Science.gov

Sample records for growth cone motility

  1. Mechanochemical regulation of growth cone motility

    PubMed Central

    Kerstein, Patrick C.; Nichol IV, 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. Radixin Is Involved in Lamellipodial Stability during Nerve Growth Cone Motility

    PubMed Central

    Castelo, Leslie; Jay, Daniel G.

    1999-01-01

    Immunocytochemistry and in vitro studies have suggested that the ERM (ezrin-radixin-moesin) protein, radixin, may have a role in nerve growth cone motility. We tested the in situ role of radixin in chick dorsal root ganglion growth cones by observing the effects of its localized and acute inactivation. Microscale chromophore-assisted laser inactivation (micro-CALI) of radixin in growth cones causes a 30% reduction of lamellipodial area within the irradiated region whereas all control treatments did not affect lamellipodia. Micro-CALI of radixin targeted to the middle of the leading edge often split growth cones to form two smaller growth cones during continued forward movement (>80%). These findings suggest a critical role for radixin in growth cone lamellipodia that is similar to ezrin function in pseudopodia of transformed fibroblasts. They are consistent with radixin linking actin filaments to each other or to the membrane during motility. PMID:10233159

  3. Distinctions in growth cone morphology and motility between monopolar and multipolar neurons in Drosophila CNS cultures.

    PubMed

    Kim, Y T; Wu, C F

    1991-04-01

    Growth cones play a central role in determining neurite extension, pathfinding and branching, and in establishing synaptic connections. This paper describes an initial characterization of growth cone morphology and behavior in dissociated larval central nervous system (CNS) cultures of Drosophila. Contrast-enhanced video images of growth cones in monopolar and multipolar neurons were characterized by employing morphometric parameters such as the number and length of filopodia, and the area and roundness of the lamellipodia. Behavior of growth cones was analyzed by a motility index and boundary flow plots originally devised for measuring motility in other cellular systems. We found that separate CNS regions yielded cultures of different major cell types with distinct neuritic patterns that could be correlated with the morphology and motility of the associated growth cones. Monopolar neurons were the major cell type in brain cultures, whereas multipolar neurons were predominant in ventral ganglion cultures. Moreover, the growth cones of monopolar neurons, which are likely to be associated with the axonal processes, differed from those of multipolar neurons, which might be related to dendritic terminals. Growth cones in monopolar neurons had larger lamellipodia of less erratic shape accompanied by fewer and shorter filopodia, and, when active, displayed much higher motility and less directionality in motion. Alternatively, these morphological and behavioral distinctions between monopolar and multipolar neurons may result from intrinsic differences in membrane adhesion and intracellular transport properties.

  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 growth cone motility and morphology by LIM kinase and Slingshot via phosphorylation and dephosphorylation of cofilin.

    PubMed

    Endo, Mitsuharu; Ohashi, Kazumasa; Sasaki, Yukio; Goshima, Yoshio; Niwa, Ryusuke; Uemura, Tadashi; Mizuno, Kensaku

    2003-04-01

    Growth cone motility and morphology are based on actin-filament dynamics. Cofilin plays an essential role for the rapid turnover of actin filaments by severing and depolymerizing them. The activity of cofilin is repressed by phosphorylation at Ser3 by LIM kinase (LIMK, in which LIM is an acronym of the three gene products Lin-11, Isl-1, and Mec-3) and is reactivated by dephosphorylation by phosphatases, termed Slingshot (SSH). We investigated the roles of cofilin, LIMK, and SSH in the growth cone motility and morphology and neurite extension by expressing fluorescence protein-labeled cofilin, LIMK1, SSH1, or their mutants in chick dorsal root ganglion (DRG) neurons and then monitoring live images of growth cones by time-lapse video fluorescence microscopy. The expression of LIMK1 remarkably repressed growth cone motility and neurite extension, whereas the expression of SSH1 or a nonphosphorylatable S3A mutant of cofilin enhanced these events. The fan-like shape of growth cones was disorganized by the expression of any of these proteins. The repressive effects on growth cone behavior by LIMK1 expression were significantly rescued by the coexpression of S3A-cofilin or SSH1. These findings suggest that LIMK1 and SSH1 play critical roles in controlling growth cone motility and morphology and neurite extension by regulating the activity of cofilin and may be involved in signaling pathways that regulate stimulus-induced growth cone guidance. Using various mutants of cofilin, we also obtained evidence that the actin-filament-severing activity of cofilin is critical for growth cone motility and neurite extension.

  6. Suppression of Radixin and Moesin Alters Growth Cone Morphology, Motility, and Process Formation In Primary Cultured Neurons

    PubMed Central

    Paglini, Gabriela; Kunda, Patricia; Quiroga, Santiago; Kosik, Kenneth; Cáceres, Alfredo

    1998-01-01

    In this study we have examined the cellular functions of ERM proteins in developing neurons. The results obtained indicate that there is a high degree of spatial and temporal correlation between the expression and subcellular localization of radixin and moesin with the morphological development of neuritic growth cones. More importantly, we show that double suppression of radixin and moesin, but not of ezrin–radixin or ezrin–moesin, results in reduction of growth cone size, disappearance of radial striations, retraction of the growth cone lamellipodial veil, and disorganization of actin filaments that invade the central region of growth cones where they colocalize with microtubules. Neuritic tips from radixin–moesin suppressed neurons displayed high filopodial protrusive activity; however, its rate of advance is 8–10 times slower than the one of growth cones from control neurons. Radixin–moesin suppressed neurons have short neurites and failed to develop an axon-like neurite, a phenomenon that appears to be directly linked with the alterations in growth cone structure and motility. Taken collectively, our data suggest that by regulating key aspects of growth cone development and maintenance, radixin and moesin modulate neurite formation and the development of neuronal polarity. PMID:9786954

  7. D1-type dopamine receptors inhibit growth cone motility in cultured retina neurons: evidence that neurotransmitters act as morphogenic growth regulators in the developing central nervous system.

    PubMed Central

    Lankford, K L; DeMello, F G; Klein, W L

    1988-01-01

    Precedent exists for the early development and subsequent down-regulation of neurotransmitter receptor systems in the vertebrate central nervous system, but the function of such embryonic receptors has not been established. Here we show that stimulation of early-developing dopamine receptors in avian retina cells greatly inhibits the motility of neuronal growth cones. Neurons from embryonic chicken retinas were cultured in low-density monolayers, and their growth cones were observed with phase-contrast or video-enhanced-contrast-differential-interference-contrast (VEC-DIC) microscopy. Approximately 25% of the neurons responded to micromolar dopamine with a rapid reduction in filopodial activity followed by a flattening of growth cones and retraction of neurites. The response occurred at all ages examined (embryonic day-8 retinal neurons cultured on polylysine-coated coverslips for 1-7 days), although neurite retraction was greatest in younger cultures. Effects of dopamine on growth cone function could be reversed by haloperidol or (+)-SCH 23390, whereas forskolin elicited a response similar to dopamine; these data show the response was receptor-mediated, acting through a D1-type system, and are consistent with the use of cAMP as a second messenger. The experiments provide strong support for the hypothesis that neurotransmitters, besides mediating transynaptic signaling in the adult, may have a role in neuronal differentiation as growth regulators. Images PMID:3380807

  8. D1-type dopamine receptors inhibit growth cone motility in cultured retina neurons: evidence that neurotransmitters act as morphogenic growth regulators in the developing central nervous system.

    PubMed Central

    Lankford, K L; DeMello, F G; Klein, W L

    1988-01-01

    Precedent exists for the early development and subsequent down-regulation of neurotransmitter receptor systems in the vertebrate central nervous system, but the function of such embryonic receptors has not been established. Here we show that stimulation of early-developing dopamine receptors in avian retina cells greatly inhibits the motility of neuronal growth cones. Neurons from embryonic chicken retinas were cultured in low-density monolayers, and their growth cones were observed with phase-contrast or video-enhanced-contrast-differential-interference-contrast (VEC-DIC) microscopy. Approximately 25% of the neurons responded to micromolar dopamine with a rapid reduction in filopodial activity followed by a flattening of growth cones and retraction of neurites. The response occurred at all ages examined (embryonic day-8 retinal neurons cultured on polylysine-coated coverslips for 1-7 days), although neurite retraction was greatest in younger cultures. Effects of dopamine on growth cone function could be reversed by haloperidol or (+)-SCH 23390, whereas forskolin elicited a response similar to dopamine; these data show the response was receptor-mediated, acting through a D1-type system, and are consistent with the use of cAMP as a second messenger. The experiments provide strong support for the hypothesis that neurotransmitters, besides mediating transynaptic signaling in the adult, may have a role in neuronal differentiation as growth regulators. Images PMID:3357895

  9. Growth cone collapse assay.

    PubMed

    Cook, Geoffrey M W; Jareonsettasin, Prem; Keynes, Roger J

    2014-01-01

    The growth cone collapse assay has proved invaluable in detecting and purifying axonal repellents. Glycoproteins/proteins present in detergent extracts of biological tissues are incorporated into liposomes, added to growth cones in culture and changes in morphology are then assessed. Alternatively purified or recombinant molecules in aqueous solution may be added directly to the cultures. In both cases after a defined period of time (up to 1 h), the cultures are fixed and then assessed by inverted phase contrast microscopy for the percentage of growth cones showing a collapsed profile with loss of flattened morphology, filopodia, and lamellipodia.

  10. Biochemical pharmacology of isolated neuronal growth cones: implications for synaptogenesis.

    PubMed

    Lockerbie, R O

    1990-01-01

    The neuronal growth cone is critical to the establishment of neuronal polarity through its motile, pathfinding and target recognition properties exhibited during synaptogenesis. Subcellular fractionation procedures yielding milligram quantities of isolated growth cones has allowed for biochemical and pharmacological investigation of intrinsic growth cone components that are likely to be involved in regulation of growth cone function in neuronal development. These 'mapping' studies of growth cone components are prerequisites to elucidating the mechanisms by which extracellular factors influence the motility, adhesion and directed growth of the growth cone. For example, neurotransmitters and polypeptide growth factors which have been shown in other systems to modulate growth cone behavior are presumed to act through receptors on the growth cone, inducing second-messenger molecule formation and consequent modification and regulation of proteins effecting the response(s) of the growth cone (i.e. proteins involved in motility, adhesion and membrane turnover). In a relatively short period of time, work with the isolated growth cone preparation has identified, in independent studies, many of the elements involved in this proposed scheme of events, including transmitter receptors, second-messenger cascades, and second-messenger post-translational modifications. An obvious future goal will be to analyze in more detail the intracellular events, and the relationships between them, in the growth cone and how they transmit extracellular signals into responses such as motility and adhesivity which underly the growth cone's synaptogenic properties. It is to be expected that much of this information will come forth from experimentation with the isolated growth cone preparation.

  11. Increase in Growth Cone Size Correlates with Decrease in Neurite Growth Rate

    PubMed Central

    Ren, Yuan

    2016-01-01

    Several important discoveries in growth cone cell biology were made possible by the use of growth cones derived from cultured Aplysia bag cell neurons, including the characterization of the organization and dynamics of the cytoskeleton. The majority of these Aplysia studies focused on large growth cones induced by poly-L-lysine substrates at early stages in cell culture. Under these conditions, the growth cones are in a steady state with very little net advancement. Here, we offer a comprehensive cellular analysis of the motile behavior of Aplysia growth cones in culture beyond this pausing state. We found that average growth cone size decreased with cell culture time whereas average growth rate increased. This inverse correlation of growth rate and growth cone size was due to the occurrence of large growth cones with a peripheral domain larger than 100 μm2. The large pausing growth cones had central domains that were less consistently aligned with the direction of growth and could be converted into smaller, faster-growing growth cones by addition of a three-dimensional collagen gel. We conclude that the significant lateral expansion of lamellipodia and filopodia as observed during these culture conditions has a negative effect on neurite growth. PMID:27274874

  12. Lipid rafts mediate chemotropic guidance of nerve growth cones.

    PubMed

    Guirland, Carmine; Suzuki, Shingo; Kojima, Masami; Lu, Bai; Zheng, James Q

    2004-04-01

    Axon guidance requires signal transduction of extracellular cues through the plasma membrane for directional motility. Here we present evidence that cholesterol- and sphingolipid-enriched membrane microdomains (lipid rafts) mediate specific guidance responses of nerve growth cones. Disruption of lipid rafts by various approaches targeting cholesterol or gangliosides selectively abolished growth cone attraction and repulsion in BDNF and netrin-1 gradients, respectively, without affecting glutamate-induced attraction. Interestingly, local raft disruption on one side of the growth cone in bath BDNF or netrin-1 produced opposite turning responses to that induced by the gradients. Raft manipulation also blocked Semaphorin 3A-induced growth cone repulsion, inhibition, and collapse. Finally, guidance responses appeared to involve raft-dependent activation of p42/p44 MAPK and ligand-induced receptor recruitment to lipid rafts. Together with the observation of asymmetric receptor-raft associations at the growth cone in guidance gradients, our findings indicate that localized signaling through membrane rafts plays a role in mediating guidance actions of extracellular cues on developing axons. PMID:15066264

  13. The role of Arp2/3 in growth cone actin dynamics and guidance is substrate dependent.

    PubMed

    San Miguel-Ruiz, José E; Letourneau, Paul C

    2014-04-23

    During development extrinsic guidance cues modulate the peripheral actin network in growth cones to direct axons to their targets. We wanted to understand the role of the actin nucleator Arp2/3 in growth cone actin dynamics and guidance. Since growth cones migrate in association with diverse adhesive substrates during development, we probed the hypothesis that the functional significance of Arp2/3 is substrate dependent. We report that Arp2/3 inhibition led to a reduction in the number of filopodia and growth cone F-actin content on laminin and L1. However, we found substrate-dependent differences in growth cone motility, actin retrograde flow, and guidance after Arp2/3 inhibition, suggesting that its role, and perhaps that of other actin binding proteins, in growth cone motility is substrate dependent. PMID:24760849

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

    PubMed Central

    Vitriol, Eric A; Zheng, James Q

    2012-01-01

    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 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 their targets. Research in the past two decades has also gained significant insight into the mechanisms by which growth cones translate extracellular signals into directional migration. This review aims to examine new progress towards 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. PMID:22445336

  15. 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.

  16. 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.

  17. 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

  18. The cytoskeletons of isolated, neuronal growth cones.

    PubMed

    Gordon-Weeks, P R

    1987-06-01

    We have examined by electron microscopy the cytoskeletons of growth cones isolated from neonatal rat forebrain by the method of Gordon-Weeks and Lockerbie [Gordon-Weeks and Lockerbie (1984) Neuroscience 13, 119-136]. When fixed in suspension with conventional fixatives, isolated growth cones contain a central region filled with a branching system of smooth endoplasmic reticulum and a cortical region immediately beneath the plasma membrane that is relatively free of organelles and is composed of an amorphous granular cytoplasm. The filopodia of isolated growth cones are also devoid of organelles and contain a cytoplasm that is similar in appearance to that in the cortical region. No microtubules or neurofilaments have been found in these growth cones. When isolated growth cones were prepared for electron microscopy by a method which preserves actin filaments [Boyles, Anderson and Hutcherson (1985) J. Histochem. Cytochem. 33, 1116-1128], microfilaments were found throughout the cortical cytoplasm. In the filopodia, the microfilaments were bundled together and oriented longitudinally. Filopodial microfilament bundles often extended into the body of the growth cone and could traverse it completely. Inclusion of Triton X-100 (1% v/v) in the fixative solubilized the membranes and soluble cytoplasmic proteins of growth cones, allowing an unobscured view of the microfilament cytoskeleton including the core bundle of microfilaments in filopodia. Suspended within the cytoskeleton were the coats of coated vesicles. These were particularly numerous at the broad bases of filopodia. Microfilaments bound heavy meromyosin and were cytochalasin B (2.0 X 10(-7) M) sensitive. Individual microfilaments branched and within filopodia they were extensively cross-linked by thin (7 nm) filaments. Microtubules and neurofilaments were not seen in these cytoskeletons despite the fact that the fixative contained a Ca2+ chelator. When growth cones were preincubated in taxol (14 microM) their

  19. Regulated plasmalemmal expansion in nerve growth cones.

    PubMed

    Lockerbie, R O; Miller, V E; Pfenninger, K H

    1991-03-01

    To study the mechanisms underlying plasmalemmal expansion in the nerve growth cone, a cell-free assay was developed to quantify membrane addition, using ligand binding and sealed growth cone particles isolated by subcellular fractionation from fetal rat brain. Exposed versus total binding sites of 125I-wheat germ agglutinin were measured in the absence or presence of saponin, respectively, after incubation with various agents. Ca2(+)-ionophore A23187 in the presence of Ca2+ increases the number of binding sites (Bmax) but does not change their affinity (KD), indicating that new receptors appear on the plasma membrane. Similarly, membrane depolarization by high K+ or veratridine significantly induces, in a Ca2(+)-dependent manner, the externalization of lectin binding sites from an internal pool. Morphometric analysis of isolated growth cones indicates that A23187 and high K+ treatment cause a significant reduction in a specific cytoplasmic membrane compartment, thus confirming the lectin labeling results and identifying the plasmalemmal precursor. The isolated growth cones take up gamma-amino-butyric acid and serotonin, but show no evidence for Ca2(+)-dependent transmitter release so that transmitter exocytosis is dissociated from plasmalemmal expansion. The data demonstrate that plasmalemmal expansion in the growth cone is a regulated process and identify an internal pool of precursor membrane.

  20. Regulated plasmalemmal expansion in nerve growth cones

    PubMed Central

    1991-01-01

    To study the mechanisms underlying plasmalemmal expansion in the nerve growth cone, a cell-free assay was developed to quantify membrane addition, using ligand binding and sealed growth cone particles isolated by subcellular fractionation from fetal rat brain. Exposed versus total binding sites of 125I-wheat germ agglutinin were measured in the absence or presence of saponin, respectively, after incubation with various agents. Ca2(+)-ionophore A23187 in the presence of Ca2+ increases the number of binding sites (Bmax) but does not change their affinity (KD), indicating that new receptors appear on the plasma membrane. Similarly, membrane depolarization by high K+ or veratridine significantly induces, in a Ca2(+)-dependent manner, the externalization of lectin binding sites from an internal pool. Morphometric analysis of isolated growth cones indicates that A23187 and high K+ treatment cause a significant reduction in a specific cytoplasmic membrane compartment, thus confirming the lectin labeling results and identifying the plasmalemmal precursor. The isolated growth cones take up gamma-amino-butyric acid and serotonin, but show no evidence for Ca2(+)-dependent transmitter release so that transmitter exocytosis is dissociated from plasmalemmal expansion. The data demonstrate that plasmalemmal expansion in the growth cone is a regulated process and identify an internal pool of precursor membrane. PMID:1999470

  1. 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.

  2. GABA release from mouse axonal growth cones

    PubMed Central

    Gao, Xiao-Bing; van den Pol, Anthony N

    2000-01-01

    Using developing hypothalamic neurons from transgenic mice that express high levels of green fluorescent protein in growing axons, and an outside-out patch from mature neuronal membranes that contain neurotransmitter receptors as a sensitive detector, we found that GABA is released by a vesicular mechanism from the growth cones of developing axons prior to synapse formation. A low level of GABA release occurs spontaneously from the growth cone, and this is substantially increased by evoked action potentials. Neurotransmitters such as acetylcholine can enhance protein kinase C (PKC) activity even prior to synapse formation; PKC activation caused a substantial increase in spontaneous GABA release from the growth cone, probably acting at the axon terminal. These data indicate that GABA is secreted from axons during a stage of neuronal development when GABA is excitatory, and that neuromodulators could alter GABA release from the growing axon, potentially enabling other developing neurons of different transmitter phenotype to modulate the early actions of GABA. PMID:10718743

  3. Measurements of growth cone adhesion to culture surfaces by micromanipulation

    PubMed Central

    1994-01-01

    Neurons were grown on plastic surfaces that were untreated, or treated with polylysine, laminin, or L1 and their growth cones were detached from their culture surface by applying known forces with calibrated glass needles. This detachment force was taken as a measure of the force of adhesion of the growth cone. We find that on all surfaces, lamellipodial growth cones require significantly greater detachment force than filopodial growth cones, but this differences is, in general, due to the greater area of lamellipodial growth cones compared to filopodial growth cones. That is, the stress (force/unit area) required for detachment was similar for growth cones of lamellipodial and filopodial morphology on all surfaces, with the exception of lamellipodial growth cones on L1-treated surfaces, which had a significantly lower stress of detachment than on other surfaces. Surprisingly, the forces required for detachment (760-3,340 mudynes) were three to 15 times greater than the typical resting axonal tension, the force exerted by advancing growth cones, or the forces of retraction previously measured by essentially the same method. Nor did we observe significant differences in detachment force among growth cones of similar morphology on different culture surfaces, with the exception of lamellipodial growth cones on L1-treated surfaces. These data argue against the differential adhesion mechanism for growth cone guidance preferences in culture. Our micromanipulations revealed that the most mechanically resistant regions of growth cone attachment were confined to quite small regions typically located at the ends of filopodia and lamellipodia. Detached growth cones remained connected to the substratum at these regions by highly elastic retraction fibers. The closeness of contact of growth cones to the substratum as revealed by interference reflection microscopy (IRM) did not correlate with our mechanical measurements of adhesion, suggesting that IRM cannot be used as a

  4. Local Protein Synthesis in Axonal Growth Cones

    PubMed Central

    Šatkauskas, Saulius

    2007-01-01

    While initially thought to be essentially a developmental characteristic observed in artificial in vitro models, local protein synthesis in growth cones has been described in the adult, and more interestingly, during nerve regeneration. This emerging field is under intense investigation, revealing new functions of localized protein synthesis that include axon guidance, growth cone adaptation and sensitivity modulation at intermediate targets or axon regeneration. Here, we will review these functions and provide a short survey of the current knowledge on mechanisms of mRNA transport and regulation of localized protein synthesis. In addition, we will consider what lessons can be learned from localized protein synthesis in dendrites and what developments can be expected next in the field. This latter question relates to the crucial point of which technical strategy to adopt for an ideal and pertinent analysis of the phenomenon. PMID:19262143

  5. Nano-scale Topographical Studies on the Growth Cones of Nerve Cells using AFM

    NASA Astrophysics Data System (ADS)

    Durkaya, Goksel; Zhong, Lei; Rehder, Vincent; Dietz, Nikolaus

    2009-11-01

    Nerve cells are the fundamental units which are responsible for intercommunication within the nervous system. The neurites, fibrous cable-like extensions for information delivery, of nerve cells are tipped by highly motile sensory structures known as the growth cones which execute important functions; neural construction, decision making and navigation during development and regeneration of the nervous system. The highly dynamic subcomponents of the growth cones are important in neural activity. Atomic Force Microscopy (AFM) is the most powerful microscopy technique which is capable of imaging without conductivity constraint and in liquid media. AFM providing nano-scale topographical information on biological structures is also informative on the physical properties such as: elasticity, adhesion, and softness. This contribution focuses on AFM analysis of the growth cones of the nerve cells removed from the buccal ganglion of Helisoma trivolvis. The results of nano-scale topography and softness analysis on growth cone central domain, filopodia and overlying lamellopodium (veil) are presented. The subcomponents of the growth cones of different nerve cells are compared to each other. The results of the analysis are linked to the mechanical properties and internal molecular density distribution of the growth cones.

  6. 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

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

    PubMed

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

    2016-06-01

    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.

  8. 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

  9. Integrin-linked kinase regulates oligodendrocyte cytoskeleton, growth cone, and adhesion dynamics.

    PubMed

    Michalski, John-Paul; Cummings, Sarah E; O'Meara, Ryan W; Kothary, Rashmi

    2016-02-01

    motility rendered less dynamic. Together, our work helps reconcile the phenotypic discrepancy between ILK loss in vitro and in vivo, informs on the oligodendrocyte's growth cone, and ascribes a role for ILK in growth cone dynamics.

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

    PubMed

    Lowery, Laura Anne; Van Vactor, David

    2009-05-01

    The central component in the road trip of axon guidance is the growth cone, a dynamic structure that is 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 contains 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 with spatial bias to translate environmental signals into directional movement. The understanding of the functions and regulation of the vehicle and navigator provides new insights into the cell biology of growth cone guidance.

  11. 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

  12. Cytoskeletal remodeling during growth cone-target interactions

    PubMed Central

    1993-01-01

    Reorganization of the cytoskeleton of neuronal growth cones in response to environmental cues underlies the process of axonal guidance. Most previous studies addressing cytoskeletal changes during growth cone pathfinding have focused on the dynamics of a single cytoskeletal component. We report here an investigation of homophilic growth cone- target interactions between Aplysia bag cell neurons using digitally enhanced video microscopy, which addresses dynamic interactions between actin filaments and microtubules. After physical contact of a growth cone with a physiological target, mechanical coupling occurred after a delay; and then the growth cone exerted forces on and displaced the target object. Subsequent to coupling, F-actin accumulation was observed at the target contact zone, followed by preferential microtubule extension to the same site. After successful target interactions, growth cones typically moved off highly adhesive poly-L- lysine substrates into native target cell surfaces. These events were associated with modulation of both the direction and rate of neurite outgrowth: growth cone migration was typically reoriented to a trajectory along the target interaction axis and rates of advance increased by about one order of magnitude. Directed microtubule movements toward the contact site appeared to be F-actin dependent as target site-specific microtubule extension and bundling could be reversibly randomized by micromolar levels of cytochalasin B in a characteristic manner. Our results suggest that target contacts can induce focal F-actin assembly and reorganization which, in turn, guides target site-directed microtubule redistribution. PMID:8509456

  13. Coupled local translation and degradation regulate growth cone collapse

    PubMed Central

    Deglincerti, Alessia; Colak, Dilek; Hengst, Ulrich; Liu, Yaobin; Xu, Guoqiang; Jaffrey, Samie R.

    2015-01-01

    Local translation mediates axonal responses to Semaphorin3A (Sema3A) and other guidance cues. However, only a subset of the axonal proteome is locally synthesized, while most proteins are trafficked from the soma. The reason why only specific proteins are locally synthesized is unknown. Here we show that local protein synthesis and degradation are linked events in growth cones. We find that growth cones exhibit high levels of ubiquitination and that local signaling pathways trigger the ubiquitination and degradation of RhoA, a mediator of Sema3A-induced growth cone collapse. Inhibition of RhoA degradation is sufficient to remove the protein-synthesis requirement for Sema3A-induced growth cone collapse. In addition to RhoA, we find that locally translated proteins are the main targets of the ubiquitin-proteasome system in growth cones. Thus, local protein degradation is a major feature of growth cones and creates a requirement for local translation to replenish proteins needed to maintain growth cone responses. PMID:25901863

  14. Cinder cone growth modeled after Northeast crater, Mount Etna, Sicily

    NASA Technical Reports Server (NTRS)

    Mcgetchin, T. R.; Settle, M.; Chouet, B. A.

    1974-01-01

    The structure, physical properties of ejecta, ballistics, and growth of Northeast crater, a young pyroclastic cone that originated in 1911 near the summit of Mount Etna, Sicily, were studied in order to form a model of volcano cinder cone growth. Four stages of growth were discerned: (1) a simple cone; (2) a cone with an outward-dipping talus slope; (3) destruction of rounded rim by the inward migration of the upper edge of the talus pile; and (4) extension of limits of talus pile beyond the ballistic limit of ejecta trajectories. The model is used to predict the features of lunar and Martian cones, assuming that they erupted under conditions qualitatively similar to Etna's Northeast crater.

  15. 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

  16. ERM proteins regulate growth cone responses to Sema3A

    PubMed Central

    Mintz, C. David; Carcea, Ioana; McNickle, Daniel G.; Dickson, Tracey C.; Ge, Yongchao; Salton, Stephen R.J.; Benson, Deanna L.

    2008-01-01

    Axonal growth cones initiate and sustain directed growth in response to cues in their environment. A variety of events such as receptor internalization, kinase activation, and actin rearrangement can be stimulated by guidance cues and are essential for mediating targeted growth cone behavior. Surprisingly little is known about how such disparate actions are coordinated. Our data suggest that ezrin, radixin, and moesin (ERMs), a family of highly homologous, multifunctional proteins may be able to coordinate growth cone responses to the guidance cue, Sema3A. We show that active ERMs concentrate asymmetrically in neocortical growth cones, are rapidly and transiently inactivated by Sema3A, and are required for Sema3A-mediated growth cone collapse and guidance. The FERM domain of active ERMs regulates internalization of the Sema3A receptor, Npn1 and its co-receptor, L1CAM, while the ERM C-terminal domain binds and caps F-actin. Our data support a model in which ERMs can coordinate membrane and actin dynamics in response to Sema3A. PMID:18651636

  17. 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.

  18. 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.

  19. Neuronal growth cones respond to laser-induced axonal damage

    PubMed Central

    Wu, Tao; Mohanty, Samarendra; Gomez-Godinez, Veronica; Shi, Linda Z.; Liaw, Lih-Huei; Miotke, Jill; Meyer, Ronald L.; Berns, Michael W.

    2012-01-01

    Although it is well known that damage to neurons results in release of substances that inhibit axonal growth, release of chemical signals from damaged axons that attract axon growth cones has not been observed. In this study, a 532 nm 12 ns laser was focused to a diffraction-limited spot to produce site-specific damage to single goldfish axons in vitro. The axons underwent a localized decrease in thickness (‘thinning’) within seconds. Analysis by fluorescence and transmission electron microscopy indicated that there was no gross rupture of the cell membrane. Mitochondrial transport along the axonal cytoskeleton immediately stopped at the damage site, but recovered over several minutes. Within seconds of damage nearby growth cones extended filopodia towards the injury and were often observed to contact the damaged site. Turning of the growth cone towards the injured axon also was observed. Repair of the laser-induced damage was evidenced by recovery of the axon thickness as well as restoration of mitochondrial movement. We describe a new process of growth cone response to damaged axons. This has been possible through the interface of optics (laser subcellular surgery), fluorescence and electron microscopy, and a goldfish retinal ganglion cell culture model. PMID:21831892

  20. 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.

  1. A quantitative study of growth cone filopodial extension.

    PubMed

    Argiro, V; Bunge, M B; Johnson, M I

    1985-01-01

    The extension of filopodia from growth cones of regenerating neurites from rat superior cervical ganglion neurons in tissue culture was studied. Cultures were grown on a thin layer of fibrous collagen and maintained in a medium containing serum and nerve growth factor. Time-lapse cinematography and computer-assisted morphometry were used to observe and measure the kinetics of extension of individual filopodia. Filopodia extended from the growth cone margin, trailing neurite, or from each other. Frequently, extension was preceded by the appearance at the cone margin of a nodule of cytoplasm which appeared dense in phase-contrast optics. Branch points between adjacent extending filopodia remained fixed with respect to the growth cone while the filopodia lengthened. The rate of extension was maximum just after initiation (0.12 +/- 0.4 micron/sec; mean +/- SD; n = 36) and declined thereafter until the filopodium collapsed. This initial rate of extension was directly correlated with the eventual length of the filopodium (r = 0.67). Filopodia of growth cones arising from embryonic neurons exhibited higher initial extension rates (range: 0.07 to 0.20 micron/sec; mean = 0.13 micron/sec) than those of postnatal neurons (range: 0.01 to 0.13 micron/sec; mean = 0.09 micron/sec). These data are discussed in relation to a model proposed by Tilney and Inoue [1982] for the extension, by distal addition of G-actin to growing filaments, of another type of elongating process filled with microfilaments, the acrosomal process of Thyone sperm.

  2. 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

  3. 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

  4. 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. PMID:26105207

  5. The role of cytoskeleton in organizing growth cones: a microfilament- associated growth cone component depends upon microtubules for its localization

    PubMed Central

    1989-01-01

    We are interested in the relationship between the cytoskeleton and the organization of polarized cell morphology. We show here that the growth cones of hippocampal neurons in culture are specifically stained by a monoclonal antibody called 13H9. In other systems, the antigen recognized by 13H9 is associated with marginal bands of chicken erythrocytes and shows properties of both microtubule-and microfilament- associated proteins (Birgbauer, E., and F. Solomon. 1989 J. Cell Biol. 109:1609-1620). This dual nature is manifest in hippocampal neurons as well. At early stages after plating, the antibody stains the circumferential lamellipodia that mediate initial cell spreading. As processes emerge, 13H9 staining is heavily concentrated in the distal regions of growth cones, particularly in lamellipodial fans. In these cells, the 13H9 staining is complementary to the localization of assembled microtubules. It colocalizes partially, but not entirely, with phalloidin staining of assembled actin. Incubation with nocodazole rapidly induces microtubule depolymerization, which proceeds in the distal-to-proximal direction in the processes. At the same time, a rapid and dramatic redistribution of the 13H9 staining occurs; it delocalizes along the axon shaft, becoming clearly distinct from the phalloidin staining and always remaining distal to the receding front of assembled microtubules. After longer times without assembled microtubules, no staining of 13H9 can be detected. Removal of the nocodazole allows the microtubules to reform, in an ordered proximal-to- distal fashion. The 13H9 immunoreactivity also reappears, but only in the growth cones, not in any intermediate positions along the axon, and only after the reformation of microtubules is complete. The results indicate that the antigen recognized by 13H9 is highly concentrated in growth cones, closely associated with polymerized actin, and that its proper localization depends upon intact microtubules. PMID:2677024

  6. Actions of cytochalasins on the organization of actin filaments and microtubules in a neuronal growth cone

    PubMed Central

    1988-01-01

    Actions of cytochalasin B (CB) on cytoskeletons and motility of growth cones from cultured Aplysia neurons were studied using a rapid flow perfusion chamber and digital video light microscopy. Living growth cones were observed using differential interference contrast optics and were also fixed at various time points to assay actin filament (F- actin) and microtubule distributions. Treatment with CB reversibly blocked motility and eliminated most of the phalloidin-stainable F- actin from the leading lamella. The loss of F-actin was nearly complete within 2-3 min of CB application and was largely reversed within 5-6 min of CB removal. The loss and recovery of F-actin were found to occur with a very distinctive spatial organization. Within 20-30 s of CB application, F-actin networks receded from the entire peripheral margin of the lamella forming a band devoid of F-actin. This band widened as F- actin receded at rates of 3-6 microns/min. Upon removal of CB, F-actin began to reappear within 20-30 s. The initial reappearance of F-actin took two forms: a coarse isotropic matrix of F-actin bundles throughout the lamella, and a denser matrix along the peripheral margin. The denser peripheral matrix then expanded in width, extending centrally to replace the coarse matrix at rates again between 3-6 microns/min. These results suggest that actin normally polymerizes at the leading edge and then flows rearward at a rate between 3-6 microns/min. CB treatment was also observed to alter the distribution of microtubules, assayed by antitubulin antibody staining. Normally, microtubules are restricted to the neurite shaft and a central growth cone domain. Within approximately 5 min after CB application, however, microtubules began extending into the lamellar region, often reaching the peripheral margin. Upon removal of CB, the microtubules were restored to their former central localization. The timing of these microtubule redistributions is consistent with their being secondary to

  7. 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

  8. Uptake and release of [3H]GABA by growth cones isolated from neonatal rat brain.

    PubMed

    Gordon-Weeks, P R; Lockerbie, R O; Pearce, B R

    1984-11-23

    A subcellular fraction highly enriched in neuronal growth cones was isolated from 5-day-old rat forebrain by a recently described method. The growth cone fraction was shown to have a sodium- and temperature-dependent, high-affinity (Km = 4.4 microM) uptake system for [3H]GABA. Electron microscopic autoradiography confirmed that this uptake was into growth cones since only these structures were heavily labelled with silver grains. High potassium induced the release of newly accumulated [3H]GABA from the growth cone fraction, about half of which was Ca2+-dependent. The presence of uptake and release systems for GABA in growth cones may simply reflect the development of growth cones into nerve terminals. Alternatively, these observations may indicate a role for neurotransmitter release in synaptogenesis.

  9. Use of scanning ion conductance microscopy to guide and redirect neuronal growth cones.

    PubMed

    Pellegrino, Mario; Orsini, Paolo; De Gregorio, Francesca

    2009-07-01

    Scanning ion conductance microscopy has been applied to neuronal growth cones of the leech either to image or to stimulate them. Growth cone advance was recorded in non-contact mode using a 2% ion current decrease criterion for pipette-membrane distance control. We demonstrate effective growth cone remodelling using a 5% criterion (near-scanning). Recurrent line near-scanning aligned growth cone processes along the scan line. The new membrane protrusions, marked by DiI, started a few minutes after scanning onset and progressively grew in thickness. Using scanning patterns suitable for connecting distinct growth cones, new links were consistently developed. Although the underlying mechanism is still a matter for investigation, a mechanical perturbation produced by the moving probe appeared to induce the process formation. Thanks to its deterministic and interactive features, this novel approach to guiding growth cones is a promising way to develop networks of identified neurons as well as link them with artificial structures. PMID:19447298

  10. Integrins and cAMP mediate netrin-induced growth cone collapse

    PubMed Central

    Lemons, M.L.; Abanto, M.L.; Dambrouskas, N.; Clements, C.C.; DeLoughery, Z.; Garozzo, J.; Condic, M.L.

    2013-01-01

    Growth cones integrate a remarkably complex concert of chemical cues to guide axons to their appropriate destinations. Recent work suggests that integrins contribute to axon guidance by interacting with a wide range of extracellular molecules including axon guidance molecules, by mechanisms that are not fully understood. Here, we describe an interaction between integrins and netrin-1 in growth cones that contributes to growth cone collapse. Our data show that netrin-1 causes growth cone collapse in a substratum-specific manner and is integrin-dependent. Netrin-1 causes collapse of cultured chick dorsal root ganglion (DRG) growth cones extending on high levels of laminin-1 (LN) but not growth cones extending on low levels of LN or on fibronectin. Blocking integrin function significantly decreases netrin-induced growth cone collapse on high LN. Netrin-1 and integrins interact on growth cones; netrin-1 causes integrin activation, a conformational shift to a high ligand-affinity state. Netrin-1 directly binds to integrin α3 and α6 peptides, further suggesting a netrin-integrin interaction. Interestingly, our data reveal netrin-1 increases growth cone levels of cAMP in a substratum-specific manner and that netrin-induced growth cone collapse requires increased cAMP in combination with integrin activation. Manipulations that either decrease cAMP levels or integrin activation block netrin-induced collapse. These results imply a common mechanism for growth cone collapse and novel interactions between integrins, netrin-1 and cAMP that contribute to growth cone guidance. PMID:24001590

  11. 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.

  12. Isolation and partial characterisation of neuronal growth cones from neonatal rat forebrain.

    PubMed

    Gordon-Weeks, P R; Lockerbie, R O

    1984-09-01

    We have devised a method for the isolation of viable neuronal growth cones from neonatal rat forebrain. The method involves differential and density gradient centrifugation and exploits the relatively low buoyant density (approximately 1.018 g/cm3) of growth cones. There are no known biochemical markers for growth cones and it was necessary therefore to monitor for their presence during the isolation using transmission electron microscopy. Several criteria were used to identify isolated growth cones including the presence of filopodia, an extensive system of branching, tubular smooth endoplasmic reticulum and a region rich in microfilaments subjacent to the plasma membrane. These morphological features are similar to those of growth cones identified unequivocally in intact developing brain and in tissue culture. Electron microscopical analysis showed that greater than 90% of membrane-bound, identifiable objects in one fraction were growth cones by these criteria. The major contaminant consisted of membrane sacs and vesicles of unidentified origin. There were only small amounts of isolated rough endoplasmic reticulum and mitochondria. Isolated growth cones were roughly spherical in shape with a diameter of 1.9 +/- 0.5 micron (mean +/- 1 SD). They usually contained mitochondria, large granular vesicles and small vesicles, and occasionally contained coated vesicles, lysosomes, lamellar bodies and multivesicular bodies, and only very rarely, intermediate filaments. Occasionally, growth cones had rudimentary synapses on them. The viability of isolated growth cones was investigated by observing their behaviour in short-term culture. After a few hours in culture on poly-D-lysine-coated coverslips, growth cones flattened down and extended filopodia-like processes. This behaviour was inhibited by cytochalasin B and reversibly by cold (4 degrees C). We conclude that physiologically active growth cones can be isolated rapidly and in large numbers by the method described here.

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

    PubMed Central

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

    2015-01-01

    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. DOI: http://dx.doi.org/10.7554/eLife.10721.001 PMID:26512889

  14. 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.

  15. Subcellular Profiling Reveals Distinct and Developmentally Regulated Repertoire of Growth Cone mRNAs

    PubMed Central

    Zivraj, Krishna H.; Tung, Yi Chun Loraine; Piper, Michael; Gumy, Laura; Fawcett, James W.; Yeo, Giles S. H.; Holt, Christine E.

    2013-01-01

    Cue-directed axon guidance depends partly on local translation in growth cones. Many mRNA transcripts are known to reside in developing axons, yet little is known about their subcellular distribution or, specifically, which transcripts are in growth cones. Here laser capture microdissection (LCM) was used to isolate the growth cones of retinal ganglion cell (RGC) axons of two vertebrate species, mouse and Xenopus, coupled with unbiased genomewide microarray profiling. An unexpectedly large pool of mRNAs defined predominant pathways in protein synthesis, oxidative phosphorylation, cancer, neurological disease, and signaling. Comparative profiling of “young” (pathfinding) versus “old” (target-arriving) Xenopus growth cones revealed that the number and complexity of transcripts increases dramatically with age. Many presynaptic protein mRNAs are present exclusively in old growth cones, suggesting that functionally related sets of mRNAs are targeted to growth cones in a developmentally regulated way. Remarkably, a subset of mRNAs was significantly enriched in the growth cone compared with the axon compartment, indicating that mechanisms exist to localize mRNAs selectively to the growth cone. Furthermore, some receptor transcripts (e.g., EphB4), present exclusively in old growth cones, were equally abundant in young and old cell bodies, indicating that RNA trafficking from the soma is developmentally regulated. Our findings show that the mRNA repertoire in growth cones is regulated dynamically with age and suggest that mRNA localization is tailored to match the functional demands of the growing axon tip as it transforms into the presynaptic terminal. PMID:21084603

  16. Hepatocyte growth factor is a potent angiogenic factor which stimulates endothelial cell motility and growth

    PubMed Central

    1992-01-01

    Hepatocyte Growth Factor (HGF, also known as Scatter Factor) is a powerful mitogen or motility factor in different cells, acting through the tyrosine kinase receptor encoded by the MET protooncogene. Endothelial cells express the MET gene and expose at the cell surface the mature protein (p190MET) made of a 50 kD (alpha) subunit disulfide linked to a 145-kD (beta) subunit. HGF binding to endothelial cells identifies two sites with different affinities. The higher affinity binding site (Kd = 0.35 nM) corresponds to the p190MET receptor. Sub- nanomolar concentrations of HGF, but not of a recombinant inactive precursor, stimulate the receptor kinase activity, cell proliferation and motility. HGF induces repairs of a wound in endothelial cell monolayer. HGF stimulates the scatter of endothelial cells grown on three-dimensional collagen gels, inducing an elongated phenotype. In the rabbit cornea, highly purified HGF promotes neovascularization at sub-nanomolar concentrations. HGF lacks activities related to hemostasis-thrombosis, inflammation and endothelial cells accessory functions. These data show that HGF is an in vivo potent angiogenic factor and in vitro induces endothelial cells to proliferate and migrate. PMID:1383237

  17. Collapsin response mediator protein 4 regulates growth cone dynamics through the actin and microtubule cytoskeleton.

    PubMed

    Khazaei, Mohamad R; Girouard, Marie-Pier; Alchini, Ricardo; Ong Tone, Stephan; Shimada, Tadayuki; Bechstedt, Susanne; Cowan, Mitra; Guillet, Dominique; Wiseman, Paul W; Brouhard, Gary; Cloutier, Jean Francois; Fournier, Alyson E

    2014-10-24

    Coordinated control of the growth cone cytoskeleton underlies axon extension and guidance. Members of the collapsin response mediator protein (CRMP) family of cytosolic phosphoproteins regulate the microtubule and actin cytoskeleton, but their roles in regulating growth cone dynamics remain largely unexplored. Here, we examine how CRMP4 regulates the growth cone cytoskeleton. Hippocampal neurons from CRMP4-/- mice exhibited a selective decrease in axon extension and reduced growth cone area, whereas overexpression of CRMP4 enhanced the formation and length of growth cone filopodia. Biochemically, CRMP4 can impact both microtubule assembly and F-actin bundling in vitro. Through a structure function analysis of CRMP4, we found that the effects of CRMP4 on axon growth and growth cone morphology were dependent on microtubule assembly, whereas filopodial extension relied on actin bundling. Intriguingly, anterograde movement of EB3 comets, which track microtubule protrusion, slowed significantly in neurons derived from CRMP4-/- mice, and rescue of microtubule dynamics required CRMP4 activity toward both the actin and microtubule cytoskeleton. Together, this study identified a dual role for CRMP4 in regulating the actin and microtubule growth cone cytoskeleton. PMID:25225289

  18. Morphology and Nanomechanics of Sensory Neurons Growth Cones following Peripheral Nerve Injury

    PubMed Central

    Szabo, Vivien; Végh, Attila-Gergely; Lucas, Olivier; Cloitre, Thierry; Scamps, Frédérique; Gergely, Csilla

    2013-01-01

    A prior peripheral nerve injury in vivo, promotes a rapid elongated mode of sensory neurons neurite regrowth in vitro. This in vitro model of conditioned axotomy allows analysis of the cellular and molecular mechanisms leading to an improved neurite re-growth. Our differential interference contrast microscopy and immunocytochemistry results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar sensory neurons from mice dorsal root ganglia sensory neurons but promoted the appearance of larger neurites and growth cones. Using atomic force microscopy on live neurons, we investigated whether membrane mechanical properties of growth cones of axotomized neurons were modified following sciatic nerve injury. Our data revealed that neurons having a regenerative growth were characterized by softer growth cones, compared to control neurons. The increase of the growth cone membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins. PMID:23418549

  19. Evolution of cell motility in an individual-based model of tumour growth

    PubMed Central

    Gerlee, P.; Anderson, A.R.A.

    2009-01-01

    Tumour invasion is driven by proliferation and importantly migration into the surrounding tissue. Cancer cell motility is also critical in the formation of metastases and is therefore a fundamental issue in cancer research. In this paper we investigate the emergence of cancer cell motility in an evolving tumour population using an individual-based modelling approach. In this model of tumour growth each cell is equipped with a microenvironment response network that determines the behaviour or phenotype of the cell based on the local environment. The response network is modelled using a feed-forward neural network, which is subject to mutations when the cells divide. With this model we have investigated the impact of the micro-environment on the emergence of a motile invasive phenotype. The results show that when a motile phenotype emerges the dynamics of the model are radically changed and we observe faster growing tumours exhibiting diffuse morphologies. Further we observe that the emergence of a motile subclone can occur in a wide range of micro-environmental growth conditions. Iterated simulations showed that in identical growth conditions the evolutionary dynamics either converge to a proliferating or migratory phenotype, which suggests that the introduction of cell motility into the model changes the shape of fitness landscape on which the cancer cell population evolves and that it now contains several local maxima. This could have important implications for cancer treatments which focus on the gene level, as our results show that several distinct genotypes and critically distinct phenotypes can emerge and become dominant in the same micro-environment. PMID:19285513

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

    PubMed

    Lewis, Wesley R; Malarkey, Erik B; Tritschler, Douglas; Bower, Raqual; Pasek, Raymond C; Porath, Jonathan D; Birket, Susan E; Saunier, Sophie; Antignac, Corinne; Knowles, Michael R; Leigh, Margaret W; Zariwala, Maimoona A; Challa, Anil K; Kesterson, Robert A; Rowe, Steven M; Drummond, Iain A; Parant, John M; Hildebrandt, Friedhelm; Porter, Mary E; Yoder, Bradley K; Berbari, Nicolas F

    2016-07-01

    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 in

  1. 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

  2. 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

  3. Absence of persistent spreading, branching, and adhesion in GAP-43- depleted growth cones

    PubMed Central

    1995-01-01

    The growth-associated protein GAP-43 is a major protein kinase C substrate of growth cones and developing nerve terminals. In the growth cone, it accumulates near the plasma membrane, where it associates with the cortical cytoskeleton and membranes. The role of GAP-43 in neurite outgrowth is not yet clear, but recent findings suggest that it may be a crucial competence factor in this process. To define the role of GAP- 43 in growth cone activity, we have analyzed neurite outgrowth and growth cone activity in primary sensory neurons depleted of GAP-43 by a specific antisense oligonucleotide procedure. Under optimal culture conditions, but in the absence of GAP-43, growth cones adhered poorly, displayed highly dynamic but unstable lamellar extensions, and were strikingly devoid of local f-actin concentrations. Upon stimulation, they failed to produce NGF-induced spreading or insulin-like growth factor-1-induced branching, whereas growth factor-induced phosphotyrosine immunoreactivity and acceleration of neurite elongation were not impaired. Unlike their GAP-43-expressing counterparts, they readily retracted when exposed to inhibitory central nervous system myelin-derived liposomes. Frequency and extent of induced retraction were attenuated by NGF. Our results indicate that GAP-43 can promote f- actin accumulation, evoked morphogenic activity, and resistance to retraction of the growth cone, suggesting that it may promote regulated neurite outgrowth during development and regeneration. PMID:7860637

  4. Signaling Mechanisms Underlying Slit2-Induced Collapse of Xenopus Retinal Growth Cones

    PubMed Central

    Piper, Michael; Anderson, Richard; Dwivedy, Asha; Weinl, Christine; van Horck, Francis; Leung, Kin Mei; Cogill, Emily; Holt, Christine

    2013-01-01

    Summary Slits mediate multiple axon guidance decisions, but the mechanisms underlying the responses of growth cones to these cues remain poorly defined. We show here that collapse induced by Slit2-conditioned medium (Slit2-CM) in Xenopus retinal growth cones requires local protein synthesis (PS) and endocytosis. Slit2-CM elicits rapid activation of translation regulators and MAP kinases in growth cones, and inhibition of MAPKs or disruption of heparan sulfate blocks Slit2-CM-induced PS and repulsion. Interestingly, Slit2-CM causes a fast PS-dependent decrease in cytoskeletal F-actin concomitant with a PS-dependent increase in the actin-depolymerizing protein cofilin. Our findings reveal an unexpected link between Slit2 and cofilin in growth cones and suggest that local translation of actin regulatory proteins contributes to repulsion. PMID:16423696

  5. The alpha-tubulin of the growth cone is predominantly in the tyrosinated form.

    PubMed

    Gordon-Weeks, P R; Lang, R D

    1988-07-01

    Growth cone cytoskeletons were prepared by detergent extraction of growth cones isolated from neonatal rat forebrain by the method of Gordon-Weeks and Lockerbie (Neuroscience, 13 (1984) 119-136). SDS-PAGE analysis of growth cone cytoskeletons revealed the presence of several major bands, identified by their mobility as actin (43 kDa Mr), myosin heavy chain (195 kDa Mr), spectrin (235 and 240 kDa Mr), and tubulin (51-54 kDa Mr). The identity of these proteins was confirmed by immunoblot analysis using specific antibodies to these proteins which further revealed that the predominant form of alpha-tubulin in the growth cone cytoskeleton and in the soluble pool of tubulin is tyrosinated at the C-terminal.

  6. 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

  7. The biosurfactant viscosin produced by Pseudomonas fluorescens SBW25 aids spreading motility and plant growth promotion.

    PubMed

    Alsohim, Abdullah S; Taylor, Tiffany B; Barrett, Glyn A; Gallie, Jenna; Zhang, Xue-Xian; Altamirano-Junqueira, Astrid E; Johnson, Louise J; Rainey, Paul B; Jackson, Robert W

    2014-07-01

    Food security depends on enhancing production and reducing loss to pests and pathogens. A promising alternative to agrochemicals is the use of plant growth-promoting rhizobacteria (PGPR), which are commonly associated with many, if not all, plant species. However, exploiting the benefits of PGPRs requires knowledge of bacterial function and an in-depth understanding of plant-bacteria associations. Motility is important for colonization efficiency and microbial fitness in the plant environment, but the mechanisms employed by bacteria on and around plants are not well understood. We describe and investigate an atypical mode of motility in Pseudomonas fluorescens SBW25 that was revealed only after flagellum production was eliminated by deletion of the master regulator fleQ. Our results suggest that this 'spidery spreading' is a type of surface motility. Transposon mutagenesis of SBW25ΔfleQ (SBW25Q) produced mutants, defective in viscosin production, and surface spreading was also abolished. Genetic analysis indicated growth-dependency, production of viscosin, and several potential regulatory and secretory systems involved in the spidery spreading phenotype. Moreover, viscosin both increases efficiency of surface spreading over the plant root and protects germinating seedlings in soil infected with the plant pathogen Pythium. Thus, viscosin could be a useful target for biotechnological development of plant growth promotion agents. PMID:24684210

  8. The biosurfactant viscosin produced by Pseudomonas fluorescens SBW25 aids spreading motility and plant growth promotion.

    PubMed

    Alsohim, Abdullah S; Taylor, Tiffany B; Barrett, Glyn A; Gallie, Jenna; Zhang, Xue-Xian; Altamirano-Junqueira, Astrid E; Johnson, Louise J; Rainey, Paul B; Jackson, Robert W

    2014-07-01

    Food security depends on enhancing production and reducing loss to pests and pathogens. A promising alternative to agrochemicals is the use of plant growth-promoting rhizobacteria (PGPR), which are commonly associated with many, if not all, plant species. However, exploiting the benefits of PGPRs requires knowledge of bacterial function and an in-depth understanding of plant-bacteria associations. Motility is important for colonization efficiency and microbial fitness in the plant environment, but the mechanisms employed by bacteria on and around plants are not well understood. We describe and investigate an atypical mode of motility in Pseudomonas fluorescens SBW25 that was revealed only after flagellum production was eliminated by deletion of the master regulator fleQ. Our results suggest that this 'spidery spreading' is a type of surface motility. Transposon mutagenesis of SBW25ΔfleQ (SBW25Q) produced mutants, defective in viscosin production, and surface spreading was also abolished. Genetic analysis indicated growth-dependency, production of viscosin, and several potential regulatory and secretory systems involved in the spidery spreading phenotype. Moreover, viscosin both increases efficiency of surface spreading over the plant root and protects germinating seedlings in soil infected with the plant pathogen Pythium. Thus, viscosin could be a useful target for biotechnological development of plant growth promotion agents.

  9. 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.

  10. Tyrosine kinase inhibitor STI571 enhances thyroid cancer cell motile response to Hepatocyte Growth Factor.

    PubMed

    Frasca, F; Vigneri, P; Vella, V; Vigneri, R; Wang, J Y

    2001-06-28

    The Hepatocyte Growth Factor (HGF) and its receptor Met are physiological regulators of cell migration. HGF and Met have also been implicated in tumor progression and metastasis. We show here that the tyrosine kinase inhibitor STI571 has a stimulatory effect on HGF-induced migration and branching morphogenesis in thyroid cancer but not in primary or immortalized thyroid epithelial cells. These stimulatory effects of STI571 are observed at a concentration that is clinically relevant. The STI571-enhanced motile response can be correlated with an increase in the Met receptor tyrosine phosphorylation as well as ERK and Akt activation by HGF. Interestingly, one of the targets of STI571, namely the c-Abl tyrosine kinase, is activated by HGF and is recruited at the migrating edge of thyroid cancer cells. These data suggests that c-Abl and/or STI571-inhibited tyrosine kinases can negatively regulate the Met receptor to restrain the motile response in thyroid cancer cells.

  11. IDENTIFICATION OF A DEVELOPMENTALLY-REGULATED PATHWAY OF MEMBRANE RETRIEVAL IN NEURONAL GROWTH CONES

    PubMed Central

    Bonanomi, Dario; Fornasiero, Eugenio F.; Valdez, Gregorio; Halegoua, Simon; Benfenati, Fabio; Menegon, Andrea; Valtorta, Flavia

    2009-01-01

    During axon navigation and upon target recognition the growth cone plasma membrane is constantly reconfigured as a result of changes in cytoskeletal and membrane dynamics. The identity and regulation of the membrane pathway(s) participating in remodeling of the growth cone surface remain elusive. Here, we identify a constitutive, high capacity plasma membrane recycling activity in the axonal growth cones which is mediated by a novel bulk endocytic pathway mechanistically related to macropinocytosis. This pathway, involving large compartments distributed at sites of intense actin-based membrane ruffling, requires phosphatidylinositol 3-kinase activity, the small GTPase Rac1 and the pinocytic chaperone Pincher. At early developmental stages, the synaptic vesicle and classical endosomal recycling pathways do not participate in the rapid retrieval of the growth cone plasma membrane. At later stages, during the onset of synaptogenesis, an intrinsic program of maturation leads to downregulation of basal bulk endocytosis and the emergence of depolarization-induced synaptic vesicle exo-endocytosis. We propose that the control of bulk membrane retrieval contributes to the homeostatic regulation of the axonal plasma membrane and growth cone remodeling during axonal outgrowth. In addition, we suggest that the downregulation of bulk endocytosis during synaptogenesis might contribute to the preservation of synaptic vesicle specificity. PMID:18940911

  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. Regulation of ECM degradation and axon guidance by growth cone invadosomes

    PubMed Central

    Santiago-Medina, Miguel; Gregus, Kelly A.; Nichol, Robert H.; O'Toole, Sean M.; Gomez, Timothy M.

    2015-01-01

    Invadopodia and podosomes, collectively referred to as invadosomes, are F-actin-rich basal protrusions of cells that provide sites of attachment to and degradation of the extracellular matrix. Invadosomes promote the invasion of cells, ranging from metastatic cancer cells to immune cells, into tissue. Here, we show that neuronal growth cones form protrusions that share molecular, structural and functional characteristics of invadosomes. Growth cones from all neuron types and species examined, including a variety of human neurons, form invadosomes both in vitro and in vivo. Growth cone invadosomes contain dynamic F-actin and several actin regulatory proteins, as well as Tks5 and matrix metalloproteinases, which locally degrade the matrix. When viewed using three-dimensional super-resolution microscopy, F-actin foci often extended together with microtubules within orthogonal protrusions emanating from the growth cone central domain. Finally, inhibiting the function of Tks5 both reduced matrix degradation in vitro and disrupted motoneuron axons from exiting the spinal cord and extending into the periphery. Taken together, our results suggest that growth cones use invadosomes to target protease activity during axon guidance through tissues. PMID:25564649

  14. 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

  15. 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

  16. Molecular Characterization of Toxoplasma gondii Formin 3, an Actin Nucleator Dispensable for Tachyzoite Growth and Motility

    PubMed Central

    Daher, Wassim; Klages, Natacha; Carlier, Marie-France

    2012-01-01

    Toxoplasma gondii belongs to the phylum Apicomplexa, a group of obligate intracellular parasites that rely on gliding motility to enter host cells. Drugs interfering with the actin cytoskeleton block parasite motility, host cell invasion, and egress from infected cells. Myosin A, profilin, formin 1, formin 2, and actin-depolymerizing factor have all been implicated in parasite motility, yet little is known regarding the importance of actin polymerization and other myosins for the remaining steps of the parasite lytic cycle. Here we establish that T. gondii formin 3 (TgFRM3), a newly described formin homology 2 domain (FH2)-containing protein, binds to Toxoplasma actin and nucleates rabbit actin assembly in vitro. TgFRM3 expressed as a transgene exhibits a patchy localization at several distinct structures within the parasite. Disruption of the TgFRM3 gene by double homologous recombination in a ku80-ko strain reveals no vital function for tachyzoite propagation in vitro, which is consistent with its weak level of expression in this life stage. Conditional stabilization of truncated forms of TgFRM3 suggests that different regions of the molecule contribute to distinct localizations. Moreover, expression of TgFRM3 lacking the C-terminal domain severely affects parasite growth and replication. This work provides a first insight into how this specialized formin, restricted to the group of coccidia, completes its actin-nucleating activity. PMID:22210829

  17. 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.

  18. Endocytosis-dependent desensitization and protein synthesis-dependent resensitization in retinal growth cone adaptation.

    PubMed

    Piper, Michael; Salih, Saif; Weinl, Christine; Holt, Christine E; Harris, William A

    2005-02-01

    It has been proposed that growth cones navigating through gradients adapt to baseline concentrations of guidance cues. This adaptation process is poorly understood. Using the collapse assay, we show that adaptation in Xenopus laevis retinal growth cones to the guidance cues Sema3A or netrin-1 involves two processes: a fast, ligand-specific desensitization that occurs within 2 min of exposure and is dependent on endocytosis, and a slower, ligand-specific resensitization, which occurs within 5 min and is dependent upon protein synthesis. These two phases of adaptation allow retinal axons to adjust their range of sensitivity to specific guidance cues.

  19. Endocytosis-dependent desensitization and protein synthesis–dependent resensitization in retinal growth cone adaptation

    PubMed Central

    Piper, Michael; Salih, Saif; Weinl, Christine; Holt, Christine E; Harris, William A

    2013-01-01

    It has been proposed that growth cones navigating through gradients adapt to baseline concentrations of guidance cues. This adaptation process is poorly understood. Using the collapse assay, we show that adaptation in Xenopus laevis retinal growth cones to the guidance cues Sema3A or netrin-1 involves two processes: a fast, ligand-specific desensitization that occurs within 2 min of exposure and is dependent on endocytosis, and a slower, ligand-specific resensitization, which occurs within 5 min and is dependent upon protein synthesis. These two phases of adaptation allow retinal axons to adjust their range of sensitivity to specific guidance cues. PMID:15643427

  20. 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

  1. Differing semaphorin 3A concentrations trigger distinct signaling mechanisms in growth cone collapse.

    PubMed

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

    2012-06-20

    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 neurons. We show that the dependence of growth cone collapse on protein synthesis varies according to Sema3A concentration, from near-total at low concentration (<100 ng/ml) to minimal at high concentration (>625 ng/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, 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.

  2. An isolated growth cone-enriched fraction from developing rat brain has substance P binding sites.

    PubMed

    Lockerbie, R O; Beaujouan, J C; Saffroy, M; Glowinski, J

    1988-05-01

    A fraction enriched in neuronal growth cones isolated from developing rat forebrain was shown to possess binding sites for the substance P analog, Bolton-Hunter substance P [( 125I]BHSP). Specific binding of this ligand reached an equilibrium after 10 min at 20 degrees C, and was reversible and temperature-dependent. Removal of extracellular Na+ did not block but rather augmented [125I]BHSP binding suggesting that the labeled analog was not transported into the growth cone fraction. Scatchard analysis of the binding indicated a single class of non-interacting binding sites in the growth cone fraction (Kd: 257 pM; Bmax: 56 fmol/mg protein). From competition studies using substance P and other tachykinins, their rank order of potency for inhibiting [125I]BHSP binding was SP greater than physalaemin much greater than eledoisin greater than kassinin greater than NKB greater than or equal to NKA. Such order is consistent with the presence of an SP receptor (Neurokinin-1) in the growth cone fraction. The N-terminal fragments of substance P, SP1-7 and SP1-11 free acids, and the C-terminal fragment, SP7-11, were devoid of affinity for the [125I]BHSP binding site. However SP6-11 and SP1-11 methyl esters showed more potency.

  3. The Role of PI(3,4,5)P3 Signaling During Axonal Growth Cone Chemotaxis

    NASA Astrophysics Data System (ADS)

    Henle, Steven J.

    Development of the nervous system is a remarkably complex process that involves the birth of billions of neurons leading to the formation of trillions of synapses. Many biological programs underlie the formation of a functional nervous system. I focused on trying to understand the process by which a newly formed axon navigates a series of signals in the environment that guide it to a synaptic partner. At the tip of the extending neurite is a conical expansion known as the growth cone that primarily is responsible for performing this pathfinding process. In order to do so it senses the environment, and induces a program of intracellular signaling that in turn leads to directed axon extension. My work has focused on understanding this signaling machinery. I have aimed to understand the role the phosphoinositde PI(3,4,5)P3 due to the critical role it plays in amoeboid chemotaxis. I discovered that PI(3,4,5)P3 and its downstream kinase Akt define the leading edge during growth cone chemotaxis and lead to activation of a TRP (Transient Receptor Potential) channel. Furthermore, I found that the PI(3,4,5)P3 phosphatase PTEN appears to be exclusively linked to guiding growth cone migration in response to a gradient of chemorepellent. Taken together my data demonstrate that PI(3,4,5)P3 functions as a key instructive mediator of growth cone chemotaxis.

  4. 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

  5. Growth cone collapse and inhibition of neurite growth by Botulinum neurotoxin C1: a t-SNARE is involved in axonal growth

    PubMed Central

    1996-01-01

    The growth cone is responsible for axonal growth, where membrane expansion is most likely to occur. Several recent reports have suggested that presynaptic proteins are involved in this process; however, the molecular mechanism details are unclear. We suggest that by cleaving a presynaptic protein syntaxin, which is essential in targeting synaptic vesicles as a target SNAP receptor (t-SNARE), neurotoxin C1 of Clostridium botulinum causes growth cone collapse and inhibits axonal growth. Video-enhanced microscopic studies showed (a) that neurotoxin C1 selectively blocked the activity of the central domain (the vesicle-rich region) at the initial stage, but not the lamellipodia in the growth cone; and (b) that large vacuole formation occurred probably through the fusion of smaller vesicles from the central domain to the most distal segments of the neurite. The total surface area of the accumulated vacuoles could explain the membrane expansion of normal neurite growth. The gradual disappearance of the surface labeling by FITC-WGA on the normal growth cone, suggesting membrane addition, was inhibited by neurotoxin C1. The experiments using the peptides derived from syntaxin, essential for interaction with VAMP or alpha-SNAP, supported the results using neurotoxin C1. Our results demonstrate that syntaxin is involved in axonal growth and indicate that syntaxin may participate directly in the membrane expansion that occurs in the central domain of the growth cone, probably through association with VAMP and SNAPs, in a SNARE-like way. PMID:8698815

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

    PubMed Central

    Shortt, Claire; Scanlan, Eoin; Hilliard, Amber; Cotroneo, Chiara E.; Bourke, Billy

    2016-01-01

    ABSTRACT 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. PMID:27624126

  7. 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

  8. 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.

  9. Effects of PNPG on cell growth cycle, motility machinery and quorum sensing in Serratia marcescens.

    PubMed

    Wei, Jun-Rong; Horng, Yu-Tze; Lai, Hsin-Chih; Luh, Kwen-Tay; Ho, Shen-Wu

    2004-02-01

    p-Nitrophenylglycerol (PNPG) effectively inhibits swarming of the enterobacterium Proteus mirabilis. The underlying mechanism of inhibition is unclear. We have now found that both PNPG also inhibits motility and swarming in another enterobacterium, Serratia marcescens. While the peak promoter activities of the flagellar master operon (flhDCSm), the flagellin structural gene (hagSm) and the nuclease gene (nucASm) in S. marcescens increased with increasing PNPG concentration, the expression of these genes was delayed in accordance with the reduced growth rate. As the quorum-sensing system is involved in the regulation of swarming in S. marcescens, we also examined the effect of PNPG on the production of quorum-sensing signal molecules and found that their expression was delayed with a reduced level. PNPG, therefore, had a pleiotropic effect on all aspects of S. marcescens physiology relating to swarming. The underlying molecular mechanism remains to be elucidated.

  10. Semaphorin3a Enhances Endocytosis at Sites of Receptor–F-Actin Colocalization during Growth Cone Collapse

    PubMed Central

    Fournier, Alyson E.; Nakamura, Fumio; Kawamoto, Susumu; Goshima, Yoshio; Kalb, Robert G.; Strittmatter, Stephen M.

    2000-01-01

    Axonal growth cone collapse is accompanied by a reduction in filopodial F-actin. We demonstrate here that semaphorin 3A (Sema3A) induces a coordinated rearrangement of Sema3A receptors and F-actin during growth cone collapse. Differential interference contrast microscopy reveals that some sites of Sema3A-induced F-actin reorganization correlate with discrete vacuoles, structures involved in endocytosis. Endocytosis of FITC-dextran by the growth cone is enhanced during Sema3A treatment, and sites of dextran accumulation colocalize with actin-rich vacuoles and ridges of membrane. Furthermore, the Sema3A receptor proteins, neuropilin-1 and plexin, and the Sema3A signaling molecule, rac1, also reorganize to vacuoles and membrane ridges after Sema3A treatment. These data support a model whereby Sema3A stimulates endocytosis by focal and coordinated rearrangement of receptor and cytoskeletal elements. Dextran accumulation is also increased in retinal ganglion cell (RGC) growth cones, in response to ephrin A5, and in RGC and DRG growth cones, in response to myelin and phorbol-ester. Therefore, enhanced endocytosis may be a general principle of physiologic growth cone collapse. We suggest that growth cone collapse is mediated by both actin filament rearrangements and alterations in membrane dynamics. PMID:10769032

  11. Neuronal growth cone retraction relies upon proneurotrophin receptor signaling through Rac

    PubMed Central

    Deinhardt, Katrin; Kim, Taeho; Spellman, Daniel S.; Mains, Richard E.; Eipper, Betty A.; Neubert, Thomas A.; Chao, Moses V.; Hempstead, Barbara L.

    2012-01-01

    Growth of axons and dendrites is a dynamic process that involves guidance molecules, adhesion proteins, and neurotrophic factors. Although neurite extension during development has been extensively studied, the intracellular mechanisms that mediate neurite retraction are poorly understood. Here, we show that the proneurotrophin, proNGF, induces acute collapse of growth cones of cultured hippocampal neurons. This retraction is initiated by an interaction between p75NTR and the sortilin family member, SorCS2 (sortilin-related VPS10 domain containing receptor 2). Binding of proNGF to the p75NTR-SorCS2 complex induced growth cone retraction by initiating the dissociation of the guanine-nucleotide exchange factor Trio from the p75NTR- SorCS2 complex, resulting in decreased Rac activity, and consequently, growth cone collapse. The actin-bundling protein fascin also became inactivated, contributing to the destabilization and collapse of actin filaments. These results identify a bifunctional signaling mechanism by which proNGF regulates actin dynamics to modulate neuronal morphology acutely. PMID:22155786

  12. 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

  13. Deiodinase Knockdown during Early Zebrafish Development Affects Growth, Development, Energy Metabolism, Motility and Phototransduction

    PubMed Central

    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

  14. Rapid Changes in the Translatome during the Conversion of Growth Cones to Synaptic Terminals.

    PubMed

    Zhang, Kelvin Xi; Tan, Liming; Pellegrini, Matteo; Zipursky, S Lawrence; McEwen, Jason M

    2016-02-01

    A common step in the formation of neural circuits is the conversion of growth cones to presynaptic terminals. Characterizing patterns of global gene expression during this process is problematic due to the cellular diversity of the brain and the complex temporal dynamics of development. Here, we take advantage of the synchronous conversion of Drosophila photoreceptor growth cones into presynaptic terminals to explore global changes in gene expression during presynaptic differentiation. Using a tandemly tagged ribosome trap (T-TRAP) and RNA sequencing (RNA-seq) at multiple developmental times, we observed dramatic changes in coding and non-coding RNAs with presynaptic differentiation. Marked changes in the mRNA encoding transmembrane and secreted proteins occurred preferentially. The 3' UTRs of transcripts encoding synaptic proteins were preferentially lengthened, and these extended UTRs were preferentially enriched for sites recognized by RNA binding proteins. These data provide a rich resource for uncovering the regulatory logic underlying presynaptic differentiation. PMID:26832407

  15. Cyclic AMP-dependent protein phosphorylation in isolated neuronal growth cones from developing rat forebrain.

    PubMed

    Lockerbie, R O; Eddé, B; Prochiantz, A

    1989-03-01

    We have shown recently that neuronal growth cones isolated from developing rat forebrain possess an appreciable activity of adenylate cyclase, which produces cyclic AMP and can be stimulated by various neurotransmitter receptor agonists and by forskolin. To investigate cyclic AMP-mediated biochemical mechanisms in isolated growth cones, we have centered the present study on cyclic AMP-dependent protein phosphorylation. One-dimensional gel electrophoretic analysis showed that cyclic AMP analogs increased incorporation of 32P into several phosphoproteins in molecular mass ranges of 50-58 and 76-82 kilodaltons, including those of 82, 76, and 51 kilodaltons. Two-dimensional electrophoresis, using isoelectric focusing in the first dimension, resolved phosphorylated alpha- and beta-tubulin species, actin, a very acidic protein (isoelectric point 4.0) with a molecular mass of 93 kilodaltons, and two proteins (x and x') closely neighboring beta-tubulin. Two other phosphoproteins seen in the gels had molecular masses of 56 and 51 kilodaltons (respective isoelectric points, 4.5 and 4.4) and, along with the 93-kilodalton phosphoprotein, were highly enriched in the isolated growth cones. Only the tubulin and actin species were major proteins in the isolated growth cones. Cyclic AMP analogs enhanced incorporation of 32P into phosphoproteins x and x', and, as assessed by immunoprecipitation, into beta-tubulin. Peptide digest experiments suggested that phosphoproteins x and x' are unrelated to beta-tubulin. Nonequilibrium two-dimensional electrophoresis resolved many phosphoproteins, of which a 79- and 75-kilodalton doublet, a 74-kilodalton species, and a 58-kilodalton doublet showed enhanced incorporation of 32P in the presence of cyclic AMP.

  16. Growth cones isolated from developing rat forebrain: uptake and release of GABA and noradrenaline.

    PubMed

    Lockerbie, R O; Gordon-Weeks, P R; Pearce, B R

    1985-08-01

    A growth cone-enriched fraction isolated from neonatal rat forebrain was shown to accumulate gamma-amino [3H]butyric acid ([3H]-GABA) and [3H]noradrenaline ([3H]NA). Uptake of both neurotransmitters was sodium- and temperature-dependent and exhibited saturation kinetics with Km values of 17.7 microM and 4.5 microM respectively and Vmax values of 114 pmol/min/mg protein and 59 pmol/min/mg protein respectively. Electron microscopic autoradiography showed that about 50% of isolated growth cones can accumulate [3H]GABA. Inhibitor studies showed that beta-alanine was a relatively weak inhibitor of [3H]GABA uptake compared to nipecotic acid and diamino-butyric acid. Growth cone fractions preloaded with [3H]GABA and [3H]NA demonstrated a K+ (25 mM) -induced release of both neurotransmitters. Of the K+-stimulated release of [3H]GABA 50% was Ca2+-dependent, whereas the release of [3H]NA was entirely Ca2+-independent.

  17. 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

    2014-01-01

    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). PMID:25225829

  18. [Cell growth and motility in culture (in vitro) under microgravity conditions. The Fibroblast Experiment].

    PubMed

    Tairbekov, M G; Margolis, L B; Baĭbakov, B A; Gabova, A V; Dergacheva, G B

    1994-01-01

    The experiment "Fibroblast" was performed in 1992 on biosatellite "Cosmos-2229" in onboard device "Biobox" designed by the order of European Space Agency. The main objective was elucidation of the mechanisms responsible for the effect of space flight factors, mostly microgravity, on cell culture. We studied time-related changes in growth, motility and some morphological characteristics of the cells in monolayer cultures on a solid substrate and in three-dimensional cultures supported by sponge gels. Studies were carried out on connective tissue cells isolated from the mouse embryos. Comparative after-flight analysis of the cell cultures exposed to space flight and of those under the normal gravity conditions (1 g) on the Earth has revealed some differences. The space flight conditions, mainly microgravity, induced marked changes in morphological characteristics and functional activity of the cultured fibroblasts: changes in the nucleus size and shape, retardation of cell growth and division rate. We believe that these changes may be due to weakening of intercellular contacts and cell adhesion to the substrate. These findings are important both for general biology and space medicine, specifically for the problems of tissue regeneration and wound healing under the conditions of long-term space flight.

  19. Isolated neuronal growth cones from developing rat forebrain possess adenylate cyclase activity which can be augmented by various receptor agonists.

    PubMed

    Lockerbie, R O; Hervé, D; Blanc, G; Tassin, J P; Glowinski, J

    1988-01-01

    Isolated neuronal growth cones from neonatal rat forebrain were found to contain a high specific activity of adenylate cyclase (61 pmol cyclic AMP/min/mg protein) compared to the pelleted starting homogenate (5 pmol cyclic AMP/min/mg protein). Forskolin at 10(-4) M increased adenylate cyclase activity in both the pelleted homogenate and growth cone fraction by 70 and 217 pmol cyclic AMP/min/mg protein, respectively, over basal levels. The incremental effect of forskolin was 3-fold greater in the growth cone fraction than in the pelleted homogenate. However, relative to basal levels in each of the two fractions, forskolin increased adenylate cyclase activity in the growth cone fraction by only approx. 5-fold compared to 15-fold in the pelleted homogenate. Dopamine (10(-4) M), vasoactive intestinal polypeptide (10(-6) M) and isoproterenol (10(-5) M) also augmented adenylate cyclase activity in the two fractions. In the growth cone fraction, dopamine and vasoactive intestinal polypeptide produced a stimulation over basal levels by approx. 20 pmol cyclic AMP/min/mg protein while isoproterenol produced a stimulation of approx. 10 pmol cAMP/min/mg protein. The incremental effects of these receptor agonists in the growth cone fraction are approx. 5-fold greater than in the pelleted homogenate. The dopamine-sensitive adenylate cyclase activity in the growth cone fraction could be blocked by the compound SCH23390, a selective D1 receptor antagonist. At saturating concentrations, all combinations of dopamine, vasoactive intestinal polypeptide and isoproterenol were found to be completely additive on adenylate cyclase activity in the growth cone fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

  20. GPCR cell signaling pathways mediating embryonic chick retinal growth cone collapse induced by LPA and S1P

    PubMed Central

    Fincher, Jarod; Whiteneck, Canaan; Birgbauer, Eric

    2014-01-01

    In the development of the nervous system, one of the critical aspects is the proper navigation of axons to their targets, the problem of axonal guidance. We are using the chick visual system as a model to investigate the role of the lysophospholipids lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) as potential axon guidance cues. We show that both LPA and S1P cause specific, dose-dependent growth cone collapse of retinal neurons in vitro in the chick model system, with slight differences to mouse, but very similar to Xenopus. Because LPA and S1P receptors are GPCRs, we analyzed the intracellular signaling pathways using pharmacological inhibitors in chick retinal neurons. Blocking rho kinase (ROCK) prevented growth cone collapse by LPA and S1P, while blocking PLC or chelating calcium had no effect on growth cone collapse. Inhibiting Gi/o with pertussis toxin resulted in a partial reduction of growth cone collapse, both with LPA and S1P. Inhibition of p38 blocked growth cone collapse mediated by LPA but not S1P. Thus, in addition to the involvement of the G12/13-ROCK pathway, LPA and S1P induced collapse of chick retinal growth cones has a partial requirement for Gi/o. PMID:25138637

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

    PubMed

    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

  2. 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

  3. Bidirectional interactions between NOX2-type NADPH oxidase and the F-actin cytoskeleton in neuronal growth cones.

    PubMed

    Munnamalai, Vidhya; Weaver, Cory J; Weisheit, Corinne E; Venkatraman, Prahatha; Agim, Zeynep Sena; Quinn, Mark T; Suter, Daniel M

    2014-08-01

    NADPH oxidases are important for neuronal function but detailed subcellular localization studies have not been performed. Here, we provide the first evidence for the presence of functional NADPH oxidase 2 (NOX2)-type complex in neuronal growth cones and its bidirectional relationship with the actin cytoskeleton. NADPH oxidase inhibition resulted in reduced F-actin content, retrograde F-actin flow, and neurite outgrowth. Stimulation of NADPH oxidase via protein kinase C activation increased levels of hydrogen peroxide in the growth cone periphery. The main enzymatic NADPH oxidase subunit NOX2/gp91(phox) localized to the growth cone plasma membrane and showed little overlap with the regulatory subunit p40(phox) . p40(phox) itself exhibited colocalization with filopodial actin bundles. Differential subcellular fractionation revealed preferential association of NOX2/gp91(phox) and p40(phox) with the membrane and the cytoskeletal fraction, respectively. When neurite growth was evoked with beads coated with the cell adhesion molecule apCAM, we observed a significant increase in colocalization of p40(phox) with NOX2/gp91(phox) at apCAM adhesion sites. Together, these findings suggest a bidirectional functional relationship between NADPH oxidase activity and the actin cytoskeleton in neuronal growth cones, which contributes to the control of neurite outgrowth. We have previously shown that reactive oxygen species (ROS) are critical for actin organization and dynamics in neuronal growth cones as well as neurite outgrowth. Here, we report that the cytosolic subunit p40(phox) of the NOX2-type NADPH oxidase complex is partially associated with F-actin in neuronal growth cones, while ROS produced by this complex regulates F-actin dynamics and neurite growth. These findings provide evidence for a bidirectional relationship between NADPH oxidase activity and the actin cytoskeleton in neuronal growth cones. PMID:24702317

  4. 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.

  5. Dynamic responses of Xenopus retinal ganglion cell axon growth cones to netrin-1 as they innervate their in vivo target

    PubMed Central

    Shirkey, Nicole J.; Manitt, Colleen; Zuniga, Liliana; Cohen-Cory, Susana

    2012-01-01

    Netrin-1 influences retinal ganglion cell (RGC) axon pathfinding and also participates in the branching and synaptic differentiation of mature RGC axons at their target. To investigate whether netrin also serves as an early target recognition signal in the brain, we examined the dynamic behavior of Xenopus RGC axons soon after they innervate the optic tectum. Time-lapse confocal microscopy imaging of RGC axons expressing EYFP demonstrated that netrin-1 is involved in early axon branching, as recombinant netrin-1 halted further advancement of growth cones into the tectum and induced back branching. RGC growth cones exhibited differential responses to netrin-1 that depended on the degree of differentiation of the axon and the developmental stage of the tadpole. Netrin-1 decreased the total number of branches on newly arrived RGC growth cones at the target, but increased the dynamic branching of more mature arbors at the later developmental stage. To further explore the response of axonal growth cones to netrin, Xenopus RGC axons were followed in culture by time-lapse imaging. Exposure to netrin-1 rapidly increased the forward advancement of the axon and decreased the size and expanse of the growth cone, while also inducing back branching. Taken together, the differential in vivo and in vitro responses to netrin-1 suggest that netrin alone is not sufficient to induce the cessation of growth cone advancement in the absence of a target, but can independently modulate axon branching. Collectively, our findings reveal a novel role for netrin on RGC axon branch initiation as growth cones innervate their target. PMID:21858928

  6. 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

  7. Insulin-like growth factor I receptors of fetal brain are enriched in nerve growth cones and contain a beta-subunit variant.

    PubMed Central

    Quiroga, S; Garofalo, R S; Pfenninger, K H

    1995-01-01

    Nerve growth cones isolated from fetal rat brain are highly enriched in a 97-kDa glycoprotein, termed beta gc, that comigrates with the beta subunit of the IGF-I receptor upon two-dimensional PAGE and is disulfide-linked to this receptor's alpha subunit. Antibodies prepared to a conserved domain shared by the insulin and IGF-I receptor beta subunits (AbP2) or to beta gc were used to study receptor distribution further. Subcellular fractionation of the fetal brain segregated most AbP2 immunoreactivity away from growth cones, whereas most beta gc immunoreactivity copurified with growth cones. Experiments involving ligand-activated receptor autophosphorylation confirmed the concentration of IGF-I but not of insulin receptors in growth cone fractions. These results indicate the enrichment of IGF-I receptors in (presumably axonal) growth cones of the differentiating neuron. Furthermore, the segregation of beta gc from AbP2 immunoreactivity suggests that such neurons express an immunochemically distinct variant of the IGF-I receptor beta subunit at the growth cone. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:7753803

  8. FLIM FRET Visualization of Cdc42 Activation by Netrin-1 in Embryonic Spinal Commissural Neuron Growth Cones.

    PubMed

    Rappaz, Benjamin; Lai Wing Sun, Karen; Correia, James P; Wiseman, Paul W; Kennedy, Timothy E

    2016-01-01

    Netrin-1 is an essential extracellular chemoattractant that signals through its receptor DCC to guide commissural axon extension in the embryonic spinal cord. DCC directs the organization of F-actin in growth cones by activating an intracellular protein complex that includes the Rho GTPase Cdc42, a critical regulator of cell polarity and directional migration. To address the spatial distribution of signaling events downstream of netrin-1, we expressed the FRET biosensor Raichu-Cdc42 in cultured embryonic rat spinal commissural neurons. Using FLIM-FRET imaging we detected rapid activation of Cdc42 in neuronal growth cones following application of netrin-1. Investigating the signaling mechanisms that control Cdc42 activation by netrin-1, we demonstrate that netrin-1 rapidly enriches DCC at the leading edge of commissural neuron growth cones and that netrin-1 induced activation of Cdc42 in the growth cone is blocked by inhibiting src family kinase signaling. These findings reveal the activation of Cdc42 in embryonic spinal commissural axon growth cones and support the conclusion that src family kinase activation downstream of DCC is required for Cdc42 activation by netrin-1. PMID:27482713

  9. FLIM FRET Visualization of Cdc42 Activation by Netrin-1 in Embryonic Spinal Commissural Neuron Growth Cones

    PubMed Central

    Rappaz, Benjamin; Lai Wing Sun, Karen; Correia, James P.; Wiseman, Paul W.; Kennedy, Timothy E.

    2016-01-01

    Netrin-1 is an essential extracellular chemoattractant that signals through its receptor DCC to guide commissural axon extension in the embryonic spinal cord. DCC directs the organization of F-actin in growth cones by activating an intracellular protein complex that includes the Rho GTPase Cdc42, a critical regulator of cell polarity and directional migration. To address the spatial distribution of signaling events downstream of netrin-1, we expressed the FRET biosensor Raichu-Cdc42 in cultured embryonic rat spinal commissural neurons. Using FLIM-FRET imaging we detected rapid activation of Cdc42 in neuronal growth cones following application of netrin-1. Investigating the signaling mechanisms that control Cdc42 activation by netrin-1, we demonstrate that netrin-1 rapidly enriches DCC at the leading edge of commissural neuron growth cones and that netrin-1 induced activation of Cdc42 in the growth cone is blocked by inhibiting src family kinase signaling. These findings reveal the activation of Cdc42 in embryonic spinal commissural axon growth cones and support the conclusion that src family kinase activation downstream of DCC is required for Cdc42 activation by netrin-1. PMID:27482713

  10. Asymmetric endocytosis and remodeling of β1-integrin adhesions during growth cone chemorepulsion by MAG

    PubMed Central

    Hines, Jacob H.; Abu-Rub, Mohammad; Henley, John R.

    2011-01-01

    Gradients of chemorepellent factors released from myelin may impair axon pathfinding and neuro-regeneration after injury. Analogous to the process of chemotaxis in invasive tumor cells, we found that axonal growth cones of Xenopus spinal neurons modulate the functional distribution of integrin receptors during chemorepulsion induced by myelin-associated glycoprotein (MAG). A focal MAG gradient induced polarized endocytosis and concomitant asymmetric loss of β1-integrin and vinculin-containing adhesions on the repellent side during repulsive turning. Loss of symmetrical β1-integrin function was both necessary and sufficient for chemorepulsion, which required internalization by clathrin-mediated endocytosis. Induction of repulsive Ca2+ signals was necessary and sufficient for the stimulated rapid endocytosis of β1-integrin. Altogether, these findings identify β1-integrin as an important functional cargo during Ca2+-dependent rapid endocytosis stimulated by a diffusible guidance cue. Such dynamic redistribution allows the growth cone to rapidly adjust adhesiveness across its axis, an essential feature for initiating chemotactic turning. PMID:20512137

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  12. Drosophila Ten-m and Filamin Affect Motor Neuron Growth Cone Guidance

    PubMed Central

    Zheng, Lihua; Michelson, Yehudit; Freger, Vita; Avraham, Ziva; Venken, Koen J. T.; Bellen, Hugo J.; Justice, Monica J.; Wides, Ron

    2011-01-01

    The Drosophila Ten-m (also called Tenascin-major, or odd Oz (odz)) gene has been associated with a pair-rule phenotype. We identified and characterized new alleles of Drosophila Ten-m to establish that this gene is not responsible for segmentation defects but rather causes defects in motor neuron axon routing. In Ten-m mutants the inter-segmental nerve (ISN) often crosses segment boundaries and fasciculates with the ISN in the adjacent segment. Ten-m is expressed in the central nervous system and epidermal stripes during the stages when the growth cones of the neurons that form the ISN navigate to their targets. Over-expression of Ten-m in epidermal cells also leads to ISN misrouting. We also found that Filamin, an actin binding protein, physically interacts with the Ten-m protein. Mutations in cheerio, which encodes Filamin, cause defects in motor neuron axon routing like those of Ten-m. During embryonic development, the expression of Filamin and Ten-m partially overlap in ectodermal cells. These results suggest that Ten-m and Filamin in epidermal cells might together influence growth cone progression. PMID:21857973

  13. 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

  14. 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

  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. Differentiation of neuronal growth cones: specialization of filopodial tips for adhesive interactions.

    PubMed Central

    Tsui, H C; Lankford, K L; Klein, W L

    1985-01-01

    Adhesive contacts made by filopodia of developing neurons are important in neurite growth and in the formation of synaptic junctions. In the present work, filopodial interactions of cultured chicken retina neurons were studied by using video-enhanced contrast, differential interference contrast (VEC-DIC) microscopy and the high-voltage electron microscope (HVEM). Use of the HVEM to examine whole mounts of fixed cells showed that filopodia in older cultures developed an appearance that might be expected of nascent synapses, becoming enlarged at their endings and accumulating organelles resembling synaptic vesicles. VEC-DIC microscopy, used to observe the motility and adhesive properties of filopodia in living cells, showed there was a particularly high affinity between filopodia tips. Contacting filopodia typically repositioned themselves so they could attach at a tip-to-tip position, occasionally bending as much as 90 degrees to achieve this preferred orientation. Interacting filopodia frequently remained together as they pushed or pulled on each other, moved laterally together, or stretched tightly and underwent intense vibratory movements. Such linked motility occurred even when apparent gaps existed between the filopodia. Examination of these gaps with the HVEM revealed filamentous structures linking the apposed membranes. The filamentous links were 10-13 nm in diameter and 30-100 nm long. Although it has not yet been established that the filaments reflect the native configuration of the interconnecting materials, the structures seem likely to be associated with the strongly adhesive behavior of the filopodial tips. The possible significance of these structural and functional properties of filopodia tips to axon growth and synapse formation is discussed. Images PMID:3865227

  17. 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.

  18. 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

  19. 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. PMID:27432222

  20. Bidirectional interactions between NOX2-type NADPH oxidase and the F-actin cytoskeleton in neuronal growth cones

    PubMed Central

    Munnamalai, Vidhya; Weaver, Cory J.; Weisheit, Corinne E.; Venkatraman, Prahatha; Agim, Zeynep Sena; Quinn, Mark T.; Suter, Daniel M.

    2014-01-01

    NADPH oxidases are important for neuronal function but detailed subcellular localization studies have not been performed. Here, we provide the first evidence for the presence of functional NOX2-type NADPH oxidase complex in neuronal growth cones and its bidirectional relationship with the actin cytoskeleton. NADPH oxidase inhibition resulted in reduced F-actin content, retrograde F-actin flow, and neurite outgrowth. Stimulation of NADPH oxidase via protein kinase C activation increased levels of hydrogen peroxide in the growth cone periphery. The main enzymatic NADPH oxidase subunit NOX2/gp91phox localized to the growth cone plasma membrane and showed little overlap with the regulatory subunit p40phox. p40phox itself exhibited co-localization with filopodial actin bundles. Differential subcellular fractionation revealed preferential association of NOX2/gp91phox and p40phox with the membrane and the cytoskeletal fraction, respectively. When neurite growth was evoked with beads coated with the cell adhesion molecule apCAM, we observed a significant increase in co-localization of p40phox with NOX2/gp91phox at apCAM adhesion sites. Together, these findings suggest a bidirectional functional relationship between NADPH oxidase activity and the actin cytoskeleton in neuronal growth cones, which contributes to the control of neurite outgrowth. PMID:24702317

  1. 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.

  2. Measurement of Mandibular Growth Using Cone-Beam Computed Tomography: A Miniature Pig Model Study

    PubMed Central

    Li, Jia-Da; Lu, Tung-Wu; Chang, Hau-Hung; Hu, Chih-Chung

    2014-01-01

    The purpose of this study was to measure the long-term growth of the mandible in miniature pigs using 3D Cone-Beam Computerized Tomography (CBCT). The mandibles of the pigs were scanned monthly over 12 months using CBCT and the 3D mandibular models were reconstructed from the data. Seventeen anatomical landmarks were identified and classified into four groups of line segments, namely anteroposterior, superoinferior, mediolateral and anteroinferior. The inter-marker distances, inter-segmental angles, volume, monthly distance changes and percentage of changes were calculated to describe mandibular growth. The total changes of inter-marker distances were normalized to the initial values. All inter-marker distances increased over time, with the greatest mean normalized total changes in the superoinferior and anteroposterior groups (p<0.05). Monthly distance changes were greatest during the first four months and then reduced over time. Percentages of inter-marker distance changes were similar among the groups, reaching half of the overall growth around the 4th month. The mandibular volume growth increased non-linearly with time, accelerating during the first five months and slowing during the remaining months. The growth of the mandible was found to be anisotropic and non-homogeneous within the bone and non-linear over time, with faster growth in the ramus than in the body. These growth patterns appeared to be related to the development of the dentition, providing necessary space for the teeth to grow upward for occlusion and for the posterior teeth to erupt. PMID:24801528

  3. 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

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

    PubMed

    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.

  5. Disruption of pioneer growth cone guidance in vivo by removal of glycosyl-phosphatidylinositol-anchored cell surface proteins.

    PubMed

    Chang, W S; Serikawa, K; Allen, K; Bentley, D

    1992-02-01

    Cell surface proteins anchored to membranes via covalently attached glycosyl-phosphatidylinositol (GPI) have been implicated in neuronal adhesion, promotion of neurite outgrowth and directed cell migration. Treatment of grasshopper embryos with bacterial phosphatidylinositol-specific phospholipase C (PI-PLC), an enzyme that cleaves the GPI anchor, often induced disruptions in the highly stereotyped migrations of peripheral pioneer growth cones and afferent neuron cell bodies. In distal limb regions of embryos treated with PI-PLC at early stages of pioneer axon outgrowth, growth cones lost their proximal orientation toward the central nervous system (CNS) and turned distally. Pioneer growth cones in treated limbs also failed to make a characteristic ventral turn along the trochanter-coxa (Tr-Cx) segment boundary, and instead continued to grow proximally across the boundary. Treatment at an earlier stage of development caused pre-axonogenesis Cx1 neurons to abandon their normal circumferential migration and reorient toward the CNS. None of these abnormal phenotypes were observed in limbs of untreated embryos or embryos exposed to other phospholipases that do not release GPI-anchored proteins. Incubation of embryos with PI-PLC effectively removed immunoreactivity for fasciclin I, a GPI-anchored protein expressed on a subset of neuronal surfaces. These results suggest that cell surface GPI-anchored proteins are involved in pioneer growth cone guidance and in pre-axonogenesis migration of neurons in the grasshopper limb bud in vivo.

  6. Dynamic Localization of G-actin During Membrane Protrusion in Neuronal Motility

    PubMed Central

    Lee, Chi Wai; Vitriol, Eric A.; Shim, Sangwoo; Wise, Ariel L.; Velayutham, Radhi P.; Zheng, James Q.

    2013-01-01

    Summary Background Actin-based cell motility is fundamental for the development, function, and malignant events of eukaryotic organisms. During neural development, axonal growth cones depend on rapid assembly and disassembly of actin filaments (F-actin) for their guided extension to specific targets for wiring. Monomeric globular actin (G-actin) is the building block for F-actin but is not considered to play a direct role in spatiotemporal control of actin dynamics in cell motility. Results Here we report that a pool of G-actin dynamically localizes to the leading edge of growth cones and neuroblastoma cells to spatially elevate the G-/F-actin ratio that drives membrane protrusion and cell movement. Loss of G-actin localization leads to the cessation and retraction of membrane protrusions. Moreover, G-actin localization occurs asymmetrically in growth cones during attractive turning. Finally, we identify the actin monomer binding proteins profilin and thymosin β4 as key molecules that localize actin monomers to the leading edge of lamellipodia for their motility. Conclusions Our results suggest that dynamic localization of G-actin provides a novel mechanism to regulate the spatiotemporal actin dynamics underlying membrane protrusion in cell locomotion and growth cone chemotaxis. PMID:23746641

  7. 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.

  8. 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. PMID:25261525

  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. Nerve growth factor stimulates axon outgrowth through negative regulation of growth cone actomyosin restraint of microtubule advance

    PubMed Central

    Turney, Stephen G.; Ahmed, Mostafa; Chandrasekar, Indra; Wysolmerski, Robert B.; Goeckeler, Zoe M.; Rioux, Robert M.; Whitesides, George M.; Bridgman, Paul C.

    2016-01-01

    Nerve growth factor (NGF) promotes growth, differentiation, and survival of sensory neurons in the mammalian nervous system. Little is known about how NGF elicits faster axon outgrowth or how growth cones integrate and transform signal input to motor output. Using cultured mouse dorsal root ganglion neurons, we found that myosin II (MII) is required for NGF to stimulate faster axon outgrowth. From experiments inducing loss or gain of function of MII, specific MII isoforms, and vinculin-dependent adhesion-cytoskeletal coupling, we determined that NGF causes decreased vinculin-dependent actomyosin restraint of microtubule advance. Inhibition of MII blocked NGF stimulation, indicating the central role of restraint in directed outgrowth. The restraint consists of myosin IIB- and IIA-dependent processes: retrograde actin network flow and transverse actin bundling, respectively. The processes differentially contribute on laminin-1 and fibronectin due to selective actin tethering to adhesions. On laminin-1, NGF induced greater vinculin-dependent adhesion–cytoskeletal coupling, which slowed retrograde actin network flow (i.e., it regulated the molecular clutch). On fibronectin, NGF caused inactivation of myosin IIA, which negatively regulated actin bundling. On both substrates, the result was the same: NGF-induced weakening of MII-dependent restraint led to dynamic microtubules entering the actin-rich periphery more frequently, giving rise to faster elongation. PMID:26631553

  11. 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.

  12. Cyclic AMP reduces adhesion of isolated neuronal growth cones from developing rat forebrain to an astrocytic cell line from embryonic mouse striatum.

    PubMed

    Lockerbie, R O; Autillo-Touati, A; Araud, D; Seite, R; Chneiweiss, H; Glowinski, J; Prochiantz, A

    1989-01-01

    We have recently shown that isolated neuronal growth cones from developing rat forebrain possess an appreciable activity of adenylate cyclase, producing cyclic adenosine monophosphate, which can be stimulated by various neurotransmitter receptor agonists and by forskolin [Lockerbie R. O., Hervé D., Blanc G., Tassin J. P. and Glowinski J. (1988) Devl Brain Res. 38, 19-25]. In the present study, we have investigated the effect of cyclic adenosine monophosphate in an in vitro adhesion assay established between [3H]GABA-labelled isolated growth cones and a Simian virus-40 transformed astrocytic cell line from embryonic mouse striatum. Adhesion of the isolated growth cones onto the astrocytic clone increased steadily up to about 45 min before it began to level off at ca 16-18% of total [3H]GABA-labelled isolated growth cones added. Adhesion of the isolated growth cones onto the astrocytic clone was much superior to that seen on polyornithine and, in particular, on non-treated tissue culture wells. Adhesion "at plateau" was independent of both temperature and extracellular Ca2+ and was markedly reduced (ca 50%) by trypsin pre-treatment of the isolated growth cones. Pre-treatment of the isolated growth cones with either forskolin or lipophilic analogues of cyclic adenosine monophosphate attenuated adhesion in a time- and concentration-dependent manner. Approximately 30% reduction in adhesion to the astrocytic clone "at plateau" was observed after a 15 min pre-treatment of the isolated growth cones with forskolin at 10(-4) M or cyclic adenosine monophosphate analogues at 10(-3) M. A cyclic guanosine monophosphate analogue was without effect on adhesion of isolated growth cones. Scanning electron microscope analysis showed that isolated growth cones pre-treated with either cyclic adenosine monophosphate analogues or forskolin had a simpler morphology when attached to the astrocytic clone than isolated growth cones under control conditions. Pre-treatment of the isolated

  13. 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

  14. 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

  15. Short window of opportunity for calpain induced growth cone formation after axotomy of Aplysia neurons.

    PubMed

    Gitler, Daniel; Spira, Micha E

    2002-09-15

    Our laboratory has established that local activation of calpain by a transient elevation of the free intracellular calcium concentration is crucial for the induction of growth cone (GC) formation in cultured Aplysia neurons. The mechanisms and stages in which calpain is involved in the formation of a GC are not known. We began to study these questions by determining the nature of calpain's action and the stages in which calpain activity affects the cascade of events that leads to the formation of the GC and its extension. We report that the calpain-dependent transformation of an axonal segment into a GC occurs within a narrow window of opportunity that lasts approximately 5 min. If calpain is inhibited during this window of opportunity, GC formation does not occur. Inhibition of calpain after the window of opportunity slows down the rate of lamellipodial extension but doesn't arrest it. The proteolysis of spectrin, a calpain substrate and a major component of the membrane skeleton, occurs within this window of opportunity, in agreement with the hypothesis that spectrin proteolysis is an early step in the formation of the GC. If the onset of proteolysis is deferred, spectrin remains unchanged and GC formation is compromised. We suggest that calpain participates in two different processes: it is critical for the triggering of GC formation and plays a modulatory role during the extension of the GC's lamellipodia.

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

    PubMed

    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

  17. 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.

  18. 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. PMID:27270387

  19. ALDH isozymes downregulation affects cell growth, cell motility and gene expression in lung cancer cells

    PubMed Central

    Moreb, Jan S; Baker, Henry V; Chang, Lung-Ji; Amaya, Maria; Lopez, M Cecilia; Ostmark, Blanca; Chou, Wayne

    2008-01-01

    Background Aldehyde dehydrogenase isozymes ALDH1A1 and ALDH3A1 are highly expressed in non small cell lung cancer. Neither the mechanisms nor the biologic significance for such over expression have been studied. Methods We have employed oligonucleotide microarrays to analyze changes in gene profiles in A549 lung cancer cell line in which ALDH activity was reduced by up to 95% using lentiviral mediated expression of siRNA against both isozymes (Lenti 1+3). Stringent analysis methods were used to identify gene expression patterns that are specific to the knock down of ALDH activity and significantly different in comparison to wild type A549 cells (WT) or cells similarly transduced with green fluorescent protein (GFP) siRNA. Results We confirmed significant and specific down regulation of ALDH1A1 and ALDH3A1 in Lenti 1+3 cells and in comparison to 12 other ALDH genes detected. The results of the microarray analysis were validated by real time RT-PCR on RNA obtained from Lenti 1+3 or WT cells treated with ALDH activity inhibitors. Detailed functional analysis was performed on 101 genes that were significantly different (P < 0.001) and their expression changed by ≥ 2 folds in the Lenti 1+3 group versus the control groups. There were 75 down regulated and 26 up regulated genes. Protein binding, organ development, signal transduction, transcription, lipid metabolism, and cell migration and adhesion were among the most affected pathways. Conclusion These molecular effects of the ALDH knock-down are associated with in vitro functional changes in the proliferation and motility of these cells and demonstrate the significance of ALDH enzymes in cell homeostasis with a potentially significant impact on the treatment of lung cancer. PMID:19025616

  20. 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

  1. 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. PMID:22617848

  2. G-protein-coupled receptor cell signaling pathways mediating embryonic chick retinal growth cone collapse induced by lysophosphatidic acid and sphingosine-1-phosphate.

    PubMed

    Fincher, Jarod; Whiteneck, Canaan; Birgbauer, Eric

    2014-01-01

    In the development of the nervous system, one of the critical aspects is the proper navigation of axons to their targets, i.e. the problem of axonal guidance. We used the chick visual system as a model to investigate the role of the lysophospholipids lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) as potential axon guidance cues. We showed that both LPA and S1P cause a specific, dose-dependent growth cone collapse of retinal neurons in vitro in the chick model system, with slight differences compared to the mouse but very similar to observations in Xenopus. Because LPA and S1P receptors are G-protein-coupled receptors, we analyzed the intracellular signaling pathways using pharmacological inhibitors in chick retinal neurons. Blocking rho kinase (ROCK) prevented growth cone collapse by LPA and S1P, while blocking PLC or chelating calcium had no effect on growth cone collapse. Inhibition of Gi/o with pertussis toxin resulted in a partial reduction of growth cone collapse, both with LPA and with S1P. Inhibition of p38 blocked growth cone collapse mediated by LPA but not S1P. Thus, in addition to the involvement of the G12/13-ROCK pathway, LPA- and S1P-induced collapse of chick retinal growth cones has a partial requirement for Gi/o. PMID:25138637

  3. 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.

  4. Downregulation of TFPI in breast cancer cells induces tyrosine phosphorylation signaling and increases metastatic growth by stimulating cell motility

    PubMed Central

    2011-01-01

    Background Increased hemostatic activity is common in many cancer types and often causes additional complications and even death. Circumstantial evidence suggests that tissue factor pathway inhibitor-1 (TFPI) plays a role in cancer development. We recently reported that downregulation of TFPI inhibited apoptosis in a breast cancer cell line. In this study, we investigated the effects of TFPI on self-sustained growth and motility of these cells, and of another invasive breast cancer cell type (MDA-MB-231). Methods Stable cell lines with TFPI (both α and β) and only TFPIβ downregulated were created using RNA interference technology. We investigated the ability of the transduced cells to grow, when seeded at low densities, and to form colonies, along with metastatic characteristics such as adhesion, migration and invasion. Results Downregulation of TFPI was associated with increased self-sustained cell growth. An increase in cell attachment and spreading was observed to collagen type I, together with elevated levels of integrin α2. Downregulation of TFPI also stimulated migration and invasion of cells, and elevated MMP activity was involved in the increased invasion observed. Surprisingly, equivalent results were observed when TFPIβ was downregulated, revealing a novel function of this isoform in cancer metastasis. Conclusions Our results suggest an anti-metastatic effect of TFPI and may provide a novel therapeutic approach in cancer. PMID:21849050

  5. Alpha 7 nicotinic receptor coupling to heterotrimeric G proteins modulates RhoA activation, cytoskeletal motility, and structural growth.

    PubMed

    King, Justin R; Kabbani, Nadine

    2016-08-01

    Nicotinic acetylcholine receptors (nAChRs) modulate the growth and structure of neurons throughout the nervous system. Ligand stimulation of the α7 nAChR has been shown to regulate the large heterotrimeric GTP-binding protein (G protein) signaling in various types of cells. Here, we demonstrate a role for α7 nAChR/G protein interaction in the activation of the small (monomeric) RhoA GTPase leading to cytoskeletal changes during neurite growth. Treatment of PC12 cells with the α7 nAChR agonist choline or PNU-282987 was associated with an increase in RhoA activity and an inhibition in neurite growth. Specifically, choline treatment was found to attenuate the velocity of microtubule growth at the growth cone and decrease the rate of actin polymerization throughout the cell. The effects of α7 nAChR activation were abolished by expression of a dominant negative α7 nAChR (α7345-348A ) deficient in G protein coupling. Proteomic analysis of immunoprecipitated α7 nAChR complexes from differentiating PC12 cells and synaptic fractions of the developing mouse hippocampus revealed the existence of Rho GTPase-regulating guanine nucleotide exchange factors within α7 nAChR interactomes. These findings underscore the role of α7 nAChR/G protein in cytoskeletal regulation during neurite growth. This image depicts the hypothesized interaction of the traditionally ionotropic α7 nicotinic acetylcholine receptor (α7 nAChR) and its ability to interact and signal through both large and small G proteins, leading to the regulation of cytoskeletal growth. Using differentiated PC12 cells, and the specific agonist choline, it was shown that α7 nAChR/G protein interactions mediate both short- and long-term neurite growth dynamics through increased RhoA activation. Activation of RhoA was shown to decrease actin polymerization, and lead to an overall decrease in neurite growth via regulation of the microtubule network. Cover Image for this issue: doi: 10.1111/jnc.13330.

  6. 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.

  7. Attenuation of actinomyosinII contractile activity in growth cones accelerates filopodia-guided and microtubule-based neurite elongation.

    PubMed

    Rösner, Harald; Möller, Wolfgang; Wassermann, Torsten; Mihatsch, Julia; Blum, Martin

    2007-10-24

    The myosinII-specific inhibitor blebbistatin was used to attenuate actinomyosinII contractility in E7-chicken retina explant, medulla and spinal cord neuronal cell cultures. Addition of 20-100 microM blebbistatin, a concentration range that reversibly disrupts actin stress fibers, led to a reduction of growth cone lamellipodial areas and to an elongation of filopodia within 5 to 10 min. These morphological changes were completely reversed after removing the inhibitor. In the continued presence of blebbistatin for several hours, a dose-dependent acceleration (up to 6-fold) of neurite outgrowth was observed. The rapidly elongating neuritic processes displayed narrowed growth cones with one to three long filopodia at the leading edge. At the same time, thin neuritic branches emerged in a "push"-like fashion guided by filopodial extensions. Immunocytochemical characterization of these thin sprouts revealed that they contained actin filaments, myosinIIA, phosphorylated neurofilament/tau epitopes, MAP2, NCAM-PSA, and microtubules, demonstrating that these processes presented neurites and not filopodia. The crucial involvement of microtubules in blebbistatin-induced accelerated neurite extension was confirmed by its inhibition in the presence of nocodazole or taxol. The promotion by blebbistatin of neurite outgrowth occurred on polylysine, laminin, as well as on fibronectin as substrate. The presence of the Rho/ROCK-inhibitor Y-27632 also caused a dose-dependent promotion of neurite growth which was, however, 3-fold less pronounced as compared to blebbistatin. In contrast to blebbistatin, Y-27632 led to the enlargement of growth cone lamellipodial extensions. Our data demonstrate that neurite outgrowth and branching are inversely correlated with the degree of actinomyosinII contractility which determines the speed of retrograde flow and turnover of actin filaments and, by this, microtubule extension.

  8. Phosphorylation and interaction of Myopodin by Integrin-Link Kinase Lead to Suppression of Cell Growth and Motility in Prostate Cancer Cells

    PubMed Central

    Yu, Yan-Ping; Luo, Jian-Hua

    2011-01-01

    Myopodin is a tumor suppressor gene that suppresses growth of prostate and urothelial carcinomas. However, the mechanism of myopodin tumor suppressor activity or signaling that leads to activation of myopodin remains unclear. In this report, we showed that the N-terminus of myopodin binds integrin-linked kinase (ILK) both in vivo and in vitro. An ILK interaction motif of 78 amino acids (amino acids 82–157) was identified in the N-terminus region of myopodin. Induction of ILK dependent kinase activity by integrin α7 led to phosphorylation of myopodin both in vivo and in vitro. Knocking down ILK dramatically reduced the inhibition of cell growth and motility mediated by myopodin. A mutant of myopodin lacking the ILK interaction motif is inactive in suppressing the growth and motility of PC3 cells. As a result, this study showed a novel and critical signaling pathway that leads to activation of myopodin. PMID:21643011

  9. 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.

  10. 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

  11. 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

  12. Negative guidance factor-induced macropinocytosis in the growth cone plays a critical role in repulsive axon turning

    PubMed Central

    Kolpak, Adrianne L.; Jiang, Jun; Guo, Daorong; Standley, Clive; Bellve, Karl; Fogarty, Kevin; Bao, Zheng-Zheng

    2009-01-01

    Macropinocytosis is a type of poorly characterized fluid-phase endocytosis which results in formation of relatively large vesicles. We report that Sonic hedgehog (Shh) protein induces macropinocytosis in the axons, through activation of a noncanonical signaling pathway including Rho GTPase and nonmuscle myosin II. Macropinocytosis induced by Shh is independent of clathrin-mediated endocytosis, but dependent on dynamin, myosin II and Rho GTPase activities. Inhibitors of macropinocytosis also abolished the negative effects of Shh on axonal growth including growth cone collapse and chemorepulsive axon turning, but not turning per se. On the other hand, activation of myosin II or treatment of phorbol ester induces macropinocytosis in the axons, elicits growth cone collapse and repulsive axon turning. Furthermore, macropinocytosis is also induced by ephrin-A2 and inhibition of dynamin abolished repulsive axon turning induced by ephrin-A2. Macropinocytosis can be induced ex vivo by high Shh, correlating with axon retraction. These results demonstrate that macropinocytosis-mediated membrane trafficking is an important cellular mechanism involved in axon chemorepulsion induced by negative guidance factors. PMID:19710302

  13. 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.

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

    PubMed

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

    2016-09-01

    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. © 2016 Wiley Periodicals, Inc.

  15. Akt2 knock-down reveals its contribution to human lung cancer cell proliferation, growth, motility, invasion and endothelial cell tube formation.

    PubMed

    Attoub, Samir; Arafat, Kholoud; Hammadi, Nasseredine Kamel; Mester, Jan; Gaben, Anne-Marie

    2015-01-01

    The Akt/PKB serine/threonine protein kinase consists of three isoforms: Akt-1, -2 and -3. Their overexpression has been detected in human cancers, but their roles in cancer progression are unclear. We investigated the impact of specific silencing of Akt1 and Akt2 on human lung cancer cell proliferation, colony growth, motility, and invasion in vitro as well as tumor growth in vivo using human Non-Small Cell Lung Cancer cells LNM35, and on the vascular tube formation using HUVEC cells. Although silencing of Akt1 decreased cellular invasion at least in part via COX-2 inhibition, it had almost no effect on cell motility, proliferation, colony formation, and angiogenesis. Transient as well as stable silencing of Akt2 resulted in a strong inhibition of Rb phosphorylation associated with a decrease in cellular proliferation and colony formation, leading to the inhibition of tumor growth in the xenograft model. Silencing of Akt2 also reduced cellular motility and invasion in vitro, presumably via COX-2 inhibition. Moreover, silencing of Akt2 in the HUVEC cells resulted in the inhibition of their spontaneous angiogenic phenotype. Altogether, these results indicate that Akt2 plays an important role in lung cancer progression and can be a promising target for lung cancer therapy. PMID:26234648

  16. Akt2 knock-down reveals its contribution to human lung cancer cell proliferation, growth, motility, invasion and endothelial cell tube formation

    PubMed Central

    Attoub, Samir; Arafat, Kholoud; Kamel Hammadi, Nasseredine; Mester, Jan; Gaben, Anne-Marie

    2015-01-01

    The Akt/PKB serine/threonine protein kinase consists of three isoforms: Akt-1, −2 and −3. Their overexpression has been detected in human cancers, but their roles in cancer progression are unclear. We investigated the impact of specific silencing of Akt1 and Akt2 on human lung cancer cell proliferation, colony growth, motility, and invasion in vitro as well as tumor growth in vivo using human Non-Small Cell Lung Cancer cells LNM35, and on the vascular tube formation using HUVEC cells. Although silencing of Akt1 decreased cellular invasion at least in part via COX-2 inhibition, it had almost no effect on cell motility, proliferation, colony formation, and angiogenesis. Transient as well as stable silencing of Akt2 resulted in a strong inhibition of Rb phosphorylation associated with a decrease in cellular proliferation and colony formation, leading to the inhibition of tumor growth in the xenograft model. Silencing of Akt2 also reduced cellular motility and invasion in vitro, presumably via COX-2 inhibition. Moreover, silencing of Akt2 in the HUVEC cells resulted in the inhibition of their spontaneous angiogenic phenotype. Altogether, these results indicate that Akt2 plays an important role in lung cancer progression and can be a promising target for lung cancer therapy. PMID:26234648

  17. Lysophospholipid receptors LPA1–3 are not required for the inhibitory effects of LPA on mouse retinal growth cones

    PubMed Central

    Birgbauer, Eric; Chun, Jerold

    2016-01-01

    One of the major requirements in the development of the visual system is axonal guidance of retinal ganglion cells toward correct targets in the brain. A novel class of extracellular lipid signaling molecules, lysophospholipids, may serve as potential axon guidance cues. They signal through cognate G protein-coupled receptors, at least some of which are expressed in the visual system. Here we show that in the mouse visual system, a lysophospholipid known as lysophosphatidic acid (LPA) is inhibitory to retinal neurites in vitro when delivered extracellularly, causing growth cone collapse and neurite retraction. This inhibitory effect of LPA is both active in the nanomolar range and specific compared to the related lysophospholipid, sphingosine 1-phosphate (S1P). Knockout mice lacking three of the five known LPA receptors, LPA1–3, continue to display retinal growth cone collapse and neurite retraction in response to LPA, demonstrating that these three receptors are not required for these inhibitory effects and indicating the existence of one or more functional LPA receptors expressed on mouse retinal neurites that can mediate neurite retraction. PMID:26966392

  18. The hippo pathway effector YAP regulates motility, invasion, and castration-resistant growth of prostate cancer cells.

    PubMed

    Zhang, Lin; Yang, Shuping; Chen, Xingcheng; Stauffer, Seth; Yu, Fang; Lele, Subodh M; Fu, Kai; Datta, Kaustubh; Palermo, Nicholas; Chen, Yuanhong; Dong, Jixin

    2015-04-01

    Yes-associated protein (YAP) is an effector of the Hippo tumor suppressor pathway. The functional significance of YAP in prostate cancer has remained elusive. In this study, we first show that enhanced expression of YAP is able to transform immortalized prostate epithelial cells and promote migration and invasion in both immortalized and cancerous prostate cells. We found that YAP mRNA was upregulated in androgen-insensitive prostate cancer cells (LNCaP-C81 and LNCaP-C4-2 cells) compared to the level in androgen-sensitive LNCaP cells. Importantly, ectopic expression of YAP activated androgen receptor signaling and was sufficient to promote LNCaP cells from an androgen-sensitive state to an androgen-insensitive state in vitro, and YAP conferred castration resistance in vivo. Accordingly, YAP knockdown greatly reduced the rates of migration and invasion of LNCaP-C4-2 cells and under androgen deprivation conditions largely blocked cell division in LNCaP-C4-2 cells. Mechanistically, we found that extracellular signal-regulated kinase-ribosomal s6 kinase signaling was downstream of YAP for cell survival, migration, and invasion in androgen-insensitive cells. Finally, immunohistochemistry showed significant upregulation and hyperactivation of YAP in castration-resistant prostate tumors compared to their levels in hormone-responsive prostate tumors. Together, our results identify YAP to be a novel regulator in prostate cancer cell motility, invasion, and castration-resistant growth and as a potential therapeutic target for metastatic castration-resistant prostate cancer (CRPC).

  19. A Mechanism for the Polarity Formation of Chemoreceptors at the Growth Cone Membrane for Gradient Amplification during Directional Sensing

    PubMed Central

    Bouzigues, Cedric; Holcman, David; Dahan, Maxime

    2010-01-01

    Accurate response to external directional signals is essential for many physiological functions such as chemotaxis or axonal guidance. It relies on the detection and amplification of gradients of chemical cues, which, in eukaryotic cells, involves the asymmetric relocalization of signaling molecules. How molecular events coordinate to induce a polarity at the cell level remains however poorly understood, particularly for nerve chemotaxis. Here, we propose a model, inspired by single-molecule experiments, for the membrane dynamics of GABA chemoreceptors in nerve growth cones (GCs) during directional sensing. In our model, transient interactions between the receptors and the microtubules, coupled to GABA-induced signaling, provide a positive-feedback loop that leads to redistribution of the receptors towards the gradient source. Using numerical simulations with parameters derived from experiments, we find that the kinetics of polarization and the steady-state polarized distribution of GABA receptors are in remarkable agreement with experimental observations. Furthermore, we make predictions on the properties of the GC seen as a sensing, amplification and filtering module. In particular, the growth cone acts as a low-pass filter with a time constant ∼10 minutes determined by the Brownian diffusion of chemoreceptors in the membrane. This filtering makes the gradient amplification resistent to rapid fluctuations of the external signals, a beneficial feature to enhance the accuracy of neuronal wiring. Since the model is based on minimal assumptions on the receptor/cytoskeleton interactions, its validity extends to polarity formation beyond the case of GABA gradient sensing. Altogether, it constitutes an original positive-feedback mechanism by which cells can dynamically adapt their internal organization to external signals. PMID:20179770

  20. Matriptase is required for the active form of hepatocyte growth factor induced Met, focal adhesion kinase and protein kinase B activation on neural stem/progenitor cell motility.

    PubMed

    Fang, Jung-Da; Lee, Sheau-Ling

    2014-07-01

    Hepatocyte growth factor (HGF) is a chemoattractant and inducer for neural stem/progenitor (NS/P) cell migration. Although the type II transmembrane serine protease, matriptase (MTP) is an activator of the latent HGF, MTP is indispensable on NS/P cell motility induced by the active form of HGF. This suggests that MTP's action on NS/P cell motility involves mechanisms other than proteolytic activation of HGF. In the present study, we investigate the role of MTP in HGF-stimulated signaling events. Using specific inhibitors of phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt) or focal adhesion kinase (FAK), we demonstrated that in NS/P cells HGF-activated c-Met induces PI3k-Akt signaling which then leads to FAK activation. This signaling pathway ultimately induces MMP2 expression and NS/P cell motility. Knocking down of MTP in NS/P cells with specific siRNA impaired HGF-stimulation of c-Met, Akt and FAK activation, blocked HGF-induced production of MMP2 and inhibited HGF-stimulated NS/P cell motility. MTP-knockdown NS/P cells cultured in the presence of recombinant protein of MTP protease domain or transfected with the full-length wild-type but not the protease-defected MTP restored HGF-responsive events in NS/P cells. In addition to functioning as HGF activator, our data revealed novel function of MTP on HGF-stimulated c-Met signaling activation.

  1. 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

  2. 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.

  3. 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.

  4. Further characterization of [3H]gamma-aminobutyric acid release from isolated neuronal growth cones: role of intracellular Ca2+ stores.

    PubMed

    Lockerbie, R O; Gordon-Weeks, P R

    1986-04-01

    We have recently shown that growth cones isolated from neonatal rat forebrain possess uptake and release mechanisms for the neurotransmitter gamma-aminobutyric acid. About half of the K+-induced release of [3H]gamma-aminobutyric acid from isolated growth cones is dependent on extracellular Ca2+. The remaining component of the [3H]gamma-aminobutyric acid release is unaffected by removal of extracellular Ca2+ and is resistant to blockade by the voltage-sensitive Ca2+-channel blocker methoxyverapamil. In the present series of experiments we have used caffeine to assess the possible role of intracellular stores of Ca2+ in supporting that component of the K+-induced release of [3H]gamma-aminobutyric acid from isolated growth cones that is independent of extracellular Ca2+. We have chosen caffeine because of its well established effect of releasing Ca2+ from smooth endoplasmic reticulum in muscle. We found that caffeine can release [3H]gamma-aminobutyric acid from isolated growth cones. This effect persists in Ca2+-free medium, in the presence of methoxyverapamil and in the absence of Na+. Furthermore, isobutylmethylxanthine could not substitute for caffeine suggesting that the caffeine effect is not due to phosphodiesterase inhibition and the subsequent rise in intracellular cyclic nucleotides. A combination of the mitochondrial poisons, Antimycin A and sodium azide had no effect on the release of [3H]gamma-aminobutyric acid induced either by caffeine or by high K+. We conclude that caffeine causes the release of Ca2+ from a non-mitochondrial store within the growth cone and that this Ca2+ store supports that component of the K+-induced release of [3H]gamma-aminobutyric acid that is independent of extracellular Ca2+.

  5. 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

  6. Peroxisome proliferator-activated receptor γ agonist efatutazone impairs transforming growth factor β2-induced motility of epidermal growth factor receptor tyrosine kinase inhibitor-resistant lung cancer cells.

    PubMed

    Serizawa, Masakuni; Murakami, Haruyasu; Watanabe, Masaru; Takahashi, Toshiaki; Yamamoto, Nobuyuki; Koh, Yasuhiro

    2014-06-01

    Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) are effective for non-small cell lung cancers (NSCLC) with EGFR-activating mutations. However, most responders develop resistance. Efatutazone, a novel peroxisome proliferator-activated receptor gamma (PPARγ) agonist, is currently under clinical evaluation; it has antiproliferative effects and induces cellular morphological changes and differentiation. The present study investigated the effects of efatutazone in EGFR-TKI-resistant NSCLC cells, while focusing on cell motility. The PC-9-derived NSCLC cell lines PC-9ER and PC-9ZD, resistant to EGFR-TKI due to v-crk avian sarcoma virus CT10 oncogene homolog-like (CRKL) amplification-induced phosphatidylinositol 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homolog (AKT) activation and an EGFR T790M mutation, respectively, were used. These cells exhibit enhanced cell motility due to transforming growth factor β (TGF-β)/Smad2 family member 2 (Smad2) pathway activation. Efatutazone had no growth-inhibitory effect on the tested cells but inhibited the motility of EGFR-TKI-resistant cells in wound closure and transwell assays. Efatutazone plus erlotinib treatment provided greater inhibition of PC-9ER cell migration than efatutazone or erlotinib alone. Efatutazone suppressed increased TGF-β2 secretion from both cell lines (shown by ELISA) and downregulation of TGF-β2 transcription (observed by quantitative RT-PCR). Immunoblot analysis and luciferase assays revealed that efatutazone suppressed Smad2 phosphorylation and its transcriptional activity. These results suggest that efatutazone inhibits cell motility by antagonizing the TGF-β/Smad2 pathway and effectively prevents metastasis in NSCLC patients with acquired resistance to EGFR-TKI regardless of the resistance mechanism.

  7. 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.

  8. Live visualization of protein synthesis in axonal growth cones by microinjection of photoconvertible Kaede into Xenopus embryos

    PubMed Central

    Leung, Kin-Mei; Holt, Christine E

    2013-01-01

    Photoconvertible fluorescent proteins, such as Kaede, can be switched irreversibly from their native color to a new one. This property can be exploited to visualize de novo mRNA translation, because newly synthesized proteins can be distinguished from preexisting ones by their color. In this protocol, Kaede cDNA linked to the 3′ untranslated region (UTR) of β-actin is delivered into cells fated to become the retina by injection into Xenopus blastomeres. Brief exposure (6–10 s) to UV light (350–410 nm) of Kaede-positive retinal axons/growth cones efficiently converts Kaede from its native green fluorescence to red. The reappearance of the green signal reports the synthesis of new Kaede protein. This approach can be used to investigate the spatiotemporal control of translation of specific mRNAs in response to external stimuli and to test the efficiency of full-length versus mutant UTRs. The 3-d protocol can be adapted for broad use with other photoactivatable fluorescent proteins. PMID:18714300

  9. Filopodial actin bundles are not necessary for microtubule advance into the peripheral domain of Aplysia neuronal growth cones.

    PubMed

    Burnette, Dylan T; Schaefer, Andrew W; Ji, Lin; Danuser, Gaudenz; Forscher, Paul

    2007-12-01

    Filopodial actin bundles guide microtubule assembly in the growth cone peripheral (P) domain and retrograde actin-network flow simultaneously transports microtubules rearward. Therefore, microtubule-end position is determined by the sum of microtubule assembly and retrograde transport rates. However, how filopodia actually affect microtubule assembly dynamics is unknown. To address this issue we quantitatively assessed microtubule and actin dynamics before and after selective removal of filopodia. Filopodium removal had surprisingly little effect on retrograde actin-flow rates or underlying network structures, but resulted in an approximate doubling of peripheral microtubule density and deeper penetration of microtubules into the P domain. The latter stemmed from less efficient coupling of microtubules to remaining actin networks and not from a change in microtubule polymer dynamics. Loss of filopodia also resulted in increased lateral microtubule movements and a more randomized microtubule distribution in the P domain. In summary, filopodia do not seem to be formally required for microtubule advance; however, their presence ensures radial distribution of microtubules in the P domain and facilitates microtubule transport by retrograde flow. The resulting dynamic steady state has interesting implications for rapid microtubule-positioning responses in the P domain.

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

    PubMed

    Azriel, Shalhevet; Goren, Alina; Rahav, Galia; Gal-Mor, Ohad

    2015-11-09

    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.

  11. 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

  12. MicroRNA networks regulated by all-trans retinoic acid and Lapatinib control the growth, survival and motility of breast cancer cells

    PubMed Central

    Kurosaki, Mami; Paroni, Gabriela; Zanetti, Adriana; Gianni, Maurizio; Bolis, Marco; Lupi, Monica; Tsykin, Anna; Goodall, Gregory J.; Garattini, Enrico

    2015-01-01

    SKBR3-cells, characterized by ERBB2/RARA co-amplification, represent a subgroup of HER2+ breast-cancers sensitive to all-trans retinoic acid (ATRA) and Lapatinib. In this model, the two agents alone or in combination modulate the expression of 174 microRNAs (miRs). These miRs and predicted target-transcripts are organized in four interconnected modules (Module-1 to -4). Module-1 and Module-3 consist of ATRA/Lapatinib up-regulated and potentially anti-oncogenic miRs, while Module-2 contains ATRA/Lapatinib down-regulated and potentially pro-oncogenic miRs. Consistent with this, the expression levels of Module-1/-3 and Module-2 miRs are higher and lower, respectively, in normal mammary tissues relative to ductal-carcinoma-in-situ, invasive-ductal-carcinoma and metastases. This indicates associations between tumor-progression and the expression profiles of Module-1 to -3 miRs. Similar associations are observed with tumor proliferation-scores, staging, size and overall-survival using TCGA (The Cancer Genome Atlas) data. Forced expression of Module-1 miRs, (miR-29a-3p; miR-874-3p) inhibit SKBR3-cell growth and Module-3 miRs (miR-575; miR-1225-5p) reduce growth and motility. Module-2 miRs (miR-125a; miR-193; miR-210) increase SKBR3 cell growth, survival and motility. Some of these effects are of general significance, being replicated in other breast cancer cell lines representing the heterogeneity of this disease. Finally, our study demonstrates that HIPK2-kinase and the PLCXD1-phospholipase-C are novel targets of miR-193a-5p/miR-210-3p and miR-575/miR-1225-5p, respectively. PMID:25961594

  13. HMGB1 induces the overexpression of miR-222 and miR-221 and increases growth and motility in papillary thyroid cancer cells.

    PubMed

    Mardente, Stefania; Mari, Emanuela; Consorti, Fabrizio; Di Gioia, Cira; Negri, Rodolfo; Etna, Marilena; Zicari, Alessandra; Antonaci, Alfredo

    2012-12-01

    Experimental and epidemiological studies have revealed that chronic inflammation contributes to cancer progression and even predisposes to cellular transformation. Inflammatory infiltrates in papillary thyroid cancer include lymphocytes, macrophages and cytokines. High-mobility group box 1 protein (HMGB1) is a late inflammatory cytokine that signals danger to the immune system through the receptor for advanced glycation end-products (RAGE) and Toll-like receptor. The activation of the above receptors results in the secretion of growth, chemotactic and angiogenic factors that contribute to chronic inflammation. In this study, we suggest that apart from the activation of signal transduction pathways by the activation of RAGE, the indirect inhibition of cell cycle regulators [such as phosphatase and tensin homolog (PTEN)] may also cause an increase in cell growth and motility. MicroRNAs (miRNAs) have increasingly been implicated in regulating the malignant progression of cancer. MiR-221 and miR-222 have been found to be deregulated in human papillary thyroid carcinomas. They are involved in cell proliferation through the inhibition of the cell cycle regulator, p27kip1, in human papillary carcinomas. In this study, we show that HMGB1 increases the expression of miR-221 and miR-222 in primary cultures of excised papillary lesions and in an established papillary cancer cell line (BC PAP). The overexpression of oncogenic miR-221 and miR-222 caused by HMGB1 is associated with an increase in malignancy scores, namely cell growth and motility.

  14. gamma-Aminobutyric acidA (GABAA) receptors modulate [3H]GABA release from isolated neuronal growth cones in the rat.

    PubMed

    Lockerbie, R O; Gordon-Weeks, P R

    1985-04-19

    Potassium-induced release of gamma-[3H]aminobutyric acid [( 3H]GABA) from a growth cone-enriched fraction isolated from neonatal rat forebrain was inhibited by the GABA mimetic muscimol in a dose-dependent manner (IC50 15 nM). The GABA antagonist bicuculline completely reversed the effect of muscimol. Bicuculline alone slightly potentiated the K+-induced release of [3H]GABA. Baclofen, a proposed selective agonist for a bicuculline-insensitive GABAB receptor, was found to cause only a slight reduction in the K+-induced release of [3H]GABA. These results are compatible with the presence of a negative feedback mechanism mediated by GABAA receptors for controlling [3H]GABA release from growth cones of the developing rat forebrain.

  15. Rab11a differentially modulates epidermal growth factor-induced proliferation and motility in immortal breast cells.

    PubMed

    Palmieri, Diane; Bouadis, Amina; Ronchetti, Ruban; Merino, Maria J; Steeg, Patricia S

    2006-11-01

    The development of cancer prevention strategies depends on the elucidation of molecular pathways underlying oncogenesis. In a previous proteomic study of matched normal breast ducts and Ductal Carcinoma in Situ (DCIS), we identified overexpression of Rab11a in DCIS. Rab11a is not well studied in cancer, but is known to regulate the recycling of internalized cell surface proteins and receptors from the early endosome through the trans-Golgi network. Using immunohistochemistry, we confirmed our observation, noting increased Rab11a expression in 19 of 22 (86%) DCIS cases compared to matched normal breast epithelium. To study the function of Rab11a, immortal, nontumorigenic MCF10A breast cells were stimulated with ligands to the EGF receptor (EGFR) after transfection with empty vector (control), Rab11a, or a S25N dominant-negative (DN) Rab11a. Using an iodinated ligand:receptor recycling assay, transfection of Rab11a accelerated, while DN-Rab11a postponed EGFR recycling in vitro. The signaling and in vitro phenotypic consequences of Rab11a expression and function were studied. Transfection of DN-Rab11a increased Erk1/2 activation downstream of EGF, but exerted no effect on the Akt pathway. Expression of DN-Rab11a inhibited MCF10A proliferation by 50-60%, and also inhibited anchorage-dependent colonization. Notably, DN-Rab11a transfection increased motility toward EGFR ligands. The data provide a first demonstration that Rab11a modulates EGFR recycling, and promotes the proliferation but inhibits the motility of an immortal breast line, consistent with the DCIS phenotype.

  16. 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

  17. 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.

  18. Optogenetic Control of PIP3: PIP3 Is Sufficient to Induce the Actin-Based Active Part of Growth Cones and Is Regulated via Endocytosis

    PubMed Central

    Kakumoto, Toshiyuki; Nakata, Takao

    2013-01-01

    Phosphatidylinositol-3,4,5-trisphosphate (PIP3) is highly regulated in a spatiotemporal manner and plays multiple roles in individual cells. However, the local dynamics and primary functions of PIP3 in developing neurons remain unclear because of a lack of techniques for manipulating PIP3 spatiotemporally. We addressed this issue by combining optogenetic control and observation of endogenous PIP3 signaling. Endogenous PIP3 was abundant in actin-rich structures such as growth cones and “waves”, and PIP3-rich plasma membranes moved actively within growth cones. To study the role of PIP3 in developing neurons, we developed a PI3K photoswitch that can induce production of PIP3 at specific locations upon blue light exposure. We succeeded in producing PIP3 locally in mouse hippocampal neurons. Local PIP3 elevation at neurite tips did not induce neurite elongation, but it was sufficient to induce the formation of filopodia and lamellipodia. Interestingly, ectopic PIP3 elevation alone activated membranes to form actin-based structures whose behavior was similar to that of growth-cone-like “waves”. We also found that endocytosis regulates effective PIP3 concentration at plasma membranes. These results revealed the local dynamics and primary functions of PIP3, providing fundamental information about PIP3 signaling in neurons. PMID:23951027

  19. 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

  20. 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.

  1. Dual Role of Herpes Simplex Virus 1 pUS9 in Virus Anterograde Axonal Transport and Final Assembly in Growth Cones in Distal Axons

    PubMed Central

    Boadle, Ross A.

    2015-01-01

    ABSTRACT The herpes simplex virus type 1 (HSV-1) envelope protein pUS9 plays an important role in virus anterograde axonal transport and spread from neuronal axons. In this study, we used both confocal microscopy and transmission electron microscopy (TEM) to examine the role of pUS9 in the anterograde transport and assembly of HSV-1 in the distal axon of human and rat dorsal root ganglion (DRG) neurons using US9 deletion (US9−), repair (US9R), and wild-type (strain F, 17, and KOS) viruses. Using confocal microscopy and single and trichamber culture systems, we observed a reduction but not complete block in the anterograde axonal transport of capsids to distal axons as well as a marked (∼90%) reduction in virus spread from axons to Vero cells with the US9 deletion viruses. Axonal transport of glycoproteins (gC, gD, and gE) was unaffected. Using TEM, there was a marked reduction or absence of enveloped capsids, in varicosities and growth cones, in KOS strain and US9 deletion viruses, respectively. Capsids (40 to 75%) in varicosities and growth cones infected with strain 17, F, and US9 repair viruses were fully enveloped compared to less than 5% of capsids found in distal axons infected with the KOS strain virus (which also lacks pUS9) and still lower (<2%) with the US9 deletion viruses. Hence, there was a secondary defect in virus assembly in distal axons in the absence of pUS9 despite the presence of key envelope proteins. Overall, our study supports a dual role for pUS9, first in anterograde axonal transport and second in virus assembly in growth cones in distal axons. IMPORTANCE HSV-1 has evolved mechanisms for its efficient transport along sensory axons and subsequent spread from axons to epithelial cells after reactivation. In this study, we show that deletion of the envelope protein pUS9 leads to defects in virus transport along axons (partial defect) and in virus assembly and egress from growth cones (marked defect). Virus assembly and exit in the neuronal

  2. 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. PMID:26241851

  3. 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.

  4. 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.

  5. Antihuman epidermal growth factor receptor 2 antibody herceptin inhibits autocrine motility factor (AMF) expression and potentiates antitumor effects of AMF inhibitors.

    PubMed

    Talukder, Amjad H; Bagheri-Yarmand, Rozita; Williams, Ruth R E; Ragoussis, Jiannis; Kumar, Rakesh; Raz, Avraham

    2002-10-01

    Overexpression of the human epidermal growth factor receptor (HER) 2 has been linked to the development and maintenance of malignant phenotypes in breast tumors. In addition, the growth and dissemination of human cancers are regulated in part by the autocrine motility factor (AMF)/phosphoglucose isomerase shown to be up-regulated by heregulin (HRG) in breast cancer cells. This study was undertaken to explore the effect of anti-HER2 monoclonal antibody 4D5 [Herceptin (HCT)] on AMF expression and the potential of its augmentation by specific simple sugar AMF inhibitors. Here we show that HCT treatment of high HER2-expressing breast cancer SK-BR3, BT-474, and ZR-75R cells resulted in down-regulation of AMF mRNA and protein. HCT inhibited the ability of HRG to induce AMF expression in cells with a normal HER2 level, and HCT-mediated down-regulation could be reversed by HRG treatment in breast cancer cells with a high HER2 level. HCT also inhibited transcription from a chimeric pGL3-Luc vector-based reporter system containing the 1.8-kb promoter region of human AMF. Treatment of breast cancer cells with the combination of HCT and specific AMF inhibitors, erythrose 4-phosphate or D-mannose 6-phosphate, resulted in an additive inhibitory effect on both the growth rate and invasiveness of cells as compared with treatment with each agent alone. Results presented here suggest that HCT can effectively block both ligand-induced and constitutive expression of AMF associated with high HER2 overexpression, implying a role of the AMF pathway in the action of HCT. Accordingly, the combination of AMF inhibitor with HCT can potentiate the growth-inhibitory and anti-invasive action of HCT in breast cancer cells.

  6. 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.

  7. Sliding Motility in Mycobacteria

    PubMed Central

    Martínez, Asunción; Torello, Sandra; Kolter, Roberto

    1999-01-01

    Mycobacteria are nonflagellated gram-positive microorganisms. Previously thought to be nonmotile, we show here that Mycobacterium smegmatis can spread on the surface of growth medium by a sliding mechanism. M. smegmatis spreads as a monolayer of cells which are arranged in pseudofilaments by close cell-to-cell contacts, predominantly along their longitudinal axis. The monolayer moves away from the inoculation point as a unit with only minor rearrangements. No extracellular structures such as pili or fimbriae appear to be involved in this process. The ability to translocate over the surface correlates with the presence of glycopeptidolipids, a mycobacterium-specific class of amphiphilic molecules located in the outermost layer of the cell envelope. We present evidence that surface motility is not restricted to M. smegmatis but is also a property of the slow-growing opportunistic pathogen M. avium. This form of motility could play an important role in surface colonization by mycobacteria in the environment as well as in the host. PMID:10572138

  8. Knockdown of Slit2 promotes growth and motility in gastric cancer cells via activation of AKT/β-catenin.

    PubMed

    Shi, Rongliang; Yang, Zhen; Liu, Weiyan; Liu, Bingya; Xu, Ziping; Zhang, Ziping

    2014-02-01

    We previously showed that Slit2 was highly expressed in gastric cancer tissues that exhibit less advanced clinicopathological features, suggesting a tumor suppressor role for Slit2. In the present study, we investigated the effects of Slit2 knockdown on gastric cancer cells. Slit2-specific shRNAs were used to generate Slit2-knockdown SGC-7901 gastric cancer cells. Cell proliferation assay, Annexin V/PI double staining and cell cycle analysis were used to investigate the role of Slit2 knockdown in cell growth. Wound-healing and in vitro migration/invasion assays were performed. Subcutaneous tumor formation and peritoneal spreading in nude mice were employed to examine the in vivo effects of Slit2 knockdown. Cell signaling changes induced by Slit2 knockdown were analyzed by immunoblotting. Slit2 knockdown increased gastric cancer cell growth in monolayer and soft agar/Matrigel 3D culture. Slit2 knockdown inhibited apoptosis but did not alter cell cycle progression. Slit2-knockdown cells formed larger tumors and produced more peritoneal metastatic nodules in nude mice. Slit2 knockdown increased AKT phosphorylation, activated anti-apoptotic signaling, suppressed GSK3β activity and induced β-catenin activation. Blocking the effects of PI3K/AKT using pharmacological inhibitors abolished the ability of Slit2 knockdown to induce apoptosis resistance and cell migration/invasion. These results indicate that Slit2 knockdown promotes gastric cancer growth and metastasis through activation of the AKT/β‑catenin-mediated signaling pathway.

  9. FAP-α (Fibroblast activation protein-α) is involved in the control of human breast cancer cell line growth and motility via the FAK pathway

    PubMed Central

    2014-01-01

    Background Fibroblast Activation Protein alpha (FAP-α) or seprase is an integral membrane serine peptidase. Previous work has not satisfactorily explained both the suppression and promotion effects that have been observed in cancer. The purpose of this work was to investigate the role of FAP-α in human breast cancer. Expression of FAP-α was characterized in primary tumour samples and in cell lines, along with the effects of FAP-α expression on in vitro growth, invasion, attachment and migration. Furthermore the potential interaction of FAP-α with other signalling pathways was investigated. Results FAP-α was significantly increased in patients with poor outcome and survival. In vitro results showed that breast cancer cells over expressing FAP-α had increased growth ability and impaired migratory ability. The growth of MDA-MB-231 cells and the adhesion and invasion ability of both MCF-7 cells and MDA-MB-231 cells were not dramatically influenced by FAP-α expression. Over-expression of FAP-α resulted in a reduction of phosphorylated focal adhesion kinase (FAK) level in both cells cultured in normal media and serum-free media. An inhibitor to FAK restored the reduced motility ability of both MCF-7exp cells and MDA-MB-231exp cells and prevented the change in phosphorylated FAK levels. However, inhibitors to PI3K, ERK, PLCϒ, NWASP, ARP2/3, and ROCK had no influence this. Conclusions FAP-α in significantly associated with poor outcome in patients with breast cancer. In vitro, FAP-α promotes proliferation and inhibits migration of breast cancer cells, potentially by regulating the FAK pathway. These results suggest FAP-α could be a target for future therapies. PMID:24885257

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

    PubMed Central

    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

    2015-01-01

    ABSTRACT 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. © 2015 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals, Inc. J. Cell. Biochem. 116: 2408–2418, 2015. © 2015 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals, Inc. PMID:26012576

  11. EGFR inhibition in glioma cells modulates Rho signaling to inhibit cell motility and invasion and cooperates with temozolomide to reduce cell growth.

    PubMed

    Ramis, Guillem; Thomàs-Moyà, Elena; Fernández de Mattos, Silvia; Rodríguez, José; Villalonga, Priam

    2012-01-01

    Enforced EGFR activation upon gene amplification and/or mutation is a common hallmark of malignant glioma. Small molecule EGFR tyrosine kinase inhibitors, such as erlotinib (Tarceva), have shown some activity in a subset of glioma patients in recent trials, although the reported data on the cellular basis of glioma cell responsiveness to these compounds have been contradictory. Here we have used a panel of human glioma cell lines, including cells with amplified or mutant EGFR, to further characterize the cellular effects of EGFR inhibition with erlotinib. Dose-response and cellular growth assays indicate that erlotinib reduces cell proliferation in all tested cell lines without inducing cytotoxic effects. Flow cytometric analyses confirm that EGFR inhibition does not induce apoptosis in glioma cells, leading to cell cycle arrest in G(1). Interestingly, erlotinib also prevents spontaneous multicellular tumour spheroid growth in U87MG cells and cooperates with sub-optimal doses of temozolomide (TMZ) to reduce multicellular tumour spheroid growth. This cooperation appears to be schedule-dependent, since pre-treatment with erlotinib protects against TMZ-induced cytotoxicity whereas concomitant treatment results in a cooperative effect. Cell cycle arrest in erlotinib-treated cells is associated with an inhibition of ERK and Akt signaling, resulting in cyclin D1 downregulation, an increase in p27(kip1) levels and pRB hypophosphorylation. Interestingly, EGFR inhibition also perturbs Rho GTPase signaling and cellular morphology, leading to Rho/ROCK-dependent formation of actin stress fibres and the inhibition of glioma cell motility and invasion.

  12. 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

  13. The Rat Homolog of the Schizophrenia Susceptibility Gene ZNF804A Is Highly Expressed during Brain Development, Particularly in Growth Cones.

    PubMed

    Hinna, Katja Hvid; Rich, Karen; Fex-Svenningsen, Åsa; Benedikz, Eirikur

    2015-01-01

    A single nucleotide polymorphism in the ZNF804A gene, rs1344706, is associated with schizophrenia. The polymorphism has been suggested to alter fetal expression of ZNF804A. It has also been reported to be associated with altered cortical functioning and neural connectivity in the brain. Since developmental mechanisms are suggested in the pathophysiology for schizophrenia, expression of Zfp804A, the rat homolog of ZNF804A, was investigated in the developing rat brain. We found that expression of Zfp804A in most brain regions is developmentally regulated and peaks around birth, where after it decreases towards adult levels. This time point is developmentally the equivalent to the second trimester of fetal development in humans. An exception to this expression pattern is the hippocampus where the expression of Zfp804A appears to increase again in the adult brain. Using laser capture and quantitative PCR we found that Zfp804A mRNA expression in the adult rat hippocampus is highest in the CA1 sub region, where the overall firing rates of neurons is higher than in the CA3 region. In cultured cortical neurons Zfp804A mRNA expression peaked at day 4 and then decreased. The ZFP804A protein expression was therefore investigated with immunochemistry in such cultures. Interestingly, before day 4, the protein is mostly found in the perinuclear region of the cell but at day 4, ZFP804A was instead found throughout the cell and particularly in the growth cones. In conclusion we demonstrate that Zfp804A increases in the rat brain at the time of birth, coinciding with neuronal differentiation. We also show that ZFP804A is localized to growth cones of growing neurites. These data implicate ZFP804A in growth cone function and neurite elongation. The polymorphism rs1344706 lowers expression of ZNF804A during prenatal brain development. This may affect ZNF804A's role in cone function and neurite elongation leading to synaptic deficits and altered neural connectivity.

  14. The Rat Homolog of the Schizophrenia Susceptibility Gene ZNF804A Is Highly Expressed during Brain Development, Particularly in Growth Cones

    PubMed Central

    Hinna, Katja Hvid; Rich, Karen; Fex-Svenningsen, Åsa; Benedikz, Eirikur

    2015-01-01

    A single nucleotide polymorphism in the ZNF804A gene, rs1344706, is associated with schizophrenia. The polymorphism has been suggested to alter fetal expression of ZNF804A. It has also been reported to be associated with altered cortical functioning and neural connectivity in the brain. Since developmental mechanisms are suggested in the pathophysiology for schizophrenia, expression of Zfp804A, the rat homolog of ZNF804A, was investigated in the developing rat brain. We found that expression of Zfp804A in most brain regions is developmentally regulated and peaks around birth, where after it decreases towards adult levels. This time point is developmentally the equivalent to the second trimester of fetal development in humans. An exception to this expression pattern is the hippocampus where the expression of Zfp804A appears to increase again in the adult brain. Using laser capture and quantitative PCR we found that Zfp804A mRNA expression in the adult rat hippocampus is highest in the CA1 sub region, where the overall firing rates of neurons is higher than in the CA3 region. In cultured cortical neurons Zfp804A mRNA expression peaked at day 4 and then decreased. The ZFP804A protein expression was therefore investigated with immunochemistry in such cultures. Interestingly, before day 4, the protein is mostly found in the perinuclear region of the cell but at day 4, ZFP804A was instead found throughout the cell and particularly in the growth cones. In conclusion we demonstrate that Zfp804A increases in the rat brain at the time of birth, coinciding with neuronal differentiation. We also show that ZFP804A is localized to growth cones of growing neurites. These data implicate ZFP804A in growth cone function and neurite elongation. The polymorphism rs1344706 lowers expression of ZNF804A during prenatal brain development. This may affect ZNF804A’s role in cone function and neurite elongation leading to synaptic deficits and altered neural connectivity. PMID:26148198

  15. The scaffolding protein NHERF1 sensitizes EGFR-dependent tumor growth, motility and invadopodia function to gefitinib treatment in breast cancer cells.

    PubMed

    Bellizzi, Antonia; Greco, Maria Raffaella; Rubino, Rosa; Paradiso, Angelo; Forciniti, Stefania; Zeeberg, Katrine; Cardone, Rosa Angela; Reshkin, Stephan Joel

    2015-03-01

    Triple negative breast cancer (TNBC) patients cannot be treated with endocrine therapy or targeted therapies due to lack of related receptors. These patients overexpress the epidermal growth factor receptor (EGFR), but are resistant to tyrosine kinase inhibitors (TKIs) and anti-EGFR therapies. Mechanisms suggested for resistance to TKIs include EGFR independence, mutations and alterations in EGFR and in its downstream signalling pathways. Ligand-induced endocytosis and degradation of EGFR play important roles in the downregulation of the EGFR signal suggesting that its activity could be regulated by targeting its trafficking. Evidence in normal cells showing that the scaffolding protein Na+/H+ exchanger regulatory factor 1 (NHERF1) can associate with EGFR to regulate its trafficking, led us to hypothesize that NHERF1 expression levels could regulate EGFR trafficking and functional expression in TNBC cells and, in this way, modulate its role in progression and response to treatment. We investigated the subcellular localization of NHERF1 and its interaction with EGFR in a metastatic basal like TNBC cell model, MDA-MB‑231, and the role of forced NHERF1 overexpression and/or stimulation with EGF on the sensitivity to EGFR specific TKI treatment with gefitinib. Stimulation with EGF induces an interaction of NHERF1 with EGFR to regulate its localization, degradation and function. NHERF1 overexpression is sufficient to drive its interaction with EGFR in non-stimulated conditions, inhibits EGFR degradation and increases its retention time in the plasma membrane. Importantly, NHERF1 overexpression strongly sensitized the cell to the pharmacological inhibition by gefitinib of EGFR-driven growth, motility and invadopodia-dependent ECM proteolysis. The further determination of how the NHERF1‑EGFR interaction is regulated may improve our understanding of TNBC resistance to the action of existing anticancer drugs.

  16. Insulin-like growth factor binding protein-3 interacts with autocrine motility factor/phosphoglucose isomerase (AMF/PGI) and inhibits the AMF/PGI function.

    PubMed

    Mishra, Suresh; Raz, Avrahram; Murphy, Liam J

    2004-04-01

    Autocrine motility factor/phosphoglucose isomerase (AMF/PGI) was identified as a binding partner for insulin-like growth factor binding protein-3 (IGFBP-3) in solubilized T47D and MCF-7 human breast cancer cell membranes. The interaction between AMF/PGI and IGFBP-3 was verified by cross-linking biotinylated IGFBP-3 to intact cells. After solubilization of the membranes, the biotinylated complexes were precipitated with streptavidin-agarose conjugate and analyzed by SDS-PAGE. A M(r) approximately 80,000 complex was identified when the nitrocellulose membranes were probed either with streptavidin-horseradish peroxidase conjugate or AMF/PGI antiserum confirming the cross-linking of IGFBP-3 to AMF/PGI. The interaction between IGFBP-3 and AMF/PGI was also further confirmed by ligand blotting of purified AMF/PGI using biotinylated IGFBP-3. Both glycosylated and nonglycosylated IGFBP-3 inhibited the catalytic activity of AMF/PGI in a dose-dependent fashion. In addition, IGFBP-3 inhibited the binding of AMF/PGI to breast cancer cells and AMF/PGI-induced migration of both T47D and MCF-7 human breast cancer cells. IGFBP-3 also decreased the phosphorylation of AMF/PGI and reduced the translocation of AMF/PGI to the cell membrane and AMF/PGI. AMF/PGI resulted in a dose-dependent inhibition of IGFBP-3 induced apoptosis in T47D and MCF-7 cells. In summary, we have identified AMF/PGI as a membrane-associated binding partner for IGFBP-3 in breast cancer cells. The ability of IGFBP-3 to bind and inhibit the actions of AMF/PGI may have some role in the antiproliferative proapoptotic effects of IGFBP-3.

  17. All-trans-retinoic Acid Modulates the Plasticity and Inhibits the Motility of Breast Cancer Cells: ROLE OF NOTCH1 AND TRANSFORMING GROWTH FACTOR (TGFβ).

    PubMed

    Zanetti, Adriana; Affatato, Roberta; Centritto, Floriana; Fratelli, Maddalena; Kurosaki, Mami; Barzago, Maria Monica; Bolis, Marco; Terao, Mineko; Garattini, Enrico; Paroni, Gabriela

    2015-07-17

    All-trans-retinoic acid (ATRA) is a natural compound proposed for the treatment/chemoprevention of breast cancer. Increasing evidence indicates that aberrant regulation of epithelial-to-mesenchymal transition (EMT) is a determinant of the cancer cell invasive and metastatic behavior. The effects of ATRA on EMT are largely unknown. In HER2-positive SKBR3 and UACC812 cells, showing co-amplification of the ERBB2 and RARA genes, ATRA activates a RARα-dependent epithelial differentiation program. In SKBR3 cells, this causes the formation/reorganization of adherens and tight junctions. Epithelial differentiation and augmented cell-cell contacts underlie the anti-migratory action exerted by the retinoid in cells exposed to the EMT-inducing factors EGF and heregulin-β1. Down-regulation of NOTCH1, an emerging EMT modulator, is involved in the inhibition of motility by ATRA. Indeed, the retinoid blocks NOTCH1 up-regulation by EGF and/or heregulin-β1. Pharmacological inhibition of γ-secretase and NOTCH1 processing also abrogates SKBR3 cell migration. Stimulation of TGFβ contributes to the anti-migratory effect of ATRA. The retinoid switches TGFβ from an EMT-inducing and pro-migratory determinant to an anti-migratory mediator. Inhibition of the NOTCH1 pathway not only plays a role in the anti-migratory action of ATRA; it is relevant also for the anti-proliferative activity of the retinoid in HCC1599 breast cancer cells, which are addicted to NOTCH1 for growth/viability. This effect is enhanced by the combination of ATRA and the γ-secretase inhibitor N-(N-(3,5-difluorophenacetyl)-l-alanyl)-S-phenylglycine t-butyl ester, supporting the concept that the two compounds act at the transcriptional and post-translational levels along the NOTCH1 pathway. PMID:26018078

  18. All-trans-retinoic Acid Modulates the Plasticity and Inhibits the Motility of Breast Cancer Cells: ROLE OF NOTCH1 AND TRANSFORMING GROWTH FACTOR (TGFβ).

    PubMed

    Zanetti, Adriana; Affatato, Roberta; Centritto, Floriana; Fratelli, Maddalena; Kurosaki, Mami; Barzago, Maria Monica; Bolis, Marco; Terao, Mineko; Garattini, Enrico; Paroni, Gabriela

    2015-07-17

    All-trans-retinoic acid (ATRA) is a natural compound proposed for the treatment/chemoprevention of breast cancer. Increasing evidence indicates that aberrant regulation of epithelial-to-mesenchymal transition (EMT) is a determinant of the cancer cell invasive and metastatic behavior. The effects of ATRA on EMT are largely unknown. In HER2-positive SKBR3 and UACC812 cells, showing co-amplification of the ERBB2 and RARA genes, ATRA activates a RARα-dependent epithelial differentiation program. In SKBR3 cells, this causes the formation/reorganization of adherens and tight junctions. Epithelial differentiation and augmented cell-cell contacts underlie the anti-migratory action exerted by the retinoid in cells exposed to the EMT-inducing factors EGF and heregulin-β1. Down-regulation of NOTCH1, an emerging EMT modulator, is involved in the inhibition of motility by ATRA. Indeed, the retinoid blocks NOTCH1 up-regulation by EGF and/or heregulin-β1. Pharmacological inhibition of γ-secretase and NOTCH1 processing also abrogates SKBR3 cell migration. Stimulation of TGFβ contributes to the anti-migratory effect of ATRA. The retinoid switches TGFβ from an EMT-inducing and pro-migratory determinant to an anti-migratory mediator. Inhibition of the NOTCH1 pathway not only plays a role in the anti-migratory action of ATRA; it is relevant also for the anti-proliferative activity of the retinoid in HCC1599 breast cancer cells, which are addicted to NOTCH1 for growth/viability. This effect is enhanced by the combination of ATRA and the γ-secretase inhibitor N-(N-(3,5-difluorophenacetyl)-l-alanyl)-S-phenylglycine t-butyl ester, supporting the concept that the two compounds act at the transcriptional and post-translational levels along the NOTCH1 pathway.

  19. 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.

  20. 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

  1. 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

  2. T-helper 2 Cytokines, Transforming Growth Factor β1, and Eosinophil Products Induce Fibrogenesis and Alter Muscle Motility in Patients with Eosinophilic Esophagitis

    PubMed Central

    Rieder, Florian; Nonevski, Ilche; Ma, Jie; Ouyang, Zhufeng; West, Gail; Protheroe, Cheryl; DePetris, Giovanni; Schirbel, Anja; Lapinski, James; Goldblum, John; Bonfield, Tracey; Lopez, Rocio; Harnett, Karen; Lee, James; Hirano, Ikuo; Falk, Gary; Biancani, Piero; Fiocchi, Claudio

    2014-01-01

    BACKGROUND & AIMS Patients with eosinophilic esophagitis (EoE) often become dysphagic from the combination of organ fibrosis and motor abnormalities. We investigated mechanisms of dysphagia, assessing the response of human esophageal fibroblasts (HEF), muscle cells (HEMC), and esophageal muscle strips to eosinophil-derived products. METHODS Biopsies were collected via endoscopy from the upper, middle and lower thirds of the esophagus of 18 patients with EoE and 21 individuals undergoing endoscopy for other reasons (controls). Primary cultures of esophageal fibroblasts and muscle cells were derived from 12 freshly resected human esophagectomy specimens. Eosinophil distribution was investigated by histologic analyses of full-thickness esophageal tissue. Active secretion of EoE-related mediators was assessed from medium underlying mucosal biopsy cultures. We quantified production of fibronectin and collagen I by HEF and HEMC in response to eosinophil products. We also measured expression of ICAM1 and VCAM1 by, and adhesion of human eosinophils to, HEF and HEMC. Eosinophil products were tested in an esophageal muscle contraction assay. RESULTS Activated eosinophils were present in all esophageal layers. Significantly higher concentrations of eosinophil-related mediators were spontaneously secreted in mucosal biopsies from patients with EoE than controls. Exposure of HEF and HEMC to increasing concentrations of eosinophil products or co-culture with eosinophils caused HEF and HEMC to increase secretion of fibronectin and collagen I; this was inhibited by blocking transforming growth factor (TGF)β1 and p38 mitogen-activated protein kinase (MAKP) signaling. Eosinophil binding to HEF and HEMC increased following incubation of mesenchymal cells with eosinophil-derived products, and decreased following blockade of TGFβ1 and p38MAPK blockade. Eosinophil products reduced electrical field-induced contraction of esophageal muscle strips, but not acetylcholine

  3. Cytoplasmic mechanisms of axonal and dendritic growth in neurons.

    PubMed

    Heidemann, S R

    1996-01-01

    The structural mechanisms responsible for the gradual elaboration of the cytoplasmic elongation of neurons are reviewed. In addition to discussing recent work, important older work is included to inform newcomers to the field how the current perspective arose. The highly specialized axon and the less exaggerated dendrite both result from the advance of the motile growth cone. In the area of physiology, studies in the last decade have directly confirmed the classic model of the growth cone pulling forward and the axon elongating from this tension. Particularly in the case of the axon, cytoplasmic elongation is closely linked to the formation of an axial microtubule bundle from behind the advancing growth cone. Substantial progress has been made in understanding the expression of microtubule-associated proteins during neuronal differentiation to stiffen and stabilize axonal microtubules, providing specialized structural support. Studies of membrane organelle transport along the axonal microtubules produced an explosion of knowledge about ATPase molecules serving as motors driving material along microtubule rails. However, most aspects of the cytoplasmic mechanisms responsible for neurogenesis remain poorly understood. There is little agreement on mechanisms for the addition of new plasma membrane or the addition of new cytoskeletal filaments in the growing axon. Also poorly understood are the mechanisms that couple the promiscuous motility of the growth cone to the addition of cytoplasmic elements.

  4. Identification and Characterization of a Gene stp17 Located on the Linear Plasmid pBSSB1 as an Enhanced Gene of Growth and Motility in Salmonella enterica Serovar Typhi

    PubMed Central

    Zhang, Haifang; Zhu, Yunxia; Xie, Xiaofang; Wang, Min; Du, Hong; Xu, Shungao; Zhang, Ying; Gong, Mingyu; Ni, Bin; Xu, Huaxi; Huang, Xinxiang

    2016-01-01

    The linear plasmid pBSSB1 mediates the flagellar phase variation in H:z66 positive Salmonella enterica serovar Typhi (S. Typhi). The gene named stp17 (S. Typhi plasmid number 17 gene) is located on pBSSB1 and encodes the protein STP17. The expression pattern at the protein-level and function of STP17 remains unknown. In this study, the recombinant protein STP17His6 was expressed, purified and used to prepare the polyclonal anti-STP17 antibody. We detected protein-level expression of stp17 in S. Typhi and further investigated the protein expression characteristics of stp17 in different growth phases by western blot analysis. The effects of STP17 on bacterial growth and motility were analyzed. In addition, the structure of STP17 was predicted and the active site of STP17 was identified by site-directed mutagenesis. The results showed that STP17 was expressed stably in the wild type strain of S. Typhi. STP17 expression at the protein level peaks when cultures reach an OD600 value of 1.2. The growth rate and motility of the Δstp17 strain were significantly decreased compared with the wild type strain (P < 0.05) and this phenotype was restored in the stp17 complementary strain. Moreover, the growth rate and motility of the stp17 over-expression strain was greater than the wild type strain. STP17 contains nine Helix segments, six Stand segments and some Coil segments in the secondary structural level. The top-ranked 3-D structure of STP17 predicted by I-TASSER contains a putative ATPase domain and the amino acid residues of GLY16, GLY19, LYS20, ASN133, LYS157, and LYS158 may be the active site residues of STP17. Finally, STP17 was able to catalyze the ATP to ADP reaction, suggesting that STP17 may be an ATPase. To our knowledge, this is the first report describing the protein expression characteristics of STP17 in S. Typhi, showing that STP17 promotes bacterial growth and motility, which may be associated with its potential ATPase activity. PMID:27761429

  5. Pediatric intestinal motility disorders

    PubMed Central

    Gfroerer, Stefan; Rolle, Udo

    2015-01-01

    Pediatric intestinal motility disorders affect many children and thus not only impose a significant impact on pediatric health care in general but also on the quality of life of the affected patient. Furthermore, some of these conditions might also have implications for adulthood. Pediatric intestinal motility disorders frequently present as chronic constipation in toddler age children. Most of these conditions are functional, meaning that constipation does not have an organic etiology, but in 5% of the cases, an underlying, clearly organic disorder can be identified. Patients with organic causes for intestinal motility disorders usually present in early infancy or even right after birth. The most striking clinical feature of children with severe intestinal motility disorders is the delayed passage of meconium in the newborn period. This sign is highly indicative of the presence of Hirschsprung disease (HD), which is the most frequent congenital disorder of intestinal motility. HD is a rare but important congenital disease and the most significant entity of pediatric intestinal motility disorders. The etiology and pathogenesis of HD have been extensively studied over the last several decades. A defect in neural crest derived cell migration has been proven as an underlying cause of HD, leading to an aganglionic distal end of the gut. Numerous basic science and clinical research related studies have been conducted to better diagnose and treat HD. Resection of the aganglionic bowel remains the gold standard for treatment of HD. Most recent studies show, at least experimentally, the possibility of a stem cell based therapy for HD. This editorial also includes rare causes of pediatric intestinal motility disorders such as hypoganglionosis, dysganglionosis, chronic intestinal pseudo-obstruction and ganglioneuromatosis in multiple endocrine metaplasia. Underlying organic pathologies are rare in pediatric intestinal motility disorders but must be recognized as early as

  6. Novel mechanisms power bacterial gliding motility.

    PubMed

    Nan, Beiyan; Zusman, David R

    2016-07-01

    For many bacteria, motility is essential for survival, growth, virulence, biofilm formation and intra/interspecies interactions. Since natural environments differ, bacteria have evolved remarkable motility systems to adapt, including swimming in aqueous media, and swarming, twitching and gliding on solid and semi-solid surfaces. Although tremendous advances have been achieved in understanding swimming and swarming motilities powered by flagella, and twitching motility powered by Type IV pili, little is known about gliding motility. Bacterial gliders are a heterogeneous group containing diverse bacteria that utilize surface motilities that do not depend on traditional flagella or pili, but are powered by mechanisms that are less well understood. Recently, advances in our understanding of the molecular machineries for several gliding bacteria revealed the roles of modified ion channels, secretion systems and unique machinery for surface movements. These novel mechanisms provide rich source materials for studying the function and evolution of complex microbial nanomachines. In this review, we summarize recent findings made on the gliding mechanisms of the myxobacteria, flavobacteria and mycoplasmas. PMID:27028358

  7. 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.

  8. Axonemal motility in Chlamydomonas.

    PubMed

    Wakabayashi, Ken-ichi; Kamiya, Ritsu

    2015-01-01

    Motile cilia and flagella rapidly propagate bending waves and produce water flow over the cell surface. Their function is important for the physiology and development of various organisms including humans. The movement is based on the sliding between outer doublet microtubules driven by axonemal dyneins, and is regulated by various axonemal components and environmental factors. For studies aiming to elucidate the mechanism of cilia/flagella movement and regulation, Chlamydomonas is an invaluable model organism that offers a variety of mutants. This chapter introduces standard methods for studying Chlamydomonas flagellar motility including analysis of swimming paths, measurements of swimming speed and beat frequency, motility reactivation in demembranated cells (cell models), and observation of microtubule sliding in disintegrating axonemes. Most methods may be easily applied to other organisms with slight modifications of the medium conditions.

  9. Cell motility on nanotopography

    NASA Astrophysics Data System (ADS)

    Kimura, Masahiro; Tsai, Irene; Green, Angelo; Jacobson, Bruce; Russell, Thomas

    2003-03-01

    Cell motility is strongly influenced by the structure of the substratum. Understanding cells motility on a surface has significant applications both in vivo and in vitro applications, such as biological sensors and hip replacement. A gradient surface is used to study the effect of the lateral nanotopography on cell motility. A gradient surface is generated by block copolymer and homopolymer blends, where the concentration of the components varies uniformly across the surface. The two homopolymers phase separate on the micron scale and this length scale gradually decrease to the nanoscopic, i.e. microphase separation of the diblock, as the copolymer concentration increases. Quantitative analysis of the speed of cell migration is correlated to the lateral length scale of the surface.

  10. [Obesity and gastrointestinal motility].

    PubMed

    Lee, Joon Seong

    2006-08-01

    Gastrointestinal (GI) motility has a crucial role in the food consumption, digestion and absorption, and also controls the appetite and satiety. In obese patients, various alterations of GI motility have been investigated. The prevalence of GERD and esophageal motor disorders in obese patients are higher than those of general population. Gastric emptying of solid food is generally accelerated and fasting gastric volume especially in distal stomach is larger in obese patients without change in accommodation. Contractile activity of small intestine in fasting period is more prominent, but orocecal transit is delayed. Autonomic dysfunction is frequently demonstrated in obese patients. These findings correspond with increased appetite and delayed satiety in obese patients, but causes or results have not been confirmed. Therapeutic interventions of these altered GI motility have been developed using botulinum toxin, gastric electrical stimulation in obese patients. Novel agents targeted for GI hormone modulation (such as ghrelin and leptin) need to be developed in the near future. PMID:16929152

  11. The role of palladin in actin organization and cell motility

    PubMed Central

    Goicoechea, Silvia M.; Arneman, Daniel; Otey, Carol A.

    2008-01-01

    Palladin is a widely expressed protein found in stress fibers, focal adhesions, growth cones, Z-discs, and other actin-based subcellular structures. It belongs to a small gene family that includes the Z-disc proteins myopalladin and myotilin, all of which share similar Ig-like domains. Recent advances have shown that palladin shares with myotilin the ability to bind directly to F-actin, and to crosslink actin filaments into bundles, in vitro. Studies in a variety of cultured cells suggest that the actin-organizing activity of palladin plays a central role in promoting cell motility. Correlative evidence also supports this hypothesis, as palladin levels are typically upregulated in cells that are actively migrating: in developing vertebrate embryos, in cells along a wound edge, and in metastatic cancer cells. Recently, a mutation in the human palladin gene was implicated in an unusually penetrant form of inherited pancreatic cancer, which has stimulated new ideas about the role of palladin in invasive cancer. PMID:18342394

  12. The Caenorhabditis elegans Eph receptor activates NCK and N-WASP, and inhibits Ena/VASP to regulate growth cone dynamics during axon guidance.

    PubMed

    Mohamed, Ahmed M; Boudreau, Jeffrey R; Yu, Fabian P S; Liu, Jun; Chin-Sang, Ian D

    2012-01-01

    The Eph receptor tyrosine kinases (RTKs) are regulators of cell migration and axon guidance. However, our understanding of the molecular mechanisms by which Eph RTKs regulate these processes is still incomplete. To understand how Eph receptors regulate axon guidance in Caenorhabditis elegans, we screened for suppressors of axon guidance defects caused by a hyperactive VAB-1/Eph RTK. We identified NCK-1 and WSP-1/N-WASP as downstream effectors of VAB-1. Furthermore, VAB-1, NCK-1, and WSP-1 can form a complex in vitro. We also report that NCK-1 can physically bind UNC-34/Enabled (Ena), and suggest that VAB-1 inhibits the NCK-1/UNC-34 complex and negatively regulates UNC-34. Our results provide a model of the molecular events that allow the VAB-1 RTK to regulate actin dynamics for axon guidance. We suggest that VAB-1/Eph RTK can stop axonal outgrowth by inhibiting filopodia formation at the growth cone by activating Arp2/3 through a VAB-1/NCK-1/WSP-1 complex and by inhibiting UNC-34/Ena activity.

  13. Gastrointestinal motility revisited: The wireless motility capsule

    PubMed Central

    Farmer, Adam D; Scott, S Mark

    2013-01-01

    Introduction The wireless motility capsule (WMC) is a novel ambulatory technology that concurrently measures intraluminal pH, temperature, and pressure as it traverses the gastrointestinal tract. Objectives We aim to provide a concise summary of the WMC, detailing the procedure for its administration and the parameters it records. We also review the evidence that has validated the WMC against other methods currently regarded as ‘gold standard’. Conclusions The WMC offers a number of advantages over and above current techniques, especially with respect to patient tolerability, safety, and standardization. The WMC represents a considerable enhancement of the researchers’ and clinicians’ investigatory armamentarium. If this technology becomes widely adopted, coupled with international consensus upon the interpretation of physiological data derived therein, it may herald a new and exciting era in gastrointestinal physiology. PMID:24917991

  14. 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.

  15. Flagellar motility confers epiphytic fitness advantages upon Pseudomonas syringae

    SciTech Connect

    Haefele, D.M.; Lindow, S.E.

    1987-10-01

    The role of flagellar motility in determining the epiphytic fitness of an ice-nucleation-active strain of Pseudomonas syringae was examined. The loss of flagellar motility reduced the epiphytic fitness of a normally motile P. syringae strain as measured by its growth, survival, and competitive ability on bean leaf surfaces. Equal population sizes of motile parental or nonmotile mutant P. syringae strains were maintained on bean plants for at least 5 days following the inoculation of fully expanded primary leaves. However, when bean seedlings were inoculated before the primary leaves had expanded and bacterial populations on these leaves were quantified at full expansion, the population size of the nonmotile derivative strain reached only 0.9% that of either the motile parental or revertant strain. When fully expanded bean primary leaves were coinoculated with equal numbers of motile and nonmotile cells, the population size of a nonmotile derivative strain was one-third of that of the motile parental or revertant strain after 8 days. Motile and nonmotile cells were exposed in vitro and on plants to UV radiation and desiccating conditions. The motile and nonmotile strains exhibited equal resistance to both stresses in vitro. However, the population size of a nonmotile strain on leaves was less than 20% that of a motile revertant strain when sampled immediately after UV irradiation. Epiphytic populations of both motile and nonmotile P. syringae declined under desiccating conditions on plants, and after 8 days, the population size of a nonmotile strain was less than one-third that of the motile parental or revertant strain.

  16. Flagellar Motility Confers Epiphytic Fitness Advantages upon Pseudomonas syringae

    PubMed Central

    Haefele, Douglas M.; Lindow, Steven E.

    1987-01-01

    The role of flagellar motility in determining the epiphytic fitness of an ice-nucleation-active strain of Pseudomonas syringae was examined. The loss of flagellar motility reduced the epiphytic fitness of a normally motile P. syringae strain as measured by its growth, survival, and competitive ability on bean leaf surfaces. Equal population sizes of motile parental or nonmotile mutant P. syringae strains were maintained on bean plants for at least 5 days following the inoculation of fully expanded primary leaves. However, when bean seedlings were inoculated before the primary leaves had expanded and bacterial populations on these leaves were quantified at full expansion, the population size of the nonmotile derivative strain reached only 0.9% that of either the motile parental or revertant strain. When fully expanded bean primary leaves were coinoculated with equal numbers of motile and nonmotile cells, the population size of a nonmotile derivative strain was one-third of that of the motile parental or revertant strain after 8 days. Motile and nonmotile cells were exposed in vitro and on plants to UV radiation and desiccating conditions. The motile and nonmotile strains exhibited equal resistance to both stresses in vitro. However, the population size of a nonmotile strain on leaves was less than 20% that of a motile revertant strain when sampled immediately after UV irradiation. Epiphytic populations of both motile and nonmotile P. syringae declined under desiccating conditions on plants, and after 8 days, the population size of a nonmotile strain was less than one-third that of the motile parental or revertant strain. PMID:16347469

  17. The cone dystrophies.

    PubMed

    Simunovic, M P; Moore, A T

    1998-01-01

    The cone dystrophies are a heterogeneous group of inherited disorders that result in dysfunction of the cone photoreceptors and sometimes their post-receptoral pathways. The major clinical features of cone dystrophy are photophobia, reduced visual acuity and abnormal colour vision. Ganzfeld electroretinography shows reduced or absent cone responses. On the basis of their natural history, the cone dystrophies may be broadly divided into two groups: stationary and progressive cone dystrophies. The stationary cone dystrophies have received more attention, and subsequently our knowledge of their molecular genetic, psychophysical and clinical characteristics is better developed. Various methods of classification have been proposed for the progressive cone dystrophies, but none is entirely satisfactory, largely because the underlying disease mechanisms are poorly understood. Multidisciplinary studies involving clinical assessment, molecular genetics, electrophysiology and psychophysics should lead to an improved understanding of the pathogenesis of these disorders.

  18. Cold knife cone biopsy

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003910.htm Cold knife cone biopsy To use the sharing features on this page, please enable JavaScript. A cold knife cone biopsy (conization) is surgery to remove ...

  19. 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.

  20. [Esophageal motility disorders].

    PubMed

    Dughera, L; Battaglia, E; Emanuelli, G

    2001-09-01

    Esophageal motility abnormalities are usually diagnosed when esophageal manometry is performed in patients with unexplained non-cardiac chest pain, non obstructive dysphagia or as a part of the preoperative evaluation for surgery of gastroesophageal reflux. Classification of these abnormalities has been a subject of controversy. These esophageal contraction abnormalities can be separated manometrically from the motor pattern seen in normal subjects, however, their clinical relevance is still unclear and debated. Many patients demonstrate motility abnormalities in the manometry laboratories, but may lack correlation with their presenting symptoms. Medical treatment can decrease symptoms particularly chest pain or acid reflux but there is no significant changes in the manometric patterns. Such motor abnormalities may not reflect a true disease state, but they could be markers of other abnormalities and they can modify the initial manometric findings in time.

  1. An ocular motility conundrum

    PubMed Central

    McElnea, Elizabeth Margaret; Stephenson, Kirk; Lanigan, Bernie; Flitcroft, Ian

    2014-01-01

    Two siblings, an 11-year-old boy and a 7-year-old girl presented with bilateral symmetrical ptosis and limited eye movements. Having already been reviewed on a number of occasions by a variety of specialists in multiple hospital settings a diagnosis of their ocular motility disorder had remained elusive. We describe their cases, outline the differential diagnosis and review the investigations performed which were influential in finally making a diagnosis. PMID:25349186

  2. 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

  3. 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.

  4. High Motility Reduces Grazing Mortality of Planktonic Bacteria

    PubMed Central

    Matz, Carsten; Jürgens, Klaus

    2005-01-01

    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 μm s−1 as a result of handling problems with highly motile cells. Comparative studies of a moderately motile strain (<25 μm s−1) and a highly motile strain (>45 μm 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 μm3. Grazing mortality was lowest for cells of >0.5 μm3 and small, highly motile bacteria. Survival efficiencies of >95% for the ultramicrobacterial isolate CP-1 (≤0.1 μm3, >50 μm 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. PMID:15691949

  5. 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

  6. Early endosome motility spatially organizes polysome distribution.

    PubMed

    Higuchi, Yujiro; Ashwin, Peter; Roger, Yvonne; Steinberg, Gero

    2014-02-01

    Early endosomes (EEs) mediate protein sorting, and their cytoskeleton-dependent motility supports long-distance signaling in neurons. Here, we report an unexpected role of EE motility in distributing the translation machinery in a fungal model system. We visualize ribosomal subunit proteins and show that the large subunits diffused slowly throughout the cytoplasm (Dc,60S = 0.311 µm(2)/s), whereas entire polysomes underwent long-range motility along microtubules. This movement was mediated by "hitchhiking" on kinesin-3 and dynein-driven EEs, where the polysomes appeared to translate EE-associated mRNA into proteins. Modeling indicates that this motor-driven transport is required for even cellular distribution of newly formed ribosomes. Indeed, impaired EE motility in motor mutants, or their inability to bind EEs in mutants lacking the RNA-binding protein Rrm4, reduced ribosome transport and induced ribosome aggregation near the nucleus. As a consequence, cell growth was severely restricted. Collectively, our results indicate that polysomes associate with moving EEs and that "off- and reloading" distributes the protein translation machinery.

  7. 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

  8. 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

  9. Motility disorders in childhood.

    PubMed

    Milla, P J

    1998-12-01

    Motility disorders are very common in childhood, causing a number of gastrointestinal symptoms: recurrent vomiting, abdominal pain and distension, constipation and obstipation, and loose stools. The disorders result from disturbances of gut motor control mechanisms caused by either intrinsic disease of nerve and muscle, central nervous system dysfunction or perturbation of the humoral environment in which they operate. Intrinsic gut motor disease and central nervous system disorder are most usually congenital in origin, and alterations of the humoral environment acquired. Irritable bowel syndrome occurs in children as well as adults and is multifactorial in origin, with an interplay of psychogenic and organic disorders. PMID:10079906

  10. 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

  11. 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

  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 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

  13. Electric Field–directed Cell Motility Involves Up-regulated Expression and Asymmetric Redistribution of the Epidermal Growth Factor Receptors and Is Enhanced by Fibronectin and Laminin

    PubMed Central

    Zhao, Min; Dick, Andrew; Forrester, John V.; McCaig, Colin D.

    1999-01-01

    Wounding corneal epithelium establishes a laterally oriented, DC electric field (EF). Corneal epithelial cells (CECs) cultured in similar physiological EFs migrate cathodally, but this requires serum growth factors. Migration depends also on the substrate. On fibronectin (FN) or laminin (LAM) substrates in EF, cells migrated faster and more directly cathodally. This also was serum dependent. Epidermal growth factor (EGF) restored cathodal-directed migration in serum-free medium. Therefore, the hypothesis that EGF is a serum constituent underlying both field-directed migration and enhanced migration on ECM molecules was tested. We used immunofluorescence, flow cytometry, and confocal microscopy and report that 1) EF exposure up-regulated the EGF receptor (EGFR); so also did growing cells on substrates of FN or LAM; and 2) EGFRs and actin accumulated in the cathodal-directed half of CECs, within 10 min in EF. The cathodal asymmetry of EGFR and actin staining was correlated, being most marked at the cell–substrate interface and showing similar patterns of asymmetry at various levels through a cell. At the cell–substrate interface, EGFRs and actin frequently colocalized as interdigitated, punctate spots resembling tank tracks. Cathodal accumulation of EGFR and actin did not occur in the absence of serum but were restored by adding ligand to serum-free medium. Inhibition of MAPK, one second messenger engaged by EGF, significantly reduced EF-directed cell migration. Transforming growth factor β and fibroblast growth factor also restored cathodal-directed cell migration in serum-free medium. However, longer EF exposure was needed to show clear asymmetric distribution of the receptors for transforming growth factor β and fibroblast growth factor. We propose that up-regulated expression and redistribution of EGFRs underlie cathodal-directed migration of CECs and directed migration induced by EF on FN and LAM. PMID:10198071

  14. Gastrointestinal Motility Disorders and Acupuncture

    PubMed Central

    Yin, Jieyun; Chen, Jiande D Z

    2010-01-01

    During the last decades, numerous studies have been performed to investigate the effects and mechanisms of acupuncture or electroacupuncture (EA) on gastrointestinal motility and patients with functional gastrointestinal diseases. A PubMed search was performed on this topic and all available studies published in English have been reviewed and evaluated. This review is organized based on the gastrointestinal organ (from the esophagus to the colon), components of gastrointestinal motility and the functional diseases related to specific motility disorders. It was found that the effects of acupuncture or EA on gastrointestinal motility were fairly consistent and the major acupuncture points used in these studies were ST36 and PC6. Gastric motility has been mostly studied, whereas much less information is available on the effect of EA on small and large intestinal motility or related disorders. A number of clinical studies have been published, investigating the therapeutic effects of EA on a number of functional gastrointestinal diseases, such as gastroesophageal reflux, functional dyspepsia and irritable bowel syndrome. However, the findings of these clinical studies were inconclusive. In summary, acupuncture or EA is able to alter gastrointestinal motility functions and improve gastrointestinal motility disorders. However, more studies are needed to establish the therapeutic roles of EA in treating functional gastrointestinal diseases. PMID:20363196

  15. Cone Health and Retinoids.

    PubMed

    Kono, Masahiro

    2015-01-01

    Cones are photoreceptor cells used for bright light and color vision. Retinoids are vitamin A derivatives, one of which is the 11-cis aldehyde form that serves as the chromophore for both cone and rod visual pigments. In the visual disease, Type 2 Leber congenital amaurosis (LCA2), 11-cis-retinal generation is inhibited or abolished. Work by others has shown that patients with LCA2 have symptoms consistent with degenerating cones. In mouse models for LCA2, early cone degeneration is readily apparent: cone opsins and other proteins associated with the outer segment are delocalized and cell numbers decline rapidly within the first month. Rods would appear normal morphologically and functionally, if not for the absence of chromophore. Supplementation of mouse models of LCA2 with cis-retinoids has been shown to slow loss of cone photoreceptor cells if mice were maintained in darkness. Thus, 11-cis-retinal appears not only to have a role in the light response reaction but also to promote proper trafficking of the cone opsins and maintain viable cones. PMID:26310171

  16. Automated measurement of cell motility and proliferation

    PubMed Central

    Bahnson, Alfred; Athanassiou, Charalambos; Koebler, Douglas; Qian, Lei; Shun, Tongying; Shields, Donna; Yu, Hui; Wang, Hong; Goff, Julie; Cheng, Tao; Houck, Raymond; Cowsert, Lex

    2005-01-01

    Background Time-lapse microscopic imaging provides a powerful approach for following changes in cell phenotype over time. Visible responses of whole cells can yield insight into functional changes that underlie physiological processes in health and disease. For example, features of cell motility accompany molecular changes that are central to the immune response, to carcinogenesis and metastasis, to wound healing and tissue regeneration, and to the myriad developmental processes that generate an organism. Previously reported image processing methods for motility analysis required custom viewing devices and manual interactions that may introduce bias, that slow throughput, and that constrain the scope of experiments in terms of the number of treatment variables, time period of observation, replication and statistical options. Here we describe a fully automated system in which images are acquired 24/7 from 384 well plates and are automatically processed to yield high-content motility and morphological data. Results We have applied this technology to study the effects of different extracellular matrix compounds on human osteoblast-like cell lines to explore functional changes that may underlie processes involved in bone formation and maintenance. We show dose-response and kinetic data for induction of increased motility by laminin and collagen type I without significant effects on growth rate. Differential motility response was evident within 4 hours of plating cells; long-term responses differed depending upon cell type and surface coating. Average velocities were increased approximately 0.1 um/min by ten-fold increases in laminin coating concentration in some cases. Comparison with manual tracking demonstrated the accuracy of the automated method and highlighted the comparative imprecision of human tracking for analysis of cell motility data. Quality statistics are reported that associate with stage noise, interference by non-cell objects, and uncertainty in the

  17. 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.

  18. Progressive cone dystrophy.

    PubMed Central

    Ripps, H; Noble, K G; Greenstein, V C; Siegel, I M; Carr, R E

    1987-01-01

    Psychophysical, reflectometric, and electrophysiological studies were performed on four members of a dominant pedigree with progressive cone dystrophy. The two youngest individuals were asymptomatic at the initial examination, and none of the subjects complained of problems associated with night vision. Absent or grossly reduced cone-mediated ERG responses revealed the widespread loss of cone function. Moderate elevations (1 log unit) in absolute threshold together with reductions in rhodopsin levels in the midperipheral retina provided evidence of a mild impairment of the rod system also, although not to the degree seen in a cone-rod dystrophy. The progressive nature of the disease was apparent from the case histories and the changes in visual performance that occurred on re-test after a 5-year interval. Likewise, the results of incremental threshold measurements at several retinal loci suggested that peripheral cones may be affected earlier and more severely than those in the central retina. PMID:3502298

  19. S-cone psychophysics.

    PubMed

    Smithson, Hannah E

    2014-03-01

    We review the features of the S-cone system that appeal to the psychophysicist and summarize the celebrated characteristics of S-cone mediated vision. Two factors are emphasized: First, the fine stimulus control that is required to isolate putative visual mechanisms and second, the relationship between physiological data and psychophysical approaches. We review convergent findings from physiology and psychophysics with respect to asymmetries in the retinal wiring of S-ON and S-OFF visual pathways, and the associated treatment of increments and decrements in the S-cone system. Beyond the retina, we consider the lack of S-cone projections to superior colliculus and the use of S-cone stimuli in experimental psychology, for example to address questions about the mechanisms of visually driven attention. Careful selection of stimulus parameters enables psychophysicists to produce entirely reversible, temporary, "lesions," and to assess behavior in the absence of specific neural subsystems. PMID:24759446

  20. 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).

  1. Epidermal growth factor upregulates motility of Mat-LyLu rat prostate cancer cells partially via voltage-gated Na+ channel activity

    PubMed Central

    Ding, Yanning; Brackenbury, William J.; Onganer, Pinar U.; Montano, Ximena; Porter, Louise M.; Bates, Lucy F.; Djamgoz, Mustafa B. A.

    2014-01-01

    The main aim of this investigation was to determine whether a functional relationship existed between epidermal growth factor (EGF) and voltage-gated sodium channel (VGSC) upregulation, both associated with strongly metastatic prostate cancer cells. Incubation with EGF for 24 h more than doubled VGSC current density. Similar treatment with EGF significantly and dose-dependently enhanced the cells’ migration through Transwell filters. Both the patch clamp recordings and the migration assay suggested that endogenous EGF played a similar role. Importantly, co-application of EGF and tetrodotoxin, a highly selective VGSC blocker, abolished 65% of the potentiating effect of EGF. It is suggested that a significant portion of the EGF-induced enhancement of migration occurred via VGSC activity. PMID:17960590

  2. Cyclic GMP and Cilia Motility

    PubMed Central

    Wyatt, Todd A.

    2015-01-01

    Motile cilia of the lungs respond to environmental challenges by increasing their ciliary beat frequency in order to enhance mucociliary clearance as a fundamental tenant of innate defense. One important second messenger in transducing the regulable nature of motile cilia is cyclic guanosine 3′,5′-monophosphate (cGMP). In this review, the history of cGMP action is presented and a survey of the existing data addressing cGMP action in ciliary motility is presented. Nitric oxide (NO)-mediated regulation of cGMP in ciliated cells is presented in the context of alcohol-induced cilia function and dysfunction. PMID:26264028

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  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. 2017 Eclipse Shadow Cones

    NASA Video Gallery

    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...

  7. Lunar cinder cones.

    PubMed

    McGetchin, T R; Head, J W

    1973-04-01

    Data on terrestrial eruptions of pyroclastic material and ballistic considerations suggest that in the lunar environment (vacuum and reduced gravity) low-rimmed pyroclastic rings are formed rather than the high-rimmed cinder cones so abundant on the earth. Dark blanketing deposits in the Taurus-Littrow region (Apollo 17 landing area) are interpreted as being at least partly composed of lunar counterparts of terrestrial cinder cones.

  8. Lunar cinder cones.

    NASA Technical Reports Server (NTRS)

    Mcgetchin, T. R.; Head, J. W.

    1973-01-01

    Data on terrestrial eruptions of pyroclastic material and ballistic considerations suggest that in the lunar environment (vacuum and reduced gravity) low-rimmed pyroclastic rings are formed rather than the high-rimmed cinder cones so abundant on the earth. Dark blanketing deposits in the Taurus-Littrow region (Apollo 17 landing area) are interpreted as being at least partly composed of lunar counterparts of terrestrial cinder cones.

  9. 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.).

  10. 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

  11. A re-examination of twitching motility in Pseudomonas aeruginosa.

    PubMed

    Semmler, A B; Whitchurch, C B; Mattick, J S

    1999-10-01

    Twitching motility is a form of solid surface translocation which occurs in a wide range of bacteria and which is dependent on the presence of functional type IV fimbriae or pili. A detailed examination of twitching motility in Pseudomonas aeruginosa under optimal conditions in vitro was carried out. Under these conditions (at the smooth surface formed between semi-solid growth media and plastic or glass surfaces) twitching motility is extremely rapid, leading to an overall radial rate of colony expansion of 0.6 mm h(-1) or greater. The zones of colony expansion due to twitching motility are very thin and are best visualized by staining. These zones exhibit concentric rings in which there is a high density of microcolonies, which may reflect periods of expansion and consolidation/cell division. Video microscopic analysis showed that twitching motility involves the initial formation of large projections or rafts of aggregated cells which move away from the colony edge. Behind the rafts, individual cells move rapidly up and down trails which thin and branch out, ultimately forming a fine lattice-like network of cells. The bacteria in the lattice network then appear to settle and divide to fill out the colonized space. Our observations redefine twitching motility as a rapid, highly organized mechanism of bacterial translocation by which P. aeruginosa can disperse itself over large areas to colonize new territories. It is also now clear, both morphologically and genetically, that twitching motility and social gliding motility, such as occurs in Myxococcus xanthus, are essentially the same process.

  12. 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

  13. Why rods and cones?

    PubMed

    Lamb, T D

    2016-02-01

    Under twenty-first-century metropolitan conditions, almost all of our vision is mediated by cones and the photopic system, yet cones make up barely 5% of our retinal photoreceptors. This paper looks at reasons why we additionally possess rods and a scotopic system, and asks why rods comprise 95% of our retinal photoreceptors. It considers the ability of rods to reliably signal the arrival of individual photons of light, as well as the ability of the retina to process these single-photon signals, and it discusses the advantages that accrue. Drawbacks in the arrangement, including the very slow dark adaptation of scotopic vision, are also considered. Finally, the timing of the evolution of cone and rod photoreceptors, the retina, and the camera-style eye is summarised.

  14. [Mechanism of bacterial gliding motility].

    PubMed

    Nakane, Daisuke

    2015-01-01

    Bacteria have various way to move over solid surfaces, such as glass, agar, and host cell. These movements involve surface appendages including flagella, type IV pili and other "mysterious" nano-machineries. Gliding motility was a term used various surface movements by several mechanisms that have not been well understood in past few decades. However, development of visualization techniques allowed us to make much progress on their dynamics of machineries. It also provided us better understanding how bacteria move over surfaces and why bacteria move in natural environments. In this review, I will introduce recent studies on the gliding motility of Flavobacteium and Mycoplasma based on the detail observation of single cell and its motility machinery with micro-nano scales. PMID:26632217

  15. Cap protects aircraft nose cone

    NASA Technical Reports Server (NTRS)

    Bryan, C. F., Jr.; Bryan, D. C.

    1981-01-01

    Inexpensive, easily fabricated cap protects aircraft nose cone from erosion. Made of molded polycarbonate, cap has been flight tested at both subsonic and supesonic speeds. Its strength and erosion characteristics are superior to those of fiberglass cones.

  16. Magma supply rates inferred from cinder cone volumes

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Borgia, A.; Neri, M.; Kervyn, M.

    2010-12-01

    Revisiting the question of how cinder cones grow suggests the possibility of inferring magma supply rates from cinder cones sizes. We start with a conceptual model of cinder cone growth: (1) Eruption volume flux increases rapidly and then decreases exponentially. (2) Cinder cones get steeper during the initiation of the eruption and then maintain a constant steepness. (3) The initial basal diameter varies with volume flux into the cone. Based on these constraints, we propose a general form for the relationship between cinder cone volume and magma supply rate: V = Q(exp(-t/b)/b - exp(-t/a)/a), where V is volume (in m3), Q is the maximum potential magma flux (in m3/s), t is time (in s), a is a damping factor (in s) controlling the decline in volume flux, and b is a factor controlling the initial increase in volume flux. Then we use the data available on the growth of cinder cones from four modern eruptions to show the relevance of our model and to constrain the supply curves. All four modern cones (Paricutin, Mexico which erupted 1943-1974; Tolbachik, Kamchatka which erupted in 1975-1976; Cono del Laghetto, Mount Etna, Italy which formed in 2001; and a small cone on the summit of Oldoinyo Lengai, Tanzania, which formed during the 2007 eruption) show the basic growth pattern: initial rapid growth followed by declining growth (Figure 1). The regression results yeild the following magma supply rates: The southern Tolbachik cones have the largest predicted magma supply at ~100 m3/s. Paricutin and Laghetto are around 9 m3/s. The Oldoinyo Lengai cone has a magma supply of ~0.5 m3/s. The northern Tolbachik cone has the lowest magma supply of ~0.1 m3/s. In contrast, the damping factor a is generally on the order of 107 (it varies from 8 x 106 at southern Tolbachik to 4 x 107 at northern Tolbachik). The parameter b controlling the initial increase is generally small (<1). The predicted magma supply does not seem to be very sensitive to either parameter. Thus we suggest that

  17. 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

    2015-01-01

    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. PMID:25938934

  18. 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.

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

    PubMed

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

    2013-12-01

    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 disc. 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.

  20. 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.

  1. 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).

  2. 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).

  3. Cone rod dystrophies.

    PubMed

    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

  4. Increase in neuropilin-1 on the surface of growth cones and putative raft domains in neuronal NG108-15 cells co-cultured with vascular smooth muscle SM-3 cells.

    PubMed

    Yoshimura, Ryoichi; Kyuka, Ayumi; Jinno, Miwa; Nishio, Satomi; Matsusaka, Mamoru; Nishida, Tomoki; Endo, Yasuhisa

    2015-04-01

    The mechanisms underlying autonomic innervation to its targets involve various chemical factors, but have not yet been elucidated in detail. We constructed a co-culture system of neuronal cells and vascular smooth muscle cells to investigate the mechanisms underlying innervation of the vasculature. A co-culture with the vascular smooth muscle cell line, SM-3 significantly promoted cell viability, neurite extension, and neuropilin-1 (Nrp-1) mRNA expression in the cholinergic neuronal cell line, NG108-15. Furthermore, immunocytochemistry with or without a detergent treatment revealed that a co-culture with SM-3 cells or culturing with the conditioned medium of SM-3 cells translocated Nrp-1 onto the cell surface of growth cones rather than varicosities of NG108-15 cells. Immunofluorescent microscopy combined with a cold detergent treatment or cholesterol depletion revealed that Nrp-1 accumulated in putative raft domains in the plasma membrane of NG108-15 cells co-cultured with SM-3 cells. The results of the present study suggest that some soluble factors from smooth muscle cells may affect the localization of Nrp-1 in cholinergic neuronal cells, which may, in turn, be involved in the autonomic innervation of blood vessels.

  5. Chemotactic Motility of Pseudomonas fluorescens F113 under Aerobic and Denitrification Conditions

    PubMed Central

    Redondo-Nieto, Miguel; Rivilla, Rafael; Martín, Marta

    2015-01-01

    The sequence of the genome of Pseudomonas fluorescens F113 has shown the presence of multiple traits relevant for rhizosphere colonization and plant growth promotion. Among these traits are denitrification and chemotactic motility. Besides aerobic growth, F113 is able to grow anaerobically using nitrate and nitrite as final electron acceptors. F113 is able to perform swimming motility under aerobic conditions and under anaerobic conditions when nitrate is used as the electron acceptor. However, nitrite can not support swimming motility. Regulation of swimming motility is similar under aerobic and anaerobic conditions, since mutants that are hypermotile under aerobic conditions, such as gacS, sadB, kinB, algU and wspR, are also hypermotile under anaerobic conditions. However, chemotactic behavior is different under aerobic and denitrification conditions. Unlike most pseudomonads, the F113 genome encode three complete chemotaxis systems, Che1, Che2 and Che3. Mutations in each of the cheA genes of the three Che systems has shown that the three systems are functional and independent. Mutation of the cheA1 gene completely abolished swimming motility both under aerobic and denitrification conditions. Mutation of the cheA2 gene, showed only a decrease in swimming motility under both conditions, indicating that this system is not essential for chemotactic motility but is necessary for optimal motility. Mutation of the cheA3 gene abolished motility under denitrification conditions but only produced a decrease in motility under aerobic conditions. The three Che systems proved to be implicated in competitive rhizosphere colonization, being the cheA1 mutant the most affected. PMID:26161531

  6. Emergence of HGF/SF-induced coordinated cellular motility.

    PubMed

    Zaritsky, Assaf; Natan, Sari; Ben-Jacob, Eshel; Tsarfaty, Ilan

    2012-01-01

    Collective cell migration plays a major role in embryonic morphogenesis, tissue remodeling, wound repair and cancer invasion. Despite many decades of extensive investigations, only few analytical tools have been developed to enhance the biological understanding of this important phenomenon. Here we present a novel quantitative approach to analyze long term kinetics of bright field time-lapse wound healing. Fully-automated spatiotemporal measures and visualization of cells' motility and implicit morphology were proven to be sound, repetitive and highly informative compared to single-cell tracking analysis. We study cellular collective migration induced by tyrosine kinase-growth factor signaling (Met-Hepatocyte Growth Factor/Scatter Factor (HGF/SF)). Our quantitative approach is applied to demonstrate that collective migration of the adenocarcinoma cell lines is characterized by simple morpho-kinetics. HGF/SF induces complex morpho-kinetic coordinated collective migration: cells at the front move faster and are more spread than those further away from the wound edge. As the wound heals, distant cells gradually accelerate and enhance spread and elongation -resembling the epithelial to mesenchymal transition (EMT), and then the cells become more spread and maintain higher velocity than cells located closer to the wound. Finally, upon wound closure, front cells halt, shrink and round up (resembling mesenchymal to epithelial transition (MET) phenotype) while distant cells undergo the same process gradually. Met inhibition experiments further validate that Met signaling dramatically alters the morpho-kinetic dynamics of the healing wound. Machine-learning classification was applied to demonstrate the generalization of our findings, revealing even subtle changes in motility patterns induced by Met-inhibition. It is concluded that activation of Met-signaling induces an elaborated model in which cells lead a coordinated increased motility along with gradual differentiation

  7. Elastic mismatch enhances cell motility

    NASA Astrophysics Data System (ADS)

    Bresler, Yony; Palmieri, Benoit; Grant, Martin

    In recent years, the study of physics phenomena in cancer has drawn considerable attention. In cancer metastasis, a soft cancer cell leaves the tumor, and must pass through the endothelium before reaching the bloodstream. Using a phase-field model we have shown that the elasticity mismatch between cells alone is sufficient to enhance the motility of thesofter cancer cell by means of bursty migration, in agreement with experiment. We will present further characterization of these behaviour, as well as new possible applications for this model.

  8. 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.

  9. The Holographic Entropy Cone

    DOE PAGES

    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 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

  10. 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.

  11. 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,…

  12. Evaluation of otoscope cone cleaning and disinfection procedures commonly used in veterinary medical practices: a pilot study.

    PubMed

    Newton, Heide M; Rosenkrantz, Wayne S; Muse, Russell; Griffin, Craig E

    2006-04-01

    The objective of this study was to evaluate the relative efficacy of otoscope cone cleaning and disinfection methods commonly used in veterinary practices. Using sterile technique, 60 new gas-sterilized 4-mm otoscope cones were inoculated with a broth culture of 1.5 billion Pseudomonas aeruginosa bacteria per mL then allowed to dry for 10 min. Six study groups of 10 cones each were created. Group 1 served as positive control and received no cleaning or disinfection. Group 2 cones were wiped with sterile cotton-tipped applicators and gauze then rinsed with water. Group 3 cones were wiped with 70% isopropyl alcohol. Group 4 cones were scrubbed in a speculum cleaner with Cetylcide II solution (Cetylite Industries, Inc., Pennsauken, NJ). Groups 5 and 6 cones were soaked for 20 min in Cetylcide II and chlorhexidine gluconate 2% solutions, respectively. Using sterile technique and after 10-15 min drying time, the cones were swabbed in a consistent pattern, and samples were submitted for quantitative culture. Culture results showed no growth from cones soaked in Cetylcide II or chlorhexidine solutions. Two of the 10 cones wiped with alcohol, 3/10 cones wiped then rinsed with water, and 3/10 cones scrubbed with the speculum cleaner showed growth of P. aeruginosa. All (10/10) cones in the control group showed heavy growth of P. aeruginosa. These results show that P. aeruginosa can survive on otoscope cones cleaned and disinfected by several commonly used methods. Further study is needed to determine practical and optimal cleaning and disinfection methods for otoscope cones.

  13. Asian Motility Studies in Irritable Bowel Syndrome

    PubMed Central

    2010-01-01

    Altered motility remains one of the important pathophysiologic factors in patients with irritable bowel syndrome (IBS) who commonly complain of abdominal pain and stool changes such as diarrhea and constipation. The prevalence of IBS has increased among Asian populations these days. Gastrointestinal (GI) physiology may vary between Asian and Western populations because of differences in diets, socio-cultural backgrounds, and genetic factors. The characteristics and differences of GI dysmotility in Asian IBS patients were reviewed. MEDLINE search work was performed including following terms, 'IBS,' 'motility,' 'transit time,' 'esophageal motility,' 'gastric motility,' 'small intestinal motility,' 'colonic motility,' 'anorectal function,' and 'gallbladder motility' and over 100 articles were categorized under 'esophagus,' 'stomach,' 'small intestine,' 'colon,' 'anorectum,' 'gallbladder,' 'transit,' 'motor pattern,' and 'effect of stressors.' Delayed gastric emptying, slow tansit in constipation predominant IBS patients, rapid transit in diarrhea predominant IBS patients, accelerated motility responses to various stressors such as meals, mental stress, or corticotrophin releasing hormones, and altered rectal compliance and altered rectal accomodation were reported in many Asian studies regarding IBS. Many conflicting results were found among these studies and there are still controversies to conclude these as unique features of Asian IBS patients. Multinational and multicenter studies are needed to be performed vigorously in order to elaborate characteristics as well as differences of altered motililty in Asian patients with IBS. PMID:20535342

  14. Kobe earthquake and reduced sperm motility.

    PubMed

    Fukuda, M; Fukuda, K; Shimizu, T; Yomura, W; Shimizu, S

    1996-06-01

    We investigated a possible relationship between the Kobe earthquake (January 17, 1995) and the quality of semen. We assessed sperm concentration and motility of 27 male patients who had a concentration of more than 30 million/ml and >40% sperm motility within 5 months before the earthquake. Twelve male patients from districts with a magnitude of <4 on the Richter scale showed no difference in sperm concentration and motility before and after the earthquake. Of 15 male patients from districts with a magnitude of >6, five patients whose houses received no damage showed no distinct changes in sperm concentration and motility. In contrast, 10 patients whose houses were partially or completely destroyed showed significantly (P < 0.001) lower sperm motility after the earthquake than before, although no significant difference of sperm concentration could be observed. Of these latter 10 patients, seven could be followed. In six patients, sperm motility was restored between 2 and 9 months after the earthquake; the sperm motility in one patient, whose father died a victim of the house crash, has not yet recovered. Thus, the acute stress resulting from such a catastrophic earthquake could be a possible cause of reduced sperm motility.

  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. Bacillus subtilis Hfq: A role in chemotaxis and motility.

    PubMed

    Jagtap, Chandrakant B; Kumar, Pradeep; Rao, Krishnamurthy K

    2016-09-01

    Hfq is a global post-transcriptional regulator that modulates the translation and stability of target mRNAs and thereby regulates pleiotropic functions, such as growth, stress, virulence and motility, in many Gram-negative bacteria. However, comparatively little is known about the regulation and function(s) of Hfq in Gram-positive bacteria. Recently, in Bacillus subtilis, a role for Hfq in stationary phase survival has been suggested, although the possibility of Hfq having an additional role(s) cannot be ruled out. In this study we show that an ortholog of Hfq in B. subtilis is regulated by the stress sigma factor, sigma^B, in addition to the stationary phase sigma factor, sigma^H. We further demonstrate that Hfq positively regulates the expression of flagellum and chemotaxis genes (fla/che) that control chemotaxis and motility, thus assigning a new function for Hfq in B. subtilis.

  17. Bacillus subtilis Hfq: A role in chemotaxis and motility.

    PubMed

    Jagtap, Chandrakant B; Kumar, Pradeep; Rao, Krishnamurthy K

    2016-09-01

    Hfq is a global post-transcriptional regulator that modulates the translation and stability of target mRNAs and thereby regulates pleiotropic functions, such as growth, stress, virulence and motility, in many Gram-negative bacteria. However, comparatively little is known about the regulation and function(s) of Hfq in Gram-positive bacteria. Recently, in Bacillus subtilis, a role for Hfq in stationary phase survival has been suggested, although the possibility of Hfq having an additional role(s) cannot be ruled out. In this study we show that an ortholog of Hfq in B. subtilis is regulated by the stress sigma factor, sigma^B, in addition to the stationary phase sigma factor, sigma^H. We further demonstrate that Hfq positively regulates the expression of flagellum and chemotaxis genes (fla/che) that control chemotaxis and motility, thus assigning a new function for Hfq in B. subtilis. PMID:27581927

  18. 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

  19. 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

  20. A Nutrient-Tunable Bistable Switch Controls Motility in Salmonella enterica Serovar Typhimurium

    PubMed Central

    Koirala, Santosh; Mears, Patrick; Sim, Martin; Golding, Ido; Chemla, Yann R.; Aldridge, Phillip D.

    2014-01-01

    ABSTRACT Many bacteria are motile only when nutrients are scarce. In contrast, Salmonella enterica serovar Typhimurium is motile only when nutrients are plentiful, suggesting that this bacterium uses motility for purposes other than foraging, most likely for host colonization. In this study, we investigated how nutrients affect motility in S. enterica and found that they tune the fraction of motile cells. In particular, we observed coexisting populations of motile and nonmotile cells, with the distribution being determined by the concentration of nutrients in the growth medium. Interestingly, S. enterica responds not to a single nutrient but apparently to a complex mixture of them. Using a combination of experimentation and mathematical modeling, we investigated the mechanism governing this behavior and found that it results from two antagonizing regulatory proteins, FliZ and YdiV. We also found that a positive feedback loop involving the alternate sigma factor FliA is required, although its role appears solely to amplify FliZ expression. We further demonstrate that the response is bistable: that is, genetically identical cells can exhibit different phenotypes under identical growth conditions. Together, these results uncover a new facet of the regulation of the flagellar genes in S. enterica and further demonstrate how bacteria employ phenotypic diversity as a general mechanism for adapting to change in their environment. PMID:25161191

  1. 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.

  2. Protonmotive force and motility of Bacillus subtilis.

    PubMed Central

    Shioi, J I; Imae, Y; Oosawa, F

    1978-01-01

    Motility of Bacillus subtilis was inhibited within a few minutes by a combination of valinomycin and a high concentration of potassium ions in the medium at neutral pH. Motility was restored by lowering the concentration of valinomycin or potassium ions. The valinomycin concentration necessary for motility inhibition was determined at various concentrations of potassium ions and various pH's. At pH 7.5, valinomycin of any concentration did not inhibit the motility, when the potassium ion concentration was lower than 9 mM. In the presence of 230 mM potassium ion, the motility inhibition by valinomycin was not detected at pH lower than 6.1. These results are easily explained by the idea that the motility of B. subtilis is supported by the electrochemical potential difference of the proton across the membrane, or the protonmotive force. The electrochemical potential difference necessary for motility was estimated to be about -90 mV. PMID:25261

  3. Computer-assisted quantification of motile and invasive capabilities of cancer cells.

    PubMed

    Kumar, Karthiga Santhana; Pillong, Max; Kunze, Jens; Burghardt, Isabel; Weller, Michael; Grotzer, Michael A; Schneider, Gisbert; Baumgartner, Martin

    2015-10-21

    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.

  4. 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

  5. Electrophoretic control of actomyosin motility

    NASA Astrophysics Data System (ADS)

    Hanson, Kristi L.; Solana, Gerardin; Nicolau, Dan V.

    2005-03-01

    The effect of DC electric field strength on in vitro actomyosin motility was examined. Rabbit skeletal muscle heavy meromyosin (HMM) was adsorbed to nitrocellulose-coated glass, and the myosin driven movement of fluorescently labeled actin filaments was recorded in the presence of 0 to 9000 V m-1 applied DC voltage. The applied electric field resulted in increased filament velocity and oriented actin movement, with leading heads of filaments directed towards the positive electrode. Velocity (v) was found to increase moderately with electric field strength at applied fields up to ~ 4500 V m-1 (Δv/ΔE = 0.037 μm2 V-1sec-1), and then increased at a more rapid rate (Δv/ΔE = 0.100 μm2 V-1sec-1) at higher field strengths up to 9000 V m-1. The electrophoretic effect caused up to 70% of actin motion to be oriented within 30 degrees of the positive electrode, with the largest effect observed using an applied field of 6000 V m-1. Higher electric field strengths caused filament breakage.

  6. 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.

  7. 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. PMID:26590774

  8. 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.

  9. How substrate rigidity regulates the cellular motility

    NASA Astrophysics Data System (ADS)

    Sarvestani, Alireza

    2011-03-01

    Mechanical stiffness of bio-adhesive substrates has been recognized as a major regulator of cell motility. We present a simple physical model to study the crawling locomotion of a contractile cell on a soft elastic substrate. The mechanism of rigidity sensing is accounted for using Schwarz's two spring model (Schwarz et al. (2006) BioSystems 83, 225-232). The predicted dependency between the speed of motility and substrate stiffness is qualitatively consistent with experimental observations. The model demonstrates that the rigidity dependent motility of cells is rooted in the regulation of actomyosin contractile forces by substrate deformation at each anchorage point. On stiffer substrates, the traction forces required for cell translocation acquire larger magnitude but show weaker asymmetry which leads to slower cell motility. On very soft substrates, the model predicts a biphasic relationship between the substrate rigidity and the speed of locomotion, over a narrow stiffness range, which has been observed experimentally for some cell types.

  10. Implications of altered gastrointestinal motility in obesity.

    PubMed

    Gallagher, T K; Geoghegan, J G; Baird, A W; Winter, D C

    2007-10-01

    The onset of obesity occurs as a result of an imbalance between nutrient consumption/absorption and energy expenditure. Gastrointestinal (GI) motility plays a critical role in the rate of consumption of foods, digestion, and absorption of nutrients. Various segments of the GI tract coordinate in a complex yet precise way, to control the process of food consumption, digestion, and absorption of nutrients. GI motility not only regulates the rates at which nutrients are processed and absorbed in the gut, but also, via mechanical and neurohormonal methods, participates in the control of appetite and satiety. Altered GI motility has frequently been observed in obese patients, the significance of which is incompletely understood. However, these alterations can be considered as potential contributing factors in the development and maintenance of obesity and changed eating behavior. Therapies aimed at regulating or counteracting the observed changes in GI motility are being actively explored and applied clinically in the management of obese patients. PMID:18098402

  11. 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. PMID:25820902

  12. Rootless cone eruption processes informed by dissected tephra deposits and conduits

    NASA Astrophysics Data System (ADS)

    Reynolds, P.; Brown, R. J.; Thordarson, T.; Llewellin, E. W.; Fielding, K.

    2015-09-01

    Rootless cones result from the explosive interaction between lava flows and underlying water-saturated sediment or volcaniclastic deposits. Rootless explosions can represent a significant far-field hazard during basaltic eruptions, but there are few detailed studies of their deposits. A rootless cone field in the 8.5 Ma Ice Harbor flow field of the Columbia River Basalt Province, NW USA, is revealed by sections through rootless conduit and cone structures. The Ice Harbor lava flow hosting the rootless cones was emplaced across a floodplain or lacustrine environment that had recently been mantled by a layer of silicic volcanic ash from a major explosive eruption. Our observations indicate a two-stage growth model for the rootless cones: (1) initial explosions generated sediment-rich tephra emplaced by fallout and pyroclastic density currents and (2) later weaker explosions that generated spatter-rich fountains. Variable explosive activity resulted in a wide range of pyroclast morphologies and vesicularities. Cross-sections through funnel-shaped conduits also show how the conduits were constructed and stabilised. The growth model is consistent with decreasing water availability with time, as inferred for rootless cones described in Iceland. The Ice Harbor rootless cones provide further lithological data to help distinguish between rootless cone-derived tephra and tephra generated above an erupting dyke.

  13. 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.

  14. 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. PMID:26523344

  15. The Effect of Alcohol on Gastrointestinal Motility.

    PubMed

    Grad, Simona; Abenavoli, Ludovico; Dumitrascu, Dan L

    2016-01-01

    The Gastrointestinal (GI) tract is one of the most affected systems by alcohol consumption. Alcohol can affect the esophagus in several ways: induces mucosal inflammation, increases the risk for Barrett esophagus and esophageal cancer, and also impairs the esophageal motility. Numerous studies have reported an increased prevalence of Gastroesophageal Reflux Disease (GERD) or erosive esophagitis in alcoholics. Some alcoholics exhibit an abnormality of esophageal motility known as a "nutcracker esophagus". Alcohol effect on gastric motility depends on the alcohol concentration. In general, beverages with high alcohol concentrations (i.e., above 15 percent) appear to inhibit gastric motility and low alcohol doses (wine and beer) accelerate gastric emptying. Also, acute administration of ethanol inhibits the gastric emptying, while chronic administration of a large dose of alcohol accelerates gastric motility. The effect of alcohol on small bowel motility differs according to the type of consumption (acute or chronic). Acute administration of alcohol has been found to inhibit small bowel transit and chronic administration of a large dose of alcohol accelerates small bowel transit. This article reviews some of the below findings. PMID:27527893

  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. 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

  18. 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.

  19. 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. PMID:27532050

  20. 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

  1. RP cone-rod degeneration.

    PubMed Central

    Heckenlively, J R

    1987-01-01

    A group of patients with progressive retinal degeneration and visual field loss, who meet the basic definition of RP were investigated to better define the relationship of the findings on the ERG with clinical characteristics such as visual field size, presence or absence of scotomata or pseudo-altitudinal defects on visual field, amount of night blindness; and presence or absence of macular or optic nerve changes. These studies suggest that cone-rod degeneration patients of the RP type go through the following stages; early, the ERG has a definite cone-rod pattern where the rod ERG is larger than the cone ERG while both are abnormal. As the disease advances, there is more of a reduction in the scotopic ERG such that both the rod and cone ERGs become nearly equal. As the disease further progresses the ERG becomes non-recordable on single-flash technique, but there is good residual rod function and the final rod threshold remains good until the visual field is reduced, typically less than 10 degrees with the IV-4 isopter. Finally with advanced disease the patient becomes night blind and generally becomes very difficult to distinguished from patients who have advanced rod-cone degeneration. While it may seem logical to find that visual field size correlates with various ERG parameters; this has not been as consistent a finding in patients with rod-cone degeneration in the author's experience. The analysis shows several new pieces of information about visual field changes in cone-rod degeneration; enlarged blind spots are seen earlier in cases which have recordable cone-rod patterns (group I), and pseudo-altitudinal changes are more likely to occur in autosomal recessive patients. Patients with macular lesions and central scotomata had larger amplitudes than patients with normal appearing maculae and no central scotomata. Patients with temporal optic atrophy had an earlier onset of symptoms and significant correlation with both photopic a- and b-waves and bright flash

  2. 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

  3. Exploring the role of CheA3 in Desulfovibrio vulgaris Hildenborough motility

    PubMed Central

    Ray, Jayashree; Keller, Kimberly L.; Catena, Michela; Juba, Thomas R.; Zemla, Marcin; Rajeev, Lara; Knierim, Bernhard; Zane, Grant M.; Robertson, Jarrod J.; Auer, Manfred; Wall, Judy D.; Mukhopadhyay, Aindrila

    2014-01-01

    Sulfate-reducing bacteria such as Desulfovibrio vulgaris Hildenborough are often found in environments with limiting growth nutrients. Using lactate as the electron donor and carbon source, and sulfate as the electron acceptor, wild type D. vulgaris shows motility on soft agar plates. We evaluated this phenotype with mutants resulting from insertional inactivation of genes potentially related to motility. Our study revealed that the cheA3 (DVU2072) kinase mutant was impaired in the ability to form motility halos. Insertions in two other cheA loci did not exhibit a loss in this phenotype. The cheA3 mutant was also non-motile in capillary assays. Complementation with a plasmid-borne copy of cheA3 restores wild type phenotypes. The cheA3 mutant displayed a flagellum as observed by electron microscopy, grew normally in liquid medium, and was motile in wet mounts. In the growth conditions used, the D. vulgaris ΔfliA mutant (DVU3229) for FliA, predicted to regulate flagella-related genes including cheA3, was defective both in flagellum formation and in forming the motility halos. In contrast, a deletion of the flp gene (DVU2116) encoding a pilin-related protein was similar to wild type. We conclude that wild type D. vulgaris forms motility halos on solid media that are mediated by flagella-related mechanisms via the CheA3 kinase. The conditions under which the CheA1 (DVU1594) and CheA2 (DVU1960) kinase function remain to be explored. PMID:24639670

  4. 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)

  5. 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.

  6. 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.

  7. 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.

  8. Competency based medical education in gastrointestinal motility.

    PubMed

    Yadlapati, R; Keswani, R N; Pandolfino, J E

    2016-10-01

    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 clarify the variable rates of learning for individual diagnostic tests. We must develop integrated systems that standardize training and monitor physician competency for GI motility diagnostics. Finally, as a profession and society, we must create certification processes to credential competent physicians. These advances are critical to optimizing the quality of GI motility diagnostics in practice.

  9. Visual versus cinemicrographic evaluation of human sperm motility and morphology.

    PubMed

    Freund, M; Oliveira, N

    1987-01-01

    Ratings of human sperm motility by visual estimation through the microscope remain important measures of semen quality and of male fertility. More objective methods, including cinemicrography, time lapse photography, and videomicrography, are advocated. Subjective (visual) and objective (cinemicrographic) ratings of motility were compared. Sixty workers in 30 laboratories rated motilities of 40 specimens on motion picture film, and motilities were also measured by cinephotomicrographic methods. The morphology of each of the motile and immotile sperm was rated. In 34 of 40 specimens visual ratings were higher (range = +2 to +31%) than actual percentage motility. Specimens with both high sperm concentration and forward progression received the highest overestimations by visual rating. This was especially apparent in specimens with the highest motility. There was a statistically significant positive relationship between sperm motility and morphology rated on a one-by-one basis, but the relationship was too small to influence the visual rating of human sperm motility.

  10. Dpp signaling directs cell motility and invasiveness during epithelial morphogenesis.

    PubMed

    Ninov, Nikolay; Menezes-Cabral, Sofia; Prat-Rojo, Carla; Manjón, Cristina; Weiss, Alexander; Pyrowolakis, George; Affolter, Markus; Martín-Blanco, Enrique

    2010-03-23

    Tissue remodeling in development and disease involves the coordinated invasion of neighboring territories and/or the replacement of entire cell populations. Cell guidance, cell matching, transitions from passive to migratory epithelia, cell growth and death, and extracellular matrix remodeling all impinge on epithelial spreading. Significantly, the extracellular signals that direct these activities and the specific cellular elements and mechanisms regulated by these signals remain in most cases to be identified. To address these issues, we performed an analysis of histoblasts (Drosophila abdominal epithelial founder cells) on their transition from a dormant state to active migration replacing obsolete larval epidermal cells (LECs). We found that during expansion, Decapentaplegic (Dpp) secreted from surrounding LECs leads to graded pathway activation in cells at the periphery of histoblast nests. Across nests, Dpp activity confers differential cellular behavior and motility by modulating cell-cell contacts, the organization and activity of the cytoskeleton, and histoblast attachment to the substrate. Furthermore, Dpp also prevents the premature death of LECs, allowing the coordination of histoblast expansion to LEC delamination. Dpp signaling activity directing histoblast spreading and invasiveness mimics transforming growth factor-beta and bone morphogenetic proteins' role in enhancing the motility and invasiveness of cancer cells, resulting in the promotion of metastasis. PMID:20226662

  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. Trimebutine as a modulator of gastrointestinal motility.

    PubMed

    Lee, Hyun-Tai; Kim, Byung Joo

    2011-06-01

    Trimebutine has been used for treatment of both hypermotility and hypomotility disorders of the gastrointestinal (GI) tract, such as irritable bowel syndrome. In this issue, Tan et al. (2011) examined the concentration-dependent dual effects of trimebutine on colonic motility in guinea pig. The authors suggested that trimebutine attenuated colonic motility mainly through the inhibition of L-type Ca(2+) channels at higher concentrations, whereas, at lower concentrations, it depolarized membrane potentials by reducing BK(ca) currents, resulting in the enhancement of the muscle contractions. Trimebutine might be a plausible modulator of GI motility, which gives an insight in developing new prokinetic agents. Further studies to elucidate the effects of trimebutine on the interstitial cells of Cajal, the pacemaker in GI muscles would promote the therapeutic benefits as a GI modulator. PMID:21725804

  13. Direct Upstream Motility in Escherichia coli

    PubMed Central

    Kaya, Tolga; Koser, Hur

    2012-01-01

    We provide an experimental demonstration of positive rheotaxis (rapid and continuous upstream motility) in wild-type Escherichia coli freely swimming over a surface. This hydrodynamic phenomenon is dominant below a critical shear rate and robust against Brownian motion and cell tumbling. We deduce that individual bacteria entering a flow system can rapidly migrate upstream (>20 μm/s) much faster than a gradually advancing biofilm. Given a bacterial population with a distribution of sizes and swim speeds, local shear rate near the surface determines the dominant hydrodynamic mode for motility, i.e., circular or random trajectories for low shear rates, positive rheotaxis for moderate flow, and sideways swimming at higher shear rates. Faster swimmers can move upstream more rapidly and at higher shear rates, as expected. Interestingly, we also find on average that both swim speed and upstream motility are independent of cell aspect ratio. PMID:22500751

  14. Transient wake and trajectory of free falling cones with various apex angles

    NASA Astrophysics Data System (ADS)

    Jin, Yaqing; Hamed, Ali M.; Chamorro, Leonardo P.

    2015-11-01

    The early free-fall stages of cones with a density ratio 1.18 and apex angles of 30°, 45°, 60°, and 90° were studied using a wireless 3-axis gyroscope and accelerometer to describe the cone 3D motions, while the induced flow in the near wake was captured using particle image velocimetry. The Reynolds number based on the cone diameter and the velocity at which the cone reaches the first local velocity maximum is found to set the limit between two distinctive states. Before this Re is reached the departure from the vertical path and cone rotations are insignificant, while relatively rapid growth is observed after this Re. Sequences of vertical velocity, swirling strength, LES-decomposed velocity, and pressure fields shows the formation and growth of a large and initially symmetric recirculation bubble at the cone base and highlights the presence of a symmetric 3D vortex rollup dominating the near-wake in the early stages of the fall. Later, the shear layer at the edge of the wake manifests in the shedding of Kelvin-Helmholtz vortices that, due to the nature of the recirculation bubble, reorganize to constitute a part of the rollup. Later in the fall, the wake loses its symmetry and shows a high population of vortical structures leading to turbulence. The asymmetric wake leads to strong interactions between the flow field and the cone creating complex feedback loops.

  15. Motor domain-based motility system and motile properties of alpha heavy chain in Tetrahymena outer arm dynein.

    PubMed

    Edamatsu, Masaki

    2014-10-24

    Axonemal dynein plays an essential role in ciliary motility, and impaired ciliary motility causes human diseases such as primary ciliary dyskinesia (PCD). The motor domain of axonemal dynein powers ciliary motility and its function is regulated by several accessary proteins bound to the tail region. Therefore, to understand the essential properties of dynein motility, examining the motile properties of the motor domain without the tail is necessary. In this study, the functional motor domain of the alpha heavy chain in Tetrahymena outer arm dynein was purified, and its motile properties were examined using an in vitro motility system. The purified protein caused microtubules to glide at a velocity of 5.0μm/s with their minus-end trailing, and motility was inhibited in an ATP concentration-dependent manner, which is in contrast with kinesin1. This method could be applicable to other axonemal dyneins and will enable further molecular studies on diverse axonemal dyneins and ciliary motility.

  16. 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

  17. 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

  18. 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.

  19. Disclinations, e-cones, and their interactions in extensible sheets.

    PubMed

    Chopin, Julien; Kudrolli, Arshad

    2016-05-11

    We investigate the nucleation, growth, and spatial organization of topological defects with a ribbon shaped elastic sheet which is stretched and twisted. Singularities are found to spontaneously arrange in a triangular lattice in the form of vertices connected by stretched ridges that result in a self-rigidified structure. The vertices are shown to be negative disclinations or e-cones which occur in sheets with negative Gaussian curvature, in contrast with d-cones in sheets with zero-Gaussian curvature. We find the growth of the wrinkled width of the ribbon to be consistent with a far-from-threshold approach assuming a compression-free base state. The system is found to show a transition from a regime where the wavelength is given by the ribbon geometry, to where it is given by its elasticity as a function of the ratio of the applied tension to the elastic modulus and cross-sectional area of the ribbon.

  20. Flagellar motility of the pathogenic spirochetes.

    PubMed

    Wolgemuth, Charles W

    2015-10-01

    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

  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. Integrin Molecular Tension within Motile Focal Adhesions.

    PubMed

    Wang, Xuefeng; Sun, Jie; Xu, Qian; Chowdhury, Farhan; Roein-Peikar, Mehdi; Wang, Yingxiao; Ha, Taekjip

    2015-12-01

    Forces transmitted by integrins regulate many important cellular functions. Previously, we developed tension gauge tether (TGT) as a molecular force sensor and determined the threshold tension across a single integrin-ligand bond, termed integrin tension, required for initial cell adhesion. Here, we used fluorescently labeled TGTs to study the magnitude and spatial distribution of integrin tension on the cell-substratum interface. We observed two distinct levels of integrin tension. A >54 pN molecular tension is transmitted by clustered integrins in motile focal adhesions (FAs) and such force is generated by actomyosin, whereas the previously reported ∼40 pN integrin tension is transmitted by integrins before FA formation and is independent of actomyosin. We then studied FA motility using a TGT-coated surface as a fluorescent canvas, which records the history of integrin force activity. Our data suggest that the region of the strongest integrin force overlaps with the center of a motile FA within 0.2 μm resolution. We also found that FAs move in pairs and that the asymmetry in the motility of an FA pair is dependent on the initial FA locations on the cell-substratum interface.

  3. 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

  4. Targeting tumor cell motility to prevent metastasis

    PubMed Central

    Palmer, Trenis D.; Ashby, William J.; Lewis, John D.; Zijlstra, Andries

    2011-01-01

    Mortality and morbidity in patients with solid tumors invariably results from the disruption of normal biological function caused by disseminating tumor cells. Tumor cell migration is under intense investigation as the underlying cause of cancer metastasis. The need for tumor cell motility in the progression of metastasis has been established experimentally and is supported empirically by basic and clinical research implicating a large collection of migration-related genes. However, there are few clinical interventions designed to specifically target the motility of tumor cells and adjuvant therapy to specifically prevent cancer cell dissemination is severely limited. In an attempt to define motility targets suitable for treating metastasis, we have parsed the molecular determinants of tumor cell motility into five underlying principles including cell autonomous ability, soluble communication, cell-cell adhesion, cell-matrix adhesion, and integrating these determinants of migration on molecular scaffolds. The current challenge is to implement meaningful and sustainable inhibition of metastasis by developing clinically viable disruption of molecular targets that control these fundamental capabilities. PMID:21664937

  5. Effects of Motility and Adsorption Rate Coefficient on Transport of Bacteria through Saturated Porous Media

    PubMed Central

    Camper, Anne K.; Hayes, Jason T.; Sturman, Paul J.; Jones, Warren L.; Cunningham, Alfred B.

    1993-01-01

    Three strains of Pseudomonas fluorescens with different motility rates and adsorption rate coefficients were injected into porous-medium reactors packed with l-mm-diameter glass spheres. Cell breakthrough, time to peak concentration, tailing, and cell recovery were measured at three interstitial pore velocities (higher than, lower than, and much lower than the maximal bacterial motility rate). All experiments were done with distilled water to reduce the effects of growth and chemotaxis. Contrary to expectations, motility did not result in either early breakthrough or early time to peak concentration at flow velocities below the motility rate. Bacterial size exclusion effects were shown to affect breakthrough curve shape at the very low flow velocity, but no such effect was seen at the higher flow velocity. The tendency of bacteria to adsorb to porous-medium surfaces, as measured by adsorption rate coefficients, profoundly influenced transport characteristics. Cell recoveries were shown to be correlated with the ratio of advective to adsorptive transport in the reactors. Adsorption rate coefficients were found to be better predictors of microbial transport phenomena than individual characteristics, such as size, motility, or porous-medium hydrodynamics. PMID:16349075

  6. 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

  7. The role of motility and chemotaxis in the bacterial colonization of protected surfaces.

    PubMed

    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

  8. 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.).

  9. 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.

  10. Does Laparoscopic and Endoscopic Cooperative Surgery for Gastric Submucosal Tumors Preserve Residual Gastric Motility? Results of a Retrospective Single-Center Study

    PubMed Central

    Waseda, Yohei; Doyama, Hisashi; Inaki, Noriyuki; Nakanishi, Hiroyoshi; Yoshida, Naohiro; Tsuji, Shigetsugu; Takemura, Kenichi; Yamada, Shinya; Okada, Toshihide

    2014-01-01

    Background Laparoscopic and endoscopic cooperative surgery (LECS) is a minimally invasive surgical technique used to resect gastric submucosal tumors with intraluminal growth. Endoscopic submucosal dissection is used to determine the appropriate resection line from within the stomach lumen as it minimizes the stomach wall resection area and prevents postoperative stomach deformity. Although LECS is intended to preserve gastric function, few reports have evaluated postoperative residual gastric motility. Therefore, we conducted a retrospective analysis of patients who underwent LECS to determine the effects of LECS on residual gastric motility. Methods Twenty-two patients underwent endoscopy 3 to 12 months after LECS. Patients were evaluated for endoscopic evidence of gastric motility disorder, namely food residue and occurrence/exacerbation of reflux esophagitis. We considered patients with new onset of gastric symptoms and endoscopic evidence of gastric motility disorder to have clinically relevant gastric motility disorder. We described patient characteristics, tumor location, and surgical findings. Results Two of 22 patients developed clinically relevant gastric motility disorder after LECS. In one of these patients, the symptoms were not severe; only one had reduced dietary intake and had lost weight. We identified clinically relevant gastric motility disorder in two patients with gastrointestinal stromal tumors located in the lesser curvature of the stomach. The major axis of these two tumors was 34 mm and 38 mm. Conclusions Many patients did not have clinically relevant gastric motility disorder after LECS. Further investigation is required to identify predisposing factors for gastric motility disorder. PMID:24968310

  11. Maintenance of motility bias during cyanobacterial phototaxis.

    PubMed

    Chau, Rosanna Man Wah; Ursell, Tristan; Wang, Shuo; Huang, Kerwyn Casey; Bhaya, Devaki

    2015-04-01

    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

  12. Prescriptionless light-cone integrals

    NASA Astrophysics Data System (ADS)

    Suzuki, A. T.; Schmidt, A. G. M.

    2000-01-01

    Perturbative quantum gauge field theory as seen within the perspective of physical gauge choices such as the light-cone gauge entails the emergence of troublesome poles of the type (k\\cdot n)^{-α} in the Feynman integrals. These come from the boson field propagator, where α = 1,2,\\cdots and n^{μ} is the external arbitrary four-vector that defines the gauge proper. This becomes an additional hurdle in the computation of Feynman diagrams, since any graph containing internal boson lines will inevitably produce integrands with denominators bearing the characteristic gauge-fixing factor. How one deals with them has been the subject of research over decades, and several prescriptions have been suggested and tried in the course of time, with failures and successes. However, a more recent development at this fronteer which applies the negative dimensional technique to compute light-cone Feynman integrals shows that we can altogether dispense with prescriptions to perform the calculations. An additional bonus comes to us attached to this new technique, in that not only it renders the light-cone prescriptionless but, by the very nature of it, it can also dispense with decomposition formulas or partial fractioning tricks used in the standard approach to separate pole products of the type (k\\cdot n)^{-α}[(k-p)\\cdot n]^{-β} (β = 1,2,\\cdots ). In this work we demonstrate how all this can be done.

  13. 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.

  14. Effects of Surface Asymmetry on Neuronal Growth

    PubMed Central

    Spedden, Elise; Wiens, Matthew R.; Demirel, Melik C.; Staii, Cristian

    2014-01-01

    Detailed knowledge of how the surface physical properties, such as mechanics, topography and texture influence axonal outgrowth and guidance is essential for understanding the processes that control neuron development, the formation of functional neuronal connections and nerve regeneration. Here we synthesize asymmetric surfaces with well-controlled topography and texture and perform a systematic experimental and theoretical investigation of axonal outgrowth on these substrates. We demonstrate unidirectional axonal bias imparted by the surface ratchet-based topography and quantify the topographical guidance cues that control neuronal growth. We describe the growth cone dynamics using a general stochastic model (Fokker-Planck formalism) and use this model to extract two key dynamical parameters: diffusion (cell motility) coefficient and asymmetric drift coefficient. The drift coefficient is identified with the torque caused by the asymmetric ratchet topography. We relate the observed directional bias in axonal outgrowth to cellular contact guidance behavior, which results in an increase in the cell-surface coupling with increased surface anisotropy. We also demonstrate that the disruption of cytoskeletal dynamics through application of Taxol (stabilizer of microtubules) and Blebbistatin (inhibitor of myosin II activity) greatly reduces the directional bias imparted by these asymmetric surfaces. These results provide new insight into the role played by topographical cues in neuronal growth and could lead to new methods for stimulating neuronal regeneration and the engineering of artificial neuronal tissue. PMID:25184796

  15. Effects of surface asymmetry on neuronal growth.

    PubMed

    Spedden, Elise; Wiens, Matthew R; Demirel, Melik C; Staii, Cristian

    2014-01-01

    Detailed knowledge of how the surface physical properties, such as mechanics, topography and texture influence axonal outgrowth and guidance is essential for understanding the processes that control neuron development, the formation of functional neuronal connections and nerve regeneration. Here we synthesize asymmetric surfaces with well-controlled topography and texture and perform a systematic experimental and theoretical investigation of axonal outgrowth on these substrates. We demonstrate unidirectional axonal bias imparted by the surface ratchet-based topography and quantify the topographical guidance cues that control neuronal growth. We describe the growth cone dynamics using a general stochastic model (Fokker-Planck formalism) and use this model to extract two key dynamical parameters: diffusion (cell motility) coefficient and asymmetric drift coefficient. The drift coefficient is identified with the torque caused by the asymmetric ratchet topography. We relate the observed directional bias in axonal outgrowth to cellular contact guidance behavior, which results in an increase in the cell-surface coupling with increased surface anisotropy. We also demonstrate that the disruption of cytoskeletal dynamics through application of Taxol (stabilizer of microtubules) and Blebbistatin (inhibitor of myosin II activity) greatly reduces the directional bias imparted by these asymmetric surfaces. These results provide new insight into the role played by topographical cues in neuronal growth and could lead to new methods for stimulating neuronal regeneration and the engineering of artificial neuronal tissue. PMID:25184796

  16. Organization of the human trichromatic cone mosaic.

    PubMed

    Hofer, Heidi; Carroll, Joseph; Neitz, Jay; Neitz, Maureen; Williams, David R

    2005-10-19

    Using high-resolution adaptive-optics imaging combined with retinal densitometry, we characterized the arrangement of short- (S), middle- (M), and long- (L) wavelength-sensitive cones in eight human foveal mosaics. As suggested by previous studies, we found males with normal color vision that varied in the ratio of L to M cones (from 1.1:1 to 16.5:1). We also found a protan carrier with an even more extreme L:M ratio (0.37:1). All subjects had nearly identical S-cone densities, indicating independence of the developmental mechanism that governs the relative numerosity of L/M and S cones. L:M cone ratio estimates were correlated highly with those obtained in the same eyes using the flicker photometric electroretinogram (ERG), although the comparison indicates that the signal from each M cone makes a larger contribution to the ERG than each L cone. Although all subjects had highly disordered arrangements of L and M cones, three subjects showed evidence for departures from a strictly random rule for assigning the L and M cone photopigments. In two retinas, these departures corresponded to local clumping of cones of like type. In a third retina, the L:M cone ratio differed significantly at two retinal locations on opposite sides of the fovea. These results suggest that the assignment of L and M pigment, although highly irregular, is not a completely random process. Surprisingly, in the protan carrier, in which X-chromosome inactivation would favor L- or M-cone clumping, there was no evidence of clumping, perhaps as a result of cone migration during foveal development. PMID:16237171

  17. Lichen Secondary Metabolite, Physciosporin, Inhibits Lung Cancer Cell Motility.

    PubMed

    Yang, Yi; Park, So-Yeon; Nguyen, Thanh Thi; Yu, Young Hyun; Nguyen, Tru Van; Sun, Eun Gene; Udeni, Jayalal; Jeong, Min-Hye; Pereira, Iris; Moon, Cheol; Ha, Hyung-Ho; Kim, Kyung Keun; Hur, Jae-Seoun; Kim, Hangun

    2015-01-01

    Lichens produce various unique chemicals that can be used for pharmaceutical purposes. To screen for novel lichen secondary metabolites showing inhibitory activity against lung cancer cell motility, we tested acetone extracts of 13 lichen samples collected in Chile. Physciosporin, isolated from Pseudocyphellaria coriacea (Hook f. & Taylor) D.J. Galloway & P. James, was identified as an effective compound and showed significant inhibitory activity in migration and invasion assays against human lung cancer cells. Physciosporin treatment reduced both protein and mRNA levels of N-cadherin with concomitant decreases in the levels of epithelial-mesenchymal transition markers such as snail and twist. Physciosporin also suppressed KITENIN (KAI1 C-terminal interacting tetraspanin)-mediated AP-1 activity in both the absence and presence of epidermal growth factor stimulation. Quantitative real-time PCR analysis showed that the expression of the metastasis suppressor gene, KAI1, was increased while that of the metastasis enhancer gene, KITENIN, was dramatically decreased by physciosporin. Particularly, the activity of 3'-untranslated region of KITENIN was decreased by physciosporin. Moreover, Cdc42 and Rac1 activities were decreased by physciosporin. These results demonstrated that the lichen secondary metabolite, physciosporin, inhibits lung cancer cell motility through novel mechanisms of action. PMID:26371759

  18. 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.

  19. Region-Specific Microtubule Transport in Motile Cells

    PubMed Central

    Yvon, Anne-Marie C.; Wadsworth, Patricia

    2000-01-01

    Photoactivation and photobleaching of fluorescence were used to determine the mechanism by which microtubules (MTs) are remodeled in PtK2 cells during fibroblast-like motility in response to hepatocyte growth factor (HGF). The data show that MTs are transported during cell motility in an actomyosin-dependent manner, and that the direction of transport depends on the dominant force in the region examined. MTs in the leading lamella move rearward relative to the substrate, as has been reported in newt cells (Waterman-Storer, C.M., and E.D. Salmon. 1997. J. Cell Biol. 139:417–434), whereas MTs in the cell body and in the retraction tail move forward, in the direction of cell locomotion. In the transition zone between the peripheral lamella and the cell body, a subset of MTs remains stationary with respect to the substrate, whereas neighboring MTs are transported either forward, with the cell body, or rearward, with actomyosin retrograde flow. In addition to transport, the photoactivated region frequently broadens, indicating that individual marked MTs are moved either at different rates or in different directions. Mark broadening is also observed in nonmotile cells, indicating that this aspect of transport is independent of cell locomotion. Quantitative measurements of the dissipation of photoactivated fluorescence show that, compared with MTs in control nonmotile cells, MT turnover is increased twofold in the lamella of HGF-treated cells but unchanged in the retraction tail, demonstrating that microtubule turnover is regionally regulated. PMID:11086002

  20. Lichen Secondary Metabolite, Physciosporin, Inhibits Lung Cancer Cell Motility

    PubMed Central

    Yang, Yi; Park, So-Yeon; Nguyen, Thanh Thi; Yu, Young Hyun; Nguyen, Tru Van; Sun, Eun Gene; Udeni, Jayalal; Jeong, Min-Hye; Pereira, Iris; Moon, Cheol; Ha, Hyung-Ho; Kim, Kyung Keun; Hur, Jae-Seoun; Kim, Hangun

    2015-01-01

    Lichens produce various unique chemicals that can be used for pharmaceutical purposes. To screen for novel lichen secondary metabolites showing inhibitory activity against lung cancer cell motility, we tested acetone extracts of 13 lichen samples collected in Chile. Physciosporin, isolated from Pseudocyphellaria coriacea (Hook f. & Taylor) D.J. Galloway & P. James, was identified as an effective compound and showed significant inhibitory activity in migration and invasion assays against human lung cancer cells. Physciosporin treatment reduced both protein and mRNA levels of N-cadherin with concomitant decreases in the levels of epithelial-mesenchymal transition markers such as snail and twist. Physciosporin also suppressed KITENIN (KAI1 C-terminal interacting tetraspanin)-mediated AP-1 activity in both the absence and presence of epidermal growth factor stimulation. Quantitative real-time PCR analysis showed that the expression of the metastasis suppressor gene, KAI1, was increased while that of the metastasis enhancer gene, KITENIN, was dramatically decreased by physciosporin. Particularly, the activity of 3’-untranslated region of KITENIN was decreased by physciosporin. Moreover, Cdc42 and Rac1 activities were decreased by physciosporin. These results demonstrated that the lichen secondary metabolite, physciosporin, inhibits lung cancer cell motility through novel mechanisms of action. PMID:26371759

  1. 21 CFR 876.1725 - Gastrointestinal motility monitoring system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Gastrointestinal motility monitoring system. 876... Gastrointestinal motility monitoring system. (a) Identification. A gastrointestinal motility monitoring system is a... include signal conditioning, amplifying, and recording equipment. This generic type of device includes...

  2. Fundamental conical defects: The d-cone, its e-cone, and its p-cone

    NASA Astrophysics Data System (ADS)

    Seffen, Keith A.

    2016-07-01

    We consider well-known surface disclinations by cutting, joining, and folding pieces of paper card. The resulting shapes have a discrete, folded vertex whose geometry is described easily by Gauss's mapping, in particular, we can relate the degree of angular excess, or deficit, to the size of fold line rotations by the area enclosed by the vector diagram of these rotations. This is well known for the case of a so-called "d-cone" of zero angular deficit, and we formulate the same for a general disclination. This method allows us to observe kinematic properties in a meaningful way without needing to consider equilibrium. Importantly, the simple vector nature of our analysis shows that some disclinations are primitive; and that other types, such as d-cones, are amalgamations of them.

  3. Fundamental conical defects: The d-cone, its e-cone, and its p-cone.

    PubMed

    Seffen, Keith A

    2016-07-01

    We consider well-known surface disclinations by cutting, joining, and folding pieces of paper card. The resulting shapes have a discrete, folded vertex whose geometry is described easily by Gauss's mapping, in particular, we can relate the degree of angular excess, or deficit, to the size of fold line rotations by the area enclosed by the vector diagram of these rotations. This is well known for the case of a so-called "d-cone" of zero angular deficit, and we formulate the same for a general disclination. This method allows us to observe kinematic properties in a meaningful way without needing to consider equilibrium. Importantly, the simple vector nature of our analysis shows that some disclinations are primitive; and that other types, such as d-cones, are amalgamations of them. PMID:27575208

  4. Transition on elliptic cones at Mach 8

    NASA Astrophysics Data System (ADS)

    Huntley, Mark Bradford

    2000-10-01

    Flow visualizations of boundary layer transition on two sharp-nosed elliptic cones at Mach 8 are presented. The elliptic cone is a relevant three-dimensional flow field since it represents a generic hypersonic lifting vehicle shape. Experiments utilize carbon dioxide enhanced Filtered Rayleigh scattering to produce planar single-shot and motion picture images. CO2 is injected into the flow upstream of the tunnel stagnation chamber and subsequently condenses into nanoscale clusters during the nozzle expansion process. The clusters sublimate as they enter the hot boundary layer, and Rayleigh images capture the interface that exists between the regions of condensed (freestream) and sublimated (boundary layer) carbon dioxide. Boundary layers ranging from laminar to late-transitional in character are imaged using streamwise, spanwise, and planform laser sheet orientations. Characteristics of observed instabilities are quantified using pdf profiles, power spectrum analysis, and autocorrelation results derived from single-shot images. A new MHz-rate imaging system is also used to produce motion pictures images and volumetric reconstructions of the boundary layer. The pressure gradient and associated crossflow from the major axis to the minor axis of the cone causes increased growth and subsequent early transition of the centerline boundary layer. The convection velocity and temporal evolution of structures appearing on both the centerline and off-axis regions is studied using cross correlation procedures. Volumetric image sets of the centerline reveal hairpin structures characteristic of the early stages of subsonic turbulent spot formation. In the off-axis regions, planform single-shot images reveal a pattern of finger-like crests in the boundary layer. At higher Reynolds numbers the breakdown of these crests involves the formation of a series of chain-like structures. The behavior appears qualitatively similar to visualizations of crossflow vortex breakdown in

  5. 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

  6. Isolating prompt photons with narrow cones

    NASA Astrophysics Data System (ADS)

    Catani, S.; Fontannaz, M.; Guillet, J. Ph.; Pilon, E.

    2013-09-01

    We discuss the isolation of prompt photons in hadronic collisions by means of narrow isolation cones and the QCD computation of the corresponding cross sections. We reconsider the occurence of large perturbative terms with logarithmic dependence on the cone size and their impact on the fragmentation scale dependence. We cure the apparent perturbative violation of unitarity for small cone sizes, which had been noticed earlier in next-to-leading-order (NLO) calculations, by resumming the leading logarithmic dependence on the cone size. We discuss possible implications regarding the implementation of some hollow cone variants of the cone criterion, which simulate the experimental difficulty to impose isolation inside the region filled by the electromagnetic shower that develops in the calorimeter.

  7. 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.

  8. MOTILITY, AGGRESSION, AND THE BODILY I: AN INTERPRETATION OF WINNICOTT.

    PubMed

    Elkins, Jeremy

    2015-10-01

    Among the central ideas associated with the name of Winnicott, scant mention is made of motility. This is largely attributable to Winnicott himself, who never thematized motility and never wrote a paper specifically devoted to the topic. This paper suggests both that the idea of motility is nonetheless of central significance in Winnicott's thought, and that motility is of central importance in the development and constitution of the bodily I. In elaborating both these suggestions, the paper gives particular attention to the connections between motility, continuity, aggression, and creativity in Winnicott's work. PMID:26443951

  9. 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.

  10. Hydrodynamic Contributions to Amoeboid Cell Motility

    NASA Astrophysics Data System (ADS)

    Lewis, Owen; Guy, Robert

    2012-11-01

    Understanding the methods by which cells move is a fundamental problem in modern biology. Recent evidence has shown that the fluid dynamics of cytoplasm can play a vital role in cellular motility. The slime mold Physarum polycephalum provides an excellent model organism for the study of amoeboid motion. In this research, we use a simply analytic model in conjuction with computational experiments to investigate intracellular fluid flow in a simple model of Physarum. Of particlar interest are stresses generated by cytoplasmic flow which may be used to aid in cellular motility. In our numerical model, the Immersed Boundary Method is used to account for such stresses. We investigate the relationship between contraction waves, flow waves, adhesion, and locomotive forces in an attempt to characterize conditions necessary to generate directed motion.

  11. Hydrodynamic Contributions to Amoeboid Cell Motility

    NASA Astrophysics Data System (ADS)

    Lewis, Owen; Guy, Robert

    2011-11-01

    Understanding the methods by which cells move is a fundamental problem in modern biology. Recent evidence has shown that the fluid dynamics of cytoplasm can play a vital role in cellular motility. The slime mold Physarum polycephalum provides an excellent model organism for the study of amoeboid motion. In this research, we use both analytic and computational models to investigate intracellular fluid flow in a simple model of Physarum. In both models, of we are specifically interested in stresses generated by cytoplasmic flow which act in the direction of cellular motility. In our numerical model, the Immersed Boundary Method is used to account for such stresses. We investigate the relationship between contraction waves, low waves and locomotive forces, and attempt characterize conditions necessary to generate directed motion.

  12. Symbiosis and the origin of eukaryotic motility

    NASA Technical Reports Server (NTRS)

    Margulis, L.; Hinkle, G.

    1991-01-01

    Ongoing work to test the hypothesis of the origin of eukaryotic cell organelles by microbial symbioses is discussed. Because of the widespread acceptance of the serial endosymbiotic theory (SET) of the origin of plastids and mitochondria, the idea of the symbiotic origin of the centrioles and axonemes for spirochete bacteria motility symbiosis was tested. Intracellular microtubular systems are purported to derive from symbiotic associations between ancestral eukaryotic cells and motile bacteria. Four lines of approach to this problem are being pursued: (1) cloning the gene of a tubulin-like protein discovered in Spirocheata bajacaliforniesis; (2) seeking axoneme proteins in spirochets by antibody cross-reaction; (3) attempting to cultivate larger, free-living spirochetes; and (4) studying in detail spirochetes (e.g., Cristispira) symbiotic with marine animals. Other aspects of the investigation are presented.

  13. Soft micromachines with programmable motility and morphology

    NASA Astrophysics Data System (ADS)

    Huang, Hen-Wei; Sakar, Mahmut Selman; Petruska, Andrew J.; Pané, Salvador; Nelson, Bradley J.

    2016-07-01

    Nature provides a wide range of inspiration for building mobile micromachines that can navigate through confined heterogenous environments and perform minimally invasive environmental and biomedical operations. For example, microstructures fabricated in the form of bacterial or eukaryotic flagella can act as artificial microswimmers. Due to limitations in their design and material properties, these simple micromachines lack multifunctionality, effective addressability and manoeuvrability in complex environments. Here we develop an origami-inspired rapid prototyping process for building self-folding, magnetically powered micromachines with complex body plans, reconfigurable shape and controllable motility. Selective reprogramming of the mechanical design and magnetic anisotropy of body parts dynamically modulates the swimming characteristics of the micromachines. We find that tail and body morphologies together determine swimming efficiency and, unlike for rigid swimmers, the choice of magnetic field can subtly change the motility of soft microswimmers.

  14. Soft micromachines with programmable motility and morphology.

    PubMed

    Huang, Hen-Wei; Sakar, Mahmut Selman; Petruska, Andrew J; Pané, Salvador; Nelson, Bradley J

    2016-01-01

    Nature provides a wide range of inspiration for building mobile micromachines that can navigate through confined heterogenous environments and perform minimally invasive environmental and biomedical operations. For example, microstructures fabricated in the form of bacterial or eukaryotic flagella can act as artificial microswimmers. Due to limitations in their design and material properties, these simple micromachines lack multifunctionality, effective addressability and manoeuvrability in complex environments. Here we develop an origami-inspired rapid prototyping process for building self-folding, magnetically powered micromachines with complex body plans, reconfigurable shape and controllable motility. Selective reprogramming of the mechanical design and magnetic anisotropy of body parts dynamically modulates the swimming characteristics of the micromachines. We find that tail and body morphologies together determine swimming efficiency and, unlike for rigid swimmers, the choice of magnetic field can subtly change the motility of soft microswimmers. PMID:27447088

  15. Electrical Signaling in Motile and Primary Cilia

    PubMed Central

    Kleene, Steven J.; Van Houten, Judith L.

    2014-01-01

    Cilia are highly conserved for their structure and also for their sensory functions. They serve as antennae for extracellular information. Whether the cilia are motile or not, they respond to environmental mechanical and chemical stimuli and send signals to the cell body. The information from extracellular stimuli is commonly converted to electrical signals through the repertoire of ion-conducting channels in the ciliary membrane, which results in changes in concentrations of ions, especially calcium ions, in the cilia. These changes, in turn, affect motility and the ability of the signaling pathways in the cilia and cell body to carry on the signal transduction. We review here the activities of ion channels in cilia in animals from protists to vertebrates. PMID:25892740

  16. Hydroxyapatite motility implants in ocular prosthetics.

    PubMed

    Cowper, T R

    1995-03-01

    For the past 5 years, an increasing number of ophthalmologists have been using hydroxyapatite (HA) motility implants after uncomplicated enucleation or evisceration of the eye. Unlike previous implant materials, HA promotes fibrovascular ingrowth and seemingly true integration of the motility implant to the residual ocular structures. As a result, a more stable defect and greater movement of the overlying prosthesis is produced. In addition, the problems of long-term orbital implant migration and the vexing postenucleation socket syndrome are thought to be minimized. This article briefly reviews the history and development of orbital implants and HA implant surgical and prosthetic procedures. It is concluded that HA implant rehabilitation is indicated after most uncomplicated enucleations or eviscerations where there is small likelihood of complication.

  17. [Gastrointestinal motility and possibilities of influencing it].

    PubMed

    Duris, I; Payer, J; Huorka, M; Randus, V; Ondrejka, P

    1994-06-01

    The authors discuss factors which influence the motility of the smooth muscles in the pancreatobiliary region. They investigated some clinical and laboratory parameters after administration of the selective antagonist of calcium influx-Pineverium bromide-Dicetel. The drug influenced significantly in a positive way nausea, flatulence, pain and chronically elevated amylases. The authors mention a cycle of possible neurohumoral changes with which specific calcium channel antagonists could interfere. PMID:8073641

  18. [Motility of human spermatozoa (author's transl)].

    PubMed

    David, G; Serres, C; Escalier, D

    1981-01-01

    Microcinematography has permitted the analysis of human sperm motility and the definition of various parameters which can be used to characterize such movements. The locomotor apparatus of the sperm flagellum consists of an axoneme to which has been added the dense fibers and the fibrous sheath. A dysfunction of flagellar locomotion may be caused by mutations resulting in various structural defects of which the most common affect the dynein arms.

  19. 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.

  20. Characterization of swarming motility in Citrobacter freundii.

    PubMed

    Cong, Yanguang; Wang, Jing; Chen, Zhijin; Xiong, Kun; Xu, Qiwang; Hu, Fuquan

    2011-04-01

    Bacterial swarming motility is a flagella-dependent translocation on the surface environment. It has received extensive attention as a population behavior involving numerous genes. Here, we report that Citrobacter freundii, an opportunistic pathogen, exhibits swarming movement on a solid medium surface with appropriate agar concentration. The swarming behavior of C. freundii was described in detail. Insertional mutagenesis with transposon Mini-Tn5 was carried out to discover genetic determinants related to the swarming of C. freundii. A number of swarming genes were identified, among which flhD, motA, motB, wzx, rfaL, rfaJ, rfbX, rfaG, rcsD, rcsC, gshB, fabF, dam, pgi, and rssB have been characterized previously in other species. In mutants related to lipopolysaccharide synthesis and RcsCDB signal system, a propensity to form poorly motile bacterial aggregates on the agar surface was observed. The aggregates hampered bacterial surface migration. In several mutants, the insertion sites were identified to be in the ORF of yqhC, yeeZ, CKO_03941, glgC, and ttrA, which have never been shown to be involved in swarming. Our results revealed several novel characteristics of swarming motility in C. freundii which are worthy of further study.

  1. Hyaluronan stimulates pancreatic cancer cell motility

    PubMed Central

    Cheng, Xiao-Bo; Kohi, Shiro; Koga, Atsuhiro; Hirata, Keiji; Sato, Norihiro

    2016-01-01

    Hyaluronan (HA) accumulates in pancreatic ductal adenocarcinoma (PDAC), but functional significance of HA in the aggressive phenotype remains unknown. We used different models to investigate the effect of HA on PDAC cell motility by wound healing and transwell migration assay. Changes in cell motility were examined in 8 PDAC cell lines in response to inhibition of HA production by treatment with 4-methylumbelliferone (4-MU) and to promotion by treatment with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or by co-culture with tumor-derived stromal fibroblasts. We also investigated changes in cell motility by adding exogenous HA. Additionally, mRNA expressions of hyaluronan synthases and hyaluronidases were examined using real time RT-PCR. Inhibition of HA by 4-MU significantly decreased the migration, whereas promotion of HA by TPA or co-culture with tumor-derived fibroblasts significantly increased the migration of PDAC cells. The changes in HA production by these treatments tended to be associated with changes in HAS3 mRNA expression. Furthermore, addition of exogenous HA, especially low-molecular-weight HA, significantly increased the migration of PDAC cells. These findings suggest that HA stimulates PDAC cell migration and thus represents an ideal therapeutic target to prevent invasion and metastasis. PMID:26684359

  2. Effect of total laryngectomy on esophageal motility

    SciTech Connect

    Hanks, J.B.; Fisher, S.R.; Meyers, W.C.; Christian, K.C.; Postlethwait, R.W.; Jones, R.S.

    1981-01-01

    Total laryngectomy for cancer can result in dysphagia and altered esophageal motility. Manometric changes in the upper esophageal sphincter (UES), and in proximal and distal esophageal function have been reported. However, most studies have failed to take into account radiation therapy and appropriate controls. We selected ten male patients (54.3 +/- 1.9 yr) for longitudinal manometric evaluation prior to laryngectomy then at two weeks and again six months later. No patient received preoperative radiation therapy, had a previous history of esophageal surgery, or developed a postoperative wound infection or fistula. Seven of ten patients had positive nodes and received 6,000-6,600 rads postoperative radiation therapy. Preoperatively 4 of 10 patients complained of dysphagia which did not significantly change following surgery and radiation. Two of three patients who did not complain of dysphagia preoperatively and received radiation postoperatively developed dysphagia. No patient without dysphagia preoperatively who received no radiation therapy developed symptoms. Our studies show that laryngectomy causes alterations in the UES resting and peak pressures but not in the proximal or distal esophagus, or the lower esophageal sphincter. These data also imply radiation therapy may be associated with progressive alterations in motility and symptomatology. Further study regarding the effects of radiation on esophageal motility and function are urged.

  3. Swimming Motility Reduces Deposition to Silica Surfaces

    SciTech Connect

    Lu, Nanxi; Massoudieh, Arash; Liang, Xiaomeng; Hu, Dehong; Kamai, Tamir; Ginn, Timothy R.; Zilles, Julie L.; Nguyen, Thanh H.

    2015-01-01

    The role of swimming motility on bacterial transport and fate in porous media was evaluated. We present microscopic evidence showing that strong swimming motility reduces attachment of Azotobacter vinelandii cells to silica surfaces. Applying global and cluster statistical analyses to microscopic videos taken under non-flow conditions, wild type, flagellated A. vinelandii strain DJ showed strong swimming ability with an average speed of 13.1 μm/s, DJ77 showed impaired swimming averaged at 8.7 μm/s, and both the non-flagellated JZ52 and chemically treated DJ cells were non-motile. Quantitative analyses of trajectories observed at different distances above the collector of a radial stagnation point flow cell (RSPF) revealed that both swimming and non-swimming cells moved with the flow when at a distance of at least 20 μm from the collector surface. Near the surface, DJ cells showed both horizontal and vertical movement diverging them from reaching surfaces, while chemically treated DJ cells moved with the flow to reach surfaces, suggesting that strong swimming reduced attachment. In agreement with the RSPF results, the deposition rates obtained for two-dimensional multiple-collector micromodels were also lowest for DJ, while DJ77 and JZ52 showed similar values. Strong swimming specifically reduced deposition on the upstream surfaces of the micromodel collectors.

  4. Knockdown of Inner Arm Protein IC138 in Trypanosoma brucei Causes Defective Motility and Flagellar Detachment

    PubMed Central

    Wilson, Corinne S.; Chang, Alex J.; Greene, Rebecca; Machado, Sulynn; Parsons, Matthew W.; Takats, Taylor A.; Zambetti, Luke J.; Springer, Amy L.

    2015-01-01

    Motility in the protozoan parasite Trypanosoma brucei is conferred by a single flagellum, attached alongside the cell, which moves the cell forward using a beat that is generated from tip-to-base. We are interested in characterizing components that regulate flagellar beating, in this study we extend the characterization of TbIC138, the ortholog of a dynein intermediate chain that regulates axonemal inner arm dynein f/I1. TbIC138 was tagged In situ-and shown to fractionate with the inner arm components of the flagellum. RNAi knockdown of TbIC138 resulted in significantly reduced protein levels, mild growth defect and significant motility defects. These cells tended to cluster, exhibited slow and abnormal motility and some cells had partially or fully detached flagella. Slight but significant increases were observed in the incidence of mis-localized or missing kinetoplasts. To document development of the TbIC138 knockdown phenotype over time, we performed a detailed analysis of flagellar detachment and motility changes over 108 hours following induction of RNAi. Abnormal motility, such as slow twitching or irregular beating, was observed early, and became progressively more severe such that by 72 hours-post-induction, approximately 80% of the cells were immotile. Progressively more cells exhibited flagellar detachment over time, but this phenotype was not as prevalent as immotility, affecting less than 60% of the population. Detached flagella had abnormal beating, but abnormal beating was also observed in cells with no flagellar detachment, suggesting that TbIC138 has a direct, or primary, effect on the flagellar beat, whereas detachment is a secondary phenotype of TbIC138 knockdown. Our results are consistent with the role of TbIC138 as a regulator of motility, and has a phenotype amenable to more extensive structure-function analyses to further elucidate its role in the control of flagellar beat in T. brucei. PMID:26555902

  5. Knockdown of Inner Arm Protein IC138 in Trypanosoma brucei Causes Defective Motility and Flagellar Detachment.

    PubMed

    Wilson, Corinne S; Chang, Alex J; Greene, Rebecca; Machado, Sulynn; Parsons, Matthew W; Takats, Taylor A; Zambetti, Luke J; Springer, Amy L

    2015-01-01

    Motility in the protozoan parasite Trypanosoma brucei is conferred by a single flagellum, attached alongside the cell, which moves the cell forward using a beat that is generated from tip-to-base. We are interested in characterizing components that regulate flagellar beating, in this study we extend the characterization of TbIC138, the ortholog of a dynein intermediate chain that regulates axonemal inner arm dynein f/I1. TbIC138 was tagged In situ-and shown to fractionate with the inner arm components of the flagellum. RNAi knockdown of TbIC138 resulted in significantly reduced protein levels, mild growth defect and significant motility defects. These cells tended to cluster, exhibited slow and abnormal motility and some cells had partially or fully detached flagella. Slight but significant increases were observed in the incidence of mis-localized or missing kinetoplasts. To document development of the TbIC138 knockdown phenotype over time, we performed a detailed analysis of flagellar detachment and motility changes over 108 hours following induction of RNAi. Abnormal motility, such as slow twitching or irregular beating, was observed early, and became progressively more severe such that by 72 hours-post-induction, approximately 80% of the cells were immotile. Progressively more cells exhibited flagellar detachment over time, but this phenotype was not as prevalent as immotility, affecting less than 60% of the population. Detached flagella had abnormal beating, but abnormal beating was also observed in cells with no flagellar detachment, suggesting that TbIC138 has a direct, or primary, effect on the flagellar beat, whereas detachment is a secondary phenotype of TbIC138 knockdown. Our results are consistent with the role of TbIC138 as a regulator of motility, and has a phenotype amenable to more extensive structure-function analyses to further elucidate its role in the control of flagellar beat in T. brucei. PMID:26555902

  6. 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.

  7. 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.

  8. Physics of protein motility and motor proteins

    NASA Astrophysics Data System (ADS)

    Kolomeisky, Anatoly B.

    2013-09-01

    Motor proteins are enzymatic molecules that transform chemical energy into mechanical motion and work. They are critically important for supporting various cellular activities and functions. In the last 15 years significant progress in understanding the functioning of motor proteins has been achieved due to revolutionary breakthroughs in single-molecule experimental techniques and strong advances in theoretical modelling. However, microscopic mechanisms of protein motility are still not well explained, and the collective efforts of many scientists are needed in order to solve these complex problems. In this special section the reader will find the latest advances on the difficult road to mapping motor proteins dynamics in various systems. Recent experimental developments have allowed researchers to monitor and to influence the activity of single motor proteins with a high spatial and temporal resolution. It has stimulated significant theoretical efforts to understand the non-equilibrium nature of protein motility phenomena. The latest results from all these advances are presented and discussed in this special section. We would like to thank the scientists from all over the world who have reported their latest research results for this special section. We are also grateful to the staff and editors of Journal of Physics: Condensed Matter for their invaluable help in handling all the administrative and refereeing activities. The field of motor proteins and protein motility is fast moving, and we hope that this collection of articles will be a useful source of information in this highly interdisciplinary area. Physics of protein motility and motor proteins contents Physics of protein motility and motor proteinsAnatoly B Kolomeisky Identification of unique interactions between the flexible linker and the RecA-like domains of DEAD-box helicase Mss116 Yuan Zhang, Mirkó Palla, Andrew Sun and Jung-Chi Liao The load dependence of the physical properties of a molecular motor

  9. Identification of appropriate cone length to avoid positive cone margin in high grade cervical intraepithelial neoplasia

    PubMed Central

    Tsuda, Naotake; Nishio, Shin; Ushijima, Kimio

    2016-01-01

    Objective To identify key factors for predicting positive cone margin and appropriate cone length. Methods We retrospectively reviewed the margin status of patients who received conization with high grade cervical intraepithelial neoplasia, along with other factors such as patient age, parity, preoperative cytology, size of disease, type of transformation zone, and cone length from patient records. Cut-off value of cone length was analyzed in women younger than 40 years old because we design conization with minimum length especially for women who wish for future pregnancy. Cut-off value of cone length was defined as length corresponds to estimated probability of positive cone margin equal to 0.1 by logistic regression analysis with variables selected by stepwise methods. Results Among 300 patients, 75 patients had positive cone margin. Multivariable analysis revealed that squamous cell carcinoma at preoperative cytology (p=0.001), 2 or more quadrant disease (p=0.011), and shorter cone length (p<0.001) were risk factors for positive cone margin. Stepwise methods identified cone length and size of lesion as important variables. With this condition, cut-off value of cone length was estimated as 15 mm in single quadrant disease and 20 mm in 2 or more quadrant disease, respectively. Conclusion We identified the independent risk factors of positive cone margin and identified the cut-off value of cone length to avoid positive cone margin in women younger than 40 years old. Conization should be performed not only according to colposcopic findings including type of transformation zone but size of disease and cone length. PMID:27401478

  10. The structure and emplacement of cinder cone fields

    NASA Technical Reports Server (NTRS)

    Settle, M.

    1979-01-01

    The paper examines the structure and emplacement of cinder cone fields. Terrestrial cinder cone fields occur in volcanic provinces upon the flanks of major volcanoes or within relatively flat-lying volcanic fields. Measurements of cone shape and distribution were made in three volcano cone fields and three platform cone fields, and it was found that modal average values of cone basal diameter are on the order of 300 to 400 m within volcano cone fields and 900 to 1000 m within platform cone fields. The average morphometric parameters for the six fields indicate that cone diameter is positively correlated with cone separation distance, and that the size and spacing of cinder cones formed on the flanks of volcanoes is less than the size and spacing of cones constructed in volcanic fields.

  11. Panoramic cone beam computed tomography

    SciTech Connect

    Chang Jenghwa; Zhou Lili; Wang Song; Clifford Chao, K. S.

    2012-05-15

    Purpose: Cone-beam computed tomography (CBCT) is the main imaging tool for image-guided radiotherapy but its functionality is limited by a small imaging volume and restricted image position (imaged at the central instead of the treatment position for peripheral lesions to avoid collisions). In this paper, the authors present the concept of ''panoramic CBCT,'' which can image patients at the treatment position with an imaging volume as large as practically needed. Methods: In this novel panoramic CBCT technique, the target is scanned sequentially from multiple view angles. For each view angle, a half scan (180 deg. + {theta}{sub cone} where {theta}{sub cone} is the cone angle) is performed with the imaging panel positioned in any location along the beam path. The panoramic projection images of all views for the same gantry angle are then stitched together with the direct image stitching method (i.e., according to the reported imaging position) and full-fan, half-scan CBCT reconstruction is performed using the stitched projection images. To validate this imaging technique, the authors simulated cone-beam projection images of the Mathematical Cardiac Torso (MCAT) thorax phantom for three panoramic views. Gaps, repeated/missing columns, and different exposure levels were introduced between adjacent views to simulate imperfect image stitching due to uncertainties in imaging position or output fluctuation. A modified simultaneous algebraic reconstruction technique (modified SART) was developed to reconstruct CBCT images directly from the stitched projection images. As a gold standard, full-fan, full-scan (360 deg. gantry rotation) CBCT reconstructions were also performed using projection images of one imaging panel large enough to encompass the target. Contrast-to-noise ratio (CNR) and geometric distortion were evaluated to quantify the quality of reconstructed images. Monte Carlo simulations were performed to evaluate the effect of scattering on the image quality and

  12. Cone penetrometer demonstration standard startup review checklist

    SciTech Connect

    KRIEG, S.A.

    1998-11-09

    Startup readiness for the Cone Penetrometer Demonstration in AX Tank Farm will be verified through the application of a Standard Startup Review Checklist. This is a listing of those items essential to demonstrating readiness to start the Cone Penetrometer Demonstration in AX Tank Farm.

  13. System design description cone penetrometer system

    SciTech Connect

    Seda, R.Y., Westinghouse Hanford

    1996-08-12

    The system design description documents in detail the design of the cone penetrometer system. The systems includes the cone penetrometer physical package, raman spectroscopy package and moisture sensor package. Information pertinent to the system design, development, fabrication and testing is provided.

  14. Recoverin depletion accelerates cone photoresponse recovery

    PubMed Central

    Zang, Jingjing; Keim, Jennifer; Kastenhuber, Edda; Gesemann, Matthias; Neuhauss, Stephan C. F.

    2015-01-01

    The neuronal Ca2+-binding protein Recoverin has been shown to regulate phototransduction termination in mammalian rods. Here we identify four recoverin genes in the zebrafish genome, rcv1a, rcv1b, rcv2a and rcv2b, and investigate their role in modulating the cone phototransduction cascade. While Recoverin-1b is only found in the adult retina, the other Recoverins are expressed throughout development in all four cone types, except Recoverin-1a, which is expressed only in rods and UV cones. Applying a double flash electroretinogram (ERG) paradigm, downregulation of Recoverin-2a or 2b accelerates cone photoresponse recovery, albeit at different light intensities. Exclusive recording from UV cones via spectral ERG reveals that knockdown of Recoverin-1a alone has no effect, but Recoverin-1a/2a double-knockdowns showed an even shorter recovery time than Recoverin-2a-deficient larvae. We also showed that UV cone photoresponse kinetics depend on Recoverin-2a function via cone-specific kinase Grk7a. This is the first in vivo study demonstrating that cone opsin deactivation kinetics determine overall photoresponse shut off kinetics. PMID:26246494

  15. Increase in cone biomass and terpenophenolics in hops ( Humulus lupulus L.) by treatment with prohexadione-calcium.

    PubMed

    Kavalier, Adam R; Pitra, Nicholi J; Koelling, Jared M; Coles, Mark C; Kennelly, Edward J; Matthews, Paul D

    2011-06-22

    Humulus lupulus L. (hop), a specialty crop bred for flavor characteristics of the inflorescence, is an essential ingredient in beer. Hop inflorescences, commonly known as hop cones, contain terpenophenolic compounds, which are important for beer flavoring and of interest in biomedical research. Hop breeders focus their efforts on increasing cone biomass and terpenophenolic content. As an alternative to traditional breeding, hops were treated with prohexadione-calcium (Pro-Ca), a growth inhibitor previously shown to have positive agronomic effects in several crops. Application of Pro-Ca to hop plants during cone maturation induced increases in cone biomass production by 1.5-19.6% and increased terpenophenolic content by 9.1-87.3%; however, some treatments also induced significant decreases in terpenophenolic content. Induced changes in cone biomass production and terpenophenolic accumulation were most dependent on cultivar and the developmental stage at which plants were treated. PMID:21598976

  16. Campylobacter jejuni pdxA Affects Flagellum-Mediated Motility to Alter Host Colonization

    PubMed Central

    Asakura, Hiroshi; Hashii, Noritaka; Uema, Masashi; Kawasaki, Nana; Sugita-Konishi, Yoshiko; Igimi, Shizunobu; Yamamoto, Shigeki

    2013-01-01

    Vitamin B6 (pyridoxal-5'-phosphate, PLP) is linked to a variety of biological functions in prokaryotes. Here, we report that the pdxA (putative 4-hydroxy-L-threonine phosphate dehydrogenase) gene plays a pivotal role in the PLP-dependent regulation of flagellar motility, thereby altering host colonization in a leading foodborne pathogen, Campylobacter jejuni. A C. jejuni pdxA mutant failed to produce PLP and exhibited a coincident loss of flagellar motility. Mass spectrometric analyses showed a 3-fold reduction in the main flagellar glycan pseudaminic acid (Pse) associated with the disruption of pdxA. The pdxA mutant also exhibited reduced growth rates compared with the WT strain. Comparative metabolomic analyses revealed differences in respiratory/energy metabolism between WT C. jejuni and the pdxA mutant, providing a possible explanation for the differential growth fitness between the two strains. Consistent with the lack of flagellar motility, the pdxA mutant showed impaired motility-mediated responses (bacterial adhesion, ERK1/2 activation, and IL-8 production) in INT407 cells and reduced colonization of chickens compared with the WT strain. Overall, this study demonstrated that the pdxA gene affects the PLP-mediated flagellar motility function, mainly through alteration of Pse modification, and the disruption of this gene also alters the respiratory/energy metabolisms to potentially affect host colonization. Our data therefore present novel implications regarding the utility of PLP and its dependent enzymes as potent target(s) for the control of this pathogen in the poultry host. PMID:23936426

  17. Unique characteristics of cones in Central Elysium Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Noguchi, Rina; Kurita, Kei

    2015-06-01

    Martian magmatism within recent several hundreds of millions years is still controversial. Central Elysium Planitia (CEP) is suspected as a site of the latest magmatism on Mars, but hot debates have been caused as for the origin of this flat plain. Cones in CEP are expected to be a key to resolve this controversy. In previous works, there are 2 models proposed for the origin of CEP cones: volcanic rootless cone (e.g. Jaeger et al., 2007) and periglacial pingo (e.g. Burr et al., 2002; Page et al., 2009). In this study, we described detail morphology, distribution and size of CEP cones by using high-resolution images and topographic data. CEP cones are classified into 3 morphological types: Single Cone (SC), Double Cone (DC), and Lotus Fruit Cone (LC). DC has an inner cone in the summit crater of the outer cone, and LC has several inner cones in the summit crater of the outer cone. Several cones have moat structure around the edifice with peripheral rise. DCs and LCs are located in very flat areas of Athabasca Valles in the vicinity of Cerberus Fossae, while SCs distribute in the entire region of CEP. We compared CEP cones with terrestrial rootless cones and pingos in aerial photos. In Lake Myvatn, Iceland, there exist rootless cones which resemble DCs and LCs in CEP. Based on the similarities with terrestrial analogies, we concluded that the most feasible origin of CEP cones is rootless cones.

  18. Primate Short-Wavelength Cones Share Molecular Markers with Rods

    PubMed Central

    Craft, Cheryl M.; Huang, Jing; Possin, Daniel E.; Hendrickson, Anita

    2015-01-01

    Macaca, Callithrix jacchus marmoset monkey, Pan troglodytes chim- panzee and human retinas were examined to define if short wavelength (S) cones share molecular markers with L&M cone or rod photoreceptors. S cones showed consistent differences in their immunohistochemical staining and expression levels compared to L&M cones for “rod” Arrestin1 (S-Antigen), “cone” Arrestin4, cone alpha transducin, and Calbindin. Our data verify a similar pattern of expression in these primate retinas and provide clues to the structural divergence of rods and S cones versus L&M cones, suggesting S cone retinal function is “intermediate” between them. PMID:24664680

  19. Septins promote stress fiber–mediated maturation of focal adhesions and renal epithelial motility

    PubMed Central

    Dolat, Lee; Hunyara, John L.; Bowen, Jonathan R.; Karasmanis, Eva Pauline; Elgawly, Maha; Galkin, Vitold E.

    2014-01-01

    Organogenesis and tumor metastasis involve the transformation of epithelia to highly motile mesenchymal-like cells. Septins are filamentous G proteins, which are overexpressed in metastatic carcinomas, but their functions in epithelial motility are unknown. Here, we show that a novel network of septin filaments underlies the organization of the transverse arc and radial (dorsal) stress fibers at the leading lamella of migrating renal epithelia. Surprisingly, septin depletion resulted in smaller and more transient and peripheral focal adhesions. This phenotype was accompanied by a highly disorganized lamellar actin network and rescued by the actin bundling protein α-actinin-1. We show that preassembled actin filaments are cross-linked directly by Septin 9 (SEPT9), whose expression is increased after induction of renal epithelial motility with the hepatocyte growth factor. Significantly, SEPT9 overexpression enhanced renal cell migration in 2D and 3D matrices, whereas SEPT9 knockdown decreased migration. These results suggest that septins promote epithelial motility by reinforcing the cross-linking of lamellar stress fibers and the stability of nascent focal adhesions. PMID:25349260

  20. Computational Trials: Unraveling Motility Phenotypes, Progression Patterns, and Treatment Options for Glioblastoma Multiforme

    PubMed Central

    Raman, Fabio; Scribner, Elizabeth; Saut, Olivier; Wenger, Cornelia; Colin, Thierry; Fathallah-Shaykh, Hassan M.

    2016-01-01

    Glioblastoma multiforme is a malignant brain tumor with poor prognosis and high morbidity due to its invasiveness. Hypoxia-driven motility and concentration-driven motility are two mechanisms of glioblastoma multiforme invasion in the brain. The use of anti-angiogenic drugs has uncovered new progression patterns of glioblastoma multiforme associated with significant differences in overall survival. Here, we apply a mathematical model of glioblastoma multiforme growth and invasion in humans and design computational trials using agents that target angiogenesis, tumor replication rates, or motility. The findings link highly-dispersive, moderately-dispersive, and hypoxia-driven tumors to the patterns observed in glioblastoma multiforme treated by anti-angiogenesis, consisting of progression by Expanding FLAIR, Expanding FLAIR + Necrosis, and Expanding Necrosis, respectively. Furthermore, replication rate-reducing strategies (e.g. Tumor Treating Fields) appear to be effective in highly-dispersive and moderately-dispersive tumors but not in hypoxia-driven tumors. The latter may respond to motility-reducing agents. In a population computational trial, with all three phenotypes, a correlation was observed between the efficacy of the rate-reducing agent and the prolongation of overall survival times. This research highlights the potential applications of computational trials and supports new hypotheses on glioblastoma multiforme phenotypes and treatment options. PMID:26756205

  1. The unique paradigm of spirochete motility and chemotaxis

    PubMed Central

    Charon, Nyles W.; Cockburn, Andrew; Li, Chunhao; Liu, Jun; Miller, Kelly A.; Miller, Michael R.; Motaleb, Md.; Wolgemuth, Charles W.

    2013-01-01

    Spirochete motility is enigmatic: It differs from the motility of most other bacteria in that the entire bacterium is involved in translocation in the absence of external appendages. Using the Lyme disease spirochete Borrelia burgdorferi (Bb) as a model system, we explore the current research on spirochete motility and chemotaxis. Bb has periplasmic flagella (PFs) subterminally attached to each end of the protoplasmic cell cylinder, and surrounding the cell is an outer membrane. These internal helically shaped PFs allow the spirochete to swim by generating backward-moving waves by rotation. Exciting advances using cryoelectron microscopy tomography are presented with respect to in situ analysis of cell, PF, and motor structure. In addition, advances in the dynamics of motility, chemotaxis, gene regulation, and the role of motility and chemotaxis in the life cycle of Bb are summarized. The results indicate that the motility paradigms of flagellated bacteria do not apply to these unique bacteria. PMID:22994496

  2. The unique paradigm of spirochete motility and chemotaxis.

    PubMed

    Charon, Nyles W; Cockburn, Andrew; Li, Chunhao; Liu, Jun; Miller, Kelly A; Miller, Michael R; Motaleb, Md A; Wolgemuth, Charles W

    2012-01-01

    Spirochete motility is enigmatic: It differs from the motility of most other bacteria in that the entire bacterium is involved in translocation in the absence of external appendages. Using the Lyme disease spirochete Borrelia burgdorferi (Bb) as a model system, we explore the current research on spirochete motility and chemotaxis. Bb has periplasmic flagella (PFs) subterminally attached to each end of the protoplasmic cell cylinder, and surrounding the cell is an outer membrane. These internal helix-shaped PFs allow the spirochete to swim by generating backward-moving waves by rotation. Exciting advances using cryoelectron tomography are presented with respect to in situ analysis of cell, PF, and motor structure. In addition, advances in the dynamics of motility, chemotaxis, gene regulation, and the role of motility and chemotaxis in the life cycle of Bb are summarized. The results indicate that the motility paradigms of flagellated bacteria do not apply to these unique bacteria.

  3. Gastrointestinal motility in space motion sickness

    NASA Technical Reports Server (NTRS)

    Thornton, William E.; Linder, Barry J.; Moore, Thomas P.; Pool, Sam L.

    1987-01-01

    Gastrointestinal symptoms in space motion sickness (SMS) are significantly different from those in ordinary motion sickness (MS). Recording and tabulation of sounds was the only technique that could be used as a measure of motility during spaceflight operations. There were 17 subjects, six unaffected by SMS, who made ambulatory recordings preflight and inflight. With one exception, all those affected had sharply reduced sounds, while those unaffected had increases or moderate reductions. The mechanism of vomiting in SMS appears to be secondary to this ileus, in contrast to vomiting in ordinary MS, where the emesis center is thought to be directly triggered by the vestibular system.

  4. Dynamic Clustering in Suspension of Motile Bacteria

    NASA Astrophysics Data System (ADS)

    Zhang, Hepeng; Chen, Xiao; Yang, Xiang; Yang, Mingcheng

    2015-03-01

    Bacteria suspension exhibits a wide range of collective phenomena arising from interactions between individual cells. Here we investigate dynamic clusters of motile bacteria near an air-liquid interface. Cell in a cluster orient its flagella perpendicular to the interface and generate attractive radial fluid flow that leads to cluster formation. Rotating cell also creates tangential forces on neighbors that sets clusters into counter-clockwise rotation. We construct a numerical model of self-propelled particles that interact via pair-wise forces extracted from hydrodynamic calculations; such a model reproduces many properties of observed cluster dynamics.

  5. Gravity duals of boundary cones

    NASA Astrophysics Data System (ADS)

    Camps, Joan

    2016-09-01

    The replica trick defines Rényi entropies as partition functions on conically singular geometries. We discuss their gravity duals: regular bulk solutions to the Einstein equations inducing conically singular metrics at the boundary. When the conical singularity is supported on a flat or spherical surface, these solutions are rewritings of the hyperbolic black hole. For more general shapes, these solutions are new. We construct them perturbatively in a double expansion in the distance and strength of the conical singularity, and extract the vacuum polarisation due to the cone. Recent results about the structure of logarithmic divergences of Rényi entropies are reproduced — in particular, f b ≠ f c . We discuss in detail the dynamical resolution of the singularity in the bulk. This resolution is in agreement with a previous proposal, and indicates a non-minimal settling to the `splitting problem': an apparent ambiguity in the holographic entropy formula of certain theories with higher derivatives.

  6. Elastic cone for Chinese calligraphy

    NASA Astrophysics Data System (ADS)

    Cai, Fenglei; Li, Haisheng

    2014-01-01

    The brush plays an important role in creating Chinese calligraphy. We regard a single bristle of a writing brush as an elastic rod and the brush tuft absorbing ink as an elastic cone, which naturally deforms according to the force exerted on it when painting on a paper, and the brush footprint is formed by the intersection region between the deformed tuft and the paper plane. To efficiently generate brush strokes, this paper introduces interpolation and texture mapping approach between two adjacent footprints, and automatically applies bristle-splitting texture to the stroke after long-time painting. Experimental results demonstrate that our method is effective and reliable. Users can create realistic calligraphy in real time.

  7. Loss-cone instability: Wave saturation by particle trapping

    SciTech Connect

    Zaslavsky, A.; Krafft, C.; Volokitin, A.

    2007-12-15

    The nonlinear mechanisms governing the interactions between whistler or lower hybrid waves and loss-cone type particles' distributions in magnetized plasmas are of great importance if one considers the major role that waves of frequency below the electron cyclotron frequency play in space and thermonuclear fusion plasmas. Up to now, most of the numerical simulations have been devoted to study the nonlinear processes at work when the plasma is weakly relativistic and when the anisotropy of the particles' distributions leads to the so-called maser instability. However, in many interesting cases, the particles' energies are sufficiently weak to ensure the validity of the nonrelativistic approximation. In this framework, the paper studies the interaction at normal cyclotron resonances between lower hybrid waves and electron distributions presenting loss-cone like features. A theoretical Hamiltonian model and a corresponding numerical symplectic code are used to evidence and to explain the nonlinear mechanisms at work at the saturation stage of the loss-cone instability. Moreover, simple analytical expressions and scaling laws have been derived for the linear growth rates and the wave amplitude at saturation.

  8. The effect of vaginal lubricants on sperm motility in vitro.

    PubMed

    Goldenberg, R L; White, R

    1975-09-01

    Apart from the documentation of the spermicidal effects of KY Jelly and Surgilube, little information about the effect of vaginal lubricants on sperm motility has been available. Fifteen substances utilizable as vaginal lubricants were therefore tested for their effect on sperm motility in vitro. Petroleum jelly and glycerin had minimal detrimental effects on motility and apparently are the lubricants of choice when an infertility problem exists.

  9. Chemokinetic motility responses of the cyanobacterium oscillatoria terebriformis

    NASA Technical Reports Server (NTRS)

    Richardson, Laurie L.; Castenholz, Richard W.

    1989-01-01

    Oscillatoria terebriformis, a gliding, filamentous, thermophilic cyanobacterium, exhibited an inhibition of gliding motility upon exposure to fructose. The observed response was transient, and the duration of nonmotility was directly proportional to the concentration of fructose. Upon resumption of motility, the rate of motility was also inversely proportional to the concentration of fructose. Sulfide caused a similar response. The effect of sulfide was specific and not due to either anoxia or negative redox potential. Exposure to glucose, acetate, lactate, or mat interstitial water did not elicit any motility response.

  10. Motility Evaluation in the Patient with Inflammatory Bowel Disease.

    PubMed

    Abdalla, Sherine M; Kalra, Gorav; Moshiree, Baha

    2016-10-01

    Patients with inflammatory bowel disease (IBD) suffer frequently from functional bowel diseases (FBD) and motility disorders. Management of FBD and motility disorders in IBD combined with continued treatment of a patient's IBD symptoms will likely lead to better clinical outcomes and improve the patient's quality of life. The goals of this review were to summarize the most recent literature on motility disturbances in patients with IBD and to give a brief overview of the ranges of motility disturbances, from reflux disease to anorectal disorders, and discuss their diagnosis and specific management. PMID:27633599

  11. Motility Evaluation in the Patient with Inflammatory Bowel Disease.

    PubMed

    Abdalla, Sherine M; Kalra, Gorav; Moshiree, Baha

    2016-10-01

    Patients with inflammatory bowel disease (IBD) suffer frequently from functional bowel diseases (FBD) and motility disorders. Management of FBD and motility disorders in IBD combined with continued treatment of a patient's IBD symptoms will likely lead to better clinical outcomes and improve the patient's quality of life. The goals of this review were to summarize the most recent literature on motility disturbances in patients with IBD and to give a brief overview of the ranges of motility disturbances, from reflux disease to anorectal disorders, and discuss their diagnosis and specific management.

  12. Thyroid Hormone Signaling and Cone Photoreceptor Viability.

    PubMed

    Ma, Hongwei; Ding, Xi-Qin

    2016-01-01

    Thyroid hormone (TH) signaling regulates cell proliferation, differentiation, and apoptosis. In the retina, TH signaling plays a central role in cone opsin expression. TH signaling inhibits S opsin expression, stimulates M opsin expression, and promotes dorsal-ventral opsin patterning. TH signaling has also been associated with cone photoreceptor viability. Treatment with thyroid hormone triiodothyronine (T3) or induction of high T3 by deleting the hormone-inactivating enzyme type 3 iodothyronine deiodinase (DIO3) causes cone death in mice. This effect is reversed by deletion of the TH receptor (TR) gene. Consistent with the T3 treatment effect, suppressing TH signaling preserves cones in mouse models of retinal degeneration. The regulation of cone survival by TH signaling appears to be independent of its regulatory role in cone opsin expression. The mechanism by which TH signaling regulates cone viability remains to be identified. The current understanding of TH signaling regulation in photoreceptor viability suggests that suppressing TH signaling locally in the retina may represent a novel strategy for retinal degeneration management. PMID:26427466

  13. Modal content of living human cone photoreceptors

    PubMed Central

    Liu, Zhuolin; Kocaoglu, Omer P.; Turner, Timothy L.; Miller, Donald T.

    2015-01-01

    Decades of experimental and theoretical investigations have established that photoreceptors capture light based on the principles of optical waveguiding. Yet considerable uncertainty remains, even for the most basic prediction as to whether photoreceptors support more than a single waveguide mode. To test for modal behavior in human cone photoreceptors in the near infrared, we took advantage of adaptive-optics optical coherence tomography (AO-OCT, λc = 785 nm) to noninvasively image in three dimensions the reflectance profile of cones. Modal content of reflections generated at the cone inner segment and outer segment junction (IS/OS) and cone outer segment tip (COST) was examined over a range of cone diameters in 1,802 cones from 0.6° to 10° retinal eccentricity. Second moment analysis in conjunction with theoretical predictions indicate cone IS and OS have optical properties consistent of waveguides, which depend on segment diameter and refractive index. Cone IS was found to support a single mode near the fovea (≤3°) and multiple modes further away (>4°). In contrast, no evidence of multiple modes was found in the cone OSs. The IS/OS and COST reflections share a common optical aperture, are most circular near the fovea, show no orientation preference, and are temporally stable. We tested mode predictions of a conventional step-index fiber model and found that in order to fit our AO-OCT results required a lower estimate of the IS refractive index and introduction of an IS focusing/tapering effect. PMID:26417509

  14. The Cone-specific Visual Cycle

    PubMed Central

    Wang, Jin-Shan; Kefalov, Vladimir J

    2010-01-01

    Cone photoreceptors mediate our daytime vision and function under bright and rapidly-changing light conditions. As their visual pigment is destroyed in the process of photoactivation, the continuous function of cones imposes the need for rapid recycling of their chromophore and regeneration of their pigment. The canonical retinoid visual cycle through the retinal pigment epithelium cells recycles chromophore and supplies it to both rods and cones. However, shortcomings of this pathway, including its slow rate and competition with rods for chromophore, have led to the suggestion that cones might use a separate mechanism for recycling of chromophore. In the past four decades biochemical studies have identified enzymatic activities consistent with recycling chromophore in the retinas of cone-dominant animals, such as chicken and ground squirrel. These studies have led to the hypothesis of a cone-specific retina visual cycle. The physiological relevance of these studies was controversial for a long time and evidence for the function of this visual cycle emerged only in very recent studies and will be the focus of this review. The retina visual cycle supplies chromophore and promotes pigment regeneration only in cones but not in rods. This pathway is independent of the pigment epithelium and instead involves the Müller cells in the retina, where chromophore is recycled and supplied selectively to cones. The rapid supply of chromophore through the retina visual cycle is critical for extending the dynamic range of cones to bright light and for their rapid dark adaptation following exposure to light. The importance of the retina visual cycle is emphasized also by its preservation through evolution as its function has now been demonstrated in species ranging from salamander to zebrafish, mouse, primate, and human. PMID:21111842

  15. Small intestine motility development in newborn mammals.

    PubMed

    Woliński, Jarosław; Słupecka-Ziemilska, Monika; Boryczka, Maria; Grzesiak, Paulina; Kwiatkowski, Jakub; Kotarba, Grzegorz

    2016-01-01

    Since the beginning of the 20th century, researchers have been working to improve the understanding of gastrointestinal motility. The first major discovery was the observation of a migrating myoelectric complex that turned out to be a universal occurrence among vertebrates. Further inquires resulted in a detailed description of its development during different stages of ontogeny. Some time before that, a cornerstone had been laid for a breakthrough that would come years later. That cornerstone came in the form of interstitial cells of Cajal whose true role could not be discerned until the discovery of a CD117 receptor - their main marker. With the ability to precisely mark interstitial cells of Cajal, a wave of subsequent new experiments and observations connected them to the occurrence of slow waves and allowed an understanding of the mechanism responsible for their generation. Some of these findings suggested that Cajal cells might have a role in the development of several motility disorders thus opening an avenue of research that requires the usage of both traditional and advanced diagnostic methods. PMID:27416626

  16. Intensification of ciliary motility by extracellular ATP.

    PubMed

    Ovadyahu, D; Eshel, D; Priel, Z

    1988-01-01

    Ciliary metachronism and motility were examined optically in tissue cultures from frog palate epithelium as a function of extracellular ATP concentration in the range of 10(-7)-10(-3) M. The main findings were: a) upon addition of ATP the metachronal wavelength increased by a factor of up to 2. b) the velocity of the metachronal wave increased by a factor of up to 5. c) the frequency of ciliary beating increased by a factor of up to 2-3, the increase being temperature insensitive in the range of 15 degrees C-25 degrees C. d) the area under the 1-second FFT spectrum decreased by a factor of up to 2.5. e) the energy of the metachronal wave is increased by a factor of up to 9.5. f) all the spectrum parameters are subject to influence by ATP, as also by ADP and AMP. However, there are pronounced differences in the various responses to them. Based on these findings, physical aspects of the rate increase of particle transport caused by addition of extracellular ATP are explained. A plausible overall chemical mechanism causing pronounced changes in ciliary motility is discussed.

  17. Bacterial Motility Reveals Unknown Molecular Organization.

    PubMed

    Duchesne, Ismaël; Rainville, Simon; Galstian, Tigran

    2015-11-17

    The water solubility of lyotropic liquid crystals (LCs) makes them very attractive to study the behavior of biological microorganisms in an environment where local symmetry is broken (as often encountered in nature). Several recent studies have shown a dramatic change in the behavior of flagellated bacteria when swimming in solutions of the lyotropic LC disodium cromoglycate (DSCG). In this study, the movements of Escherichia coli bacteria in DSCG-water solutions of different concentrations are observed to improve our understanding of this phenomenon. In addition, the viscosity of DSCG aqueous solutions is measured as a function of concentration at room temperature. We also experimentally identify a previously undescribed isotropic pretransition zone where bacteria start sticking to each other and to surfaces. Simple estimations show that the unbalanced osmotic pressure induced depletion force might be responsible for this sticking phenomenon. An estimate of the bacteria propulsive force and the DSCG aggregates length (versus concentration) are calculated from the measured viscosity of the medium. All these quantities are found to undergo a strong increase in the pretransition zone, starting at a threshold concentration of 6±1 wt % DSCG that is well below the known isotropic-LC transition (∼10 wt %). This study also shines light on the motility of flagellated bacteria in realistic environments, and it opens new avenues for interesting applications such as the use of motile microorganisms to probe the physical properties of their host or smart bandages that could guide bacteria out of wounds.

  18. Rumen motility during induced hyper- and hypocalcaemia.

    PubMed

    Jørgensen, R J; Nyengaard, N R; Hara, S; Enemark, J M; Andersen, P H

    1998-01-01

    Rumen motility was recorded on an experimental cow by means of telemetric signal transfer from strain gauge force transducers fixed surgically on the peritoneal surface of the rumen wall in the left flank. The normocalcaemic cow was given a standard milk fever treatment with calcium borogluconate (400 ml with 14 mg Ca/ml) intravenously. Transient clinical signs were: decreased rumination, muscle ticks, salivation and a heart rate reduction of 20%. Rectal temperature remained unaltered. Frequency of rumen contractions was reduced up to 40% whereas amplitude of contractions did not deviate from baseline values. Hypocalcaemia was induced in a second experiment by iv infusion of Na2EDTA. At 0.60 mmol/l ionized blood calcium periods of no motility were recorded whereas inactivity of rumen activity was persistent at 0.55 mmol/l ionized blood calcium. The cow went down at 0.45-0.48 mmol/l ionized blood calcium at which point the heart rate was increased by 40%. The high sensitivity of the method employed allowed the conclusion that already at a concentration of ionized blood calcium at 1.0 mmol/l both frequency and amplitude of rumen contractions decreased rapidly although eating behaviour and rumination appeared unaffected during the short term observation periods. Implications of this finding towards health and production in transition cows are discussed.

  19. Intracellular Microrheology of Motile Amoeba proteus

    NASA Astrophysics Data System (ADS)

    Rogers, S.; Waigh, T.; Lu, J.

    2008-04-01

    The motility of motile Amoeba proteus was examined using the technique of passive particle tracking microrheology, with the aid of newly-developed particle tracking software, a fast digital camera and an optical microscope. We tracked large numbers of endogeneous particles in the amoebae, which displayed subdiffusive motion at short time scales, corresponding to thermal motion in a viscoelastic medium, and superdiffusive motion at long time scales due to the convection of the cytoplasm. Subdiffusive motion was characterised by a rheological scaling exponent of 3/4 in the cortex, indicative of the semiflexible dynamics of the actin fibres. We observed shear-thinning in the flowing endoplasm, where exponents increased with increasing flow rate; i.e. the endoplasm became more fluid-like. The rheology of the cortex is found to be isotropic, reflecting an isotropic actin gel. A clear difference was seen between cortical and endoplasmic layers in terms of both viscoelasticity and flow velocity, where the profile of the latter is close to a Poiseuille flow for a Newtonian fluid.

  20. Single molecule analysis of cytoplasmic dynein motility

    NASA Astrophysics Data System (ADS)

    Yildiz, Ahmet

    2014-03-01

    Cytoplasmic dynein is a homodimeric AAA + motor that transports a multitude of cargos towards the microtubule (MT) minus end. The mechanism of dynein motility remains unclear, due to its large size (2.6 MDa) and the complexity of its structure. By tracking the stepping motion of both heads at nanometer resolution, we observed that dynein heads move independently along the MT, in contrast to hand over hand movement of kinesins and myosin. Stepping behavior of the heads varies as a function of interhead separation and establishing the basis of high variability in dynein step size. By engineering the mechanical and catalytic properties of the dynein motor domain, we show that a rigid linkage between monomers and dimerization between N-terminal tail domains are not essential for processive movement. Instead, dynein processivity minimally requires the linker domain of one active monomer to be attached to an inert MT tether retaining only the MT-binding domain. The release of a dynein monomer from the MT can be mediated either by nucleotide binding or external load. Nucleotide dependent release is inhibited by the tension on the linker domain at high interhead separations. Tension dependent release is highly asymmetric, with faster release towards the minus-end. Reversing the asymmetry of the MT binding interface results in plus end directed motility, even though the force was generated by the dynein motor activity. On the basis of these measurements, we propose a model that describes the basis of dynein processivity, directionality and force generation.

  1. Gastrointestinal motility and functional gastrointestinal diseases.

    PubMed

    Kusano, Motoyasu; Hosaka, Hiroko; Kawada, Akiyo; Kuribayashi, Shiko; Shimoyama, Yasuyuki; Zai, Hiroaki; Kawamura, Osamu; Yamada, Masanobu

    2014-01-01

    Digestive tract motility patterns are closely related to the pathophysiology of functional gastrointestinal diseases (FGID), and these patterns differ markedly between the interdigestive period and the postprandial period. The characteristic motility pattern in the interdigestive period is so-called interdigestive migrating contraction (IMC). IMCs have a housekeeping role in the intestinal tract, and could also be related to FGID. IMCs arising from the stomach are called gastrointestinal IMCs (GI-IMC), while IMCs arising from the duodenum without associated gastric contractions are called intestinal IMCs (I-IMC). It is thought that I-IMCs are abnormal in FGID. Transport of food residue to the duodenum via gastric emptying is one of the most important postprandial functions of the stomach. In patients with functional dyspepsia (FD), abnormal gastric emptying is a possible mechanism of gastric dysfunction. Accordingly, delayed gastric emptying has attracted attention, with prokinetic agents and herbal medicines often being administered in Japan to accelerate gastric emptying in patients who have anorexia associated with dyspepsia. Recently, we found that addition of monosodium L-glutamate (MSG) to a high-calorie liquid diet rich in casein promoted gastric emptying in healthy men. Therefore, another potential method of improving delayed gastric emptying could be activation of chemosensors that stimulate the autonomic nervous system of the gastrointestinal tract, suggesting a role for MSG in the management of delayed gastric emptying in patients with FD.

  2. Small intestine motility development in newborn mammals.

    PubMed

    Woliński, Jarosław; Słupecka-Ziemilska, Monika; Boryczka, Maria; Grzesiak, Paulina; Kwiatkowski, Jakub; Kotarba, Grzegorz

    2016-01-01

    Since the beginning of the 20th century, researchers have been working to improve the understanding of gastrointestinal motility. The first major discovery was the observation of a migrating myoelectric complex that turned out to be a universal occurrence among vertebrates. Further inquires resulted in a detailed description of its development during different stages of ontogeny. Some time before that, a cornerstone had been laid for a breakthrough that would come years later. That cornerstone came in the form of interstitial cells of Cajal whose true role could not be discerned until the discovery of a CD117 receptor - their main marker. With the ability to precisely mark interstitial cells of Cajal, a wave of subsequent new experiments and observations connected them to the occurrence of slow waves and allowed an understanding of the mechanism responsible for their generation. Some of these findings suggested that Cajal cells might have a role in the development of several motility disorders thus opening an avenue of research that requires the usage of both traditional and advanced diagnostic methods.

  3. Mechanics and polarity in cell motility

    NASA Astrophysics Data System (ADS)

    Ambrosi, D.; Zanzottera, A.

    2016-09-01

    The motility of a fish keratocyte on a flat substrate exhibits two distinct regimes: the non-migrating and the migrating one. In both configurations the shape is fixed in time and, when the cell is moving, the velocity is constant in magnitude and direction. Transition from a stable configuration to the other one can be produced by a mechanical or chemotactic perturbation. In order to point out the mechanical nature of such a bistable behaviour, we focus on the actin dynamics inside the cell using a minimal mathematical model. While the protein diffusion, recruitment and segregation govern the polarization process, we show that the free actin mass balance, driven by diffusion, and the polymerized actin retrograde flow, regulated by the active stress, are sufficient ingredients to account for the motile bistability. The length and velocity of the cell are predicted on the basis of the parameters of the substrate and of the cell itself. The key physical ingredient of the theory is the exchange among actin phases at the edges of the cell, that plays a central role both in kinematics and in dynamics.

  4. Epilepsy-induced motility of differentiated neurons.

    PubMed

    Chai, Xuejun; Münzner, Gert; Zhao, Shanting; Tinnes, Stefanie; Kowalski, Janina; Häussler, Ute; Young, Christina; Haas, Carola A; Frotscher, Michael

    2014-08-01

    Neuronal ectopia, such as granule cell dispersion (GCD) in temporal lobe epilepsy (TLE), has been assumed to result from a migration defect during development. Indeed, recent studies reported that aberrant migration of neonatal-generated dentate granule cells (GCs) increased the risk to develop epilepsy later in life. On the contrary, in the present study, we show that fully differentiated GCs become motile following the induction of epileptiform activity, resulting in GCD. Hippocampal slice cultures from transgenic mice expressing green fluorescent protein in differentiated, but not in newly generated GCs, were incubated with the glutamate receptor agonist kainate (KA), which induced GC burst activity and GCD. Using real-time microscopy, we observed that KA-exposed, differentiated GCs translocated their cell bodies and changed their dendritic organization. As found in human TLE, KA application was associated with decreased expression of the extracellular matrix protein Reelin, particularly in hilar interneurons. Together these findings suggest that KA-induced motility of differentiated GCs contributes to the development of GCD and establish slice cultures as a model to study neuronal changes induced by epileptiform activity.

  5. Electrical coupling between cones in turtle retina.

    PubMed Central

    Detwiler, P B; Hodgkin, A L

    1979-01-01

    1. The electrical coupling between cones of known spectral sensitivity in the peripheral part of the turtle's retina was studied by passing current through a micro-electrode inserted into one cone and recording with a second micro-electrode inserted into a neighbouring cone. 2. Spatial sensitivity profiles were determined by recording flash responses to a long narrow strip of light which was moved across the impaled cones in orthogonal directions. These measurements gave both the length constant lambda of electrical spread in the cone network and the separation of the two cones. 3. The cone separation determined from the spatial profiles agreed closely with that measured directly by injecting a fluorescent dye into two cones. 4. The length constant lambda varied from 18 to 39 micron with a mean of 25 micron for red-sensitive cones and 26 micron for green-sensitive cones. 5. The majority of cone pairs studied were electrically coupled provided they had the same spectral sensitivity and were separated by less than 60 micron: thirty-two out of thirty-six red-red pairs, two out of two green-green pairs, none out of eight red-green pairs: no blue cones were observed. 6. The strength of electrical coupling was expressed as a mutual resistance defined as the voltage in one cell divided by the current flowing into the other. Mutual resistances decreased from a maximum value of about 30 M omega at separations close to zero to 0.2 M omega, the lower limit of detectable coupling at separations of about 60 micron. Mutual resistances were always positive and were independent of which cell was directly polarized. The coupling seemed to be ohmic and any rectification or non-linearity probably arose in the cone membranes rather than in the coupling resistances. 7. The results were analysed in terms of the Lamb & Simon (1977) theories of square and hexagonal lattices, which approximate to the continuous sheet model except in the case of the cone to which current is applied. 8. The

  6. Large-sized tubular graphite cones with nanotube tips

    SciTech Connect

    Shang, N.G.; Jiang, X.

    2005-10-17

    Tubular graphite cones (TGCs) have been grown on planar steel substrates by microwave plasma-assisted chemical vapor deposition with a high concentration of methane and at a high substrate temperature. The largest TGCs can reach 110 {mu}m in length and 10 {mu}m in diameter at the root. Unique TGCs terminated in long extruding carbon nanotube tips are realized. Scanning micro-Raman spectroscopy of individual TGCs shows a high crystallinity of the tips and more disordered structure of the roots. A possible growth mechanism of TGCs is presented.

  7. Distribution and specificity of S-cone ("blue cone") signals in subcortical visual pathways.

    PubMed

    Martin, Paul R; Lee, Barry B

    2014-03-01

    We review here the distribution of S-cone signals and properties of S-cone recipient receptive fields in subcortical pathways. Nearly everything we know about S-cone signals in the subcortical visual system comes from the study of visual systems in cats and primates (monkeys); in this review, we concentrate on results from macaque and marmoset monkeys. We discuss segregation of S-cone recipient (blue-on and blue-off) receptive fields in the dorsal lateral geniculate nucleus and describe their receptive field properties. We treat in some detail the question of detecting weak S-cone signals as an introduction for newcomers to the field. Finally, we briefly consider the question on how S-cone signals are distributed among nongeniculate targets. PMID:24555883

  8. Distribution and specificity of S-cone ("blue cone") signals in subcortical visual pathways.

    PubMed

    Martin, Paul R; Lee, Barry B

    2014-03-01

    We review here the distribution of S-cone signals and properties of S-cone recipient receptive fields in subcortical pathways. Nearly everything we know about S-cone signals in the subcortical visual system comes from the study of visual systems in cats and primates (monkeys); in this review, we concentrate on results from macaque and marmoset monkeys. We discuss segregation of S-cone recipient (blue-on and blue-off) receptive fields in the dorsal lateral geniculate nucleus and describe their receptive field properties. We treat in some detail the question of detecting weak S-cone signals as an introduction for newcomers to the field. Finally, we briefly consider the question on how S-cone signals are distributed among nongeniculate targets.

  9. Balancing Thymocyte Adhesion and Motility: A Functional Linkage Between β1 Lntegrins and The Motility Receptor RHAMM

    PubMed Central

    Gares, Sheryl L.

    2000-01-01

    Thymocyte differentiation involves several processes that occur in different anatomic sites within the thymus. Therefore, thymocytes must have the ability to respond to signals received from stromal cells and adopt either adhesive or motile behavior. We will discuss our data indicating human thymocytes use α4β1 integrin, α5β1 integrin and RHAMM to mediate these activities. Immature multinegative (MN; CD3–4–8–19-) thymocytes use α4β1 and α5β1 integrins to mediate weak and strong adhesion. This subset also uses α4β1 integrin to mediate motility. As thymocytes differentiate, they begin to express and use RHAMM to mediate motility in conjunction with α4β1 and α5β1 integrins. Motile thymocytes use β1 integrins to maintain weakly adhesive contacts with substrate to provide traction for locomoting cells, thus weak adhesion is a requirement of motile behavior. Hyaluronan (HA) is also required by thymocytes to mediate motility. HA binding to cell surface RHAMM redistributes intracellular RHAMM to the cell surface where it functions to mediate motility. We propose that the decision to maintain adhesive or motile behavior is based on the balance between low and high avidity binding conformations of β1 integrins on thymocytes and that RHAMM:HA interactions decrease high avidity binding conformations of integrins pushing the balance toward motile behavior. PMID:11097213

  10. PAK4 kinase activity and somatic mutation promote carcinoma cell motility and influence inhibitor sensitivity

    PubMed Central

    Whale, Andrew D.; Dart, Anna; Holt, Mark; Jones, Gareth E.; Wells, Claire M.

    2012-01-01

    Hepatocyte growth factor (HGF) and its receptor (c-Met) are associated with cancer cell motility and invasiveness. p21-activated kinase 4 (PAK4), a potential therapeutic target, is recruited to and activated by c-Met. In response, PAK4 phosphorylates LIM kinase 1 (LIMK1) in an HGF-dependent manner in metastatic prostate carcinoma cells. PAK4 overexpression is known to induce increased cell migration speed but the requirement for kinase activity has not been established. We have used a panel of PAK4 truncations and mutations in a combination of over-expression and RNAi rescue experiments to determine the requirement for PAK4 kinase activity during carcinoma cell motility downstream of HGF. We find that neither the kinase domain alone nor a PAK4 mutant unable to bind Cdc42 is able to fully rescue cell motility in a PAK4-deficient background. Nevertheless, we find that PAK4 kinase activity and associated LIMK1 activity are essential for carcinoma cell motility, highlighting PAK4 as a potential anti-metastatic therapeutic target. We also show here that overexpression of PAK4 harboring a somatic mutation, E329K, increased the HGF-driven motility of metastatic prostate carcinoma cells. E329 lies within the G-loop region of the kinase. Our data suggest E329K mutation leads to a modest increase in kinase activity conferring resistance to competitive ATP inhibitors in addition to promoting cell migration. The existence of such a mutation may have implications for the development of PAK4-specific competitive ATP inhibitors should PAK4 be further explored for clinical inhibition. PMID:22689056

  11. Nonlinear Resonance Cones and Converging Plasma Blobs

    NASA Astrophysics Data System (ADS)

    Agmon, Nathan; Pribyl, Patrick; Gekelman, Walter; Wise, Joe; Katz, Cami; Ha, Chis; Baker, Bob

    2013-10-01

    Electric field resonance cones have been shown to create density disturbances in cold, magnetized plasmas. Two circular antennas in the LAPTAG experimental plasma device were used to create converging, nonlinear resonance cones. The nonlinear electrostatic field is produced by large amplitude RF (ERF/nkTe >> 1). A movable probe, powered by a computerized motor and consisting of three mutually orthogonal electric dipoles, is used to measure the electric field of the cones which become distorted at large amplitudes. A 2D movable Langmuir probe was used to determine localized density perturbations after turn-off of the RF power. A density blob moving at 3-5 times the ion sound speed has been observed to propagate away (for at least 20 cm) from the focus of the cone. Two ring antennas produced colliding blobs. The physics of the collision will be described. Work performed at the Basic Plasma Science Facility supported by DOE and NSF.

  12. Some inversion formulas for the cone transform

    NASA Astrophysics Data System (ADS)

    Terzioglu, Fatma

    2015-11-01

    Several novel imaging applications have lead recently to a variety of Radon type transforms, where integration is made over a family of conical surfaces. We call them cone transforms (in 2D they are also called V-line or broken ray transforms). Most prominently, they are present in the so called Compton camera imaging that arises in medical diagnostics, astronomy, and lately in homeland security applications. Several specific incarnations of the cone transform have been considered separately. In this paper, we address the most general (and overdetermined) cone transform, obtain integral relations between cone and Radon transforms in {{{R}}}n, and a variety of inversion formulas. In many applications (e.g., in homeland security), the signal to noise ratio is very low. So, if overdetermined data is collected (as in the case of Compton imaging), attempts to reduce the dimensionality might lead to essential elimination of the signal. Thus, our main concentration is on obtaining formulas involving overdetermined data.

  13. Homologies among Coniferophyte cones: further observations

    NASA Astrophysics Data System (ADS)

    Grauvogel-Stamm, Léa; Galtier, Jean

    1998-04-01

    A reinvestigation of the Triassic conifer pollen cone of Darneya shows evidence that clusters of pollen sacs are attached (adnate), at regular intervals, to the upper side of the stalk and that the distribution of stomata is restricted to the apical part of the abaxial side of the peltate scale. These features and others, such as the commissure visible on the stalk and the scale, suggest a dual nature of the male scale complex of Darneya which therefore is interpreted as an abaxial bract fused with an adaxial fertile shoot bearing several clusters of pollen sacs. This conifer pollen cone is thus considered as a compound strobilus (inflorescence) homologous with the female cone of the conifers and therefore with the cones, both male and female, of the cordaites.

  14. DEFORMATION OF SCORIA CONE BY CONDUIT PRESSURIZATION

    SciTech Connect

    E.S. Gaffney; B. Damjanac; D. Krier; G. Valentine

    2005-08-26

    A simplified mechanical model is used to simulate the deformation of a scoria cone due to pressurization of magma in a feeder conduit. The scoria cone is modeled as consisting of a cone of stabilized scoria with an axial region of loose scoria (height h{sub 1}), all overlying a vertically oriented cylindrical conduit intruded into rhyolite tuff country rock. For our analyses, the conduit is filled with basalt magma, usually with the upper length (h{sub 2}) solidified. The style of deformation of the cone depends on both h{sub 1} and h{sub 2}. If magma is prevented from hydrofracturing out of the conduit (as, for example, might be the case if the magma is surrounded by a solidified, but plastically deformable layer acting as a gasket backed up by the brittle country rock) pressures in the magma can build to 10s of MPa. When h{sub 1} is 100 m, not unusual for a small isolated basaltic cinder cone, the magma pressure needed to destabilize the cone when molten magma extends all the way to the original ground surface (h{sub 2} = 0) is only about one-third of the pressure when the upper part of the conduit is solidified (h{sub 2} = 25m). In the former case, almost the entire upper third of the cone is at failure in tension when the configuration becomes unstable. In the latter case, small portions of the surface of the cone are failing in tension when instability occurs, but a large volume in the central core of the cone is failing in shear or compressions. These results may provide insight into the status of volcanic plumbing, either past or present, beneath scoria cones. Field observations at the Lathrop Wells volcano in southern Nevada identify structures at the outer edge just below the crater rim that appear to be inward-dipping listric normal faults. This may indicate that, near the end of its active stage, the cone was close to failing in this fashion. A companion paper suggests that such a failure could have been quite energetic had it occurred.

  15. Laser radiation and motility patterns of human sperm

    SciTech Connect

    Lenzi, A.; Claroni, F.; Gandini, L.; Lombardo, F.; Barbieri, C.; Lino, A.; Dondero, F. )

    1989-01-01

    Human sperm were exposed in vitro to laser radiation. An increase in progressive sperm motility was associated with a faster rate of sperm ATP consumption. Computer-assisted analysis of sperm motility confirmed the positive effect of laser irradiation on velocity and linearity of sperm.

  16. Detection and genomic characterization of motility in Lactobacillus curvatus: confirmation of motility in a species outside the Lactobacillus salivarius clade.

    PubMed

    Cousin, Fabien J; Lynch, Shónagh M; Harris, Hugh M B; McCann, Angela; Lynch, Denise B; Neville, B Anne; Irisawa, Tomohiro; Okada, Sanae; Endo, Akihito; O'Toole, Paul W

    2015-02-01

    Lactobacillus is the largest genus within the lactic acid bacteria (LAB), with almost 180 species currently identified. Motility has been reported for at least 13 Lactobacillus species, all belonging to the Lactobacillus salivarius clade. Motility in lactobacilli is poorly characterized. It probably confers competitive advantages, such as superior nutrient acquisition and niche colonization, but it could also play an important role in innate immune system activation through flagellin–Toll-like receptor 5 (TLR5) interaction. We now report strong evidence of motility in a species outside the L. salivarius clade, Lactobacillus curvatus (strain NRIC0822). The motility of L. curvatus NRIC 0822 was revealed by phase-contrast microscopy and soft-agar motility assays. Strain NRIC 0822 was motile at temperatures between 15 °C and 37 °C, with a range of different carbohydrates, and under varying atmospheric conditions. We sequenced the L. curvatus NRIC 0822 genome, which revealed that the motility genes are organized in a single operon and that the products are very similar (>98.5% amino acid similarity over >11,000 amino acids) to those encoded by the motility operon of Lactobacillus acidipiscis KCTC 13900 (shown for the first time to be motile also). Moreover, the presence of a large number of mobile genetic elements within and flanking the motility operon of L. curvatus suggests recent horizontal transfer between members of two distinct Lactobacillus clades: L. acidipiscis in the L. salivarius clade and L. curvatus inthe L. sakei clade. This study provides novel phenotypic, genetic, and phylogenetic insights into flagellum-mediated motility in lactobacilli.

  17. Detection and Genomic Characterization of Motility in Lactobacillus curvatus: Confirmation of Motility in a Species outside the Lactobacillus salivarius Clade

    PubMed Central

    Cousin, Fabien J.; Lynch, Shónagh M.; Harris, Hugh M. B.; McCann, Angela; Lynch, Denise B.; Neville, B. Anne; Irisawa, Tomohiro; Okada, Sanae; Endo, Akihito

    2014-01-01

    Lactobacillus is the largest genus within the lactic acid bacteria (LAB), with almost 180 species currently identified. Motility has been reported for at least 13 Lactobacillus species, all belonging to the Lactobacillus salivarius clade. Motility in lactobacilli is poorly characterized. It probably confers competitive advantages, such as superior nutrient acquisition and niche colonization, but it could also play an important role in innate immune system activation through flagellin–Toll-like receptor 5 (TLR5) interaction. We now report strong evidence of motility in a species outside the L. salivarius clade, Lactobacillus curvatus (strain NRIC 0822). The motility of L. curvatus NRIC 0822 was revealed by phase-contrast microscopy and soft-agar motility assays. Strain NRIC 0822 was motile at temperatures between 15°C and 37°C, with a range of different carbohydrates, and under varying atmospheric conditions. We sequenced the L. curvatus NRIC 0822 genome, which revealed that the motility genes are organized in a single operon and that the products are very similar (>98.5% amino acid similarity over >11,000 amino acids) to those encoded by the motility operon of Lactobacillus acidipiscis KCTC 13900 (shown for the first time to be motile also). Moreover, the presence of a large number of mobile genetic elements within and flanking the motility operon of L. curvatus suggests recent horizontal transfer between members of two distinct Lactobacillus clades: L. acidipiscis in the L. salivarius clade and L. curvatus in the L. sakei clade. This study provides novel phenotypic, genetic, and phylogenetic insights into flagellum-mediated motility in lactobacilli. PMID:25501479

  18. Electron-cyclotron maser instability driven by a loss-cone distribution

    SciTech Connect

    Lau, Y.Y.; Chu, K.

    1983-01-24

    It is shown that the electron-cyclotron maser instabilities may readily be excited in a plasma with a loss-cone distribution when the electron temperature exceeds a few tens of kiloelectronvolts. The growth rate is typically a few percent of the electron-cyclotron frequency. The appearance of the instability can be avoided by proper control of the plasma density.

  19. Profilin Interaction with Actin Filament Barbed End Controls Dynamic Instability, Capping, Branching, and Motility

    PubMed Central

    Pernier, Julien; Shekhar, Shashank; Jegou, Antoine; Guichard, Bérengère; Carlier, Marie-France

    2016-01-01

    Summary Cell motility and actin homeostasis depend on the control of polarized growth of actin filaments. Profilin, an abundant regulator of actin dynamics, supports filament assembly at barbed ends by binding G-actin. Here, we demonstrate how, by binding and destabilizing filament barbed ends at physiological concentrations, profilin also controls motility, cell migration, and actin homeostasis. Profilin enhances filament length fluctuations. Profilin competes with Capping Protein at barbed ends, which generates a lower amount of profilin-actin than expected if barbed ends were tightly capped. Profilin competes with barbed end polymerases, such as formins and VopF, and inhibits filament branching by WASP-Arp2/3 complex by competition for filament barbed ends, accounting for its as-yet-unknown effects on motility and metastatic cell migration observed in this concentration range. In conclusion, profilin is a major coordinator of polarized growth of actin filaments, controlled by competition between barbed end cappers, trackers, destabilizers, and filament branching machineries. PMID:26812019

  20. Wild-type p53 controls cell motility and invasion by dual regulation of MET expression

    PubMed Central

    Hwang, Chang-Il; Matoso, Andres; Corney, David C.; Flesken-Nikitin, Andrea; Körner, Stefanie; Wang, Wei; Boccaccio, Carla; Thorgeirsson, Snorri S.; Comoglio, Paolo M.; Hermeking, Heiko; Nikitin, Alexander Yu.

    2011-01-01

    Recent observations suggest that p53 mutations are responsible not only for growth of primary tumors but also for their dissemination. However, mechanisms involved in p53-mediated control of cell motility and invasion remain poorly understood. By using the primary ovarian surface epithelium cell culture, we show that conditional inactivation of p53 or expression of its mutant forms results in overexpression of MET receptor tyrosine kinase, a crucial regulator of invasive growth. At the same time, cells acquire increased MET-dependent motility and invasion. Wild-type p53 negatively regulates MET expression by two mechanisms: (i) transactivation of MET-targeting miR-34, and (ii) inhibition of SP1 binding to MET promoter. Both mechanisms are not functional in p53 absence, but mutant p53 proteins retain partial MET promoter suppression. Accordingly, MET overexpression, cell motility, and invasion are particularly high in p53-null cells. These results identify MET as a critical effector of p53 and suggest that inhibition of MET may be an effective antimetastatic approach to treat cancers with p53 mutations. These results also show that the extent of advanced cancer traits, such as invasion, may be determined by alterations in individual components of p53/MET regulatory network. PMID:21831840

  1. Microspectrophotometric evidence for cone monochromacy in sharks

    NASA Astrophysics Data System (ADS)

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks—the rays and chimaeras—are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λmax 484-518 nm) and cone (λmax 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  2. Design of a trichromatic cone array.

    PubMed

    Garrigan, Patrick; Ratliff, Charles P; Klein, Jennifer M; Sterling, Peter; Brainard, David H; Balasubramanian, Vijay

    2010-02-01

    Cones with peak sensitivity to light at long (L), medium (M) and short (S) wavelengths are unequal in number on the human retina: S cones are rare (<10%) while increasing in fraction from center to periphery, and the L/M cone proportions are highly variable between individuals. What optical properties of the eye, and statistical properties of natural scenes, might drive this organization? We found that the spatial-chromatic structure of natural scenes was largely symmetric between the L, M and S sensitivity bands. Given this symmetry, short wavelength attenuation by ocular media gave L/M cones a modest signal-to-noise advantage, which was amplified, especially in the denser central retina, by long-wavelength accommodation of the lens. Meanwhile, total information represented by the cone mosaic remained relatively insensitive to L/M proportions. Thus, the observed cone array design along with a long-wavelength accommodated lens provides a selective advantage: it is maximally informative. PMID:20168996

  3. Cone Tracing for Furry Object Rendering.

    PubMed

    Qin, Hao; Chai, Menglei; Hou, Qiming; Ren, Zhong; Zhou, Kun

    2014-08-01

    We present a cone-based ray tracing algorithm for high-quality rendering of furry objects with reflection, refraction and defocus effects. By aggregating many sampling rays in a pixel as a single cone, we significantly reduce the high supersampling rate required by the thin geometry of fur fibers. To reduce the cost of intersecting fur fibers with cones, we construct a bounding volume hierarchy for the fiber geometry to find the fibers potentially intersecting with cones, and use a set of connected ribbons to approximate the projections of these fibers on the image plane. The computational cost of compositing and filtering transparent samples within each cone is effectively reduced by approximating away in-cone variations of shading, opacity and occlusion. The result is a highly efficient ray tracing algorithm for furry objects which is able to render images of quality comparable to those generated by alternative methods, while significantly reducing the rendering time. We demonstrate the rendering quality and performance of our algorithm using several examples and a user study. PMID:26357369

  4. Crowding in the S-cone pathway.

    PubMed

    Coates, Daniel R; Chung, Susana T L

    2016-05-01

    The spatial extent of interference from nearby object or contours (the critical spacing of "crowding") has been thoroughly characterized across the visual field, typically using high contrast achromatic stimuli. However, attempts to link this measure with known properties of physiological pathways have been inconclusive. The S-cone pathway, with its ease of psychophysical isolation and known anatomical characteristics, offers a unique tool to gain additional insights into crowding. In this study, we measured the spatial extent of crowding in the S-cone pathway at several retinal locations using a chromatic adaptation paradigm. S-cone crowding was evident and extensive, but its spatial extent changed less markedly as a function of retinal eccentricity than the extent found using traditional achromatic stimuli. However, the spatial extent agreed with that of low contrast achromatic stimuli matched for isolated resolvability. This suggests that common cortical mechanisms mediate the crowding effect in the S-cone and achromatic pathway, but contrast is an important factor. The low contrast of S-cone stimuli makes S-cone vision more acuity-limited than crowding-limited.

  5. Microspectrophotometric evidence for cone monochromacy in sharks.

    PubMed

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks-the rays and chimaeras-are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ(max) 484-518 nm) and cone (λ(max) 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology. PMID:21212930

  6. Microspectrophotometric evidence for cone monochromacy in sharks.

    PubMed

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks-the rays and chimaeras-are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ(max) 484-518 nm) and cone (λ(max) 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  7. Method and system for enhancing microbial motility

    SciTech Connect

    Hazen, T.C.; Lopez-De-Victoria, G.

    1992-12-31

    A method and system for enhancing the motility of microorganisms by placing an effective amount of chlorinated hydrocarbons, preferably chlorinated alkenes, and most preferably trichloroethylene in spaced relation to the microbes so that the surprisingly strong, monomodal, chemotactic response of the chlorinated hydrocarbon on subsurface microbes can draw the microbes away from or towards and into a substance, as desired. In remediation of groundwater pollution, for example, TCE can be injected into the plume to increase the population of microbes at the plume whereby the plume can be more quickly degraded. A TCE-degrading microbe, such as Welchia alkenophilia, can be used to degrade the TCE following the degradation of the original pollutant.

  8. Quantum Dot-Based Cell Motility Assay

    SciTech Connect

    Gu, Weiwei; Pellegrino, Teresa; Parak Wolfgang J; Boudreau,Rosanne; Le Gros, Mark A.; Gerion, Daniele; Alivisatos, A. Paul; Larabell, Carolyn A.

    2005-06-06

    Because of their favorable physical and photochemical properties, colloidal CdSe/ZnS-semiconductor nanocrystals (commonly known as quantum dots) have enormous potential for use in biological imaging. In this report, we present an assay that uses quantum dots as markers to quantify cell motility. Cells that are seeded onto a homogeneous layer of quantum dots engulf and absorb the nanocrystals and, as a consequence, leave behind a fluorescence-free trail. By subsequently determining the ratio of cell area to fluorescence-free track area, we show that it is possible to differentiate between invasive and noninvasive cancer cells. Because this assay uses simple fluorescence detection, requires no significant data processing, and can be used in live-cell studies, it has the potential to be a powerful new tool for discriminating between invasive and noninvasive cancer cell lines or for studying cell signaling events involved in migration.

  9. Mechanics model for actin-based motility.

    PubMed

    Lin, Yuan

    2009-02-01

    We present here a mechanics model for the force generation by actin polymerization. The possible adhesions between the actin filaments and the load surface, as well as the nucleation and capping of filament tips, are included in this model on top of the well-known elastic Brownian ratchet formulation. A closed form solution is provided from which the force-velocity relationship, summarizing the mechanics of polymerization, can be drawn. Model predictions on the velocity of moving beads driven by actin polymerization are consistent with experiment observations. This model also seems capable of explaining the enhanced actin-based motility of Listeria monocytogenes and beads by the presence of Vasodilator-stimulated phosphoprotein, as observed in recent experiments.

  10. Mechanics model for actin-based motility

    NASA Astrophysics Data System (ADS)

    Lin, Yuan

    2009-02-01

    We present here a mechanics model for the force generation by actin polymerization. The possible adhesions between the actin filaments and the load surface, as well as the nucleation and capping of filament tips, are included in this model on top of the well-known elastic Brownian ratchet formulation. A closed form solution is provided from which the force-velocity relationship, summarizing the mechanics of polymerization, can be drawn. Model predictions on the velocity of moving beads driven by actin polymerization are consistent with experiment observations. This model also seems capable of explaining the enhanced actin-based motility of Listeria monocytogenes and beads by the presence of Vasodilator-stimulated phosphoprotein, as observed in recent experiments.

  11. Spontaneous embryonic motility: an enduring legacy.

    PubMed

    Bekoff, A

    2001-04-01

    This chapter addresses the influential contributions Viktor Hamburger has made to our understanding of embryonic motor behavior. With his classic review, published in 1963, Viktor Hamburger opened up the field of embryonic motor behavior, which had lain almost completely dormant for many years. He focused his observations and experimental studies on the spontaneously generated embryonic movements rather than on reflex responses. As a result, he and his colleagues firmly established the central generation of embryonic motility as a basic component of embryonic behavior in chicks. These studies were also extended to rat fetuses, showing that similar principles apply to mammalian fetuses. All of us who have followed after him owe Viktor Hamburger an enormous debt of gratitude for his pioneering work. PMID:11255029

  12. Photonic Landau levels on cones

    NASA Astrophysics Data System (ADS)

    Schine, Nathan; Ryou, Albert; Gromov, Andrey; Sommer, Ariel; Simon, Jonathan

    2016-05-01

    We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Using a digital micromirror device to control both amplitude and phase, we inject arbitrary optical modes into our resonator. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We show that there is a conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids.

  13. Photonic Landau levels on cones

    NASA Astrophysics Data System (ADS)

    Schine, Nathan; Ryou, Albert; Gromov, Andrey; Sommer, Ariel; Simon, Jonathan

    2016-05-01

    Creating photonic materials with nontrivial topological characteristics has seen burgeoning interest in recent years; however, a major route to topology, a magnetic field for continuum photons, has remained elusive. We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We will discuss the conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids.

  14. Thyroxin Is Useful to Improve Sperm Motility

    PubMed Central

    Mendeluk, Gabriela Ruth; Rosales, Mónica

    2016-01-01

    Background The aim of this study was to evaluate the non-genomic action of thyroxin on sperm kinetic and its probable use to improve sperm recovery after applying an en- richment method like “swim-up” in comparison with the available one, pentoxifylline. Materials and Methods This is an experimental study. A total of 50 patients were re- cruited, followed by infertility consultation. Conventional sperm assays were performed according to World Health Organization criteria-2010 (WHO-2010). A Computer Aided Semen Analysis System was employed to assess kinetic parameters and concentrations. Number of the motile sperm recovered after preparation technique was calculated. Results Addition of T4 (0.002 µg/ml) to semen samples increased hypermotility at 20 minutes (control: 14.18 ± 5.1% vs. 17.66 ± 8.88%, P<0.03, data expressed as mean ± SD) and remained unchanged after 40 minutes. Significant differences were found in the motile sperm recovered after swim-up (control: 8.93×106 ± 9.52× 06vs. 17.20×106 ± 21.16×106, P<0.03), achieving all of the tested samples a desirable threshold value for artificial insemination outcome, while adding pentoxifylline increased the number of recovered sperm after swim-up in 60% of the studied cases. No synergism between two treatments could be determined. Conclusion We propose a new physiological tool to artificially improve insemination. The discussion opens windows to investigate unknown pathways involved in sperm ca- pacitation and gives innovative arguments to better understand infertility mechanisms. PMID:27441054

  15. Gliding Motility Revisited: How Do the Myxobacteria Move without Flagella?

    PubMed Central

    Mauriello, Emilia M. F.; Mignot, Tâm; Yang, Zhaomin; Zusman, David R.

    2010-01-01

    Summary: In bacteria, motility is important for a wide variety of biological functions such as virulence, fruiting body formation, and biofilm formation. While most bacteria move by using specialized appendages, usually external or periplasmic flagella, some bacteria use other mechanisms for their movements that are less well characterized. These mechanisms do not always exhibit obvious motility structures. Myxococcus xanthus is a motile bacterium that does not produce flagella but glides slowly over solid surfaces. How M. xanthus moves has remained a puzzle that has challenged microbiologists for over 50 years. Fortunately, recent advances in the analysis of motility mutants, bioinformatics, and protein localization have revealed likely mechanisms for the two M. xanthus motility systems. These results are summarized in this review. PMID:20508248

  16. Twitching motility and possession of polar fimbriae in spreading Streptococcus sanguis isolates from the human throat.

    PubMed

    Henriksen, S D; Henrichsen, J

    1975-04-01

    A collection of 19 strains of alpha haemolytic streptococci, isolated from throat swabs and characterized by production of spreading zones around colonies on blood agar, was found to constitute a very homogeneous group with morphological, physiological and biochemical characters corresponding to those of streptococci of ser-group H, or Streptococcus sanguis, and they all appeared to possess the group H antigen. They all had a common agglutinogen and, in addition, heterogeneous agglutinogens. The spreading growth, which appears to be a common property of S. sanguis, was due to twitching motility, and the spreading cultures possessed polar fimbriae. tneither twitching motility nor the possession of polar fimbriae have been observed in gram-positive bacteria before. PMID:1171576

  17. Use of Two Selective Media and a Broth Motility Test Can Aid in Identification or Exclusion of Bacillus anthracis

    PubMed Central

    Luna, Vicki A.; Peak, K. Kealy; Veguilla, William O.; Reeves, Frank; Heberlein-Larson, Lea; Cannons, Andrew C.; Amuso, Phil; Cattani, Jacqueline

    2005-01-01

    During the anthrax attack of 2001, the Florida Department of Health (FDOH) Bureau of Laboratories in Tampa received hundreds of isolates suspected of being Bacillus anthracis. None were confirmed to be B. anthracis since most isolates were motile and not even in the Bacillus cereus group. Although the sentinel laboratories now send fewer isolates to FDOH laboratories, should another attack occur the number of isolates submitted would likely increase dramatically, and this upsurge would seriously challenge personnel who are expected to be busy examining an increased number of environmental samples. We examined two selective and differential growth media and alternative motility methods that could be used to streamline the processing of suspicious isolates. Of 60 isolates previously sent to the FDOH laboratory, 56 were endospore-forming gram-positive rods and only 7 grew on mannitol-egg yolk-polymyxin B agar and/or the Anthracis chromogenic agar. Microscopic observation of early-log-phase growth (2 to 3 h) in a shaking broth was the best method to detect motility in 40 isolates that appeared nonmotile in the motility media investigated. One of these growth media and microscopic examination of shaken broth cultures can be used to show that an isolate is not B. anthracis before expensive molecular and antibody-based tests are performed. By doing so, costs could be reduced and analysis time shortened. PMID:16145074

  18. Growth

    NASA Astrophysics Data System (ADS)

    Waag, Andreas

    This chapter is devoted to the growth of ZnO. It starts with various techniques to grow bulk samples and presents in some detail the growth of epitaxial layers by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and pulsed laser deposition (PLD). The last section is devoted to the growth of nanorods. Some properties of the resulting samples are also presented. If a comparison between GaN and ZnO is made, very often the huge variety of different growth techniques available to fabricate ZnO is said to be an advantage of this material system. Indeed, growth techniques range from low cost wet chemical growth at almost room temperature to high quality MOCVD growth at temperatures above 1, 000∘C. In most cases, there is a very strong tendency of c-axis oriented growth, with a much higher growth rate in c-direction as compared to other crystal directions. This often leads to columnar structures, even at relatively low temperatures. However, it is, in general, not straight forward to fabricate smooth ZnO thin films with flat surfaces. Another advantage of a potential ZnO technology is said to be the possibility to grow thin films homoepitaxially on ZnO substrates. ZnO substrates are mostly fabricated by vapor phase transport (VPT) or hydrothermal growth. These techniques are enabling high volume manufacturing at reasonable cost, at least in principle. The availability of homoepitaxial substrates should be beneficial to the development of ZnO technology and devices and is in contrast to the situation of GaN. However, even though a number of companies are developing ZnO substrates, only recently good quality substrates have been demonstrated. However, these substrates are not yet widely available. Still, the situation concerning ZnO substrates seems to be far from low-cost, high-volume production. The fabrication of dense, single crystal thin films is, in general, surprisingly difficult, even when ZnO is grown on a ZnO substrate. However

  19. 3D modelling of the Tejeda Caldera cone-sheet swarm, Gran Canaria, Canary Islands, Spain

    NASA Astrophysics Data System (ADS)

    Samrock, Lisa K.; Jensen, Max J.; Burchardt, Steffi; Troll, Valentin R.; Mattsson, Tobias; Geiger, Harri

    2015-04-01

    . 2011, and references therein), and we discuss the implications of this architecture for the feeding system of the Tejeda volcano and the associated temporal variations of cone-sheet emplacement. References: Burchardt, S., Tanner, D.C., Troll, V.R., Krumbholz, M., Gustafsson, L.E. (2011) Three-dimensional geometry of concentric intrusive sheet swarms in the Geitafell and the Dyrfjöll volcanoes, eastern Iceland. Geochemistry, Geophysics, Geosystems 12(7): Q0AB09. Burchardt, S., Troll, V.R., Mathieu, L., Emeleus, H.C., Donaldson, C.H. (2013) Ardnamruchan 3D cone-sheet architecture explained by a single elongate magma chamber. Scientific Reports 3:2891. Schirnick, C. (1996) Formation of an intracaldera cone sheet dike swarm (Tejeda Caldera, Gran Canaria) (Dissertation). Christian-Albrechts-Universität, Kiel, Germany. Schirnick, C., van den Bogaard, P., Schmincke, H.-U. (1999) Cone-sheet formation and intrusive growth of an oceanic island - The Miocene Tejeda complex on Gran Canaria (Canary Islands). Geology, 27: 207-210.

  20. Submicrometer Hollow Bioglass Cones Deposited by Radio Frequency Magnetron Sputtering: Formation Mechanism, Properties, and Prospective Biomedical Applications.

    PubMed

    Popa, A C; Stan, G E; Besleaga, C; Ion, L; Maraloiu, V A; Tulyaganov, D U; Ferreira, J M F

    2016-02-01

    This work reports on the unprecedented magnetron sputtering deposition of submicrometric hollow cones of bioactive glass at low temperature in the absence of any template or catalyst. The influence of sputtering conditions on the formation and development of bioglass cones was studied. It was shown that larger populations of well-developed cones could be achieved by increasing the argon sputtering pressure. A mechanism describing the growth of bioglass hollow cones is presented, offering the links for process control and reproducibility of the cone features. The composition, structure, and morphology of the as-synthesized hollow cones were investigated by energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), grazing incidence geometry X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM)-selected area electron diffraction (SAED). The in vitro biological performance, assessed by degradation tests (ISO 10993-14) and cytocompatibility assays (ISO 10993-5) in endothelial cell cultures, was excellent. This allied with resorbability and the unique morphological features make the submicrometer hollow cones interesting candidate material devices for focal transitory permeabilization of the blood-brain barrier in the treatment of carcinoma and neurodegenerative disorders.

  1. Shape of scoria cones on Mars: Insights from numerical modeling of ballistic pathways

    NASA Astrophysics Data System (ADS)

    Brož, Petr; Čadek, Ondřej; Hauber, Ernst; Rossi, Angelo Pio

    2014-11-01

    Morphological observations of scoria cones on Mars show that their cross-sectional shapes are different from those on Earth. Due to lower gravity and atmospheric pressure on Mars, particles are spread over a larger area than on Earth. Hence, erupted volumes are typically not large enough for the flank slopes to attain the angle of repose, in contrast to Earth where this is common. The distribution of ejected material forming scoria cones on Mars, therefore, is ruled mainly by ballistic distribution and not by redistribution of flank material by avalanching after the static angle of repose is reached. As a consequence, the flank slopes of the Martian scoria cones do not reach the critical angle of repose in spite of a large volume of ejected material. Therefore, the topography of scoria cones on Mars is governed mainly by ballistic distribution of ejected particles and is not influenced by redistribution of flank material by avalanching. The growth of a scoria cone can be studied numerically by tracking the ballistic trajectories and tracing the cumulative deposition of repeatedly ejected particles. We apply this approach to a specific volcanic field, Ulysses Colles on Mars, and compare our numerical results with observations. The scoria cones in this region are not significantly affected by erosion and their morphological shape still preserves a record of physical conditions at the time of eruption. We demonstrate that the topography of these scoria cones can be rather well (with accuracy of ∼10 m) reproduced provided that the ejection velocities are a factor of ∼2 larger and the ejected particles are about ten times finer than typical on Earth, corresponding to a mean particle velocity of ∼92 m/s and a real particle size of about 4 mm. This finding is in agreement with previous theoretical works that argued for larger magma fragmentation and higher ejection velocities on Mars than on Earth due to lower gravity and different environmental conditions.

  2. Light responses of primate and other mammalian cones

    PubMed Central

    Cao, Li-Hui; Luo, Dong-Gen; Yau, King-Wai

    2014-01-01

    Retinal cones are photoreceptors for daylight vision. For lower vertebrates, cones are known to give monophasic, hyperpolarizing responses to light flashes. For primate cones, however, they have been reported to give strongly biphasic flash responses, with an initial hyperpolarization followed by a depolarization beyond the dark level, now a textbook dogma. We have reexamined this primate-cone observation and, surprisingly, found predominantly monophasic cone responses. Correspondingly, we found that primate cones began to adapt to steady light at much lower intensities than previously reported, explainable by a larger steady response to background light for a monophasic than for a biphasic response. Similarly, we have found a monophasic cone response for several other mammalian species. Thus, a monophasic flash response may in fact be the norm for primate and other mammalian cones as for lower-vertebrate cones. This revised information is important for ultimately understanding human retinal signal processing and correlating with psychophysical data. PMID:24550304

  3. Origin and Impact of Phototransduction Noise in Primate Cone Photoreceptors

    PubMed Central

    Angueyra, Juan Manuel; Rieke, Fred

    2013-01-01

    Noise in the responses of cone photoreceptors sets a fundamental limit to visual sensitivity, yet the origin of noise in mammalian cones and its relation to behavioral sensitivity are poorly understood. Our work here on primate cones improves understanding of these issues in three ways. First, we find that cone noise is not dominated by spontaneous photopigment activation or by quantal fluctuations in photon absorption but instead by other sources, namely channel noise and fluctuations in cGMP. Second, we find that adaptation in cones, unlike that in rods, affects signals and noise differently. This difference helps explain why thresholds for rod- and cone-mediated signals have different dependencies on background light level. Third, past estimates of noise in mammalian cones are too high to explain behavioral sensitivity. Our measurements indicate a lower level of cone noise, and thus help reconcile physiological and behavioral estimates of cone noise and sensitivity. PMID:24097042

  4. Light responses of primate and other mammalian cones.

    PubMed

    Cao, Li-Hui; Luo, Dong-Gen; Yau, King-Wai

    2014-02-18

    Retinal cones are photoreceptors for daylight vision. For lower vertebrates, cones are known to give monophasic, hyperpolarizing responses to light flashes. For primate cones, however, they have been reported to give strongly biphasic flash responses, with an initial hyperpolarization followed by a depolarization beyond the dark level, now a textbook dogma. We have reexamined this primate-cone observation and, surprisingly, found predominantly monophasic cone responses. Correspondingly, we found that primate cones began to adapt to steady light at much lower intensities than previously reported, explainable by a larger steady response to background light for a monophasic than for a biphasic response. Similarly, we have found a monophasic cone response for several other mammalian species. Thus, a monophasic flash response may in fact be the norm for primate and other mammalian cones as for lower-vertebrate cones. This revised information is important for ultimately understanding human retinal signal processing and correlating with psychophysical data. PMID:24550304

  5. The motility-proliferation-metabolism interplay during metastatic invasion

    PubMed Central

    Hecht, Inbal; Natan, Sari; Zaritsky, Assaf; Levine, Herbert; Tsarfaty, Ilan; Ben-Jacob, Eshel

    2015-01-01

    Metastasis is the major cause for cancer patients’ death, and despite all the recent advances in cancer research it is still mostly incurable. Understanding the mechanisms that are involved in the migration of the cells in a complex environment is a key step towards successful anti-metastatic treatment. Using experimental data-based modeling, we focus on the fundamentals of metastatic invasion: motility, invasion, proliferation and metabolism, and study how they may be combined to maximize the cancer’s ability to metastasize. The modeled cells’ performance is measured by the number of cells that succeed in migration in a maze, which mimics the extracellular environment. We show that co-existence of different cell clones in the tumor, as often found in experiments, optimizes the invasive ability in a frequently-changing environment. We study the role of metabolism and stimulation by growth factors, and show that metabolism plays a crucial role in the metastatic process and should therefore be targeted for successful treatment. PMID:26337223

  6. The motility-proliferation-metabolism interplay during metastatic invasion.

    PubMed

    Hecht, Inbal; Natan, Sari; Zaritsky, Assaf; Levine, Herbert; Tsarfaty, Ilan; Ben-Jacob, Eshel

    2015-01-01

    Metastasis is the major cause for cancer patients' death, and despite all the recent advances in cancer research it is still mostly incurable. Understanding the mechanisms that are involved in the migration of the cells in a complex environment is a key step towards successful anti-metastatic treatment. Using experimental data-based modeling, we focus on the fundamentals of metastatic invasion: motility, invasion, proliferation and metabolism, and study how they may be combined to maximize the cancer's ability to metastasize. The modeled cells' performance is measured by the number of cells that succeed in migration in a maze, which mimics the extracellular environment. We show that co-existence of different cell clones in the tumor, as often found in experiments, optimizes the invasive ability in a frequently-changing environment. We study the role of metabolism and stimulation by growth factors, and show that metabolism plays a crucial role in the metastatic process and should therefore be targeted for successful treatment. PMID:26337223

  7. Quorum sensing positively regulates flagellar motility in pathogenic Vibrio harveyi.

    PubMed

    Yang, Qian; Defoirdt, Tom

    2015-04-01

    Vibrios belonging to the Harveyi clade are among the major pathogens of aquatic organisms. Quorum sensing (QS) is essential for virulence of V. harveyi towards different hosts. However, most virulence factors reported to be controlled by QS to date are negatively regulated by QS, therefore suggesting that their impact on virulence is limited. In this study, we report that QS positively regulates flagellar motility. We found that autoinducer synthase mutants showed significantly lower swimming motility than the wild type, and the swimming motility could be restored by adding synthetic signal molecules. Further, motility of a luxO mutant with inactive QS (LuxO D47E) was significantly lower than that of the wild type and of a luxO mutant with constitutively maximal QS activity (LuxO D47A). Furthermore, we found that the expression of flagellar genes (both early, middle and late genes) was significantly lower in the luxO mutant with inactive QS when compared with wild type and the luxO mutant with maximal QS activity. Motility assays and gene expression also revealed the involvement of the quorum-sensing master regulator LuxR in the QS regulation of motility. Finally, the motility inhibitor phenamil significantly decreased the virulence of V. harveyi towards gnotobiotic brine shrimp larvae. PMID:24528485

  8. Dynamic self-assembly of motile bacteria in liquid crystals

    PubMed Central

    Mushenheim, Peter C.; Trivedi, Rishi R.; Tuson, Hannah H.

    2014-01-01

    This paper reports an investigation of dynamical behaviors of motile rod-shaped bacteria within anisotropic viscoelastic environments defined by lyotropic liquid crystals (LCs). In contrast to passive microparticles (including non-motile bacteria) that associate irreversibly in LCs via elasticity-mediated forces, we report that motile Proteus mirabilis bacteria form dynamic and reversible multi-cellular assemblies when dispersed in a lyotropic LC. By measuring the velocity of the bacteria through the LC (8.8 +/− 0.2 μm/s) and by characterizing the ordering of the LC about the rod-shaped bacteria (tangential anchoring), we conclude that the reversibility of the inter-bacterial interaction emerges from the interplay of forces generated by the flagella of the bacteria and the elasticity of the LC, both of which are comparable in magnitude (tens of pN) for motile Proteus mirabilis cells. We also measured the dissociation process, which occurs in a direction determined by the LC, to bias the size distribution of multi-cellular bacterial complexes in a population of motile Proteus mirabilis relative to a population of non-motile cells. Overall, these observations and others reported in this paper provide insight into the fundamental dynamical behaviors of bacteria in complex anisotropic environments and suggest that motile bacteria in LCs are an exciting model system for exploration of principles for the design of active materials. PMID:24652584

  9. Ion channels and calcium signaling in motile cilia

    PubMed Central

    Doerner, Julia F; Delling, Markus; Clapham, David E

    2015-01-01

    The beating of motile cilia generates fluid flow over epithelia in brain ventricles, airways, and Fallopian tubes. Here, we patch clamp single motile cilia of mammalian ependymal cells and examine their potential function as a calcium signaling compartment. Resting motile cilia calcium concentration ([Ca2+] ~170 nM) is only slightly elevated over cytoplasmic [Ca2+] (~100 nM) at steady state. Ca2+ changes that arise in the cytoplasm rapidly equilibrate in motile cilia. We measured CaV1 voltage-gated calcium channels in ependymal cells, but these channels are not specifically enriched in motile cilia. Membrane depolarization increases ciliary [Ca2+], but only marginally alters cilia beating and cilia-driven fluid velocity within short (~1 min) time frames. We conclude that beating of ependymal motile cilia is not tightly regulated by voltage-gated calcium channels, unlike that of well-studied motile cilia and flagella in protists, such as Paramecia and Chlamydomonas. DOI: http://dx.doi.org/10.7554/eLife.11066.001 PMID:26650848

  10. Regulation of flagellar, motility and chemotaxis genes in Rhizobium leguminosarum by the VisN/R-Rem cascade.

    PubMed

    Tambalo, Dinah D; Del Bel, Kate L; Bustard, Denise E; Greenwood, Paige R; Steedman, Audrey E; Hynes, Michael F

    2010-06-01

    In this paper, we describe the regulatory roles of VisN, VisR and Rem in the expression of flagellar, motility and chemotaxis genes in Rhizobium leguminosarum biovar viciae strains VF39SM and 3841. Individual mutations in the genes encoding these proteins resulted in a loss of motility and an absence of flagella, indicating that these regulatory genes are essential for flagellar synthesis and function. Transcriptional experiments involving gusA-gene fusions in wild-type and mutant backgrounds were performed to identify the genes under VisN/R and Rem regulation. Results showed that the chemotaxis and motility genes of R. leguminosarum could be separated into two groups: one group under VisN/R-Rem regulation and another group that is independent of this regulation. VisN and VisR regulate the expression of rem, while Rem positively regulates the expression of flaA, flaB, flaC, flaD, motA, motB, che1 and mcpD. All of these genes except mcpD are located within the main motility and chemotaxis gene cluster of R. leguminosarum. Other chemotaxis and motility genes, which are found outside of the main motility gene cluster (che2 operon, flaH for VF39SM, and flaG) or are plasmid-borne (flaE and mcpC), are not part of the VisN/R-Rem regulatory cascade. In addition, all genes exhibited the same regulation pattern in 3841 and in VF39SM, except flaE and flaH. flaE is not regulated by VisN/R-Rem in 3841 but it is repressed by Rem in VF39SM. flaH is under VisN/R-Rem regulation in 3841, but not in VF39SM. A kinetics experiment demonstrated that a subset of the flagellar genes is continuously expressed in all growth phases, indicating the importance of continuous motility for R. leguminosarum under free-living conditions. On the other hand, motility is repressed under symbiotic conditions. Nodulation experiments showed that the transcriptional activators VisN and Rem are dramatically downregulated in the nodules, suggesting that the symbiotic downregulation of motility-related genes

  11. Regulation of flagellar, motility and chemotaxis genes in Rhizobium leguminosarum by the VisN/R-Rem cascade.

    PubMed

    Tambalo, Dinah D; Del Bel, Kate L; Bustard, Denise E; Greenwood, Paige R; Steedman, Audrey E; Hynes, Michael F

    2010-06-01

    In this paper, we describe the regulatory roles of VisN, VisR and Rem in the expression of flagellar, motility and chemotaxis genes in Rhizobium leguminosarum biovar viciae strains VF39SM and 3841. Individual mutations in the genes encoding these proteins resulted in a loss of motility and an absence of flagella, indicating that these regulatory genes are essential for flagellar synthesis and function. Transcriptional experiments involving gusA-gene fusions in wild-type and mutant backgrounds were performed to identify the genes under VisN/R and Rem regulation. Results showed that the chemotaxis and motility genes of R. leguminosarum could be separated into two groups: one group under VisN/R-Rem regulation and another group that is independent of this regulation. VisN and VisR regulate the expression of rem, while Rem positively regulates the expression of flaA, flaB, flaC, flaD, motA, motB, che1 and mcpD. All of these genes except mcpD are located within the main motility and chemotaxis gene cluster of R. leguminosarum. Other chemotaxis and motility genes, which are found outside of the main motility gene cluster (che2 operon, flaH for VF39SM, and flaG) or are plasmid-borne (flaE and mcpC), are not part of the VisN/R-Rem regulatory cascade. In addition, all genes exhibited the same regulation pattern in 3841 and in VF39SM, except flaE and flaH. flaE is not regulated by VisN/R-Rem in 3841 but it is repressed by Rem in VF39SM. flaH is under VisN/R-Rem regulation in 3841, but not in VF39SM. A kinetics experiment demonstrated that a subset of the flagellar genes is continuously expressed in all growth phases, indicating the importance of continuous motility for R. leguminosarum under free-living conditions. On the other hand, motility is repressed under symbiotic conditions. Nodulation experiments showed that the transcriptional activators VisN and Rem are dramatically downregulated in the nodules, suggesting that the symbiotic downregulation of motility-related genes

  12. Ecophysiological variables influencing Aleppo pine seed and cone production: a review.

    PubMed

    Ayari, Abdelaziz; Khouja, Mohamed Larbi

    2014-04-01

    The most interesting factors associated with seed and cone production of Aleppo pine were largely reviewed to identify broad patterns and potential effectiveness of reforestation efforts and planning. Aleppo pine cone production and seed yields are relatively variable, with differences between spatial and temporal influences. These differences are considered, mainly between (i) year, (ii) stand characteristics and (iii) individual tree measurements. Annual variability among populations was recorded for cone production per tree, based on influencing factors such as genetic characteristics, wetness, nutrient availability, insect pests and disease. In addition, some factors may affect Aleppo pine tree growth directly but may be affecting seed and cone production indirectly. Therefore, reduced stand density results in less competition among Aleppo pine trees and accompanying understory flora, which subsequently increases the stem diameter and other tree dimensions, including seed production. This review suggests that reforestation planning, particularly thinning, will result in improved tree morphology that will increase Aleppo pine seed and cone crops. Wildfire intensity and stand conditions such as light and soil nutrient status are also examined.

  13. Multiple dendrochronological responses to the eruption of Cinder Cone, Lassen Volcanic National Park, California

    USGS Publications Warehouse

    Sheppard, P.R.; Ort, M.H.; Anderson, K.C.; Clynne, M.A.; May, E.M.

    2009-01-01

    Two dendrochronological properties – ring width and ring chemistry – were investigated in trees near Cinder Cone in Lassen Volcanic National Park, northeastern California, for the purpose of re-evaluating the date of its eruption. Cinder Cone is thought to have erupted in AD 1666 based on ring-width evidence, but interpreting ring-width changes alone is not straightforward because many forest disturbances can cause changes in ring width. Old Jeffrey pines growing in Cinder Cone tephra and elsewhere for control comparison were sampled. Trees growing in tephra show synchronous ring-width changes at AD 1666, but this ring-width signal could be considered ambiguous for dating the eruption because changes in ring width can be caused by other events. Trees growing in tephra also show changes in ring phosphorus, sulfur, and sodium during the late 1660s, but inter-tree variability in dendrochemical signals makes dating the eruption from ring chemistry alone difficult. The combination of dendrochemistry and ring-width signals improves confidence in dating the eruption of Cinder Cone over the analysis of just one ring-growth property. These results are similar to another case study using dendrochronology of ring width and ring chemistry at Parícutin, Michoacán, Mexico, a cinder cone that erupted beginning in 1943. In both cases, combining analysis with ring width and ring chemistry improved confidence in the dendro-dating of the eruptions.

  14. Flagella-independent surface motility in Salmonella enterica serovar Typhimurium.

    PubMed

    Park, Sun-Yang; Pontes, Mauricio H; Groisman, Eduardo A

    2015-02-10

    Flagella are multiprotein complexes necessary for swimming and swarming motility. In Salmonella enterica serovar Typhimurium, flagella-mediated motility is repressed by the PhoP/PhoQ regulatory system. We now report that Salmonella can move on 0.3% agarose media in a flagella-independent manner when experiencing the PhoP/PhoQ-inducing signal low Mg(2+). This motility requires the PhoP-activated mgtA, mgtC, and pagM genes, which specify a Mg(2+) transporter, an inhibitor of Salmonella's own F1Fo ATPase, and a small protein of unknown function, respectively. The MgtA and MgtC proteins are necessary for pagM expression because pagM mRNA levels were lower in mgtA and mgtC mutants than in wild-type Salmonella, and also because pagM expression from a heterologous promoter rescued motility in mgtA and mgtC mutants. PagM promotes group motility by a surface protein(s), as a pagM-expressing strain conferred motility upon a pagM null mutant, and proteinase K treatment eliminated motility. The pagM gene is rarely found outside subspecies I of S. enterica and often present in nonfunctional allelic forms in organisms lacking the identified motility. Deletion of the pagM gene reduced bacterial replication on 0.3% agarose low Mg(2+) media but not in low Mg(2+) liquid media. Our findings define a form of motility that allows Salmonella to scavenge nutrients and to escape toxic compounds in low Mg(2+) semisolid environments. PMID:25624475

  15. Swimming with protists: perception, motility and flagellum assembly.

    PubMed

    Ginger, Michael L; Portman, Neil; McKean, Paul G

    2008-11-01

    In unicellular and multicellular eukaryotes, fast cell motility and rapid movement of material over cell surfaces are often mediated by ciliary or flagellar beating. The conserved defining structure in most motile cilia and flagella is the '9+2' microtubule axoneme. Our general understanding of flagellum assembly and the regulation of flagellar motility has been led by results from seminal studies of flagellate protozoa and algae. Here we review recent work relating to various aspects of protist physiology and cell biology. In particular, we discuss energy metabolism in eukaryotic flagella, modifications to the canonical assembly pathway and flagellum function in parasite virulence. PMID:18923411

  16. Swimming with protists: perception, motility and flagellum assembly.

    PubMed

    Ginger, Michael L; Portman, Neil; McKean, Paul G

    2008-11-01

    In unicellular and multicellular eukaryotes, fast cell motility and rapid movement of material over cell surfaces are often mediated by ciliary or flagellar beating. The conserved defining structure in most motile cilia and flagella is the '9+2' microtubule axoneme. Our general understanding of flagellum assembly and the regulation of flagellar motility has been led by results from seminal studies of flagellate protozoa and algae. Here we review recent work relating to various aspects of protist physiology and cell biology. In particular, we discuss energy metabolism in eukaryotic flagella, modifications to the canonical assembly pathway and flagellum function in parasite virulence.

  17. Effect of anionic polymeric hydrogels on spermatozoa motility.

    PubMed

    Singh, H; Jabbal, M S; Ray, A R; Vasudevan, P

    1984-09-01

    The effects of a few synthetic polymers on the motility of human spermatozoa in vitro have been studied. An alternate copolymer of styrene and maleic anhydride, poly(S-MA), poly (styrene-maleic acid), poly(S-MC), poly(hydroxy-ethyl methacrylate-methacrylic acid) copolymer, poly(HEMA-MAC), poly(HEMA) homopolymer and poly(MAC) homopolymer were chosen for this purpose. It was found that all the carboxylic acid containing polymers are strong inhibitors of the motility of spermatozoa. Poly(HEMA) did not have any inhibitory effect on the motility of spermatozoa.

  18. Shear alters motility of Escherichia coli

    NASA Astrophysics Data System (ADS)

    Molaei, Mehdi; Jalali, Maryam; Sheng, Jian

    2013-11-01

    Understanding of locomotion of microorganisms in shear flows drew a wide range of interests in microbial related topics such as biological process including pathogenic infection and biophysical interactions like biofilm formation on engineering surfaces. We employed microfluidics and digital holography microscopy to study motility of E. coli in shear flows. We controlled the shear flow in three different shear rates: 0.28 s-1, 2.8 s-1, and 28 s-1 in a straight channel with the depth of 200 μm. Magnified holograms, recorded at 15 fps with a CCD camera over more than 20 minutes, are analyzed to obtain 3D swimming trajectories and subsequently used to extract shear responses of E.coli. Thousands of 3-D bacterial trajectories are tracked. The change of bacteria swimming characteristics including swimming velocity, reorientation, and dispersion coefficient are computed directly for individual trajectory and ensemble averaged over thousands of realizations. The results show that shear suppresses the bacterial dispersions in bulk but promote dispersions near the surface contrary to those in quiescent flow condition. Ongoing analyses are focusing to quantify effect of shear rates on tumbling frequency and reorientation of cell body, and its implication in locating the hydrodynamic mechanisms for shear enhanced angular scattering. NIH, NSF, GoMRI.

  19. [The flagellum: from cell motility to morphogenesis].

    PubMed

    Kohl, Linda; Robinson, Derrick; Bastin, Philippe

    2003-01-01

    Flagella and cilia are elaborate cytoskeletal structures conserved from protists to mammals, where they fulfil functions related to motility or sensitivity. We demonstrate a novel role for the flagellum in the control of cell morphogenesis and division of Trypanosoma brucei. To investigate flagellum functions, its formation was perturbed by inducible RNA interference silencing of components required for intraflagellar transport (IFT), a dynamic process necessary for flagellum assembly. First, we show that down-regulation of IFT leads to assembly of a shorter flagellum. Strikingly, cells with a shorter flagellum are smaller, with a direct correlation between flagellum length and cell size. Detailed morphogenetic analysis reveals that the tip of the new flagellum defines the point where cytokinesis is initiated. Furthermore, when new flagellum formation is completely blocked, non-flagellated cells are very short, lose their normal shape and polarity and fail to undergo cytokinesis. We show that flagellum elongation controls formation of cytoskeletal structures present in the cell body that act as molecular organisers of the cell.

  20. Colloidal motility and patterning by physical chemotaxis

    NASA Astrophysics Data System (ADS)

    Palacci, Jeremie; Abecassis, Benjamin; Cottin-Bizonne, Cecile; Ybert, Christophe; Bocquet, Lyderic

    2009-11-01

    We developped a microfluidic setup to show the motility of colloids or biomolecules under a controlled salt gradient thanks to the diffusiophoresis phenomenon [1,2]. We can therefore mimic chemotaxis on simple physical basis with thrilling analogies with the biological chemotaxis of E. Coli bacteria: salt dependance of the velocity [3] and log-sensing behavior [4]. In addition with a temporally tunable gradient we show we can generate an effective osmotic potential to trap colloids or DNA. These experimental observations are supported by numerical simulations and an asymptotic ratchet model. Finally, we use these traps to generate various patterns and because concentration gradients are ubiquitous in nature, we question for the role of such a mecanism in morphogenesis [5] or positioning perspectives in cells [6]. [4pt] [1] B. Abecassis, C. Cottin-Bizonne, C. Ybert, A. Ajdari, and L. Bocquet, Nat. Mat., 7(10):785--789, 2008. [2] Anderson, Ann. Rev. Fluid Mech, 21, 1989. [3] Y. L. Qi and J. Adler, PNAS, 86(21):8358--8362, 1989. [4] Y. V. Kalinin, L. L. Jiang, Y. H. Tu, and M. M. Wu, Biophys. J., 96(6):2439--2448, 2009. [4] J. B. Moseley, A. Mayeux, A. Paoletti, and P. Nurse, Nat., 459(7248):857--U8, 2009. [6] L. Wolpert, Dev., 107:3--12, 1989

  1. Comparative analysis of mammalian sperm motility.

    PubMed

    Phillips, D M

    1972-05-01

    Spermatozoa of several mammalian species were studied by means of high-speed cinematography and electron microscopy. Three types of motile patterns were observed in mouse spermatozoa. The first type involved an asymmetrical beat which seemed to propel the sperm in circular paths. The second type involved rotation of the sperm and appeared to allow them to maintain straight paths. In the third type of pattern, the sperm appeared to move by crawling on surfaces in a snakelike manner. Spermatozoa of rabbit and Chinese hamster also had an asymmetrical beat which sometimes caused them to swim in circles. In spite of the asymmetry of the beat, these spermatozoa were also able to swim in straight paths by rotating around a central axis as they swam. Spermatozoa of some species appeared very flexible; their flagella formed arcs with a very small radius of curvature as they beat. Spermatozoa of other species appeared very stiff, and their flagella formed arcs with a very large radius of curvature. The stiffness of the spermatozoan appeared to correlate positively with the cross-sectional area of the dense fibers. This suggests that the dense fibers may be stiff elastic elements. Opossum sperm become paired as they pass through the epididymis. Pairs of opossum spermatozoa beat in a coordinated, alternating manner.

  2. Inhibition of tumor cell proliferation and motility by fibroblasts is both contact and soluble factor dependent

    PubMed Central

    Alkasalias, Twana; Flaberg, Emilie; Kashuba, Vladimir; Alexeyenko, Andrey; Pavlova, Tatiana; Savchenko, Andrii; Szekely, Laszlo; Klein, George; Guven, Hayrettin

    2014-01-01

    Normal human and murine fibroblasts can inhibit proliferation of tumor cells when cocultured in vitro. The inhibitory capacity varies depending on the donor and the site of origin of the fibroblast. We showed previously that effective inhibition requires formation of a morphologically intact fibroblast monolayer before seeding of the tumor cells. Here we show that inhibition is extended to motility of tumor cells and we dissect the factors responsible for these inhibitory functions. We find that inhibition is due to two different sets of molecules: (i) the extracellular matrix (ECM) and other surface proteins of the fibroblasts, which are responsible for contact-dependent inhibition of tumor cell proliferation; and (ii) soluble factors secreted by fibroblasts when confronted with tumor cells (confronted conditioned media, CCM) contribute to inhibition of tumor cell proliferation and motility. However, conditioned media (CM) obtained from fibroblasts alone (nonconfronted conditioned media, NCM) did not inhibit tumor cell proliferation and motility. In addition, quantitative PCR (Q-PCR) data show up-regulation of proinflammatory genes. Moreover, comparison of CCM and NCM with an antibody array for 507 different soluble human proteins revealed differential expression of growth differentiation factor 15, dickkopf-related protein 1, endothelial-monocyte-activating polypeptide II, ectodysplasin A2, Galectin-3, chemokine (C-X-C motif) ligand 2, Nidogen1, urokinase, and matrix metalloproteinase 3. PMID:25404301

  3. Up-regulation of neogenin-1 increases cell proliferation and motility in gastric cancer

    PubMed Central

    Kim, Seok-Jun; Wang, Yuan-Guo; Lee, Hyun-Woo; Gu Kang, Hyeok; La, Sun-Hyuk; Ju Choi, Il; Irimura, Tatsuro; Ro, Jae Y.; Bresalier, Robert S.; Chun, Kyung-Hee

    2014-01-01

    Although elevated expression of neogenin-1 has been detected in human gastric cancer tissue, its role in gastric tumorigenesis remains unclear due to the lack of neogenin-1 studies in cancer. Therefore, we demonstrated here the function and regulatory mechanism of neogenin-1 in gastric cancer. Neogenin-1 ablation decreased proliferation and migration of gastric cancer cells, whereas its over-expression reversed these effects. Xenografted analyses using gastric cancer cells displayed statistically significant inhibition of tumor growth by neogenin-1 depletion. Interestingly, galectin-3 interacted with HSF-1 directly, which facilitated nuclear-localization and binding on neogenin-1 promoter to drive its transcription and gastric cancer cell motility. The galectin-3-increased gastric cancer cell motility was down-regulated by HSF-1 depletion. Moreover, the parallel expression patterns of galectin-3 and neogenin-1, as well as those of HSF-1 and neogenin-1, were detected in the malignant tissues of gastric cancer patients. Taken together, high-expression of neogenin-1 promotes gastric cancer proliferation and motility and its expression is regulated by HSF-1 and galectin-3 interaction. In addition, we propose further studies for neogenin-1 and its associated pathways to provide them as a proper target for gastric cancer therapy. PMID:24930499

  4. PTP1B inhibitor promotes endothelial cell motility by activating the DOCK180/Rac1 pathway

    PubMed Central

    Wang, Yuan; Yan, Feng; Ye, Qing; Wu, Xiao; Jiang, Fan

    2016-01-01

    Promoting endothelial cell (EC) migration is important not only for therapeutic angiogenesis, but also for accelerating re-endothelialization after vessel injury. Several recent studies have shown that inhibition of protein tyrosine phosphatase 1B (PTP1B) may promote EC migration and angiogenesis by enhancing the vascular endothelial growth factor receptor-2 (VEGFR2) signalling. In the present study, we demonstrated that PTP1B inhibitor could promote EC adhesion, spreading and migration, which were abolished by the inhibitor of Rac1 but not RhoA GTPase. PTP1B inhibitor significantly increased phosphorylation of p130Cas, and the interactions among p130Cas, Crk and DOCK180; whereas the phosphorylation levels of focal adhesion kinase, Src, paxillin, or Vav2 were unchanged. Gene silencing of DOCK180, but not Vav2, abrogated the effects of PTP1B inhibitor on EC motility. The effects of PTP1B inhibitor on EC motility and p130Cas/DOCK180 activation persisted in the presence of the VEGFR2 antagonist. In conclusion, we suggest that stimulation of the DOCK180 pathway represents an alternative mechanism of PTP1B inhibitor-stimulated EC motility, which does not require concomitant VEGFR2 activation as a prerequisite. Therefore, PTP1B inhibitor may be a useful therapeutic strategy for promoting EC migration in cardiovascular patients in which the VEGF/VEGFR functions are compromised. PMID:27052191

  5. On the transient dynamics of the wake and trajectory of free falling cones with various apex angles

    NASA Astrophysics Data System (ADS)

    Hamed, Ali M.; Jin, Yaqing; Chamorro, Leonardo P.

    2015-11-01

    The early free fall stages of cones with a density ratio 1.18 and apex angles of 30°, 45°, 60°, and 90° were studied using a wireless 3-axis gyroscope and accelerometer to describe the cone 3D motions, while particle image velocimetry was used to capture the induced flow in the near wake. The Reynolds number based on the cones diameter and the velocity at which the cone reaches the first local velocity maximum is found to consistently set the limit between two distinctive states. Relatively rapid growth in the cone nutation and departure from the vertical axis is observed after this Re is reached. Sequences of vertical velocity, swirling strength, LES-decomposed velocity, and pressure fields show the formation and growth of a large and initially symmetric recirculation bubble at the cone base. Those also highlight the presence of a symmetric 3D vortex rollup dominating the near wake in the early stages of the fall. A shear layer develops at the edge of the wake and manifests in the periodic shedding of Kelvin-Helmholtz vortices that, due to the nature of the recirculation bubble, reorganize to constitute a part of the rollup. Later in the fall, the wake loses symmetry and shows high population of vortical structures leading to turbulence. The asymmetric wake leads to strong interactions between the flow field and the cone evidenced by the shedding of a part of the 3D large-scale vortex rollup. This shedding process along with the cone rotation around its own axis provides a possible explanation of the helical wake structure observed in other studies.

  6. Hurricane track forecast cones from fluctuations

    NASA Astrophysics Data System (ADS)

    Meuel, T.; Prado, G.; Seychelles, F.; Bessafi, M.; Kellay, H.

    2012-06-01

    Trajectories of tropical cyclones may show large deviations from predicted tracks leading to uncertainty as to their landfall location for example. Prediction schemes usually render this uncertainty by showing track forecast cones representing the most probable region for the location of a cyclone during a period of time. By using the statistical properties of these deviations, we propose a simple method to predict possible corridors for the future trajectory of a cyclone. Examples of this scheme are implemented for hurricane Ike and hurricane Jimena. The corridors include the future trajectory up to at least 50 h before landfall. The cones proposed here shed new light on known track forecast cones as they link them directly to the statistics of these deviations.

  7. Hurricane track forecast cones from fluctuations.

    PubMed

    Meuel, T; Prado, G; Seychelles, F; Bessafi, M; Kellay, H

    2012-01-01

    Trajectories of tropical cyclones may show large deviations from predicted tracks leading to uncertainty as to their landfall location for example. Prediction schemes usually render this uncertainty by showing track forecast cones representing the most probable region for the location of a cyclone during a period of time. By using the statistical properties of these deviations, we propose a simple method to predict possible corridors for the future trajectory of a cyclone. Examples of this scheme are implemented for hurricane Ike and hurricane Jimena. The corridors include the future trajectory up to at least 50 h before landfall. The cones proposed here shed new light on known track forecast cones as they link them directly to the statistics of these deviations.

  8. Hurricane track forecast cones from fluctuations

    PubMed Central

    Meuel, T.; Prado, G.; Seychelles, F.; Bessafi, M.; Kellay, H.

    2012-01-01

    Trajectories of tropical cyclones may show large deviations from predicted tracks leading to uncertainty as to their landfall location for example. Prediction schemes usually render this uncertainty by showing track forecast cones representing the most probable region for the location of a cyclone during a period of time. By using the statistical properties of these deviations, we propose a simple method to predict possible corridors for the future trajectory of a cyclone. Examples of this scheme are implemented for hurricane Ike and hurricane Jimena. The corridors include the future trajectory up to at least 50 h before landfall. The cones proposed here shed new light on known track forecast cones as they link them directly to the statistics of these deviations. PMID:22701776

  9. Pure bending of a solid cone

    NASA Astrophysics Data System (ADS)

    Renton, J. D.

    1997-05-01

    The problems of torsion, axial loading and shear of a solid cone were solved around the turn of the century by Michell and Föppl. Surprisingly, no solution to the problem of the elastic response of a cone to the only other possible resultant applied to its apex seems to have been published until now. The method used here is based on certain theoretical considerations related to the author's work on generalizing the engineering theory of beams. This means that the result is derived rather than being the result of a trial-and-error process. A comparison is made with the usual engineering theory as modified for variable bending stiffness. The two analyses give the same results at the limit as the cone angle tends to zero.

  10. The flagellum in bacterial pathogens: For motility and a whole lot more.

    PubMed

    Chaban, Bonnie; Hughes, H Velocity; Beeby, Morgan

    2015-10-01

    The bacterial flagellum is an amazingly complex molecular machine with a diversity of roles in pathogenesis including reaching the optimal host site, colonization or invasion, maintenance at the infection site, and post-infection dispersal. Multi-megadalton flagellar motors self-assemble across the cell wall to form a reversible rotary motor that spins a helical propeller - the flagellum itself - to drive the motility of diverse bacterial pathogens. The flagellar motor responds to the chemoreceptor system to redirect swimming toward beneficial environments, thus enabling flagellated pathogens to seek out their site of infection. At their target site, additional roles of surface swimming and mechanosensing are mediated by flagella to trigger pathogenesis. Yet while these motility-related functions have long been recognized as virulence factors in bacteria, many bacteria have capitalized upon flagellar structure and function by adapting it to roles in other stages of the infection process. Once at their target site, the flagellum can assist adherence to surfaces, differentiation into biofilms, secretion of effector molecules, further penetration through tissue structures, or in activating phagocytosis to gain entry into eukaryotic cells. Next, upon onset of infection, flagellar expression must be adapted to deal with the host's immune system defenses, either by reduced or altered expression or by flagellar structural modification. Finally, after a successful growth phase on or inside a host, dispersal to new infection sites is often flagellar motility-mediated. Examining examples of all these processes from different bacterial pathogens, it quickly becomes clear that the flagellum is involved in bacterial pathogenesis for motility and a whole lot more. PMID:26541483

  11. PP2A in the regulation of cell motility and invasion.

    PubMed

    Basu, Sunanda

    2011-02-01

    Cell motility is a very critical phenomenon that plays an important role in the development of eukaryotic organisms. One of the well studied cell motility phenomena is chemotaxis, which is described as a directional movement of cell in response to changes in external chemotactic gradient. Numerous studies conducted both in unicellular organism and in mammalian cells have demonstrated the importance of phosphatidylionositol-3 kinase (PI3K) in this process. In addition, it is now well established that although PI3K plays an activation role in chemotaxis, the role of phosphatases is also critical to maintain this dynamic cyclical process. Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase that is a key player in regulating PI3K signaling. PP2A is abundantly and ubiquitously expressed and has been highly conserved during the evolution of eukaryotes. PP2A is composed of three protein subunits, A, B, and C. Subunit 'A' is a 60-65 kDa structural component, 'C' is a 36-38 kDa catalytic subunit, and 'B' is a 54-130 kDa regulatory subunit. The core complex of PP2A is comprised of the A and C subunits, which are tightly associated and this dimeric core complexes with the regulatory B subunit. The B subunit determines the substrate specificity as well as the spatial and temporal functions of PP2A. PP2A plays an important role in regulating multiple signal transduction pathways, including cell-cycle regulation, cell-growth and development, cytoskeleton dynamics, and cell motility. This review focuses on the role of PP2A in regulating motility of normal and transformed cells.

  12. The flagellum in bacterial pathogens: For motility and a whole lot more.

    PubMed

    Chaban, Bonnie; Hughes, H Velocity; Beeby, Morgan

    2015-10-01

    The bacterial flagellum is an amazingly complex molecular machine with a diversity of roles in pathogenesis including reaching the optimal host site, colonization or invasion, maintenance at the infection site, and post-infection dispersal. Multi-megadalton flagellar motors self-assemble across the cell wall to form a reversible rotary motor that spins a helical propeller - the flagellum itself - to drive the motility of diverse bacterial pathogens. The flagellar motor responds to the chemoreceptor system to redirect swimming toward beneficial environments, thus enabling flagellated pathogens to seek out their site of infection. At their target site, additional roles of surface swimming and mechanosensing are mediated by flagella to trigger pathogenesis. Yet while these motility-related functions have long been recognized as virulence factors in bacteria, many bacteria have capitalized upon flagellar structure and function by adapting it to roles in other stages of the infection process. Once at their target site, the flagellum can assist adherence to surfaces, differentiation into biofilms, secretion of effector molecules, further penetration through tissue structures, or in activating phagocytosis to gain entry into eukaryotic cells. Next, upon onset of infection, flagellar expression must be adapted to deal with the host's immune system defenses, either by reduced or altered expression or by flagellar structural modification. Finally, after a successful growth phase on or inside a host, dispersal to new infection sites is often flagellar motility-mediated. Examining examples of all these processes from different bacterial pathogens, it quickly becomes clear that the flagellum is involved in bacterial pathogenesis for motility and a whole lot more.

  13. Flavobacterium gliding motility and the type IX secretion system.

    PubMed

    McBride, Mark J; Nakane, Daisuke

    2015-12-01

    Cells of Flavobacterium johnsoniae crawl rapidly over surfaces in a process called gliding motility. These cells do not have flagella or pili but instead rely on a novel motility machine composed of proteins that are unique to the phylum Bacteroidetes. The motility adhesins SprB and RemA are propelled along the cell surface by the still poorly-defined gliding motor. Interaction of these adhesins with a surface results in translocation of the cell. SprB and RemA are delivered to the cell surface by the type IX secretion system (T9SS). T9SSs are confined to but common in the phylum Bacteroidetes. Transmembrane components of the T9SS may perform roles in both secretion and gliding motility. PMID:26461123

  14. Optical approaches to the study of foraminiferan motility.

    PubMed

    Travis, J L; Bowser, S S

    1988-01-01

    Microtubules are the major cytoskeletal component of foraminiferan reticulopodia. Video-enhanced differential interference contrast light microscopy has demonstrated that the microtubules serve as the intracellular tracks along which rapid bidirectional organelle transport and cell surface motility occurs. Microtubules appear to move, both axially and laterally within the pseudopodial cytoplasm, and these microtubule translocations appear to drive the various reticulopodial movements. F-actin is localized to discrete filament plaques form at sites of pseudopod-substrate adhesion. Correlative immunofluorescence and electron microscopy reveals a structural interaction between microtubules and the actin-containing filament plaques. Our recent data on reticulopodial motility are discussed in an historical context, and a model for foram motility, based on motile microtubules, is presented.

  15. Pediatric Gastrointestinal Motility Disorders: Challenges and a Clinical Update

    PubMed Central

    Chumpitazi, Bruno

    2008-01-01

    Pediatric gastrointestinal motility disorders are common and can range from relatively benign conditions such as functional constipation to more serious disorders such as achalasia, Hirschsprung disease, and intestinal pseudoobstruction. Performing and interpreting motility evaluations in children presents unique challenges and is complicated by a dearth of control information, underlying gastrointestinal developmental maturation, technical challenges (eg, catheter size limitations), and patient cooperation. Primary diseases such as congenital pseudoobstruction or Hirschsprung disease occur more often in children, but as with adults, abnormal motility may be secondary to other processes. Diagnostic studies include radiographic studies, manometry, breath testing, myoelectrical testing, and histologic evaluation. Although recent advances in technology, genetics, and biology are making an important impact and have allowed for a better understanding of the pathophysiology and therapy of gastrointestinal motility disorders in children, further research and new therapeutic agents are needed. PMID:21904491

  16. Bidirectional helical motility of cytoplasmic dynein around microtubules.

    PubMed

    Can, Sinan; Dewitt, Mark A; Yildiz, Ahmet

    2014-07-28

    Cytoplasmic dynein is a molecular motor responsible for minus-end-directed cargo transport along microtubules (MTs). Dynein motility has previously been studied on surface-immobilized MTs in vitro, which constrains the motors to move in two dimensions. In this study, we explored dynein motility in three dimensions using an MT bridge assay. We found that dynein moves in a helical trajectory around the MT, demonstrating that it generates torque during cargo transport. Unlike other cytoskeletal motors that produce torque in a specific direction, dynein generates torque in either direction, resulting in bidirectional helical motility. Dynein has a net preference to move along a right-handed helical path, suggesting that the heads tend to bind to the closest tubulin binding site in the forward direction when taking sideways steps. This bidirectional helical motility may allow dynein to avoid roadblocks in dense cytoplasmic environments during cargo transport.

  17. Ghrelin as a target for gastrointestinal motility disorders.

    PubMed

    Greenwood-Van Meerveld, Beverley; Kriegsman, Michael; Nelson, Richard

    2011-11-01

    The therapeutic potential of ghrelin and synthetic ghrelin receptor (GRLN-R) agonists for the treatment of gastrointestinal (GI) motility disorders is based on their ability to stimulate coordinated patterns of propulsive GI motility. This review focuses on the latest findings that support the therapeutic potential of GRLN-R agonists for the treatment of GI motility disorders. The review highlights the preclinical and clinical prokinetic effects of ghrelin and a series of novel ghrelin mimetics to exert prokinetic effects on the GI tract. We build upon a series of excellent reviews to critically discuss the evidence that supports the potential of GRLN-R agonists to normalize GI motility in patients with GI hypomotility disorders such as gastroparesis, post-operative ileus (POI), idiopathic chronic constipation and functional bowel disorders. PMID:21453735

  18. Lightcone: Light-cone generating script

    NASA Astrophysics Data System (ADS)

    Bernyk, Max

    2014-03-01

    Lightcone works with simulated galaxy data stored in a relational database to rearrange the data in a shape of a light-cone; simulated galaxy data is expected to be in a box volume. The light-cone constructing script works with output from the SAGE semi-analytic model, but will work with any other model that has galaxy positions (and other properties) saved per snapshots of the simulation volume distributed in time. The database configuration file is set up for PostgreSQL RDBMS, but can be modified for use with any other SQL database.

  19. Understanding Cone Photoreceptor Cell Death in Achromatopsia.

    PubMed

    Carvalho, Livia S; Vandenberghe, Luk H

    2016-01-01

    Colour vision is only achieved in the presence of healthy and functional cone photoreceptors found in the retina. It is an essential component of human vision and usually the first complaint patients undergoing vision degeneration have is the loss of daylight colour vision. Therefore, an understanding of the biology and basic mechanisms behind cone death under the degenerative state of retinal dystrophies and how the activation of the apoptotic pathway is triggered will provide valuable knowledge. It will also have broader applications for a spectrum of visual disorders and will be critical for future advances in translational research. PMID:26427416

  20. Mucin Promotes Rapid Surface Motility in Pseudomonas aeruginosa

    PubMed Central

    Yeung, Amy T. Y.; Parayno, Alicia; Hancock, Robert E. W.

    2012-01-01

    ABSTRACT An important environmental factor that determines the mode of motility adopted by Pseudomonas aeruginosa is the viscosity of the medium, often provided by adjusting agar concentrations in vitro. However, the viscous gel-like property of the mucus layer that overlays epithelial surfaces is largely due to the glycoprotein mucin. P. aeruginosa is known to swim within 0.3% (wt/vol) agar and swarm on the surface at 0.5% (wt/vol) agar with amino acids as a weak nitrogen source. When physiological concentrations or as little as 0.05% (wt/vol) mucin was added to the swimming agar, in addition to swimming, P. aeruginosa was observed to undergo highly accelerated motility on the surface of the agar. The surface motility colonies in the presence of mucin appeared to be circular, with a bright green center surrounded by a thicker white edge. While intact flagella were required for the surface motility in the presence of mucin, type IV pili and rhamnolipid production were not. Replacement of mucin with other wetting agents indicated that the lubricant properties of mucin might contribute to the surface motility. Based on studies with mutants, the quorum-sensing systems (las and rhl) and the orphan autoinducer receptor QscR played important roles in this form of surface motility. Transcriptional analysis of cells taken from the motility zone revealed the upregulation of genes involved in virulence and resistance. Based on these results, we suggest that mucin may be promoting a new or highly modified form of surface motility, which we propose should be termed “surfing.” PMID:22550036

  1. Basaltic Cone Suggests Constructional Origin of Some Guyots.

    PubMed

    Christensen, M N; Gilbert, C M

    1964-01-17

    A basaltic cinder cone was built beneath the waters of Mono Lake in Pleistocene time. This cone is now exposed. Its internal structure, external form, and petrography suggest that it was constructed with a flat top.

  2. Basaltic Cone Suggests Constructional Origin of Some Guyots.

    PubMed

    Christensen, M N; Gilbert, C M

    1964-01-17

    A basaltic cinder cone was built beneath the waters of Mono Lake in Pleistocene time. This cone is now exposed. Its internal structure, external form, and petrography suggest that it was constructed with a flat top. PMID:17753148

  3. Metal artifacts correction in cone-beam CT bone imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Ning, Ruola; Conover, David

    2007-03-01

    Cone-beam CT (CBCT) technique is needed by orthopaedists in their new studies to monitor bone volume growth and blood vessel growth of structural bone grafts used in reconstruction surgery. However, titanium plate and screws, which are commonly used to connect bone grafts to host bones, can cause severe streaking artifacts and shading artifact in the reconstructed images due to their high attenuation of x-rays. These metal artifacts will distort the information of the bone and cause difficulties when measuring bone volume growth and the inside blood vessel growth. To solve this problem and help orthopaedists quantitatively record the growth of bone grafts, we present a three-dimensional metal artifact correction technique to correct the streaking artifacts generated by titanium implants. In this project not only the artifacts need to be corrected but also the correct information of the bone is required in the image for the quantitative measurements. Both phantom studies and animal studies were conducted to test this correction method. Images without metal correction and images with metal correction were compared together, as well as the reference bone images acquired without metal. It's shown the streaking and shading artifacts were greatly reduced after metal correction. The accuracy of bone volume measurements was also greatly increased by 79% for phantom studies and 53% for animal studies.

  4. Effect of surface chemistry on in vitro actomyosin motility

    NASA Astrophysics Data System (ADS)

    Hanson, Kristi L.; Solana, Gerardin; Nicolau, Dan V.

    2005-02-01

    A variety of surface coatings were evaluated for their ability to promote in vitro actomyosin motility. Rabbit skeletal muscle heavy meromyosin (HMM) was adsorbed to uncoated glass and to surfaces coated with nitrocellulose, poly(methyl methacrylate) (PMMA), poly(butyl methacrylate) (PBMA), poly(tert-butyl methacrylate (PtBMA), polystyrene (PS) and hexamethyldisilazane (HMDS), and the myosin driven movement of fluorescently labeled actin filaments was recorded using epifluorescence microscopy. HMDS and uncoated glass did not support actomyosin motility, while mean velocities on other surfaces ranged from 1.7 μm sec-1 (PtBMA) to 3.5 μm sec-1 (NC). Nitrocellulose supported the highest proportion of motile filaments (75%), while 47 - 61% of filaments were motile on other surfaces. Within the methacrylate polymers, average filament velocities increased with decreasing hydrophobicity of the surface. Distributions of instantaneous acceleration values and angle deviations suggested more erratic and stuttered movement on the methacrylates and polystyrene than on NC, in line with qualitative visual observations. Despite the higher velocities and high proportion of motile filaments on NC, this surface resulted in a high proportion of small filaments and high rates of filament breakage during motility. Similar effects were observed on PS and PtBMA, while PBMA and PMMA supported longer filaments with less observed breakage.

  5. Power gain exhibited by motile mechanosensory neurons in Drosophila ears

    PubMed Central

    Göpfert, M. C.; Humphris, A. D. L.; Albert, J. T.; Robert, D.; Hendrich, O.

    2005-01-01

    In insects and vertebrates alike, hearing is assisted by the motility of mechanosensory cells. Much like pushing a swing augments its swing, this cellular motility is thought to actively augment vibrations inside the ear, thus amplifying the ear's mechanical input. Power gain is the hallmark of such active amplification, yet whether and how much energy motile mechanosensory cells contribute within intact auditory systems has remained uncertain. Here, we assess the mechanical energy provided by motile mechanosensory neurons in the antennal hearing organs of Drosophila melanogaster by analyzing the fluctuations of the sound receiver to which these neurons connect. By using dead WT flies and live mutants (tilB2, btv5P1, and nompA2) with defective neurons as a background, we show that the intact, motile neurons do exhibit power gain. In WT flies, the neurons lift the receiver's mean total energy by 19 zJ, which corresponds to 4.6 times the energy of the receiver's Brownian motion. Larger energy contributions (200 zJ) associate with self-sustained oscillations, suggesting that the neurons adjust their energy expenditure to optimize the receiver's sensitivity to sound. We conclude that motile mechanosensory cells provide active amplification; in Drosophila, mechanical energy contributed by these cells boosts the vibrations that enter the ear. PMID:15623551

  6. Power gain exhibited by motile mechanosensory neurons in Drosophila ears.

    PubMed