognathic surgery and orthodontic mini screw application in various vertical face patterns.

  17. Role of glutamate in the regulation of the outgrowth and motility of neurites from mouse spinal cord neurons in culture

    PubMed Central

    OWEN, ALUN D.; BIRD, MARGARET M.

    1997-01-01

    The excitatory amino acid glutamate has been shown to be toxic to a number of neuronal cell types both in vitro and in vivo. It has also been shown to be capable of controlling the development of neurons grown in vitro. Using time-lapse video microscopy techniques the effects of glutamate on the rate of neurite outgrowth and growth cone motility were examined on cultured mouse spinal cord neurons. Concentrations in the range of 1 to 100 µ M caused a significant inhibition of neurite outgrowth and concentrations of 10 and 100 µ M significantly inhibited growth cone activity. In addition it was shown that the kainate/AMPA receptor antagonist (±)3-(2-carbvoxypiperazin-4-yl)-propyl-l-phosphonic acid, but not the NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione, was capable of blocking the inhibitory actions of glutamate on both outgrowth and motility. These results show that, at least in the culture system employed, glutamate might have a role in regulating neuronal development and function. PMID:9306206

  18. Cone calorimeter evaluation of wood products

    Treesearch

    Robert H. White; Mark A. Dietenberger

    2004-01-01

    The Forest Products Laboratory uses the cone calorimeter for the initial evaluation of the flammability of untreated and fire retardant treated wood products. The results of various studies are reviewed using a model presented at the 12th Annual BBC Conference on Flame Retardancy. The model uses data from the cone calorimeter to provide measures of fire growth...

  19. Neuronal deletion of GSK3β increases microtubule speed in the growth cone and enhances axon regeneration via CRMP-2 and independently of MAP1B and CLASP2

    PubMed Central

    2014-01-01

    Background In the adult central nervous system, axonal regeneration is abortive. Regulators of microtubule dynamics have emerged as attractive targets to promote axonal growth following injury as microtubule organization is pivotal for growth cone formation. In this study, we used conditioned neurons with high regenerative capacity to further dissect cytoskeletal mechanisms that might be involved in the gain of intrinsic axon growth capacity. Results Following a phospho-site broad signaling pathway screen, we found that in conditioned neurons with high regenerative capacity, decreased glycogen synthase kinase 3β (GSK3β) activity and increased microtubule growth speed in the growth cone were present. To investigate the importance of GSK3β regulation during axonal regeneration in vivo, we used three genetic mouse models with high, intermediate or no GSK3β activity in neurons. Following spinal cord injury, reduced GSK3β levels or complete neuronal deletion of GSK3β led to increased growth cone microtubule growth speed and promoted axon regeneration. While several microtubule-interacting proteins are GSK3β substrates, phospho-mimetic collapsin response mediator protein 2 (T/D-CRMP-2) was sufficient to decrease microtubule growth speed and neurite outgrowth of conditioned neurons and of GSK3β-depleted neurons, prevailing over the effect of decreased levels of phosphorylated microtubule-associated protein 1B (MAP1B) and through a mechanism unrelated to decreased levels of phosphorylated cytoplasmic linker associated protein 2 (CLASP2). In addition, phospho-resistant T/A-CRMP-2 counteracted the inhibitory myelin effect on neurite growth, further supporting the GSK3β-CRMP-2 relevance during axon regeneration. Conclusions Our work shows that increased microtubule growth speed in the growth cone is present in conditions of increased axonal growth, and is achieved following inactivation of the GSK3β-CRMP-2 pathway, enhancing axon regeneration through the glial scar

  20. Whiskers, cones and pyramids created in sputtering by ion bombardment

    NASA Technical Reports Server (NTRS)

    Wehner, G. K.

    1979-01-01

    A thorough study of the role which foreign atoms play in cone formation during sputtering of metals revealed many experimental facts. Two types of cone formation were distinquished, deposit cones and seed cones. Twenty-six combinations of metals for seed cone formation were tested. The sputtering yield variations with composition for combinations which form seed cones were measured. It was demonstrated that whisker growth becomes a common occurrence when low melting point material is sputter deposited on a hot nonsputtered high melting point electrode.

  1. The Super-Cone

    ERIC Educational Resources Information Center

    Fülöp, Zsolt

    2009-01-01

    Using the concept of exploded and compressed numbers the author constructs the supercone which is able to turn upon the border of three dimensional space and breaks through it. The introduction of super-cone gives a possibility for students to see the properties of traditional cone while the super-cone is not a traditional cone. Moreover we show…

  2. Nerve growth cones isolated from fetal rat brain. IV. Preparation of a membrane subfraction and identification of a membrane glycoprotein expressed on sprouting neurons

    PubMed Central

    1985-01-01

    This study describes the preparation of a membrane subfraction from isolated nerve growth cone particles (GCPs) (see Pfenninger, K. H., L. Ellis, M. P. Johnson, L. B. Friedman, and S. Somlo, 1983, Cell, 35:573- 584) and the identification in this fraction of a glycoprotein expressed during neurite growth. While approximately 40 major polypeptides are visible in Coomassie Blue-stained SDS polyacrylamide gels of pelleted (partially disrupted) GCPs, a salt-washed membrane fraction prepared from lysed, detergent-permeabilized GCPs contains only 14% of this protein and has an unusually simple polypeptide pattern of seven major bands. Monoclonal antibodies have been generated to GCP membranes isolated from fetal rat brain. These antibodies have been screened differentially with synaptosomes from adult rat brain in order to identify those which recognize antigens expressed selectively during neurite growth. One such antibody (termed 5B4) recognizes a developmentally regulated membrane glycoprotein that is enriched in GCP membranes and expressed in fetal neurons sprouting in vitro. The 5B4 antigen in fetal brain migrates in SDS polyacrylamide gels as a diffuse band of approximately 185-255 kD, is rich in sialic acid, and consists of a small family of isoelectric variants. Freezing-thawing and neuraminidase digestion result in the cleavage of the native antigen into two new species migrating diffusely around 200 and 160 kD. Prolonged neuraminidase digestion sharpens these bands at about 180 and 135 kD, respectively. In the mature brain, antibody 5B4 recognizes a sparse polypeptide migrating at approximately 140 kD. As shown in the following paper (Wallis, I., L. Ellis, K. Suh, and K. H. Pfenninger, 1985, J. Cell Biol., 101:1990-1998), the fetal antigen is specifically associated with regions of neuronal sprouting and, therefore, can be used as a molecular marker of neurite growth. PMID:3902858

  3. Tumor invasion as dysregulated cell motility.

    PubMed

    Kassis, J; Lauffenburger, D A; Turner, T; Wells, A

    2001-04-01

    Investigations across a range of disciplines over the past decade have brought the study of cell motility and its role in invasion to an exciting threshold. The biophysical forces proximally involved in generating cell locomotion, as well as the underlying signaling and genomic regulatory processes, are gradually becoming elucidated. We now appreciate the intricacies of the many cellular and extracellular events that modulate cell migration. This has enabled the demonstration of a causal role of cell motility in tumor progression, with various points of 'dysregulation' of motility being responsible for promoting invasion. In this paper, we describe key fundamental principles governing cell motility and branch out to describe the essence of the data that describe these principles. It has become evident that many proposed models may indeed be converging into a tightly-woven tapestry of coordinated events which employ various growth factors and their receptors, adhesion receptors (integrins), downstream molecules, cytoskeletal components, and altered genomic regulation to accomplish cell motility. Tumor invasion occurs in response to dysregulation of many of these modulatory points; specific examples include increased signaling from the EGF receptor and through PLC gamma, altered localization and expression of integrins, changes in actin modifying proteins and increased transcription from specific promoter sites. This diversity of alterations all leading to tumor invasion point to the difficulty of correcting causal events leading to tumor invasion and rather suggest that the underlying common processes required for motility be targeted for therapeutic intervention.

  4. Defective Gpsm2/Gαi3 signalling disrupts stereocilia development and growth cone actin dynamics in Chudley-McCullough syndrome

    NASA Astrophysics Data System (ADS)

    Mauriac, Stephanie A.; Hien, Yeri E.; Bird, Jonathan E.; Carvalho, Steve Dos-Santos; Peyroutou, Ronan; Lee, Sze Chim; Moreau, Maite M.; Blanc, Jean-Michel; Geyser, Aysegul; Medina, Chantal; Thoumine, Olivier; Beer-Hammer, Sandra; Friedman, Thomas B.; Rüttiger, Lukas; Forge, Andrew; Nürnberg, Bernd; Sans, Nathalie; Montcouquiol, Mireille

    2017-04-01

    Mutations in GPSM2 cause Chudley-McCullough syndrome (CMCS), an autosomal recessive neurological disorder characterized by early-onset sensorineural deafness and brain anomalies. Here, we show that mutation of the mouse orthologue of GPSM2 affects actin-rich stereocilia elongation in auditory and vestibular hair cells, causing deafness and balance defects. The G-protein subunit Gαi3, a well-documented partner of Gpsm2, participates in the elongation process, and its absence also causes hearing deficits. We show that Gpsm2 defines an ~200 nm nanodomain at the tips of stereocilia and this localization requires the presence of Gαi3, myosin 15 and whirlin. Using single-molecule tracking, we report that loss of Gpsm2 leads to decreased outgrowth and a disruption of actin dynamics in neuronal growth cones. Our results elucidate the aetiology of CMCS and highlight a new molecular role for Gpsm2/Gαi3 in the regulation of actin dynamics in epithelial and neuronal tissues.

  5. 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

  6. Pleomorphic carcinomas of the lung show a selective distribution of gene products involved in cell differentiation, cell cycle control, tumor growth, and tumor cell motility: a clinicopathologic and immunohistochemical study of 31 cases.

    PubMed

    Pelosi, Giuseppe; Fraggetta, Filippo; Nappi, Oscar; Pastorino, Ugo; Maisonneuve, Patrick; Pasini, Felice; Iannucci, Antonio; Solli, Piergiorgio; Musavinasab, Hossein S; De Manzoni, Giovanni; Terzi, Alberto; Viale, Giuseppe

    2003-09-01

    We investigated 31 cases of pleomorphic carcinomas of the lung, with a double component of neoplastic epithelial cells and of spindle and/or giant cells. To correlate the morphologic diversity of these two cell components with their immunophenotype, we evaluated the expression of several gene products involved in cell differentiation (cytokeratins, epithelial membrane antigen, carcinoembryonic antigen, vimentin, S-100 protein, smooth muscle actin, desmin), cell cycle control and apoptosis (p53, p21Waf1, p27Kip1, FHIT), tumor growth (proliferative fraction, assessed by Ki-67 antigen, and microvascular density, assessed by CD34 immunostaining), and tumor cell motility (fascin). We found the epithelial component to be significantly more immunoreactive for cytokeratins, epithelial membrane antigen, carcinoembryonic antigen, cell cycle inhibitors p21Waf1, p27Kip1 and tumor suppressor gene FHIT, whereas the sarcomatoid component, independent of tumor stage and size, was more immunoreactive for vimentin, fascin, and microvascular density. Accordingly, we suggest a model of tumorigenesis whereby the mesenchymal phenotype of pleomorphic cells is likely induced by the selective activation and segregation of several molecules involved in cell differentiation, cell cycle control, and tumor cell growth and motility. Whether pleomorphic carcinomas of the lung are tumors with a dismal prognosis still remains an unsettled issue. In our series, however, stage I pleomorphic carcinomas have the same clinical behavior as ordinary non-small cell lung cancer, and only a high proliferative index (Ki-67 labeling index >35%) is associated with a worse prognosis in these tumors.

  7. High mannose N-glycan binding lectin from Remusatia vivipara (RVL) limits cell growth, motility and invasiveness of human breast cancer cells.

    PubMed

    Sindhura, B R; Hegde, Prajna; Chachadi, Vishwanath B; Inamdar, Shashikala R; Swamy, Bale M

    2017-09-01

    Breast cancer known for its high metastatic potential is responsible for large mortality rate amongst women; hence it is imperative to search for effective anti-metastatic molecules despite anticancer drugs. The current study describes the potential of Remusatia vivipara lectin (RVL), inducing apoptosis in breast cancer cells there by limiting motility and invasiveness. RVL binds to the cell surface glycans of MDA-MB-468 and MCF-7 cells, exhibiting strong glycan mediated cytotoxic effect, but show marginal effect on non-tumorigenic MCF-10A cells. RVL elicits increased cellular stress, apoptotic vacuoles and nuclear disintegration in both MDA-MB-468 and MCF-7 cells accompanied by depletion of G0/G1, S and G2/M phases. Lectin interaction induced production of reactive oxygen species through altering mitochondrial membrane potential progressing to apoptosis. Further, RVL strongly elicited reproductive cell death in MDA-MB-468 cells and showed strong inhibitory effect on neovascularization demonstrated in chorioallantoic membrane assay. Treatment of MDA-MB-468 cells with RVL, suppress the motility and invasive property as shown by scratch wound heal and Boyden chamber transwell assays respectively. These results provide an insight into significance of interaction of RVL with specific cell surface high mannose N-glycans resulting in curtailing the metastatic ability of cancer cells. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  8. Microgravity, bacteria, and the influence of motility

    NASA Astrophysics Data System (ADS)

    Benoit, Michael R.; Klaus, David M.

    Space microbiology studies date back to the 1960s, with most investigations reporting that increased bacterial populations occur in flight compared to ground controls. Several exceptions to these findings, however, have created controversy and complicated explanations of how, or whether, microgravity affects microorganisms. Upon closer examination of the literature, we identified a trend relating cell motility to experimental outcome. Related studies conducted in microgravity analog devices, such as the clinostat or rotating wall vessel bioreactor, further corroborate this trend. We review the literature regarding bacterial growth experiments conducted in space (and using microgravity analogs) and analyze the influence of bacterial motility.

  9. Sperm Motility in Flow

    NASA Astrophysics Data System (ADS)

    Guasto, Jeffrey; Juarez, Gabriel; Stocker, Roman

    2012-11-01

    A wide variety of plants and animals reproduce sexually by releasing motile sperm that seek out a conspecific egg, for example in the reproductive tract for mammals or in the water column for externally fertilizing organisms. Sperm are aided in their quest by chemical cues, but must also contend with hydrodynamic forces, resulting from laminar flows in reproductive tracts or turbulence in aquatic habitats. To understand how velocity gradients affect motility, we subjected swimming sperm to a range of highly-controlled straining flows using a cross-flow microfluidic device. The motion of the cell body and flagellum were captured through high-speed video microscopy. The effects of flow on swimming are twofold. For moderate velocity gradients, flow simply advects and reorients cells, quenching their ability to cross streamlines. For high velocity gradients, fluid stresses hinder the internal bending of the flagellum, directly inhibiting motility. The transition between the two regimes is governed by the Sperm number, which compares the external viscous stresses with the internal elastic stresses. Ultimately, unraveling the role of flow in sperm motility will lead to a better understanding of population dynamics among aquatic organisms and infertility problems in humans.

  10. Defining motility in the Staphylococci.

    PubMed

    Pollitt, Eric J G; Diggle, Stephen P

    2017-08-01

    The ability of bacteria to move is critical for their survival in diverse environments and multiple ways have evolved to achieve this. Two forms of motility have recently been described for Staphylococcus aureus, an organism previously considered to be non-motile. One form is called spreading, which is a type of sliding motility and the second form involves comet formation, which has many observable characteristics associated with gliding motility. Darting motility has also been observed in Staphylococcus epidermidis. This review describes how motility is defined and how we distinguish between passive and active motility. We discuss the characteristics of the various forms of Staphylococci motility, the molecular mechanisms involved and the potential future research directions.

  11. Identification of novel 2-(1H-indol-1-yl)-benzohydrazides CXCR4 ligands impairing breast cancer growth and motility.

    PubMed

    Grande, Fedora; Barone, Ines; Aiello, Francesca; Brancale, Andrea; Cancellieri, Michela; Badolato, Mariateresa; Chemi, Francesca; Giordano, Cinzia; Vircillo, Valentina; Bonofiglio, Daniela; Garofalo, Antonio; Andò, Sebastiano; Catalano, Stefania

    2016-01-01

    Stromal-derived-factor-1 (SDF-1) and the G-protein-coupled receptor CXCR4 are involved in several physiological and pathological processes including breast cancer spread and progression. Several CXCR4 antagonists have currently reached advanced development stages as potential therapeutic agents for different diseases. A small series of novel CXCR4 ligands, based on a 2-(1H-indol-1-yl)-benzohydrazide scaffold, has been designed and synthesized. The interaction with CXCR4-active site was predicted by molecular docking and confirmed by whole cell-based [(125)I]-SDF-1 ligand competition binding assays. One of the synthesized compounds was particularly active in blocking SDF-1-induced breast cancer cell motility, proliferation and downstream signaling activation in different breast cancer cell models and coculture systems. The newly synthesized compounds represent suitable leads for the development of innovative therapeutic agents targeting CXCR4.

  12. A simple procedure for morphometric analysis of processes and growth cones of neurons in culture using parameters derived from the contour and convex hull of the object.

    PubMed

    Kawa, A; Stahlhut, M; Berezin, A; Bock, E; Berezin, V

    1998-01-31

    Morphometric estimation of neuronal processes is currently laborious and time-consuming, since the individual processes (axons and dendrites) have to be traced manually. In order to facilitate the measurement of cellular processes, we have tested a series of parameters derived from the contour and the convex hull of an object and estimated to which extent they reflect process length and number. The parameters included the area, perimeter and form factor of the object and convex hull, their ratios as well as object length, breadth, width, length/width and spreading index. Some new parameters derived from the contour and convex hull of the object, were also computed: process index (the number of areas contained within the convex hull outside the object contour), process domain (the total area contained within the convex hull outside the object contour), their ratio and the square root of the process domain (SR process domain). In total, 18 parameters were estimated. Populations of motoneurons, growth cones of cerebellar granule cells and N2a neuroblastoma cells were utilized due to their diversity in morphological features. The processes of each object were drawn by hand to establish the actual length and number. Total process length per object correlated strongly with object perimeter, process domain and SR process domain. The number of processes per object correlated well with perimeter ratio, process index and form factor, whereas object length, convex hull perimeter and spreading index correlated acceptably with the average process length. Using these parameters for the evaluation of neurite outgrowth in developing of hippocampal neurons in vitro, variables such as object perimeter, process domain and SR process domain were found to be very well suited for estimation of the total length of neurites. We conclude that based on the contour and convex hull of an object it is possible to calculate a series of parameters which may substitute direct measurements of

  13. A novel rare variant R292H in RTN4R affects growth cone formation and possibly contributes to schizophrenia susceptibility.

    PubMed

    Kimura, H; Fujita, Y; Kawabata, T; Ishizuka, K; Wang, C; Iwayama, Y; Okahisa, Y; Kushima, I; Morikawa, M; Uno, Y; Okada, T; Ikeda, M; Inada, T; Branko, A; Mori, D; Yoshikawa, T; Iwata, N; Nakamura, H; Yamashita, T; Ozaki, N

    2017-08-22

    Reticulon 4 receptor (RTN4R) plays an essential role in regulating axonal regeneration and plasticity in the central nervous system through the activation of rho kinase, and is located within chromosome 22q11.2, a region that is known to be a hotspot for schizophrenia (SCZ) and autism spectrum disorder (ASD). Recently, rare variants such as copy-number variants and single-nucleotide variants have been a focus of research because of their large effect size associated with increased susceptibility to SCZ and ASD and the possibility of elucidating the pathophysiology of mental disorder through functional analysis of the discovered rare variants. To discover rare variants with large effect size and to evaluate their role in the etiopathophysiology of SCZ and ASD, we sequenced the RTN4R coding exons with a sample comprising 370 SCZ and 192 ASD patients, and association analysis using a large number of unrelated individuals (1716 SCZ, 382 ASD and 4009 controls). Through this mutation screening, we discovered four rare (minor allele frequency <1%) missense mutations (R68H, D259N, R292H and V363M) of RTN4R. Among these discovered rare mutations, R292H was found to be significantly associated with SCZ (P=0.048). Furthermore, in vitro functional assays showed that the R292H mutation affected the formation of growth cones. This study strengthens the evidence for association between rare variants within RTN4R and SCZ, and may shed light on the molecular mechanisms underlying the neurodevelopmental disorder.

  14. Amyloid Precursor Protein family as unconventional Go-coupled receptors and the control of neuronal motility.

    PubMed

    Ramaker, Jenna M; Copenhaver, Philip F

    2017-01-01

    Cleavage of the Amyloid Precursor Protein (APP) generates amyloid peptides that accumulate in Alzheimer Disease (AD), but APP is also upregulated by developing and injured neurons, suggesting that it regulates neuronal motility. APP can also function as a G protein-coupled receptor that signals via the heterotrimeric G protein Gαo, but evidence for APP-Gαo signaling in vivo has been lacking. Using Manduca as a model system, we showed that insect APP (APPL) regulates neuronal migration in a Gαo-dependent manner. Recently, we also demonstrated that Manduca Contactin (expressed by glial cells) induces APPL-Gαo retraction responses in migratory neurons, consistent with evidence that mammalian Contactins also interact with APP family members. Preliminary studies using cultured hippocampal neurons suggest that APP-Gαo signaling can similarly regulate growth cone motility. Whether Contactins (or other APP ligands) induce this response within the developing nervous system, and how this pathway is disrupted in AD, remains to be explored.

  15. Modeling collective cell motility

    NASA Astrophysics Data System (ADS)

    Rappel, Wouter-Jan

    Eukaryotic cells often move in groups, a critical aspect of many biological and medical processes including wound healing, morphogenesis and cancer metastasis. Modeling can provide useful insights into the fundamental mechanisms of collective cell motility. Constructing models that incorporate the physical properties of the cells, however, is challenging. Here, I discuss our efforts to build a comprehensive cell motility model that includes cell membrane properties, cell-substrate interactions, cell polarity, and cell-cell interaction. The model will be applied to a variety of systems, including motion on micropatterned substrates and the migration of border cells in Drosophila. This work was supported by NIH Grant No. P01 GM078586 and NSF Grant No. 1068869.

  16. Motility of Mollicutes

    NASA Astrophysics Data System (ADS)

    Wolgemuth, Charles; Igoshin, Oleg; Oster, George

    2003-03-01

    Recent experiments show that the conformation of filament proteins play a role in the motility and morphology of many different types of bacteria. Conformational changes in the protein subunits may produce forces to drive propulsion and cell division. Here we present a molecular mechanism by which these forces can drive cell motion. Coupling of a biochemical cycle, such as ATP hydrolysis, to the dynamics of elastic filaments enable elastic filaments to propagate deformations that generate propulsive forces. We demonstrate this possibility for two classes of wall-less bacteria called mollicutes: the swimming of helical shaped Spiroplasma, and the gliding motility of Mycoplasma. Similar mechanisms may explain the locomotion of other prokaryotes, including the swimming of Synechococcus and the gliding of some myxobacteria.

  17. NCAM regulates cell motility.

    PubMed

    Prag, Søren; Lepekhin, Eugene A; Kolkova, Kateryna; Hartmann-Petersen, Rasmus; Kawa, Anna; Walmod, Peter S; Belman, Vadym; Gallagher, Helen C; Berezin, Vladimir; Bock, Elisabeth; Pedersen, Nina

    2002-01-15

    Cell migration is required during development of the nervous system. The regulatory mechanisms for this process, however, are poorly elucidated. We show here that expression of or exposure to the neural cell adhesion molecule (NCAM) strongly affected the motile behaviour of glioma cells independently of homophilic NCAM interactions. Expression of the transmembrane 140 kDa isoform of NCAM (NCAM-140) caused a significant reduction in cellular motility, probably through interference with factors regulating cellular attachment, as NCAM-140-expressing cells exhibited a decreased attachment to a fibronectin substratum compared with NCAM-negative cells. Ectopic expression of the cytoplasmic part of NCAM-140 also inhibited cell motility, presumably via the non-receptor tyrosine kinase p59(fyn) with which NCAM-140 interacts. Furthermore, we showed that the extracellular part of NCAM acted as a paracrine inhibitor of NCAM-negative cell locomotion through a heterophilic interaction with a cell-surface receptor. As we showed that the two N-terminal immunoglobulin modules of NCAM, which are known to bind to heparin, were responsible for this inhibition, we presume that this receptor is a heparan sulfate proteoglycan. A model for the inhibitory effect of NCAM is proposed, which involves competition between NCAM and extracellular components for the binding to membrane-associated heparan sulfate proteoglycan.

  18. Motility of Mycoplasma pneumoniae.

    PubMed Central

    Radestock, U; Bredt, W

    1977-01-01

    Cell of Mycoplasma pneumoniae FH gliding on a glass surface in liquid medium were examined by microscopic observation and quantitatively by microcinematography (30 frames per min). Comparisons were made only within the individual experiments. The cells moved in an irregular pattern with numerous narrow bends and circles. They never changed their leading end. The average speed (without pauses) was relatively constant between o.2 and 0.5 mum/s. The maximum speed was about 1.5 to 2.0 mum/s. The movements were interrupted by resting periods of different lengths and frequency. Temperature, viscosity, pH, and the presence of yeast extract in the medium influenced the motility significantly; changes in glucose, calcium ions, and serum content were less effective. The movements were affected by iodoacetate, p-mercuribenzoate, and mitomycin C at inhibitory or subinhibitory concentrations. Sodium fluoride, sodium cyanide, dinitrophenol, chloramphenicol, puromycin, cholchicin, and cytochalasin B at minimal inhibitory concentrations did not affect motility. The movements were effectively inhibited by anti-M. pneumoniae antiserum. Studies with absorbed antiserum suggested that the surface components involved in motility are heat labile. The gliding of M. pneumoniae cells required an intact energy metabolism and the proteins involved seemed to have a low turnover. Images PMID:14925

  19. Evolutionary aspects of collective motility in pathogenic bacteria

    NASA Astrophysics Data System (ADS)

    Deforet, Maxime; Xavier, Joao

    Pseudomonas aeruginosa is a pathogenic bacteria that can use its single polar flagellum to swim through liquids. It can move collectively over semisolid surfaces, a behavior called swarming. It can also settle and form surface-attached communities called biofilms that protect them from antibiotics. The transition from single motility (swimming) to collective motility (swarming) is biologically relevant as it enables exploring environments that a single bacterium cannot explore on its own. It is also clinically relevant since swarming and biofilm formation are thought to be antagonistic. We investigate the mechanisms of bacterial collective motility using a multidisciplinary approach that combines mathematical modeling, quantitative experiments, and microbial genetics. We aim to identify how these mechanisms may evolve under the selective pressure of population expansion, and consequently reinforce or hinder collective motility. In particular, we clarify the role of growth rate and motility in invasive populations.

  20. Mechanisms of growth cone repulsion

    PubMed Central

    Krull, Catherine E

    2010-01-01

    Research conducted in the last century suggested that chemoattractants guide cells or their processes to appropriate locations during development. Today, we know that many of the molecules involved in cellular guidance can act as chemorepellents that prevent migration into inappropriate territories. Here, we review some of the early seminal experiments and our current understanding of the underlying molecular mechanisms. PMID:20711492

  1. High motility reduces grazing mortality of planktonic bacteria.

    PubMed

    Matz, Carsten; Jürgens, Klaus

    2005-02-01

    We tested the impact of bacterial swimming speed on the survival of planktonic bacteria in the presence of protozoan grazers. Grazing experiments with three common bacterivorous nanoflagellates revealed low clearance rates for highly motile bacteria. High-resolution video microscopy demonstrated that the number of predator-prey contacts increased with bacterial swimming speed, but ingestion rates dropped at speeds of >25 microm s(-1) as a result of handling problems with highly motile cells. Comparative studies of a moderately motile strain (<25 microm s(-1)) and a highly motile strain (>45 microm s(-1)) further revealed changes in the bacterial swimming speed distribution due to speed-selective flagellate grazing. Better long-term survival of the highly motile strain was indicated by fourfold-higher bacterial numbers in the presence of grazing compared to the moderately motile strain. Putative constraints of maintaining high swimming speeds were tested at high growth rates and under starvation with the following results: (i) for two out of three strains increased growth rate resulted in larger and slower bacterial cells, and (ii) starved cells became smaller but maintained their swimming speeds. Combined data sets for bacterial swimming speed and cell size revealed highest grazing losses for moderately motile bacteria with a cell size between 0.2 and 0.4 microm(3). Grazing mortality was lowest for cells of >0.5 microm(3) and small, highly motile bacteria. Survival efficiencies of >95% for the ultramicrobacterial isolate CP-1 (< or =0.1 microm(3), >50 microm s(-1)) illustrated the combined protective action of small cell size and high motility. Our findings suggest that motility has an important adaptive function in the survival of planktonic bacteria during protozoan grazing.

  2. Basal bodies exhibit polarized positioning in zebrafish cone photoreceptors

    PubMed Central

    Ramsey, Michelle; Perkins, Brian D.

    2012-01-01

    The asymmetric positioning of basal bodies, and therefore cilia, is often critical for proper cilia function. This planar polarity is critical for motile cilia function but has not been extensively investigated for non-motile cilia or for sensory cilia such as vertebrate photoreceptors. Zebrafish photoreceptors form an organized mosaic ideal for investigating cilia positioning. We report that in the adult retina, the basal bodies of red, green-, and blue-sensitive cone photoreceptors localized asymmetrically on the cell edge nearest to the optic nerve. In contrast, no patterning was seen in the basal bodies of ultraviolet-sensitive cones or in rod photoreceptors. The asymmetric localization of basal bodies was consistent in all regions of the adult retina. Basal body patterning was unaffected in the cones of the XOPS-mCFP transgenic line, which lacks rod photoreceptors. Finally, the adult pattern was not seen in 7 day post fertilization (dpf) larvae as basal bodies were randomly distributed in all the photoreceptor subtypes. These results establish the asymmetrical localization of basal bodies in red-, green-, and blue-sensitive cones in adult zebrafish retinas but not in larvae. This pattern suggests an active cellular mechanism regulated the positioning of basal bodies after the transition to the adult mosaic and that rods do not seem to be necessary for the patterning of cone basal bodies. PMID:23171982

  3. The role of collapsing and cone rafting on eruption style changes and final cone morphology: Los Morados scoria cone, Mendoza, Argentina

    NASA Astrophysics Data System (ADS)

    Németh, Karoly; Risso, Corina; Nullo, Francisco; Kereszturi, Gabor

    2011-06-01

    Payún Matru Volcanic Field is a Quaternary monogenetic volcanic field that hosts scoria cones with perfect to breached morphologies. Los Morados complex is a group of at least four closely spaced scoria cones (Los Morados main cone and the older Cones A, B, and C). Los Morados main cone was formed by a long lived eruption of months to years. After an initial Hawaiian-style stage, the eruption changed to a normal Strombolian, conebuilding style, forming a cone over 150 metres high on a northward dipping (˜4°) surface. An initial cone gradually grew until a lava flow breached the cone's base and rafted an estimated 10% of the total volume. A sudden sector collapse initiated a dramatic decompression in the upper part of the feeding conduit and triggered violent a Strombolian style eruptive stage. Subsequently, the eruption became more stable, and changed to a regular Strombolian style that partially rebuilt the cone. A likely increase in magma flux coupled with the gradual growth of a new cone caused another lava flow outbreak at the structurally weakened earlier breach site. For a second time, the unstable flank of the cone was rafted, triggering a second violent Strombolian eruptive stage which was followed by a Hawaiian style lava fountain stage. The lava fountaining was accompanied by a steady outpour of voluminous lava emission accompanied by constant rafting of the cone flank, preventing the healing of the cone. Santa Maria is another scoria cone built on a nearly flat pre-eruption surface. Despite this it went through similar stages as Los Morados main cone, but probably not in as dramatic a manner as Los Morados. In contrast to these examples of large breached cones, volumetrically smaller cones, associated to less extensive lava flows, were able to heal raft/collapse events, due to the smaller magma output and flux rates. Our evidence shows that scoria cone growth is a complex process, and is a consequence of the magma internal parameters (e.g. volatile

  4. Cone visual pigments.

    PubMed

    Imamoto, Yasushi; Shichida, Yoshinori

    2014-05-01

    Cone visual pigments are visual opsins that are present in vertebrate cone photoreceptor cells and act as photoreceptor molecules responsible for photopic vision. Like the rod visual pigment rhodopsin, which is responsible for scotopic vision, cone visual pigments contain the chromophore 11-cis-retinal, which undergoes cis-trans isomerization resulting in the induction of conformational changes of the protein moiety to form a G protein-activating state. There are multiple types of cone visual pigments with different absorption maxima, which are the molecular basis of color discrimination in animals. Cone visual pigments form a phylogenetic sister group with non-visual opsin groups such as pinopsin, VA opsin, parapinopsin and parietopsin groups. Cone visual pigments diverged into four groups with different absorption maxima, and the rhodopsin group diverged from one of the four groups of cone visual pigments. The photochemical behavior of cone visual pigments is similar to that of pinopsin but considerably different from those of other non-visual opsins. G protein activation efficiency of cone visual pigments is also comparable to that of pinopsin but higher than that of the other non-visual opsins. Recent measurements with sufficient time-resolution demonstrated that G protein activation efficiency of cone visual pigments is lower than that of rhodopsin, which is one of the molecular bases for the lower amplification of cones compared to rods. In this review, the uniqueness of cone visual pigments is shown by comparison of their molecular properties with those of non-visual opsins and rhodopsin. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks. © 2013 Elsevier B.V. All rights reserved.

  5. Berkeley Lighting Cone

    SciTech Connect

    Lask, Kathleen; Gadgil, Ashok

    2016-10-24

    A lighting cone is a simple metal cone placed on the fuel bed of a stove during ignition to act as a chimney, increasing the draft through the fuel bed. Many stoves tend to be difficult to light due to poor draft through the fuel bed, so lighting cones are used in various parts of the world as an inexpensive accessory to help with ignition.

  6. MOTILE MARINE BACTERIA I.

    PubMed Central

    Leifson, Einar; Cosenza, B. J.; Murchelano, R.; Cleverdon, R. C.

    1964-01-01

    Leifson, Einar (Loyola University, Chicago, Ill.), B. J. Cosenza, R. Murchelano, and R. C. Cleverdon. Motile marine bacteria. I. Techniques, ecology, and general characteristics. J. Bacteriol. 87:652–666. 1964.—Aerobic, heterotrophic bacteria were isolated from the waters of the Long Island Sound, Narragansett Bay, Atlantic Ocean, and from the intestine of a variety of marine animals found along the shore of the Long Island Sound. A total of about 600 cultures of motile bacteria were studied morphologically and physiologically, with special emphasis on flagellar characteristics. The great majority of the bacteria isolated from the water were polar flagellate, nonfermentative, nonpigmented, and gramnegative. Most of these were straight, capsulated rods, but a considerable number were curved like vibrios. Yellow-pigmented isolates were often nonmotile, and the motile forms were most frequently subpolar flagellate. Several rosette-forming bacteria, including Caulobacter species, were isolated. Two typical spirilla and one flagellated coccus were found. Peritrichous flagellate bacteria, both gram-positive and gram-negative, were rare except in bottom mud. The normal intestinal flora of marine animals, such as fish and shellfish, consisted of polar flagellate, fermentative, non-pigmented, gram-negative, straight rods. Curved forms, like vibrios, were less common. Polar multitrichous flagellate forms were not uncommon and included all the luminescent types isolated. A considerable proportion of the polar monotrichous flagellate rods swarmed over the surface of agar media. When grown on solid media, all of these showed mixed polar and lateral flagellation; in liquid media, mainly polar flagellation was found. The ecology and general taxonomy of marine bacteria are discussed. Images PMID:14129669

  7. The Neural Cell Adhesion Molecule (NCAM) Promotes Clustering and Activation of EphA3 Receptors in GABAergic Interneurons to Induce Ras Homolog Gene Family, Member A (RhoA)/Rho-associated protein kinase (ROCK)-mediated Growth Cone Collapse.

    PubMed

    Sullivan, Chelsea S; Kümper, Maike; Temple, Brenda S; Maness, Patricia F

    2016-12-16

    Establishment of a proper balance of excitatory and inhibitory connectivity is achieved during development of cortical networks and adjusted through synaptic plasticity. The neural cell adhesion molecule (NCAM) and the receptor tyrosine kinase EphA3 regulate the perisomatic synapse density of inhibitory GABAergic interneurons in the mouse frontal cortex through ephrin-A5-induced growth cone collapse. In this study, it was demonstrated that binding of NCAM and EphA3 occurred between the NCAM Ig2 domain and EphA3 cysteine-rich domain (CRD). The binding interface was further refined through molecular modeling and mutagenesis and shown to be comprised of complementary charged residues in the NCAM Ig2 domain (Arg-156 and Lys-162) and the EphA3 CRD (Glu-248 and Glu-264). Ephrin-A5 induced co-clustering of surface-bound NCAM and EphA3 in GABAergic cortical interneurons in culture. Receptor clustering was impaired by a charge reversal mutation that disrupted NCAM/EphA3 association, emphasizing the importance of the NCAM/EphA3 binding interface for cluster formation. NCAM enhanced ephrin-A5-induced EphA3 autophosphorylation and activation of RhoA GTPase, indicating a role for NCAM in activating EphA3 signaling through clustering. NCAM-mediated clustering of EphA3 was essential for ephrin-A5-induced growth cone collapse in cortical GABAergic interneurons, and RhoA and a principal effector, Rho-associated protein kinase, mediated the collapse response. This study delineates a mechanism in which NCAM promotes ephrin-A5-dependent clustering of EphA3 through interaction of the NCAM Ig2 domain and the EphA3 CRD, stimulating EphA3 autophosphorylation and RhoA signaling necessary for growth cone repulsion in GABAergic interneurons in vitro, which may extend to remodeling of axonal terminals of interneurons in vivo.

  8. Symmetry-Breaking Motility

    NASA Astrophysics Data System (ADS)

    Lee, Allen; Lee, Ha Youn; Kardar, Mehran

    2005-09-01

    Locomotion of bacteria by actin polymerization and in vitro motion of spherical beads coated with a protein catalyzing polymerization are examples of active motility. Starting from a simple model of forces locally normal to the surface of a bead, we construct a phenomenological equation for its motion. The singularities at a continuous transition between moving and stationary beads are shown to be related to the symmetries of its shape. Universal features of the phase behavior are calculated analytically and confirmed by simulations. Fluctuations in velocity are shown to be generically non-Maxwellian and correlated to the shape of the bead.

  9. Cellular mechanics and motility

    NASA Astrophysics Data System (ADS)

    Hénon, Sylvie; Sykes, Cécile

    2015-10-01

    The term motility defines the movement of a living organism. One widely known example is the motility of sperm cells, or the one of flagellar bacteria. The propulsive element of such organisms is a cilium(or flagellum) that beats. Although cells in our tissues do not have a flagellum in general, they are still able to move, as we will discover in this chapter. In fact, in both cases of movement, with or without a flagellum, cell motility is due to a dynamic re-arrangement of polymers inside the cell. Let us first have a closer look at the propulsion mechanism in the case of a flagellum or a cilium, which is the best known, but also the simplest, and which will help us to define the hydrodynamic general conditions of cell movement. A flagellum is sustained by cellular polymers arranged in semi-flexible bundles and flagellar beating generates cell displacement. These polymers or filaments are part of the cellular skeleton, or "cytoskeleton", which is, in this case, external to the cellular main body of the organism. In fact, bacteria move in a hydrodynamic regime in which viscosity dominates over inertia. The system is thus in a hydrodynamic regime of low Reynolds number (Box 5.1), which is nearly exclusively the case in all cell movements. Bacteria and their propulsion mode by flagella beating are our unicellular ancestors 3.5 billion years ago. Since then, we have evolved to form pluricellular organisms. However, to keep the ability of displacement, to heal our wounds for example, our cells lost their flagellum, since it was not optimal in a dense cell environment: cells are too close to each other to leave enough space for the flagella to accomplish propulsion. The cytoskeleton thus developed inside the cell body to ensure cell shape changes and movement, and also mechanical strength within a tissue. The cytoskeleton of our cells, like the polymers or filaments that sustain the flagellum, is also composed of semi-flexible filaments arranged in bundles, and also in

  10. Spirochete motility and morpholgy

    NASA Astrophysics Data System (ADS)

    Charon, Nyles

    2004-03-01

    Spirochetes have a unique structure, and as a result their motility is different from that of other bacteria. These organisms can swim in a highly viscous, gel-like medium, such as that found in connective tissue, that inhibits the motility of most other bacteria. In spirochetes, the organelles for motility, the periplasmic flagella, reside inside the cell within the periplasmic space. A given periplasmic flagellum is attached only at one end of the cell, and depending on the species, may or may not overlap in the center of the cell. The number of periplasmic flagella varies from species to species. These structures have been shown to be directly involved in motility and function by rotating within the periplasmic space (1). The present talk focuses on the spirochete that causes Lyme disease, Borrelia burgdorferi. In many bacterial species, cell shape is usually dictated by the peptidoyglycan layer of the cell wall. In the first part of the talk, results will be presented that the morphology of B. burgdorferi is the result of a complex interaction between the cell cylinder and the internal periplasmic flagella resulting in a cell with a flat-wave morphology. Backward moving, propagating waves enable these bacteria to swim and translate in a given direction. Using targeted mutagenesis, we inactivated the gene encoding the major periplasmic flagellar filament protein FlaB. The resulting flaB mutants not only were non-motile, but were rod-shaped (2). Western blot analysis indicated that flaB was no longer synthesized, and electron microscopy revealed that the mutants were completely deficient in periplasmic flagella. Our results indicate that the periplasmic flagella of B. burgdorferi have a skeletal function. These organelles dynamically interact with the rod-shaped cell cylinder to enable the cell to swim, and to confer in part its flat-wave morphology The latter part of the talk concerns the basis for asymmetrical rotation of the periplasmic flagella of B

  11. Mechanics of motility initiation and motility arrest in crawling cells

    NASA Astrophysics Data System (ADS)

    Recho, Pierre; Putelat, Thibaut; Truskinovsky, Lev

    2015-11-01

    Motility initiation in crawling cells requires transformation of a symmetric state into a polarized state. In contrast, motility arrest is associated with re-symmetrization of the internal configuration of a cell. Experiments on keratocytes suggest that polarization is triggered by the increased contractility of motor proteins but the conditions of re-symmetrization remain unknown. In this paper we show that if adhesion with the extra-cellular substrate is sufficiently low, the progressive intensification of motor-induced contraction may be responsible for both transitions: from static (symmetric) to motile (polarized) at a lower contractility threshold and from motile (polarized) back to static (symmetric) at a higher contractility threshold. Our model of lamellipodial cell motility is based on a 1D projection of the complex intra-cellular dynamics on the direction of locomotion. In the interest of analytical transparency we also neglect active protrusion and view adhesion as passive. Despite the unavoidable oversimplifications associated with these assumptions, the model reproduces quantitatively the motility initiation pattern in fish keratocytes and reveals a crucial role played in cell motility by the nonlocal feedback between the mechanics and the transport of active agents. A prediction of the model that a crawling cell can stop and re-symmetrize when contractility increases sufficiently far beyond the motility initiation threshold still awaits experimental verification.

  12. Whole-transcriptome shotgun sequencing (RNA-seq) screen reveals upregulation of cellobiose and motility operons of Lactobacillus ruminis L5 during growth on tetrasaccharides derived from barley β-glucan.

    PubMed

    Lawley, Blair; Sims, Ian M; Tannock, Gerald W

    2013-09-01

    Lactobacillus ruminis is an inhabitant of human bowels and bovine rumens. None of 10 isolates (three from bovine rumen, seven from human feces) of L. ruminis that were tested could utilize barley β-glucan for growth. Seven of the strains of L. ruminis were, however, able to utilize tetrasaccharides (3-O-β-cellotriosyl-d-glucose [LDP4] or 4-O-β-laminaribiosyl-d-cellobiose [CDP4]) present in β-glucan hydrolysates for growth. The tetrasaccharides were generated by the use of lichenase or cellulase, respectively. To learn more about the utilization of tetrasaccharides by L. ruminis, whole-transcriptome shotgun sequencing (RNA-seq) was tested as a transcriptional screen to detect altered gene expression when an autochthonous human strain (L5) was grown in medium containing CDP4. RNA-seq results were confirmed and extended by reverse transcription-quantitative PCR assays of selected genes in two upregulated operons when cells were grown as batch cultures in medium containing either CDP4 or LDP4. The cellobiose utilization operon had increased transcription, particularly in early growth phase, whereas the chemotaxis/motility operon was upregulated in late growth phase. Phenotypic changes were seen in relation to upregulation of chemotaxis/flagellar operons: flagella were rarely seen by electron microscopy on glucose-grown cells but cells cultured in tetrasaccharide medium were commonly flagellated. Chemotactic movement toward tetrasaccharides was demonstrated in capillary cultures. L. ruminis utilized 3-O-β-cellotriosyl-d-glucose released by β-glucan hydrolysis due to bowel commensal Coprococcus sp., indicating that cross feeding of tetrasaccharide between bacteria could occur. Therefore, the RNA-seq screen and subsequent experiments had utility in revealing foraging attributes of gut commensal Lactobacillus ruminis.

  13. Whole-Transcriptome Shotgun Sequencing (RNA-seq) Screen Reveals Upregulation of Cellobiose and Motility Operons of Lactobacillus ruminis L5 during Growth on Tetrasaccharides Derived from Barley β-Glucan

    PubMed Central

    Lawley, Blair; Sims, Ian M.

    2013-01-01

    Lactobacillus ruminis is an inhabitant of human bowels and bovine rumens. None of 10 isolates (three from bovine rumen, seven from human feces) of L. ruminis that were tested could utilize barley β-glucan for growth. Seven of the strains of L. ruminis were, however, able to utilize tetrasaccharides (3-O-β-cellotriosyl-d-glucose [LDP4] or 4-O-β-laminaribiosyl-d-cellobiose [CDP4]) present in β-glucan hydrolysates for growth. The tetrasaccharides were generated by the use of lichenase or cellulase, respectively. To learn more about the utilization of tetrasaccharides by L. ruminis, whole-transcriptome shotgun sequencing (RNA-seq) was tested as a transcriptional screen to detect altered gene expression when an autochthonous human strain (L5) was grown in medium containing CDP4. RNA-seq results were confirmed and extended by reverse transcription-quantitative PCR assays of selected genes in two upregulated operons when cells were grown as batch cultures in medium containing either CDP4 or LDP4. The cellobiose utilization operon had increased transcription, particularly in early growth phase, whereas the chemotaxis/motility operon was upregulated in late growth phase. Phenotypic changes were seen in relation to upregulation of chemotaxis/flagellar operons: flagella were rarely seen by electron microscopy on glucose-grown cells but cells cultured in tetrasaccharide medium were commonly flagellated. Chemotactic movement toward tetrasaccharides was demonstrated in capillary cultures. L. ruminis utilized 3-O-β-cellotriosyl-d-glucose released by β-glucan hydrolysis due to bowel commensal Coprococcus sp., indicating that cross feeding of tetrasaccharide between bacteria could occur. Therefore, the RNA-seq screen and subsequent experiments had utility in revealing foraging attributes of gut commensal Lactobacillus ruminis. PMID:23851085

  14. Spirochete periplasmic flagella and motility.

    PubMed

    Li, C; Motaleb, A; Sal, M; Goldstein, S F; Charon, N W

    2000-10-01

    Spirochetes have a unique structure, and as a result their motility is different from that of other bacteria. They also have a special attribute: spirochetes can swim in a highly viscous, gel-like medium, such as that found in connective tissue, that inhibits the motility of most other bacteria. In spirochetes, the organelles for motility, the periplasmic flagella, reside inside the cell within the periplasmic space. A given periplasmic flagellum is attached only at one end of the cell, and depending on the species, may or may not overlap in the center of the cell with those attached at the other end. The number of periplasmic flagella varies from species to species. These structures have been shown to be directly involved in spirochete motility, and they function by rotating within the periplasmic space. The mechanics of motility also vary among the spirochetes. In Leptospira, a motility model developed several years ago has been extensively tested, and the evidence supporting this model is convincing. Borrelia burgdorferi swims differently, and a model of its motility has been recently put forward. This model is based on analyzing the motion of swimming cells, high voltage electron microscopy of fixed cells, and mutant analysis. To better understand spirochete motility on a more molecular level, the proteins and genes involved in motility are being analyzed. Spirochete periplasmic flagellar filaments are among the most complex of bacterial flagella. They are composed of the FlaA sheath proteins, and in many species, multiple FlaB core proteins. Allelic exchange mutagenesis of the genes which encode these proteins is beginning to yield important information with respect to periplasmic flagellar structure and function. Although we are at an early stage with respect to analyzing the function, organization, and regulation of many of the genes involved in spirochete motility, unique aspects have already become evident. Future studies on spirochete motility should be

  15. Cone sampling array models

    NASA Technical Reports Server (NTRS)

    Ahumada, Albert J., Jr.; Poirson, Allen

    1987-01-01

    A model is described for positioning cones in the retina. Each cone has a circular disk of influence, and the disks are tightly packed outward from the center. This model has three parameters that can vary with eccentricity: the mean radius of the cone disk, the standard deviation of the cone disk radius, and the standard deviation of postpacking jitter. Estimates for these parameters out to 1.6 deg are found by using measurements reported by Hirsch and Hylton (1985) and Hirsch and Miller (1987) of the positions of the cone inner segments of an adult macaque. The estimation is based on fitting measures of variation in local intercone distances, and the fit to these measures is good.

  16. The color cone.

    PubMed

    Logvinenko, Alexander D

    2015-02-01

    While the notion of a color cone can be found in writings of Maxwell, Helmholtz, Grassmann, and other scientists of the nineteenth century, it has not been clearly defined as yet. In this paper, the color cone is understood as the set of points in the cone excitation space produced by all possible lights. The spectral curve representing all the monochromatic lights is shown not to entirely belong to the color cone boundary, since its ends turn into the color cone interior. The monochromatic lights represented by the fragment of the spectral curve lying on the color cone boundary make up what is called the effective visible spectrum. The color cone is shown to be a convex hull of the conical surface through the fragment of the spectral curve representing the effective visible spectrum. The effective visible spectrum ends are shown to be determined by the photopigment spectral absorbance being independent of the prereceptor filters (e.g., the spectral transmittance of the lense and macular pigment).

  17. Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces.

    PubMed

    Hagai, Efrat; Dvora, Reut; Havkin-Blank, Tal; Zelinger, Einat; Porat, Ziv; Schulz, Stefan; Helman, Yael

    2014-05-01

    The ability to move on solid surfaces provides ecological advantages for bacteria, yet many bacterial species lack this trait. We found that Xanthomonas spp. overcome this limitation by making use of proficient motile bacteria in their vicinity. Using X. perforans and Paenibacillus vortex as models, we show that X. perforans induces surface motility, attracts proficient motile bacteria and 'rides' them for dispersal. In addition, X. perforans was able to restore surface motility of strains that lost this mode of motility under multiple growth cycles in the lab. The described interaction occurred both on agar plates and tomato leaves and was observed between several xanthomonads and motile bacterial species. Thus, suggesting that this motility induction and hitchhiking strategy might be widespread and ecologically important. This study provides an example as to how bacteria can rely on the abilities of their neighboring species for their own benefit, signifying the importance of a communal organization for fitness.

  18. RNA interference targeting against S100A4 suppresses cell growth and motility and induces apoptosis in human pancreatic cancer cells

    SciTech Connect

    Tabata, Takahiro; Tsukamoto, Nobukazu; Fooladi, Abbas Ali Imani; Yamanaka, Sumitaka; Furukawa, Toru; Ishida, Masaharu; Sato, Daisuke; Gu, Zhaodi; Nagase, Hiroki; Egawa, Shinichi; Sunamura, Makoto; Horii, Akira

    2009-12-18

    S100A4 protein belongs to the S100 subfamily, which has grown to be one of the large subfamilies of the EF-hand Ca{sup 2+}-binding proteins, and overexpression of S100A4 is suggested to associate with cell proliferation, invasion, and metastasis. We observed frequent overexpression of S100A4 in pancreatic cancer cell lines and further analyzed RNAi-mediated knockdown to address the possibility of its use as a therapeutic target for pancreatic cancer. The specific knockdown of S100A4 strongly suppressed cell growth, induced G2 arrest and eventual apoptosis, and decreased cell migration. Furthermore, microarray analyses revealed that knockdown of S100A4 induced expression of the tumor suppressor genes PRDM2 and VASH1. Our present results suggest the possibility that the inhibition of S100A4 can be utilized in antitumor applications for patients with pancreatic cancer.

  19. Rimonabant, Gastrointestinal Motility and Obesity

    PubMed Central

    Sun, Yan; Chen, Jiande

    2012-01-01

    Background: Obesity and overweight affect more than half of the US population and are associated with a number of diseases. Rimonabant, a cannabinoid receptor 1 blocker in the endocannabinoid (EC) system, was indicated in Europe for the treatment of obesity and overweight patients with associated risk factors but withdrawn on Jan, 2009 because of side effects. Many studies have reported the effects of rimonabant on gastrointestinal (GI) motility and food intake. The aims of this review are: to review the relationship of EC system with GI motility and food intake;to review the studies of rimonabant on GI motility, food intake and obesity;and to report the tolerance and side effects of rimonabant. Methods: the literature (Pubmed database) was searched using keywords: rimonabant, obesity and GI motility. Results: GI motility is related with appetite, food intake and nutrients absorption. The EC system inhibits GI motility, reduces emesis and increases food intake; Rimonabant accelerates gastric emptying and intestinal transition but decreases energy metabolism and food intake. There is rapid onset of tolerance to the prokinetic effect of rimonabant. The main side effects of rimonabant are depression and GI symptoms. Conclusions: Rimonabant has significant effects on energy metabolism and food intake, probably mediated via its effects on GI motility. PMID:23449551

  20. 2017 Eclipse Shadow Cones

    NASA Image and Video Library

    A solar eclipse occurs when the Moon's shadow falls on the Earth. The shadow comprises two concentric cones called the umbra and the penumbra. Within the smaller, central umbra, the Sun is complete...

  1. HSURIA Cone Centration.

    DTIC Science & Technology

    1981-09-01

    laser. b. Interferometer configuration. This configuration (Fig. 4) uses a Twyman -Green interferometer to measure the cone centration for comparison...autocollimator. The interferometer mode, as was explained in Section Ill-l, gave very little information about the alignment of the cone. c. Physical...the camera turning flat (5) must be removed and the centration sensor laser is used. The interferometer laser is turned off. For the interferometer

  2. Filamin B Plays a Key Role in Vascular Endothelial Growth Factor-induced Endothelial Cell Motility through Its Interaction with Rac-1 and Vav-2*

    PubMed Central

    del Valle-Pérez, Beatriz; Martínez, Vanesa Gabriela; Lacasa-Salavert, Cristina; Figueras, Agnès; Shapiro, Sandor S.; Takafuta, Toshiro; Casanovas, Oriol; Capellà, Gabriel; Ventura, Francesc; Viñals, Francesc

    2010-01-01

    Actin-binding proteins filamin A (FLNA) and B (FLNB) are expressed in endothelial cells and play an essential role during vascular development. In order to investigate their role in adult endothelial cell function, we initially confirmed their expression pattern in different adult mouse tissues and cultured cell lines and found that FLNB expression is concentrated mainly in endothelial cells, whereas FLNA is more ubiquitously expressed. Functionally, small interfering RNA knockdown of endogenous FLNB in human umbilical vein endothelial cells inhibited vascular endothelial growth factor (VEGF)-induced in vitro angiogenesis by decreasing endothelial cell migration capacity, whereas FLNA ablation did not alter these parameters. Moreover, FLNB-depleted cells increased their substrate adhesion with more focal adhesions. The molecular mechanism underlying this effect implicates modulation of small GTP-binding protein Rac-1 localization and activity, with altered activation of its downstream effectors p21 protein Cdc42/Rac-activated kinase (PAK)-4/5/6 and its activating guanine nucleotide exchange factor Vav-2. Moreover, our results suggest the existence of a signaling complex, including FLNB, Rac-1, and Vav-2, under basal conditions that would further interact with VEGFR2 and integrin αvβ5 after VEGF stimulation. In conclusion, our results reveal a crucial role for FLNB in endothelial cell migration and in the angiogenic process in adult endothelial cells. PMID:20110358

  3. Mechanosensitivity in axon growth and guidance

    NASA Astrophysics Data System (ADS)

    Urbach, Jeff

    2013-03-01

    In the developing nervous system, axons respond to a diverse array of cues to generate the intricate connection network required for proper function. The growth cone, a highly motile structure at the tip of a growing axon, integrates information about the local environment and modulates outgrowth and guidance, but little is known about effects of external mechanical cues and internal mechanical forces on growth cone behavior. We have investigated axon outgrowth and force generation on soft elastic substrates for dorsal root ganglion (DRG) neurons (from the peripheral nervous system) and hippocampal neurons (from the central) to see how the mechanics of the microenvironment affect different populations. We find that force generation and stiffness-dependent outgrowth are strongly dependent on cell type. We also observe very different internal dynamics and substrate coupling in the two populations, suggesting that the difference in force generation is due to stronger adhesions and therefore stronger substrate engagement in the peripheral nervous system neurons. We will discuss the biological origins of these differences, and recent analyses of the dynamic aspects of growth cone force generation and the implications for the role of mechanosensitivity in axon guidance. In collaboration with D. Koch, W. Rosoff, and H. M. Geller. Supported by NINDS grant 1R01NS064250-01 (J.S.U.) and the NHLBI Intramural Research Program (H.M.G.).

  4. Gastrointestinal Motility Disorders in Children

    PubMed Central

    Ambartsumyan, Lusine

    2014-01-01

    The most common and challenging gastrointestinal motility disorders in children include gastroesophageal reflux disease (GERD), esophageal achalasia, gastroparesis, chronic intestinal pseudo-obstruction, and constipation. GERD is the most common gastrointestinal motility disorder affecting children and is diagnosed clinically and treated primarily with acid secretion blockade. Esophageal achalasia, a less common disorder in the pediatric patient population, is characterized by dysphagia and treated with pneumatic balloon dilation and/or esophagomyotomy. Gastroparesis and chronic intestinal pseudo-obstruction are poorly characterized in children and are associated with significant morbidity. Constipation is among the most common complaints in children and is associated with significant morbidity as well as poor quality of life. Data on epidemiology and outcomes, clinical trials, and evaluation of new diagnostic techniques are needed to better diagnose and treat gastrointestinal motility disorders in children. We present a review of the conditions and challenges related to these common gastrointestinal motility disorders in children. PMID:24799835

  5. Shape determination in motile cells

    NASA Astrophysics Data System (ADS)

    Mogilner, Alex

    2010-03-01

    Flat, simple shaped, rapidly gliding fish keratocyte cell is the model system of choice to study cell motility. The cell motile appendage, lamellipod, has a characteristic bent-rectangular shape. Recent experiments showed that the lamellipodial geometry is tightly correlated with cell speed and with actin dynamics. These quantitative data combined with computational modeling suggest that a model for robust actin treadmill inside the 'unstretchable membrane bag'. According to this model, a force balance between membrane tension and growing and pushing actin network distributed unevenly along the cell periphery can explain the cell shape and motility. However, when adhesion of the cell to the surface weakens, the actin dynamics become less regular, and myosin-powered contraction starts playing crucial role in stabilizing the cell shape. I will illustrate how the combination of theoretical and experimental approaches helped to unravel the keratocyte motile behavior.

  6. Surface motility of Myxococcus Xanthus

    NASA Astrophysics Data System (ADS)

    Gibiansky, Maxsim; Hu, William; Jin, Fan; Zhao, Kun; Shi, Wenyuan; Wong, Gerard

    2011-03-01

    We examine the surface motility of Myxococcus Xanthus, a bacterium species found in soil that exhibits a broad range of self-organizing behavior, including predatory ``swarms'' and survival-enhancing ``fruiting bodies.'' To quantify the effects of exopolysaccharides (EPS) on surface adhesion and motility, we use modified versions of particle tracking algorithms from colloid physics to analyze bacterial trajectories, and compare the wild type (WT) strain to EPS knockout and EPS overproducer strains. We find that EPS deficiency leads to an increase in the number of ``standing'' bacteria oriented normal to the surface, attached by one end with minimal motility. EPS overproduction, by contrast, suppresses this phenotype. A detailed investigation of the influence of EPS on Myxococcus social motility will be presented.

  7. The Salmonella enterica serovar Typhimurium QseB Response Regulator Negatively Regulates Bacterial Motility and Swine Colonization in the Absence of the QseC Sensor Kinase

    USDA-ARS?s Scientific Manuscript database

    Salmonella enterica serovar Typhimurium (S. Typhimurium) responds to the catecholamine, norepinephrine by increasing bacterial growth and enhancing motility. In this study, iron with or without the siderophore, ferrioxamine E also enhanced bacterial motility. Iron-enhanced motility was growth-rate ...

  8. Elenoside increases intestinal motility

    PubMed Central

    Navarro, E; Alonso, SJ; Navarro, R; Trujillo, J; Jorge, E

    2006-01-01

    AIM: To study the effects of elenoside, an arylnaph-thalene lignan from Justicia hyssopifolia, on gastro-intestinal motility in vivo and in vitro in rats. METHODS: Routine in vivo experimental assessments were catharsis index, water percentage of boluses, intestinal transit, and codeine antagonism. The groups included were vehicle control (propylene glycol-ethanol-plant oil-tween 80), elenoside (i.p. 25 and 50 mg/kg), cisapride (i.p. 10 mg/kg), and codeine phosphate (intragastric route, 50 mg/kg). In vitro approaches used isolated rat intestinal tissues (duodenum, jejunum, and ileum). The effects of elenoside at concentrations of 3.2 x 10-4, 6.4 x 10-4 and 1.2 x 10-3 mol/L, and cisapride at 10-6 mol/L were investigated. RESULTS: Elenoside in vivo produced an increase in the catharsis index and water percentage of boluses and in the percentage of distance traveled by a suspension of activated charcoal. Codeine phosphate antagonized the effect of 25 mg/kg of elenoside. In vitro, elenoside in duodenum, jejunum and ileum produced an initial decrease in the contraction force followed by an increase. Elenoside resulted in decreased intestinal frequency in duodenum, jejunum, and ileum. The in vitro and in vivo effects of elenoside were similar to those produced by cisapride. CONCLUSION: Elenoside is a lignan with an action similar to that of purgative and prokinetics drugs. Elenoside, could be an alternative to cisapride in treatment of gastrointestinal diseases as well as a preventive therapy for the undesirable gastrointestinal effects produced by opioids used for mild to moderate pain. PMID:17131476

  9. Eph/ephrin interactions modulate muscle satellite cell motility and patterning

    PubMed Central

    Stark, Danny A.; Karvas, Rowan M.; Siegel, Ashley L.; Cornelison, D. D. W.

    2011-01-01

    During development and regeneration, directed migration of cells, including neural crest cells, endothelial cells, axonal growth cones and many types of adult stem cells, to specific areas distant from their origin is necessary for their function. We have recently shown that adult skeletal muscle stem cells (satellite cells), once activated by isolation or injury, are a highly motile population with the potential to respond to multiple guidance cues, based on their expression of classical guidance receptors. We show here that, in vivo, differentiated and regenerating myofibers dynamically express a subset of ephrin guidance ligands, as well as Eph receptors. This expression has previously only been examined in the context of muscle-nerve interactions; however, we propose that it might also play a role in satellite cell-mediated muscle repair. Therefore, we investigated whether Eph-ephrin signaling would produce changes in satellite cell directional motility. Using a classical ephrin ‘stripe’ assay, we found that satellite cells respond to a subset of ephrins with repulsive behavior in vitro; patterning of differentiating myotubes is also parallel to ephrin stripes. This behavior can be replicated in a heterologous in vivo system, the hindbrain of the developing quail, in which neural crest cells are directed in streams to the branchial arches and to the forelimb of the developing quail, where presumptive limb myoblasts emigrate from the somite. We hypothesize that guidance signaling might impact multiple steps in muscle regeneration, including escape from the niche, directed migration to sites of injury, cell-cell interactions among satellite cell progeny, and differentiation and patterning of regenerated muscle. PMID:22071104

  10. The cone dysfunction syndromes

    PubMed Central

    Aboshiha, Jonathan; Dubis, Adam M; Hardcastle, Alison J; Michaelides, Michel

    2016-01-01

    The cone dysfunction syndromes are a heterogeneous group of inherited, predominantly stationary retinal disorders characterised by reduced central vision and varying degrees of colour vision abnormalities, nystagmus and photophobia. This review details the following conditions: complete and incomplete achromatopsia, blue-cone monochromatism, oligocone trichromacy, bradyopsia and Bornholm eye disease. We describe the clinical, psychophysical, electrophysiological and imaging findings that are characteristic to each condition in order to aid their accurate diagnosis, as well as highlight some classically held notions about these diseases that have come to be challenged over the recent years. The latest data regarding the genetic aetiology and pathological changes observed in the cone dysfunction syndromes are discussed, and, where relevant, translational avenues of research, including completed and anticipated interventional clinical trials, for some of the diseases described herein will be presented. Finally, we briefly review the current management of these disorders. PMID:25770143

  11. Insulin Receptor Signaling in Cones*

    PubMed Central

    Rajala, Ammaji; Dighe, Radhika; Agbaga, Martin-Paul; Anderson, Robert E.; Rajala, Raju V.S.

    2013-01-01

    In humans, age-related macular degeneration and diabetic retinopathy are the most common disorders affecting cones. In retinitis pigmentosa (RP), cone cell death precedes rod cell death. Systemic administration of insulin delays the death of cones in RP mouse models lacking rods. To date there are no studies on the insulin receptor signaling in cones; however, mRNA levels of IR signaling proteins are significantly higher in cone-dominant neural retina leucine zipper (Nrl) knock-out mouse retinas compared with wild type rod-dominant retinas. We previously reported that conditional deletion of the p85α subunit of phosphoinositide 3-kinase (PI3K) in cones resulted in age-related cone degeneration, and the phenotype was not rescued by healthy rods, raising the question of why cones are not protected by the rod-derived cone survival factors. Interestingly, systemic administration of insulin has been shown to delay the death of cones in mouse models of RP lacking rods. These observations led to the hypothesis that cones may have their own endogenous neuroprotective pathway, or rod-derived cone survival factors may be signaled through cone PI3K. To test this hypothesis we generated p85α−/−/Nrl−/− double knock-out mice and also rhodopsin mutant mice lacking p85α and examined the effect of the p85α subunit of PI3K on cone survival. We found that the rate of cone degeneration is significantly faster in both of these models compared with respective mice with competent p85α. These studies suggest that cones may have their own endogenous PI3K-mediated neuroprotective pathway in addition to the cone viability survival signals derived from rods. PMID:23673657

  12. Use of diatom motility features as endpoints of metolachlor toxicity.

    PubMed

    Coquillé, Nathalie; Jan, Gwilherm; Moreira, Aurélie; Morin, Soizic

    2015-01-01

    Many recent ecotoxicological studies suggest a relationship between freshwater contamination and increasing abundances of motile diatoms (potentially able to move). The capacity to escape would present advantages to species in polluted environments. However, actual motility as a response to toxicants had not been described and required experimental validation. We designed a specific experiment to assess how a field-isolated diatom (Gomphonema gracile) distributes energy to in situ resistance (increased population growth or photosynthesis) and escape (behavioral changes), when exposed to increasing concentrations of the herbicide metolachlor. We report here the dose-time dependent responses of G. gracile populations. They coped with low contamination by resisting in situ, with early hormetic responses highlighted by stimulation of chlorophyll-a fluorescence. At a higher dose, harmful impacts were observed on growth after a few days, but an earlier behavioral response suggested that higher motility (percentage of motile individuals and mean distance crossed) could be involved in escape. Our findings bring new arguments to support the implementation of real measurements instead of motility traits in toxicity assessment. Specifically, motion descriptors have been used as early-warning indicators of contamination in our study. Further works should address the reliability of these endpoints in more complex conditions (interspecific variability, behavior in the field). Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Loss of mTOR signaling affects cone function, cone structure and expression of cone specific proteins without affecting cone survival.

    PubMed

    Ma, Shan; Venkatesh, Aditya; Langellotto, Fernanda; Le, Yun Z; Hall, Michael N; Rüegg, Markus A; Punzo, Claudio

    2015-06-01

    Cones are the primary photoreceptor (PR) cells responsible for vision in humans. They are metabolically highly active requiring phosphoinositide 3-kinase (PI3K) activity for long-term survival. One of the downstream targets of PI3K is the kinase mammalian target of rapamycin (mTOR), which is a key regulator of cell metabolism and growth, integrating nutrient availability and growth factor signals. Both PI3K and mTOR are part of the insulin/mTOR signaling pathway, however if mTOR is required for long-term PR survival remains unknown. This is of particular interest since deregulation of this pathway in diabetes results in reduced PR function before the onset of any clinical signs of diabetic retinopathy. mTOR is found in two distinct complexes (mTORC1 & mTORC2) that are characterized by their unique accessory proteins RAPTOR and RICTOR respectively. mTORC1 regulates mainly cell metabolism in response to nutrient availability and growth factor signals, while mTORC2 regulates pro-survival mechanisms in response to growth factors. Here we analyze the effect on cones of loss of mTORC1, mTORC2 and simultaneous loss of mTORC1 & mTORC2. Interestingly, neither loss of mTORC1 nor mTORC2 affects cone function or survival at one year of age. However, outer and inner segment morphology is affected upon loss of either complex. In contrast, concurrent loss of mTORC1 and mTORC2 leads to a reduction in cone function without affecting cone viability. The data indicates that PI3K mediated pro-survival signals diverge upstream of both mTOR complexes in cones, suggesting that they are independent of mTOR activity. Furthermore, the data may help explain why PR function is reduced in diabetes, which can lead to deregulation of both mTOR complexes simultaneously. Finally, although mTOR is a key regulator of cell metabolism, and PRs are metabolically highly active, the data suggests that the role of mTOR in regulating the metabolic transcriptome in healthy cones is minimal. Copyright

  14. Shatter Cones: (Mis)understood?

    NASA Astrophysics Data System (ADS)

    Osinski, G. R.; Ferrière, L.

    2016-08-01

    In this study we provide new observations of shatter cones from several complex impact craters in various target rocks and in different preservation states. We show that shatter cones are present in several stratigraphic settings.

  15. Esophageal motility disorders: medical therapy.

    PubMed

    Lacy, Brian E; Weiser, Kirsten

    2008-01-01

    Symptoms of chest pain and dysphagia are common in the adult population. Most patients initially undergo an evaluation to exclude anatomic causes (ie, esophagitis, stricture) and cardiovascular disease as the etiology of these symptoms. Patients with persistent symptoms may then be referred for specialized testing of the esophagus, including esophageal manometry. Disorders of esophageal motility, which include achalasia, diffuse esophageal spasm, nutcracker esophagus, hypertensive lower esophageal sphincter, and ineffective motility are often identified in these patients. Unfortunately, the etiology of these disorders has not been well characterized and the treatment has not been standardized. This review will briefly discuss the impact, etiology, and diagnosis of esophageal motility disorders, and then focus on the medical management of these disorders using evidence from well-designed, prospective studies, where available.

  16. Reconstruction from cone integral transforms

    NASA Astrophysics Data System (ADS)

    Palamodov, Victor

    2017-10-01

    The paper contains new reconstruction formulas for a function on 3D space from data of its cone integrals with fixed opening and integrable weight. In the case of cone integrals with the (non integrable) weight modelling photometric law, a reconstruction is obtained for the non redundant data of cones with the apex running on a curve.

  17. Cone on Olympus Mons

    NASA Image and Video Library

    2005-10-24

    This image from NASA 2001 Mars Odyssey spacecraft shows just a small part of the eastern flank of Olympus Mons. On the far left side of the image a small volcanic cone can be seen. The shadow helps to identify this feature.

  18. Motility of Electric Cable Bacteria.

    PubMed

    Bjerg, Jesper Tataru; Damgaard, Lars Riis; Holm, Simon Agner; Schramm, Andreas; Nielsen, Lars Peter

    2016-07-01

    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. 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. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  19. Brow motility in mitochondrial myopathy.

    PubMed

    de Castro, Flávia Augusta Attié; Cruz, Antonio Augusto V; Sobreira, Cláudia Ferreira da Rosa

    2010-01-01

    To quantify the range of brow excursion in patients with mitochondrial myopathy and chronic progressive external ophthalmoplegia (CPEO). Comparative case series. Digital image processing techniques were used to quantify the upper eyelid resting position, brow excursion, and monocular eye movements (ductions) in 19 patients with mitochondrial myopathy and CPEO and in 27 healthy control subjects. All patients with CPEO had ptosis ranging from 0.6 to 8 mm. For most patients, eye motility limitation was symmetrical. Elevation was the most affected eye movement. Patient's brow motility was on average 56.7% of the motility seen in the control group, and did not correlate with age or eye motility in any direction. Seventy-six percent of the brows displayed more than 2 mm of excursion. In patients with CPEO, the occipitofrontalis muscle is less affected than the extraocular muscles. Most patients display a useful degree of brow excursion that theoretically can be used to clear the visual axis after a conservative brow suspension.

  20. 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

  1. Preparation, imaging, and quantification of bacterial surface motility assays.

    PubMed

    Morales-Soto, Nydia; Anyan, Morgen E; Mattingly, Anne E; Madukoma, Chinedu S; Harvey, Cameron W; Alber, Mark; Déziel, Eric; Kearns, Daniel B; Shrout, Joshua D

    2015-04-07

    Bacterial surface motility, such as swarming, is commonly examined in the laboratory using plate assays that necessitate specific concentrations of agar and sometimes inclusion of specific nutrients in the growth medium. The preparation of such explicit media and surface growth conditions serves to provide the favorable conditions that allow not just bacterial growth but coordinated motility of bacteria over these surfaces within thin liquid films. Reproducibility of swarm plate and other surface motility plate assays can be a major challenge. Especially for more "temperate swarmers" that exhibit motility only within agar ranges of 0.4%-0.8% (wt/vol), minor changes in protocol or laboratory environment can greatly influence swarm assay results. "Wettability", or water content at the liquid-solid-air interface of these plate assays, is often a key variable to be controlled. An additional challenge in assessing swarming is how to quantify observed differences between any two (or more) experiments. Here we detail a versatile two-phase protocol to prepare and image swarm assays. We include guidelines to circumvent the challenges commonly associated with swarm assay media preparation and quantification of data from these assays. We specifically demonstrate our method using bacteria that express fluorescent or bioluminescent genetic reporters like green fluorescent protein (GFP), luciferase (lux operon), or cellular stains to enable time-lapse optical imaging. We further demonstrate the ability of our method to track competing swarming species in the same experiment.

  2. Control of actin-based motility through localized actin binding

    PubMed Central

    Banigan, Edward J.; Lee, Kun-Chun; Liu, Andrea J.

    2014-01-01

    A wide variety of cell biological and biomimetic systems use actin polymerization to drive motility. It has been suggested that an object such as a bacterium can propel itself by self-assembling a high concentration of actin behind it if it is repelled by actin. However, it is also known that it is essential for the moving object to bind actin. Therefore, a key question is how the actin tail can propel an object when it both binds and repels the object. We present a physically consistent Brownian dynamics model for actin-based motility that includes the minimal components of the dendritic nucleation model and allows for both attractive and repulsive interactions between actin and a moveable disk. We find that the concentration gradient of filamentous actin generated by polymerization is sufficient to propel the object, even with moderately strong binding interactions. Additionally, actin binding can act as a biophysical cap, and may directly control motility through modulation of network growth. Overall, this mechanism is robust in that it can drive motility against a load up to a stall pressure that depends on the Young’s modulus of the actin network and can explain several aspects of actin-based motility. PMID:24225232

  3. 3D timelapse analysis of muscle satellite cell motility.

    PubMed

    Siegel, Ashley L; Atchison, Kevin; Fisher, Kevin E; Davis, George E; Cornelison, D D W

    2009-10-01

    Skeletal muscle repair and regeneration requires the activity of satellite cells, a population of myogenic stem cells scattered throughout the tissue and activated to proliferate and differentiate in response to myotrauma or disease. While it seems likely that satellite cells would need to navigate local muscle tissue to reach damaged areas, relatively little data on such motility exist, and most studies have been with immortalized cell lines. We find that primary satellite cells are significantly more motile than myoblast cell lines, and that adhesion to laminin promotes primary cell motility more than fourfold over other substrates. Using timelapse videomicroscopy to assess satellite cell motility on single living myofibers, we have identified a requirement for the laminin-binding integrin alpha 7 beta 1 in satellite cell motility, as well as a role for hepatocyte growth factor in promoting directional persistence. The extensive migratory behavior of satellite cells resident on muscle fibers suggests caution when determining, based on fixed specimens, whether adjacent cells are daughters from the same mother cell. We also observed more persistent long-term contact between individual satellite cells than has been previously supposed, potential cell-cell attractive and repulsive interactions, and migration between host myofibers. Based on such activity, we assayed for expression of "pathfinding" cues, and found that satellite cells express multiple guidance ligands and receptors. Together, these data suggest that satellite cell migration in vivo may be more extensive than currently thought, and could be regulated by combinations of signals, including adhesive haptotaxis, soluble factors, and guidance cues.

  4. Esophageal motility in eosinophilic esophagitis.

    PubMed

    Weiss, A H; Iorio, N; Schey, R

    2015-01-01

    Eosinophilic esophagitis (EoE) is characterized by eosinophilic infiltration of the esophagus and is a potential cause of dysphagia and food impaction, most commonly affecting young men. Esophageal manometry findings vary from normal motility to aperistalsis, simultaneous contractions, diffuse esophageal spasm, nutcracker esophagus or hypotonic lower esophageal sphincter (LES). It remains unclear whether esophageal dysmotility plays a significant role in the clinical symptoms of EoE. Our aim is to review the pathogenesis, diagnosis, and effect of treatment on esophageal dysmotility in EoE. A literature search utilizing the PubMed database was performed using keywords: eosinophilic esophagitis, esophageal dysmotility, motility, manometry, impedance planimetry, barium esophagogram, endoscopic ultrasound, and dysphagia. Fifteen studies, totaling 387 patients with eosinophilic esophagitis were identified as keeping in accordance with the aim of this study and included in this review. The occurrence of abnormal esophageal manometry was reported to be between 4 and 87% among patients with EoE. Esophageal motility studies have shown reduced distensibility, abnormal peristalsis, and hypotonicity of the LES in patients with EoE, which may also mimic other esophageal motility disorders such as achalasia or nutcracker esophagus. Studies have shown conflicting results regarding the presence of esophageal dysmotility and symptoms with some reports suggesting a higher rate of food impaction, while others report no correlation between motor function and dysphagia. Motility dysfunction of the esophagus in EoE has not been well reported in the literature and studies have reported conflicting evidence regarding the clinical significance of dysmotility seen in EoE. The correlation between esophageal dysmotility and symptoms of EoE remains unclear. Larger studies are needed to investigate the incidence of esophageal dysmotility, clinical implications, and effect of treatment on

  5. Corticotropin Releasing Factor promotes breast cancer cell motility and invasiveness

    PubMed Central

    Androulidaki, Ariadne; Dermitzaki, Erini; Venihaki, Maria; Karagianni, Effie; Rassouli, Olga; Andreakou, Erini; Stournaras, Christos; Margioris, Andrew N; Tsatsanis, Christos

    2009-01-01

    Introduction Cancer cells secrete bioactive peptides that act in an autocrine or paracrine fashion affecting tumor growth and metastasis. Corticotropin-releasing factor (CRF), a hypothalamic neuropeptide that controls the response to stress, has been detected in breast cancer tissues and cell lines. CRF can affect breast cancer cells in an autocrine or paracrine manner via its production from innervating sympathetic neurons or immune cells. Methods In the present study we report our findings regarding the impact of CRF on breast cancer cell motility and invasiveness. For this purpose we used the MCF7 breast cancer cell line and evaluated the effect of CRF on motility and invasiveness using the wound-healing and boyden-chamber assays. In addition, we measured the effect of CRF on molecules that mediate motility by western blot, immunofluorescence, ELISA and RT-PCR. Results Our findings show that: 1. CRF transiently inhibited the apoptosis of MCF7 cells. 2. CRF enhanced MCF7 cell motility in a wound healing assay and their invasiveness through extracellular matrix. 3. CRF increased actin polymerization, phosphorylation of Focal Adhesion Kinase (FAK), providing a potential mechanism for the observed induction of MCF7 motility. 4. CRF induced the expression of Cox-1 but not Cox-2 in MCF7 cells as well as the production of prostaglandins, factors known to promote invasiveness and metastasis. Conclusion Overall, our data suggest that CRF stimulates cell motility and invasiveness of MCF7 cells most probably via induction of FAK phosphorylation and actin filament reorganization and production of prostaglandins via Cox1. Based on these findings we postulate that the stress neuropeptide CRF present in the vicinity of tumors (either produced locally by the tumor cells themselves or by nearby normal cells or secreted from the innervations of surrounding tissues) may play an important role on breast tumor growth and metastatic capacity, providing a potential link between stress

  6. How VASP enhances actin-based motility

    PubMed Central

    Samarin, Stanislav; Romero, Stéphane; Kocks, Christine; Didry, Dominique; Pantaloni, Dominique; Carlier, Marie-France

    2003-01-01

    The function of vasodilator-stimulated phosphoprotein (VASP) in motility is analyzed using a biomimetic motility assay in which ActA-coated microspheres propel themselves in a medium containing actin, the Arp2/3 complex, and three regulatory proteins in the absence or presence of VASP. Propulsion is linked to cycles of filament barbed end attachment-branching-detachment-growth in which the ActA-activated Arp2/3 complex incorporates at the junctions of branched filaments. VASP increases the velocity of beads. VASP increases branch spacing of filaments in the actin tail, as it does in lamellipodia in living cells. The effect of VASP on branch spacing of Arp2/3-induced branched actin arrays is opposed to the effect of capping proteins. However, VASP does not compete with capping proteins for binding barbed ends of actin filaments. VASP enhances branched actin polymerization only when ActA is immobilized on beads or on Listeria. VASP increases the rate of dissociation of the branch junction from immobilized ActA, which is the rate-limiting step in the catalytic cycle of site-directed filament branching. PMID:14557252

  7. Light cone matrix product

    SciTech Connect

    Hastings, Matthew B

    2009-01-01

    We show how to combine the light-cone and matrix product algorithms to simulate quantum systems far from equilibrium for long times. For the case of the XXZ spin chain at {Delta} = 0.5, we simulate to a time of {approx} 22.5. While part of the long simulation time is due to the use of the light-cone method, we also describe a modification of the infinite time-evolving bond decimation algorithm with improved numerical stability, and we describe how to incorporate symmetry into this algorithm. While statistical sampling error means that we are not yet able to make a definite statement, the behavior of the simulation at long times indicates the appearance of either 'revivals' in the order parameter as predicted by Hastings and Levitov (e-print arXiv:0806.4283) or of a distinct shoulder in the decay of the order parameter.

  8. Shatter cones: Diagnostic impact signatures

    NASA Technical Reports Server (NTRS)

    Mchone, J. F.; Dietz, R. S.

    1988-01-01

    Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures).

  9. Shatter cones: Diagnostic impact signatures

    NASA Astrophysics Data System (ADS)

    McHone, J. F.; Dietz, R. S.

    Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures).

  10. Cone rod dystrophies

    PubMed Central

    Hamel, Christian P

    2007-01-01

    Cone rod dystrophies (CRDs) (prevalence 1/40,000) are inherited retinal dystrophies that belong to the group of pigmentary retinopathies. CRDs are characterized by retinal pigment deposits visible on fundus examination, predominantly localized to the macular region. In contrast to typical retinitis pigmentosa (RP), also called the rod cone dystrophies (RCDs) resulting from the primary loss in rod photoreceptors and later followed by the secondary loss in cone photoreceptors, CRDs reflect the opposite sequence of events. CRD is characterized by primary cone involvement, or, sometimes, by concomitant loss of both cones and rods that explains the predominant symptoms of CRDs: decreased visual acuity, color vision defects, photoaversion and decreased sensitivity in the central visual field, later followed by progressive loss in peripheral vision and night blindness. The clinical course of CRDs is generally more severe and rapid than that of RCDs, leading to earlier legal blindness and disability. At end stage, however, CRDs do not differ from RCDs. CRDs are most frequently non syndromic, but they may also be part of several syndromes, such as Bardet Biedl syndrome and Spinocerebellar Ataxia Type 7 (SCA7). Non syndromic CRDs are genetically heterogeneous (ten cloned genes and three loci have been identified so far). The four major causative genes involved in the pathogenesis of CRDs are ABCA4 (which causes Stargardt disease and also 30 to 60% of autosomal recessive CRDs), CRX and GUCY2D (which are responsible for many reported cases of autosomal dominant CRDs), and RPGR (which causes about 2/3 of X-linked RP and also an undetermined percentage of X-linked CRDs). It is likely that highly deleterious mutations in genes that otherwise cause RP or macular dystrophy may also lead to CRDs. The diagnosis of CRDs is based on clinical history, fundus examination and electroretinogram. Molecular diagnosis can be made for some genes, genetic counseling is always advised. Currently

  11. Trichomonas vaginalis: preliminary characterization of a sperm motility inhibiting factor.

    PubMed

    Jarecki-Black, J C; Lushbaugh, W B; Golosov, L; Glassman, A B

    1988-01-01

    This study determined the effects of Trichomonas vaginalis trophozoites, subcellular fractions, and medium from axenic T. vaginalis cultures on human sperm motility and viability. Spent medium (pH 7.0) caused complete cessation of sperm motility after 15 minutes incubation. Trophozoite soluble fraction or formalin-killed trophozoites caused a 50 percent reduction in sperm motility, compared to 25 percent reduction caused by the trophozoite particulate fraction or the sterile medium and three percent by saline (control). Spent medium from T. vaginalis cultures reaching stationary growth phase produced the greatest reduction in sperm motility, suggesting that potency was related to time in culture and trophozoites per ml. The T. vaginalis spermicidal activity was heat-stable, trypsin-sensitive, and had a molecular weight of 12-15,000 by gel filtration. This proteinaceous substance was present in and secreted by T. vaginalis trophozoites during normal growth in axenic culture. Since this T. vaginalis byproduct rapidly killed sperm in vitro, its effects in humans may contribute to infertility in infected couples.

  12. Axoneme Structure from Motile Cilia.

    PubMed

    Ishikawa, Takashi

    2017-01-03

    The axoneme is the main extracellular part of cilia and flagella in eukaryotes. It consists of a microtubule cytoskeleton, which normally comprises nine doublets. In motile cilia, dynein ATPase motor proteins generate sliding motions between adjacent microtubules, which are integrated into a well-orchestrated beating or rotational motion. In primary cilia, there are a number of sensory proteins functioning on membranes surrounding the axoneme. In both cases, as the study of proteomics has elucidated, hundreds of proteins exist in this compartmentalized biomolecular system. In this article, we review the recent progress of structural studies of the axoneme and its components using electron microscopy and X-ray crystallography, mainly focusing on motile cilia. Structural biology presents snapshots (but not live imaging) of dynamic structural change and gives insights into the force generation mechanism of dynein, ciliary bending mechanism, ciliogenesis, and evolution of the axoneme.

  13. Self-organized cell motility

    NASA Astrophysics Data System (ADS)

    Du, Xinxin; Doubrovinski, Konstantin

    2011-03-01

    Cell migration plays a key role in a wide range of biological phenomena, such as morphogenesis, chemotaxis, and wound healing. Cell locomotion relies on the cytoskeleton, a meshwork of filamentous proteins, intrinsically out of thermodynamic equilibrium and cross-linked by molecular motors, proteins that turn chemical energy into mechanical work. In the course of locomotion, cells remain polarized, i.e. they retain a single direction of motion in the absence of external cues. Traditionally, polarization has been attributed to intracellular signaling. However, recent experiments show that polarization may be a consequence of self-organized cytoskeletal dynamics. Our aim is to elucidate the mechanisms by which persistent unidirectional locomotion may arise through simple mechanical interactions of the cytoskeletal proteins. To this end, we develop a simple physical description of cytoskeletal dynamics. We find that the proposed description accounts for a range of phenomena associated with cell motility, including spontaneous polarization, persistent unidirectional motion, and the co-existence of motile and non-motile states.

  14. Bacterial motility: From propulsion to collective behavior

    NASA Astrophysics Data System (ADS)

    Dombrowski, Christopher C.

    This work explores bacterial motility from the mechanisms of propulsion of an individual cell to the complex behavior of collective motility. The shear modulus of bacterial flagella was measured by stretching isolated flagella with an optical trap and by measuring force extension curves of the stretched flagella shedding light onto the mechanics involved in the motility of single micro-organisms. Experiments in concentrated suspensions of bacteria show collective behavior with large scale mixing on a time and length scale greater than can be understood from the standard model of "run and tumble" motility of a single organism are reported. To further understand the transition from individual to collective motility a novel form of motility where an individual bacterium can reverse direction without changing cell orientation is reported here. These experiments further the understanding of bacterial motility.

  15. Fundoplication improves disordered esophageal motility.

    PubMed

    Heider, T Ryan; Behrns, Kevin E; Koruda, Mark J; Shaheen, Nicholas J; Lucktong, Tananchai A; Bradshaw, Barbara; Farrell, Timothy M

    2003-02-01

    Patients with gastroesophageal reflux disease (GERD) and disordered esophageal motility are at risk for postoperative dysphagia, and are often treated with partial (270-degree) fundoplication as a strategy to minimize postoperative swallowing difficulties. Complete (360-degree) fundoplication, however, may provide more effective and durable reflux protection over time. Recently we reported that postfundoplication dysphagia is uncommon, regardless of preoperative manometric status and type of fundoplication. To determine whether esophageal function improves after fundoplication, we measured postoperative motility in patients in whom disordered esophageal motility had been documented before fundoplication. Forty-eight of 262 patients who underwent laparoscopic fundoplication between 1995 and 2000 satisfied preoperative manometric criteria for disordered esophageal motility (distal esophageal peristaltic amplitude < or =30 mm Hg and/or peristaltic frequency < or =80%). Of these, 19 had preoperative manometric assessment at our facility and consented to repeat study. Fifteen (79%) of these patients had a complete fundoplication and four (21%) had a partial fundoplication. Each patient underwent repeat four-channel esophageal manometry 29.5 +/- 18.4 months (mean +/- SD) after fundoplication. Distal esophageal peristaltic amplitude and peristaltic frequency were compared to preoperative data by paired t test. After fundoplication, mean peristaltic amplitude in the distal esophagus increased by 47% (56.8 +/- 30.9 mm Hg to 83.5 +/- 36.5 mm Hg; P < 0.001) and peristaltic frequency improved by 33% (66.4 +/- 28.7% to 87.6 +/- 16.3%; P < 0.01). Normal esophageal motor function was present in 14 patients (74%) after fundoplication, whereas in five patients the esophageal motor function remained abnormal (2 improved, 1 worsened, and 2 remained unchanged). Three patients with preoperative peristaltic frequencies of 0%, 10%, and 20% improved to 84%, 88%, and 50%, respectively

  16. Enhanced light trapping in periodically truncated cone silicon nanowire structure

    NASA Astrophysics Data System (ADS)

    Kai, Qiu; Yuhua, Zuo; Tianwei, Zhou; Zhi, Liu; Jun, Zheng; Chuanbo, Li; Buwen, Cheng

    2015-10-01

    Light trapping plays an important role in improving the conversion efficiency of thin-film solar cells. The good wideband light trapping is achieved using our periodically truncated cone Si nanowire (NW) structures, and their inherent mechanism is analyzed and simulated by FDTD solution software. Ordered cylinder Si NW structure with initial size of 80 nm and length of 200 nm is grown by pattern transfer and selective epitaxial growth. Truncated cone Si NW array is then obtained by thermal oxidation treatment. Its mean reflection in the range of 300-900 nm is lowered to be 5% using 140 nm long truncated cone Si NW structure, compared with that of 20% using cylinder counterparts. It indicates that periodically truncated Si cone structures trap the light efficiently to enhance the light harvesting in a wide spectral range and have the potential application in highly efficient NW solar cells. Project supported by the National Natural Science Foundation of China (Nos. 51072194, 61021003, 61036001, 61376057).

  17. Effects of light environment during growth on the expression of cone opsin genes and behavioral spectral sensitivities in guppies (Poecilia reticulata).

    PubMed

    Sakai, Yusuke; Ohtsuki, Hajime; Kasagi, Satoshi; Kawamura, Shoji; Kawata, Masakado

    2016-05-18

    The visual system is important for animals for mate choice, food acquisition, and predator avoidance. Animals possessing a visual system can sense particular wavelengths of light emanating from objects and their surroundings and perceive their environments by processing information contained in these visual perceptions of light. Visual perception in individuals varies with the absorption spectra of visual pigments and the expression levels of opsin genes, which may be altered according to the light environments. However, which light environments and the mechanism by which they change opsin expression profiles and whether these changes in opsin gene expression can affect light sensitivities are largely unknown. This study determined whether the light environment during growth induced plastic changes in opsin gene expression and behavioral sensitivity to particular wavelengths of light in guppies (Poecilia reticulata). Individuals grown under orange light exhibited a higher expression of long wavelength-sensitive (LWS) opsin genes and a higher sensitivity to 600-nm light than those grown under green light. In addition, we confirmed that variations in the expression levels of LWS opsin genes were related to the behavioral sensitivities to long wavelengths of light. The light environment during the growth stage alters the expression levels of LWS opsin genes and behavioral sensitivities to long wavelengths of light in guppies. The plastically enhanced sensitivity to background light due to changes in opsin gene expression can enhance the detection and visibility of predators and foods, thereby affecting survival. Moreover, changes in sensitivities to orange light may lead to changes in the discrimination of orange/red colors of male guppies and might alter female preferences for male color patterns.

  18. Hydrogen Sulfide and/or Ammonia Reduces Spermatozoa Motility through AMPK/AKT Related Pathways

    NASA Astrophysics Data System (ADS)

    Zhao, Yong; Zhang, Wei-Dong; Liu, Xin-Qi; Zhang, Peng-Fei; Hao, Ya-Nan; Li, Lan; Chen, Liang; Shen, Wei; Tang, Xiang-Fang; Min, Ling-Jiang; Meng, Qing-Shi; Wang, Shu-Kun; Yi, Bao; Zhang, Hong-Fu

    2016-11-01

    A number of emerging studies suggest that air pollutants such as hydrogen sulfide (H2S) and ammonia (NH3) may cause a decline in spermatozoa motility. The impact and underlying mechanisms are currently unknown. Boar spermatozoa (in vitro) and peripubertal male mice (in vivo) were exposed to H2S and/or NH3 to evaluate the impact on spermatozoa motility. Na2S and/or NH4Cl reduced the motility of boar spermatozoa in vitro. Na2S and/or NH4Cl disrupted multiple signaling pathways including decreasing Na+/K+ ATPase activity and protein kinase B (AKT) levels, activating Adenosine 5‧-monophosphate (AMP)-activated protein kinase (AMPK) and phosphatase and tensin homolog deleted on chromosome ten (PTEN), and increasing reactive oxygen species (ROS) to diminish boar spermatozoa motility. The increase in ROS might have activated PTEN, which in turn diminished AKT activation. The ATP deficiency (indicated by reduction in Na+/K+ ATPase activity), transforming growth factor (TGFβ) activated kinase-1 (TAK1) activation, and AKT deactivation stimulated AMPK, which caused a decline in boar spermatozoa motility. Simultaneously, the deactivation of AKT might play some role in the reduction of boar spermatozoa motility. Furthermore, Na2S and/or NH4Cl declined the motility of mouse spermatozoa without affecting mouse body weight gain in vivo. Findings of the present study suggest that H2S and/or NH3 are adversely associated with spermatozoa motility.

  19. Hydrogen Sulfide and/or Ammonia Reduces Spermatozoa Motility through AMPK/AKT Related Pathways

    PubMed Central

    Zhao, Yong; Zhang, Wei-Dong; Liu, Xin-Qi; Zhang, Peng-Fei; Hao, Ya-Nan; Li, Lan; Chen, Liang; Shen, Wei; Tang, Xiang-Fang; Min, Ling-Jiang; Meng, Qing-Shi; Wang, Shu-Kun; Yi, Bao; Zhang, Hong-Fu

    2016-01-01

    A number of emerging studies suggest that air pollutants such as hydrogen sulfide (H2S) and ammonia (NH3) may cause a decline in spermatozoa motility. The impact and underlying mechanisms are currently unknown. Boar spermatozoa (in vitro) and peripubertal male mice (in vivo) were exposed to H2S and/or NH3 to evaluate the impact on spermatozoa motility. Na2S and/or NH4Cl reduced the motility of boar spermatozoa in vitro. Na2S and/or NH4Cl disrupted multiple signaling pathways including decreasing Na+/K+ ATPase activity and protein kinase B (AKT) levels, activating Adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) and phosphatase and tensin homolog deleted on chromosome ten (PTEN), and increasing reactive oxygen species (ROS) to diminish boar spermatozoa motility. The increase in ROS might have activated PTEN, which in turn diminished AKT activation. The ATP deficiency (indicated by reduction in Na+/K+ ATPase activity), transforming growth factor (TGFβ) activated kinase-1 (TAK1) activation, and AKT deactivation stimulated AMPK, which caused a decline in boar spermatozoa motility. Simultaneously, the deactivation of AKT might play some role in the reduction of boar spermatozoa motility. Furthermore, Na2S and/or NH4Cl declined the motility of mouse spermatozoa without affecting mouse body weight gain in vivo. Findings of the present study suggest that H2S and/or NH3 are adversely associated with spermatozoa motility. PMID:27883089

  20. The Holographic Entropy Cone

    SciTech Connect

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.

  1. The Holographic Entropy Cone

    DOE PAGES

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; ...

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phasemore » space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.« less

  2. Making An Impact: Shatter Cones

    ERIC Educational Resources Information Center

    Blank, Lisa M.; Plautz, Michael R.; Crews, Jeffrey W.

    2004-01-01

    In 1990, a group of geologists discovered a large number of shatter cones in southwestern Montana. Shatter cones are a type of metamorphosed rock often found in impact structures (the remains of a crater after a meteor impact and years of Earth activity). Scientists have discovered only 168 impact craters around the world. If rocks could talk,…

  3. Making An Impact: Shatter Cones

    ERIC Educational Resources Information Center

    Blank, Lisa M.; Plautz, Michael R.; Crews, Jeffrey W.

    2004-01-01

    In 1990, a group of geologists discovered a large number of shatter cones in southwestern Montana. Shatter cones are a type of metamorphosed rock often found in impact structures (the remains of a crater after a meteor impact and years of Earth activity). Scientists have discovered only 168 impact craters around the world. If rocks could talk,…

  4. Laser range profile of cones

    NASA Astrophysics Data System (ADS)

    Zhou, Wenzhen; Gong, Yanjun; Wang, Mingjun; Gong, Lei

    2016-10-01

    technology. Laser one-dimensional range profile can reflect the characteristics of the target shape and surface material. These techniques were motivated by applications of laser radar to target discrimination in ballistic missile defense. The radar equation of pulse laser about cone is given in this paper. This paper demonstrates the analytical model of laser one-dimensional range profile of cone based on the radar equation of the pulse laser. Simulations results of laser one-dimensional range profiles of some cones are given. Laser one-dimensional range profiles of cone, whose surface material with diffuse lambertian reflectance, is given in this paper. Laser one-dimensional range profiles of cone, whose surface mater with diffuse materials whose retroreflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. Laser one-dimensional range profiles of different pulse width of cone is given in this paper. The influences of surface material, pulse width, attitude on the one-dimensional range are analyzed. The laser two-dimensional range profile is two-dimensional scattering imaging of pulse laser of target. The two-dimensional range profile of roughness target can provide range resolved information. An analytical model of two-dimensional laser range profile of cone is proposed. The simulations of two-dimensional laser range profiles of some cones are given. Laser two-dimensional range profiles of cone, whose surface mater with diffuse lambertian reflectance, is given in this paper. Laser two-dimensional range profiles of cone, whose surface mater with diffuse materials whose retroreflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. The influence of pulse width, surface material on laser two-dimensional range profile is analyzed. Laser one-dimensional range profile and laser two-dimensional range profile are called as laser

  5. 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.

  6. Deletion of the p85alpha regulatory subunit of phosphoinositide 3-kinase in cone photoreceptor cells results in cone photoreceptor degeneration.

    PubMed

    Ivanovic, Ivana; Anderson, Robert E; Le, Yun Z; Fliesler, Steven J; Sherry, David M; Rajala, Raju V S

    2011-06-01

    Downregulation of the retinal insulin/mTOR pathway in mouse models of retinitis pigmentosa is linked to cone cell death, which can be delayed by systemic administration of insulin. A classic survival kinase linking extracellular trophic/growth factors with intracellular antiapoptotic pathways is phosphoinositide 3-kinase (PI3K), which the authors have shown to protect rod photoreceptors from stress-induced cell death. The role of PI3K in cones was studied by conditional deletion of its p85α regulatory subunit. Mice expressing Cre recombinase in cones were bred to mice with a floxed pi3k gene encoding the p85α regulatory subunit of the PI3K and were back-crossed to ultimately generate offspring with cone-specific p85α knockout (cKO). Cre expression and cone-specific localization were confirmed by Western blot analysis and immunohistochemistry (IHC), respectively. Cone structural integrity was determined by IHC using peanut agglutinin and an M-opsin-specific antibody. Electroretinography (ERG) was used to assess rod and cone photoreceptor function. Retinal structure was examined by light and electron microscopy. An age-related cone degeneration was found in cKO mice, evidenced by a reduction in photopic ERG amplitudes and loss of cone cells. By 12 months of age, approximately 78% of cones had died, and progressive disorganization of synaptic ultrastructure was noted in surviving cone terminals in cKO retinas. Rod viability was unaffected in p85α cKO mice. The present study suggests that PI3K signaling pathway is essential for cone survival in the mouse retina.

  7. Deletion of the p85α Regulatory Subunit of Phosphoinositide 3-Kinase in Cone Photoreceptor Cells Results in Cone Photoreceptor Degeneration

    PubMed Central

    Ivanovic, Ivana; Anderson, Robert E.; Le, Yun Z.; Fliesler, Steven J.; Sherry, David M.

    2011-01-01

    Purpose. Downregulation of the retinal insulin/mTOR pathway in mouse models of retinitis pigmentosa is linked to cone cell death, which can be delayed by systemic administration of insulin. A classic survival kinase linking extracellular trophic/growth factors with intracellular antiapoptotic pathways is phosphoinositide 3-kinase (PI3K), which the authors have shown to protect rod photoreceptors from stress-induced cell death. The role of PI3K in cones was studied by conditional deletion of its p85α regulatory subunit. Methods. Mice expressing Cre recombinase in cones were bred to mice with a floxed pi3k gene encoding the p85α regulatory subunit of the PI3K and were back-crossed to ultimately generate offspring with cone-specific p85α knockout (cKO). Cre expression and cone-specific localization were confirmed by Western blot analysis and immunohistochemistry (IHC), respectively. Cone structural integrity was determined by IHC using peanut agglutinin and an M-opsin–specific antibody. Electroretinography (ERG) was used to assess rod and cone photoreceptor function. Retinal structure was examined by light and electron microscopy. Results. An age-related cone degeneration was found in cKO mice, evidenced by a reduction in photopic ERG amplitudes and loss of cone cells. By 12 months of age, approximately 78% of cones had died, and progressive disorganization of synaptic ultrastructure was noted in surviving cone terminals in cKO retinas. Rod viability was unaffected in p85α cKO mice. Conclusions. The present study suggests that PI3K signaling pathway is essential for cone survival in the mouse retina. PMID:21398281

  8. 21 CFR 876.1725 - Gastrointestinal motility monitoring system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Gastrointestinal motility monitoring system. 876... Gastrointestinal motility monitoring system. (a) Identification. A gastrointestinal motility monitoring system is a... esophageal motility monitor and tube, the gastrointestinal motility (electrical) system, and...

  9. 21 CFR 876.1725 - Gastrointestinal motility monitoring system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Gastrointestinal motility monitoring system. 876... Gastrointestinal motility monitoring system. (a) Identification. A gastrointestinal motility monitoring system is a... esophageal motility monitor and tube, the gastrointestinal motility (electrical) system, and...

  10. 21 CFR 876.1725 - Gastrointestinal motility monitoring system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Gastrointestinal motility monitoring system. 876... Gastrointestinal motility monitoring system. (a) Identification. A gastrointestinal motility monitoring system is a... esophageal motility monitor and tube, the gastrointestinal motility (electrical) system, and...

  11. Ejecta evolution during cone impact

    NASA Astrophysics Data System (ADS)

    Marston, Jeremy; Vakarelski, Ivan; Thoroddsen, Sigurdur

    2013-11-01

    We present results from an experimental study of the impact of conical shaped bodies into a pool of liquid. By varying the cone angle, impact speed and liquid physical properties, we examine a broad parameter space and seek to find conditions when self-similarity can be observed during this phenomena. We use high-speed imaging to capture the early-time motion of the liquid ejecta which emanates from the tip of the cone and travels up along the cone surface. Surprisingly, we find that the detachment of the ejecta can be simply described by air entrainment relationships derived from coating experiments.

  12. Transonic Flow Past Cone Cylinders

    NASA Technical Reports Server (NTRS)

    Solomon, George E

    1955-01-01

    Experimental results are presented for transonic flow post cone-cylinder, axially symmetric bodies. The drag coefficient and surface Mach number are studied as the free-stream Mach number is varied and, wherever possible, the experimental results are compared with theoretical predictions. Interferometric results for several typical flow configurations are shown and an example of shock-free supersonic-to-subsonic compression is experimentally demonstrated. The theoretical problem of transonic flow past finite cones is discussed briefly and an approximate solution of the axially symmetric transonic equations, valid for a semi-infinite cone, is presented.

  13. Cone and Seed Maturation of Southern Pines

    Treesearch

    James P. Barnett

    1976-01-01

    If slightly reduced yields and viability are acceptable, loblolly and slash cone collections can begin 2 to 3 weeks before maturity if the cones are stored before processing. Longleaf(P. palestris Mill.) pine cones should be collected only when mature, as storage decreased germination of seeds from immature cones. Biochemical analyses to determine reducing sugar...

  14. Gaslike model of social motility.

    PubMed

    Parravano, A; Reyes, L M

    2008-08-01

    We propose a model to represent the motility of social elements. The model is completely deterministic, possesses a small number of parameters, and exhibits a series of properties that are reminiscent of the behavior of communities in social-ecological competition; these are (i) similar individuals attract each other; (ii) individuals can form stable groups; (iii) a group of similar individuals breaks into subgroups if it reaches a critical size; (iv) interaction between groups can modify the distribution of the elements as a result of fusion, fission, or pursuit; (v) individuals can change their internal state by interaction with their neighbors. The simplicity of the model and its richness of emergent behaviors, such as, for example, pursuit between groups, make it a useful toy model to explore a diversity of situations by changing the rule by which the internal state of individuals is modified by the interactions with the environment.

  15. Actin-based motility propelled by molecular motors

    NASA Astrophysics Data System (ADS)

    Upadyayula, Sai Pramod; Rangarajan, Murali

    2012-09-01

    Actin-based motility of Listeria monocytogenes propelled by filament end-tracking molecular motors has been simulated. Such systems may act as potential nanoscale actuators and shuttles useful in sorting and sensing biomolecules. Filaments are modeled as three-dimensional elastic springs distributed on one end of the capsule and persistently attached to the motile bacterial surface through an end-tracking motor complex. Filament distribution is random, and monomer concentration decreases linearly as a function of position on the bacterial surface. Filament growth rate increases with monomer concentration but decreases with the extent of compression. The growing filaments exert push-pull forces on the bacterial surface. In addition to forces, torques arise due to two factors—distribution of motors on the bacterial surface, and coupling of torsion upon growth due to the right-handed helicity of F-actin—causing the motile object to undergo simultaneous translation and rotation. The trajectory of the bacterium is simulated by performing a force and torque balance on the bacterium. All simulations use a fixed value of torsion. Simulations show strong alignment of the filaments and the long axis of the bacterium along the direction of motion. In the absence of torsion, the bacterial surface essentially moves along the direction of the long axis. When a small amount of the torsion is applied to the bacterial surface, the bacterium is seen to move in right-handed helical trajectories, consistent with experimental observations.

  16. Vertical microbial community variability of carbonate-based cones may provide insight into ancient conical stromatolite formation

    NASA Astrophysics Data System (ADS)

    Bradley, James; Daille, Leslie; Trivedi, Christopher; Bojanowski, Caitlin; Nunn, Heather; Stamps, Blake; Johnson, Hope; Stevenson, Bradley; Berelson, Will; Corsetti, Frank; Spear, John

    2016-04-01

    Stromatolite morphogenesis is poorly understood, and the process by which microbial mats become mineralized is a primary question in microbialite formation. Ancient conical stromatolites are primarily carbonate-based whereas the few modern analogues in hot springs are either non-mineralized or mineralized by silica. A team from the 2015 International GeoBiology Course investigated carbonate-rich microbial cones from near Little Hot Creek (LHC), Long Valley Caldera, California, to investigate how conical stromatolites might form in a hot spring carbonate system. The cones rise up from a layered microbial mat on the east side of a 45° C pool with very low flow that is super-saturated with respect to CaCO3. Cone structures are 8-30 mm in height, are rigid and do not deform when removed from the pool. Morphological characterization through environmental scanning electronic microscopy revealed that the cone structure is maintained by a matrix of intertwining microbial filaments around carbonate grains. This matrix gives rise to cone-filaments that are arranged vertically or horizontally, and provides further stability to the cone. Preliminary 16S rRNA gene analysis indicated variability of community composition between different vertical levels of the cone. The cone tip had comparatively greater abundance of filamentous cyanobacteria including Leptolingbya, Phormidium and Isosphaera and fewer heterotrophs (e.g. Chloroflexi) compared to the cone bottom. This supports the hypothesis that cone formation may depend on the differential abundance of the microbial community and their potential functional roles. Metagenomic analyses of the cones revealed potential genes related to chemotaxis and motility. Specifically, a genomic bin identified as a member of the genus Isosphaera contained an hmp chemotaxis operon implicated in gliding motility in the cyanobacterium Nostoc punctiforme. Isosphaera is a Planctomycete shown to have phototactic capabilities, and may play a role in

  17. Active gel model of amoeboid cell motility

    NASA Astrophysics Data System (ADS)

    Callan-Jones, A. C.; Voituriez, R.

    2013-02-01

    We develop a model of amoeboid cell motility based on active gel theory. Modeling the motile apparatus of a eukaryotic cell as a confined layer of finite length of poroelastic active gel permeated by a solvent, we first show that, due to active stress and gel turnover, an initially static and homogeneous layer can undergo a contractile-type instability to a polarized moving state in which the rear is enriched in gel polymer. This agrees qualitatively with motile cells containing an actomyosin-rich uropod at their rear. We find that the gel layer settles into a steadily moving, inhomogeneous state at long times, sustained by a balance between contractility and filament turnover. In addition, our model predicts an optimal value of the gel-substrate adhesion leading to maximum layer speed, in agreement with cell motility assays. The model may be relevant to motility of cells translocating in complex, confining environments that can be mimicked experimentally by cell migration through microchannels.

  18. Sperm motility under conditions of weightlessness.

    PubMed

    Engelmann, U; Krassnigg, F; Schill, W B

    1992-01-01

    The aim of this study was to determine the differences in motility of frozen and thawed bull spermatozoa under conditions of weightlessness compared with ground conditions. The tests were performed within a series of scientific and technologic experiments under microgravity using sounding rockets in the Technologische Experimente unter Schwerelosigkeit (TEXUS) program launched in Kiruna, North Sweden. Using a computerized sperm motility analyzer, significant differences were found in sperm motility under microgravity compared with sperm under gravitational conditions on earth. Computer analysis showed alterations in straight line and curvilinear velocity, as well as in linearity values. The amount of progressively motile spermatozoa, including all spermatozoa with a velocity > 20 microns/second, increased significantly from 24% +/- 9.5% in the reference test to 49% +/- 7.6% in the microgravity test. In conclusion, there is strong evidence that gravity influences sperm motility.

  19. Motility of Campylobacter concisus isolated from saliva, feces, and gut mucosal biopsies.

    PubMed

    Ovesen, Sandra; Kirk, Karina Frahm; Nielsen, Hans Linde; Nielsen, Henrik

    2017-03-01

    Campylobacter concisus is an emerging pathogen associated with gastrointestinal disorders such as gastroenteritis and inflammatory bowel diseases (IBD), but the species is also found in healthy subjects. The heterogeneous genome of C. concisus increases the likelihood of varying virulence between strains. Flagella motility is a crucial virulence factor for the well-recognized Campylobacter jejuni; therefore, this study aimed to analyze the motility of C. concisus isolated from saliva, gut biopsies, and feces of patients with IBD, gastroenteritis, and healthy subjects. The motility zones of 63 isolates from 52 patients were measured after microaerobic growth in soft-agar plates for 72 hours. The motility of C. concisus was significantly lower than that of Campylobacter jejuni and Campylobacter fetus subsp. fetus. The motility of C. concisus varied between isolates (4-22 mm), but there was no statistical significant difference between isolates from IBD patients and healthy subjects (p = 0.14). A tendency of a larger motility zones was observed for IBD gut mucosa isolates, although it did not reach statistical significance (p = 0.13), and no difference was found between oral or fecal isolates between groups. In conclusion, the varying motility of C. concisus could not be related to disease outcome or colonization sites. © 2017 APMIS. Published by John Wiley & Sons Ltd.

  20. Bacterial signaling and motility: Sure bets

    SciTech Connect

    Zhulin, Igor B

    2008-01-01

    cytoplasmic membrane. The interaction causes the supramembrane and cytoplasmic rings to rotate along with the flagellar filaments. The energy for flagellar rotation comes from proton motive force or other ions, especially sodium in marine bacteria, which generate an electrochemical gradient across the cell membrane. Three proteins, FliM, FliN, and FliG, located at the base of the motor act as switches that control the direction of flagellar rotation. As exemplified by the enteric bacteria Escherichia coli and Salmonella enterica serovar Typhimurium, changes in the direction of flagellar rotation affect the swimming behavior of the bacterial cell. Counterclockwise (CCW) rotation of the flagella causes the flagellar filaments to form a bundle that pushes the cell forward in a 'run.' In contrast, clockwise (CW) rotation causes the flagellar bundle to fly apart, and the cell tumbles to reorient to a new direction for the ensuing run upon the return of CCW rotation. The interchanging pattern of CCW and CW rotations produces a random walk, composed of relatively long runs with occasional direction changes or turns. By modulating the lengths of the runs or the frequency of tumbling, bacteria can regulate their motile behavior to move in a desirable direction. Many bacteria can also move on surfaces. Except for flagellum-driven swarming motility, all the other forms of known bacterial surface movement involve no flagella. The flagellum-independent surface motility, known as gliding, is observed in cyanobacteria, Mycoplasma species, Cytophaga-Flexibacterium species, and Myxococcus species. Without a doubt, the most thoroughly studied model gliding bacterium is Myxococcus xanthus, which also serves as a prokaryotic model for developmental biology due to its ability to develop multicellular fruiting bodies. M. xanthus cells use gliding motility both to hunt for food during vegetative growth and to aggregate during fruiting body formation. When nutrients are present, groups of cells or

  1. Embryonic markers of cone differentiation

    PubMed Central

    Rodgers, Helen M.; Belcastro, Marycharmain; Sokolov, Maxim

    2016-01-01

    Purpose Photoreceptor cells are born in two distinct phases of vertebrate retinogenesis. In the mouse retina, cones are born primarily during embryogenesis, while rod formation occurs later in embryogenesis and early postnatal ages. Despite this dichotomy in photoreceptor birthdates, the visual pigments and phototransduction machinery are not reactive to visual stimulus in either type of photoreceptor cell until the second postnatal week. Several markers of early cone formation have been identified, including Otx2, Crx, Blimp1, NeuroD, Trβ2, Rorβ, and Rxrγ, and all are thought to be involved in cellular determination. However, little is known about the expression of proteins involved in cone visual transduction during early retinogenesis. Therefore, we sought to characterize visual transduction proteins that are expressed specifically in photoreceptors during mouse embryogenesis. Methods Eye tissue was collected from control and phosducin-null mice at embryonic and early postnatal ages. Immunohistochemistry and quantitative reverse transcriptase-PCR (qPCR) were used to measure the spatial and temporal expression patterns of phosducin (Pdc) and cone transducin γ (Gngt2) proteins and transcripts in the embryonic and early postnatal mouse retina. Results We identified the embryonic expression of phosducin (Pdc) and cone transducin γ (Gngt2) that coincides temporally and spatially with the earliest stages of cone histogenesis. Using immunohistochemistry, the phosducin protein was first detected in the retina at embryonic day (E)12.5, and cone transducin γ was observed at E13.5. The phosducin and cone transducin γ proteins were seen only in the outer neuroblastic layer, consistent with their expression in photoreceptors. At the embryonic ages, phosducin was coexpressed with Rxrγ, a known cone marker, and with Otx2, a marker of photoreceptors. Pdc and Gngt2 mRNAs were detected as early as E10.5 with qPCR, although at low levels. Conclusions Visual transduction

  2. Visual Pigments of Goldfish Cones

    PubMed Central

    Hárosi, Ferenc I.; MacNichol, Edward F.

    1974-01-01

    Freshly isolated retinal photoreceptors of goldfish were studied microspectrophotometrically. Absolute absorptance spectra obtained from dark-adapted cone outer segments reaffirm the existence of three spectrally distinct cone types with absorption maxima at 455 ± 3,530 ± 3, and 625 ± 5 nm. These types were found often recognizable by gross cellular morphology. Side-illuminated cone outer segments were dichroic. The measured dichroic ratio for the main absorption band of each type was 2–3:1. Rapidly bleached cells revealed spectral and dichroic transitions in regions near 400–410, 435–455, and 350–360 nm. These photoproducts decay about fivefold as fast as the intermediates in frog rods. The spectral maxima of photoproducts, combined with other evidence, indicate that retinene2 is the chromophore of all three cone pigments. The average specific optical density for goldfish cone outer segments was found to be 0.0124 ± 0.0015/µm. The spectra of the blue-, and green-absorbing cones appeared to match porphyropsin standards with half-band width Δν = 4,832 ± 100 cm–1. The red-absorbing spectrum was found narrower, having Δν = 3,625 ± 100 cm–1. The results are consistent with the notion that visual pigment concentration within the outer segments is about the same for frog rods and goldfish cones, but that the blue-, and green-absorbing pigments possess molar extinctions of 30,000 liter/mol cm. The red-absorbing pigment was found to have extinction of 40,000 liter/mol cm, assuming invariance of oscillator strength among the three cone spectra. PMID:4817352

  3. A Cone Shaped Hill

    NASA Image and Video Library

    2015-10-14

    There are many hills and knobs on Mars that reveal aspects of the local geologic history. Typically, the hills in the relatively-smooth region surrounding this image are flat topped erosional remnants or mesas with irregular or even polyhedral margins. These landforms suggest wide spread erosion of the soft or weakly-cemented sedimentary layers. This hill stands out because of is circular inverted-cone shape and apparent dark streaks along its flanks visible in lower resolution images. Close inspection from HiRISE reveals that the fine soils sloping down from the peak are intersected with radiating lines of rock and eroding rubble. This formation is similar to lava intrusions that form in the core of a volcano. As lava is squeezed up into a central conduit, radiating fractures fill with lava forming rock units called dikes. As the lava cools inside the ground and in the fractures, it forms into a harder rock that is more resistant to erosion. Later, as the surrounding sediments and soils erode, the resistant volcanic rock remains standing to tell a story of what happened underground long ago. http://photojournal.jpl.nasa.gov/catalog/PIA20003

  4. A two-component regulatory system modulates twitching motility in Dichelobacter nodosus.

    PubMed

    Kennan, Ruth M; Lovitt, Carrie J; Han, Xiaoyan; Parker, Dane; Turnbull, Lynne; Whitchurch, Cynthia B; Rood, Julian I

    2015-08-31

    Dichelobacter nodosus is the essential causative agent of footrot in sheep and type IV fimbriae-mediated twitching motility has been shown to be essential for virulence. We have identified a two-component signal transduction system (TwmSR) that shows similarity to chemosensory systems from other bacteria. Insertional inactivation of the gene encoding the response regulator, TwmR, led to a twitching motility defect, with the mutant having a reduced rate of twitching motility when compared to the wild-type and a mutant complemented with the wild-type twmR gene. The reduced rate of twitching motility was not a consequence of a reduced growth rate or decreased production of surface located fimbriae, but video microscopy indicated that it appeared to result from an overall loss of twitching directionality. These results suggest that a chemotactic response to environmental factors may play an important role in the D. nodosus-mediated disease process.

  5. Effects of pharmacological agents on gastrointestinal motility.

    PubMed

    Gerring, E L

    1989-08-01

    The control mechanisms of gastrointestinal motility are complex. Extrinsic neurohormonal effects modulate an intrinsic system, often called the "gut brain," composed of nervous and neuropeptide components. To exert pharmacologic influence on GI motility, use is made of agents that mimic the external control system. Agents that stimulate opioid receptors, block adrenoceptors, block or facilitate acetylcholine action, or antagonize the action of prostaglandins are used to effect changes in GI motility. The major indications for pharmacologic intervention are to increase motility in constipation, to reduce it in most cases of diarrhea, and to restore propulsive coordination in postoperative ileus. In cases of clinical colic the primary requirement is control of pain. Agents used for this purpose may adversely affect motility, and choice requires knowledge of their actions in this respect. In addition, drugs used for other purposes, anthelmintics for instance, may also influence gut motility. A synopsis of the actions of the agents commonly employed in GI motility control and some associated drugs are displayed in Table 3. Recent advances in the understanding of drug action on the gut should help in the selection of drugs for clinical use.

  6. Modulation of mammalian sperm motility by quercetin.

    PubMed

    Nass-Arden, L; Breitbart, H

    1990-04-01

    The flavonoid quercetin inhibits collective motility of ejaculated ram spermatozoa in the first 2 hr of incubation; during the next 3-4 hr motility is stimulated. To explain this interesting effect, we followed the influence of quercetin on sperm glycolysis, extracellular pH, ATP content, mitochondrial respiration, and lipid peroxidation. The collective motility of untreated cells is decreased to about 40% of the original motility during two hours of incubation. During this time, the rate of glycolysis is constant, respiration rate is increasing, there is no change in ATP content, the rate of lipid peroxidation is very slow, and the extracellular pH became very acidic (pH 5.5). It is concluded that motility is decreased due to this acidification. This acidification is prevented to some extent by quercetin, which indirectly inhibits glycolysis. Quercetin inhibits motility due to the inhibition of the plasma membrane calcium pump, as we showed previously (Breitbart et al., J Biol Chem 260:11548-11553, 1985). The motility of untreated cells is arrested after 3.5 hr of incubation, whereas quercetin-treated cells show high motility, which continues for additional 2-3 hr. After 3.5 hr, the control cells show no glycolytic activity, ATP content and respiration rates are decreased, and rate of lipid peroxidation is highly increased. At this time, quercetin-treated cells show no glycolytic activity, only a small decrease in ATP content and respiratory rate, and a very low rate of lipid peroxidation. Based on these data it is concluded that sperm motility after 3.5 hr of incubation is dependent mainly on mitochondrial respiration.(ABSTRACT TRUNCATED AT 250 WORDS)

  7. Computer-assisted quantification of motile and invasive capabilities of cancer cells

    PubMed Central

    Kumar, Karthiga Santhana; Pillong, Max; Kunze, Jens; Burghardt, Isabel; Weller, Michael; Grotzer, Michael A.; Schneider, Gisbert; Baumgartner, Martin

    2015-01-01

    High-throughput analysis of cancer cell dissemination and its control by extrinsic and intrinsic cellular factors is hampered by the lack of adequate and efficient analytical tools for quantifying cell motility. Oncology research would greatly benefit from such a methodology that allows to rapidly determine the motile behaviour of cancer cells under different environmental conditions, including inside three-dimensional matrices. We combined automated microscopy imaging of two- and three-dimensional cell cultures with computational image analysis into a single assay platform for studying cell dissemination in high-throughput. We have validated this new approach for medulloblastoma, a metastatic paediatric brain tumour, in combination with the activation of growth factor signalling pathways with established pro-migratory functions. The platform enabled the detection of primary tumour and patient-derived xenograft cell sensitivity to growth factor-dependent motility and dissemination and identified tumour subgroup-specific responses to selected growth factors of excellent diagnostic value. PMID:26486848

  8. Motility-Induced Phase Separation

    NASA Astrophysics Data System (ADS)

    Cates, Michael E.; Tailleur, Julien

    2015-03-01

    Self-propelled particles include both self-phoretic synthetic colloids and various microorganisms. By continually consuming energy, they bypass the laws of equilibrium thermodynamics. These laws enforce the Boltzmann distribution in thermal equilibrium: The steady state is then independent of kinetic parameters. In contrast, self-propelled particles tend to accumulate where they move more slowly. They may also slow down at high density for either biochemical or steric reasons. This creates positive feedback, which can lead to motility-induced phase separation (MIPS) between dense and dilute fluid phases. At leading order in gradients, a mapping relates variable-speed, self-propelled particles to passive particles with attractions. This deep link to equilibrium phase separation is confirmed by simulations but generally breaks down at higher order in gradients: New effects, with no equilibrium counterpart, then emerge. We give a selective overview of the fast-developing field of MIPS, focusing on theory and simulation but including a brief speculative survey of its experimental implications.

  9. Methanogens, Methane and Gastrointestinal Motility

    PubMed Central

    Triantafyllou, Konstantinos; Chang, Christopher

    2014-01-01

    Anaerobic fermentation of the undigested polysaccharide fraction of carbohydrates produces hydrogen in the intestine which is the substrate for methane production by intestinal methanogens. Hydrogen and methane are excreted in the flatus and in breath giving the opportunity to indirectly measure their production using breath testing. Although methane is detected in 30%-50% of the healthy adult population worldwide, its production has been epidemiologically and clinically associated with constipation related diseases, like constipation predominant irritable bowel syndrome and chronic constipation. While a causative relation is not proven yet, there is strong evidence from animal studies that methane delays intestinal transit, possibly acting as a neuromuscular transmitter. This evidence is further supported by the universal finding that methane production (measured by breath test) is associated with delayed transit time in clinical studies. There is also preliminary evidence that antibiotic reduction of methanogens (as evidenced by reduced methane production) predicts the clinical response in terms of symptomatic improvement in patients with constipation predominant irritable bowel syndrome. However, we have not identified yet the mechanism of action of methane on intestinal motility, and since methane production does not account for all constipation associated cases, there is need for high quality clinical trials to examine methane as a biomarker for the diagnosis or as a biomarker that predicts antibiotic treatment response in patients with constipation related disorders. PMID:24466443

  10. Regulation of Eukaryotic Flagellar Motility

    NASA Astrophysics Data System (ADS)

    Mitchell, David R.

    2005-03-01

    The central apparatus is essential for normal eukaryotic flagellar bend propagation as evidenced by the paralysis associated with mutations that prevent central pair (CP) assembly. Interactions between doublet-associated radial spokes and CP projections are thought to modulate spoke-regulated protein kinases and phosphatases on outer doublets, and these enzymes in turn modulate dynein activity. To better understand CP control mechanisms, we determined the three-dimensional structure of the Chlamydomonas reinhardtii CP complex and analyzed CP orientation during formation and propagation of flagellar bending waves. We show that a single CP microtubule, C1, is near the outermost doublet in curved regions of the flagellum, and this orientation is maintained by twists between successive principal and reverse bends. The Chlamydomonas CP is inherently twisted; twists are not induced by bend formation, and do not depend on forces or signals transmitted through spoke-central pair interactions. We hypothesize that CP orientation passively responds to bend formation, and that bend propagation drives rotation of the CP and maintains a constant CP orientation in bends, which in turn permits signal transduction between specific CP projections and specific doublet-associated dyneins through radial spokes. The central pair kinesin, Klp1, although essential for normal motility, is therefore not the motor that drives CP rotation. The CP also acts as a scaffold for enzymes that maintain normal intraflagellar ATP concentration.

  11. Deterministic patterns in cell motility

    NASA Astrophysics Data System (ADS)

    Lavi, Ido; Piel, Matthieu; Lennon-Duménil, Ana-Maria; Voituriez, Raphaël; Gov, Nir S.

    2016-12-01

    Cell migration paths are generally described as random walks, associated with both intrinsic and extrinsic noise. However, complex cell locomotion is not merely related to such fluctuations, but is often determined by the underlying machinery. Cell motility is driven mechanically by actin and myosin, two molecular components that generate contractile forces. Other cell functions make use of the same components and, therefore, will compete with the migratory apparatus. Here, we propose a physical model of such a competitive system, namely dendritic cells whose antigen capture function and migratory ability are coupled by myosin II. The model predicts that this coupling gives rise to a dynamic instability, whereby cells switch from persistent migration to unidirectional self-oscillation, through a Hopf bifurcation. Cells can then switch to periodic polarity reversals through a homoclinic bifurcation. These predicted dynamic regimes are characterized by robust features that we identify through in vitro trajectories of dendritic cells over long timescales and distances. We expect that competition for limited resources in other migrating cell types can lead to similar deterministic migration modes.

  12. Shatter cones at sierra madera, Texas.

    PubMed

    Howard, K A; Offield, T W

    1968-10-11

    Shatter cones abound in the central uplift of Sierra Madera and they occur as far as 6.5 kilometers from the center. Apical angles average near 90 degrees. Whole cones and full cones represented by diversely oriented cone segments in any structural block show relatively uniform orientations of axes and a dominant direction of point. The cones predate faulting and folding in the central uplift, and, when beds are restored to horizontal, most cones point inward and upward, a pattern that supports the hypothesis of an impact origin.

  13. Mammalian Sperm Motility: Observation and Theory

    NASA Astrophysics Data System (ADS)

    Gaffney, E. A.; Gadêlha, H.; Smith, D. J.; Blake, J. R.; Kirkman-Brown, J. C.

    2011-01-01

    Mammalian spermatozoa motility is a subject of growing importance because of rising human infertility and the possibility of improving animal breeding. We highlight opportunities for fluid and continuum dynamics to provide novel insights concerning the mechanics of these specialized cells, especially during their remarkable journey to the egg. The biological structure of the motile sperm appendage, the flagellum, is described and placed in the context of the mechanics underlying the migration of mammalian sperm through the numerous environments of the female reproductive tract. This process demands certain specific changes to flagellar movement and motility for which further mechanical insight would be valuable, although this requires improved modeling capabilities, particularly to increase our understanding of sperm progression in vivo. We summarize current theoretical studies, highlighting the synergistic combination of imaging and theory in exploring sperm motility, and discuss the challenges for future observational and theoretical studies in understanding the underlying mechanics.

  14. The influence of prostaglandins on sperm motility.

    PubMed

    Schlegel, W; Rotermund, S; Färber, G; Nieschlag, E

    1981-01-01

    Prostaglandin E2 and F2 alpha were measured in ejaculates from 10 fertile and 55 infertile men. Prostaglandin F2 alpha was negatively correlated with motility (r = 0.77; p less than 0.01) in normal men. In patients with disturbed fertility, prostaglandin F2 alpha was always higher than in the controls, while prostaglandin E2 was elevated only in patients with persisting varicocele and in those with very low sperm counts and severely impaired motility. There was neither de novo synthesis of prostaglandins in spermatozoa nor were binding sites for prostaglandin E2 and F2 alpha detectable. Inactivation of seminal prostaglandins by incubation with prostaglandin 15-hydroxydehydrogenase resulted in a dramatic fall in motility. The results suggest that prostaglandin F2 alpha act on motility, but the action is not mediated by receptors.

  15. Motility in the epsilon-proteobacteria.

    PubMed

    Beeby, Morgan

    2015-12-01

    The epsilon-proteobacteria are a widespread group of flagellated bacteria frequently associated with either animal digestive tracts or hydrothermal vents, with well-studied examples in the human pathogens of Helicobacter and Campylobacter genera. Flagellated motility is important to both pathogens and hydrothermal vent members, and a number of curious differences between the epsilon-proteobacterial and enteric bacterial motility paradigms make them worthy of further study. The epsilon-proteobacteria have evolved to swim at high speed and through viscous media that immobilize enterics, a phenotype that may be accounted for by the molecular architecture of the unusually large epsilon-proteobacterial flagellar motor. This review summarizes what is known about epsilon-proteobacterial motility and focuses on a number of recent discoveries that rationalize the differences with enteric flagellar motility. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Toll-like receptor 2 (TLR2), transforming growth factor-β, hyaluronan (HA), and receptor for HA-mediated motility (RHAMM) are required for surfactant protein A-stimulated macrophage chemotaxis.

    PubMed

    Foley, Joseph P; Lam, David; Jiang, Hongmei; Liao, Jie; Cheong, Naeun; McDevitt, Theresa M; Zaman, Aisha; Wright, Jo Rae; Savani, Rashmin C

    2012-10-26

    The innate immune system protects the host from bacterial and viral invasion. Surfactant protein A (SPA), a lung-specific collectin, stimulates macrophage chemotaxis. However, the mechanisms regulating this function are unknown. Hyaluronan (HA) and its receptors RHAMM (receptor for HA-mediated motility, CD168) and CD44 also regulate cell migration and inflammation. We therefore examined the role of HA, RHAMM, and CD44 in SPA-stimulated macrophage chemotaxis. Using antibody blockade and murine macrophages, SPA-stimulated macrophage chemotaxis was dependent on TLR2 but not the other SPA receptors examined. Anti-TLR2 blocked SPA-induced production of TGFβ. In turn, TGFβ1-stimulated chemotaxis was inhibited by HA-binding peptide and anti-RHAMM antibody but not anti-TLR2 antibody. Macrophages from TLR2(-/-) mice failed to migrate in response to SPA but responded normally to TGFβ1 and HA, effects that were blocked by anti-RHAMM antibody. Macrophages from WT and CD44(-/-) mice had similar responses to SPA, whereas those from RHAMM(-/-) mice had decreased chemotaxis to SPA, TGFβ1, and HA. In primary macrophages, SPA-stimulated TGFβ production was dependent on TLR2, JNK, and ERK but not p38. Pam3Cys, a specific TLR2 agonist, stimulated phosphorylation of JNK, ERK, and p38, but only JNK and ERK inhibition blocked Pam3Cys-stimulated chemotaxis. We have uncovered a novel pathway for SPA-stimulated macrophage chemotaxis where SPA stimulation via TLR2 drives JNK- and ERK-dependent TGFβ production. TGFβ1, in turn, stimulates macrophage chemotaxis in a RHAMM and HA-dependent manner. These findings are highly relevant to the regulation of innate immune responses by SPA with key roles for specific components of the extracellular matrix.

  17. Toll-like Receptor 2 (TLR2), Transforming Growth Factor-β, Hyaluronan (HA), and Receptor for HA-mediated Motility (RHAMM) Are Required for Surfactant Protein A-stimulated Macrophage Chemotaxis*

    PubMed Central

    Foley, Joseph P.; Lam, David; Jiang, Hongmei; Liao, Jie; Cheong, Naeun; McDevitt, Theresa M.; Zaman, Aisha; Wright, Jo Rae; Savani, Rashmin C.

    2012-01-01

    The innate immune system protects the host from bacterial and viral invasion. Surfactant protein A (SPA), a lung-specific collectin, stimulates macrophage chemotaxis. However, the mechanisms regulating this function are unknown. Hyaluronan (HA) and its receptors RHAMM (receptor for HA- mediated motility, CD168) and CD44 also regulate cell migration and inflammation. We therefore examined the role of HA, RHAMM, and CD44 in SPA-stimulated macrophage chemotaxis. Using antibody blockade and murine macrophages, SPA-stimulated macrophage chemotaxis was dependent on TLR2 but not the other SPA receptors examined. Anti-TLR2 blocked SPA-induced production of TGFβ. In turn, TGFβ1-stimulated chemotaxis was inhibited by HA-binding peptide and anti-RHAMM antibody but not anti-TLR2 antibody. Macrophages from TLR2−/− mice failed to migrate in response to SPA but responded normally to TGFβ1 and HA, effects that were blocked by anti-RHAMM antibody. Macrophages from WT and CD44−/− mice had similar responses to SPA, whereas those from RHAMM−/− mice had decreased chemotaxis to SPA, TGFβ1, and HA. In primary macrophages, SPA-stimulated TGFβ production was dependent on TLR2, JNK, and ERK but not p38. Pam3Cys, a specific TLR2 agonist, stimulated phosphorylation of JNK, ERK, and p38, but only JNK and ERK inhibition blocked Pam3Cys-stimulated chemotaxis. We have uncovered a novel pathway for SPA-stimulated macrophage chemotaxis where SPA stimulation via TLR2 drives JNK- and ERK-dependent TGFβ production. TGFβ1, in turn, stimulates macrophage chemotaxis in a RHAMM and HA-dependent manner. These findings are highly relevant to the regulation of innate immune responses by SPA with key roles for specific components of the extracellular matrix. PMID:22948158

  18. Select Acetophenones Modulate Flagellar Motility in Chlamydomonas

    PubMed Central

    Evans, Shakila K.; Pearce, Austin A.; Ibezim, Prudence K.; Primm, Todd P.; Gaillard, Anne R.

    2009-01-01

    Acetophenones were screened for activity against positive phototaxis of Chlamydomonas cells, a process that requires coordinated flagellar motility. The structure-activity relationships of a series of acetophenones are reported, including acetophenones that affect flagellar motility and cell viability. Notably, 4-methoxyacetophenone, 3,4-dimethoxyacetophenone, and 4-hydroxyacetophenone induced negative phototaxis in Chlamydomonas, suggesting interference with activity of flagellar proteins and control of flagellar dominance. PMID:20659114

  19. ATPases, ion exchangers and human sperm motility.

    PubMed

    Peralta-Arias, Rubén D; Vívenes, Carmen Y; Camejo, María I; Piñero, Sandy; Proverbio, Teresa; Martínez, Elizabeth; Marín, Reinaldo; Proverbio, Fulgencio

    2015-05-01

    Human sperm has several mechanisms to control its ionic milieu, such as the Na,K-ATPase (NKA), the Ca-ATPase of the plasma membrane (PMCA), the Na(+)/Ca(2) (+)-exchanger (NCX) and the Na(+)/H(+)-exchanger (NHE). On the other hand, the dynein-ATPase is the intracellular motor for sperm motility. In this work, we evaluated NKA, PMCA, NHE, NCX and dynein-ATPase activities in human sperm and investigated their correlation with sperm motility. Sperm motility was measured by Computer Assisted Semen Analysis. It was found that the NKA activity is inhibited by ouabain with two Ki (7.9 × 10(-9) and 9.8 × 10(-5) M), which is consistent with the presence of two isoforms of α subunit of the NKA in the sperm plasma membranes (α1 and α4), being α4 more sensitive to ouabain. The decrease in NKA activity is associated with a reduction in sperm motility. In addition, sperm motility was evaluated in the presence of known inhibitors of NHE, PMCA and NCX, such as amiloride, eosin, and KB-R7943, respectively, as well as in the presence of nigericin after incubation with ouabain. Amiloride, eosin and KB-R7943 significantly reduced sperm motility. Nigericin reversed the effect of ouabain and amiloride on sperm motility. Dynein-ATPase activity was inhibited by acidic pH and micromolar concentrations of Ca(2) (+). We explain our results in terms of inhibition of the dynein-ATPase in the presence of higher cytosolic H(+) and Ca(2) (+), and therefore inhibition of sperm motility. © 2015 Society for Reproduction and Fertility.

  20. Key stages in mammary gland development: the mammary end bud as a motile organ.

    PubMed

    Hinck, Lindsay; Silberstein, Gary B

    2005-01-01

    In the rodent, epithelial end buds define the tips of elongating mammary ducts. These highly motile structures undergo repeated dichotomous branching as they aggressively advance through fatty stroma and, turning to avoid other ducts, they finally cease growth leaving behind the open, tree-like framework on which secretory alveoli develop during pregnancy. This review identifies the motility of end buds as a unique developmental marker that represents the successful integration of systemic and local mammotrophic influences, and covers relevant advances in ductal growth regulation, extracellular matrix (ECM) remodeling, and cell adhesion in the inner end bud. An unexpected growth-promoting synergy between insulin-like growth factor-1 and progesterone, in which ducts elongate without forming new end buds, is described as well as evidence strongly supporting self-inhibition of ductal elongation by end-bud-secreted transforming growth factor-beta acting on stromal targets. The influence of the matrix metalloproteinase ECM-remodeling enzymes, notably matrix metalloproteinase-2, on end bud growth is discussed in the broader context of enzymes that regulate the polysaccharide-rich glycosaminoglycan elements of the ECM. Finally, a critical, motility-enabling role for the cellular architecture of the end bud is identified and the contribution of cadherins, the netrin/neogenin system, and ErbB2 to the structure and motility of end buds is discussed.

  1. Flagellar motility in eukaryotic human parasites.

    PubMed

    Krüger, Timothy; Engstler, Markus

    2015-10-01

    A huge variety of protists rely on one or more motile flagella to either move themselves or move fluids and substances around them. Many of these flagellates have evolved a symbiotic or parasitic lifestyle. Several of the parasites have adapted to human hosts, and include agents of prevalent and serious diseases. These unicellular parasites have become specialised in colonising a wide range of biological niches within humans. They usually have diverse transmission cycles, and frequently manifest a variety of distinct morphological stages. The motility of the single or multiple flagella plays important but understudied roles in parasite transmission, host invasion, dispersal, survival, proliferation and pathology. In this review we provide an overview of the important human pathogens that possess a motile flagellum for at least part of their life cycle. We highlight recently published studies that aim to elucidate motility mechanisms, and their relevance for human disease. We then bring the physics of swimming at the microscale into context, emphasising the importance of interdisciplinary approaches for a full understanding of flagellate motility - especially in light of the parasites' microenvironments and population dynamics. Finally, we summarise some important technological aspects, describing challenges for the field and possibilities for motility analyses in the future.

  2. Toward the reconstitution of synthetic cell motility

    PubMed Central

    Siton-Mendelson, Orit; Bernheim-Groswasser, Anne

    2016-01-01

    ABSTRACT Cellular motility is a fundamental process essential for embryonic development, wound healing, immune responses, and tissues development. Cells are mostly moving by crawling on external, or inside, substrates which can differ in their surface composition, geometry, and dimensionality. Cells can adopt different migration phenotypes, e.g., bleb-based and protrusion-based, depending on myosin contractility, surface adhesion, and cell confinement. In the few past decades, research on cell motility has focused on uncovering the major molecular players and their order of events. Despite major progresses, our ability to infer on the collective behavior from the molecular properties remains a major challenge, especially because cell migration integrates numerous chemical and mechanical processes that are coupled via feedbacks that span over large range of time and length scales. For this reason, reconstituted model systems were developed. These systems allow for full control of the molecular constituents and various system parameters, thereby providing insight into their individual roles and functions. In this review we describe the various reconstituted model systems that were developed in the past decades. Because of the multiple steps involved in cell motility and the complexity of the overall process, most of the model systems focus on very specific aspects of the individual steps of cell motility. Here we describe the main advancement in cell motility reconstitution and discuss the main challenges toward the realization of a synthetic motile cell. PMID:27019160

  3. Toward the reconstitution of synthetic cell motility.

    PubMed

    Siton-Mendelson, Orit; Bernheim-Groswasser, Anne

    2016-09-02

    Cellular motility is a fundamental process essential for embryonic development, wound healing, immune responses, and tissues development. Cells are mostly moving by crawling on external, or inside, substrates which can differ in their surface composition, geometry, and dimensionality. Cells can adopt different migration phenotypes, e.g., bleb-based and protrusion-based, depending on myosin contractility, surface adhesion, and cell confinement. In the few past decades, research on cell motility has focused on uncovering the major molecular players and their order of events. Despite major progresses, our ability to infer on the collective behavior from the molecular properties remains a major challenge, especially because cell migration integrates numerous chemical and mechanical processes that are coupled via feedbacks that span over large range of time and length scales. For this reason, reconstituted model systems were developed. These systems allow for full control of the molecular constituents and various system parameters, thereby providing insight into their individual roles and functions. In this review we describe the various reconstituted model systems that were developed in the past decades. Because of the multiple steps involved in cell motility and the complexity of the overall process, most of the model systems focus on very specific aspects of the individual steps of cell motility. Here we describe the main advancement in cell motility reconstitution and discuss the main challenges toward the realization of a synthetic motile cell.

  4. Characterizing motility dynamics in human RPE cells

    NASA Astrophysics Data System (ADS)

    Liu, Zhuolin; Kurokawa, Kazuhiro; Zhang, Furu; Miller, Donald T.

    2017-02-01

    Retinal pigment epithelium (RPE) cells are vital to health of the outer retina, however, are often compromised in ageing and ocular diseases that lead to blindness. Early manifestation of RPE disruption occurs at the cellular level, but while in vivo biomarkers at this scale hold considerable promise, RPE cells have proven extremely challenging to image in the living human eye. Recently we addressed this problem by using organelle motility as a novel contrast agent to enhance the RPE cell in conjunction with 3D resolution of adaptive optics-optical coherence tomography (AO-OCT) to section the RPE layer. In this study, we expand on the central novelty of our method - organelle motility - by characterizing the dynamics of the motility in individual RPE cells, important because of its direct link to RPE physiology. To do this, AO-OCT videos of the same retinal patch were acquired at approximately 1 min intervals or less, time stamped, and registered in 3D with sub-cellular accuracy. Motility was quantified by an exponential decay time constant, the time for motility to decorrelate the speckle field across an RPE cell. In two normal subjects, we found the decay time constant to be just 3 seconds, thus indicating rapid motility in normal RPE cells.

  5. Shatter cones: (Mis)understood?

    PubMed Central

    Osinski, Gordon R.; Ferrière, Ludovic

    2016-01-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and “double” cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship Dsc = 0.4 Da, where Dsc is the maximum spatial extent of in situ shatter cones, and Da is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact. PMID:27532050

  6. Shatter cones: (Mis)understood?

    PubMed

    Osinski, Gordon R; Ferrière, Ludovic

    2016-08-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and "double" cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship D sc = 0.4 D a, where D sc is the maximum spatial extent of in situ shatter cones, and D a is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact.

  7. Vertical Microbial Community Variability of Carbonate-based Cones may Provide Insight into Formation in the Rock Record

    NASA Astrophysics Data System (ADS)

    Trivedi, C.; Bojanowski, C.; Daille, L. K.; Bradley, J.; Johnson, H.; Stamps, B. W.; Stevenson, B. S.; Berelson, W.; Corsetti, F. A.; Spear, J. R.

    2015-12-01

    Stromatolite morphogenesis is poorly understood, and the process by which microbial mats become mineralized is a primary question in microbialite formation. Ancient conical stromatolites are primarily carbonate-based whereas the few modern analogues in hot springs are either non-mineralized or mineralized by silica. A team from the 2015 International GeoBiology Course investigated carbonate-rich microbial cones from near Little Hot Creek (LHC), Long Valley Caldera, California, to investigate how conical stromatolites might form in a hot spring carbonate system. The cones are up to 3 cm tall and are found in a calm, ~45° C pool near LHC that is 4 times super-saturated with respect to CaCO3. The cones rise from a flat, layered microbial mat at the edge of the pool. Scanning electron microscopy revealed filamentous bacteria associated with calcite crystals within the cone tips. Preliminary 16S rRNA gene analysis indicated variability of community composition between different vertical levels of the cone. The cone tip had comparatively greater abundance of filamentous cyanobacteria (Leptolyngbya and Phormidium) and fewer heterotrophs (e.g. Chloroflexi) compared to the cone bottom. This supports the hypothesis that cone formation may depend on the differential abundance of the microbial community and their potential functional roles. Metagenomic analyses of the cones revealed potential genes related to chemotaxis and motility. Specifically, a genomic bin identified as a member of the genus Isosphaera contained an hmp chemotaxis operon implicated in gliding motility in the cyanobacterium Nostoc punctiforme [1]. Isosphaera is a Planctomycete shown to have phototactic capabilities [2], and may play a role in conjunction with cyanobacteria in the vertical formation of the cones. This analysis of actively growing cones indicates a complex interplay of geochemistry and microbiology that form structures which can serve as models for processes that occurred in the past and are

  8. The swarming motility of Pseudomonas aeruginosa is blocked by cranberry proanthocyanidins and other tannin-containing materials.

    PubMed

    O'May, Che; Tufenkji, Nathalie

    2011-05-01

    Bacterial motility plays a key role in the colonization of surfaces by bacteria and the subsequent formation of resistant communities of bacteria called biofilms. Derivatives of cranberry fruit, predominantly condensed tannins called proanthocyanidins (PACs) have been reported to interfere with bacterial adhesion, but the effects of PACs and other tannins on bacterial motilities remain largely unknown. In this study, we investigated whether cranberry PAC (CPAC) and the hydrolyzable tannin in pomegranate (PG; punicalagin) affected the levels of motilities exhibited by the bacterium Pseudomonas aeruginosa. This bacterium utilizes flagellum-mediated swimming motility to approach a surface, attaches, and then further spreads via the surface-associated motilities designated swarming and twitching, mediated by multiple flagella and type IV pili, respectively. Under the conditions tested, both CPAC and PG completely blocked swarming motility but did not block swimming or twitching motilities. Other cranberry-containing materials and extracts of green tea (also rich in tannins) were also able to block or impair swarming motility. Moreover, swarming bacteria were repelled by filter paper discs impregnated with many tannin-containing materials. Growth experiments demonstrated that the majority of these compounds did not impair bacterial growth. When CPAC- or PG-containing medium was supplemented with surfactant (rhamnolipid), swarming motility was partially restored, suggesting that the effective tannins are in part acting by a rhamnolipid-related mechanism. Further support for this theory was provided by demonstrating that the agar surrounding tannin-induced nonswarming bacteria was considerably less hydrophilic than the agar area surrounding swarming bacteria. This is the first study to show that natural compounds containing tannins are able to block P. aeruginosa swarming motility and that swarming bacteria are repelled by such compounds.

  9. Two Shatter-Coned NWA Meteorites

    NASA Astrophysics Data System (ADS)

    McHone, J. F.; Shoemaker, C.; Killgore, M.; Killgore, K.

    2012-03-01

    Shatter cones are found in target rocks at more than 70 terrestrial impact sites and are regarded as reliable field criteria for meteoroid impact events. Shatter cones are now seen in chondritic meteorites and indicate early collision events.

  10. Cone Penetrometer N Factor Determination Testing Results

    SciTech Connect

    Follett, Jordan R.

    2014-03-05

    This document contains the results of testing activities to determine the empirical 'N Factor' for the cone penetrometer in kaolin clay simulant. The N Factor is used to releate resistance measurements taken with the cone penetrometer to shear strength.

  11. Novel ultrastructures of Treponema primitia and their implications for motility

    PubMed Central

    Murphy, Gavin E.; Matson, Eric G.; Leadbetter, Jared R.; Berg, Howard C.; Jensen, Grant J.

    2011-01-01

    Summary Members of the bacterial phylum Spirochaetes are generally helical cells propelled by periplasmic flagella. The spirochete Treponema primitia is interesting because of its mutualistic role in the termite gut, where it is believed to cooperate with protozoa that break down cellulose and produce H2 as a by-product. Here we report the ultrastructure of T. primitia as obtained by electron cryotomography of intact, frozen-hydrated cells. Several previously unrecognized external structures were revealed, including bowl-like objects decorating the outer membrane, arcades of hook-shaped proteins winding along the exterior and tufts of fibrils extending from the cell tips. Inside the periplasm, cone-like structures were found at each pole. Instead of the single peptidoglycan layer typical of other Gram-negative bacteria, two distinct periplasmic layers were observed. These layers formed a central open space that contained two flagella situated adjacent to each other. In some areas, the inner membrane formed flattened invaginations that protruded into the cytoplasm. High-speed light microscopic images of swimming T. primitia cells showed that cell bodies remained rigid and moved in a helical rather than planar motion. Together, these findings support the ‘rolling cylinder’ model for T. primitia motility that posits rotation of the protoplasmic cylinder within the outer sheath. PMID:18248579

  12. Cross-Phosphorylation and Interaction between Src/FAK and MAPKAP5/PRAK in Early Focal Adhesions Controls Cell Motility

    PubMed Central

    Dwyer, Sheila Figel; Gelman, Irwin H

    2015-01-01

    P38-regulated and activated kinase (PRAK/MAPKAPK5) is a serine/threonine kinase which lies downstream of the p38 and ERK3/4 MAP kinase pathways. PRAK plays diverse roles in the processes of cell growth, nutrient starvation response, programmed cell death, senescence and motility. PRAK has been shown to both promote and inhibit cell motility in different contexts. The pro-motility functions of PRAK are attributed mainly to cytoskeletal rearrangement occurring downstream of its phosphorylated substrate HSP27; however, it was recently shown that PRAK is required for motility in endothelial cells upstream of Focal adhesion kinase (FAK). Along with Src, FAK functions as a mediator of motility signaling through the phosphorylation of substrates in focal adhesions. Here, we show that PRAK, initially identified as a FAK substrate in an in situ/ kinase overlay assay, is a Src substrate, the phosphorylation of which directs PRAK to focal adhesions. Focal adhesion localization of PRAK was not found to affect cell motility, however transient over expression of PRAK inhibited motility in HeLa cells. This effect requires PRAK kinase activity and proceeds through an impairment of FAK activation via phosphorylation on Y861. Our studies demonstrate for the first time that PRAK is regulated by tyrosine phosphorylation, localizes to focal adhesions, and interacts physically with and can phosphorylate FAK/Src. Further we provide a novel mechanism for the inhibition of motility downstream of PRAK. PMID:26042227

  13. Small Molecules in the Cone Snail Arsenal.

    PubMed

    Neves, Jorge L B; Lin, Zhenjian; Imperial, Julita S; Antunes, Agostinho; Vasconcelos, Vitor; Olivera, Baldomero M; Schmidt, Eric W

    2015-10-16

    Cone snails are renowned for producing peptide-based venom, containing conopeptides and conotoxins, to capture their prey. A novel small-molecule guanine derivative with unprecedented features, genuanine, was isolated from the venom of two cone snail species. Genuanine causes paralysis in mice, indicating that small molecules and not just polypeptides may contribute to the activity of cone snail venom.

  14. Cone positioning device for oral radiation therapy.

    PubMed

    Mahanna, G K; Ivanhoe, J R; Attanasio, R A

    1994-06-01

    This article describes the fabrication and modification of a peroral cone-positioning device. The modification provides added cone stability and prevents tongue intrusion into the radiation field. This device provides a repeatable accurate cone/lesion relationship and the fabrication technique is simplified, accurate, and minimizes patient discomfort.

  15. Statistical physical models of cellular motility

    NASA Astrophysics Data System (ADS)

    Banigan, Edward J.

    Cellular motility is required for a wide range of biological behaviors and functions, and the topic poses a number of interesting physical questions. In this work, we construct and analyze models of various aspects of cellular motility using tools and ideas from statistical physics. We begin with a Brownian dynamics model for actin-polymerization-driven motility, which is responsible for cell crawling and "rocketing" motility of pathogens. Within this model, we explore the robustness of self-diffusiophoresis, which is a general mechanism of motility. Using this mechanism, an object such as a cell catalyzes a reaction that generates a steady-state concentration gradient that propels the object in a particular direction. We then apply these ideas to a model for depolymerization-driven motility during bacterial chromosome segregation. We find that depolymerization and protein-protein binding interactions alone are sufficient to robustly pull a chromosome, even against large loads. Next, we investigate how forces and kinetics interact during eukaryotic mitosis with a many-microtubule model. Microtubules exert forces on chromosomes, but since individual microtubules grow and shrink in a force-dependent way, these forces lead to bistable collective microtubule dynamics, which provides a mechanism for chromosome oscillations and microtubule-based tension sensing. Finally, we explore kinematic aspects of cell motility in the context of the immune system. We develop quantitative methods for analyzing cell migration statistics collected during imaging experiments. We find that during chronic infection in the brain, T cells run and pause stochastically, following the statistics of a generalized Levy walk. These statistics may contribute to immune function by mimicking an evolutionarily conserved efficient search strategy. Additionally, we find that naive T cells migrating in lymph nodes also obey non-Gaussian statistics. Altogether, our work demonstrates how physical

  16. Cone selectivity derived from the responses of the retinal cone mosaic to natural scenes.

    PubMed

    Wachtler, Thomas; Doi, Eizaburo; Lee, Te- Won; Sejnowski, Terrence J

    2007-06-18

    To achieve color vision, the brain has to process signals of the cones in the retinal photoreceptor mosaic in a cone-type-specific way. We investigated the possibility that cone-type-specific wiring is an adaptation to the statistics of the cone signals. We analyzed estimates of cone responses to natural scenes and found that there is sufficient information in the higher order statistics of L- and M-cone responses to distinguish between cones of different types, enabling unsupervised learning of cone-type specificity. This was not the case for a fourth cone type with spectral sensitivity between L and M cones, suggesting an explanation for the lack of strong tetrachromacy in heterozygous carriers of color deficiencies.

  17. Cone selectivity derived from the responses of the retinal cone mosaic to natural scenes

    PubMed Central

    Doi, Eizaburo; Lee, Te-Won; Sejnowski, Terrence J.

    2010-01-01

    To achieve color vision, the brain has to process signals of the cones in the retinal photoreceptor mosaic in a cone-type-specific way. We investigated the possibility that cone-type-specific wiring is an adaptation to the statistics of the cone signals. We analyzed estimates of cone responses to natural scenes and found that there is sufficient information in the higher order statistics of L- and M-cone responses to distinguish between cones of different types, enabling unsupervised learning of cone-type specificity. This was not the case for a fourth cone type with spectral sensitivity between L and M cones, suggesting an explanation for the lack of strong tetrachromacy in heterozygous carriers of color deficiencies. PMID:17685813

  18. DOS cones along atomic chains

    NASA Astrophysics Data System (ADS)

    Kwapiński, Tomasz

    2017-03-01

    The electron transport properties of a linear atomic chain are studied theoretically within the tight-binding Hamiltonian and the Green’s function method. Variations of the local density of states (DOS) along the chain are investigated. They are crucial in scanning tunnelling experiments and give important insight into the electron transport mechanism and charge distribution inside chains. It is found that depending on the chain parity the local DOS at the Fermi level can form cone-like structures (DOS cones) along the chain. The general condition for the local DOS oscillations is obtained and the linear behaviour of the local density function is confirmed analytically. DOS cones are characterized by a linear decay towards the chain which is in contrast to the propagation properties of charge density waves, end states and Friedel oscillations in one-dimensional systems. We find that DOS cones can appear due to non-resonant electron transport, the spin–orbit scattering or for chains fabricated on a substrate with localized electrons. It is also shown that for imperfect chains (e.g. with a reduced coupling strength between two neighboring sites) a diamond-like structure of the local DOS along the chain appears.

  19. Cellular Motility--Experiments on Contractile and Motile Mechanisms in the Slime Mould, Physarum Polycephalum

    ERIC Educational Resources Information Center

    Holmes, R. P.; Stewart, P. R.

    1977-01-01

    Actin and myosin have now been demonstrated to be important constituents of many eukaryotic cells. Their role is primarily that of a contractile system underlying all aspects of cellular motility. Described here is a simple experimental system to demonstrate quantitatively aspects of motility and its regulation in a slime mold. (Author/MA)

  20. Cellular Motility--Experiments on Contractile and Motile Mechanisms in the Slime Mould, Physarum Polycephalum

    ERIC Educational Resources Information Center

    Holmes, R. P.; Stewart, P. R.

    1977-01-01

    Actin and myosin have now been demonstrated to be important constituents of many eukaryotic cells. Their role is primarily that of a contractile system underlying all aspects of cellular motility. Described here is a simple experimental system to demonstrate quantitatively aspects of motility and its regulation in a slime mold. (Author/MA)

  1. Fourier analysis of cell motility: correlation of motility with metastatic potential.

    PubMed Central

    Partin, A W; Schoeniger, J S; Mohler, J L; Coffey, D S

    1989-01-01

    We report the development of a computerized, mathematical system for quantitating the various types of cell motility. This Fourier analysis method simultaneously quantifies for individual cells (i) temporal changes in cell shape represented by cell ruffling, undulation, and pseudopodal extension, (ii) cell translation, and (iii) average cell size and shape. This spatial-temporal Fourier analysis was tested on a series of well-characterized animal tumor cell lines of rat prostatic cancer to study in a quantitative manner the correlation of cell motility with increasing in vivo metastatic potential. Fourier motility coefficients measuring pseudopodal extension correlated best with metastatic potential in the cell lines studied. This study demonstrated that Fourier analysis provides quantitative measurement of cell motility that may be applied to the study of biological processes. This analysis should aid in the study of the motility of individual cells in various areas of cellular and tumor biology. Images PMID:2919174

  2. Using experimental evolution to explore natural patterns between bacterial motility and resistance to bacteriophages.

    PubMed

    Koskella, Britt; Taylor, Tiffany B; Bates, Jennifer; Buckling, Angus

    2011-11-01

    Resistance of bacteria to phages may be gained by alteration of surface proteins to which phages bind, a mechanism that is likely to be costly as these molecules typically have critical functions such as movement or nutrient uptake. To address this potential trade-off, we combine a systematic study of natural bacteria and phage populations with an experimental evolution approach. We compare motility, growth rate and susceptibility to local phages for 80 bacteria isolated from horse chestnut leaves and, contrary to expectation, find no negative association between resistance to phages and bacterial motility or growth rate. However, because correlational patterns (and their absence) are open to numerous interpretations, we test for any causal association between resistance to phages and bacterial motility using experimental evolution of a subset of bacteria in both the presence and absence of naturally associated phages. Again, we find no clear link between the acquisition of resistance and bacterial motility, suggesting that for these natural bacterial populations, phage-mediated selection is unlikely to shape bacterial motility, a key fitness trait for many bacteria in the phyllosphere. The agreement between the observed natural pattern and the experimental evolution results presented here demonstrates the power of this combined approach for testing evolutionary trade-offs.

  3. Motility modes of the parasite Trypanosoma brucei

    NASA Astrophysics Data System (ADS)

    Temel, Fatma Zeynep; Qu, Zijie; McAllaster, Michael; de Graffenried, Christopher; Breuer, Kenneth

    2015-11-01

    The parasitic single-celled protozoan Trypanosoma brucei causes African Sleeping Sickness, which is a fatal disease in humans and animals that threatens more than 60 million people in 36 African countries. Cell motility plays a critical role in the developmental phases and dissemination of the parasite. Unlike many other motile cells such as bacteria Escherichia coli or Caulobacter crescentus, the flagellum of T. brucei is attached along the length of its awl-like body, producing a unique mode of motility that is not fully understood or characterized. Here, we report on the motility of T. brucei, which swims using its single flagellum employing both rotating and undulating propulsion modes. We tracked cells in real-time in three dimensions using fluorescent microscopy. Data obtained from experiments using both short-term tracking within the field of view and long-term tracking using a tracking microscope were analyzed. Motility modes and swimming speed were analyzed as functions of cell size, rotation rate and undulation pattern. Research supported by NSF.

  4. Gliding motility and polarized slime secretion.

    PubMed

    Yu, Rosa; Kaiser, Dale

    2007-01-01

    Myxococcus leaves a trail of slime on agar as it moves. A filament of slime can be seen attached to the end of a cell, but it is seen only at one end at any particular moment. To identify genes essential for A motility, transposon insertion mutations with defective A motility were studied. Fifteen of the 33 mutants had totally lost A motility. All these mutant cells had filaments of slime emerging from both ends, indicating that bipolar secretion prevents A motility. The remaining 18 A motility mutants, also produced by gene knockout, secreted slime only from one pole, but they swarmed at a lower rate than A(+) and are called 'partial' gliding mutants, or pgl. For each pgl mutant, the reduction in swarm expansion rate was directly proportional to the reduction in the coefficient of elasticotaxis. The pgl mutants have a normal reversal frequency and normal gliding speed when they move. But their probability of movement per unit time is lower than pgl(+) cells. Many of the pgl mutants are produced by transposon insertions in glycosyltransferase genes. It is proposed that these glycosyltransferases carry out the synthesis of a repeat unit polysaccharide that constitutes the slime.

  5. Competency Based Medical Education in Gastrointestinal Motility

    PubMed Central

    Yadlapati, Rena; Keswani, Rajesh N.; Pandolfino, John E.

    2016-01-01

    Traditional apprenticeship based medical education methods focusing on subjective evaluations and case-volume requirements do not reliably produce clinicians that provide high-quality care in unsupervised practice. Consequently, training approaches are shifting towards competency based medical education, which incorporates robust assessment methods and credible standards of physician proficiency. However, current gastroenterology and hepatology training in the US continues to utilize procedural volume and global impressions without standardized criteria as markers of competence. In particular, efforts to optimize competency based training in gastrointestinal (GI) motility are not underway, even though GI motility disorders account for nearly half of outpatient gastroenterology visits. These deficiencies compromise the quality of patient care. Thus, there is a great need and opportunity to shift our focus in GI motility training towards a competency based approach. First, we need to understand rates of learning for individual diagnostic tests. Next, integrated systems that standardize training and monitor physician competency for GI motility diagnostics are required. In addition, certification processes to credential competent physicians need to be developed. These advances are critical to optimizing the quality of GI motility diagnostics in practice. PMID:27061311

  6. Study of human sperm motility post cryopreservation

    PubMed Central

    Oberoi, Bhavni; Kumar, Sushil; Talwar, Pankaj

    2014-01-01

    Background Cryopreservation of spermatozoa is a widely used technique to preserve the fertility of males. It can also benefit the armed forces personnel who are to be sent for long recruitments, while leaving their families behind. This study, apart from studying the effects of freezing and thawing, reveals the effect of the post thaw interval on the motility of the human spermatozoa and thus widens the insemination window period. Methods A detailed semen analysis was carried out as per the WHO guidelines for 25 samples. The samples were then washed, analysed and frozen in liquid nitrogen. The semen samples were subsequently thawed and similarly analysed after 20 min and 40 min of thawing. This was then followed by statistical analysis of the comparative motilities. Results Motility of sperms is found to decrease after cryopreservation. However, the study revealed that after thawing a significant increase in the motility of the sperms was noted with the progression of time (p < 0.05). Conclusion By simulating conditions similar to the in vivo conditions for the post thaw semen samples, we can safely wait, confirm the parameters like motility and count, and then inseminate the samples instead of blindly inseminating them immediately after thawing. PMID:25382909

  7. Nitric oxide inhibition of human sperm motility.

    PubMed

    Weinberg, J B; Doty, E; Bonaventura, J; Haney, A F

    1995-08-01

    To determine the effect of nitric oxide (NO) on sperm motility in vitro. Normal human sperm separated by centrifugation through a discontinuous Percoll gradient and subsequent swim-up were incubated for up to 24 hours with NO donors, with and without the known NO quencher hemoglobin, as well as with agents that raise intracellular cyclic 3',5'-guanosine monophosphate (cGMP). Sperm respiration was determined by a tetrazolium-formazan spectrophotometric assay. Andrology laboratory. Absolute sperm motility and respiration. Sperm incubated with the NO donors 1 mM nitroprusside, 100 to 125 microM 3-morpholinosydnonimine, and 25 to 125 microM pure nitric oxide gas dissolved in buffer were inhibited in motility in a dose-dependent fashion. The inhibition could be reversed by the NO quencher hemoglobin. Agents that raise cellular cGMP (dibutyryl cGMP or 8-bromo-cGMP) did not inhibit motility. Nitric oxide inhibited sperm respiration, as measured by the tetrazolium-formazan assay. Nitric oxide reduces sperm motility, possibly by a mechanism involving inhibition of cellular respiration independent of an elevation of intracellular cGMP. Nitric oxide elaborated in the female or male genital tract in vivo could adversely influence sperm function and fertility.

  8. Effectiveness of different chemical agents for disinfection of gutta-percha cones.

    PubMed

    Nabeshima, Cleber K; Machado, Manoel Eduardo de Lima; Britto, Maria Leticia Borges; Pallotta, Raul Capp

    2011-12-01

    This aim of this study was to evaluate and compare the efficacy of different chemical methods to disinfect gutta-percha cones (GP). Eighty-six size 80 GP cones were used. The cones were contaminated by immersion in saliva and Enterococcus faecalis. Four chemical agents were used: 1% sodium hypochlorite (G1), 2% chlorhexidine gluconate (G2), 10% povidone iodine (G3) and 0.9% saline solution (G4). GP cones were immersed in the solutions for periods of 1 and 10 min. After the disinfection procedure, the cones were incubated in blood heart infusion and the presence of bacterial growth was analysed by turbidity of the medium. In G4, bacterial growth was observed in all specimens; G3 showed growth after immersion for 1 min when contaminated with E. faecalis; G1 showed diverse results after the immersion for 1 min. Meanwhile, G1 and G3 after 10 min, and G2 at both times evaluated did not show bacterial growth. The immersion of GP cones in 2% chlorhexidine gluconate for 1 min was an effective method for GP disinfection, while 10% povidone iodine and 1% sodium hypochlorite needed 10 min of immersion to disinfect the GP.

  9. Directional imaging of the retinal cone mosaic.

    PubMed

    Vohnsen, Brian; Iglesias, Ignacio; Artal, Pablo

    2004-05-01

    We describe a near-IR scanning laser ophthalmoscope that allows the retinal cone mosaic to be imaged in the human eye in vivo without the use of wave-front correction techniques. The method takes advantage of the highly directional quality of cone photoreceptors that permits efficient coupling of light to individual cones and subsequent detection of most directional components of the backscattered light produced by the light-guiding effect of the cones. We discuss details of the system and describe cone-mosaic images obtained under different conditions.

  10. Light-sensitive motile iridophores and visual pigments in the neon tetra, Paracheirodon innesi.

    PubMed

    Kasai, Akiko; Oshima, Noriko

    2006-09-01

    Although motile iridophores in the longitudinal stripes of neon tetra skin are under control of the sympathetic nervous system, they also respond to light directly and show circadian color changes. Using neon tetra skin, we found that the photoresponse of iridophores depends on light intensity, and that light near 500 nm is most effective. RT-PCR demonstrated the expression of mRNAs encoding rhodopsin and two kinds of cone opsins (Pi-green1 and Pi-green2) in neon tetra skin where the light-sensitive iridophores exist. These mRNAs are also expressed in the lateral eyes. The cone opsin genes, Pi-green1 and Pi-green2, show high similarity with the g101 and g103 genes of unique green cone opsins (belonging to the MWS/LWS group) of the blind Mexican cavefish. These results show that Pi-green1, Pi-green2, and/or rhodopsin may play important roles in the photoresponse of neon tetra iridophores, which are most sensitive to light near 500 nm.

  11. Symmetry breaking in actin gels - Implications for cellular motility

    NASA Astrophysics Data System (ADS)

    John, Karin; Peyla, Philippe; Misbah, Chaouqi

    2007-03-01

    The physical origin of cell motility is not fully understood. Recently minimal model systems have shown, that polymerizing actin itself can produce a motile force, without the help of motor proteins. Pathogens like Shigella or Listeria use actin to propel themselves forward in their host cell. The same process can be mimicked with polystyrene beads covered with the activating protein ActA, which reside in a solution containing actin monomers. ActA induces the growth of an actin gel at the bead surface. Initially the gel grows symmetrically around the bead until a critical size is reached. Subsequently one observes a symmetry breaking and the gel starts to grow asymmetrically around the bead developing a tail of actin at one side. This symmetry breaking is accompanied by a directed movement of the bead, with the actin tail trailing behind the bead. Force generation relies on the combination of two properties: growth and elasticity of the actin gel. We study this phenomenon theoretically within the framework of a linear elasticity theory and linear flux-force relationships for the evolution of an elastic gel around a hard sphere. Conditions for a parity symmetry breaking are identified analytically and illustrated numerically with the help of a phasefield model.

  12. Journey of water in pine cones

    NASA Astrophysics Data System (ADS)

    Song, Kahye; Yeom, Eunseop; Seo, Seung-Jun; Kim, Kiwoong; Kim, Hyejeong; Lim, Jae-Hong; Joon Lee, Sang

    2015-05-01

    Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system.

  13. Journey of water in pine cones

    PubMed Central

    Song, Kahye; Yeom, Eunseop; Seo, Seung-Jun; Kim, Kiwoong; Kim, Hyejeong; Lim, Jae-Hong; Joon Lee, Sang

    2015-01-01

    Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system. PMID:25944117

  14. Modeling of chromosome motility during mitosis.

    PubMed

    Gardner, Melissa K; Odde, David J

    2006-12-01

    Chromosome motility is a highly regulated and complex process that ultimately achieves proper segregation of the replicated genome. Recent modeling studies provide a computational framework for investigating how microtubule assembly dynamics, motor protein activity and mitotic spindle mechanical properties are integrated to drive chromosome motility. Among other things, these studies show that metaphase chromosome oscillations can be explained by a range of assumptions, and that non-oscillatory states can be achieved with modest changes to the model parameters. In addition, recent microscopy studies provide new insight into the nature of the coupling between force on the kinetochore and kinetochore-microtubule assembly/disassembly. Together, these studies facilitate advancement toward a unified model that quantitatively predicts chromosome motility.

  15. Shock detachment process on cones in hypervelocity flows

    NASA Astrophysics Data System (ADS)

    Leyva, Ivett Alejandra

    1999-11-01

    The shock detachment process on cones in hypervelocity flows is one of the most sensitive flows to relaxation effects. The critical angle for shock detachment under frozen conditions can be very different from the critical angle under chemical and thermal equilibrium. The rate of increase of the detachment distance with cone angle is also affected by the relaxation rate. The purpose of this study is to explain the effects of nonequilibrium on the shock detachment distance and its growth rate on cones in hypervelocity flows. The study consists of an experimental and a computational program. The experimental part has been carried out at Caltech's hypervelocity reflected shock tunnel. Six free-stream conditions were chosen, using both N2 and CO2 as test gases. The experimental data obtained are holographic interferograms, surface temperature, and pressure measurements. The code employed for the numerical simulations is a Navier-Stokes solver that can account for thermal and chemical nonequilibrium in axisymmetric flows. The data obtained for the shock detachment distance confirms a previous theoretical model that predicts the detachment distance will grow more slowly for relaxing flows than for frozen or equilibrium flows. This difference is due to the behavior of the sonic line inside the shock layer. Different growth rates result when the detachment distance is controlled by the diameter of the cone (frozen and equilibrium cases) than when it is controlled by the relaxation length (nonequilibrium flows). The behavior of the detachment distance from the frozen to equilibrium limits for a given cone half-angle and free-stream condition has also been studied. It was confirmed that the ratio of the detachment distance to the cone diameter is constant in the two extremes and rapidly switches from one value to the other for cone diameters of about 2 cm to 16 cm. The experimental interferograms are also compared with numerical ones in terms of the detachment distance, the

  16. Response of a Motile/Non-Motile Escherichia coli Front to Hydrodynamic excitations

    NASA Astrophysics Data System (ADS)

    Baabour, Magali; Douarche, Carine; Salin, Dominique

    2014-11-01

    In a recent study (Douarche et al. PRL 102, 198101 (2009)), it has been shown that the motility of Escherichia coli (E. coli) is highly correlated to the oxygen level in a minimal medium: bacteria swim as long as they are provided with oxygen but reversibly transit to a non-motile state when they lack of it. Hence, when oxygen diffuses into an anaerobic sample of non-motile bacteria, a propagating front delineates a region of motile bacteria where oxygen is present from a region of non-motile ones where the oxygen is still not present. To study the response of this front to hydrodynamics excitation, we use the same fluorescent E. coli bacterial solution in rectangular cross section glass cells open to air (oxygen) at one inlet. After bacteria have consumed the oxygen of the solution, the presence of the oxygen only at the open edge of the sample leads to the formation of an analogous stationary front between motile and non-motile bacteria. We follow the response of this front to hydrodynamics flows such as an oscillating Poiseuille flow or natural convection. We analyze both the macroscopic behavior (shape and width) of the front as well as the microscopic displacements of individual bacteria. The dispersive behavior of this bacterial front is compared to the one of equivalent. Collaboration between Laboratories FAST and LPS, Univ Paris Sud and CNRS.

  17. Deployable micro-traps to sequester motile bacteria

    NASA Astrophysics Data System (ADS)

    di Giacomo, Raffaele; Krödel, Sebastian; Maresca, Bruno; Benzoni, Patrizia; Rusconi, Roberto; Stocker, Roman; Daraio, Chiara

    2017-04-01

    The development of strategies to reduce the load of unwanted bacteria is a fundamental challenge in industrial processing, environmental sciences and medical applications. Here, we report a new method to sequester motile bacteria from a liquid, based on passive, deployable micro-traps that confine bacteria using micro-funnels that open into trapping chambers. Even in low concentrations, micro-traps afford a 70% reduction in the amount of bacteria in a liquid sample, with a potential to reach >90% as shown by modelling improved geometries. This work introduces a new approach to contain the growth of bacteria without chemical means, an advantage of particular importance given the alarming growth of pan-drug-resistant bacteria.

  18. Deployable micro-traps to sequester motile bacteria

    PubMed Central

    Di Giacomo, Raffaele; Krödel, Sebastian; Maresca, Bruno; Benzoni, Patrizia; Rusconi, Roberto; Stocker, Roman; Daraio, Chiara

    2017-01-01

    The development of strategies to reduce the load of unwanted bacteria is a fundamental challenge in industrial processing, environmental sciences and medical applications. Here, we report a new method to sequester motile bacteria from a liquid, based on passive, deployable micro-traps that confine bacteria using micro-funnels that open into trapping chambers. Even in low concentrations, micro-traps afford a 70% reduction in the amount of bacteria in a liquid sample, with a potential to reach >90% as shown by modelling improved geometries. This work introduces a new approach to contain the growth of bacteria without chemical means, an advantage of particular importance given the alarming growth of pan-drug-resistant bacteria. PMID:28378786

  19. Deployable micro-traps to sequester motile bacteria.

    PubMed

    Di Giacomo, Raffaele; Krödel, Sebastian; Maresca, Bruno; Benzoni, Patrizia; Rusconi, Roberto; Stocker, Roman; Daraio, Chiara

    2017-04-05

    The development of strategies to reduce the load of unwanted bacteria is a fundamental challenge in industrial processing, environmental sciences and medical applications. Here, we report a new method to sequester motile bacteria from a liquid, based on passive, deployable micro-traps that confine bacteria using micro-funnels that open into trapping chambers. Even in low concentrations, micro-traps afford a 70% reduction in the amount of bacteria in a liquid sample, with a potential to reach >90% as shown by modelling improved geometries. This work introduces a new approach to contain the growth of bacteria without chemical means, an advantage of particular importance given the alarming growth of pan-drug-resistant bacteria.

  20. Inside the cone of protection

    SciTech Connect

    Stahmann, J.R.

    1983-01-01

    Although lightning cones of protection and cones of attraction have been used for over 100 years, much confusion still remains as to their effectiveness, particularly as applied to personnel protection. At Kennedy Space Center, a 1:1 cone of protection with a straight side is standard for structure or equipment protection. However, at the launch pad, where a 400-foot lightning lightning rod on top of an insulating mast is used for pad lightning protection, the idea developed that personnel within a 400-foot radius of this mast would be safe from lightning and those outside it would not. Since it is obvious that a person 395 feet (120.4 m.) from the mast is only slightly safer than one at 405 feet (123.5 m.), an investigation was initiated to calculate the probabilities of a person being struck by lightning as he moves closer to the mast inside the cone of protection. Since the risk does not go to zero outside the structure, the risk level can then be estimated. To arrive at the expected strike frequency, it was necessary to measure the strike frequencies at KSC. Krider and others have found a mean area density of cloud-to-ground lightning at KSC of about 4.6 + or - 3.1 flashes per sq km per month in the summer. An overall frequency is estimated as about 20 flashes per sq km per year. With these data, the risk of exposure at various distances from the lightning mast can be calculated. Assuming continuous exposure during thunderstorms, this risk varies from about one strike per person in 1,400 years near the tower to one stroke per person in 300 years at about 400 foot (122 m.).

  1. Cardiac cone-beam CT

    SciTech Connect

    Manzke, Robert . E-mail: robert.manzke@philips.com

    2005-10-15

    This doctoral thesis addresses imaging of the heart with retrospectively gated helical cone-beam computed tomography (CT). A thorough review of the CT reconstruction literature is presented in combination with a historic overview of cardiac CT imaging and a brief introduction to other cardiac imaging modalities. The thesis includes a comprehensive chapter about the theory of CT reconstruction, familiarizing the reader with the problem of cone-beam reconstruction. The anatomic and dynamic properties of the heart are outlined and techniques to derive the gating information are reviewed. With the extended cardiac reconstruction (ECR) framework, a new approach is presented for the heart-rate-adaptive gated helical cardiac cone-beam CT reconstruction. Reconstruction assessment criteria such as the temporal resolution, the homogeneity in terms of the cardiac phase, and the smoothness at cycle-to-cycle transitions are developed. Several reconstruction optimization approaches are described: An approach for the heart-rate-adaptive optimization of the temporal resolution is presented. Streak artifacts at cycle-to-cycle transitions can be minimized by using an improved cardiac weighting scheme. The optimal quiescent cardiac phase for the reconstruction can be determined automatically with the motion map technique. Results for all optimization procedures applied to ECR are presented and discussed based on patient and phantom data. The ECR algorithm is analyzed for larger detector arrays of future cone-beam systems throughout an extensive simulation study based on a four-dimensional cardiac CT phantom. The results of the scientific work are summarized and an outlook proposing future directions is given. The presented thesis is available for public download at www.cardiac-ct.net.

  2. Missile and Spacecraft Coning Instabilities

    DTIC Science & Technology

    2007-11-02

    181-192. "Mingori, D. L., and Yam, T., " Nutational Stability of a Spinning Space- craft with Internal Mass Motion and Axial Thrust," AIAA Paper 86...Nomenclature 1 Introduction 1 Equations of Motion 2 Yaw Moment Damping or Undamping 2 Spacecraft Precession Damper 3 Vehicle Coning with Axial ...with Axial Thrust and Variable Mass The variable mass accompanying thrust from a spin-stabilized rocket motor or PAM produces a destabilizing effect

  3. Loss cone-driven cyclotron maser instability

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Yun; Yi, Sibaek; Lim, Dayeh; Kim, Hee-Eun; Seough, Jungjoon; Yoon, Peter H.

    2013-11-01

    The weakly (or mildly) relativistic cyclotron maser instability has been successfully applied to explain the Earth's auroral kilometric radiation and other radio sources in nature and laboratory. Among the most important physical parameters that determine the instability criteria is the ratio of plasma-to-electron cyclotron frequencies, ωp/Ω. It is therefore instructive to consider how the normalized maximum growth rate, γmax/Ω, varies as a function of ωp/Ω. Although many authors have already discussed this problem, in order to complete the analysis, one must also understand how the radiation emission angle corresponding to the maximum growth, θmax, scales with ωp/Ω, since the propagation angle determines the radiation beaming pattern. Also, the behavior of the frequency corresponding to the maximum growth rate at each harmonic, (ωmax-sΩ)/Ω, where s=1,2,3,ċ , as a function of ωp/Ωis of importance for a complete understanding of the maser excitation. The present paper computes these additional quantities for the first time, making use of a model loss cone electron distribution function.

  4. Bursting the Taylor cone bubble

    NASA Astrophysics Data System (ADS)

    Pan, Zhao; Truscott, Tadd

    2014-11-01

    A soap bubble fixed on a surface and placed in an electric field will take on the shape of a cone rather than constant curvature (dome) when the electrical field is not present. The phenomenon was introduced by J. Zeleny (1917) and studied extensively by C.T. Wilson & G.I. Taylor (1925). We revisit the Taylor cone problem by studying the deformation and bursting of soap bubbles in a point charge electric field. A single bubble takes on the shape of a cone in the electric field and a high-speed camera equipped with a micro-lens is used to observe the unsteady dynamics at the tip. Rupture occurs as a very small piece of the tip is torn away from the bubble toward the point charge. Based on experiments, a theoretical model is developed that predicts when rupture should occur. This study may help in the design of foam-removal techniques in engineering and provide a better understanding of an electrified air-liquid interface.

  5. Motility is critical for effective distribution and accumulation of bacteria in tumor tissue.

    PubMed

    Toley, Bhushan J; Forbes, Neil S

    2012-02-01

    Motile bacteria can overcome the penetration limitations of cancer chemotherapeutics because they can actively migrate into solid tumors. Although several genera of bacteria have been shown to accumulate preferentially in tumors, the spatiotemporal dynamics of bacterial tumor colonization and their dependence on bacterial motility are not clear. For effective tumor regression, bacteria must penetrate and distribute uniformly throughout tumors. To measure these dynamics, we used an in vitro model of continuously perfused tumor tissue to mimic the delivery and systemic clearance of Salmonella typhimurium strains SL1344 and VNP20009, and Escherichia coli strains K12 and DH5α. Tissues were treated for 1 hour with 10(5) or 10(7) CFU ml(-1) suspensions of each strain and the location and extent of bacterial accumulation were observed for 30 hours. Salmonella had 14.5 times greater average swimming speed than E. coli and colonized tissues at 100 times lower doses than E. coli. Bacterial motility strongly correlated (R(2) = 99.3%) with the extent of tissue accumulation. When inoculated at 10(5) CFU ml(-1), motile Salmonella formed colonies denser than 10(10) CFU/(g-tissue) and less motile E. coli showed no detectable colonization. Based on spatiotemporal profiles and a mathematical model of motility and growth, bacterial dispersion was found to be necessary for deep penetration into tissue. Bacterial colonization caused apoptosis in tumors and apoptosis levels correlated (R(2) = 98.6%) with colonization density. These results show that motility is critical for effective distribution of bacteria in tumors and is essential for designing cancer therapies that can overcome the barrier of limited tumor penetration. This journal is © The Royal Society of Chemistry 2012

  6. Hydrodynamic effects on microcapillary motility and chemotaxis assays of Methylosinus trichosporium OB3b.

    PubMed Central

    Shonnard, D R; Taylor, R T; Tompson, A; Knapp, R B

    1992-01-01

    A study of the random motility and chemotaxis of Methylosinus trichosporium OB3b was conducted by using Palleroni-chamber microcapillary assay procedures. Under the growth conditions employed, this methanotroph was observed qualitatively with a microscope to be either slightly motile or essentially nonmotile. However, the cells did not not respond in the microcapillary assays in the manner expected for nonmotile Brownian particles. As a consequence, several hydrodynamic effects on these Palleroni microcapillary assays were uncovered. In the random-motility microcapillary assay, nondiffusive cell accumulations occurred that were strongly dependent upon cell concentration. An apparent minimal random-motility coefficient (mu) for this bacterial cell of 1.0 x 10(-7) cm2/s was estimated from microcapillary assays. A simple alternative spectrophotometric assay, based upon gravitational settling, was developed and shown to be an improvement over the Palleroni microcapillary motility assay for M. trichosporium OB3b in that it yielded a more-accurate threefold-lower random-motility coefficient. In addition, it provided a calculation of the gravitational-settling velocity. In the chemotaxis microcapillary assay, the apparent chemotactic responses were strongest for the highest test-chemical concentrations in the microcapillaries, were correlated with microcapillary fluid density, and were strongly dependent upon the microcapillary volume. A simple method to establish the maximal concentration of a chemical that can be tested and to quantify any contributions of abiotic convection is described. Investigators should be aware of the potential problems due to density-driven convection when using these commonly employed microcapillary assays for studying cells which have low motilities. PMID:1444383

  7. Computer aided boar semen motility analysis for cereulide detection in different food matrices.

    PubMed

    Rajkovic, Andreja; Uyttendaele, Mieke; Debevere, Johan

    2007-02-28

    Computer Aided Semen Analysis (CASA) study of the boar semen motility has been demonstrated to be an appropriate assay for detection of cereulide (Bacillus cereus emetic toxin). Application of the boar semen bio-assay to detect cereulide directly in foods requires investigation of potential interference of food components, preservatives and other microbial and chemical food contaminants with the bio-assay. Current study provides evidence that none of included Staphylococcus aureus enterotoxins A, B, C and D nor B. cereus Hemolysin BL (HBL) and non-hemolytic enterotoxin (NHE) and three mycotoxins (Sterigmatocystin, Fumonisin B1 and Patulin) exhibited a toxic impact on semen progressive motility. Aflatoxin M1, M3 and zearalenone impaired semen motility only at concentrations (0.004 mg ml(-1), 0.1 mg ml(-1) and 10 mg ml(-1), respectively) much higher than those found in foods and those permitted by legislation, in comparison to cereulide which induces motility cease at concentrations lower than 20 ng ml(-1). Ten commonly used preservatives, namely potassium sorbate, sodium benzoate, (DL) malic acid, citric acid, (L+) tartaric acid, acetic acid, (DL) lactic acid, (L+) ascorbic acid, sodium chloride and sucrose induced no cease in spermatozoa motility even at preservative concentrations higher than permitted by legislation. Dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and acrylamide had no acute effect on spermatozoa motility at concentrations of 500 and 10,000 mg ml(-1), respectively. Robustness of computer aided boar semen motility analysis, tested with 14 different foods inoculated with cereulide producing B. cereus, showed distinct cereulide production in seven samples (although B. cereus growth to counts higher than 8 log CFU g(-1) was noted in 11 samples), in amounts close to those reported in foodborne outbreaks. Test evaluation in 33 samples suspected to hold cereulide showed actual cereulide presence in ten samples and no interference of food matrix

  8. Light-cone quantization of quantum chromodynamics

    SciTech Connect

    Brodsky, S.J. ); Pauli, H.C. )

    1991-06-01

    We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism.

  9. How empty is an empty loss cone?

    NASA Astrophysics Data System (ADS)

    Weissbein, Amir; Sari, Re'em

    2017-06-01

    We consider two-body relaxation in a spherical system with a loss cone. Considering two-dimensional angular momentum space, we focus on 'empty loss cone' systems, where the typical scattering during a dynamical time jd is smaller than the size of the loss cone jlc. As a result, the occupation number within the loss cone is significantly smaller than outside. Classical diffusive treatment of this regime predict exponentially small occupation number deep in the loss cone. We revisit this classical derivation of occupancy distribution of objects in the empty loss cone regime. We emphasize the role of the rare large scatterings and show that the occupancy does not decay exponentially within the loss cone, but it is rather flat, with a typical value ˜[(jd/jlc)]2ln -2(jlc/jmin ) compared to the occupation in circular angular momentum (where jmin is the smallest possible scattering). Implication are that although the loss cone for tidal break of Giants or binaries is typically empty, tidal events that occur significantly inside the loss cone (β ≳ 2) are almost as common as those with β ≅ 1, where β is the ratio between the tidal radius and the periastron. The probability for event with penetration factor >β decreases only as β-1 rather than exponentially. This effect has no influence on events characterized by full loss cone, such as tidal disruption event of ˜1 m⊙ main-sequence star.

  10. Viscumins functionally modulate cell motility-associated gene expression.

    PubMed

    Schötterl, Sonja; Hübner, Miriam; Armento, Angela; Veninga, Vivien; Wirsik, Naita Maren; Bernatz, Simon; Lentzen, Hans; Mittelbronn, Michel; Naumann, Ulrike

    2017-02-01

    In Europe extracts from Viscum album L., the European white-berry mistletoe, are widely used as a complementary cancer therapy. Viscumins (mistletoe lectins, ML) have been scrutinized as important active components of mistletoe and exhibit a variety of anticancer effects such as stimulation of the immune system, induction of cytotoxicity, reduction of tumor cell motility as well as changes in the expression of genes associated with cancer development and progression. By microarray expression analysis, quantitative RT-PCR and RT-PCR based validation of microarray data we demonstrate for the Viscum album extract Iscador Qu and for the lectins Aviscumine and ML-1 that in glioma cells these drugs differentially modulate the expression of genes involved in the regulation of cell migration and invasion, including processes modulating cell architecture and cell adhesion. A variety of differentially expressed genes in ML treated cells are associated with the transforming growth factor (TGF)-β signaling pathway or are targets of TGF-β. ML treatment downregulated the expression of TGF-β itself, of the TGF-β receptor II (TGFBR2), of the TGF-β intracellular signal transducer protein SMAD2, and of matrix-metalloproteinases (MMP) MMP-2 and MMP-14. Even if the changes in gene expression differ between Aviscumine, Iscador Qu and ML-1, the overall regulation of motility associated gene expression by all drugs showed functional effects since tumor cell motility was reduced in a ML-dependent manner. Therefore, ML containing compounds might provide clinical benefit as adjuvant therapeutics in the treatment of patients with invasively growing tumors such as glioblastomas.

  11. Growth

    Treesearch

    John R. Jones; George A. Schier

    1985-01-01

    This chapter considers aspen growth as a process, and discusses some characteristics of the growth and development of trees and stands. For the most part, factors affecting growth are discussed elsewhere, particularly in the GENETICS AND VARIATION chapter and in chapters in PART 11. ECOLOGY. Aspen growth as it relates to wood production is examined in the WOOD RESOURCE...

  12. Cytoplasmic Domain Interactions of Syndecan-1 and Syndecan-4 with α6β4 Integrin Mediate Human Epidermal Growth Factor Receptor (HER1 and HER2)-dependent Motility and Survival*♦

    PubMed Central

    Wang, Haiyao; Jin, Haining; Beauvais, DeannaLee M.; Rapraeger, Alan C.

    2014-01-01

    Epithelial cells are highly dependent during wound healing and tumorigenesis on the α6β4 integrin and its association with receptor tyrosine kinases. Previous work showed that phosphorylation of the β4 subunit upon matrix engagement depends on the matrix receptor syndecan (Sdc)-1 engaging the cytoplasmic domain of the β4 integrin and coupling of the integrin to human epidermal growth factor receptor-2 (HER2). In this study, HER2-dependent migration activated by matrix engagement is compared with migration stimulated by EGF. We find that whereas HER2-dependent migration depends on Sdc1, EGF-dependent migration depends on a complex consisting of human epidermal growth factor receptor-1 (HER1, commonly known as EGFR), α6β4, and Sdc4. The two syndecans recognize distinct sites at the extreme C terminus of the β4 integrin cytoplasmic domain. The binding motif in Sdc1 is QEEXYX, composed in part by its syndecan-specific variable (V) region and in part by the second conserved (C2) region that it shares with other syndecans. A cell-penetrating peptide containing this sequence competes for HER2-dependent epithelial migration and carcinoma survival, although it is without effect on the EGFR-stimulated mechanism. β4 mutants bearing mutations specific for Sdc1 and Sdc4 recognition act as dominant negative mutants to block cell spreading or cell migration that depends on HER2 or EGFR, respectively. The interaction of the α6β4 integrin with the syndecans appears critical for it to be utilized as a signaling platform; migration depends on α3β1 integrin binding to laminin 332 (LN332; also known as laminin 5), whereas antibodies that block α6β4 binding are without effect. These findings indicate that specific syndecan family members are likely to have key roles in α6β4 integrin activation by receptor tyrosine kinases. PMID:25202019

  13. Esophageal motility disorders after gastric banding.

    PubMed

    O'Rourke, R W; Deveney, C W; McConnell, D B; Wolfe, B M; Jobe, B A

    2007-01-01

    The long-term effects of gastric banding on esophageal function are not well described. This report describes a 28-year-old woman who developed signs and symptoms of abnormal esophageal motility and lower esophageal sphincter hypotension after gastric banding for morbid obesity. The current literature addressing the effects of gastric banding on esophageal function in light of this case report is discussed.

  14. Esophageal motility abnormalities in gastroesophageal reflux disease.

    PubMed

    Martinucci, Irene; de Bortoli, Nicola; Giacchino, Maria; Bodini, Giorgia; Marabotto, Elisa; Marchi, Santino; Savarino, Vincenzo; Savarino, Edoardo

    2014-05-06

    Esophageal motility abnormalities are among the main factors implicated in the pathogenesis of gastroesophageal reflux disease. The recent introduction in clinical and research practice of novel esophageal testing has markedly improved our understanding of the mechanisms contributing to the development of gastroesophageal reflux disease, allowing a better management of patients with this disorder. In this context, the present article intends to provide an overview of the current literature about esophageal motility dysfunctions in patients with gastroesophageal reflux disease. Esophageal manometry, by recording intraluminal pressure, represents the gold standard to diagnose esophageal motility abnormalities. In particular, using novel techniques, such as high resolution manometry with or without concurrent intraluminal impedance monitoring, transient lower esophageal sphincter (LES) relaxations, hypotensive LES, ineffective esophageal peristalsis and bolus transit abnormalities have been better defined and strongly implicated in gastroesophageal reflux disease development. Overall, recent findings suggest that esophageal motility abnormalities are increasingly prevalent with increasing severity of reflux disease, from non-erosive reflux disease to erosive reflux disease and Barrett's esophagus. Characterizing esophageal dysmotility among different subgroups of patients with reflux disease may represent a fundamental approach to properly diagnose these patients and, thus, to set up the best therapeutic management. Currently, surgery represents the only reliable way to restore the esophagogastric junction integrity and to reduce transient LES relaxations that are considered to be the predominant mechanism by which gastric contents can enter the esophagus. On that ground, more in depth future studies assessing the pathogenetic role of dysmotility in patients with reflux disease are warranted.

  15. [Increased spontaneous uterine motility with serotonin].

    PubMed

    Lechner, W; Sölder, E; Sölder, B; Kölle, D; Huter, O

    1992-01-01

    The influence of serotonine, a vasoactive neurotransmitter, on the spontaneous motility of uterine strips was investigated. A highly significant (p less than 0.001) increase of uterine activity was observed when serotonine 10(-6) M was added to the perfusing medium.

  16. Methods for fabricating microarrays of motile bacteria.

    PubMed

    Rozhok, Sergey; Shen, Clifton K-F; Littler, Pey-Lih H; Fan, Zhifang; Liu, Chang; Mirkin, Chad A; Holz, Richard C

    2005-04-01

    Motile bacterial cell microarrays were fabricated by attaching Escherichia coli K-12 cells onto predesigned 16-mercaptohexadecanoic acid patterned microarrays, which were covalently functionalized with E. coli antibodies or poly-L-lysine. By utilizing 11-mercaptoundecyl-penta(ethylene glycol) or 11-mercapto-1-undecanol as passivating molecules, nonspecific binding of E. coli was significantly reduced. Microcontact printing and dip-pen nanolithography were used to prepare microarrays for bacterial adhesion, which was studied by optical fluorescence and atomic force microscopy. These data indicate that single motile E. coli can be attached to predesigned line or dot features and binding can occur via the cell body or the flagella of bacteria. Adherent bacteria are viable (remain alive and motile after adhesion to patterned surface features) for more than four hours. Individual motile bacterial cells can be placed onto predesigned surface features that are at least 1.3 microm in diameter or larger. The importance of controlling the adhesion of single bacterial cell to a surface is discussed with regard to biomotor design.

  17. Flagellar motility of the pathogenic spirochetes

    PubMed Central

    Wolgemuth, Charles W.

    2016-01-01

    Bacterial pathogens are often classified by their toxicity and invasiveness. The invasiveness of a given bacterium is determined by how capable the bacterium is at invading a broad range of tissues in its host. Of mammalian pathogens, some of the most invasive come from a group of bacteria known as the spirochetes, which cause diseases such as syphilis, Lyme disease, relapsing fever and leptospirosis. Most of the spirochetes are characterized by their distinct shapes and unique motility. They are long, thin bacteria that can be shaped like flat-waves, helices, or have more irregular morphologies. Like many other bacteria, the spirochetes use long, helical appendages known as flagella to move; however, the spirochetes enclose their flagella in the periplasm, the narrow space between the inner and outer membranes. Rotation of the flagella in the periplasm causes the entire cell body to rotate and/or undulate. These deformations of the bacterium produce the force that drives the motility of these organisms, and it is this unique motility that likely allows these bacteria to be highly invasive in mammals. This review will describe the current state of knowledge on the motility and biophysics of these organisms and provide evidence on how this knowledge can inform our understanding of spirochetal diseases. PMID:26481969

  18. Actin motility: formin a SCAry tail.

    PubMed

    Alberts, Art; Way, Michael

    2011-01-11

    A new biochemical analysis has revealed that the Rickettsia bacterial protein Sca2--recently shown to be essential for virulence and actin-dependent motility--assembles actin filaments using a mechanism that functionally resembles the processive elongation tactics used by formins. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. Disordered oesophageal motility in thyrotoxic myopathy.

    PubMed Central

    Sweatman, M. C.; Chambers, L.

    1985-01-01

    Dysphagia is an uncommon feature of thyrotoxic myopathy, and is usually associated with other signs of bulbar weakness, such as dysarthria and nasal regurgitation. We report a case of thyrotoxicosis presenting with dysphagia due to diminished oesophageal motility associated with significant hypercalcaemia; both abnormalities resolved rapidly following treatment. PMID:4022894

  20. Semiautomated Motility Assay For Determining Toxicity

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Cronise, Raymond

    1996-01-01

    Improved method of assessing toxicities of various substances based on observation of effects of those substances on motilities of manageably small number of cells of protozoan species Tetrahema pyriformis. Provides repeatable, standardized tests with minimal handling by technicians and with minimal exposure of technicians to chemicals. Rapid and economical alternative to Draize test.

  1. Semiautomated Motility Assay For Determining Toxicity

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Cronise, Raymond

    1996-01-01

    Improved method of assessing toxicities of various substances based on observation of effects of those substances on motilities of manageably small number of cells of protozoan species Tetrahema pyriformis. Provides repeatable, standardized tests with minimal handling by technicians and with minimal exposure of technicians to chemicals. Rapid and economical alternative to Draize test.

  2. Shock detachment process on cones in hypervelocity flows

    NASA Astrophysics Data System (ADS)

    Leyva, Ivett A.

    1999-11-01

    The shock detachment process on cones in hypervelocity flows is one of the most sensitive flows to relaxation effects. The critical angle for shock detachment under frozen conditions can be very different from the critical angle under chemical and thermal equilibrium. The rate of increase of the detachment distance with cone angle is also affected by the relaxation rate. The purpose of this study is to explain the effects of nonequilibrium on the shock detachment distance and its growth rate on cones in hypervelocity flows. The study consists of an experimental and a computational program. The experimental part has been carried out at Caltech's hypervelocity reflected shock tunnel (T5). Six different free-stream conditions have been chosen, four using N2 as the test gas and two using CO2. About 170 shots were performed on 24 cones. The cones range in diameter from 2 cm to 16 cm with half-angles varying from 55° to 75°. The experimental data obtained are holographic interferograms of every shot, and surface temperature and pressure measurements for the bigger cones. Extensive numerical simulations were made for the N2 flows and some were also made for the CO2 flows. The code employed is a Navier-Stokes solver that can account for thermal and chemical nonequilibrium in axisymmetric flows. The experimental and computational data obtained for the shock detachment distance confirms a previous theoretical model that predicts the detachment distance will grow more slowly for relaxing flows than for frozen or equilibrium flows. This difference is explained in terms of the behavior of the sonic line inside the shock layer. Different growth rates result when the detachment distance is controlled by the diameter of the cone (frozen and equilibrium cases) than when it is controlled by the extent of the relaxation zone inside the shock layer (nonequilibrium flows). The experimental data are also complemented with computational data to observe the behavior of the detachment

  3. α-Bisabolol Inhibits Invasiveness and Motility in Pancreatic Cancer Through KISS1R Activation.

    PubMed

    Uno, Masanori; Kokuryo, Toshio; Yokoyama, Yukihiro; Senga, Takeshi; Nagino, Masato

    2016-02-01

    α-Bisabolol is a plant-derived, oily sesquiterpene alcohol that induces apoptosis of various cancer cells. We previously reported the antiproliferative effects of α-bisabolol on pancreatic cancer cell lines using in vitro and in vivo experiments. However, the effects of α-bisabolol on tumor invasiveness and motility are still unknown. In this study, demonstrated that α-bisabolol suppressed the invasiveness and motility of a pancreatic cancer cell line. Although Early growth response 1 (EGR1) was involved in antiproliferative effects of α-bisabolol, it had no relationship with the inhibitory effect of α-bisabolol on cellular invasiveness and motility. Polymerase chain reaction analysis revealed that α-bisabolol induced Kisspeptin 1 receptor (KISS1R) in pancreatic cancer cell lines. The inhibition of KISS1R weakened the inhibitory effect of α-bisabolol on invasiveness of pancreatic cancer cells. The results also implied that the inhibitory effects of α-bisabolol on tumor invasiveness and motility are at least partly associated with the activation of KISS1R. However, there is a possibility that other molecular mechanisms of α-bisabolol regulate invasiveness and motility in pancreatic cancer cells. Further investigations are necessary to clarify the precise mechanisms of α-bisabolol activity for clinical application as a novel treatment for pancreatic cancer.

  4. Temperature and pyoverdine-mediated iron acquisition control surface motility of Pseudomonas putida.

    PubMed

    Matilla, Miguel A; Ramos, Juan L; Duque, Estrella; de Dios Alché, Juan; Espinosa-Urgel, Manuel; Ramos-González, María Isabel

    2007-07-01

    Pseudomonas putida KT2440 is unable to swarm at its common temperature of growth in the laboratory (30 degrees C) but exhibits surface motility similar to swarming patterns in other Pseudomonas between 18 degrees C and 28 degrees C. These motile cells show differentiation, consisting on elongation and the presence of surface appendages. Analysis of a collection of mutants to define the molecular determinants of this type of surface movement in KT2440 shows that while type IV pili and lipopolysaccharide O-antigen are requisites flagella are not. Although surface motility of flagellar mutants was macroscopically undistinguishable from that of the wild type, microscopy analysis revealed that these mutants move using a distinct mechanism to that of the wild-type strain. Mutants either in the siderophore pyoverdine (ppsD) or in the FpvA siderophore receptor were also unable to spread on surfaces. Motility in the ppsD strain was totally restored with pyoverdine and partially with the wild-type ppsD allele. Phenotype of the fpvA strain was not complemented by this siderophore. We discuss that iron influences surface motility and that it can be an environmental cue for swarming-like movement in P. putida. This study constitutes the first report assigning an important role to pyoverdine iron acquisition in en masse bacterial surface movement.

  5. The role of motility and chemotaxis in the bacterial colonization of protected surfaces

    PubMed Central

    Tamar, Einat; Koler, Moriah; Vaknin, Ady

    2016-01-01

    Internal epithelial surfaces in humans are both oxygenated and physically protected by a few hundred microns thick hydrogel mucosal layer, conditions that might support bacterial aerotaxis. However, the potential role of aerotaxis in crossing such a thin hydrogel layer is not clear. Here, we used a new setup to study the potential role of motility and chemotaxis in the bacterial colonization of surfaces covered by a thin hydrogel layer and subjected to a vertical oxygen gradient. Using the bacterium Escherichia coli, we show that both non-motile and motile-but-non-chemotactic bacteria could barely reach the surface. However, an acquired mutation in the non-chemotactic bacteria that altered their inherent swimming behavior led to a critical enhancement of surface colonization. Most chemotactic strains accumulated within the bulk of the hydrogel layer, except for the MG1655 strain, which showed a unique tendency to accumulate directly at the oxygenated surface and thus exhibited distinctly enhanced colonization. Even after a long period of bacterial growth, non-motile bacteria could not colonize the hydrogel. Thus, switching motility, which can be spontaneously acquired or altered in vivo, is critical for the colonization of such protected surfaces, whereas aerotaxis capacity clearly expedites surface colonization, and can lead to diverse colonization patterns. PMID:26792493

  6. The motility of axonemal dynein is regulated by the tubulin code.

    PubMed

    Alper, Joshua D; Decker, Franziska; Agana, Bernice; Howard, Jonathon

    2014-12-16

    Microtubule diversity, arising from the utilization of different tubulin genes and from posttranslational modifications, regulates many cellular processes including cell division, neuronal differentiation and growth, and centriole assembly. In the case of cilia and flagella, multiple cell biological studies show that microtubule diversity is important for axonemal assembly and motility. However, it is not known whether microtubule diversity directly influences the activity of the axonemal dyneins, the motors that drive the beating of the axoneme, nor whether the effects on motility are indirect, perhaps through regulatory pathways upstream of the motors, such as the central pair, radial spokes, or dynein regulatory complex. To test whether microtubule diversity can directly regulate the activity of axonemal dyneins, we asked whether in vitro acetylation or deacetylation of lysine 40 (K40), a major posttranslational modification of α-tubulin, or whether proteolytic cleavage of the C-terminal tail (CTT) of α- and β-tubulin, the location of detyrosination, polyglutamylation, and polyglycylation modifications as well as most of the genetic diversity, can influence the activity of outer arm axonemal dynein in motility assays using purified proteins. By quantifying the motility with displacement-weighted velocity analysis and mathematically modeling the results, we found that K40 acetylation increases and CTTs decrease axonemal dynein motility. These results show that axonemal dynein directly deciphers the tubulin code, which has important implications for eukaryotic ciliary beat regulation.

  7. The Motility of Axonemal Dynein Is Regulated by the Tubulin Code

    PubMed Central

    Alper, Joshua D.; Decker, Franziska; Agana, Bernice; Howard, Jonathon

    2014-01-01

    Microtubule diversity, arising from the utilization of different tubulin genes and from posttranslational modifications, regulates many cellular processes including cell division, neuronal differentiation and growth, and centriole assembly. In the case of cilia and flagella, multiple cell biological studies show that microtubule diversity is important for axonemal assembly and motility. However, it is not known whether microtubule diversity directly influences the activity of the axonemal dyneins, the motors that drive the beating of the axoneme, nor whether the effects on motility are indirect, perhaps through regulatory pathways upstream of the motors, such as the central pair, radial spokes, or dynein regulatory complex. To test whether microtubule diversity can directly regulate the activity of axonemal dyneins, we asked whether in vitro acetylation or deacetylation of lysine 40 (K40), a major posttranslational modification of α-tubulin, or whether proteolytic cleavage of the C-terminal tail (CTT) of α- and β-tubulin, the location of detyrosination, polyglutamylation, and polyglycylation modifications as well as most of the genetic diversity, can influence the activity of outer arm axonemal dynein in motility assays using purified proteins. By quantifying the motility with displacement-weighted velocity analysis and mathematically modeling the results, we found that K40 acetylation increases and CTTs decrease axonemal dynein motility. These results show that axonemal dynein directly deciphers the tubulin code, which has important implications for eukaryotic ciliary beat regulation. PMID:25658008

  8. An animated model of reticulorumen motility.

    PubMed

    Gookin, Jody L; Foster, Derek M; Harvey, Alice M; McWhorter, Dan

    2009-01-01

    Understanding reticulorumen motility is important to the assessment of ruminant health and optimal production, and in the recognition, diagnosis, and treatment of disease. Accordingly, the teaching of reticulorumen motility is a staple of all veterinary curricula. This teaching has historically been based on written descriptions, line drawings, or pressure tracings obtained during contraction sequences. We developed an animated model of reticulorumen motility and hypothesized that veterinary students would prefer use of the model over traditional instructional methods. First-year veterinary students were randomly allocated to one of two online learning exercises: with the animated model (Group A) or with text and line drawings (Group B) depicting reticulorumen motility. Learning was assessed with a multiple-choice quiz and feedback on the learning alternatives was obtained by survey. Seventy-four students participated in the study, including 38/42 in Group A and 36/36 in Group B. Sixty-four out of 72 students (89%) responded that they would prefer use of the animated model if only one of the two learning methods was available. A majority of students agreed or strongly agreed that the animated model was easy to understand and improved their knowledge and appreciation of the importance of reticulorumen motility, and would recommend the model to other veterinary students. Interestingly, students in Group B achieved higher scores on examination than students in Group A. This could be speculatively attributed to the inclusion of an itemized list of contraction sequences in the text provided to Group B and failure of Group A students to read the text associated with the animations.

  9. Maintenance of Motility Bias during Cyanobacterial Phototaxis

    PubMed Central

    Chau, Rosanna Man Wah; Ursell, Tristan; Wang, Shuo; Huang, Kerwyn Casey; Bhaya, Devaki

    2015-01-01

    Signal transduction in bacteria is complex, ranging across scales from molecular signal detectors and effectors to cellular and community responses to stimuli. The unicellular, photosynthetic cyanobacterium Synechocystis sp. PCC6803 transduces a light stimulus into directional movement known as phototaxis. This response occurs via a biased random walk toward or away from a directional light source, which is sensed by intracellular photoreceptors and mediated by Type IV pili. It is unknown how quickly cells can respond to changes in the presence or directionality of light, or how photoreceptors affect single-cell motility behavior. In this study, we use time-lapse microscopy coupled with quantitative single-cell tracking to investigate the timescale of the cellular response to various light conditions and to characterize the contribution of the photoreceptor TaxD1 (PixJ1) to phototaxis. We first demonstrate that a community of cells exhibits both spatial and population heterogeneity in its phototactic response. We then show that individual cells respond within minutes to changes in light conditions, and that movement directionality is conferred only by the current light directionality, rather than by a long-term memory of previous conditions. Our measurements indicate that motility bias likely results from the polarization of pilus activity, yielding variable levels of movement in different directions. Experiments with a photoreceptor (taxD1) mutant suggest a supplementary role of TaxD1 in enhancing movement directionality, in addition to its previously identified role in promoting positive phototaxis. Motivated by the behavior of the taxD1 mutant, we demonstrate using a reaction-diffusion model that diffusion anisotropy is sufficient to produce the observed changes in the pattern of collective motility. Taken together, our results establish that single-cell tracking can be used to determine the factors that affect motility bias, which can then be coupled with

  10. Cone Penetrometer Off-Surface Sensor

    SciTech Connect

    Smail, T.R.; French, p.J.; Huffman, R.K.; Hebert, P.S.

    1999-10-20

    Cone penetrometer technology accounts for approximately 50 percent of the subsurface drilling done at the Savannah River Site. This technology provides a means of collecting data for use in the characterization of the subsurface. The cone penetrometer consists of a steel cone attached to a pipe column that is hydraulically inserted into the ground. To allow researchers to accurately measure subsurface properties, without the inherent problems of cone penetrometer equipment, the Savannah River Technology Center has developed the Cone Penetrometer Off-Surface Sensor (CPOSS). The CPOSS design consists of a knife-blade mechanism mounted along the surface of a module capable of attaching to existing cone penetrometer equipment and being deployed at depths of up to 200 feet. CPOSS development is the subject of this report.

  11. Membrane tension and cytoskeleton organization in cell motility

    NASA Astrophysics Data System (ADS)

    Sens, Pierre; Plastino, Julie

    2015-07-01

    Cell membrane shape changes are important for many aspects of normal biological function, such as tissue development, wound healing and cell division and motility. Various disease states are associated with deregulation of how cells move and change shape, including notably tumor initiation and cancer cell metastasis. Cell motility is powered, in large part, by the controlled assembly and disassembly of the actin cytoskeleton. Much of this dynamic happens in close proximity to the plasma membrane due to the fact that actin assembly factors are membrane-bound, and thus actin filaments are generally oriented such that their growth occurs against or near the membrane. For a long time, the membrane was viewed as a relatively passive scaffold for signaling. However, results from the last five years show that this is not the whole picture, and that the dynamics of the actin cytoskeleton are intimately linked to the mechanics of the cell membrane. In this review, we summarize recent findings concerning the role of plasma membrane mechanics in cell cytoskeleton dynamics and architecture, showing that the cell membrane is not just an envelope or a barrier for actin assembly, but is a master regulator controlling cytoskeleton dynamics and cell polarity.

  12. Surface motility of polycyclic aromatic hydrocarbon (PAH)-degrading mycobacteria.

    PubMed

    Fredslund, Line; Sniegowski, Kristel; Wick, Lukas Y; Jacobsen, Carsten S; De Mot, René; Springael, Dirk

    2008-05-01

    Surface motility of the polycyclic aromatic hydrocarbon (PAH)-degrading Mycobacterium gilvum VM552 was tested on agar and agarose plates prepared with varying amounts of gelling agents in the presence and absence of phenanthrene. Extensive spreading, originating from the point of inoculation, was observed on the surfaces of plates prepared with up to 0.3% agar and up to 0.6% agarose. The spreading velocities were 15.8 mm d(-1) on 0.3% agar and 19.5 mm d(-1) on 0.3% agarose plates. No evidence was found of accelerated or directed surface motility towards PAH crystals. The morphology of spreading M. gilvum VM552 colonies depended on both the carbon source and the type and concentration of the gelling agent. In 0.3% agar plates, M. gilvum VM552 cells were organized in 1-2-mm-wide branches of 1-5 cm length, while on agarose they slid as a homogenous monolayer across the surface. Microscopic inspection of the colonies on agar surfaces suggested that formation of branches was the combined effect of: (i) cell division and growth at the tip of a branch; (ii) propulsion of cells from the mature basal parts of a branch towards the tip; and (iii) physiologically induced reduced friction between cells and agar. Similar surface migration patterns were observed for the anthracene-degrading M. frederiksbergense LB501T.

  13. Membrane tension and cytoskeleton organization in cell motility.

    PubMed

    Sens, Pierre; Plastino, Julie

    2015-07-15

    Cell membrane shape changes are important for many aspects of normal biological function, such as tissue development, wound healing and cell division and motility. Various disease states are associated with deregulation of how cells move and change shape, including notably tumor initiation and cancer cell metastasis. Cell motility is powered, in large part, by the controlled assembly and disassembly of the actin cytoskeleton. Much of this dynamic happens in close proximity to the plasma membrane due to the fact that actin assembly factors are membrane-bound, and thus actin filaments are generally oriented such that their growth occurs against or near the membrane. For a long time, the membrane was viewed as a relatively passive scaffold for signaling. However, results from the last five years show that this is not the whole picture, and that the dynamics of the actin cytoskeleton are intimately linked to the mechanics of the cell membrane. In this review, we summarize recent findings concerning the role of plasma membrane mechanics in cell cytoskeleton dynamics and architecture, showing that the cell membrane is not just an envelope or a barrier for actin assembly, but is a master regulator controlling cytoskeleton dynamics and cell polarity.

  14. Programming Retinal Stem Cells into Cone Photoreceptors

    DTIC Science & Technology

    2015-12-01

    to program human stem cells directly into cones. Using RNA -seq, we identified several genes that are upregulated in advance of the earliest...reverse vision loss. 15. SUBJECT TERMS Cone photoreceptor, retina, retinal stem cell, Otx2, Onecut1, Blimp1, RNA -seq., transcription factors, and...1 Keywords: 1. Cone photoreceptor 2. Retina 3. Retinal stem cell 4. Otx2 5. Onecut1 6. Blimp1 7. RNA -seq. 8. Transcription factors 9

  15. Light-cones, almost light-cones and almost-complex light-cones

    NASA Astrophysics Data System (ADS)

    Newman, Ezra T.

    2017-08-01

    We point out (and then apply to a general situation) an unusual relationship among a variety of null geodesic congruences; (a) the generators of ordinary light-cones and (b) certain (related) shear-free but twisting congruences in Minkowski space-time as well as (c) asymptotically shear-free null geodesic congruences that exist in the neighborhood of Penrose's I^{ +} in Einstein or Einstein-Maxwell asymptotically flat-space-times. We refer to these geodesic congruences respectively as: Lignt-Cones (LCs), as "Almost-Complex"-Light-Cones (ACLCs), [though they are real they resemble complex light-cones in complex Minkowski space] and finally to a family of congruences in asymptotically flat-spaces as ` Almost Light-Cones' (ALC). The two essential points of resemblance among the three families are: (1) they are all either shear-free or asymptotically shear-free and (2) in each family the individual members of the family can be labeled by the points in a real or complex four-dimensional manifold. As an example, the Minkowski space LCs are labeled by the (real) coordinate value of their apex. In the case of (ACLCs) (complex coordinate values), the congruences will have non-vanishing twist whose magnitude is determined by the imaginary part of the complex coordinate values. In studies of gravitational radiation, Bondi-type of null surfaces and their associated Bondi coordinates have been almost exclusively used for calculations. It turns out that some surprising relations arise if, instead of the Bondi coordinates, one uses ALCs and their associated coordinate systems in the analysis of the Einstein-Maxwell equations in the neighborhood of I+. More explicitly and surprisingly, the asymptotic Bianchi Identities (arising directly from the Einstein equations), expressed in the coordinates of the ALCs, turn directly into many of the standard definitions and equations and relations of classical mechanics coupled with Maxwell's equations. These results extend and generalize the

  16. Cone opsins, colour blindness and cone dystrophy: Genotype-phenotype correlations.

    PubMed

    Gardner, J C; Michaelides, M; Hardcastle, A J

    2016-05-25

    X-linked cone photoreceptor disorders caused by mutations in the OPN1LW (L) and OPN1MW (M) cone opsin genes on chromosome Xq28 include a range of conditions from mild stable red-green colour vision deficiencies to severe cone dystrophies causing progressive loss of vision and blindness. Advances in molecular genotyping and functional analyses of causative variants, combined with deep retinal phenotyping, are unravelling genetic mechanisms underlying the variability of cone opsin disorders.

  17. Esophageal motility disorders in HIV patients.

    PubMed

    Zalar, Alberto E; Olmos, Martín A; Piskorz, Eduardo L; Magnanini, Fernando L

    2003-05-01

    Opportunistic esophageal infections (Candida, cytomegalovirus, herpes simplex virus) and idiophatic esophageal ulcerations are commonly found in HIV patients. However, motility disorders of the esophagus have seldom been investigated in this population. The aim of this prospective study was to determine the presence of motility disorders in HIV patients with esophageal symptoms (with or without associated lesions detected by endoscopy) and in HIV patients without esophageal symptoms and normal esophagoscopy. Eigthteen consecutive HIV patients (10 male, 8 female, ages 20-44 years, mean age 33.5; 8 HIV positive and 10 AIDS) were studied prospectively. Nine patients complained of esophageal symptoms, e.g, dysphagia/odynophagia (group 1) and 9 had symptoms not related to esophageal disease, such as diarrhea, abdominal pain, or gastrointestinal bleeding (group 2). All patients underwent upper endoscopy; mucosal biopsies were taken when macroscopic esophageal lesions were identified or when the patients were symptomatic even if the esophageal mucosa was normal. Esophageal manometry was performed in the 18 patients, using a 4-channel water-perfused system according to a standardized technique. Sixteen of the 18 patients (88.8%) had baseline manometric abnormalities. In group 1, 8/9 patients had esophageal motility disorders: nutcrackeresophagus in 1, hypertensive lower esophageal sphincter (LES) with incomplete relaxation in 2, nonspecific esophageal motility disorders (NEMD) in 3, diffuse esophageal spasm in 1, esophageal hypocontraction with low LES pressure in 1. Six of these 9 patients had lesions detected by endoscopy: CMV ulcers in 2, idiopathic ulcers in 1, candidiasis in 1, idiopathic ulcer + candidiasis in 1, nonspecific esophagitis in 1; and 3/9 had normal endoscopy and normal esophageal biopsies. In group 2, 8/9 patients had abnormal motility: hypertensive LES with incomplete relaxation in 1, nutcracker esophagus in 2, esophageal hypocontraction in 3, and NEMD

  18. Ionic emission from Taylor cones

    NASA Astrophysics Data System (ADS)

    Castro Reina, Sergio

    Electrified Taylor cones have been seen as an efficient way to generate thrust for space propulsion. Especially the pure ionic regime (PIR) combines a very high specific impulse (thrust per unit mass) and efficiency, which is very important to reduce fuel transportation costs. The PIR has been primarily based on electrosprays of liquid metals [Swatik and Hendricks 1968, Swatik 1969]. However, emissions dominated by or containing exclusively ions have also been observed from nonmetallic purely ionic substances, initially sulfuric acid [Perel et al. 1969], and more recently room temperature molten salts referred to as ionic liquids (ILs) [Romero-Sanz et al. 2003]. The recent use of the liquid metal ion source (LMIS) with ILs, becoming this "new" source to be known as ionic liquid ion source (ILIS) [Lozano and Martinez-Sanchez 2005], has shown important differences on the emission from Taylor cones with the traditional hollow capillary. This new source seems to be more flexible than the capillary [Paulo, Sergio, carlos], although its low emission level (low thrust) is an important drawback from the space propulsion point of view. Throughout the thesis I have studied some aspects of the ionic emission from ionic liquid Taylor cones and the influence of the properties of the liquids and the characteristic of source on the emission. I have unraveled the reason why ILIS emits such low currents (˜200 nA) and found a way to solve this problem increasing the current up to capillary levels (˜1000 nA) [Castro and Fernandez de la Mora 2009]. I have also tried to reduce ion evaporation while reducing the emitted droplet size in order to increase the thrust generated while keeping the efficiency relatively high and I have measured the energy of evaporation of several cations composing ionic liquids, mandatory step to understand ionic evaporation.

  19. Cyclic Di-GMP Regulates Type IV Pilus-Dependent Motility in Myxococcus xanthus

    PubMed Central

    Skotnicka, Dorota; Petters, Tobias; Heering, Jan; Hoppert, Michael; Kaever, Volkhard

    2015-01-01

    ABSTRACT The nucleotide-based second messenger bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP) is involved in regulating a plethora of processes in bacteria that are typically associated with lifestyle changes. Myxococcus xanthus undergoes major lifestyle changes in response to nutrient availability, with the formation of spreading colonies in the presence of nutrients and spore-filled fruiting bodies in the absence of nutrients. Here, we investigated the function of c-di-GMP in M. xanthus and show that this bacterium synthesizes c-di-GMP during growth. Manipulation of the c-di-GMP level by expression of either an active, heterologous diguanylate cyclase or an active, heterologous phosphodiesterase correlated with defects in type IV pilus (T4P)-dependent motility, whereas gliding motility was unaffected. An increased level of c-di-GMP correlated with reduced transcription of the pilA gene (which encodes the major pilin of T4P), reduced the assembly of T4P, and altered cell agglutination, whereas a decreased c-di-GMP level correlated with altered cell agglutination. The systematic inactivation of the 24 genes in M. xanthus encoding proteins containing GGDEF, EAL, or HD-GYP domains, which are associated with c-di-GMP synthesis, degradation, or binding, identified three genes encoding proteins important for T4P-dependent motility, whereas all mutants had normal gliding motility. Purified DmxA had diguanylate cyclase activity, whereas the hybrid histidine protein kinases TmoK and SgmT, each of which contains a GGDEF domain, did not have diguanylate cyclase activity. These results demonstrate that c-di-GMP is important for T4P-dependent motility in M. xanthus. IMPORTANCE We provide the first direct evidence that M. xanthus synthesizes c-di-GMP and demonstrate that c-di-GMP is important for T4P-dependent motility, whereas we did not obtain evidence that c-di-GMP regulates gliding motility. The data presented uncovered a novel mechanism for regulation of T4P

  20. gdf6a Is Required for Cone Photoreceptor Subtype Differentiation and for the Actions of tbx2b in Determining Rod Versus Cone Photoreceptor Fate

    PubMed Central

    DuVal, Michèle G.; Oel, A. Phillip; Allison, W. Ted

    2014-01-01

    Functional vision restoration is within reach via stem cell therapy, but one of the largest obstacles is the derivation of colour-sensitive cone photoreceptors that are required for high-acuity daytime vision. To enhance progress made using nocturnal murine models, we instead utilize cone-rich zebrafish and herein investigate relationships between gdf6a and tbx2b in cone photoreceptor development. Growth/differentiation factor 6a (gdf6a), a bone morphogenetic protein family ligand, is an emerging factor in photoreceptor degenerative diseases. The T-box transcription factor tbx2b is required to specify UV cone photoreceptor fate instead of rod photoreceptor fate. Interactions between these factors in cone development would be unanticipated, considering the discrete phenotypes in their respective mutants. However, gdf6a positively modulates the abundance of tbx2b transcript during early eye morphogenesis, and we extended this conclusion to later stages of retinal development comprising the times when photoreceptors differentiate. Despite this, gdf6a−/− larvae possess a normal relative number of UV cones and instead present with a low abundance of blue cone photoreceptors, approximately half that of siblings (p<0.001), supporting a differential role for gdf6a amongst the spectral subtypes of cone photoreceptors. Further, gdf6a−/− larvae from breeding of compound heterozygous gdf6a+/−;tbx2b+/− mutants exhibit the recessive lots-of-rods phenotype (which also shows a paucity of UV cones) at significantly elevated rates (44% or 48% for each of two tbx2b alleles, χ2 p≤0.007 for each compared to expected Mendelian 25%). Thus the gdf6a−/− background sensitizes fish such that the recessive lots-of-rods phenotype can appear in heterozygous tbx2b+/− fish. Overall, this work establishes a novel link between tbx2b and gdf6a in determining photoreceptor fates, defining the nexus of an intricate pathway influencing the abundance of cone spectral subtypes and

  1. gdf6a is required for cone photoreceptor subtype differentiation and for the actions of tbx2b in determining rod versus cone photoreceptor fate.

    PubMed

    Duval, Michèle G; Oel, A Phillip; Allison, W Ted

    2014-01-01

    Functional vision restoration is within reach via stem cell therapy, but one of the largest obstacles is the derivation of colour-sensitive cone photoreceptors that are required for high-acuity daytime vision. To enhance progress made using nocturnal murine models, we instead utilize cone-rich zebrafish and herein investigate relationships between gdf6a and tbx2b in cone photoreceptor development. Growth/differentiation factor 6a (gdf6a), a bone morphogenetic protein family ligand, is an emerging factor in photoreceptor degenerative diseases. The T-box transcription factor tbx2b is required to specify UV cone photoreceptor fate instead of rod photoreceptor fate. Interactions between these factors in cone development would be unanticipated, considering the discrete phenotypes in their respective mutants. However, gdf6a positively modulates the abundance of tbx2b transcript during early eye morphogenesis, and we extended this conclusion to later stages of retinal development comprising the times when photoreceptors differentiate. Despite this, gdf6a-/- larvae possess a normal relative number of UV cones and instead present with a low abundance of blue cone photoreceptors, approximately half that of siblings (p<0.001), supporting a differential role for gdf6a amongst the spectral subtypes of cone photoreceptors. Further, gdf6a-/- larvae from breeding of compound heterozygous gdf6a+/-;tbx2b+/- mutants exhibit the recessive lots-of-rods phenotype (which also shows a paucity of UV cones) at significantly elevated rates (44% or 48% for each of two tbx2b alleles, χ2 p≤0.007 for each compared to expected Mendelian 25%). Thus the gdf6a-/- background sensitizes fish such that the recessive lots-of-rods phenotype can appear in heterozygous tbx2b+/- fish. Overall, this work establishes a novel link between tbx2b and gdf6a in determining photoreceptor fates, defining the nexus of an intricate pathway influencing the abundance of cone spectral subtypes and specifying rod vs

  2. Nested-cone transformer antenna

    DOEpatents

    Ekdahl, Carl A.

    1991-01-01

    A plurality of conical transmission lines are concentrically nested to form n output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated.

  3. Nested-cone transformer antenna

    DOEpatents

    Ekdahl, C.A.

    1991-05-28

    A plurality of conical transmission lines are concentrically nested to form an output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated. 6 figures.

  4. Possible Tuff Cones In Isidis Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Seabrook, A. M.; Rothery, D. A.; Bridges, J. C.; Wright, I. P.

    The Beagle 2 lander of the ESA Mars Express mission will touch down on the martian surface in December 2003 to conduct a primarily exobiological mission. The landing site will be within Isidis Planitia, an 1100 km diameter impact basin. Isidis contains many sub-kilometre-sized cones. These can be found singly, in clusters, and in straight or arcuate chains extending many kilometres. In some areas of the basin these cones can occupy over 10% of the surface, with the most densely populated areas being in the older western half of the basin. There are few cones around the basin rim. There is also variation in the erosional state of the