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Sample records for neurite mechanical tension

  1. Mechanisms of developmental neurite pruning

    PubMed Central

    Schuldiner, Oren; Yaron, Avraham

    2016-01-01

    The precise wiring of the nervous system is a combined outcome of progressive and regressive events during development. Axon guidance and synapse formation intertwined with cell death and neurite pruning sculpt the mature circuitry. It is now well recognized that pruning of dendrites and axons as means to refine neuronal networks, is a wide spread phenomena required for the normal development of vertebrate and invertebrate nervous systems. Here we will review the arising principles of cellular and molecular mechanisms of neurite pruning. We will discuss these principles in light of studies in multiple neuronal systems, and speculate on potential explanations for the emergence of neurite pruning as a mechanism to sculpt the nervous system. PMID:25213356

  2. Molecular mechanisms of neurite extension.

    PubMed Central

    Valtorta, F; Leoni, C

    1999-01-01

    The extension of neurites is a major task of developing neurons, requiring a significant metabolic effort to sustain the increase in molecular synthesis necessary for plasma membrane expansion. In addition, neurite extension involves changes in the subsets of expressed proteins and reorganization of the cytomatrix. These phenomena are driven by environmental cues which activate signal transduction processes as well as by the intrinsic genetic program of the cell. The present review summarizes some of the most recent progress made in the elucidation of the molecular mechanisms underlying these processes. PMID:10212488

  3. Tension and compression in the cytoskeleton of PC-12 neurites. II: Quantitative measurements

    PubMed Central

    1988-01-01

    We assessed the mechanical properties of PC-12 neurites by applying a force with calibrated glass needles and measured resulting changes in neurite length and deflection of the needle. We observed a linear relationship between force and length change that was not affected by multiple distensions and were thus able to determine neurite spring constants and initial, nondistended, rest tensions. 81 out of 82 neurites showed positive rest tensions ranging over three orders of magnitude with most values clustering around 30-40 mu dynes. Treatment with cytochalasin D significantly reduced neurite rest tensions to an average compression equal to 14% of the former tension and spring constants to an average of 17% of resting values. Treatment with nocodazole increased neurite rest tensions to an average of 282% of resting values but produced no change in spring constant. These observations suggest a particular type of complementary force interaction underlying axonal shape; the neurite actin network under tension and neurite microtubules under compression. Thermodynamics suggests that microtubule (MT) assembly may be regulated by changes in compressive load. We tested this effect by releasing neurite attachment to a polylysine-coated surface with polyaspartate, thus shifting external compressive support onto internal elements, and measuring the relative change in MT polymerization using quantitative Western blotting. Neurons grown on polylysine or collagen without further treatment had a 1:2 ratio of soluble to polymerized tubulin. When neurites grown on polylysine were treated with 1% polyaspartate for 15- 30 min, 80% of neurites retracted, shifting the soluble: polymerized tubulin ratio to 1:1. Polyaspartate treatment of cells grown on collagen, or grown on polylysine but treated with cytochalasin to reduce tension, caused neither retraction nor a change in the soluble:polymerized tubulin ratio. We suggest that the release of adhesion to the dish shifted the compressive

  4. Drag force as a tool to test the active mechanical response of PC12 neurites.

    PubMed

    Bernal, Roberto; Melo, Francisco; Pullarkat, Pramod A

    2010-02-17

    We investigate the mechanical response of PC12 neurites subjected to a drag force imposed by a laminar flow perpendicular to the neurite axis. The curvature of the catenary shape acquired by an initially straight neurite under the action of the drag force provides information on both elongation and tension of the neurite. This method allows us to measure the rest tension and viscoelastic parameters of PC12 neurites and active behavior of neurites. Measurement of oscillations in the strain rate of neurites at constant flow rate provides insight on the response of molecular motors and additional support for the presence of a negative strain-rate sensitivity region in the global mechanical response of PC12 neurites. Copyright 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  5. Dynamic peripheral traction forces balance stable neurite tension in regenerating Aplysia bag cell neurons.

    PubMed

    Hyland, Callen; Mertz, Aaron F; Forscher, Paul; Dufresne, Eric

    2014-05-14

    Growth cones of elongating neurites exert force against the external environment, but little is known about the role of force in outgrowth or its relationship to the mechanical organization of neurons. We used traction force microscopy to examine patterns of force in growth cones of regenerating Aplysia bag cell neurons. We find that traction is highest in the peripheral actin-rich domain and internal stress reaches a plateau near the transition between peripheral and central microtubule-rich domains. Integrating stress over the area of the growth cone reveals that total scalar force increases with area but net tension on the neurite does not. Tensions fall within a limited range while a substantial fraction of the total force can be balanced locally within the growth cone. Although traction continuously redistributes during extension and retraction of the peripheral domain, tension is stable over time, suggesting that tension is a tightly regulated property of the neurite independent of growth cone dynamics. We observe that redistribution of traction in the peripheral domain can reorient the end of the neurite shaft. This suggests a role for off-axis force in growth cone turning and neuronal guidance.

  6. Dynamic peripheral traction forces balance stable neurite tension in regenerating Aplysia bag cell neurons

    PubMed Central

    Hyland, Callen; Mertz, Aaron F.; Forscher, Paul; Dufresne, Eric

    2014-01-01

    Growth cones of elongating neurites exert force against the external environment, but little is known about the role of force in outgrowth or its relationship to the mechanical organization of neurons. We used traction force microscopy to examine patterns of force in growth cones of regenerating Aplysia bag cell neurons. We find that traction is highest in the peripheral actin-rich domain and internal stress reaches a plateau near the transition between peripheral and central microtubule-rich domains. Integrating stress over the area of the growth cone reveals that total scalar force increases with area but net tension on the neurite does not. Tensions fall within a limited range while a substantial fraction of the total force can be balanced locally within the growth cone. Although traction continuously redistributes during extension and retraction of the peripheral domain, tension is stable over time, suggesting that tension is a tightly regulated property of the neurite independent of growth cone dynamics. We observe that redistribution of traction in the peripheral domain can reorient the end of the neurite shaft. This suggests a role for off-axis force in growth cone turning and neuronal guidance. PMID:24825441

  7. Neurite, a Finite Difference Large Scale Parallel Program for the Simulation of Electrical Signal Propagation in Neurites under Mechanical Loading

    PubMed Central

    García-Grajales, Julián A.; Rucabado, Gabriel; García-Dopico, Antonio; Peña, José-María; Jérusalem, Antoine

    2015-01-01

    With the growing body of research on traumatic brain injury and spinal cord injury, computational neuroscience has recently focused its modeling efforts on neuronal functional deficits following mechanical loading. However, in most of these efforts, cell damage is generally only characterized by purely mechanistic criteria, functions of quantities such as stress, strain or their corresponding rates. The modeling of functional deficits in neurites as a consequence of macroscopic mechanical insults has been rarely explored. In particular, a quantitative mechanically based model of electrophysiological impairment in neuronal cells, Neurite, has only very recently been proposed. In this paper, we present the implementation details of this model: a finite difference parallel program for simulating electrical signal propagation along neurites under mechanical loading. Following the application of a macroscopic strain at a given strain rate produced by a mechanical insult, Neurite is able to simulate the resulting neuronal electrical signal propagation, and thus the corresponding functional deficits. The simulation of the coupled mechanical and electrophysiological behaviors requires computational expensive calculations that increase in complexity as the network of the simulated cells grows. The solvers implemented in Neurite—explicit and implicit—were therefore parallelized using graphics processing units in order to reduce the burden of the simulation costs of large scale scenarios. Cable Theory and Hodgkin-Huxley models were implemented to account for the electrophysiological passive and active regions of a neurite, respectively, whereas a coupled mechanical model accounting for the neurite mechanical behavior within its surrounding medium was adopted as a link between electrophysiology and mechanics. This paper provides the details of the parallel implementation of Neurite, along with three different application examples: a long myelinated axon, a segmented

  8. Snapping mechanical metamaterials under tension.

    PubMed

    Rafsanjani, Ahmad; Akbarzadeh, Abdolhamid; Pasini, Damiano

    2015-10-21

    A snapping mechanical metamaterial is designed, which exhibits a sequential snap-through behavior under tension. The tensile response of this mechanical metamaterial can be altered by tuning the architecture of the snapping segments to achieve a range of nonlinear mechanical responses, including monotonic, S-shaped, plateau, and non-monotonic snap-through behavior.

  9. Time-resolved neurite mechanics by thermal fluctuation assessments.

    PubMed

    Gárate, Fernanda; Betz, Timo; Pertusa, María; Bernal, Roberto

    2015-12-30

    In the absence of simple noninvasive measurements, the knowledge of temporal and spatial variations of axons mechanics remains scarce. By extending thermal fluctuation spectroscopy (TFS) to long protrusions, we determine the transverse amplitude thermal fluctuation spectra that allow direct and simultaneous access to three key mechanics parameters: axial tension, bending flexural rigidity and plasma membrane tension. To test our model, we use PC12 cell protrusions-a well-know biophysical model of axons-in order to simplify the biological system under scope. For instance, axial and plasma membrane tension are found in the range of nano Newton and tens of pico Newtons per micron respectively. Furthermore, our results shows that the TFS technique is capable to distinguish quasi-identical protrusions. Another advantage of our approach is the time resolved nature of the measurements. Indeed, in the case of long term experiments on PC12 protrusions, TFS has revealed large temporal, correlated variations of the protrusion mechanics, displaying extraordinary feedback control over the axial tension in order to maintain a constant tension value.

  10. Active transport of vesicles in neurons is modulated by mechanical tension.

    PubMed

    Ahmed, Wylie W; Saif, Taher A

    2014-03-27

    Effective intracellular transport of proteins and organelles is critical in cells, and is especially important for ensuring proper neuron functionality. In neurons, most proteins are synthesized in the cell body and must be transported through thin structures over long distances where normal diffusion is insufficient. Neurons transport subcellular cargo along axons and neurites through a stochastic interplay of active and passive transport. Mechanical tension is critical in maintaining proper function in neurons, but its role in transport is not well understood. To this end, we investigate the active and passive transport of vesicles in Aplysia neurons while changing neurite tension via applied strain, and quantify the resulting dynamics. We found that tension in neurons modulates active transport of vesicles by increasing the probability of active motion, effective diffusivity, and induces a retrograde bias. We show that mechanical tension modulates active transport processes in neurons and that external forces can couple to internal (subcellular) forces and change the overall transport dynamics.

  11. Active transport of vesicles in neurons is modulated by mechanical tension

    PubMed Central

    Ahmed, Wylie W.; Saif, Taher A.

    2014-01-01

    Effective intracellular transport of proteins and organelles is critical in cells, and is especially important for ensuring proper neuron functionality. In neurons, most proteins are synthesized in the cell body and must be transported through thin structures over long distances where normal diffusion is insufficient. Neurons transport subcellular cargo along axons and neurites through a stochastic interplay of active and passive transport. Mechanical tension is critical in maintaining proper function in neurons, but its role in transport is not well understood. To this end, we investigate the active and passive transport of vesicles in Aplysia neurons while changing neurite tension via applied strain, and quantify the resulting dynamics. We found that tension in neurons modulates active transport of vesicles by increasing the probability of active motion, effective diffusivity, and induces a retrograde bias. We show that mechanical tension modulates active transport processes in neurons and that external forces can couple to internal (subcellular) forces and change the overall transport dynamics. PMID:24670781

  12. Active transport of vesicles in neurons is modulated by mechanical tension

    NASA Astrophysics Data System (ADS)

    Ahmed, Wylie W.; Saif, Taher A.

    2014-03-01

    Effective intracellular transport of proteins and organelles is critical in cells, and is especially important for ensuring proper neuron functionality. In neurons, most proteins are synthesized in the cell body and must be transported through thin structures over long distances where normal diffusion is insufficient. Neurons transport subcellular cargo along axons and neurites through a stochastic interplay of active and passive transport. Mechanical tension is critical in maintaining proper function in neurons, but its role in transport is not well understood. To this end, we investigate the active and passive transport of vesicles in Aplysia neurons while changing neurite tension via applied strain, and quantify the resulting dynamics. We found that tension in neurons modulates active transport of vesicles by increasing the probability of active motion, effective diffusivity, and induces a retrograde bias. We show that mechanical tension modulates active transport processes in neurons and that external forces can couple to internal (subcellular) forces and change the overall transport dynamics.

  13. 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.

  14. Uridine from Pleurotus giganteus and Its Neurite Outgrowth Stimulatory Effects with Underlying Mechanism

    PubMed Central

    Phan, Chia-Wei; David, Pamela; Wong, Kah-Hui; Naidu, Murali; Sabaratnam, Vikineswary

    2015-01-01

    Neurodegenerative diseases are linked to neuronal cell death and impairment of neurite outgrowth. An edible mushroom, Pleurotus giganteus was found to stimulate neurite outgrowth in vitro but the chemical constituents and the underlying mechanism is yet to be elucidated. The chemical constituents of P. giganteus (linoleic acid, oleic acid, cinnamic acid, caffeic acid, p-coumaric acid, succinic acid, benzoic acid, and uridine) were tested for neurite outgrowth activity. Uridine (100 μM) was found to increase the percentage of neurite-bearing cells of differentiating neuroblastoma (N2a) cells by 43.1±0.5%, which was 1.8-fold higher than NGF (50 ng/mL)-treated cells. Uridine which was present in P. giganteus (1.80±0.03 g/100g mushroom extract) increased the phosphorylation of extracellular-signal regulated kinases (ERKs) and protein kinase B (Akt). Further, phosphorylation of the mammalian target of rapamycin (mTOR) was also increased. MEK/ERK and PI3K-Akt-mTOR further induced phosphorylation of cAMP-response element binding protein (CREB) and expression of growth associated protein 43 (GAP43); all of which promoted neurite outgrowth of N2a cells. This study demonstrated that P. giganteus may enhance neurite outgrowth and one of the key bioactive molecules responsible for neurite outgrowth is uridine. PMID:26565787

  15. Uridine from Pleurotus giganteus and Its Neurite Outgrowth Stimulatory Effects with Underlying Mechanism.

    PubMed

    Phan, Chia-Wei; David, Pamela; Wong, Kah-Hui; Naidu, Murali; Sabaratnam, Vikineswary

    2015-01-01

    Neurodegenerative diseases are linked to neuronal cell death and impairment of neurite outgrowth. An edible mushroom, Pleurotus giganteus was found to stimulate neurite outgrowth in vitro but the chemical constituents and the underlying mechanism is yet to be elucidated. The chemical constituents of P. giganteus (linoleic acid, oleic acid, cinnamic acid, caffeic acid, p-coumaric acid, succinic acid, benzoic acid, and uridine) were tested for neurite outgrowth activity. Uridine (100 μM) was found to increase the percentage of neurite-bearing cells of differentiating neuroblastoma (N2a) cells by 43.1 ± 0.5%, which was 1.8-fold higher than NGF (50 ng/mL)-treated cells. Uridine which was present in P. giganteus (1.80 ± 0.03 g/100g mushroom extract) increased the phosphorylation of extracellular-signal regulated kinases (ERKs) and protein kinase B (Akt). Further, phosphorylation of the mammalian target of rapamycin (mTOR) was also increased. MEK/ERK and PI3K-Akt-mTOR further induced phosphorylation of cAMP-response element binding protein (CREB) and expression of growth associated protein 43 (GAP43); all of which promoted neurite outgrowth of N2a cells. This study demonstrated that P. giganteus may enhance neurite outgrowth and one of the key bioactive molecules responsible for neurite outgrowth is uridine.

  16. Sonic hedgehog stimulates neurite outgrowth in a mechanical stretch model of reactive-astrogliosis.

    PubMed

    Berretta, Antonio; Gowing, Emma K; Jasoni, Christine L; Clarkson, Andrew N

    2016-02-23

    Although recovery following a stroke is limited, undamaged neurons under the right conditions can establish new connections and take on-board lost functions. Sonic hedgehog (Shh) signaling is integral for developmental axon growth, but its role after injury has not been fully examined. To investigate the effects of Shh on neuronal sprouting after injury, we used an in vitro model of glial scar, whereby cortical astrocytes were mechanically traumatized to mimic reactive astrogliosis observed after stroke. This mechanical trauma impaired neurite outgrowth from post-natal cortical neurons plated on top of reactive astrocytes. Addition of Shh to the media, however, resulted in a concentration-dependent increase in neurite outgrowth. This response was inhibited by cyclopamine and activated by oxysterol 20(S)-hydroxycholesterol, both of which modulate the activity of the Shh co-receptor Smoothened (Smo), demonstrating that Shh-mediated neurite outgrowth is Smo-dependent. In addition, neurite outgrowth was not associated with an increase in Gli-1 transcription, but could be inhibited by PP2, a selective inhibitor of Src family kinases. These results demonstrate that neurons exposed to the neurite growth inhibitory environment associated with a glial scar can be stimulated by Shh, with signaling occurring through a non-canonical pathway, to overcome this suppression and stimulate neurite outgrowth.

  17. A model for neurite growth and neuronal morphogenesis.

    PubMed

    Li, G H; Qin, C D

    1996-02-01

    A model is presented for tensile regulation of neuritic growth. It is proposed that the neurite tension can be determined by Hooke's law and determines the growth rate of neurites. The growth of a neurite is defined as the change in its unstretched length. Neuritic growth rate is assumed to increase in proportion to tension magnitude over a certain threshold [Dennerll et al., J. Cell Biol. 107: 665-674 (1988)]. The movement of branch nodes also contributes to the neuronal morphogenesis. It is supposed that the rate of a branch-node displacement is in proportion to the resultant neuritic tension exerted on this node. To deal with the growth-cone movement, it is further supposed that the environment exerts a traction force on the growth cone and the rate of growth-cone displacement is determined by the vector sum of the neuritic tension and the traction force. A group of differential equations are used to describe the model. The key point of the model is that the traction force and the neuritic tension are in opposition to generate a temporal contrast-enhancing mechanism. Results of a simulation study suggest that the model can explain some phenomena related to neuronal morphogenesis.

  18. Elastic properties and mechanical tension of graphene

    NASA Astrophysics Data System (ADS)

    Ramírez, R.; Herrero, C. P.

    2017-01-01

    Room-temperature simulations of graphene have been performed as a function of the mechanical tension of the layer. Finite-size effects are accurately reproduced by an acoustic dispersion law for the out-of-plane vibrations that, in the long-wave limit, behaves as ρ ω2=σ k2+κ k4 . The fluctuation tension σ is finite (˜0.1 N/m) even when the external mechanical tension vanishes. Transverse vibrations imply a duplicity in the definition of the elastic constants of the layer, as observables related to the real area of the surface may differ from those related to the in-plane projected area. This duplicity explains the variability of experimental data on the Young modulus of graphene based on electron spectroscopy, interferometric profilometry, and indentation experiments.

  19. Modelling RNA folding under mechanical tension

    PubMed Central

    VIEREGG, JEFFREY R.; TINOCO, IGNACIO

    2006-01-01

    We investigate the thermodynamics and kinetics of RNA unfolding and refolding under mechanical tension. The hierarchical nature of RNA structure and the existence of thermodynamic parameters for base pair formation based on nearest-neighbour interactions allows modelling of sequence-dependent folding dynamics for any secondary structure. We calculate experimental observables such as the transition force for unfolding, the end-to-end distribution function and its variance, as well as kinetic information, for a representative RNA sequence and for a sequence containing two homopolymer segments: A.U and G.C. PMID:16969426

  20. Mechanical tension drives cell membrane fusion.

    PubMed

    Kim, Ji Hoon; Ren, Yixin; Ng, Win Pin; Li, Shuo; Son, Sungmin; Kee, Yee-Seir; Zhang, Shiliang; Zhang, Guofeng; Fletcher, Daniel A; Robinson, Douglas N; Chen, Elizabeth H

    2015-03-09

    Membrane fusion is an energy-consuming process that requires tight juxtaposition of two lipid bilayers. Little is known about how cells overcome energy barriers to bring their membranes together for fusion. Previously, we have shown that cell-cell fusion is an asymmetric process in which an "attacking" cell drills finger-like protrusions into the "receiving" cell to promote cell fusion. Here, we show that the receiving cell mounts a Myosin II (MyoII)-mediated mechanosensory response to its invasive fusion partner. MyoII acts as a mechanosensor, which directs its force-induced recruitment to the fusion site, and the mechanosensory response of MyoII is amplified by chemical signaling initiated by cell adhesion molecules. The accumulated MyoII, in turn, increases cortical tension and promotes fusion pore formation. We propose that the protrusive and resisting forces from fusion partners put the fusogenic synapse under high mechanical tension, which helps to overcome energy barriers for membrane apposition and drives cell membrane fusion. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Effect of wire tension on stiffness of tensioned fine wires in external fixation: a mechanical study.

    PubMed

    Antoci, Valentin; Voor, Michael J; Antoci, Valentin; Roberts, Craig S

    2007-09-01

    To determine the effect of changes in magnitude of transfixion wire tension on stiffness of fine-wire external-fixation load deformation, we compared results obtained with different wire tensions (50-140 kg) under identical conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion. Stiffness values were calculated from the load-deformation and torque-angle curves. Tension of 140 kg provided the most stiffness, and there was a trend toward increasing overall stiffness with increasing wire tension. The 1.8-mm wires should be tensioned to at least 110 kg in most cases of fine-wire external fixation; compared with all tensions less than 110 kg, this tension provides significantly more mechanical stability in all loading modes.

  2. Space Station Freedom Solar Array tension mechanism development

    NASA Technical Reports Server (NTRS)

    Allmon, Curtis; Haugen, Bert

    1994-01-01

    A tension mechanism is used to apply a tension force to the Space Station Freedom Solar Array Blanket. This tension is necessary to meet the deployed frequency requirement of the array as well as maintain the flatness of the flexible substrate solar cell blanket. The mechanism underwent a series of design iterations before arriving at the final design. This paper discusses the design and testing of the mechanism.

  3. Mechanisms controlling neurite outgrowth in a pheochromocytoma cell line: the role of TRPC channels.

    PubMed

    Kumar, Sanjay; Chakraborty, Saikat; Barbosa, Cindy; Brustovetsky, Tatiana; Brustovetsky, Nickolay; Obukhov, Alexander G

    2012-04-01

    Transient Receptor Potential Canonical (TRPC) channels are implicated in modulating neurite outgrowth. The expression pattern of TRPCs changes significantly during brain development, suggesting that fine-tuning TRPC expression may be important for orchestrating neuritogenesis. To study how alterations in the TRPC expression pattern affect neurite outgrowth, we used nerve growth factor (NGF)-differentiated rat pheochromocytoma 12 (PC12) cells, a model system for neuritogenesis. In PC12 cells, NGF markedly up-regulated TRPC1 and TRPC6 expression, but down-regulated TRPC5 expression while promoting neurite outgrowth. Overexpression of TRPC1 augmented, whereas TRPC5 overexpression decelerated NGF-induced neurite outgrowth. Conversely, shRNA-mediated knockdown of TRPC1 decreased, whereas shRNA-mediated knockdown of TRPC5 increased NGF-induced neurite extension. Endogenous TRPC1 attenuated the anti-neuritogenic effect of overexpressed TRPC5 in part by forming the heteromeric TRPC1-TRPC5 channels. Previous reports suggested that TRPC6 may facilitate neurite outgrowth. However, we found that TRPC6 overexpression slowed down neuritogenesis, whereas dominant negative TRPC6 (DN-TRPC6) facilitated neurite outgrowth in NGF-differentiated PC12 cells. Consistent with these findings, hyperforin, a neurite outgrowth promoting factor, decreased TRPC6 expression in NGF-differentiated PC12 cells. Using pharmacological and molecular biological approaches, we determined that NGF up-regulated TRPC1 and TRPC6 expression via a p75(NTR)-IKK(2)-dependent pathway that did not involve TrkA receptor signaling in PC12 cells. Similarly, NGF up-regulated TRPC1 and TRPC6 via an IKK(2) dependent pathway in primary cultured hippocampal neurons. Thus, our data suggest that a balance of TRPC1, TRPC5, and TRPC6 expression determines neurite extension rate in neural cells, with TRPC6 emerging as an NGF-dependent "molecular damper" maintaining a submaximal velocity of neurite extension.

  4. Optimization of adult sensory neuron electroporation to study mechanisms of neurite growth

    PubMed Central

    McCall, Julianne; Nicholson, LaShae; Weidner, Norbert; Blesch, Armin

    2012-01-01

    The development of eukaryotic transfection technologies has been rapid in recent years, providing the opportunity to better analyze cell-autonomous mechanisms influencing various cellular processes, including cell-intrinsic regulators of regenerative neurite growth and survival. Electroporation is one of the more effective methodologies for transfection of post-mitotic neurons demonstrating sufficient neuronal survival and transfection efficiency. To further maximize the number of transfected neurons especially with large plasmids, to limit the cellular exposure to serum, and to minimize the number of animals required for cell isolation per experiment, we compared two state-of-the-art electroporation devices for in vitro transfection of adult rat dorsal root ganglion (DRG) neuron cultures. By refining different parameters, transfection efficiencies of 39–42% could be achieved using the Lonza 4D-Nucleofector X-unit system, 1.5–2-fold higher rates than those that have been previously published for adult DRG neurons using smaller plasmid sizes. Our protocol further limits the number of cells required to 3 × 105 cells per 20 μl reaction using only 2 μg DNA/reaction and allows for the complete omission of serum post-transfection. Application of this optimized protocol will contribute to furthering the study of neuron-intrinsic mechanisms responsible for growth and survival under physiological and pathophysiological conditions. PMID:22347167

  5. Potential Mechanism of Neurite Outgrowth Enhanced by Electrical Stimulation: Involvement of MicroRNA-363-5p Targeting DCLK1 Expression in Rat.

    PubMed

    Quan, Xin; Huang, Liangliang; Yang, Yafeng; Ma, Teng; Liu, Zhongyang; Ge, Jun; Huang, Jinghui; Luo, Zhuojing

    2017-02-01

    Electrical stimulation (ES) promotes neurite outgrowth and nerve regeneration, but the underlying mechanisms remain undefined. In the present study, we investigated the role of micro RNAs (miRNAs) in ES-mediated neurite outgrowth. First, we performed microarray analyses to identify changes in the miRNAs profile of dorsal root ganglion neurons (DRGNs) following ES. The expression of 16 known miRNAs was altered by ES. Bioinformatics showed that the potential targets of these differentially expressed miRNAs were involved in neurite outgrowth. We focused on miRNA-363-5p (miR-363-5p), because its expression was consistently altered by ES in the present study. Silencing miR-363-5p promoted neurite outgrowth, while miR-363-5p mimic reduced neurite outgrowth. Downregulation of miR-363-5p indicated that double cortin-like kinase (DCLK) 1, a major microtubule-associated protein, was a direct target of miR-363-5p in DRGNs. Knockdown of DCLK1 recapitulated the beneficial effect of a miR-363-5p inhibitor on DRG neurite outgrowth. In conclusion, our data has indicated that miR-363-5p is involved in ES-promoted neurite outgrowth by targeting DCLK1. These findings provide new insights into the roles of miRNAs in ES-enhanced neurite outgrowth and regeneration.

  6. Effects of DS-modified agarose gels on neurite extension in 3D scaffold through mechanisms other than changing the pore radius of the gels.

    PubMed

    Peng, Jin; Pan, Qian; Zhang, Wei; Yang, Hao; Zhou, Xue; Jiang, Hua

    2014-07-01

    Dermatan sulfate is widely distributed as glycosaminoglycan side chains of proteoglycans, which are the main components of glial scar and inhibit neurite regeneration after nerve injury. However its role in the inhibiting process is not clear. Understanding neurite extension in three-dimensional scaffolds is critical for neural tissue engineering. This study used agarose gels modified with dermatan sulfate as the three-dimensional culture scaffold. We explored structure-function relationship between the three-dimensional scaffold and neurite extension and examined the role of dermatan sulfate on neurite extension in the three-dimensional scaffold. A range of agarose concentrations was used to generate varied gel physical structures and the corresponding neurite extension of embryonic day (E9) chick dorsal root ganglia was examined. We measured gel stiffness and gel pore size to determine whether dermatan sulfate changed the gels' conformation. As gel concentration increased, neurite length and gel pore size decreased, and gel stiffness increased. At 1.00 and 1.25% (wt/vol) concentrations, dermatan sulfates both immobilized with agarose gels and dissolved in culture medium inhibit neurite extension. While at 1.50 and 1.75% (wt/vol) concentrations, only immobilized dermatan sulfate worked. Immobilized dermatan sulfate could modify molecular shape of agarose gels, decrease gel pore size statistically, but did not influence gel stiffness. We have proved that the decrease of gel pore size is insufficient to inhibit neurite extension. These results indicate that dermatan sulfate inhibits neurite extension not through forming a mechanical barrier. Maybe its interaction with neuron membrane is the key factor in neurite extension.

  7. Bioassay, isolation and studies on the mechanism of action of neurite extension factor

    NASA Technical Reports Server (NTRS)

    Kligman, D.

    1984-01-01

    The identification and purification of molecules active in promoting neurite outgrowth requires a sensitive reproducible bioassay. A quantitative bioassay was utilized to purify a neurite extension factor (NEF) based on counting the number of phase bright neurons with processes at least equal to one cell body diameter after 20 hrs. in culture is defined, serum free medium. Using a combination of heat treatment DEAE cellulose chromatography and gel filtration, an acidic protein of M sub r = 75,000 was highly purified. Upon reduction, it yields subunits of M sub r = 37,000. Purified fractions are active half maximally at 100 ng/ml in inducing neurite outgrowth in this bioassay. Currently, monoclonal antibodies to NEF are being produced. Female Balb C mice were immunized with the antigen and fusions with mouse myeloma cells will be performed to yield hybridoma cells.

  8. Bioassay, isolation and studies on the mechanism of action of neurite extension factor

    NASA Technical Reports Server (NTRS)

    Kligman, D.

    1984-01-01

    The identification and purification of molecules active in promoting neurite outgrowth requires a sensitive reproducible bioassay. A quantitative bioassay was utilized to purify a neurite extension factor (NEF) based on counting the number of phase bright neurons with processes at least equal to one cell body diameter after 20 hrs. in culture is defined, serum free medium. Using a combination of heat treatment DEAE cellulose chromatography and gel filtration, an acidic protein of M sub r = 75,000 was highly purified. Upon reduction, it yields subunits of M sub r = 37,000. Purified fractions are active half maximally at 100 ng/ml in inducing neurite outgrowth in this bioassay. Currently, monoclonal antibodies to NEF are being produced. Female Balb C mice were immunized with the antigen and fusions with mouse myeloma cells will be performed to yield hybridoma cells.

  9. Panaxynol induces neurite outgrowth in PC12D cells via cAMP- and MAP kinase-dependent mechanisms.

    PubMed

    Wang, Ze-Jian; Nie, Bao-Ming; Chen, Hong-Zhuan; Lu, Yang

    2006-01-05

    Panaxynol, a polyacetylene ((3R)-heptadeca-1,9-diene-4,6-diyn-3-ol; syn. falcarinol), was isolated from the lipophilic fractions of Panax notoginseng, a Chinese traditional medicinal plant. In the present study, we reported the neurotrophic effects of panaxynol on PC12D cells and mechanism involved in neurite outgrowth of the cells. Panaxynol could morphologically promote neurite outgrowth in PC12D cells, concentration-dependently reduce cell division and up-regulate molecular marker (MAP1B) expression in PC12D cells. Panaxynol induces the elevation of intracellular cAMP in PC12D cells. The neurite outgrowth in PC12D cells induced by panaxynol could be inhibited by the protein kinase A inhibitor RpcAMPS and by MAP kinase kinase 1/2 inhibitor U0126. These observations reveal that panaxynol could induce the differentiation of PC12D cells in a process similar to but distinct from that of NGF and the panaxynol's effects were via cAMP- and MAP kinase-dependent mechanisms.

  10. [Inhibitory proteins of neuritic regeneration in the extracellular matrix: structure, molecular interactions and their functions. Mechanisms of extracellular balance].

    PubMed

    Vargas, Javier; Uribe-Escamilla, Rebeca; Alfaro-Rodríguez, Alfonso

    2013-01-01

    After injury of the central nervous system (CNS) in higher vertebrates, neurons neither grow nor reconnect with their targets because their axons or dendrites cannot regenerate within the injured site. In the CNS, the signal from the environment regulating neurite regeneration is not exclusively generated by one molecular group. This signal is generated by the interaction of various types of molecules such as extracellular matrix proteins, soluble factors and surface membrane molecules; all these elements interact with one another generating the matrix's biological state: the extracellular balance. Proteins in the balanced extracellular matrix, support and promote cellular physiological states, including neuritic regeneration. We have reviewed three types of proteins of the extracellular matrix possessing an inhibitory effect and that are determinant of neuritic regeneration failure in the CNS: chondroitin sulfate proteoglycans, keratan sulfate proteoglycans and tenascin. We also review some of the mechanisms involved in the balance of extracellular proteins such as isomerization, epimerization, sulfation and glycosylation as well as the assemblage of the extracellular matrix, the interaction between the matrix and soluble factors and its proteolytic degradation. In the final section, we have presented some examples of the matrix's role in development and in tumor propagation.

  11. Measurement of dynamic surface tension by mechanically vibrated sessile droplets.

    PubMed

    Iwata, Shuichi; Yamauchi, Satoko; Yoshitake, Yumiko; Nagumo, Ryo; Mori, Hideki; Kajiya, Tadashi

    2016-04-01

    We developed a novel method for measuring the dynamic surface tension of liquids using mechanically vibrated sessile droplets. Under continuous mechanical vibration, the shape of the deformed droplet was fitted by numerical analysis, taking into account the force balance at the drop surface and the momentum equation. The surface tension was determined by optimizing four parameters: the surface tension, the droplet's height, the radius of the droplet-substrate contact area, and the horizontal symmetrical position of the droplet. The accuracy and repeatability of the proposed method were confirmed using drops of distilled water as well as viscous aqueous glycerol solutions. The vibration frequency had no influence on surface tension in the case of pure liquids. However, for water-soluble surfactant solutions, the dynamic surface tension gradually increased with vibration frequency, which was particularly notable for low surfactant concentrations slightly below the critical micelle concentration. This frequency dependence resulted from the competition of two mechanisms at the drop surface: local surface deformation and surfactant transport towards the newly generated surface.

  12. Measurement of dynamic surface tension by mechanically vibrated sessile droplets

    NASA Astrophysics Data System (ADS)

    Iwata, Shuichi; Yamauchi, Satoko; Yoshitake, Yumiko; Nagumo, Ryo; Mori, Hideki; Kajiya, Tadashi

    2016-04-01

    We developed a novel method for measuring the dynamic surface tension of liquids using mechanically vibrated sessile droplets. Under continuous mechanical vibration, the shape of the deformed droplet was fitted by numerical analysis, taking into account the force balance at the drop surface and the momentum equation. The surface tension was determined by optimizing four parameters: the surface tension, the droplet's height, the radius of the droplet-substrate contact area, and the horizontal symmetrical position of the droplet. The accuracy and repeatability of the proposed method were confirmed using drops of distilled water as well as viscous aqueous glycerol solutions. The vibration frequency had no influence on surface tension in the case of pure liquids. However, for water-soluble surfactant solutions, the dynamic surface tension gradually increased with vibration frequency, which was particularly notable for low surfactant concentrations slightly below the critical micelle concentration. This frequency dependence resulted from the competition of two mechanisms at the drop surface: local surface deformation and surfactant transport towards the newly generated surface.

  13. The death receptor antagonist FAIM promotes neurite outgrowth by a mechanism that depends on ERK and NF-κB signaling

    PubMed Central

    Sole, Carme; Dolcet, Xavier; Segura, Miguel F.; Gutierrez, Humberto; Diaz-Meco, Maria-Teresa; Gozzelino, Raffaella; Sanchis, Daniel; Bayascas, Jose R.; Gallego, Carme; Moscat, Jorge; Davies, Alun M.; Comella, Joan X.

    2004-01-01

    Fas apoptosis inhibitory molecule (FAIM) is a protein identified as an antagonist of Fas-induced cell death. We show that FAIM overexpression fails to rescue neurons from trophic factor deprivation, but exerts a marked neurite growth–promoting action in different neuronal systems. Whereas FAIM overexpression greatly enhanced neurite outgrowth from PC12 cells and sympathetic neurons grown with nerve growth factor (NGF), reduction of endogenous FAIM levels by RNAi decreased neurite outgrowth in these cells. FAIM overexpression promoted NF-κB activation, and blocking this activation by using a super-repressor IκBα or by carrying out experiments using cortical neurons from mice that lack the p65 NF-κB subunit prevented FAIM-induced neurite outgrowth. The effect of FAIM on neurite outgrowth was also blocked by inhibition of the Ras–ERK pathway. Finally, we show that FAIM interacts with both Trk and p75 neurotrophin receptor NGF receptors in a ligand-dependent manner. These results reveal a new function of FAIM in promoting neurite outgrowth by a mechanism involving activation of the Ras–ERK pathway and NF-κB. PMID:15520226

  14. Mechanical tension and electrical conductivity of liquid crystal filaments

    NASA Astrophysics Data System (ADS)

    Kress, Oliver H.

    During the NSF funded IRES internship at the Otto-von-Geuricke Univeristy in Magdeburg, Germany, I studied the optical properties and mechanical behavior in the form of line tension of bent-core liquid crystal fiber bundles and verified previously published tension values and temperature dependent behavior. Then, carbon nanotubes were added and it as found that the tension in the fibers decreased by a factor of two instead of increasing as was hoped. A new device for pulling fibers and measuring tension by deflection due to the adhesion of glass beads was built at the LCI. The device was meant to improve upon the device used at O.v.G. Improvements included a smaller heating chamber with better insulation, temperature control, large viewing windows, more stable mounting interface, easier disassembly and the option to quickly modify the device in order to perform a variety of other experiments such as observing behavior due to acoustic driving (based on previous literature), observing optical behavior under a polarizing microscope and introducing probes to measure the electrical properties of fibers. The platform remains modular and makes the addition of new components for carrying out new experiments very simple and straightforward. The addition of carbon nanotubes has scattered results regarding the modulation of fiber tension. It seems that the addition of CNTs to BLC1571 may slightly be decreasing tension while the addition to BLC1688 may be increasing it. In both mesogens, 10wt% CNT yielded the highest tension value above the theoretical surface tension contribution. A reversal of temperature dependence was observed for fibers containing CNT; their tension increased with temperature instead of decreased. A driving rod attached to a speaker was used to acoustically drive a filament of pure BLC1571 in an attempt to replicate the tension values in a different way. The movement of the fiber and the driving rod were captured using a high-speed camera and MATLAB code

  15. Sensing bilayer tension: bacterial mechanosensitive channels and their gating mechanisms.

    PubMed

    Booth, Ian R; Rasmussen, Tim; Edwards, Michelle D; Black, Susan; Rasmussen, Akiko; Bartlett, Wendy; Miller, Samantha

    2011-06-01

    Mechanosensitive channels sense and respond to changes in bilayer tension. In many respects, this is a unique property: the changes in membrane tension gate the channel, leading to the transient formation of open non-selective pores. Pore diameter is also high for the bacterial channels studied, MscS and MscL. Consequently, in cells, gating has severe consequences for energetics and homoeostasis, since membrane depolarization and modification of cytoplasmic ionic composition is an immediate consequence. Protection against disruption of cellular integrity, which is the function of the major channels, provides a strong evolutionary rationale for possession of such disruptive channels. The elegant crystal structures for these channels has opened the way to detailed investigations that combine molecular genetics with electrophysiology and studies of cellular behaviour. In the present article, the focus is primarily on the structure of MscS, the small mechanosensitive channel. The description of the structure is accompanied by discussion of the major sites of channel-lipid interaction and reasoned, but limited, speculation on the potential mechanisms of tension sensing leading to gating.

  16. Elastocapillarity: Surface Tension and the Mechanics of Soft Solids

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Jagota, Anand; Hui, Chung-Yuen; Dufresne, Eric R.

    2017-03-01

    It is widely appreciated that surface tension can dominate the behavior of liquids at small scales. Solids also have surface stresses of a similar magnitude, but they are usually overlooked. However, recent work has shown that these can play a central role in the mechanics of soft solids such as gels. Here, we review this emerging field. We outline the theory of surface stresses, from both mechanical and thermodynamic perspectives, emphasizing the relationship between surface stress and surface energy. We describe a wide range of phenomena at interfaces and contact lines where surface stresses play an important role. We highlight how surface stresses cause dramatic departures from classic theories for wetting (Young-Dupré), adhesion (Johnson-Kendall-Roberts), and composites (Eshelby). A common thread is the importance of the ratio of surface stress to an elastic modulus, which defines a length scale below which surface stresses can dominate.

  17. Biaxial mechanical properties of human ureter under tension.

    PubMed

    Rassoli, Aisa; Shafigh, Mohammad; Seddighi, Amirsaeed; Seddighi, Afsoun; Daneshparvar, Hamidreza; Fatouraee, Nasser

    2014-07-08

    The Mechanical properties of the ureteral wall may be altered by certain diseases such as megaureter. Ureter compliance and wall tension alterations can occur, leading to some abnormalities such as reflex mechanisms. Familiarizing with the mechanical properties of the ureter can help us advance in the understanding of urinary tract diseases. A constitutive model that can predict the mechanical response of ureteral tissue under complex mechanical loading is required. Parameters characterizing the mechanical behaviour of the material were estimated from planar biaxial test data, where human ureter specimens were simultaneously loaded along the longitudinal and circumferential directions. The biaxial stress-stretch curve was plotted and fitted to a hyperelastic four-parameter Fung type model and five-parameter Mooney-Rivlin model. The average strength in the longitudinal direction was 3.48 ± 0.47 MPa and 2.31 ± 0.46 MPa (P <.05) for the circumferential direction.In the Fung model the value of parameter a2 (0.699 ± 0.17) was higher than a1 (0.279 ± 0.07), which may be due to the collagen fiber orientation's preference along the longitudinal axis. According to this study, it seems that ureter tissue is stiffer in the longitudinal than in the circumferential direction and maybe the collagen fiber are along the axial axes. Also the specimens showed some degree of anisotropy.

  18. Liquid drops and surface tension with smoothed particle applied mechanics

    NASA Astrophysics Data System (ADS)

    Nugent, S.; Posch, H. A.

    2000-10-01

    Smoothed particle applied mechanics (SPAM), also referred to as smoothed particle hydrodynamics, is a Lagrangian particle method for the simulation of continuous flows. Here we apply it to the formation of a liquid drop, surrounded by its vapor, for a van der Waals (vdW) fluid in two dimensions. The cohesive pressure of the vdW equation of state gives rise to an attractive, central force between the particles with an interaction range which is assumed to exceed the interaction range of all the other smoothed forces in the SPAM equations of motion. With this assumption, stable drops are formed, and the vdW phase diagram is well reproduced by the simulations. Below the critical temperature, the surface tension for equilibrated drops may be computed from the pressure excess in their centers. It agrees very well with the surface tension independently determined from the vibrational frequency of weakly excited drops. We also study strongly deformed drops performing large-amplitude oscillations, which are reminiscent of the oscillations of a large ball of water under microgravity conditions. In an appendix we comment on the limitations of SPAM by studying the violation of angular momentum conservation, which is a consequence of noncentral forces contributed by the full Newtonian viscous stress tensor.

  19. Mechanisms underlying the initiation and dynamics of neuronal filopodia: from neurite formation to synaptogenesis.

    PubMed

    Gallo, Gianluca

    2013-01-01

    Filopodia are finger-like cellular protrusions found throughout the metazoan kingdom and perform fundamental cellular functions during development and cell migration. Neurons exhibit a wide variety of extremely complex morphologies. In the nervous system, filopodia underlie many major morphogenetic events. Filopodia have roles spanning the initiation and guidance of neuronal processes, axons and dendrites to the formation of synaptic connections. This chapter addresses the mechanisms of the formation and dynamics of neuronal filopodia. Some of the major lessons learned from the study of neuronal filopodia are (1) there are multiple mechanisms that can regulate filopodia in a context-dependent manner, (2) that filopodia are specialized subcellular domains, (3) that filopodia exhibit dynamic membrane recycling which also controls aspects of filopodial dynamics, (4) that neuronal filopodia contain machinery for the orchestration of the actin and microtubule cytoskeleton, and (5) localized protein synthesis contributes to neuronal filopodial dynamics. Copyright © 2013 Elsevier Inc. All rights reserved.

  20. Rapid cable tension estimation using dynamic and mechanical properties

    NASA Astrophysics Data System (ADS)

    Martínez-Castro, Rosana E.; Jang, Shinae; Christenson, Richard E.

    2016-04-01

    Main tension elements are critical to the overall stability of cable-supported bridges. A dependable and rapid determination of cable tension is desired to assess the state of a cable-supported bridge and evaluate its operability. A portable smart sensor setup is presented to reduce post-processing time and deployment complexity while reliably determining cable tension using dynamic characteristics extracted from spectral analysis. A self-recording accelerometer is coupled with a single-board microcomputer that communicates wirelessly with a remote host computer. The portable smart sensing device is designed such that additional algorithms, sensors and controlling devices for various monitoring applications can be installed and operated for additional structural assessment. The tension-estimating algorithms are based on taut string theory and expand to consider bending stiffness. The successful combination of cable properties allows the use of a cable's dynamic behavior to determine tension force. The tension-estimating algorithms are experimentally validated on a through-arch steel bridge subject to ambient vibration induced by passing traffic. The tension estimation is determined in well agreement with previously determined tension values for the structure.

  1. Nerve growth factor (NGF) and pro-NGF increase low-density lipoprotein (LDL) receptors in neuronal cells partly by different mechanisms: role of LDL in neurite outgrowth.

    PubMed

    Do, Hai Thi; Bruelle, Céline; Pham, Dan Duc; Jauhiainen, Matti; Eriksson, Ove; Korhonen, Laura T; Lindholm, Dan

    2016-01-01

    Low-density lipoprotein receptors (LDLRs) mediate the uptake of lipoprotein particles into cells, as studied mainly in peripheral tissues. Here, we show that nerve growth factor (NGF) increases LDLR levels in PC6.3 cells and in cultured septal neurons from embryonic rat brain. Study of the mechanisms showed that NGF enhanced transcription of the LDLR gene, acting mainly via Tropomyosin receptor kinase A receptors. Simvastatin, a cholesterol-lowering drug, also increased the LDLR expression in PC6.3 cells. In addition, pro-NGF and pro-brain-derived neurotrophic factor, acting via the p75 neurotrophin receptor (p75NTR) also increased LDLRs. We further observed that Myosin Regulatory Light Chain-Interacting Protein/Inducible Degrader of the LDLR (Mylip/Idol) was down-regulated by pro-NGF, whereas the other LDLR regulator, proprotein convertase subtilisin kexin 9 (PCSK9) was not significantly changed. On the functional side, NGF and pro-NGF increased lipoprotein uptake by neuronal cells as shown using diacetyl-labeled LDL. The addition of serum-derived lipoprotein particles in conjunction with NGF or simvastatin enhanced neurite outgrowth. Collectively, these results show that NGF and simvastatin are able to stimulate lipoprotein uptake by neurons with a positive effect on neurite outgrowth. Increases in LDLRs and lipoprotein particles in neurons could play a functional role during brain development, in neuroregeneration and after brain injuries. Nerve growth factor (NGF) and pro-NGF induce the expression of low-density lipoprotein receptors (LDLRs) in neuronal cells leading to increased LDLR levels. Pro-NGF also down-regulated myosin regulatory light chain-interacting protein/inducible degrader of the LDLR (Mylip/Idol) that is involved in the degradation of LDLRs. NGF acts mainly via Tropomyosin receptor kinase A (TrkA) receptors, whereas pro-NGF stimulates p75 neurotrophin receptor (p75NTR). Elevated LDLRs upon NGF and pro-NGF treatments enhanced lipoprotein uptake

  2. Molecular mechanism for cavitation in water under tension.

    PubMed

    Menzl, Georg; Gonzalez, Miguel A; Geiger, Philipp; Caupin, Frédéric; Abascal, José L F; Valeriani, Chantal; Dellago, Christoph

    2016-11-29

    Despite its relevance in biology and engineering, the molecular mechanism driving cavitation in water remains unknown. Using computer simulations, we investigate the structure and dynamics of vapor bubbles emerging from metastable water at negative pressures. We find that in the early stages of cavitation, bubbles are irregularly shaped and become more spherical as they grow. Nevertheless, the free energy of bubble formation can be perfectly reproduced in the framework of classical nucleation theory (CNT) if the curvature dependence of the surface tension is taken into account. Comparison of the observed bubble dynamics to the predictions of the macroscopic Rayleigh-Plesset (RP) equation, augmented with thermal fluctuations, demonstrates that the growth of nanoscale bubbles is governed by viscous forces. Combining the dynamical prefactor determined from the RP equation with CNT based on the Kramers formalism yields an analytical expression for the cavitation rate that reproduces the simulation results very well over a wide range of pressures. Furthermore, our theoretical predictions are in excellent agreement with cavitation rates obtained from inclusion experiments. This suggests that homogeneous nucleation is observed in inclusions, whereas only heterogeneous nucleation on impurities or defects occurs in other experiments.

  3. Molecular mechanism for cavitation in water under tension

    PubMed Central

    Menzl, Georg; Gonzalez, Miguel A.; Geiger, Philipp; Caupin, Frédéric; Abascal, José L. F.; Dellago, Christoph

    2016-01-01

    Despite its relevance in biology and engineering, the molecular mechanism driving cavitation in water remains unknown. Using computer simulations, we investigate the structure and dynamics of vapor bubbles emerging from metastable water at negative pressures. We find that in the early stages of cavitation, bubbles are irregularly shaped and become more spherical as they grow. Nevertheless, the free energy of bubble formation can be perfectly reproduced in the framework of classical nucleation theory (CNT) if the curvature dependence of the surface tension is taken into account. Comparison of the observed bubble dynamics to the predictions of the macroscopic Rayleigh–Plesset (RP) equation, augmented with thermal fluctuations, demonstrates that the growth of nanoscale bubbles is governed by viscous forces. Combining the dynamical prefactor determined from the RP equation with CNT based on the Kramers formalism yields an analytical expression for the cavitation rate that reproduces the simulation results very well over a wide range of pressures. Furthermore, our theoretical predictions are in excellent agreement with cavitation rates obtained from inclusion experiments. This suggests that homogeneous nucleation is observed in inclusions, whereas only heterogeneous nucleation on impurities or defects occurs in other experiments. PMID:27803329

  4. Actomyosin tension as a determinant of metastatic cancer mechanical tropism.

    PubMed

    McGrail, Daniel J; Kieu, Quang Minh N; Iandoli, Jason A; Dawson, Michelle R

    2015-02-23

    Despite major advances in the characterization of molecular regulators of cancer growth and metastasis, patient survival rates have largely stagnated. Recent studies have shown that mechanical cues from the extracellular matrix can drive the transition to a malignant phenotype. Moreover, it is also known that the metastatic process, which results in over 90% of cancer-related deaths, is governed by intracellular mechanical forces. To better understand these processes, we identified metastatic tumor cells originating from different locations which undergo inverse responses to altered matrix elasticity: MDA-MB-231 breast cancer cells that prefer rigid matrices and SKOV-3 ovarian cancer cells that prefer compliant matrices as characterized by parameters such as tumor cell proliferation, chemoresistance, and migration. Transcriptomic analysis revealed higher expression of genes associated with cytoskeletal tension and contractility in cells that prefer stiff environments, both when comparing MDA-MB-231 to SKOV-3 cells as well as when comparing bone-metastatic to lung-metastatic MDA-MB-231 subclones. Using small molecule inhibitors, we found that blocking the activity of these pathways mitigated rigidity-dependent behavior in both cell lines. Probing the physical forces exerted by cells on the underlying substrates revealed that though force magnitude may not directly correlate with functional outcomes, other parameters such as force polarization do correlate directly with cell motility. Finally, this biophysical analysis demonstrates that intrinsic levels of cell contractility determine the matrix rigidity for maximal cell function, possibly influencing tissue sites for metastatic cancer cell engraftment during dissemination. By increasing our understanding of the physical interactions of cancer cells with their microenvironment, these studies may help develop novel therapeutic strategies.

  5. Actomyosin tension as a determinant of metastatic cancer mechanical tropism

    NASA Astrophysics Data System (ADS)

    McGrail, Daniel J.; Kieu, Quang Minh N.; Iandoli, Jason A.; Dawson, Michelle R.

    2015-04-01

    Despite major advances in the characterization of molecular regulators of cancer growth and metastasis, patient survival rates have largely stagnated. Recent studies have shown that mechanical cues from the extracellular matrix can drive the transition to a malignant phenotype. Moreover, it is also known that the metastatic process, which results in over 90% of cancer-related deaths, is governed by intracellular mechanical forces. To better understand these processes, we identified metastatic tumor cells originating from different locations which undergo inverse responses to altered matrix elasticity: MDA-MB-231 breast cancer cells that prefer rigid matrices and SKOV-3 ovarian cancer cells that prefer compliant matrices as characterized by parameters such as tumor cell proliferation, chemoresistance, and migration. Transcriptomic analysis revealed higher expression of genes associated with cytoskeletal tension and contractility in cells that prefer stiff environments, both when comparing MDA-MB-231 to SKOV-3 cells as well as when comparing bone-metastatic to lung-metastatic MDA-MB-231 subclones. Using small molecule inhibitors, we found that blocking the activity of these pathways mitigated rigidity-dependent behavior in both cell lines. Probing the physical forces exerted by cells on the underlying substrates revealed that though force magnitude may not directly correlate with functional outcomes, other parameters such as force polarization do correlate directly with cell motility. Finally, this biophysical analysis demonstrates that intrinsic levels of cell contractility determine the matrix rigidity for maximal cell function, possibly influencing tissue sites for metastatic cancer cell engraftment during dissemination. By increasing our understanding of the physical interactions of cancer cells with their microenvironment, these studies may help develop novel therapeutic strategies.

  6. Mechanical considerations in using tensioned wires in a transosseous external fixation system.

    PubMed

    Aronson, J; Harp, J H

    1992-07-01

    Factors that affect wire tension were examined using external mechanical testing units as well as in-line load cells. The circular external fixator with wires supported at each end exhibits a self-stiffening effect such that wire stiffness increases with wire deflection. Mechanical slippage between wire and fixation bolt is the primary reason for loss of wire tension. Slippage can be avoided by adequate torque on the fixation nut (20 N.m). Guidelines are presented for proper and safe tensioning techniques to achieve clinically indicated tensions without risk of breakage.

  7. Olfactory ensheathing cell-neurite alignment enhances neurite outgrowth in scar-like cultures

    PubMed Central

    Khankan, Rana R.; Wanner, Ina B.; Phelps, Patricia E.

    2015-01-01

    The regenerative capacity of the adult CNS neurons after injury is strongly inhibited by the spinal cord lesion site environment that is composed primarily of the reactive astroglial scar and invading meningeal fibroblasts. Olfactory ensheathing cell (OEC) transplantation facilitates neuronal survival and functional recovery after a complete spinal cord transection, yet the mechanisms by which this recovery occurs remain unclear. We used a unique multicellular scar-like culture model to test if OECs promote neurite outgrowth in growth inhibitory areas. Astrocytes were mechanically injured and challenged by meningeal fibroblasts to produce key inhibitory elements of a spinal cord lesion. Neurite outgrowth of postnatal cerebral cortical neurons was assessed on three substrates: quiescent astrocyte control cultures, reactive astrocyte scar-like cultures, and scar-like cultures with OECs. Initial results showed that OECs enhanced total neurite outgrowth of cortical neurons in a scar-like environment by 60%. We then asked if the neurite growth-promoting properties of OECs depended on direct alignment between neuronal and OEC processes. Neurites that aligned with OECs were nearly three times longer when they grew on inhibitory meningeal fibroblast areas and twice as long on reactive astrocyte zones compared to neurites not associated with OECs. Our results show that OECs can independently enhance neurite elongation and that direct OEC-neurite cell contact can provide a permissive substrate that overcomes the inhibitory nature of the reactive astrocyte scar border and the fibroblast-rich spinal cord lesion core. PMID:25863021

  8. Tension pneumothorax secondary to automatic mechanical compression decompression device.

    PubMed

    Hutchings, A C; Darcy, K J; Cumberbatch, G L A

    2009-02-01

    The details are presented of the first published case of a tension pneumothorax induced by an automatic compression-decompression (ACD) device during cardiac arrest. An elderly patient collapsed with back pain and, on arrival of the crew, was in pulseless electrical activity (PEA) arrest. He was promptly intubated and correct placement of the endotracheal tube was confirmed by noting equal air entry bilaterally and the ACD device applied. On the way to the hospital he was noted to have absent breath sounds on the left without any change in the position of the endotracheal tube. Needle decompression of the left chest caused a hiss of air but the patient remained in PEA. Intercostal drain insertion in the emergency department released a large quantity of air from his left chest but without any change in his condition. Post-mortem examination revealed a ruptured abdominal aortic aneurysm as the cause of death. Multiple left rib fractures and a left lung laceration secondary to the use of the ACD device were also noted, although the pathologist felt that the tension pneumothorax had not contributed to the patient's death. It is recommended that a simple or tension pneumothorax should be considered when there is unilateral absence of breath sounds in addition to endobronchial intubation if an ACD device is being used.

  9. Mechanical tension contributes to clustering of neurotransmitter vesicles at presynaptic terminals

    PubMed Central

    Siechen, Scott; Yang, Shengyuan; Chiba, Akira; Saif, Taher

    2009-01-01

    Memory and learning in animals are mediated by neurotransmitters that are released from vesicles clustered at the synapse. As a synapse is used more frequently, its neurotransmission efficiency increases, partly because of increased vesicle clustering in the presynaptic neuron. Vesicle clustering has been believed to result primarily from biochemical signaling processes that require the connectivity of the presynaptic terminal with the cell body, the central nervous system, and the postsynaptic cell. Our in vivo experiments on the embryonic Drosophila nervous system show that vesicle clustering at the neuromuscular presynaptic terminal depends on mechanical tension within the axons. Vesicle clustering vanishes upon severing the axon from the cell body, but is restored when mechanical tension is applied to the severed end of the axon. Clustering increases when intact axons are stretched mechanically by pulling the postsynaptic muscle. Using micro mechanical force sensors, we find that embryonic axons that have formed neuromuscular junctions maintain a rest tension of ≈1 nanonewton. If the rest tension is perturbed mechanically, axons restore the rest tension either by relaxing or by contracting over a period of ≈15 min. Our results suggest that neuromuscular synapses employ mechanical tension as a signal to modulate vesicle accumulation and synaptic plasticity. PMID:19620718

  10. Conducting-polymer nanotubes improve electrical properties, mechanical adhesion, neural attachment, and neurite outgrowth of neural electrodes.

    PubMed

    Abidian, Mohammad Reza; Corey, Joseph M; Kipke, Daryl R; Martin, David C

    2010-02-05

    An in vitro comparison of conducting-polymer nanotubes of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(pyrrole) (PPy) and to their film counterparts is reported. Impedance, charge-capacity density (CCD), tendency towards delamination, and neurite outgrowth are compared. For the same deposition charge density, PPy films and nanotubes grow relatively faster vertically, while PEDOT films and nanotubes grow more laterally. For the same deposition charge density (1.44 C cm(-2)), PPy nanotubes and PEDOT nanotubes have lower impedance (19.5 +/- 2.1 kOmega for PPy nanotubes and 2.5 +/- 1.4 kOmega for PEDOT nanotubes at 1 kHz) and higher CCD (184 +/- 5.3 mC cm(-2) for PPy nanotubes and 392 +/- 6.2 mC cm(-2) for PEDOT nanotubes) compared to their film counterparts. However, PEDOT nanotubes decrease the impedance of neural-electrode sites by about two orders of magnitude (bare iridium 468.8 +/- 13.3 kOmega at 1 kHz) and increase capacity of charge density by about three orders of magnitude (bare iridium 0.1 +/- 0.5 mC cm(-2)). During cyclic voltammetry measurements, both PPy and PEDOT nanotubes remain adherent on the surface of the silicon dioxide while PPy and PEDOT films delaminate. In experiments of primary neurons with conducting-polymer nanotubes, cultured dorsal root ganglion explants remain more intact and exhibit longer neurites (1400 +/- 95 microm for PPy nanotubes and 2100 +/- 150 microm for PEDOT nanotubes) than their film counterparts. These findings suggest that conducting-polymer nanotubes may improve the long-term function of neural microelectrodes.

  11. Conducting-Polymer Nanotubes Improve Electrical Properties, Mechanical Adhesion, Neural Attachment, and Neurite Outgrowth of Neural Electrodes

    PubMed Central

    Abidian, Mohammad Reza; Corey, Joseph M.; Kipke, Daryl R.; Martin, David C.

    2011-01-01

    An in vitro comparison of conducting-polymer nanotubes of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(pyrrole) (PPy) and to their film counterparts is reported. Impedance, charge-capacity density (CCD), tendency towards delamination, and neurite outgrowth are compared. For the same deposition charge density, PPy films and nanotubes grow relatively faster vertically, while PEDOT films and nanotubes grow more laterally. For the same deposition charge density (1.44 C cm–2), PPy nanotubes and PEDOT nanotubes have lower impedance (19.5 ± 2.1 kΩ for PPy nanotubes and 2.5 ± 1.4 kΩ for PEDOT nanotubes at 1 kHz) and higher CCD (184 ± 5.3 mC cm–2 for PPy nanotubes and 392 ± 6.2 mC cm–2 for PEDOT nanotubes) compared to their film counterparts. However, PEDOT nanotubes decrease the impedance of neural-electrode sites by about two orders of magnitude (bare iridium 468.8 ± 13.3 kΩ at 1 kHz) and increase capacity of charge density by about three orders of magnitude (bare iridium 0.1 ± 0.5 mC cm–2). During cyclic voltammetry measurements, both PPy and PEDOT nanotubes remain adherent on the surface of the silicon dioxide while PPy and PEDOT films delaminate. In experiments of primary neurons with conducting-polymer nanotubes, cultured dorsal root ganglion explants remain more intact and exhibit longer neurites (1400 ± 95 μm for PPy nanotubes and 2100 ± 150 μm for PEDOT nanotubes) than their film counterparts. These findings suggest that conducting-polymer nanotubes may improve the long-term function of neural microelectrodes. PMID:20077424

  12. Lighting Up the Force: Investigating Mechanisms of Mechanotransduction Using Fluorescent Tension Probes

    PubMed Central

    Jurchenko, Carol

    2015-01-01

    The ability of cells to sense the physical nature of their surroundings is critical to the survival of multicellular organisms. Cellular response to physical cues from adjacent cells and the extracellular matrix leads to a dynamic cycle in which cells respond by remodeling their local microenvironment, fine-tuning cell stiffness, polarity, and shape. Mechanical regulation is important in cellular development, normal morphogenesis, and wound healing. The mechanisms by which these finely balanced mechanotransduction events occur, however, are not well understood. In large part, this is due to the limited availability of tools to study molecular mechanotransduction events in live cells. Several classes of molecular tension probes have been recently developed which are rapidly transforming the study of mechanotransduction. Molecular tension probes are primarily based on fluorescence resonance energy transfer (FRET) and report on piconewton scale tension events in live cells. In this minireview, we describe the two main classes of tension probes, genetically encoded tension sensors and immobilized tension sensors, and discuss the advantages and limitations of each type. We discuss future opportunities to address major biological questions and outline the challenges facing the next generation of molecular tension probes. PMID:26031334

  13. Joining mechanism with stem tension and interlocked compression ring

    DOEpatents

    James, Allister W.; Morrison, Jay A.

    2012-09-04

    A stem (34) extends from a second part (30) through a hole (28) in a first part (22). A groove (38) around the stem provides a non-threaded contact surface (42) for a ring element (44) around the stem. The ring element exerts an inward force against the non-threaded contact surface at an angle that creates axial tension (T) in the stem, pulling the second part against the first part. The ring element is formed of a material that shrinks relative to the stem by sintering. The ring element may include a split collet (44C) that fits partly into the groove, and a compression ring (44E) around the collet. The non-threaded contact surface and a mating distal surface (48) of the ring element may have conic geometries (64). After shrinkage, the ring element is locked onto the stem.

  14. Orexin A Inhibits Propofol-Induced Neurite Retraction by a Phospholipase D/Protein Kinase Cε-Dependent Mechanism in Neurons

    PubMed Central

    Björnström, Karin; Turina, Dean; Strid, Tobias; Sundqvist, Tommy; Eintrei, Christina

    2014-01-01

    Background The intravenous anaesthetic propofol retracts neurites and reverses the transport of vesicles in rat cortical neurons. Orexin A (OA) is an endogenous neuropeptide regulating wakefulness and may counterbalance anaesthesia. We aim to investigate if OA interacts with anaesthetics by inhibition of the propofol-induced neurite retraction. Methods In primary cortical cell cultures from newborn rats’ brains, live cell light microscopy was used to measure neurite retraction after propofol (2 µM) treatment with or without OA (10 nM) application. The intracellular signalling involved was tested using a protein kinase C (PKC) activator [phorbol 12-myristate 13-acetate (PMA)] and inhibitors of Rho-kinase (HA-1077), phospholipase D (PLD) [5-fluoro-2-indolyl des-chlorohalopemide (FIPI)], PKC (staurosporine), and a PKCε translocation inhibitor peptide. Changes in PKCε Ser729 phosphorylation were detected with Western blot. Results The neurite retraction induced by propofol is blocked by Rho-kinase and PMA. OA blocks neurite retraction induced by propofol, and this inhibitory effect could be prevented by FIPI, staurosporine and PKCε translocation inhibitor peptide. OA increases via PLD and propofol decreases PKCε Ser729 phosphorylation, a crucial step in the activation of PKCε. Conclusions Rho-kinase is essential for propofol-induced neurite retraction in cortical neuronal cells. Activation of PKC inhibits neurite retraction caused by propofol. OA blocks propofol-induced neurite retraction by a PLD/PKCε-mediated pathway, and PKCε maybe the key enzyme where the wakefulness and anaesthesia signal pathways converge. PMID:24828410

  15. Influence of Tension Leveling Parameters on the Microstructure and Mechanical Properties of Steel Strip

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Zhou, C. L.; Li, H. B.; Zhang, X. C.; Li, M.

    2017-02-01

    We describe the effect of varying tension leveling parameters on the microstructure and mechanical properties of steel strips. We found that, when the tension leveling elongation was constant, an increase in the screw-down value resulted in an initial decrease in the cross-sectional grain size of the strip, which was followed by an increase. However, the longitudinal grain size remained constant, and the yield strength and tensile strength increased gradually. In addition, with a constant screw-down value, an increase in tension leveling elongation resulted in refining of the cross-sectional grain size, elongation of the longitudinal grain size, and small increases in both yield and tensile strength. This study therefore provides an insight into the optimal configuration of tension leveling parameters to improve steel strip properties.

  16. Mechano-adaptive sensory mechanism of α-catenin under tension

    NASA Astrophysics Data System (ADS)

    Maki, Koichiro; Han, Sung-Woong; Hirano, Yoshinori; Yonemura, Shigenobu; Hakoshima, Toshio; Adachi, Taiji

    2016-04-01

    The contractile forces in individual cells drive the tissue processes, such as morphogenesis and wound healing, and maintain tissue integrity. In these processes, α-catenin molecule acts as a tension sensor at cadherin-based adherens junctions (AJs), accelerating the positive feedback of intercellular tension. Under tension, α-catenin is activated to recruit vinculin, which recruits actin filaments to AJs. In this study, we revealed how α-catenin retains its activated state while avoiding unfolding under tension. Using single-molecule force spectroscopy employing atomic force microscopy (AFM), we found that mechanically activated α-catenin fragment had higher mechanical stability than a non-activated fragment. The results of our experiments using mutated and segmented fragments showed that the key intramolecular interactions acted as a conformational switch. We also found that the conformation of α-catenin was reinforced by vinculin binding. We demonstrate that α-catenin adaptively changes its conformation under tension to a stable intermediate state, binds to vinculin, and finally settles into a more stable state reinforced by vinculin binding. Our data suggest that the plastic characteristics of α-catenin, revealed in response to both mechanical and biochemical cues, enable the functional-structural dynamics at the cellular and tissue levels.

  17. Mechano-adaptive sensory mechanism of α-catenin under tension

    PubMed Central

    Maki, Koichiro; Han, Sung-Woong; Hirano, Yoshinori; Yonemura, Shigenobu; Hakoshima, Toshio; Adachi, Taiji

    2016-01-01

    The contractile forces in individual cells drive the tissue processes, such as morphogenesis and wound healing, and maintain tissue integrity. In these processes, α-catenin molecule acts as a tension sensor at cadherin-based adherens junctions (AJs), accelerating the positive feedback of intercellular tension. Under tension, α-catenin is activated to recruit vinculin, which recruits actin filaments to AJs. In this study, we revealed how α-catenin retains its activated state while avoiding unfolding under tension. Using single-molecule force spectroscopy employing atomic force microscopy (AFM), we found that mechanically activated α-catenin fragment had higher mechanical stability than a non-activated fragment. The results of our experiments using mutated and segmented fragments showed that the key intramolecular interactions acted as a conformational switch. We also found that the conformation of α-catenin was reinforced by vinculin binding. We demonstrate that α-catenin adaptively changes its conformation under tension to a stable intermediate state, binds to vinculin, and finally settles into a more stable state reinforced by vinculin binding. Our data suggest that the plastic characteristics of α-catenin, revealed in response to both mechanical and biochemical cues, enable the functional-structural dynamics at the cellular and tissue levels. PMID:27109499

  18. Skeletal muscle is sensitive to the tension-time integral but not to the rate of change of tension, as assessed by mechanically induced signaling.

    PubMed

    Martineau, Louis C; Gardiner, Phillip F

    2002-05-01

    Mechanical forces regulate many cellular processes. Mechanotransduction, however, is poorly understood. In skeletal muscle, mechanical forces have a major impact on the regulation of cellular volume, yet the nature of the mechanical stimulation to which muscle is most sensitive is unknown. It was recently demonstrated that activation of the mechanically-sensitive kinase p54 jun-N-terminal-kinase (JNK), is a quantitative marker of mechanical stimulation in skeletal muscle. This marker was shown to be more sensitive to peak tension than to other tension-related parameters such as the tension-time integral (TTI) and the rate of change of tension (dT/dt). The purpose of the present study was to parcel out the contribution of TTI and dT/dt to mechanical stimulation of muscle under conditions of constant peak tension. The rat medial gastrocnemius in situ was subjected to one of four 5-min passive stretch protocols consisting of equal length excursions, but differing in displacement-time integral (4%, 40%, or 100%) and/or rate of stretch (0, 3, or 30 mm/s), and the resulting p54-JNK phosphorylation was assessed. A linear relationship between TTI and p54-JNK signaling was observed. However, no effect of dT/dt was observed. It is concluded that peak tension and TTI are necessary parameters for modeling the mechanical stimulus-response of muscle. Additionally, the mechanism of mechanotransduction is sensitive to peak tension and TTI, but not to dT/dt, and thus exhibits spring-like behavior. These findings may contribute to the refinement of disuse atrophy countermeasures.

  19. Ten years of tension: single-molecule DNA mechanics.

    PubMed

    Bustamante, Carlos; Bryant, Zev; Smith, Steven B

    2003-01-23

    The basic features of DNA were elucidated during the half-century following the discovery of the double helix. But it is only during the past decade that researchers have been able to manipulate single molecules of DNA to make direct measurements of its mechanical properties. These studies have illuminated the nature of interactions between DNA and proteins, the constraints within which the cellular machinery operates, and the forces created by DNA-dependent motors.

  20. Sensing Viruses by Mechanical Tension of DNA in Responsive Hydrogels

    NASA Astrophysics Data System (ADS)

    Shin, Jaeoh; Cherstvy, Andrey G.; Metzler, Ralf

    2014-04-01

    The rapid worldwide spread of severe viral infections, often involving novel mutations of viruses, poses major challenges to our health-care systems. This means that tools that can efficiently and specifically diagnose viruses are much needed. To be relevant for broad applications in local health-care centers, such tools should be relatively cheap and easy to use. In this paper, we discuss the biophysical potential for the macroscopic detection of viruses based on the induction of a mechanical stress in a bundle of prestretched DNA molecules upon binding of viruses to the DNA. We show that the affinity of the DNA to the charged virus surface induces a local melting of the double helix into two single-stranded DNA. This process effects a mechanical stress along the DNA chains leading to an overall contraction of the DNA. Our results suggest that when such DNA bundles are incorporated in a supporting matrix such as a responsive hydrogel, the presence of viruses may indeed lead to a significant, macroscopic mechanical deformation of the matrix. We discuss the biophysical basis for this effect and characterize the physical properties of the associated DNA melting transition. In particular, we reveal several scaling relations between the relevant physical parameters of the system. We promote this DNA-based assay as a possible tool for efficient and specific virus screening.

  1. Mechanisms underlying rhythmic locomotion: interactions between activation, tension and body curvature waves.

    PubMed

    Chen, Jun; Friesen, W Otto; Iwasaki, Tetsuya

    2012-01-15

    Undulatory animal locomotion arises from three closely related propagating waves that sweep rostrocaudally along the body: activation of segmental muscles by motoneurons (MNs), strain of the body wall, and muscle tension induced by activation and strain. Neuromechanical models that predict the relative propagation speeds of neural/muscle activation, muscle tension and body curvature can reveal crucial underlying control features of the central nervous system and the power-generating mechanisms of the muscle. We provide an analytical explanation of the relative speeds of these three waves based on a model of neuromuscular activation and a model of the body-fluid interactions for leech anguilliform-like swimming. First, we deduced the motoneuron spike frequencies that activate the muscle and the resulting muscle tension during swimming in intact leeches from muscle bending moments. Muscle bending moments were derived from our video-recorded kinematic motion data by our body-fluid interaction model. The phase relationships of neural activation and muscle tension in the strain cycle were then calculated. Our study predicts that the MN activation and body curvature waves have roughly the same speed (the ratio of curvature to MN activation speed ≈0.84), whereas the tension wave travels about twice as fast. The high speed of the tension wave resulting from slow MN activation is explained by the multiplicative effects of MN activation and muscle strain on tension development. That is, the product of two slower waves (activation and strain) with appropriate amplitude, bias and phase can generate a tension wave with twice the propagation speed of the factors. Our study predicts that (1) the bending moment required for swimming is achieved by minimal MN spike frequency, rather than by minimal muscle tension; (2) MN activity is greater in the mid-body than in the head and tail regions; (3) inhibitory MNs not only accelerate the muscle relaxation but also reduce the intrinsic

  2. Mechanisms underlying rhythmic locomotion: interactions between activation, tension and body curvature waves

    PubMed Central

    Chen, Jun; Friesen, W. Otto; Iwasaki, Tetsuya

    2012-01-01

    SUMMARY Undulatory animal locomotion arises from three closely related propagating waves that sweep rostrocaudally along the body: activation of segmental muscles by motoneurons (MNs), strain of the body wall, and muscle tension induced by activation and strain. Neuromechanical models that predict the relative propagation speeds of neural/muscle activation, muscle tension and body curvature can reveal crucial underlying control features of the central nervous system and the power-generating mechanisms of the muscle. We provide an analytical explanation of the relative speeds of these three waves based on a model of neuromuscular activation and a model of the body–fluid interactions for leech anguilliform-like swimming. First, we deduced the motoneuron spike frequencies that activate the muscle and the resulting muscle tension during swimming in intact leeches from muscle bending moments. Muscle bending moments were derived from our video-recorded kinematic motion data by our body–fluid interaction model. The phase relationships of neural activation and muscle tension in the strain cycle were then calculated. Our study predicts that the MN activation and body curvature waves have roughly the same speed (the ratio of curvature to MN activation speed ≈0.84), whereas the tension wave travels about twice as fast. The high speed of the tension wave resulting from slow MN activation is explained by the multiplicative effects of MN activation and muscle strain on tension development. That is, the product of two slower waves (activation and strain) with appropriate amplitude, bias and phase can generate a tension wave with twice the propagation speed of the factors. Our study predicts that (1) the bending moment required for swimming is achieved by minimal MN spike frequency, rather than by minimal muscle tension; (2) MN activity is greater in the mid-body than in the head and tail regions; (3) inhibitory MNs not only accelerate the muscle relaxation but also reduce

  3. Laminar stream of detergents for subcellular neurite damage in a microfluidic device: a simple tool for the study of neuroregeneration

    NASA Astrophysics Data System (ADS)

    Lee, Chang Young; Romanova, Elena V.; Sweedler, Jonathan V.

    2013-06-01

    Objective. The regeneration and repair of damaged neuronal networks is a difficult process to study in vivo, leading to the development of multiple in vitro models and techniques for studying nerve injury. Here we describe an approach for generating a well-defined subcellular neurite injury in a microfluidic device. Approach. A defined laminar stream of sodium dodecyl sulfate (SDS) was used to damage selected portions of neurites of individual neurons. The somata and neurites unaffected by the SDS stream remained viable, thereby enabling the study of neuronal regeneration. Main results. By using well-characterized neurons from Aplysia californica cultured in vitro, we demonstrate that our approach is useful in creating neurite damage, investigating neurotrophic factors, and monitoring somata migration during regeneration. Supplementing the culture medium with acetylcholinesterase (AChE) or Aplysia hemolymph facilitated the regeneration of the peptidergic Aplysia neurons within 72 h, with longer (p < 0.05) and more branched (p < 0.05) neurites than in the control medium. After the neurons were transected, their somata migrated; intriguingly, for the control cultures, the migration direction was always away from the injury site (7/7). In the supplemented cultures, the number decreased to 6/8 in AChE and 4/8 in hemolymph, with reduced migration distances in both cases. Significance. The SDS transection approach is simple and inexpensive, yet provides flexibility in studying neuroregeneration, particularly when it is important to make sure there are no retrograde signals from the distal segments affecting regeneration. Neurons are known to not only be under tension but also balanced in terms of force, and the balance is obviously disrupted by transection. Our experimental platform, verified with Aplysia, can be extended to mammalian systems, and help us gain insight into the role that neurotrophic factors and mechanical tension play during neuronal regeneration.

  4. The role of calsyntenin-3 in dystrophic neurite formation in Alzheimer's disease brain.

    PubMed

    Uchida, Yoko; Gomi, Fujiya

    2016-03-01

    β-Amyloid (Aβ) oligomers may play an important role in the early pathogenesis of Alzheimer's disease: cognitive impairment caused by synaptic dysfunction. Dystrophic neurites surrounding Aβ plaques, another pathological feature of Alzheimer's disease, are plaque-associated neuritic alterations preceding the appearance of synaptic loss. In the present review, we focus on the mechanism of dystrophic neurite formation by Aß oligomers, and discuss the neurotoxic role of Aβ-induced calsyntenin-3 in mediating dystrophic neurite formation.

  5. h2-Calponin is regulated by mechanical tension and modifies the function of actin cytoskeleton.

    PubMed

    Hossain, M Moazzem; Crish, James F; Eckert, Richard L; Lin, Jim J-C; Jin, Jian-Ping

    2005-12-23

    Calponin is an extensively studied actin-binding protein, but its function is not well understood. Among three isoforms of calponin, h2-calponin is found in both smooth muscle and non-muscle cells. The present study demonstrates that epidermal keratinocytes and fibroblast cells express significant amounts of h2-calponin. The expression of h2-calponin is cell anchorage-dependent. The levels of h2-calponin decrease when cells are rounded up and remain low when cells are prevented from adherence to a culture dish. h2-calponin expression resumes after the floating cells are allowed to form a monolayer in plastic dish. Cell cultures on polyacrylamide gels of different stiffness demonstrated that h2-calponin expression is affected by the mechanical properties of the culture matrix. When cells are cultured on soft gel that applies less traction force to the cell and, therefore, lower mechanical tension in the cytoskeleton, the level of h2-calponin is significantly lower than that in cells cultured on hard gel or rigid plastic dish. Force-expression of h2-calponin enhanced the resistance of the actin filaments to cytochalasin B treatment. Keratinocyte differentiation is accompanied by a mechanical tension-related up-regulation of h2-calponin. Lowering the tension of actin cytoskeleton by inhibiting non-muscle myosin II ATPase decreased h2-calponin expression. In contrast to the mechanical tension regulation of endogenous h2-calponin, the expression of h2-calponin using a cytomegalovirus promotor was independent of the stiffness of culture matrix. The results suggest that h2-calponin represents a novel manifestation of mechanical tension responsive gene regulation that may modify cytoskeleton function.

  6. Control of cytoskeletal mechanics by extracellular matrix, cell shape, and mechanical tension

    NASA Technical Reports Server (NTRS)

    Wang, N.; Ingber, D. E.

    1994-01-01

    We have investigated how extracellular matrix (ECM) alters the mechanical properties of the cytoskeleton (CSK). Mechanical stresses were applied to integrin receptors on the apical surfaces of adherent endothelial cells using RGD-coated ferromagnetic microbeads (5.5-microns diameter) in conjunction with a magnetic twisting device. Increasing the number of basal cell-ECM contacts by raising the fibronectin (FN) coating density from 10 to 500 ng/cm2 promoted cell spreading by fivefold and increased CSK stiffness, apparent viscosity, and permanent deformation all by more than twofold, as measured in response to maximal stress (40 dyne/cm2). When the applied stress was increased from 7 to 40 dyne/cm2, the stiffness and apparent viscosity of the CSK increased in parallel, although cell shape, ECM contacts, nor permanent deformation was altered. Application of the same stresses over a lower number ECM contacts using smaller beads (1.4-microns diameter) resulted in decreased CSK stiffness and apparent viscosity, confirming that this technique probes into the depth of the CSK and not just the cortical membrane. When magnetic measurements were carried out using cells whose membranes were disrupted and ATP stores depleted using saponin, CSK stiffness and apparent viscosity were found to rise by approximately 20%, whereas permanent deformation decreased by more than half. Addition of ATP (250 microM) under conditions that promote CSK tension generation in membrane-permeabilized cells resulted in decreases in CSK stiffness and apparent viscosity that could be detected within 2 min after ATP addition, before any measurable change in cell size.(ABSTRACT TRUNCATED AT 250 WORDS).

  7. Mechanical tension as a driver of connective tissue growth in vitro.

    PubMed

    Wilson, Cameron J; Pearcy, Mark J; Epari, Devakara R

    2014-07-01

    We propose the progressive mechanical expansion of cell-derived tissue analogues as a novel, growth-based approach to in vitro tissue engineering. The prevailing approach to producing tissue in vitro is to culture cells in an exogenous "scaffold" that provides a basic structure and mechanical support. This necessarily pre-defines the final size of the implantable material, and specific signals must be provided to stimulate appropriate cell growth, differentiation and matrix formation. In contrast, surgical skin expansion, driven by increments of stretch, produces increasing quantities of tissue without trauma or inflammation. This suggests that connective tissue cells have the innate ability to produce growth in response to elevated tension. We posit that this capacity is maintained in vitro, and that order-of-magnitude growth may be similarly attained in self-assembling cultures of cells and their own extracellular matrix. The hypothesis that growth of connective tissue analogues can be induced by mechanical expansion in vitro may be divided into three components: (1) tension stimulates cell proliferation and extracellular matrix synthesis; (2) the corresponding volume increase will relax the tension imparted by a fixed displacement; (3) the repeated application of static stretch will produce sustained growth and a tissue structure adapted to the tensile loading. Connective tissues exist in a state of residual tension, which is actively maintained by resident cells such as fibroblasts. Studies in vitro and in vivo have demonstrated that cellular survival, reproduction, and matrix synthesis and degradation are regulated by the mechanical environment. Order-of-magnitude increases in both bone and skin volume have been achieved clinically through staged expansion protocols, demonstrating that tension-driven growth can be sustained over prolonged periods. Furthermore, cell-derived tissue analogues have demonstrated mechanically advantageous structural adaptation in

  8. Measurement of Mechanical Tension at Cell-cell Junctions Using Two-photon Laser Ablation.

    PubMed

    Liang, Xuan; Michael, Magdalene; Gomez, Guillermo A

    2016-12-20

    The cortical actomyosin cytoskeleton is found in all non-muscle cells where a key function is to control mechanical force (Salbreux et al., 2012). When coupled to E-cadherin cell-cell adhesion, cortical actomyosin generates junctional tension that influences many aspects of tissue function, organization and morphogenesis (Lecuit and Yap, 2015). Uncovering the molecular mechanisms underlying the generation of junctional tension requires tools for measuring it in live cells with a high spatio-temporal resolution. For this, we have set up a technique of laser ablation, in which we use the high power output of a two-photon laser to physically cut the actin cortex at the sites of cell-cell adhesion labeled with E-cadherin-GFP. Tension, thus is visualized as the outwards recoil of the vertices that define a junction after this was ablated/cut. Analysis of recoil versus time allows extracting parameters related to the amount of contractile force that is applied to the junction before ablation (initial recoil) and the ratio between elasticity of the junction and viscosity of the media (cytoplasm) in which the junctional cortex is immersed. Using this approach we have discovered how Src protein-tyrosine kinase (Gomez et al., 2015); actin-binding proteins such as tropomyosins (Caldwell et al., 2014) and N-WASP (Wu et al., 2014); Myosin II (Priya et al., 2015) and coronin-1B (Michael et al., 2016) contribute to the molecular apparatus responsible for generating tension at the cell-cell junctions. This protocol describes the experimental procedure for setting up laser ablation experiments and how to optimize ablation and acquisition conditions for optimal measurements of junctional tension. It also provides a full description, step by step, of the post-acquisition analysis required to evaluate changes in contractile force as well as cell elasticity and/or cytoplasm viscosity.

  9. Measurement of Mechanical Tension at Cell-cell Junctions Using Two-photon Laser Ablation

    PubMed Central

    Liang, Xuan; Michael, Magdalene; Gomez, Guillermo A.

    2017-01-01

    The cortical actomyosin cytoskeleton is found in all non-muscle cells where a key function is to control mechanical force (Salbreux et al., 2012). When coupled to E-cadherin cell-cell adhesion, cortical actomyosin generates junctional tension that influences many aspects of tissue function, organization and morphogenesis (Lecuit and Yap, 2015). Uncovering the molecular mechanisms underlying the generation of junctional tension requires tools for measuring it in live cells with a high spatio-temporal resolution. For this, we have set up a technique of laser ablation, in which we use the high power output of a two-photon laser to physically cut the actin cortex at the sites of cell-cell adhesion labeled with E-cadherin-GFP. Tension, thus is visualized as the outwards recoil of the vertices that define a junction after this was ablated/cut. Analysis of recoil versus time allows extracting parameters related to the amount of contractile force that is applied to the junction before ablation (initial recoil) and the ratio between elasticity of the junction and viscosity of the media (cytoplasm) in which the junctional cortex is immersed. Using this approach we have discovered how Src protein-tyrosine kinase (Gomez et al., 2015); actin-binding proteins such as tropomyosins (Caldwell et al., 2014) and N-WASP (Wu et al., 2014); Myosin II (Priya et al., 2015) and coronin-1B (Michael et al., 2016) contribute to the molecular apparatus responsible for generating tension at the cell-cell junctions. This protocol describes the experimental procedure for setting up laser ablation experiments and how to optimize ablation and acquisition conditions for optimal measurements of junctional tension. It also provides a full description, step by step, of the post-acquisition analysis required to evaluate changes in contractile force as well as cell elasticity and/or cytoplasm viscosity. PMID:28191488

  10. Surface tension and the mechanics of liquid inclusions in compliant solids

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Wettlaufer, John S.; Dufresne, Eric R.

    Eshelby's theory of inclusions has wide-reaching implications across the mechanics of materials and structures including the theories of composites, fracture, and plasticity. However, it does not include the effects of surface stress, which has recently been shown to control many processes in soft materials such as gels, elastomers and biological tissue. To extend Eshelby's theory of inclusions to soft materials, we consider liquid inclusions within an isotropic, compressible, linear-elastic solid. We solve for the displacement and stress fields around individual stretched inclusions, accounting for the bulk elasticity of the solid and the surface tension (\\textit{i.e.} isotropic strain-independent surface stress) of the solid-liquid interface. Surface tension significantly alters the inclusion's shape and stiffness as well as its near- and far-field stress fields. These phenomenon depend strongly on the ratio of inclusion radius, $R$, to an elastocapillary length, $L$. Surface tension is significant whenever inclusions are smaller than $100L$. While Eshelby theory predicts that liquid inclusions generically reduce the stiffness of an elastic solid, our results show that liquid inclusions can actually stiffen a solid when $R<3L/2$. Intriguingly, surface tension cloaks the far-field signature of liquid inclusions when $R=3L/2$. These results are have far-reaching applications from measuring local stresses in biological tissue, to determining the failure strength of soft composites.

  11. Surface tension and the mechanics of liquid inclusions in compliant solids.

    PubMed

    Style, Robert W; Wettlaufer, John S; Dufresne, Eric R

    2015-01-28

    Eshelby's theory of inclusions has wide-reaching implications across the mechanics of materials and structures including the theories of composites, fracture, and plasticity. However, it does not include the effects of surface stress, which has recently been shown to control many processes in soft materials such as gels, elastomers and biological tissue. To extend Eshelby's theory of inclusions to soft materials, we consider liquid inclusions within an isotropic, compressible, linear-elastic solid. We solve for the displacement and stress fields around individual stretched inclusions, accounting for the bulk elasticity of the solid and the surface tension (i.e. isotropic strain-independent surface stress) of the solid-liquid interface. Surface tension significantly alters the inclusion's shape and stiffness as well as its near- and far-field stress fields. These phenomena depend strongly on the ratio of the inclusion radius, R, to an elastocapillary length, L. Surface tension is significant whenever inclusions are smaller than 100L. While Eshelby theory predicts that liquid inclusions generically reduce the stiffness of an elastic solid, our results show that liquid inclusions can actually stiffen a solid when R<3L/2. Intriguingly, surface tension cloaks the far-field signature of liquid inclusions when R=3L/2. These results are have far-reaching applications from measuring local stresses in biological tissue, to determining the failure strength of soft composites.

  12. From membrane tension to channel gating: A principal energy transfer mechanism for mechanosensitive channels.

    PubMed

    Zhang, Xuejun C; Liu, Zhenfeng; Li, Jie

    2016-11-01

    Mechanosensitive (MS) channels are evolutionarily conserved membrane proteins that play essential roles in multiple cellular processes, including sensing mechanical forces and regulating osmotic pressure. Bacterial MscL and MscS are two prototypes of MS channels. Numerous structural studies, in combination with biochemical and cellular data, provide valuable insights into the mechanism of energy transfer from membrane tension to gating of the channel. We discuss these data in a unified two-state model of thermodynamics. In addition, we propose a lipid diffusion-mediated mechanism to explain the adaptation phenomenon of MscS.

  13. Continuum Damage Mechanics Models for the Analysis of Progressive Failure in Open-Hole Tension Laminates

    NASA Technical Reports Server (NTRS)

    Song, Kyonchan; Li, Yingyong; Rose, Cheryl A.

    2011-01-01

    The performance of a state-of-the-art continuum damage mechanics model for interlaminar damage, coupled with a cohesive zone model for delamination is examined for failure prediction of quasi-isotropic open-hole tension laminates. Limitations of continuum representations of intra-ply damage and the effect of mesh orientation on the analysis predictions are discussed. It is shown that accurate prediction of matrix crack paths and stress redistribution after cracking requires a mesh aligned with the fiber orientation. Based on these results, an aligned mesh is proposed for analysis of the open-hole tension specimens consisting of different meshes within the individual plies, such that the element edges are aligned with the ply fiber direction. The modeling approach is assessed by comparison of analysis predictions to experimental data for specimen configurations in which failure is dominated by complex interactions between matrix cracks and delaminations. It is shown that the different failure mechanisms observed in the tests are well predicted. In addition, the modeling approach is demonstrated to predict proper trends in the effect of scaling on strength and failure mechanisms of quasi-isotropic open-hole tension laminates.

  14. Extracellular matrix allows PC12 neurite elongation in the absence of microtubules.

    PubMed

    Lamoureux, P; Steel, V L; Regal, C; Adgate, L; Buxbaum, R E; Heidemann, S R

    1990-01-01

    results by postulating that growth on ECM relieves the need for MTs to serve as compressive supports for neurite tension (Dennerll, T. J., H. C. Joshi, U. L. Steel, R. E. Buxbaum, and S. R. Heidemann. 1988. J. Cell Biol. 107:665). Because compression destabilizes MTs and favors disassembly, this would tend to increase MT assembly relative to other conditions, as we found. Additionally, if MTs are not needed as compressive supports, neurites could grow out in their absence, as we also observed.

  15. Arf6 Guanine Nucleotide Exchange Factor Cytohesin-2 Binds to CCDC120 and Is Transported Along Neurites to Mediate Neurite Growth*

    PubMed Central

    Torii, Tomohiro; Miyamoto, Yuki; Tago, Kenji; Sango, Kazunori; Nakamura, Kazuaki; Sanbe, Atsushi; Tanoue, Akito; Yamauchi, Junji

    2014-01-01

    The mechanism of neurite growth is complicated, involving continuous cytoskeletal rearrangement and vesicular trafficking. Cytohesin-2 is a guanine nucleotide exchange factor for Arf6, an Arf family molecular switch protein, controlling cell morphological changes such as neuritogenesis. Here, we show that cytohesin-2 binds to a protein with a previously unknown function, CCDC120, which contains three coiled-coil domains, and is transported along neurites in differentiating N1E-115 cells. Transfection of the small interfering RNA (siRNA) specific for CCDC120 into cells inhibits neurite growth and Arf6 activation. When neurites start to extend, vesicles containing CCDC120 and cytohesin-2 are transported in an anterograde manner rather than a retrograde one. As neurites continue extension, anterograde vesicle transport decreases. CCDC120 knockdown inhibits cytohesin-2 localization into vesicles containing CCDC120 and diffuses cytohesin-2 in cytoplasmic regions, illustrating that CCDC120 determines cytohesin-2 localization in growing neurites. Reintroduction of the wild type CCDC120 construct into cells transfected with CCDC120 siRNA reverses blunted neurite growth and Arf6 activity, whereas the cytohesin-2-binding CC1 region-deficient CCDC120 construct does not. Thus, cytohesin-2 is transported along neurites by vesicles containing CCDC120, and it mediates neurite growth. These results suggest a mechanism by which guanine nucleotide exchange factor for Arf6 is transported to mediate neurite growth. PMID:25326380

  16. Mechanical response and failure of High Performance Propellant (HPP) subject to uniaxial tension

    NASA Astrophysics Data System (ADS)

    Liu, C.; Thompson, D. G.

    2015-05-01

    As part of a program to characterize and understand the mechanical response and failure behavior of the High Performance Propellant (HPP), uniaxial tensile tests were conducted. The mechanical properties of the HPP solid propellant subject to tension are investigated as a function of both the loading (strain) rate and the temperature. The nominal strain rate varies from 10-6 to 10-2 s-1 and the temperature varies from -50 to 50 °C. Digital image correlation (DIC) technique was used to obtain the full field deformation measurement over the sample surface, from which both the axial strain and the circumferential strain were determined, and as a result, volume changes during the uniaxial tension were studied. Some of the material parameters, e.g., Young's modulus E, the tensile strength σ max, and uniaxial tensile strain at the maximum tensile stress ɛ max, were found to be extremely sensitive to both the strain rate and the temperature. It was also observed that during the linear portion of the uniaxial tension, the HPP is close to incompressible. But when deformation enters the nonlinear regime, volume change of the sample accelerates and such a significant volume increase during the nonlinear portion of the deformation can be attributed to the formation and extension of damage within the gage section, which lead to the macroscopic tearing failure of the material.

  17. Myths and Truths of Nitinol Mechanics: Elasticity and Tension-Compression Asymmetry

    NASA Astrophysics Data System (ADS)

    Bucsek, Ashley N.; Paranjape, Harshad M.; Stebner, Aaron P.

    2016-09-01

    Two prevalent myths of Nitinol mechanics are examined: (1) Martensite is more compliant than austenite; (2) Texture-free Nitinol polycrystals do not exhibit tension-compression asymmetry. By reviewing existing literature, the following truths are revealed: (1) Martensite crystals may be more compliant, equally stiff, or stiffer than austenite crystals, depending on the orientation of the applied load. The Young's Modulus of polycrystalline Nitinol is not a fixed number—it changes with both processing and in operando deformations. Nitinol martensite prefers to behave stiffer under compressive loads and more compliant under tensile loads. (2) Inelastic Nitinol martensite deformation in and of itself is asymmetric, even for texture-free polycrystals. Texture-free Nitinol polycrystals also exhibit tension-compression transformation asymmetry.

  18. Fabrication of Open-Cell Al Foams and Evaluation of their Mechanical Response under Tension

    NASA Astrophysics Data System (ADS)

    Michailidis, N.; Stergioudi, F.; Omar, H.; Tsipas, D. N.

    2010-01-01

    In the present paper a novel procedure for describing the solid geometry of open cell foams is introduced, facilitating the establishment of a corresponding FEM model for simulating the material behaviour in micro-tension. Open-cell Al-foams were fabricated using the polymer impregnating method. A serial sectioning image-based process is described to capture, reproduce and visualize the exact three-dimensional (3D) microstructure of the examined foam. The generated 3D geometry of the Al-foam, derived from the synthesis of digital cross sectional images of the foam, was appropriately adjusted to build a FE model simulating the deformation conditions of the Al-foam under micro-tension loads. The obtained results enabled the visualisation of the stress fields in the Al-foam, allowing for a full investigation of its mechanical behaviour.

  19. Static model of a violin bow: influence of camber and hair tension on mechanical behavior.

    PubMed

    Ablitzer, Frédéric; Dalmont, Jean-Pierre; Dauchez, Nicolas

    2012-01-01

    Experienced bow makers empirically know the influence of wood, tapering, and camber on the playing and tonal qualities of a bow. However, the way each parameter affects the bow mechanical behavior is not clearly established. An in-plane finite element model is developed to highlight the link between the adjustable design parameters and the mechanical behavior of a bow. This model takes into account geometric nonlinearity as well as compliance of the hair. Its validity is discussed from measurements on a bow. Results from simulations are compared to experimental results from previous studies. The consequences of adjusting hair tension and camber are then investigated.

  20. Tension applied through the Dam1 complex promotes microtubule elongation: a direct mechanism for length control in mitosis

    PubMed Central

    Franck, Andrew D.; Powers, Andrew F.; Gestaut, Daniel R.; Gonen, Tamir; Davis, Trisha N.; Asbury, Charles L.

    2009-01-01

    In dividing cells, kinetochores couple chromosomes to the tips of growing and shortening microtubule (MT) fibers1, 2 and tension at the kinetochore-MT interface promotes fiber elongation3-6. Tension-dependent MT fiber elongation is thought to be essential for coordinating chromosome alignment and separation1, 3, 7-10, but the mechanism underlying this effect is unknown. Using optical tweezers, we applied tension to a model of the kinetochore-microtubule interface composed of the yeast Dam1 complex11-13 bound to individual dynamic microtubule tips14. Higher tension decreased the likelihood that growing tips would begin to shorten, slowed shortening, and increased the likelihood that shortening tips would resume growth. These effects are similar to the effects of tension on kinetochore-attached microtubule fibers in many cell types, suggesting that we have reconstituted a direct mechanism for microtubule length control in mitosis. PMID:17572669

  1. Tension applied through the Dam1 complex promotes microtubule elongation providing a direct mechanism for length control in mitosis.

    PubMed

    Franck, Andrew D; Powers, Andrew F; Gestaut, Daniel R; Gonen, Tamir; Davis, Trisha N; Asbury, Charles L

    2007-07-01

    In dividing cells, kinetochores couple chromosomes to the tips of growing and shortening microtubule fibres and tension at the kinetochore-microtubule interface promotes fibre elongation. Tension-dependent microtubule fibre elongation is thought to be essential for coordinating chromosome alignment and separation, but the mechanism underlying this effect is unknown. Using optical tweezers, we applied tension to a model of the kinetochore-microtubule interface composed of the yeast Dam1 complex bound to individual dynamic microtubule tips. Higher tension decreased the likelihood that growing tips would begin to shorten, slowed shortening, and increased the likelihood that shortening tips would resume growth. These effects are similar to the effects of tension on kinetochore-attached microtubule fibres in many cell types, suggesting that we have reconstituted a direct mechanism for microtubule-length control in mitosis.

  2. Reactive oxygen species induce neurite degeneration before induction of cell death

    PubMed Central

    Fukui, Koji

    2016-01-01

    Reactive oxygen species (ROS) induce neuronal cell death in a time- and concentration-dependent manner. Treatment of cultured cells with a low concentration of hydrogen peroxide induces neurite degeneration, but not cell death. Neurites (axons and dendrites) are vulnerable to ROS. Neurite degeneration (shrinkage, accumulation, and fragmentation) has been found in neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease. However, the mechanism of ROS-related neurite degeneration is not fully understood. Many studies have demonstrated the relationship between mitochondrial dysfunction and microtubule destabilization. These dysfunctions are deeply related to changes in calcium homeostasis and ROS production in neurites. Treatment with antioxidant substances, such as vitamin E, prevents neurite degeneration in cultured cells. This review describes the possibility that ROS induces neurite degeneration before the induction of cell death. PMID:27895381

  3. Sonic Hedgehog Promotes Neurite Outgrowth of Primary Cortical Neurons Through Up-Regulating BDNF Expression.

    PubMed

    He, Weiliang; Cui, Lili; Zhang, Cong; Zhang, Xiangjian; He, Junna; Xie, Yanzhao

    2016-04-01

    Sonic hedgehog (Shh), a secreted glycoprotein factor, can activate the Shh pathway, which has been implicated in neuronal polarization involving neurite outgrowth. However, little evidence is available about the effect of Shh on neurite outgrowth in primary cortical neurons and its potential mechanism. Here, we revealed that Shh increased neurite outgrowth in primary cortical neurons, while the Shh pathway inhibitor (cyclopamine, CPM) partially suppressed Shh-induced neurite outgrowth. Similar results were found for the expressions of Shh and Patched genes in Shh-induced primary cortical neurons. Moreover, Shh increased the levels of brain-derived neurotrophic factor (BDNF) not only in lysates and in culture medium but also in the longest neurites of primary cortical neurons, which was partially blocked by CPM. In addition, blocking of BDNF action suppressed Shh-mediated neurite elongation in primary cortical neurons. In conclusion, these findings suggest that Shh promotes neurite outgrowth in primary cortical neurons at least partially through modulating BDNF expression.

  4. Determining Tension-Compression Nonlinear Mechanical Properties of Articular Cartilage from Indentation Testing.

    PubMed

    Chen, Xingyu; Zhou, Yilu; Wang, Liyun; Santare, Michael H; Wan, Leo Q; Lu, X Lucas

    2016-04-01

    The indentation test is widely used to determine the in situ biomechanical properties of articular cartilage. The mechanical parameters estimated from the test depend on the constitutive model adopted to analyze the data. Similar to most connective tissues, the solid matrix of cartilage displays different mechanical properties under tension and compression, termed tension-compression nonlinearity (TCN). In this study, cartilage was modeled as a porous elastic material with either a conewise linear elastic matrix with cubic symmetry or a solid matrix reinforced by a continuous fiber distribution. Both models are commonly used to describe the TCN of cartilage. The roles of each mechanical property in determining the indentation response of cartilage were identified by finite element simulation. Under constant loading, the equilibrium deformation of cartilage is mainly dependent on the compressive modulus, while the initial transient creep behavior is largely regulated by the tensile stiffness. More importantly, altering the permeability does not change the shape of the indentation creep curves, but introduces a parallel shift along the horizontal direction on a logarithmic time scale. Based on these findings, a highly efficient curve-fitting algorithm was designed, which can uniquely determine the three major mechanical properties of cartilage (compressive modulus, tensile modulus, and permeability) from a single indentation test. The new technique was tested on adult bovine knee cartilage and compared with results from the classic biphasic linear elastic curve-fitting program.

  5. Reducing Mechanical Formation Damage by Minimizing Interfacial Tension and Capillary Pressure in Tight Gas

    NASA Astrophysics Data System (ADS)

    Ahmed, Arshad; Talib Shuker, Muhannad; Rehman, Khalil; Bahrami, Hassan; Memon, Muhammad Khan

    2013-12-01

    Tight gas reservoirs incur problems and significant damage caused by low permeability during drilling, completion, stimulation and production. They require advanced improvement techniques to achieve flow gas at optimum rates. Water blocking damage (phase Trapping/retention of fluids) is a form of mechanical formation damage mechanism, which is caused by filtrate invasion in drilling operations mostly in fracturing. Water blocking has a noticeable impact on formation damage in gas reservoirs which tends to decrease relative permeability near the wellbore. Proper evaluation of damage and the factors which influence its severity is essential to optimize well productivity. Reliable data regarding interfacial tension between gas and water is required in order to minimize mechanical formation damage potential and to optimize gas production. This study was based on the laboratory experiments of interfacial tension by rising drop method between gas-brine, gas-condensate and gas-brine. The results showed gas condensate has low interfacial tension value 6 - 11 dynes/cm when compared to gas-brine and gas- diesel which were 44 - 58 dynes/cm and 14 - 19 dynes/cm respectively. In this way, the capillary pressure of brine-gas system was estimated as 0.488 psi, therefore diesel-gas system was noticed about 0.164 psi and 0.098 psi for condensate-gas system. A forecast model was used by using IFT values to predict the phase trapping which shows less severe phase trapping damage in case of condensate than diesel and brine. A reservoir simulation study was also carried out in order to better understand the effect of hysteresis on well productivity and flow efficiency affected due to water blocking damage in tight gas reservoirs.

  6. Device for Investigation of Mechanical Tension of Isolated Smooth Muscle Vessels and Airway Segments of Animals

    NASA Astrophysics Data System (ADS)

    Aleinik, A.; Karpovich, N.; Turgunova, N.; Nosarev, A.

    2016-11-01

    For the purpose of testing and the search for new drug compounds, designed to heal many human diseases, it is necessary to investigate the deformation of experimental tissue samples under influence of these drugs. For this task a precision force sensor for measuring the mechanical tension, produced by isolated ring segments of blood vessels and airways was created. The hardware and software systems for the study of changes in contractile responses of the airway smooth muscles and blood vessels of experimental animals was developed.

  7. Mechanical dynamics in live cells and fluorescence-based force/tension sensors.

    PubMed

    Yang, Chao; Zhang, Xiaohan; Guo, Yichen; Meng, Fanjie; Sachs, Frederick; Guo, Jun

    2015-08-01

    Three signaling systems play the fundamental roles in modulating cell activities: chemical, electrical, and mechanical. While the former two are well studied, the mechanical signaling system is still elusive because of the lack of methods to measure structural forces in real time at cellular and subcellular levels. Indeed, almost all biological processes are responsive to modulation by mechanical forces that trigger dispersive downstream electrical and biochemical pathways. Communication among the three systems is essential to make cells and tissues receptive to environmental changes. Cells have evolved many sophisticated mechanisms for the generation, perception and transduction of mechanical forces, including motor proteins and mechanosensors. In this review, we introduce some background information about mechanical dynamics in live cells, including the ubiquitous mechanical activity, various types of mechanical stimuli exerted on cells and the different mechanosensors. We also summarize recent results obtained using genetically encoded FRET (fluorescence resonance energy transfer)-based force/tension sensors; a new technique used to measure mechanical forces in structural proteins. The sensors have been incorporated into many specific structural proteins and have measured the force gradients in real time within live cells, tissues, and animals.

  8. Mechanical dynamics in live cells and fluorescence-based force/tension sensors

    PubMed Central

    Yang, Chao; Zhang, Xiaohan; Guo, Yichen; Meng, Fanjie; Sachs, Frederick; Guo, Jun

    2016-01-01

    Three signaling systems play the fundamental roles in modulating cell activities: chemical, electrical, and mechanical. While the former two are well studied, the mechanical signaling system is still elusive because of the lack of methods to measure structural forces in real time at cellular and subcellular levels. Indeed, almost all biological processes are responsive to modulation by mechanical forces that trigger dispersive downstream electrical and biochemical pathways. Communication among the three systems is essential to make cells and tissues receptive to environmental changes. Cells have evolved many sophisticated mechanisms for the generation, perception and transduction of mechanical forces, including motor proteins and mechanosensors. In this review, we introduce some background information about mechanical dynamics in live cells, including the ubiquitous mechanical activity, various types of mechanical stimuli exerted on cells and the different mechanosensors. We also summarize recent results obtained using genetically encoded FRET (fluorescence resonance energy transfer)-based force/tension sensors; a new technique used to measure mechanical forces in structural proteins. The sensors have been incorporated into many specific structural proteins and have measured the force gradients in real time within live cells, tissues, and animals. PMID:25958335

  9. Mycolactone-mediated neurite degeneration and functional effects in cultured human and rat DRG neurons: Mechanisms underlying hypoalgesia in Buruli ulcer.

    PubMed

    Anand, U; Sinisi, M; Fox, M; MacQuillan, A; Quick, T; Korchev, Y; Bountra, C; McCarthy, T; Anand, P

    2016-01-01

    Mycolactone is a polyketide toxin secreted by the mycobacterium Mycobacterium ulcerans, responsible for the extensive hypoalgesic skin lesions characteristic of patients with Buruli ulcer. A recent pre-clinical study proposed that mycolactone may produce analgesia via activation of the angiotensin II type 2 receptor (AT2R). In contrast, AT2R antagonist EMA401 has shown analgesic efficacy in animal models and clinical trials for neuropathic pain. We therefore investigated the morphological and functional effects of mycolactone in cultured human and rat dorsal root ganglia (DRG) neurons and the role of AT2R using EMA401. Primary sensory neurons were prepared from avulsed cervical human DRG and rat DRG; 24 h after plating, neurons were incubated for 24 to 96 h with synthetic mycolactone A/B, followed by immunostaining with antibodies to PGP9.5, Gap43, β tubulin, or Mitotracker dye staining. Acute functional effects were examined by measuring capsaicin responses with calcium imaging in DRG neuronal cultures treated with mycolactone. Morphological effects: Mycolactone-treated cultures showed dramatically reduced numbers of surviving neurons and non-neuronal cells, reduced Gap43 and β tubulin expression, degenerating neurites and reduced cell body diameter, compared with controls. Dose-related reduction of neurite length was observed in mycolactone-treated cultures. Mitochondria were distributed throughout the length of neurites and soma of control neurons, but clustered in the neurites and soma of mycolactone-treated neurons. Functional effects: Mycolactone-treated human and rat DRG neurons showed dose-related inhibition of capsaicin responses, which were reversed by calcineurin inhibitor cyclosporine and phosphodiesterase inhibitor 3-isobutyl-1-Methylxanthine, indicating involvement of cAMP/ATP reduction. The morphological and functional effects of mycolactone were not altered by Angiotensin II or AT2R antagonist EMA401. Mycolactone induces toxic effects in DRG

  10. Modeling the Mechanics of Cell Division: Influence of Spontaneous Membrane Curvature, Surface Tension, and Osmotic Pressure

    PubMed Central

    Beltrán-Heredia, Elena; Almendro-Vedia, Víctor G.; Monroy, Francisco; Cao, Francisco J.

    2017-01-01

    Many cell division processes have been conserved throughout evolution and are being revealed by studies on model organisms such as bacteria, yeasts, and protozoa. Cellular membrane constriction is one of these processes, observed almost universally during cell division. It happens similarly in all organisms through a mechanical pathway synchronized with the sequence of cytokinetic events in the cell interior. Arguably, such a mechanical process is mastered by the coordinated action of a constriction machinery fueled by biochemical energy in conjunction with the passive mechanics of the cellular membrane. Independently of the details of the constriction engine, the membrane component responds against deformation by minimizing the elastic energy at every constriction state following a pathway still unknown. In this paper, we address a theoretical study of the mechanics of membrane constriction in a simplified model that describes a homogeneous membrane vesicle in the regime where mechanical work due to osmotic pressure, surface tension, and bending energy are comparable. We develop a general method to find approximate analytical expressions for the main descriptors of a symmetrically constricted vesicle. Analytical solutions are obtained by combining a perturbative expansion for small deformations with a variational approach that was previously demonstrated valid at the reference state of an initially spherical vesicle at isotonic conditions. The analytic approximate results are compared with the exact solution obtained from numerical computations, getting a good agreement for all the computed quantities (energy, area, volume, constriction force). We analyze the effects of the spontaneous curvature, the surface tension and the osmotic pressure in these quantities, focusing especially on the constriction force. The more favorable conditions for vesicle constriction are determined, obtaining that smaller constriction forces are required for positive spontaneous

  11. Modeling the Mechanics of Cell Division: Influence of Spontaneous Membrane Curvature, Surface Tension, and Osmotic Pressure.

    PubMed

    Beltrán-Heredia, Elena; Almendro-Vedia, Víctor G; Monroy, Francisco; Cao, Francisco J

    2017-01-01

    Many cell division processes have been conserved throughout evolution and are being revealed by studies on model organisms such as bacteria, yeasts, and protozoa. Cellular membrane constriction is one of these processes, observed almost universally during cell division. It happens similarly in all organisms through a mechanical pathway synchronized with the sequence of cytokinetic events in the cell interior. Arguably, such a mechanical process is mastered by the coordinated action of a constriction machinery fueled by biochemical energy in conjunction with the passive mechanics of the cellular membrane. Independently of the details of the constriction engine, the membrane component responds against deformation by minimizing the elastic energy at every constriction state following a pathway still unknown. In this paper, we address a theoretical study of the mechanics of membrane constriction in a simplified model that describes a homogeneous membrane vesicle in the regime where mechanical work due to osmotic pressure, surface tension, and bending energy are comparable. We develop a general method to find approximate analytical expressions for the main descriptors of a symmetrically constricted vesicle. Analytical solutions are obtained by combining a perturbative expansion for small deformations with a variational approach that was previously demonstrated valid at the reference state of an initially spherical vesicle at isotonic conditions. The analytic approximate results are compared with the exact solution obtained from numerical computations, getting a good agreement for all the computed quantities (energy, area, volume, constriction force). We analyze the effects of the spontaneous curvature, the surface tension and the osmotic pressure in these quantities, focusing especially on the constriction force. The more favorable conditions for vesicle constriction are determined, obtaining that smaller constriction forces are required for positive spontaneous

  12. Micro-mechanical model for the tension-stabilized enzymatic degradation of collagen tissues

    NASA Astrophysics Data System (ADS)

    Nguyen, Thao; Ruberti, Jeffery

    We present a study of how the collagen fiber structure influences the enzymatic degradation of collagen tissues. Experiments of collagen fibrils and tissues show that mechanical tension can slow and halt enzymatic degradation. Tissue-level experiments also show that degradation rate is minimum at a stretch level coincident with the onset of strain-stiffening in the stress response. To understand these phenomena, we developed a micro-mechanical model of a fibrous collagen tissue undergoing enzymatic degradation. Collagen fibers are described as sinusoidal elastica beams, and the tissue is described as a distribution of fibers. We assumed that the degradation reaction is inhibited by the axial strain energy of the crimped collagen fibers. The degradation rate law was calibrated to experiments on isolated single fibrils from bovine sclera. The fiber crimp and properties were fit to uniaxial tension tests of tissue strips. The fibril-level kinetic and tissue-level structural parameters were used to predict tissue-level degradation-induced creep rate under a constant applied force. We showed that we could accurately predict the degradation-induce creep rate of the pericardium and cornea once we accounted for differences in the fiber crimp structure and properties.

  13. Mechanical tension and spontaneous muscle twitching precede the formation of cross-striated muscle in vivo

    PubMed Central

    Weitkunat, Manuela; Brasse, Martina; Bausch, Andreas R.

    2017-01-01

    Muscle forces are produced by repeated stereotypical actomyosin units called sarcomeres. Sarcomeres are chained into linear myofibrils spanning the entire muscle fiber. In mammalian body muscles, myofibrils are aligned laterally, resulting in their typical cross-striated morphology. Despite this detailed textbook knowledge about the adult muscle structure, it is still unclear how cross-striated myofibrils are built in vivo. Here, we investigate the morphogenesis of Drosophila abdominal muscles and establish them as an in vivo model for cross-striated muscle development. By performing live imaging, we find that long immature myofibrils lacking a periodic actomyosin pattern are built simultaneously in the entire muscle fiber and then align laterally to give mature cross-striated myofibrils. Interestingly, laser micro-lesion experiments demonstrate that mechanical tension precedes the formation of the immature myofibrils. Moreover, these immature myofibrils do generate spontaneous Ca2+-dependent contractions in vivo, which, when chemically blocked, result in cross-striation defects. Taken together, these results suggest a myofibrillogenesis model in which mechanical tension and spontaneous muscle twitching synchronize the simultaneous self-organization of different sarcomeric protein complexes to build highly regular cross-striated myofibrils spanning the length of large muscle fibers. PMID:28174246

  14. Simultaneous Effect of Mechanical Tension on Electrical Lifetime of Some Inorganic Composites

    NASA Astrophysics Data System (ADS)

    Özcanli, Y. Lenger; BoydaǦ, F. Ş.; Alekberov, V. A.; Hikmet, I.; Cantürk, M.

    In this work, the simultaneous effect of mechanical tension (σ) and electrical strength (E) on electrical lifetime (τE) for pure low density polyethylene (LDPE)/polypropylene (PP) and composites with different commercial diamond-additive/glass fiber additive percentages is experimentally studied. The role of this effect on degradation mechanisms is investigated. logτE,σ-f(E) and Eσ-f(σ) graphs are drawn, new equations are proposed and determined parameters at constant temperature for pure LDPE and PP, and for optimum composites (LDPE/0.5% diamond, PP/0.5% glass fiber) are listed. The results indicate that the degradation speed decreases more for composites than for pure LDPE and PP. The electrical durability for composites after the simultaneous effect of σ decreases 18-20%, while for pure LDPE and PP, it decreases 50-55%.

  15. Autophagy protects end plate chondrocytes from intermittent cyclic mechanical tension induced calcification.

    PubMed

    Xu, Hong-guang; Yu, Yun-fei; Zheng, Quan; Zhang, Wei; Wang, Chuang-dong; Zhao, Xiao-yn; Tong, Wen-xue; Wang, Hong; Liu, Ping; Zhang, Xiao-ling

    2014-09-01

    Calcification of end plate chondrocytes is a major cause of intervertebral disc (IVD) degeneration. However, the underlying molecular mechanism of end plate chondrocyte calcification is still unclear. The aim of this study was to clarify whether autophagy in end plate chondrocytes could protect the calcification of end plate chondrocytes. Previous studies showed that intermittent cyclic mechanical tension (ICMT) contributes to the calcification of end plate chondrocytes in vitro. While autophagy serves as a cell survival mechanism, the relationship of autophagy and induced end plate chondrocyte calcification by mechanical tension in vitro is unknown. Thus, we investigated autophagy, the expression of the autophagy genes, Beclin-1 and LC3, and rat end plate chondrocyte calcification by ICMT. The viability of end plate chondrocytes was examined using the LIVE/DEAD viability/cytotoxicity kit. The reverse transcription-polymerase chain reaction and western blotting were used to detect the expression of Beclin-1; LC3; type I, II and X collagen; aggrecan; and Sox-9 genes. Immunofluorescent and fluorescent microscopy showed decreased autophagy in the 10- and 20-day groups loaded with ICMT. Additionally, Alizarin red and alkaline phosphatase staining detected the palpable calcification of end plate chondrocytes after ICMT treatment. We found that increased autophagy induced by short-term ICMT treatment was accompanied by an insignificant calcification of end plate chondrocytes. To the contrary, the suppressive autophagy inhibited by long-term ICMT was accompanied by a more significant calcification. The process of calcification induced by ICMT was partially resisted by increased autophagy activity induced by rapamycin, implicating that autophagy may prevent end plate chondrocyte calcification. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Neurite outgrowth is driven by actin polymerization even in the presence of actin polymerization inhibitors

    PubMed Central

    Chia, Jonathan X.; Efimova, Nadia; Svitkina, Tatyana M.

    2016-01-01

    Actin polymerization is a universal mechanism to drive plasma membrane protrusion in motile cells. One apparent exception to this rule is continuing or even accelerated outgrowth of neuronal processes in the presence of actin polymerization inhibitors. This fact, together with the key role of microtubule dynamics in neurite outgrowth, led to the concept that microtubules directly drive plasma membrane protrusion either in the course of polymerization or by motor-driven sliding. The possibility that unextinguished actin polymerization drives neurite outgrowth in the presence of actin drugs was not explored. We show that cultured hippocampal neurons treated with cytochalasin D or latrunculin B contained dense accumulations of branched actin filaments at ∼50% of neurite tips at all tested drug concentrations (1–10 μM). Actin polymerization is required for neurite outgrowth because only low concentrations of either inhibitor increased the length and/or number of neurites, whereas high concentrations inhibited neurite outgrowth. Of importance, neurites undergoing active elongation invariably contained a bright F-actin patch at the tip, whereas actin-depleted neurites never elongated, even though they still contained dynamic microtubules. Stabilization of microtubules by Taxol treatment did not stop elongation of cytochalasin–treated neurites. We conclude that actin polymerization is indispensable for neurite elongation. PMID:27682586

  17. Lysophosphatidic Acid Induces Neurite Retraction in Differentiated Neuroblastoma Cells via GSK-3β Activation

    PubMed Central

    Sun, Yuanjie; Kim, Nam-Ho; Yang, Haijie; Kim, Seung-Hyuk; Huh, Sung-Oh

    2011-01-01

    Lysophosphatidic acid (LPA) is a lipid growth factor that exerts diverse biological effects, including rapid neurite retraction and cell migration. Alterations in cell morphology, including neurite retraction, in neurodegenerative disorders such as Alzheimer’s disease involve hyperphosphorylation of the cytoskeletal protein tau. Since LPA has been shown to induce neurite retraction in various cultured neural cells and the detailed underlying molecular mechanisms have not yet been elucidated, we investigated whether LPA induced neurite retraction through taumediated signaling pathways in differentiated neuroblastoma cells. When Neuro2a cells differentiated with retinoic acid (RA) were exposed to LPA, cells exhibited neurite retraction in a time-dependent manner. The retraction of neurites was accompanied by the phosphorylation of tau. The LPA-induced neurite retraction and tau phosphorylation in differentiated Neuro2a cells were significantly abolished by the glycogen synthase kinase-3β (GSK-3β) inhibitor lithium chloride. Interestingly, the LPA-stimulated tau phosphorylation and neurite retraction were markedly prevented by the administration of H89, an inhibitor of both cyclic-AMP dependent protein kinase (PKA) and cyclic- AMP response element-binding protein (CREB). Transfection of the dominant-negative CREBs, K-CREB and ACREB, failed to prevent LPA-induced tau phosphorylation and neurite retraction in differentiated Neuro2a cells. Taken together, these results suggest that GSK-3β and PKA, rather than CREB, play important roles in tau phosphorylation and neurite retraction in LPA-stimulated differentiated Neuro2a cells. PMID:21499833

  18. Novel Roles and Mechanism for Krüppel-like Factor 16 (KLF16) Regulation of Neurite Outgrowth and Ephrin Receptor A5 (EphA5) Expression in Retinal Ganglion Cells.

    PubMed

    Wang, Jianbo; Galvao, Joana; Beach, Krista M; Luo, Weijia; Urrutia, Raul A; Goldberg, Jeffrey L; Otteson, Deborah C

    2016-08-26

    Regenerative medicine holds great promise for the treatment of degenerative retinal disorders. Krüppel-like factors (KLFs) are transcription factors that have recently emerged as key tools in regenerative medicine because some of them can function as epigenetic reprogrammers in stem cell biology. Here, we show that KLF16, one of the least understood members of this family, is a POU4F2 independent transcription factor in retinal ganglion cells (RGCs) as early as embryonic day 15. When overexpressed, KLF16 inhibits RGC neurite outgrowth and enhances RGC growth cone collapse in response to exogenous ephrinA5 ligands. Ephrin/EPH signaling regulates RGC connectivity. The EphA5 promoter contains multiple GC- and GT-rich KLF-binding sites, which, as shown by ChIP-assays, bind KLF16 in vivo In electrophoretic mobility shift assays, KLF16 binds specifically to a single KLF site near the EphA5 transcription start site that is required for KLF16 transactivation. Interestingly, methylation of only six of 98 CpG dinucleotides within the EphA5 promoter blocks its transactivation by KLF16 but enables transactivation by KLF2 and KLF15. These data demonstrate a role for KLF16 in regulation of RGC neurite outgrowth and as a methylation-sensitive transcriptional regulator of EphA5 expression. Together, these data identify differential low level methylation as a novel mechanism for regulating KLF16-mediated EphA5 expression across the retina. Because of the critical role of ephrin/EPH signaling in patterning RGC connectivity, understanding the role of KLFs in regulating neurite outgrowth and Eph receptor expression will be vital for successful restoration of functional vision through optic nerve regenerative therapies.

  19. Influence of strain rate on the mechanical behaviour in tension of bovine cortical bone

    NASA Astrophysics Data System (ADS)

    Latella, C.; Dotta, M.; Forni, D.; Tesio, N.; Cadoni, E.

    2015-09-01

    The mechanical behaviour of bones when subjected to tension loading in a wide range of strain-rates is fundamental to develop protection systems. The paper presents the preliminary tests on the tensile behaviour of bovine cortical bone at medium and high strain rates. Two special apparatus, both installed at the DynaMat Laboratory of the University of Applied Sciences of Southern Switzerland, a Hydro-Pneumatic Machine and a Modified Hopkinson Bar respectively for medium and high strain-rate tests have been used. Flat shape specimens (having 10 mm of gauge length, 5 mm width and 3 mm thickness) have been obtained from 15 bovine femurs with the same age. The paper describes the preparation techniques of the samples and the experimental results obtained. The bovine cortical bone shown a quite important strain rate dependency.

  20. Strain rate effects on mechanical properties in tension of aluminium alloys used in armour applications

    NASA Astrophysics Data System (ADS)

    Cadoni, E.; Dotta, M.; Forni, D.; Bianchi, S.; Kaufmann, H.

    2012-08-01

    The mechanical properties in tension of two aluminium alloys (AA5059-H131 and AA7039-T651) used in armour applications were determined from tests carried out over a wide range of strain-rates on round specimens. The experimental research was developed in the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. The target strain rates were set at the following four levels: 10-3, 30, 300 and 1000s-1. The quasi-static tests were performed with a universal electromechanical machine, whereas a hydro-pneumatic machine and a Split Hopkinson Tensile Bar apparatus were used for medium and high strain-rates respectively. The required parameters by the Johnson-Cook constitutive law were also determined.

  1. Pressure and tension effects on mechanical properties of ZrAl{sub 2}

    SciTech Connect

    Zhang, Pinliang; Tang, Xiuzhang; Meng, Fanchen; Gong, Zizheng; Ji, Guangfu; Yang, Jinke

    2014-11-15

    Structural, elastic, thermodynamic of ZrAl{sub 2} under pressure, ideal strength and deformation mode under tension are investigated by the first-principles method. The calculated structural parameters at zero pressure are in consistent with experiments. Under pressure, elastic constants and their pressure dependence are obtained using the static finite strain technique. ZrAl{sub 2} exhibits lower elastic anisotropy. The linear thermal expansion coefficient shows greater effects of temperature at lower pressure. The ideal tensile have been investigated by stress–strain calculations. Finally, the microscopic mechanism that determines the structural stability is studied using the results of electronic structure calculations. We propose that the weakening of Zr-Zr leads to the significant change of stress–strain curve at strain ∼0.27, and the breaking of Zr{sub 2}-Zr{sub 3} leads to the structural instability of ZrAl{sub 2} under large tensile strains.

  2. Improved discretisation and linearisation of active tension in strongly coupled cardiac electro-mechanics simulations

    PubMed Central

    Sundnes, J.; Wall, S.; Osnes, H.; Thorvaldsen, T.; McCulloch, A.D.

    2013-01-01

    Mathematical models of cardiac electro-mechanics typically consist of three tightly coupled parts: systems of ordinary differential equations describing electro-chemical reactions and cross-bridge dynamics in the muscle cells, a system of partial differential equations modelling the propagation of the electrical activation through the tissue and a nonlinear elasticity problem describing the mechanical deformations of the heart muscle. The complexity of the mathematical model motivates numerical methods based on operator splitting, but simple explicit splitting schemes have been shown to give severe stability problems for realistic models of cardiac electro-mechanical coupling. The stability may be improved by adopting semi-implicit schemes, but these give rise to challenges in updating and linearising the active tension. In this paper we present an operator splitting framework for strongly coupled electro-mechanical simulations and discuss alternative strategies for updating and linearising the active stress component. Numerical experiments demonstrate considerable performance increases from an update method based on a generalised Rush–Larsen scheme and a consistent linearisation of active stress based on the first elasticity tensor. PMID:22800534

  3. Improved discretisation and linearisation of active tension in strongly coupled cardiac electro-mechanics simulations.

    PubMed

    Sundnes, J; Wall, S; Osnes, H; Thorvaldsen, T; McCulloch, A D

    2014-01-01

    Mathematical models of cardiac electro-mechanics typically consist of three tightly coupled parts: systems of ordinary differential equations describing electro-chemical reactions and cross-bridge dynamics in the muscle cells, a system of partial differential equations modelling the propagation of the electrical activation through the tissue and a nonlinear elasticity problem describing the mechanical deformations of the heart muscle. The complexity of the mathematical model motivates numerical methods based on operator splitting, but simple explicit splitting schemes have been shown to give severe stability problems for realistic models of cardiac electro-mechanical coupling. The stability may be improved by adopting semi-implicit schemes, but these give rise to challenges in updating and linearising the active tension. In this paper we present an operator splitting framework for strongly coupled electro-mechanical simulations and discuss alternative strategies for updating and linearising the active stress component. Numerical experiments demonstrate considerable performance increases from an update method based on a generalised Rush-Larsen scheme and a consistent linearisation of active stress based on the first elasticity tensor.

  4. Local pressure components and surface tension of spherical interfaces. Thermodynamic versus mechanical definitions. I. A mesoscale modeling of droplets

    NASA Astrophysics Data System (ADS)

    Ghoufi, Aziz; Malfreyt, Patrice

    2011-09-01

    We report mesoscale simulations of spherical drops to investigate the surface tension and mechanical properties. The Monte Carlo simulations are performed with the multibody potential commonly used in the many-body dissipative particle dynamics simulations. We establish here the calculation of the local normal and transverse components of the pressure tensor via the perturbation volume within the thermodynamic route. The different profiles of these components are compared to those calculated using the mechanical approach. To complete the mesoscale modeling of drops, we investigate the curvature dependence of the surface tension in order to calculate the Tolman's length, which is found to be negative.

  5. Laminin receptors for neurite formation

    SciTech Connect

    Kleinman, H.K.; Ogle, R.C.; Cannon, F.B.; Little, C.D.; Sweeney, T.M.; Luckenbill-Edds, L.

    1988-02-01

    Laminin, a basement membrane glycoprotein promotes both cell attachment and neurite outgrowth. Separate domains on laminin elicit these responses, suggesting that distinct receptors occur on the surface of cells. NG108-15 neuroblastoma-glioma cells rapidly extend long processes in the presence of laminin. The authors report here that /sup 125/I-labeled laminin specifically binds to these cells and to three membrane proteins of 67, 110, and 180 kDa. These proteins were isolated by affinity chromatography on laminin-Sepharose. The 67-kDa protein reacted with antibody to the previously characterized receptor for cell attachment to laminin. Antibodies to the 110-kDa and 180-kDa bands demonstrated that the 110-kDa protein was found in a variety of epithelial cell lines and in brain, whereas the 180-kDa protein was neural specific. Antibodies prepared against the 110-kDa and 180-kDa proteins inhibited neurite outgrowth induced by the neurite-promoting domain of laminin, whereas antibodies to the 67-kDa laminin receptor had no effect on neurite outgrowth. They conclude that neuronal cells have multiple cell-surface laminin receptors and that the 110-kDa and 180-kDa proteins are involved in neurite formation.

  6. Using magnets and magnetic beads to dissect signaling pathways activated by mechanical tension applied to cells.

    PubMed

    Marjoram, R J; Guilluy, C; Burridge, K

    2016-02-01

    Cellular tension has implications in normal biology and pathology. Membrane adhesion receptors serve as conduits for mechanotransduction that lead to cellular responses. Ligand-conjugated magnetic beads are a useful tool in the study of how cells sense and respond to tension. Here we detail methods for their use in applying tension to cells and strategies for analyzing the results. We demonstrate the methods by analyzing mechanotransduction through VE-cadherin on endothelial cells using both permanent magnets and magnetic tweezers.

  7. Using Magnets and Magnetic Beads to Dissect Signaling Pathways Activated by Mechanical Tension Applied to Cells

    PubMed Central

    Marjoram, R.J.; Guilluy, C; Burridge, K.

    2015-01-01

    Cellular tension has implications in normal biology and pathology. Membrane adhesion receptors serve as conduits for mechanotransduction that lead to cellular responses. Ligand-conjugated magnetic beads are a useful tool in the study of how cells sense and respond to tension. Here we detail methods for their use in applying tension to cells and strategies for analyzing the results. We demonstrate the methods by analyzing mechanotransduction through VE-cadherin on endothelial cells using both permanent magnets and magnetic tweezers. PMID:26427549

  8. Evaluation of Bulk Mechanical Properties of Selected Lead-Free Solders in Tension and in Shear

    NASA Astrophysics Data System (ADS)

    Devaki Rani, S.; Murthy, G. S.

    2013-08-01

    Lead-free solders are fast emerging as better alternatives to Sn-Pb solders. The reliability of a soldered joint to withstand imposed stresses in an assembly is decided by its mechanical properties. The present work is about the investigation of tensile and shear properties of four binary eutectic alloys Sn-3.5Ag, Sn-58Bi, Sn-0.7Cu, Sn-9Zn and a ternary alloy Sn-57Bi-1.3Zn in comparison with conventional Sn-38Pb alloy. It is observed that the lead-free solders have better mechanical properties than the latter. SEM studies of tensile and shear fracture show ductile dimples circular in tension and parabolic in shear modes supporting the mechanical behavior of the alloys investigated. Eutectic alloys Sn-Ag, Sn-Zn, and Sn-Cu form potential substitutes for Sn-Pb for electronic interconnects exposed to high temperatures, while Sn-Bi and Sn-Bi-Zn are attractive alternatives in addressing the need of lower processing temperatures in printed circuit boards and other applications.

  9. Effect of surface tension and surfactant administration on Eustachian tube mechanics.

    PubMed

    Ghadiali, Samir N; Banks, Julie; Swarts, J Douglas

    2002-09-01

    Development of otitis media has been related to abnormal Eustachian tube (ET) mechanics. ET is a collapsible tube that is periodically opened to regulate middle ear pressure and to clear middle ear fluid into the nasopharynx. The ability to perform these physiological functions depends on several mechanical properties, including the ET's opening pressure (P(open)), compliance (ETC), and hysteresis (eta). In this study, a previously developed modified force-response protocol was used to determine ET mechanical properties after experimental manipulation of the mucosal surface condition. Specifically, these properties were measured in the right ear of six cynomologous monkeys under baseline conditions after "washing out" the normal ET mucous layer and after instillation of a pulmonary surfactant, Infasurf. Removal of the normal mucosa did not significantly alter P(open) but did result in a decrease in ETC and eta (P < 0.05). Treatment of the mucosa with Infasurf was effective in reducing P(open) and increasing both ETC and eta to baseline values (P < 0.05). These results indicate that the mucosa-air surface tension can affect the overall ETC and eta properties of the ET. In addition, this study indicates that surfactant therapy may only be beneficial in patients with rigid or inelastic ETs (large P(open) and low ETC and eta).

  10. Periostin Responds to Mechanical Stress and Tension by Activating the MTOR Signaling Pathway

    PubMed Central

    Rosselli-Murai, Luciana K.; Galindo-Moreno, Pablo; Padial-Molina, Miguel; Volk, Sarah L.; Murai, Marcelo J.; Rios, Hector F.; Squarize, Cristiane H.; Castilho, Rogerio M.

    2013-01-01

    Current knowledge about Periostin biology has expanded from its recognized functions in embryogenesis and bone metabolism to its roles in tissue repair and remodeling and its clinical implications in cancer. Emerging evidence suggests that Periostin plays a critical role in the mechanism of wound healing; however, the paracrine effect of Periostin in epithelial cell biology is still poorly understood. We found that epithelial cells are capable of producing endogenous Periostin that, unlike mesenchymal cell, cannot be secreted. Epithelial cells responded to Periostin paracrine stimuli by enhancing cellular migration and proliferation and by activating the mTOR signaling pathway. Interestingly, biomechanical stimulation of epithelial cells, which simulates tension forces that occur during initial steps of tissue healing, induced Periostin production and mTOR activation. The molecular association of Periostin and mTOR signaling was further dissected by administering rapamycin, a selective pharmacological inhibitor of mTOR, and by disruption of Raptor and Rictor scaffold proteins implicated in the regulation of mTORC1 and mTORC2 complex assembly. Both strategies resulted in ablation of Periostin-induced mitogenic and migratory activity. These results indicate that Periostin-induced epithelial migration and proliferation requires mTOR signaling. Collectively, our findings identify Periostin as a mechanical stress responsive molecule that is primarily secreted by fibroblasts during wound healing and expressed endogenously in epithelial cells resulting in the control of cellular physiology through a mechanism mediated by the mTOR signaling cascade. PMID:24349533

  11. Defect induced plasticity and failure mechanism of boron nitride nanotubes under tension

    SciTech Connect

    Anoop Krishnan, N. M. Ghosh, Debraj

    2014-07-28

    The effects of Stone-Wales (SW) and vacancy defects on the failure behavior of boron nitride nanotubes (BNNTs) under tension are investigated using molecular dynamics simulations. The Tersoff-Brenner potential is used to model the atomic interaction and the temperature is maintained close to 300 K. The effect of a SW defect is studied by determining the failure strength and failure mechanism of nanotubes with different radii. In the case of a vacancy defect, the effect of an N-vacancy and a B-vacancy is studied separately. Nanotubes with different chiralities but similar diameter is considered first to evaluate the chirality dependence. The variation of failure strength with the radius is then studied by considering nanotubes of different diameters but same chirality. It is observed that the armchair BNNTs are extremely sensitive to defects, whereas the zigzag configurations are the least sensitive. In the case of pristine BNNTs, both armchair and zigzag nanotubes undergo brittle failure, whereas in the case of defective BNNTs, only the zigzag ones undergo brittle failure. An interesting defect induced plastic behavior is observed in defective armchair BNNTs. For this nanotube, the presence of a defect triggers mechanical relaxation by bond breaking along the closest zigzag helical path, with the defect as the nucleus. This mechanism results in a plastic failure.

  12. Integrin binding and mechanical tension induce movement of mRNA and ribosomes to focal adhesions

    NASA Technical Reports Server (NTRS)

    Chicurel, M. E.; Singer, R. H.; Meyer, C. J.; Ingber, D. E.

    1998-01-01

    The extracellular matrix (ECM) activates signalling pathways that control cell behaviour by binding to cell-surface integrin receptors and inducing the formation of focal adhesion complexes (FACs). In addition to clustered integrins, FACs contain proteins that mechanically couple the integrins to the cytoskeleton and to immobilized signal-transducing molecules. Cell adhesion to the ECM also induces a rapid increase in the translation of preexisting messenger RNAs. Gene expression can be controlled locally by targeting mRNAs to specialized cytoskeletal domains. Here we investigate whether cell binding to the ECM promotes formation of a cytoskeletal microcompartment specialized for translational control at the site of integrin binding. High-resolution in situ hybridization revealed that mRNA and ribosomes rapidly and specifically localized to FACs that form when cells bind to ECM-coated microbeads. Relocation of these protein synthesis components to the FAC depended on the ability of integrins to mechanically couple the ECM to the contractile cytoskeleton and on associated tension-moulding of the actin lattice. Our results suggest a new type of gene regulation by integrins and by mechanical stress which may involve translation of mRNAs into proteins near the sites of signal reception.

  13. Integrin binding and mechanical tension induce movement of mRNA and ribosomes to focal adhesions

    NASA Technical Reports Server (NTRS)

    Chicurel, M. E.; Singer, R. H.; Meyer, C. J.; Ingber, D. E.

    1998-01-01

    The extracellular matrix (ECM) activates signalling pathways that control cell behaviour by binding to cell-surface integrin receptors and inducing the formation of focal adhesion complexes (FACs). In addition to clustered integrins, FACs contain proteins that mechanically couple the integrins to the cytoskeleton and to immobilized signal-transducing molecules. Cell adhesion to the ECM also induces a rapid increase in the translation of preexisting messenger RNAs. Gene expression can be controlled locally by targeting mRNAs to specialized cytoskeletal domains. Here we investigate whether cell binding to the ECM promotes formation of a cytoskeletal microcompartment specialized for translational control at the site of integrin binding. High-resolution in situ hybridization revealed that mRNA and ribosomes rapidly and specifically localized to FACs that form when cells bind to ECM-coated microbeads. Relocation of these protein synthesis components to the FAC depended on the ability of integrins to mechanically couple the ECM to the contractile cytoskeleton and on associated tension-moulding of the actin lattice. Our results suggest a new type of gene regulation by integrins and by mechanical stress which may involve translation of mRNAs into proteins near the sites of signal reception.

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

    PubMed Central

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

    2010-01-01

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

  15. Organic and inorganic lead inhibit neurite growth in vertebrate and invertebrate neurons in culture.

    PubMed

    Audesirk, G; Shugarts, D; Nelson, G; Przekwas, J

    1989-12-01

    Neurons from brains of chick embryos and pond snails (Lymnaea stagnalis) were cultured for 3 to 4 d in the presence of no toxins, inorganic lead (PbCl2), or organic lead (triethyl lead chloride). In chick neurons, inorganic lead reduced the percentage of cells that grew neurites (IC50 = 270 microM total lead, approximately 70 nM free Pb2+) but did not reduce the number of neurites per cell or the mean neurite length. Triethyl lead reduced the percentage of cells that grew neurites (IC50 = 0.24 microM) and the mean neurite length (extrapolated IC50 = 3.6 microM) but did not reduce the number of neurites per cell. In Lymnaea neurons, inorganic lead reduced the percentage of cells that grew neurites (IC50 = 13 microM total lead; approximately 10 nM free Pb2+). Triethyl lead reduced the percentage of cells that grew neurites (IC50 = 0.4 microM) and exerted significant toxicity at 0.2 microM. The two forms of lead affected neurite growth in qualitatively different ways, which suggests that their mechanisms of action are different.

  16. Mechanical behavior of twinned SiC nanowires under combined tension-torsion and compression-torsion strain

    SciTech Connect

    Li, Zhijie; Wang, Shengjie; Wang, Zhiguo; Zu, Xiaotao T.; Gao, Fei; Weber, William J.

    2010-07-01

    The mechanical behavior of twinned silicon carbide (SiC) nanowires under combined tension-torsion and compression-torsion is investigated using molecular dynamics simulations with an empirical potential. The simulation results show that both the tensile failure stress and buckling stress decrease under combined tension-torsional and combined compression-torsional strain, and they decrease with increasing torsional rate under combined loading. The torsion rate has no effect on the elastic properties of the twinned SiC nanowires. The collapse of the twinned nanowires takes place in a twin stacking fault of the nanowires.

  17. Mechanical performance of external fixators with wires for the treatment of bone fractures--Part II: Wire tension and slippage.

    PubMed

    Delprete, C; Gola, M M

    1993-02-01

    The work shows correct procedures needed in order to gather reliable data from measurement of displacements versus axial load in a laboratory mounting of the Ilizarov external fixator. The mechanism of settling after load cycling is investigated. Detension under load is a major problem of wires. By means of vibration frequency measurements, tests on single wire allow determination of reduction in wire tension due to transverse loading: it is found that, almost independently from the amount of clamp tightening, the tension reaches a lower limit related only to the transverse load and not related to pretension. It is shown that, for higher clamp tightening torques, wire detension must be attributed to permanent plastic deformation of the wires; moreover, it is shown that the unavoidable errors in the spacing of the tensioned wires lead to marked decrease of their stiffness under transverse load.

  18. Influence of Tension-Compression Asymmetry on the Mechanical Behavior of AZ31B Magnesium Alloy Sheets in Bending

    NASA Astrophysics Data System (ADS)

    Zhou, Ping; Beeh, Elmar; Friedrich, Horst E.

    2016-03-01

    Magnesium alloys are promising materials for lightweight design in the automotive industry due to their high strength-to-mass ratio. This study aims to study the influence of tension-compression asymmetry on the radius of curvature and energy absorption capacity of AZ31B-O magnesium alloy sheets in bending. The mechanical properties were characterized using tension, compression, and three-point bending tests. The material exhibits significant tension-compression asymmetry in terms of strength and strain hardening rate due to extension twinning in compression. The compressive yield strength is much lower than the tensile yield strength, while the strain hardening rate is much higher in compression. Furthermore, the tension-compression asymmetry in terms of r value (Lankford value) was also observed. The r value in tension is much higher than that in compression. The bending results indicate that the AZ31B-O sheet can outperform steel and aluminum sheets in terms of specific energy absorption in bending mainly due to its low density. In addition, the AZ31B-O sheet was deformed with a larger radius of curvature than the steel and aluminum sheets, which brings a benefit to energy absorption capacity. Finally, finite element simulation for three-point bending was performed using LS-DYNA and the results confirmed that the larger radius of curvature of a magnesium specimen is mainly attributed to the high strain hardening rate in compression.

  19. CRMP-5 interacts with actin to regulate neurite outgrowth

    PubMed Central

    GONG, XIAOBING; TAN, MINGHUI; GAO, YUAN; CHEN, KEEN; GUO, GUOQING

    2016-01-01

    CRMP family proteins (CRMPs) are abundantly expressed in the developing nervous system mediating growth cone guidance, neuronal polarity and axon elongation. CRMP-5 has been indicated to serve a critical role in neurite outgrowth. However, the detailed mechanisms of how CRMP-5 regulates neurite outgrowth remain unclear. In the current study, co-immunoprecipitation was used to identify the fact that CRMP-5 interacted with the actin and tubulin cytoskeleton networks in the growth cones of developing hippocampal neurons. CRMP-5 exhibited increased affinity towards actin when compared with microtubules. Immunocytochemistry was used to identify the fact that CRMP-5 colocalized with actin predominantly in the C-domain and T-zone in growth cones. In addition, genetic inhibition of CRMP-5 by siRNA suppressed the expression of actin, growth cone development and neurite outgrowth. Overexpression of CRMP-5 promoted the interaction with actin, growth cone development and hippocampal neurite outgrowth. Taken together, these data suggest that CRMP-5 is able to interact with the actin cytoskeleton network in the growth cone and affect growth cone development and neurite outgrowth via this interaction in developing hippocampal neurons. PMID:26677106

  20. Overexpression of the monocyte chemokine CCL2 in dorsal root ganglion neurons causes a conditioning-like increase in neurite outgrowth and does so via a STAT3 dependent mechanism.

    PubMed

    Niemi, Jon P; DeFrancesco-Lisowitz, Alicia; Cregg, Jared M; Howarth, Madeline; Zigmond, Richard E

    2016-01-01

    Neuroinflammation plays a critical role in the regeneration of peripheral nerves following axotomy. An injury to the sciatic nerve leads to significant macrophage accumulation in the L5 DRG, an effect not seen when the dorsal root is injured. We recently demonstrated that this accumulation around axotomized cell bodies is necessary for a peripheral conditioning lesion response to occur. Here we asked whether overexpression of the monocyte chemokine CCL2 specifically in DRG neurons of uninjured mice is sufficient to cause macrophage accumulation and to enhance regeneration or whether other injury-derived signals are required. AAV5-EF1α-CCL2 was injected intrathecally, and this injection led to a time-dependent increase in CCL2 mRNA expression and macrophage accumulation in L5 DRG, with a maximal response at 3 weeks post-injection. These changes led to a conditioning-like increase in neurite outgrowth in DRG explant and dissociated cell cultures. This increase in regeneration was dependent upon CCL2 acting through its primary receptor CCR2. When CCL2 was overexpressed in CCR2-/- mice, macrophage accumulation and enhanced regeneration were not observed. To address the mechanism by which CCL2 overexpression enhances regeneration, we tested for elevated expression of regeneration-associated genes in these animals. Surprisingly, we found that CCL2 overexpression led to a selective increase in LIF mRNA and neuronal phosphorylated STAT3 (pSTAT3) in L5 DRGs, with no change in expression seen in other RAGs such as GAP-43. Blockade of STAT3 phosphorylation by each of two different inhibitors prevented the increase in neurite outgrowth. Thus, CCL2 overexpression is sufficient to induce macrophage accumulation in uninjured L5 DRGs and increase the regenerative capacity of DRG neurons via a STAT3-dependent mechanism. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Overexpression of the Monocyte Chemokine CCL2 in Dorsal Root Ganglion Neurons Causes a Conditioning-Like Increase in Neurite Outgrowth and Does So via a STAT3 Dependent Mechanism

    PubMed Central

    Niemi, Jon P.; DeFrancesco-Lisowitz, Alicia; Cregg, Jared; Howarth, Madeline; Zigmond, Richard E.

    2015-01-01

    Neuroinflammation plays a critical role in the regeneration of peripheral nerves following axotomy. An injury to the sciatic nerve leads to significant macrophage accumulation in the L5 DRG, an effect not seen when the dorsal root is injured. We recently demonstrated that this accumulation around axotomized cell bodies is necessary for a peripheral conditioning lesion response to occur. Here we asked whether overexpression of the monocyte chemokine CCL2 specifically in DRG neurons of uninjured mice is sufficient to cause macrophage accumulation and to enhance regeneration or whether other injury-derived signals are required. AAV5-EF1α-CCL2 was injected intrathecally, and this injection led to a time-dependent increase in CCL2 mRNA expression and macrophage accumulation in L5 DRG, with a maximal response at 3 wk post-injection. These changes led to a conditioning-like increase in neurite outgrowth in DRG explant and dissociated cell cultures. This increase in regeneration was dependent upon CCL2 acting through its primary receptor CCR2. When CCL2 was overexpressed in CCR2 −/− mice, macrophage accumulation and enhanced regeneration were not observed. To address the mechanism by which CCL2 overexpression enhances regeneration, we tested for elevated expression of regeneration-associated genes in these animals. Surprisingly, we found that CCL2 overexpression led to a selective increase in LIF mRNA and neuronal phosphorylated STAT3 (pSTAT3) in L5 DRGs, with no change in expression seen in other RAGs such as GAP-43. Blockade of STAT3 phosphorylation by each of two different inhibitors prevented the increase in neurite outgrowth. Thus, CCL2 overexpression is sufficient to induce macrophage accumulation in uninjured L5 DRGs and increase the regenerative capacity of DRG neurons via a STAT3-dependent mechanism. PMID:26431741

  2. Myosin IC generates power over a range of loads via a new tension-sensing mechanism.

    PubMed

    Greenberg, Michael J; Lin, Tianming; Goldman, Yale E; Shuman, Henry; Ostap, E Michael

    2012-09-11

    Myosin IC (myo1c), a widely expressed motor protein that links the actin cytoskeleton to cell membranes, has been associated with numerous cellular processes, including insulin-stimulated transport of GLUT4, mechanosensation in sensory hair cells, endocytosis, transcription of DNA in the nucleus, exocytosis, and membrane trafficking. The molecular role of myo1c in these processes has not been defined, so to better understand myo1c function, we utilized ensemble kinetic and single-molecule techniques to probe myo1c's biochemical and mechanical properties. Utilizing a myo1c construct containing the motor and regulatory domains, we found the force dependence of the actin-attachment lifetime to have two distinct regimes: a force-independent regime at forces < 1 pN, and a highly force-dependent regime at higher loads. In this force-dependent regime, forces that resist the working stroke increase the actin-attachment lifetime. Unexpectedly, the primary force-sensitive transition is the isomerization that follows ATP binding, not ADP release as in other slow myosins. This force-sensing behavior is unique amongst characterized myosins and clearly demonstrates mechanochemical diversity within the myosin family. Based on these results, we propose that myo1c functions as a slow transporter rather than a tension-sensitive anchor.

  3. Staurosporin induces neurite outgrowth through ROS generation in HN33 hippocampal cell lines.

    PubMed

    Min, J Y; Park, M H; Park, M K; Park, K W; Lee, N W; Kim, T; Kim, H J; Lee, D H

    2006-11-01

    Staurosporin, a specific inhibitor of PKC, is widely used in studies of signal transduction pathways. Previous studies have shown that staurosporin induces neurite outgrowth, but the underlying mechanisms remain unclear. Here we report that staurosporin induces neurite outgrowth in HN33 hippocampal cells. Two other PKC inhibitors, Go 6976 (specific for alpha- and beta-isoforms) and rotterlin (a selective inhibitor of PKC delta), have no neuritogenic effect. In addition, staurosporin specifically increases ROS generation. NAC, which inhibits the generation of ROS, suppresses the staurosporin-induced neurite outgrowth in HN33 cells. Further, H(2)O(2) causes neurite outgrowth. Taken together, these results confirm a neuritogenic effect of staurosporin and point to ROS as the signal mediator of staurosporin-induced neurite outgrowth in HN33 hippocampal cells. Theme: Development and regeneration Topic: Neurotrophic factors: receptors and cellular mechanisms.

  4. The effect of high oxygen tensions on the mechanical properties of rat lungs

    PubMed Central

    Hurley, R. M.; Rosenberg, Edith

    1970-01-01

    1. The average mechanical properties of groups of lungs or lung—thorax systems from pathogen-free rats weighing approximately 200 g were determined. Static pressure—volume curves and resistances to air-flow were obtained. 2. Six series, each of sixteen rats, were studied. Eight experimental rats in each series were exposed to 4 atm O2 (OHP) in a transparent pressure chamber; the other eight rats, which served as controls, were obtained from the breeder at the same time and studied at the same time. 3. In four series, the experimental animals were killed 10 min after gasping due to OHP had been definitely established. One series was a control in which experimental animals were exposed to 4 atm of pressure in an atmosphere containing oxygen at a tension of 150 mm Hg for 190 min. The experimental animals in the sixth series were exposed to 4 atm O2 for 2 hr and none of them gasped. 4. Gross and histological examination of sixteen rats, eight of which were killed after 10 min of gasping at 4 atm O2, showed that at this stage of intoxication there was no evidence of pulmonary pathology. 5. In none of the series studied were the static pressure—volume curves for deflation shifted, i.e. OHP did not affect the elastic properties of the lungs or the alveolar surfactant. 6. In two series studied 10 min after gasping behaviour had been established there was a significant decrease of resistance to air-flow and a shift to the left of the static pressure—volume curve for inflation with air. The rats in both these series were sedated with pentobarbitone and then killed with pentobarbitone injected into the jugular vein. 7. The decrease in resistance to air-flow was interpreted as broncho-dilatation and a possible mechanism whereby OHP produces broncho-dilatation is discussed. PMID:5503886

  5. Neuroprotective copper bis(thiosemicarbazonato) complexes promote neurite elongation.

    PubMed

    Bica, Laura; Liddell, Jeffrey R; Donnelly, Paul S; Duncan, Clare; Caragounis, Aphrodite; Volitakis, Irene; Paterson, Brett M; Cappai, Roberto; Grubman, Alexandra; Camakaris, James; Crouch, Peter J; White, Anthony R

    2014-01-01

    Abnormal biometal homeostasis is a central feature of many neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and motor neuron disease. Recent studies have shown that metal complexing compounds behaving as ionophores such as clioquinol and PBT2 have robust therapeutic activity in animal models of neurodegenerative disease; however, the mechanism of neuroprotective action remains unclear. These neuroprotective or neurogenerative processes may be related to the delivery or redistribution of biometals, such as copper and zinc, by metal ionophores. To investigate this further, we examined the effect of the bis(thiosemicarbazonato)-copper complex, Cu(II)(gtsm) on neuritogenesis and neurite elongation (neurogenerative outcomes) in PC12 neuronal-related cultures. We found that Cu(II)(gtsm) induced robust neurite elongation in PC12 cells when delivered at concentrations of 25 or 50 nM overnight. Analogous effects were observed with an alternative copper bis(thiosemicarbazonato) complex, Cu(II)(atsm), but at a higher concentration. Induction of neurite elongation by Cu(II)(gtsm) was restricted to neurites within the length range of 75-99 µm with a 2.3-fold increase in numbers of neurites in this length range with 50 nM Cu(II)(gtsm) treatment. The mechanism of neurogenerative action was investigated and revealed that Cu(II)(gtsm) inhibited cellular phosphatase activity. Treatment of cultures with 5 nM FK506 (calcineurin phosphatase inhibitor) resulted in analogous elongation of neurites compared to 50 nM Cu(II)(gtsm), suggesting a potential link between Cu(II)(gtsm)-mediated phosphatase inhibition and neurogenerative outcomes.

  6. Neuroprotective Copper Bis(thiosemicarbazonato) Complexes Promote Neurite Elongation

    PubMed Central

    Bica, Laura; Liddell, Jeffrey R.; Donnelly, Paul S.; Duncan, Clare; Caragounis, Aphrodite; Volitakis, Irene; Paterson, Brett M.; Cappai, Roberto; Grubman, Alexandra; Camakaris, James; Crouch, Peter J.; White, Anthony R.

    2014-01-01

    Abnormal biometal homeostasis is a central feature of many neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and motor neuron disease. Recent studies have shown that metal complexing compounds behaving as ionophores such as clioquinol and PBT2 have robust therapeutic activity in animal models of neurodegenerative disease; however, the mechanism of neuroprotective action remains unclear. These neuroprotective or neurogenerative processes may be related to the delivery or redistribution of biometals, such as copper and zinc, by metal ionophores. To investigate this further, we examined the effect of the bis(thiosemicarbazonato)-copper complex, CuII(gtsm) on neuritogenesis and neurite elongation (neurogenerative outcomes) in PC12 neuronal-related cultures. We found that CuII(gtsm) induced robust neurite elongation in PC12 cells when delivered at concentrations of 25 or 50 nM overnight. Analogous effects were observed with an alternative copper bis(thiosemicarbazonato) complex, CuII(atsm), but at a higher concentration. Induction of neurite elongation by CuII(gtsm) was restricted to neurites within the length range of 75–99 µm with a 2.3-fold increase in numbers of neurites in this length range with 50 nM CuII(gtsm) treatment. The mechanism of neurogenerative action was investigated and revealed that CuII(gtsm) inhibited cellular phosphatase activity. Treatment of cultures with 5 nM FK506 (calcineurin phosphatase inhibitor) resulted in analogous elongation of neurites compared to 50 nM CuII(gtsm), suggesting a potential link between CuII(gtsm)-mediated phosphatase inhibition and neurogenerative outcomes. PMID:24587210

  7. Quercetin promotes neurite growth through enhancing intracellular cAMP level and GAP-43 expression.

    PubMed

    Chen, Ming-Ming; Yin, Zhi-Qi; Zhang, Lu-Yong; Liao, Hong

    2015-09-01

    The present study was designed to investigate the role of quercetin on neurite growth in N1E-115 cells and the underlying mechanisms. Quercetin was evaluated for its effects on cell numbers of neurites, neurite length, intracellular cAMP content, and Gap-43 expression in N1E-115 cells in vitro by use of microscopy, LANCE(tm) cAMP 384 kit, and Western blot analysis, respectively. Our results showed that quercetin could increase the neurite length in a concentration-dependent manner, but had no effect on the numbers of cells. Quercetin significantly increased the expression of cellular cAMP in a time- and concentration-dependent manner. The Gap-43 expression was up-regulated in a time-dependent manner. In conclusion, quercetin could promote neurite growth through increasing the intracellular cAMP level and Gap-43 expression.

  8. Material Stiffness Effects on Neurite Alignment to Photopolymerized Micropatterns

    PubMed Central

    2015-01-01

    The ability to direct neurite growth into a close proximity of stimulating elements of a neural prosthesis, such as a retinal or cochlear implant (CI), may enhance device performance and overcome current spatial signal resolution barriers. In this work, spiral ganglion neurons (SGNs), which are the target neurons to be stimulated by CIs, were cultured on photopolymerized micropatterns with varied matrix stiffnesses to determine the effect of rigidity on neurite alignment to physical cues. Micropatterns were generated on methacrylate thin film surfaces in a simple, rapid photopolymerization step by photomasking the prepolymer formulation with parallel line–space gratings. Two methacrylate series, a nonpolar HMA-co-HDDMA series and a polar PEGDMA-co-EGDMA series, with significantly different surface wetting properties were evaluated. Equivalent pattern periodicity was maintained across each methacrylate series based on photomask band spacing, and the feature amplitude was tuned to a depth of 2 μm amplitude for all compositions using the temporal control afforded by the UV curing methodology. The surface morphology was characterized by scanning electron microscopy and white light interferometry. All micropatterned films adsorb similar amounts of laminin from solution, and no significant difference in SGN survival was observed when the substrate compositions were compared. SGN neurite alignment significantly increases with increasing material modulus for both methacrylate series. Interestingly, SGN neurites respond to material stiffness cues that are orders of magnitude higher (GPa) than what is typically ascribed to neural environments (kPa). The ability to understand neurite response to engineered physical cues and mechanical properties such as matrix stiffness will allow the development of advanced biomaterials that direct de novo neurite growth to address the spatial signal resolution limitations of current neural prosthetics. PMID:25211120

  9. Mechanical properties of nanocrystalline metals, intermetalics and multiphase materials determined by tension, compression and disk-bend techniques

    SciTech Connect

    Eastman, J.A.; Thompson, L.J.; DiMelfi, R.J.; Choudry, M. Dollar, M.; Weertman, J.R.; Rittner, M.N.; Youngdahl, C.J. /

    1997-02-01

    The mechanical behavior of nanocrystalline metallic, intermetallic, and multiphase materials was investigated using tension, compression, and disk-bend techniques. Nanocrystalline NiAl, Al-Al{sub 3}Zr, and Cu were synthesized by gas condensation and either resistive or electron beam heating followed by high temperature vacuum compaction. Disk- bend tests of nanocrystalline NiAl show evidence of improved ductility at room temperature in this normally extremely brittle material. In contrast, tension tests of multiphase nanocrystalline Al- Al{sub 3}Zr samples show significant increases in strength by substantial reductions in ductility with decreasing grain size. Compression tests of nanocrystalline copper result in substantially higher yield stress and total elongation values than those measured in tensile tests. Implications for operative deformation mechanisms in these materials are discussed.

  10. A local difference in Hedgehog signal transduction increases mechanical cell bond tension and biases cell intercalations along the Drosophila anteroposterior compartment boundary.

    PubMed

    Rudolf, Katrin; Umetsu, Daiki; Aliee, Maryam; Sui, Liyuan; Jülicher, Frank; Dahmann, Christian

    2015-11-15

    Tissue organization requires the interplay between biochemical signaling and cellular force generation. The formation of straight boundaries separating cells with different fates into compartments is important for growth and patterning during tissue development. In the developing Drosophila wing disc, maintenance of the straight anteroposterior (AP) compartment boundary involves a local increase in mechanical tension at cell bonds along the boundary. The biochemical signals that regulate mechanical tension along the AP boundary, however, remain unknown. Here, we show that a local difference in Hedgehog signal transduction activity between anterior and posterior cells is necessary and sufficient to increase mechanical tension along the AP boundary. This difference in Hedgehog signal transduction is also required to bias cell rearrangements during cell intercalations to keep the characteristic straight shape of the AP boundary. Moreover, severing cell bonds along the AP boundary does not reduce tension at neighboring bonds, implying that active mechanical tension is upregulated, cell bond by cell bond. Finally, differences in the expression of the homeodomain-containing protein Engrailed also contribute to the straight shape of the AP boundary, independently of Hedgehog signal transduction and without modulating cell bond tension. Our data reveal a novel link between local differences in Hedgehog signal transduction and a local increase in active mechanical tension of cell bonds that biases junctional rearrangements. The large-scale shape of the AP boundary thus emerges from biochemical signals inducing patterns of active tension on cell bonds. © 2015. Published by The Company of Biologists Ltd.

  11. Effect of mechanical stimulation by tooth brushing on oxygen tension in dog gingiva.

    PubMed

    Tanaka, M; Hanioka, T; Ojima, M; Hori, T; Shizukuishi, S

    1994-11-01

    To determine oxygen tension (pO2) in gingival tissue, an oxygen micro-electrode with a membrane-coated Pt needle was inserted into the gingiva of 12 dogs. Teeth were brushed using a modified Bass technique for 10 s under 200 g pressure. pO2 increased and reached a maximum 15 min after brushing, then gradually returned to the baseline. A significant increase in pO2 persisted for approx. 1 h. These findings suggest that short-term stimulation by tooth brushing increases oxygen tension in the gingiva.

  12. Mechanical Analyses of Real Time Warp Yarn Tensions in Size-Free Weaving

    USDA-ARS?s Scientific Manuscript database

    A 100% cotton, size-less common warp was used to study the real-time tensions of single strands of the warp during weaving on a high-speed weaving machine. The machine was operated under almost mill-like conditions. In order to investigate the independent effects of the weaving speed and fabric cons...

  13. Change Mechanisms in EMG Biofeedback Training: Cognitive Changes Underlying Improvements in Tension Headache.

    ERIC Educational Resources Information Center

    Holroyd, Kenneth A.; And Others

    1984-01-01

    Subjects (N=43) suffering from tension headache were assigned to one of four electromyograph (EMG) biofeedback conditions and were led to believe they were achieving high or moderate success in decreasing EMG activity. Regardless of actual EMG changes, subjects receiving high-success feedback showed greater improvement for headaches than…

  14. Change Mechanisms in EMG Biofeedback Training: Cognitive Changes Underlying Improvements in Tension Headache.

    ERIC Educational Resources Information Center

    Holroyd, Kenneth A.; And Others

    1984-01-01

    Subjects (N=43) suffering from tension headache were assigned to one of four electromyograph (EMG) biofeedback conditions and were led to believe they were achieving high or moderate success in decreasing EMG activity. Regardless of actual EMG changes, subjects receiving high-success feedback showed greater improvement for headaches than…

  15. The influence of binder film thickness on the mechanical properties of binder films in tension.

    PubMed

    Ononokpono, O E; Spring, M S

    1988-02-01

    The physicomechanical properties of films of different thicknesses, made from methylcellulose and gelatinized maize starch, have been studied in tension. There was a linear relation between film thickness and tensile strength, toughness, elastic resilence and elongation at fracture. Young's modulus increased with decreasing film thickness particularly with films with a thickness of less than 15 micron.

  16. Tropomodulins are negative regulators of neurite outgrowth

    PubMed Central

    Fath, Thomas; Fischer, Robert S.; Dehmelt, Leif; Halpain, Shelley; Fowler, Velia M.

    2010-01-01

    Regulation of the actin cytoskeleton is critical for neurite formation. Tropomodulins (Tmods) regulate polymerization at actin filament pointed ends. Previous experiments using a mouse model deficient for the neuron specific isoform Tmod2 suggested a role for Tmods in neuronal function by impacting processes underlying learning and memory. However, the role of Tmods in neuronal function on the cellular level remains unknown. Immunofluorescence localization of the neuronal isoforms Tmod1 and Tmod2 in cultured rat primary hippocampal neurons revealed that Tmod1 is enriched along the proximal part of F-actin bundles in lamellipodia of spreading cells and in growth cones of extending neurites, while Tmod2 appears largely cytoplasmic. Functional analysis of these Tmod isoforms in a mouse neuroblastoma N2a cell line showed that knockdown of Tmod2 resulted in a significant increase in number of neurite-forming cells and in neurite length. While N2a cells compensated for Tmod2 knockdown by increasing Tmod1 levels, over-expression of exogenous Tmod1 had no effect on neurite outgrowth. Moreover, knockdown of Tmod1 increased the number of neurites formed per cell, without effect on number of neurite-forming cells or neurite length. Taken together, these results indicate that Tmod1 and Tmod2 have mechanistically distinct inhibitory roles in neurite formation, likely mediated via different effects on F-actin dynamics and via differential localizations during early neuritogenesis. PMID:21146252

  17. Contribution of human skin topography to the characterization of dynamic skin tension during senescence: morpho-mechanical approach

    NASA Astrophysics Data System (ADS)

    Zahouani, H.; Djaghloul, M.; Vargiolu, R.; Mezghani, S.; Mansori, M. E. L.

    2014-03-01

    The structuring of the dermis with a network of collagen and elastic fibres gives a three-dimensional structure to the skin network with directions perpendicular and parallel to the skin surface. This three-dimensional morphology prints on the surface of the stratum corneum a three dimensional network of lines which express the mechanical tension of the skin at rest. To evaluate the changes of skin morphology, we used a three-dimensional confocal microscopy and characterization of skin imaging of volar forearm microrelief. We have accurately characterize the role of skin line network during chronological aging with the identification of depth scales on the network of lines (z <= 60μm) and the network of lines covering Langer's lines (z > 60 microns). During aging has been highlighted lower rows for elastic fibres, the decrease weakened the tension and results in enlargement of the plates of the microrelief, which gives us a geometric pertinent indicator to quantify the loss of skin tension and assess the stage of aging. The study of 120 Caucasian women shows that ageing in the volar forearm zone results in changes in the morphology of the line network organisation. The decrease in secondary lines (z <= 60 μm) is counterbalanced by an increase in the depth of the primary lines (z > 60 μm) and an accentuation of the anisotropy index.

  18. Calsyntenin-3 C-terminal fragment accumulates in dystrophic neurites surrounding aβ plaques in tg2576 mouse and Alzheimer disease brains: its neurotoxic role in mediating dystrophic neurite formation.

    PubMed

    Uchida, Yoko; Gomi, Fujiya; Murayama, Shigeo; Takahashi, Hiroshi

    2013-05-01

    Dystrophic neurites surrounding β-amyloid (Aβ) plaques precede neuronal death in Alzheimer disease. These neuritic alterations may be one of the initial stages for synaptic loss and dysfunction. However, intracellular pathways that cause local disruption of neuronal processes by Aβ remain to be fully elucidated. The identification of Aβ-induced genes that mediate neuritic pathology would provide considerable insight into the mechanisms of Alzheimer's disease. Previously, we reported that selective up-regulation of calsyntenin-3 (Cst-3) by Aβ and accumulation of neurotoxic Cst-3 in dystrophic neurites surrounding Aβ plaques may lead to local disruption of these neurites. Like amyloid precursor protein, Cst-3 undergoes two-step proteolytic processing: the primary cleavage with α-secretase generates an N-terminal ectodomain and a C-terminal fragment (CTF). The CTF is subsequently cleaved into p3 peptide and an intracellular domain via γ-secretase. It would be interesting to know whether accumulated Cst-3 in dystrophic neurites surrounding Aβ plaques is the full-length version or a CTF. Herein, we show that the CTF but not full-length Cst-3 accumulated in dystrophic neurites surrounding Aβ plaques in Tg2576 mouse and Alzheimer disease brains. In vitro experiments with Cst-3 fragments have revealed that only the CTF resulted in acceleration of neuronal death. These results indicate that accumulation of the neurotoxic CTF in neurites surrounding Aβ plaques may lead to local disruption of neuronal processes and development of dystrophic neurites.

  19. The effect of temperature induced surface tension gradients on bubble mechanics

    NASA Technical Reports Server (NTRS)

    Mcgrew, J. L.; Rehm, T. L.; Griskey, R. G.

    1974-01-01

    Experiments were conducted to examine in detail the influence of surface tension gradient induced flow, the Marangoni effect. One set of studies provided visual results that demonstrated the occurrence and magnitude of the Marangoni effect. Another portion of the work was directed to bubble force measurements. These studies used in deflection of a very fine cantilevered wire with an attached bubble as a means of measuring force with and without temperature gradients. The experimental force data were found to check existing theoretical predictions reasonably well except for the case where the test fluid had a sizeable vapor pressure. In this situation the thermophoretic force on the bubble was much higher than predicted.

  20. Lignification and tension wood.

    PubMed

    Pilate, Gilles; Chabbert, Brigitte; Cathala, Bernard; Yoshinaga, Arata; Leplé, Jean-Charles; Laurans, Françoise; Lapierre, Catherine; Ruel, Katia

    2004-01-01

    Hardwood trees are able to reorient their axes owing to tension wood differentiation. Tension wood is characterised by important ultrastructural modifications, such as the occurrence in a number of species, of an extra secondary wall layer, named gelatinous layer or G-layer, mainly constituted of cellulose microfibrils oriented nearly parallel to the fibre axis. This G-layer appears directly involved in the definition of tension wood mechanical properties. This review gathers the data available in the literature about lignification during tension wood formation. Potential roles for lignin in tension wood formation are inferred from biochemical, anatomical and mechanical studies, from the hypotheses proposed to describe tension wood function and from data coming from new research areas such as functional genomics.

  1. Girdin/GIV is upregulated by cyclic tension, propagates mechanical signal transduction, and is required for the cellular proliferation and migration of MG-63 cells

    SciTech Connect

    Hu, Jiang-Tian; Li, Yan; Yu, Bing; Gao, Guo-Jie; Zhou, Ting; Li, Song

    2015-08-21

    To explore how Girdin/GIV is regulated by cyclic tension and propagates downstream signals to affect cell proliferation and migration. Human osteoblast-like MG-63 cells were exposed to cyclic tension force at 4000 μstrain and 0.5 Hz for 6 h, produced by a four-point bending system. Cyclic tension force upregulated Girdin and Akt expression and phosphorylation in cultured MG-63 cells. Girdin and Akt each promoted the phosphorylation of the other under stimulated tension. In vitro MTT and transwell assays showed that Girdin and Akt are required for cell proliferation and migration during cellular quiescence. Moreover, STAT3 was determined to be essential for Girdin expression under stimulated tension force in the physiological condition, as well as for osteoblast proliferation and migration during quiescence. These findings suggest that the STAT3/Girdin/Akt pathway activates in osteoblasts in response to mechanical stimulation and may play a significant role in triggering osteoblast proliferation and migration during orthodontic treatment. - Highlights: • Tension force upregulates Girdin and Akt expression and phosphorylation. • Girdin and Akt promotes the phosphorylation of each other under tension stimulation. • Girdin and Akt are required for MG-63 cell proliferation and migration. • STAT3 is essential for Girdin expression after application of the tension forces.

  2. Tiam1 as a signaling mediator of nerve growth factor-dependent neurite outgrowth.

    PubMed

    Shirazi Fard, Shahrzad; Kele, Julianna; Vilar, Marçal; Paratcha, Gustavo; Ledda, Fernanda

    2010-03-19

    Nerve Growth Factor (NGF)-induced neuronal differentiation requires the activation of members of the Rho family of small GTPases. However, the molecular mechanisms through which NGF regulates cytoskeletal changes and neurite outgrowth are not totally understood. In this work, we identify the Rac1-specific guanine exchange factor (GEF) Tiam1 as a novel mediator of NGF/TrkA-dependent neurite elongation. In particular, we report that knockdown of Tiam1 causes a significant reduction in Rac1 activity and neurite outgrowth induced by NGF. Physical interaction between Tiam1 and active Ras (Ras-GTP), but not tyrosine phosphorylation of Tiam1, plays a central role in Rac1 activation by NGF. In addition, our findings indicate that Ras is required to associate Tiam1 with Rac1 and promote Rac1 activation upon NGF stimulation. Taken together, these findings define a novel molecular mechanism through which Tiam1 mediates TrkA signaling and neurite outgrowth induced by NGF.

  3. Mps1 kinase promotes sister-kinetochore bi-orientation by a tension-dependent mechanism.

    PubMed

    Maure, Jean-François; Kitamura, Etsushi; Tanaka, Tomoyuki U

    2007-12-18

    Segregation of sister chromatids to opposite spindle poles during anaphase is dependent on the prior capture of sister kinetochores by microtubules extending from opposite spindle poles (bi-orientation). If sister kinetochores attach to microtubules from the same pole (syntelic attachment), the kinetochore-spindle pole connections must be re-oriented to be converted to proper bi-orientation. This re-orientation is facilitated by Aurora B kinase (Ipl1 in budding yeast), which eliminates kinetochore-spindle pole connections that do not generate tension. Mps1 is another evolutionarily conserved protein kinase, required for spindle-assembly checkpoint and, in some organisms, for duplication of microtubule-organizing centers. Separately from these functions, however, Mps1 has an important role in chromosome segregation. Here we show that, in budding yeast, Mps1 has a crucial role in establishing sister-kinetochore bi-orientation on the mitotic spindle. Failure in bi-orientation with inactive Mps1 is not due to a lack of kinetochore-spindle pole connections by microtubules, but due to a defect in properly orienting the connections. Mps1 promotes re-orientation of kinetochore-spindle pole connections and eliminates those that do not generate tension between sister kinetochores. We did not find evidence that Ipl1 regulates Mps1 or vice versa; therefore, they play similar, but possibly independent, roles in facilitating bi-orientation.

  4. Mouse Acetylcholinesterase Enhances Neurite Outgrowth of Rat R28 Cells Through Interaction With Laminin-1

    PubMed Central

    Sperling, Laura E.; Klaczinski, Janine; Schütz, Corina; Rudolph, Lydia; Layer, Paul G.

    2012-01-01

    The enzyme acetylcholinesterase (AChE) terminates synaptic transmission at cholinergic synapses by hydrolyzing the neurotransmitter acetylcholine, but can also exert ‘non-classical’, morpho-regulatory effects on developing neurons such as stimulation of neurite outgrowth. Here, we investigated the role of AChE binding to laminin-1 on the regulation of neurite outgrowth by using cell culture, immunocytochemistry, and molecular biological approaches. To explore the role of AChE, we examined fiber growth of cells overexpressing different forms of AChE, and/or during their growth on laminin-1. A significant increase of neuritic growth as compared with controls was observed for neurons over-expressing AChE. Accordingly, addition of globular AChE to the medium increased total length of neurites. Co-transfection with PRIMA, a membrane anchor of AChE, led to an increase in fiber length similar to AChE overexpressing cells. Transfection with an AChE mutant that leads to the retention of AChE within cells had no stimulatory effect on neurite length. Noticeably, the longest neurites were produced by neurons overexpressing AChE and growing on laminin-1, suggesting that the AChE/laminin interaction is involved in regulating neurite outgrowth. Our findings demonstrate that binding of AChE to laminin-1 alters AChE activity and leads to increased neurite growth in culture. A possible mechanism of the AChE effect on neurite outgrowth is proposed due to the interaction of AChE with laminin-1. PMID:22570738

  5. Comparison of rheological, mechanical, electrical properties of HDPE filled with BaTiO3 with different polar surface tension

    NASA Astrophysics Data System (ADS)

    Su, Jun; Zhang, Jun

    2016-12-01

    In this work, three types of coupling agents: isopropyl trioleic titanate (NDZ105), vinyltriethoxysilane (SG-Si151), 3-aminopropyltriethoxysilane (KH550) were applied to modify the surface tension of Barium titanate (BaTiO3) particles. The Fourier transform infrared (FT-IR) spectra confirm the chemical adherence of coupling agents to the particle surface. The long hydrocarbon chains in NDZ105 can cover the particle surface and reduce the polar surface tension of BaTiO3 from 37.53 mJ/m2 to 7.51 mJ/m2, turning it from hydrophilic to oleophilic properties. The short and non-polar vinyl groups in SG-Si151 does not influence the surface tension of BaTiO3, but make BaTiO3 have both hydrophilic and oleophilic properties. The polar amino in KH550 can keep BaTiO3 still with hydrophilic properties. It is found that SG-Si151 modified BaTiO3 has the lowest interaction with HDPE matrix, lowering the storage modulus of HDPE composites to the greatest extent. As for mechanical properties, the polar amino groups in KH550 on BaTiO3 surface can improve the adhesion of BaTiO3 with HDPE matrix, which increases the elongation at break of HDPE composites to the greatest extent. In terms of electrical properties, the polar amino groups on surface of BaTiO3 can boost the dielectric properties of HDPE/BaTiO3 composites and decrease the volume resistivity of HDPE/BaTiO3 composites. The aim of this study is to investigate how functional groups affect the rheological, mechanical and electrical properties of HDPE composites and to select a coupling agent to produce HDPE/BaTiO3 composites with low dielectric loss, high dielectric constant and elongation at break.

  6. Surface Tension

    NASA Technical Reports Server (NTRS)

    Theissen, David B.; Man, Kin F.

    1996-01-01

    The effect of surface tension is observed inmany everyday situations. For example, a slowly leaking faucet drips because the force surface tension allows the water to cling to it until a sufficient mass of water is accumulated to break free.

  7. Prediction of plastic instabilities under thermo-mechanical loadings in tension and simple shear

    NASA Astrophysics Data System (ADS)

    Manach, P. Y.; Mansouri, L. F.; Thuillier, S.

    2016-08-01

    Plastic instabilities like Portevin-Le Châtelier were quite thoroughly investigated experimentally in tension, under a large range of strain rates and temperatures. Such instabilities are characterized both by a jerky flow and a localization of the strain in bands. Similar phenomena were also recorded for example in simple shear [1]. Modelling of this phenomenon is mainly performed at room temperature, taking into account the strain rate sensitivity, though an extension of the classical Estrin-Kubin-McCormick was proposed in the literature, by making some of the material parameters dependent on temperature. A similar approach is considered in this study, furthermore extended for anisotropic plasticity with Hill's 1948 yield criterion. Material parameters are identified at 4 different temperatures, ranging from room temperature up to 250°C. The identification procedure is split in 3 steps, related to the elasticity, the average stress level and the magnitude of the stress drops. The anisotropy is considered constant in this temperature range, as evidenced by experimental results [2]. The model is then used to investigate the temperature dependence of the critical strain, as well as its capability to represent the propagation of the bands. Numerical predictions of the instabilities in tension and simple shear at room temperature and up to 250°C are compared with experimental results [3]. In the case of simple shear, a monotonic loading followed by unloading and reloading in the reverse direction (“Bauschinger-type” test) is also considered, showing that (i) kinematic hardening should be taken into account to fully describe the transition at re-yielding (ii) the modelling of the critical strain has to be improved.

  8. RNA localization is a key determinant of neurite-enriched proteome.

    PubMed

    Zappulo, Alessandra; van den Bruck, David; Ciolli Mattioli, Camilla; Franke, Vedran; Imami, Koshi; McShane, Erik; Moreno-Estelles, Mireia; Calviello, Lorenzo; Filipchyk, Andrei; Peguero-Sanchez, Esteban; Müller, Thomas; Woehler, Andrew; Birchmeier, Carmen; Merino, Enrique; Rajewsky, Nikolaus; Ohler, Uwe; Mazzoni, Esteban O; Selbach, Matthias; Akalin, Altuna; Chekulaeva, Marina

    2017-09-19

    Protein subcellular localization is fundamental to the establishment of the body axis, cell migration, synaptic plasticity, and a vast range of other biological processes. Protein localization occurs through three mechanisms: protein transport, mRNA localization, and local translation. However, the relative contribution of each process to neuronal polarity remains unknown. Using neurons differentiated from mouse embryonic stem cells, we analyze protein and RNA expression and translation rates in isolated cell bodies and neurites genome-wide. We quantify 7323 proteins and the entire transcriptome, and identify hundreds of neurite-localized proteins and locally translated mRNAs. Our results demonstrate that mRNA localization is the primary mechanism for protein localization in neurites that may account for half of the neurite-localized proteome. Moreover, we identify multiple neurite-targeted non-coding RNAs and RNA-binding proteins with potential regulatory roles. These results provide further insight into the mechanisms underlying the establishment of neuronal polarity.Subcellular localization of RNAs and proteins is important for polarized cells such as neurons. Here the authors differentiate mouse embryonic stem cells into neurons, and analyze the local transcriptome, proteome, and translated transcriptome in their cell bodies and neurites, providing a unique resource for future studies on neuronal polarity.

  9. Characterization of BASP1-mediated neurite outgrowth.

    PubMed

    Korshunova, Irina; Caroni, Pico; Kolkova, Kateryna; Berezin, Vladimir; Bock, Elisabeth; Walmod, Peter S

    2008-08-01

    The brain acid-soluble protein BASP1 (CAP-23, NAP-22) belongs to the family of growth-associated proteins, which also includes GAP-43, a protein recently shown to regulate neural cell adhesion molecule (NCAM)-mediated neurite outgrowth. Here, the effects of BASP1 overexpression were investigated in PC12E2 cells and primary hippocampal neurons. BASP1 overexpression stimulated neurite outgrowth in both cell types. The effects of BASP1 and trans-homophilic NCAM interactions were additive, and BASP1-induced neurite outgrowth was not inhibited by ectopic expression of cytoplasmic NCAM domains. Furthermore, inhibition of signaling via the fibroblast growth factor receptor, Src-family nonreceptor tyrosine kinases, protein kinase C, or GSK3beta, and expression of constructs of the cytoskeletal proteins spectrin and tau inhibited NCAM- but not BASP1-induced neurite outgrowth. Expression of BASP1 mutated at the serine-5 phosphorylation site stimulated neurite outgrowth to a degree comparable to that observed in response to overexpression of wild-type BASP1, whereas expression of BASP1 mutated at the myristoylation site at glycine-1 completely abrogated the stimulatory effects of the protein on neurite outgrowth. Finally, coexpression experiments with dominant negative and wild-type versions of GAP-43 and BASP1 demonstrated that the two proteins could substitute for each other with respect to induction of NCAM-independent neurite outgrowth, whereas BASP1 was unable to replace the stimulatory effect of GAP-43 on NCAM-mediated neurite outgrowth. These observations demonstrate that BASP1 and GAP-43 have overlapping, but not identical, functions in relation to neurite outgrowth and indicate that the main function of BASP1 is to regulate the organization and morphology of the plasma membrane.

  10. A Dynamical Approach Toward Understanding Mechanisms of Team Science: Change, Kinship, Tension, and Heritage in a Transdisciplinary Team

    PubMed Central

    2013-01-01

    Abstract Since the concept of team science gained recognition among biomedical researchers, social scientists have been challenged with investigating evidence of team mechanisms and functional dynamics within transdisciplinary teams. Identification of these mechanisms has lacked substantial research using grounded theory models to adequately describe their dynamical qualities. Research trends continue to favor the measurement of teams by isolating occurrences of production over relational mechanistic team tendencies. This study uses a social constructionist‐grounded multilevel mixed methods approach to identify social dynamics and mechanisms within a transdisciplinary team. A National Institutes of Health—funded research team served as a sample. Data from observations, interviews, and focus groups were qualitatively coded to generate micro/meso level analyses. Social mechanisms operative within this biomedical scientific team were identified. Dynamics that support such mechanisms were documented and explored. Through theoretical and emergent coding, four social mechanisms dominated in the analysis—change, kinship, tension, and heritage. Each contains relational social dynamics. This micro/meso level study suggests such mechanisms and dynamics are key features of team science and as such can inform problems of integration, praxis, and engagement in teams. PMID:23919361

  11. A dynamical approach toward understanding mechanisms of team science: change, kinship, tension, and heritage in a transdisciplinary team.

    PubMed

    Lotrecchiano, Gaetano R

    2013-08-01

    Since the concept of team science gained recognition among biomedical researchers, social scientists have been challenged with investigating evidence of team mechanisms and functional dynamics within transdisciplinary teams. Identification of these mechanisms has lacked substantial research using grounded theory models to adequately describe their dynamical qualities. Research trends continue to favor the measurement of teams by isolating occurrences of production over relational mechanistic team tendencies. This study uses a social constructionist-grounded multilevel mixed methods approach to identify social dynamics and mechanisms within a transdisciplinary team. A National Institutes of Health-funded research team served as a sample. Data from observations, interviews, and focus groups were qualitatively coded to generate micro/meso level analyses. Social mechanisms operative within this biomedical scientific team were identified. Dynamics that support such mechanisms were documented and explored. Through theoretical and emergent coding, four social mechanisms dominated in the analysis-change, kinship, tension, and heritage. Each contains relational social dynamics. This micro/meso level study suggests such mechanisms and dynamics are key features of team science and as such can inform problems of integration, praxis, and engagement in teams.

  12. Surface Tension and Capillary Rise

    ERIC Educational Resources Information Center

    Walton, Alan J.

    1972-01-01

    Discussion of the shortcomings of textbook explanations of surface tension, distinguishing between concepts of tension and capillary rise. The arguments require only a clear understanding of Newtonian mechanics, notably potential energy. (DF)

  13. In vitro study of the impact of mechanical tension on the dermal fibroblast phenotype in the context of skin wound healing.

    PubMed

    Rolin, Gwenae L; Binda, Delphine; Tissot, Marion; Viennet, Céline; Saas, Philippe; Muret, Patrice; Humbert, Philippe

    2014-11-07

    Skin wound healing is finely regulated by both matrix synthesis and degradation which are governed by dermal fibroblast activity. Actually, fibroblasts synthesize numerous extracellular matrix proteins (i.e., collagens), remodeling enzymes and their inhibitors. Moreover, they differentiate into myofibroblasts and are able to develop endogenous forces at the wound site. Such forces are crucial during skin wound healing and have been widely investigated. However, few studies have focused on the effect of exogenous mechanical tension on the dermal fibroblast phenotype, which is the objective of the present paper. To this end, an exogenous, defined, cyclic and uniaxial mechanical strain was applied to fibroblasts cultured as scratch-wounded monolayers. Results showed that fibroblasts' response was characterized by both an increase in procollagen type-I and TIMP-1 synthesis, and a decrease in MMP-1 synthesis. The monitoring of scratch-wounded monolayers did not show any decrease in kinetics of the filling up when mechanical tension was applied. Additional results obtained with proliferating fibroblasts and confluent monolayer indicated that mechanical tension-induced response of fibroblasts depends on their culture conditions. In conclusion, mechanical tension leads to the differentiation of dermal fibroblasts and may increase their wound-healing capacities. So, the exogenous uniaxial and cyclic mechanical tension reported in the present study may be considered in order to improve skin wound healing. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Quantitative analysis of surface tension of liquid nano-film with thickness: Two stage stability mechanism, molecular dynamics and thermodynamics approach

    NASA Astrophysics Data System (ADS)

    Peng, Tiefeng; Li, Qibin; Chen, Jie; Gao, Xuechao

    2016-11-01

    The effects of thickness on surface tension of aqueous nano-films under the same lateral size were studied by molecular dynamics (MD) simulations. The surface tension was found to decrease with decreasing thickness when film thickness is below 1.5 nm. Between 4 and 1.5 nm, the trend is for the surface tension to decrease but this is not as significant as between 1.5 and 1.2 nm. For the surface tension of salt nano-films, with low temperatures resulting in monotonous decreasing with thickness, while high temperature (e.g. 479 K) exhibited a first increase then decrease for surface tension with thickness. Filippini et al. (2014) suggested that surface tension is constant with the thickness as long as the sheet remains in one piece, also the decrease observed and as proposed by Werth et al. (2013) is not due to a confinement effect on Lennard-Jones systems. However, in this study for aqueous nano-films, a two stage mechanism was proposed to interpret this effect, for which the stability was classified according to thickness range and validated by disjoining pressure. The results are important in describing the role of surface tension in determining the behaviour of disjoining pressure.

  15. Tension-induced tunable corrugation in bio-inspired two-phase soft composite materials: mechanisms and implications

    NASA Astrophysics Data System (ADS)

    Elbanna, Ahmed; Chen, Qianli

    We numerically investigate the elastic deformation response of a two-phase bio-inspired soft composite material under externally applied concentric tension using the finite element method. We show that by carefully designing the inclusion pattern it is possible to induce corrugations normal to the direction of stretch. By stacking 1D composite fibers to form 2D membranes, these corrugations collectively lead to the formation of membrane channels with shapes and sizes that are tunable by the level of stretch. Furthermore, we show that by using specific inclusion patterns in laminated plates, it is possible to create pop-ups and troughs enabling the development of complex 3D geometries from planar construction. We have found that the corrugation amplitude increases with the stiffness of inclusion and its eccentricity from the tension axis. We discuss the mechanisms leading to the development of corrugations as well as its different implications. We discuss applications for this design in a variety of fields including tunable band gap formation, surface roughness controllability, auxetic materials and toughness enhancement via programmable evolving geometrical effects..

  16. Mechanical stress on tensioned wires at direct and indirect loading: a biomechanical study on the Ilizarov external fixator.

    PubMed

    Gessmann, Jan; Jettkant, Birger; Schildhauer, Thomas Armin; Seybold, Dominik

    2011-10-01

    The biomechanical effect of indirect weight loading with the Ilizarov ring fixator using a weight-bearing platform has not yet been investigated. The problem of wire loosening and breakage occurs more frequently when patients are mobilised with a weight-bearing platform. Therefore, the aim of this research was to compare the influence of direct and indirect weight loading on the tensioned wires. A universal testing machine (UTS, Germany) was used in this study. A composite tibia model with a standard four-ring Ilizarov fixator and 1.8-mm wires in anatomical position was used to simulate a clinical situation. Wire strain was measured with two strain gauges positioned at the ring-wire interface of each wire. After a standardised 2-mm mid-diaphyseal osteotomy, an axial load of up to 1000 N was applied to the bone; the different methods of weight loading were evaluated in two experimental set-ups. A higher axial load was necessary to achieve an osteotomy gap closure at indirect loading. Mechanical stress on the tensioned wires was 400% higher on the proximal wires and 250% higher on the distal wires at a maximum axial loading of 1000 N. Mechanical stress remained on the wires in indirect loading, even after bone end contact, and led to excessive stress under higher weight-bearing amounts. There is a substantial change in the biomechanical characteristics of the Ilizarov ring fixator when mobilising a patient with a weight-bearing platform. The considerable higher mechanical stress on the wires needs to be considered when patients are mobilised with a weight-bearing platform. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Design of an adaptive-passive dynamic vibration absorber composed of a string-mass system equipped with negative stiffness tension adjusting mechanism

    NASA Astrophysics Data System (ADS)

    Acar, M. A.; Yilmaz, C.

    2013-01-01

    In this study, a new adaptive-passive dynamic vibration absorber design is discussed. The proposed design is composed of a string under variable tension with a central mass attachment as an undamped dynamic vibration absorber (DVA), a negative stiffness mechanism as a string tension adjustment aid and a tuning controller to make it adaptive. The dependency of the natural frequencies of this system on the string tension is determined analytically and verified using the finite element method. It is analytically shown that with the help of a negative stiffness element, the tuning force requirement is almost zero throughout the whole operation range. A string tension adjustment algorithm is proposed, which tunes the DVA system depending on the magnitude and frequency of the most dominant component of the vibration signal. Finally, a prototype of the system is built and a series of experiments are conducted on the prototype that validate the analytical and numerical calculations.

  18. Mechanical and structural contribution of non-fibrillar matrix in uniaxial tension: a collagen-agarose co-gel model.

    PubMed

    Lake, Spencer P; Barocas, Victor H

    2011-07-01

    The mechanical role of non-fibrillar matrix and the nature of its interaction with the collagen network in soft tissues remain poorly understood, in part because of the lack of a simple experimental model system to quantify these interactions. This study's objective was to examine mechanical and structural properties of collagen-agarose co-gels, utilized as a simplified model system, to understand better the relationships between the collagen network and non-fibrillar matrix. We hypothesized that the presence of agarose would have a pronounced effect on microstructural reorganization and mechanical behavior. Samples fabricated from gel solutions containing 1.0 mg/mL collagen and 0, 0.125, or 0.25% w/v agarose were evaluated via scanning electron microscopy, incremental tensile stress-relaxation tests, and polarized light imaging. While the incorporation of agarose did not dramatically alter collagen network morphology, agarose led to concentration-dependent changes in mechanical and structural properties. Specifically, resistance of co-gels to volume change corresponded with differences in fiber reorientation and elastic/viscoelastic mechanics. Results demonstrate strong relationships between tissue properties and offer insight into behavior of tissues of varying Poisson's ratio and fiber kinematics. Results also suggest that non-fibrillar material may have significant effects on properties of artificial and native tissues even in tension, which is generally assumed to be collagen dominated.

  19. “Spatial Mapping of the Neurite and Soma Proteomes Reveals a Functional Cdc42/Rac Regulatory Network”

    SciTech Connect

    Pertz, Olivier C.; Wang, Yingchun; Yang, Feng; Wang, Wei; gay, laurie J.; Gritsenko, Marina A.; Clauss, Therese RW; Anderson, David J.; Liu, Tao; Auberry, Kenneth J.; Camp, David G.; Smith, Richard D.; Klemke, Richard L.

    2008-02-12

    Neurite extension and growth cone navigation are guided by extracellular cues that control cytoskeletal rearrangements. However, understanding the complex signaling mechanisms that mediate neuritogenesis has been limited by the inability to biochemically separate the neurite and soma for spatial proteomic and bioinformatic analyses. Here, we apply global proteome profiling in combination with a novel neurite purification methodology for comparative analysis of the soma and neurite proteomes of neuroblastoma cells. The spatial relationship of 4855 proteins were mapped revealing networks of signaling proteins that control integrins, the actin cytoskeleton, and axonal guidance in the extending neurite. Bioinformatics and functional analyses revealed a spatially compartmentalized Rac/Cdc42 signaling network that operates in conjunction with multiple GEFs and GAPs to control neurite formation. Interestingly, RNA interference experiments revealed that the different GEFs and GAPs regulate specialized functions during neurite formation including neurite growth and retraction kinetics, cytoskeletal organization, and cell polarity. Our findings provide insight into the spatial organization of signaling networks that enable neuritogenesis and provide a comprehensive system-wide profile of proteins that mediate this process including those that control Rac and Cdc42 signaling.

  20. Experimental and numerical thermo-mechanical analysis of shape memory alloy subjected to tension with various stress and strain rates

    NASA Astrophysics Data System (ADS)

    Dunić, V.; Pieczyska, E. A.; Tobushi, H.; Staszczak, M.; Slavković, R.

    2014-05-01

    TiNi shape memory alloy (SMA) is experimentally and numerically investigated in tension tests under different loading rates. The thermomechanical behaviour of the SMA, related to the stress-induced martensitic transformation (SIMT) noticed during the experimental tests, is analysed and the observations are considered for numerical analysis. Initiation, development and saturation of the SIMT are monitored by a fast and sensitive infrared camera. The estimated temperature changes of the SMA sample, related to the exothermic martensitic forward and endothermic reverse transformation, have been analysed with the focus on the rate-dependent response and on the influence of the heat transfer on the mechanical behaviour. The effectively modified constitutive model, proposed by Lagoudas, is implemented in structural PAK finite element method (FEM) software and is thermomechanically coupled with the heat transfer FEM software in a partitioned approach. The experimental results are quantitatively and qualitatively reproduced by the numerical FEM model, which verifies the efficiency and accuracy of the proposed investigation method.

  1. CB1 cannabinoid receptor-mediated neurite remodeling in mouse neuroblastoma N1E-115 cells.

    PubMed

    Zhou, D; Song, Z H

    2001-08-15

    The morphological remodeling of neuronal cells influences neurogenesis and brain functions. We hypothesize that psychoactive and neurotoxic effects of cannabinoids may be mediated, at least in part, by their morphoregulatory activities. In the present study, mouse neuroblastoma N1E-115 cells were used as an in vitro model to investigate cannabinoid-induced neurite remodeling effects and to identify the involvement of cannabinoid receptors in this neurite remodeling process. Using reverse transcription-polymerase chain reaction and immunofluorescence microscopy, the endogenously expressed CB1, but not CB2, cannabinoid receptors were detected in morphologically differentiated N1E-115 cells. Activation of these natively expressed CB1 cannabinoid receptors by cannabinoid agonist HU-210 led to a concentration-dependent inhibition of adenylate cyclase activity. Importantly, HU-210 treatment induced neurite retraction in a concentration-dependent manner. Pretreatment of N1E-115 cells with a CB1 antisense oligodeoxynucleotide (ODN) suppressed HU-210-induced inhibition of forskolin-stimulated cAMP accumulation, indicating that the knocking down of functional CB1 cannabinoid receptor expression was achieved. Antisense ODN pretreatment also abolished HU-210-induced neurite retraction, demonstrating the involvement of CB1 cannabinoid receptors in mediating the neurite remodeling effects of HU-210. In addition, reversing HU-210-induced intracellular cAMP declination by 8-Br-cAMP partially prevented HU-210-induced neurite retraction, indicating the involvement of cAMP-dependent signaling pathways in mediating the neurite remodeling function of CB1 cannabinoid receptors in N1E-115 cells. These data demonstrate that neurite remodeling is a newly discovered function of CB1 cannabinoid receptors. This morphoregulatory function of CB1 cannabinoid receptors might be a new mechanism that mediates the psychoactive and neurotoxic effects of cannabinoids in developing and adult brain.

  2. Pullout problem and fracture mechanism of quasi-brittle material reinforced with discontinous aligned fibers subjected to uniaxial tension

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng-Jang

    The objective of this research is to characterize the postpeak pseudo strain-hardening behavior of the discontinuous aligned fiber composites subjected to uniaxial tension. In order to fully understand the fiber axial force-debonding relationship, fiber pullout problem was first investigated. Unlike most models this theory assumes a triangularly distributed interface shear stress. Besides, R-curve approach was adopted to evaluate the maximum pullout load. In quasi-brittle materials when the value of energy release rate G increases with the applied load, the value of crack resistance R also increases. As a result, the equality of G and R can only serve as the necessary condition for crack propagation. In order to further distinguish stable and unstable crack propagation, a second condition must be included. Namely, the first derivatives of G and R must also equal to each other for the onset of unstable crack propagation. The applied load corresponding to this status is assumed to be the maximum pullout load the fiber can sustain. The corresponding debond length is referred to critical debond length ldc. It was found that ldc increases with embedment length le. This model reproduced the experimental results pretty well. The same concept of R-curve was adopted to investigate the fracture mechanism of the uniaxial tension problem. While determining strain energy of the fiber reinforced composite, equivalent inclusion method and Mori-Tanaka theory was utilized. Again, whenever the above two conditions are satisfied simultaneously, unstable crack propagation initiates. However, are the fibers being pulled out or is there another unstable crack propagation? The comparison of the force sustained by all the fibers in the entire cross section with its allowable value sets the criterion. Besides, unlike most models, this model takes account of the impact of fiber distribution. Thus a model distinguishing single cracking from multiple cracking fracture mechanism has been

  3. SRRM4-dependent neuron-specific alternative splicing of protrudin transcripts regulates neurite outgrowth

    PubMed Central

    Ohnishi, Takafumi; Shirane, Michiko; Nakayama, Keiichi I.

    2017-01-01

    Alternative splicing gives rise to diversity of the proteome, and it is especially prevalent in the mammalian nervous system. Indeed, many factors that control the splicing process govern nervous system development. Among such factors, SRRM4 is an important regulator of aspects of neural differentiation including neurite outgrowth. The mechanism by which SRRM4 regulates neurite outgrowth has remained poorly understood, however. We now show that SRRM4 regulates the splicing of protrudin gene (Zfyve27) transcripts in neuronal cells. SRRM4 was found to promote splicing of protrudin pre-mRNA so as to include a microexon (exon L) encoding seven amino acids in a neuron-specific manner. The resulting protein (protrudin-L) promotes neurite outgrowth during neurogenesis. Depletion of SRRM4 in Neuro2A cells impaired inclusion of exon L in protrudin mRNA, resulting in the generation of a shorter protein isoform (protrudin-S) that is less effective at promoting neurite extension. SRRM4 was found to recognize a UGC motif that is located immediately upstream of exon L and is necessary for inclusion of exon L in the mature transcript. Deletion of exon L in Neuro2A or embryonic stem cells inhibited neurite outgrowth. Our results suggest that SRRM4 controls neurite outgrowth through regulation of alternative splicing of protrudin transcripts. PMID:28106138

  4. Design of Hyaluronic Acid Hydrogels to Promote Neurite Outgrowth in Three Dimensions.

    PubMed

    Tarus, Dominte; Hamard, Lauriane; Caraguel, Flavien; Wion, Didier; Szarpak-Jankowska, Anna; van der Sanden, Boudewijn; Auzély-Velty, Rachel

    2016-09-28

    A hyaluronic acid (HA)-based extracellular matrix (ECM) platform with independently tunable stiffness and density of cell-adhesive peptide (RGD, arginine-glycine-aspartic acid) that mimics key biochemical and mechanical features of brain matrix has been designed. We demonstrated here its utility in elucidating ECM regulation of neural progenitor cell behavior and neurite outgrowth. The analysis of neurite outgrowth in 3-D by two-photon microscopy showed several important results in the development of these hydrogels. First, the ability of neurites to extend deeply into these soft HA-based matrices even in the absence of cell-adhesive ligand further confirms the potential of HA hydrogels for central nervous system (CNS) regeneration. Second, the behavior of hippocampal neural progenitor cells differed markedly between the hydrogels with a storage modulus of 400 Pa and those with a modulus of 800 Pa. We observed an increased outgrowth and density of neurites in the softest hydrogels (G' = 400 Pa). Interestingly, cells seeded on the surface of the hydrogels functionalized with the RGD ligand experienced an optimum in neurite outgrowth as a function of ligand density. Surprinsingly, neurites preferentially progressed inside the gels in a vertical direction, suggesting that outgrowth is directed by the hydrogel structure. This work may provide design principles for the development of hydrogels to facilitate neuronal regeneration in the adult brain.

  5. Self-aligned Schwann cell monolayers demonstrate an inherent ability to direct neurite outgrowth

    NASA Astrophysics Data System (ADS)

    Seggio, A. M.; Narayanaswamy, A.; Roysam, B.; Thompson, D. M.

    2010-08-01

    In vivo nerve guidance channel studies have identified Schwann cell (SC) presence as an integral factor in axonal number and extension in an injury site, and in vitro studies have provided evidence that oriented SCs can direct neurite outgrowth. However, traditional methods used to create oriented SC monolayers (e.g. micropatterns/microtopography) potentially introduce secondary guidance cues to the neurons that are difficult to de-couple. Although SCs expanded on uniform laminin-coated coverslips lack a global orientation, the monolayers contain naturally formed regions of locally oriented cells that can be used to investigate SC-mediated neurite guidance. In this work, novel image analysis techniques have been developed to quantitatively assess local neurite orientation with respect to the underlying regional orientation of the Schwann cell monolayer. Results confirm that, in the absence of any secondary guidance cues, a positive correlation exists between neurite outgrowth and regional orientation of the SC monolayer. Thus, SCs alone possess an inherent ability to direct neurite outgrowth, and expansion of the co-culture-based quantitative method described can be used to further deconstruct specific biomolecular mechanisms of neurite guidance.

  6. Surface tension of spherical drops from surface of tension

    SciTech Connect

    Homman, A.-A.; Bourasseau, E.; Malfreyt, P.; Strafella, L.; Ghoufi, A.

    2014-01-21

    The determination of surface tension of curved interfaces is a topic that raised many controversies during the last century. Explicit liquid-vapor interface modelling (ELVI) was unable up to now to reproduce interfacial behaviors in drops due to ambiguities in the mechanical definition of the surface tension. In this work, we propose a thermodynamic approach based on the location of surface of tension and its use in the Laplace equation to extract the surface tension of spherical interfaces from ELVI modelling.

  7. Fracture Mechanics of Thin, Cracked Plates Under Tension, Bending and Out-of-Plane Shear Loading

    NASA Technical Reports Server (NTRS)

    Zehnder, Alan T.; Hui, C. Y.; Potdar, Yogesh; Zucchini, Alberto

    1999-01-01

    Cracks in the skin of aircraft fuselages or other shell structures can be subjected to very complex stress states, resulting in mixed-mode fracture conditions. For example, a crack running along a stringer in a pressurized fuselage will be subject to the usual in-plane tension stresses (Mode-I) along with out-of-plane tearing stresses (Mode-III like). Crack growth and initiation in this case is correlated not only with the tensile or Mode-I stress intensity factor, K(sub I), but depends on a combination of parameters and on the history of crack growth. The stresses at the tip of a crack in a plate or shell are typically described in terms of either the small deflection Kirchhoff plate theory. However, real applications involve large deflections. We show, using the von-Karman theory, that the crack tip stress field derived on the basis of the small deflection theory is still valid for large deflections. We then give examples demonstrating the exact calculation of energy release rates and stress intensity factors for cracked plates loaded to large deflections. The crack tip fields calculated using the plate theories are an approximation to the actual three dimensional fields. Using three dimensional finite element analyses we have explored the relationship between the three dimensional elasticity theory and two dimensional plate theory results. The results show that for out-of-plane shear loading the three dimensional and Kirchhoff theory results coincide at distance greater than h/2 from the crack tip, where h/2 is the plate thickness. Inside this region, the distribution of stresses through the thickness can be very different from the plate theory predictions. We have also explored how the energy release rate varies as a function of crack length to plate thickness using the different theories. This is important in the implementation of fracture prediction methods using finite element analysis. Our experiments show that under certain conditions, during fatigue crack

  8. Mechanical Characterization of Immature Porcine Brainstem in Tension at Dynamic Strain Rates

    PubMed Central

    Zhao, Hui; Yin, Zhiyong; Li, Kui; Liao, Zhikang; Xiang, Hongyi; Zhu, Feng

    2016-01-01

    Background Many brain injury cases involve pediatric road traffic accidents, and among these, brainstem injury causes disastrous outcomes. A thorough understanding of the tensile characterization of immature brainstem tissue is crucial in modeling traumatic brain injury sustained by children, but limited experimental data in tension is available for the immature brain tissue at dynamic strain rates. Material/Methods We harvested brainstem tissue from immature pigs (about 4 weeks old, and at a developmental stage similar to that of human toddlers) as a byproduct from a local slaughter house and very carefully prepared the samples. Tensile tests were performed on specimens at dynamic strain rates of 2/s, 20/s, and 100/s using a biological material instrument. The constitutive models, Fung, Ogden, Gent, and exponential function, for immature brainstem tissue material property were developed for the recorded experimental data using OriginPro® 8.0 software. The t test was performed for infinitesimal shear modules. Results The curves of stress-versus-stretch ratio were convex in shape, and inflection points were found in all the test groups at the strain of about 2.5%. The average Lagrange stress of the immature brainstem specimen at the 30% strain at the strain rates of 2, 20, and 100/s was 273±114, 515±107, and 1121±197 Pa, respectively. The adjusted R-Square (R2) of Fung, Ogden, Gent, and exponential model was 0.820≤R2≤0.933, 0.774≤R2≤0.940, 0.650≤R2≤0.922, and 0.852≤R2≤0.981, respectively. The infinitesimal shear modulus of the strain energy functions showed a significant association with the strain rate (p<0.01). Conclusions The immature brainstem is a rate-dependent material in dynamic tensile tests, and the tissue becomes stiffer with increased strain rate. The reported results may be useful in the study of brain injuries in children who sustain injuries in road traffic accidents. Further research in more detail should be performed in the

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

    PubMed

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

    2013-01-01

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

  10. Contact force and mechanical loss of multistage cable under tension and bending

    NASA Astrophysics Data System (ADS)

    Ru, Yanyun; Yong, Huadong; Zhou, Youhe

    2016-10-01

    A theoretical model for calculating the stress and strain states of cabling structures with different loadings has been developed in this paper. We solve the problem for the first- and second-stage cable with tensile or bending strain. The contact and friction forces between the strands are presented by two-dimensional contact model. Several theoretical models have been proposed to verify the results when the triplet subjected to the tensile strain, including contact force, contact stresses, and mechanical loss. It is found that loadings will affect the friction force and the mechanical loss of the triplet. The results show that the contact force and mechanical loss are dependent on the twist pitch. A shorter twist pitch can lead to higher contact force, while the trend of mechanical loss with twist pitch is complicated. The mechanical loss may be reduced by adjusting the twist pitch reasonably. The present model provides a simple analysis method to investigate the mechanical behaviors in multistage-structures under different loads.

  11. Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression.

    PubMed

    Sirry, Mazin S; Butler, J Ryan; Patnaik, Sourav S; Brazile, Bryn; Bertucci, Robbin; Claude, Andrew; McLaughlin, Ron; Davies, Neil H; Liao, Jun; Franz, Thomas

    2016-10-01

    Understanding the passive mechanical properties of infarcted tissue at different healing stages is essential to explore the emerging biomaterial injection-based therapy for myocardial infarction (MI). Although rats have been widely used as animal models in such investigations, the data in literature that quantify the passive mechanical properties of rat heart infarcts is very limited. MI was induced in rats and hearts were harvested immediately (0 day), 7, 14 and 28 days after infarction onset. Left ventricle anterioapical samples were cut and underwent equibiaxial and non equibiaxial tension followed by uniaxial compression mechanical tests. Histological analysis was conducted to confirm MI and to quantify the size of the induced infarcts. Infarcts maintained anisotropy and the nonlinear biaxial and compressive mechanical behaviour throughout the healing phases with the circumferential direction being stiffer than the longitudinal direction. Mechanical coupling was observed between the two axes in all infarct groups. The 0, 7, 14 and 28 days infarcts showed 438, 693, 1048 and 1218kPa circumferential tensile moduli. The 28 day infarct group showed a significantly higher compressive modulus compared to the other infarct groups (p=0.0060, 0.0293, and 0.0268 for 0, 7 and 14 days groups). Collagen fibres were found to align in a preferred direction for all infarct groups supporting the observed mechanical anisotropy. The presented data are useful for developing material models for healing infarcts and for setting a baseline for future assessment of emerging mechanical-based MI therapies. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. The effects of morphological irregularity on the mechanical behavior of interdigitated biological sutures under tension.

    PubMed

    Liu, Lei; Jiang, Yunyao; Boyce, Mary; Ortiz, Christine; Baur, Jeffery; Song, Juha; Li, Yaning

    2017-06-14

    Irregular interdigitated morphology is prevalent in biological sutures in nature. Suture complexity index has long been recognized as the most important morphological parameter to govern the mechanical properties of biological sutures. However, the suture complexity index alone does not reflect all aspects of suture morphology. The goal of this investigation was to determine that besides suture complexity index, whether the degree of morphological irregularity of biological sutures has influences on the mechanical properties, and if there is any, how to quantify these influences. To explore these issues, theoretical and finite element (FE) suture models with the same suture complexity index but different levels of morphological irregularity were developed. The quasi-static stiffness, strength for damage initiation and post-failure process of irregular sutures were studied. It was shown that for the same suture complexity index, when the level of morphological irregularity increases, the overall strain to failure will increase while tensile stiffness is retained; also, the total energy to fracture increases with a sacrifice in strength to damage initiation. These results reveal that morphological irregularity is another important independent parameter to govern and balance the mechanical properties of biological sutures. Therefore, from the mechanics point of view, the prevalence of irregular suture morphology in nature is a merit, not a defect. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. PROGRESSIVE MECHANICAL BEHAVIOR OF HUMAN CORTICAL BONE IN TENSION FOR TWO AGE GROUPS

    PubMed Central

    Nyman, Jeffry S.; Roy, Anuradha; Reyes, Michael J.; Wang, Xiaodu

    2007-01-01

    The capacity of bone for post-yield energy dissipation decreases with age. To gain information on the cause of such changes, we examined the mechanical behavior of human cadaveric bone as a function of progressive deformation. In this study, tensile specimens from tibiae of 9 middle aged and 8 elderly donors were loaded till failure in an incremental and cyclic (load-dwell-unload-dwell-reload) scheme. The elastic modulus, maximum stress, permanent strain, stress relaxation, viscoelastic time constant, plastic strain energy, elastic release strain energy, and hysteresis energy were determined at incremental strains of each loading cycle. Experimental results showed that elderly bone failed at much lower strains compared to middle aged bone, but little age-related differences were observed in the mechanical behavior of bone until the premature failure of elderly bone. Energy dissipation and permanent strain appeared to linearly increase with increasing strain, while non-linear changes occurred in the modulus loss and stress relaxation/time constant with increasing strain. Such changes suggest that two distinct stages may exist in the progressive deformation of bone. In Stage I, rapid damage accumulation and increased involvement of collagen in load bearing appeared to dominate the mechanical behavior of bone with limited energy dissipation (<20% of total energy dissipated), whereas Stage II is dominated by continuous plastic deformation, accompanied by major energy dissipation through all three pathways till failure. This study suggests that damaging mechanisms in bone vary with deformation and age affects the post-yield mechanisms causing a significant decline in the capacity of aged bone to dissipate energy. PMID:18437693

  14. Mechanical Properties of Axons

    NASA Astrophysics Data System (ADS)

    Bernal, Roberto; Pullarkat, Pramod A.; Melo, Francisco

    2007-07-01

    The mechanical response of PC12 neurites under tension is investigated using a microneedle technique. Elastic response, viscoelastic relaxation, and active contraction are observed. The mechanical model proposed by Dennerll et al. [J. Cell Biol. 109, 3073 (1989).JCLBA30021-952510.1083/jcb.109.6.3073], which involves three mechanical devices—a stiff spring κ coupled with a Voigt element that includes a less stiff spring k and a dashpot γ—has been improved by adding a new element to describe the main features of the contraction of axons. This element, which represents the action of molecular motors, acts in parallel with viscous forces defining a global tension response of axons T against elongation rates δ˙k. Under certain conditions, axons show a transition from a viscoelastic elongation to active contraction, suggesting the presence of a negative elongation rate sensitivity in the curve T vs δ˙k.

  15. Mechanics of Composite Materials with Different Moduli in Tension and Compression

    DTIC Science & Technology

    1978-07-01

    Dynamics, and Materials Conference, Bethesda, Maryland, 3-5 April 1978, by Robert M. Jones and Jose C . F. Henneman . To appear in AIAA Journal. (24) "Biaxial...Canada, 16-20 April 1978, by Robert M. Jones and Jose C . F. Henneman . (25) "Analysis of Nonlinear Deformation Behavior of Laminated Fiber- Reinforced...CIVIL AND MECHANICAL ENGINEERING DEPA~I, T SCHOOL OF ENGINEERING AND APPLIED SCIENCE C .2 _SOUTHERN METHODIST UNIVEfttr DALLAS, TEXAS 75275 /FINAL

  16. chemo-mechanical coupling in water unsaturated domains: capillary tension and crystallization pressure

    NASA Astrophysics Data System (ADS)

    Hulin, Claudie; Mercury, Lionel

    2015-04-01

    Unsaturated zones are widely present in natural systems, such as soils, deep aquifers and building stones under wetting-drying cycles. Such porous media contains the three phases liquid, gas and solid and present specific physico-chemical processes or properties - as soluble salts precipitation or capillary water properties rise - have important impact on environmental issues since they are coupled with mechanical effects. The driving force of both phase transitions and capillarization is the decreasing relative humidity below the saturated value in the atmospheric air contacting the unsaturated materials. - Decreasing relative humidity leads to evaporation, creating local supersaturation and then driving crystallization. According to the usual theory of crystallization pressure, a confined growing crystal can exert a constraint against the pore wall, leading to its rupture if it exceeds the tensile strength of the pore material. This coupled chemo-mechanical process requires a nano-scale film of solution to hold between the crystal and the pore, which allows the solutes to diffuse and the solution not to precipitate despite increasing supersaturation. The repulsive effect between growing and host solids, ultimately increases the local pressure and may induce the host rupture - Capillarity has a large occurrence in unsaturated porous media and depends on pore radius and relative humidity of air. The capillary state makes the internal pressure of capillary water can drop down to negative values, meaning it is under tensile state and potentially exert traction on pore wall. These effects of chemo-mechanical coupling are observed using an experimental approach on three simplified natural analogues: porous membrane, borosilicate microcapillaries, and synthetic fluid inclusions. In the two former samples, sodium sulfates precipitates are induced through wetting-drying cycles and the role of both the capillarity and the crystallization pressure are observed. In the

  17. DA-9801 promotes neurite outgrowth via ERK1/2-CREB pathway in PC12 cells.

    PubMed

    Won, Jong Hoon; Ahn, Kyong Hoon; Back, Moon Jung; Ha, Hae Chan; Jang, Ji Min; Kim, Ha Hyung; Choi, Sang-Zin; Son, Miwon; Kim, Dae Kyong

    2015-01-01

    In the present study, we examined the mechanisms underlying the effect of DA-9801 on neurite outgrowth. We found that DA-9801 elicits its effects via the mitogen-activated protein kinase (MEK) extracellular signal-regulated kinase (ERK)1/2-cAMP response element-binding protein (CREB) pathway. DA-9801, an extract from a mixture of Dioscorea japonica and Dioscorea nipponica, was reported to promote neurite outgrowth in PC12 cells. The effects of DA-9801 on cell viability and expression of neuronal markers were evaluated in PC12 cells. To investigate DA-9801 action, specific inhibitors targeting the ERK signaling cascade were used. No cytotoxicity was observed in PC12 cells at DA-9801 concentrations of less than 30 µg/mL. In the presence of nerve growth factor (NGF, 2 ng/mL), DA-9801 promoted neurite outgrowth and increased the relative mRNA levels of neurofilament-L (NF-L), a marker of neuronal differentiation. The Raf-1 inhibitor GW5074 and MEK inhibitor PD98059 significantly attenuated DA-9801-induced neurite outgrowth. Additionally, the MEK1 and MEK2 inhibitor SL327 significantly attenuated the increase in the percentage of neurite-bearing PC12 cells induced by DA-9801 treatment. Conversely, the selective p38 mitogen-activated protein kinase inhibitor SB203580 did not attenuate the DA-9801 treatment-induced increase in the percentage of neurite-bearing PC12 cells. DA-9801 enhanced the phosphorylation of ERK1/2 and CREB in PC12 cells incubated with and without NGF. Pretreatment with PD98059 blocked the DA-9801-induced phosphorylation of ERK1/2 and CREB. In conclusion, DA-9801 induces neurite outgrowth by affecting the ERK1/2-CREB signaling pathway. Insights into the mechanism underlying this effect of DA-9801 may suggest novel potential strategies for the treatment of peripheral neuropathy.

  18. On the mechanical behavior of WS2 nanotubes under axial tension and compression.

    PubMed

    Kaplan-Ashiri, Ifat; Cohen, Sidney R; Gartsman, Konstantin; Ivanovskaya, Viktoria; Heine, Thomas; Seifert, Gotthard; Wiesel, Inna; Wagner, H Daniel; Tenne, Reshef

    2006-01-17

    The mechanical properties of materials and particularly the strength are greatly affected by the presence of defects; therefore, the theoretical strength ( approximately 10% of the Young's modulus) is not generally achievable for macroscopic objects. On the contrary, nanotubes, which are almost defect-free, should achieve the theoretical strength that would be reflected in superior mechanical properties. In this study, both tensile tests and buckling experiments of individual WS(2) nanotubes were carried out in a high-resolution scanning electron microscope. Tensile tests of MoS(2) nanotubes were simulated by means of a density-functional tight-binding-based molecular dynamics scheme as well. The combination of these studies provides a microscopic picture of the nature of the fracture process, giving insight to the strength and flexibility of the WS(2) nanotubes (tensile strength of approximately 16 GPa). Fracture analysis with recently proposed models indicates that the strength of such nanotubes is governed by a small number of defects. A fraction of the nanotubes attained the theoretical strength indicating absence of defects.

  19. Tension Strength, Failure Prediction and Damage Mechanisms in 2D Triaxial Braided Composites with Notch

    NASA Technical Reports Server (NTRS)

    Norman, Timothy L.; Anglin, Colin

    1995-01-01

    The unnotched and notched (open hole) tensile strength and failure mechanisms of two-dimensional (2D) triaxial braided composites were examined. The effect of notch size and notch position were investigated. Damage initiation and propagation in notched and unnotched coupons were also examined. Theory developed to predict the normal stress distribution near an open hole and failure for tape laminated composites was evaluated for its applicability to 2D triaxial braided textile composite materials. Four different fiber architectures were considered; braid angle, yarn and braider size, percentage of longitudinal yarns and braider angle varied. Tape laminates equivalent to textile composites were also constructed for comparison. Unnotched tape equivalents were stronger than braided textiles but exhibited greater notch sensitivity. Notched textiles and tape equivalents have roughly the same strength at large notch sizes. Two common damage mechanisms were found: braider yarn cracking and near notch longitudinal yarn splitting. Cracking was found to initiate in braider yarns in unnotched and notched coupons, and propagate in the direction of the braider yarns until failure. Damage initiation stress decreased with increasing braid angle. No significant differences in prediction of near notch strain between textile and tape equivalents could be detected for small braid angle, but the correlations were weak for textiles with large braid angle. Notch strength could not be predicted using existing anisotropic theory for braided textiles due to their insensitivity to notch.

  20. Echinococcal tension pneumothorax

    PubMed Central

    Bakir, Farhan; Al-Omeri, Muayyad M.

    1969-01-01

    Hydatid cyst is rarely mentioned among the causes of pneumothorax in text-books or monographs, especially those written in English. Five examples of tension pneumothorax secondary to ruptured hydatid cyst of the lung are reported: the mechanism of this tension effect and helpful diagnostic points are discussed. We think that surgical correction is the only satisfactory treatment of tension pneumothorax due to ruptured hydatid cyst: surgery is advocated in any suspected cyst as soon as it is discovered so as to avoid any such serious complication. Images PMID:5348321

  1. Flow in porous media, phase and ultralow interfacial tensions: Mechanisms of enhanced petroleum recovery

    SciTech Connect

    Davis, H.T.; Scriven, L.E.

    1991-07-01

    A major program of university research, longer-ranged and more fundamental in approach than industrial research, into basic mechanisms of enhancing petroleum recovery and into underlying physics, chemistry, geology, applied mathematics, computation, and engineering science has been built at Minnesota. The original focus was surfactant-based chemical flooding, but the approach taken was sufficiently fundamental that the research, longer-ranged than industrial efforts, has become quite multidirectional. Topics discussed are volume controlled porosimetry; fluid distribution and transport in porous media at low wetting phase saturation; molecular dynamics of fluids in ultranarrow pores; molecular dynamics and molecular theory of wetting and adsorption; new numerical methods to handle initial and boundary conditions in immiscible displacement; electron microscopy of surfactant fluid microstructure; low cost system for animating liquid crystallites viewed with polarized light; surfaces of constant mean curvature with prescribed contact angle.

  2. A Reduced Order Model of Force Displacement Curves for the Failure of Mechanical Bolts in Tension.

    SciTech Connect

    Moore, Keegan J.; Brake, Matthew Robert

    2015-12-01

    Assembled mechanical systems often contain a large number of bolted connections. These bolted connections (joints) are integral aspects of the load path for structural dynamics, and, consequently, are paramount for calculating a structure's stiffness and energy dissipation prop- erties. However, analysts have not found the optimal method to model appropriately these bolted joints. The complexity of the screw geometry causes issues when generating a mesh of the model. This report will explore different approaches to model a screw-substrate connec- tion. Model parameters such as mesh continuity, node alignment, wedge angles, and thread to body element size ratios are examined. The results of this study will give analysts a better understanding of the influences of these parameters and will aide in finding the optimal method to model bolted connections.

  3. Strain rate effects on the mechanical behavior of two Dual Phase steels in tension

    NASA Astrophysics Data System (ADS)

    Cadoni, E.; Singh, N. K.; Forni, D.; Singha, M. K.; Gupta, N. K.

    2016-05-01

    This paper presents an experimental investigation on the strain rate sensitivity of Dual Phase steel 1200 (DP1200) and Dual Phase steel 1400 (DP1400) under uni-axial tensile loads in the strain rate range from 0.001 s-1 to 600 s-1. These materials are advanced high strength steels (AHSS) having high strength, high capacity to dissipate crash energy and high formability. Flat sheet specimens of the materials having gauge length 10 mm, width 4 mm and thickness 2 mm (DP1200) and 1.25 mm (DP1400), are tested at room temperature (20∘C) on electromechanical universal testing machine to obtain their stress-strain relation under quasi-static condition (0.001 s-1), and on Hydro-Pneumatic machine and modified Hopkinson bar to study their mechanical behavior at medium (3 s-1, and 18 s-1) and high strain rates (200 s-1, 400 s-1, and 600 s-1) respectively. Tests under quasi-static condition are performed at high temperature (200∘C) also, and found that tensile flow stress is a increasing function of temperature. The stress-strain data has been analysed to determine the material parameters of the Cowper-Symonds and the Johnson-Cook models. A simple modification of the Johnson-Cook model has been proposed in order to obtain a better fit of tests at high temperatures. Finally, the fractographs of the broken specimens are taken by scanning electron microscope (SEM) to understand the fracture mechanism of these advanced high strength steels at different strain rates.

  4. Mechanisms and Modeling of Bake-Hardening Steels: Part I. Uniaxial Tension

    NASA Astrophysics Data System (ADS)

    Ballarin, V.; Soler, M.; Perlade, A.; Lemoine, X.; Forest, S.

    2009-06-01

    A physically based model for bake-hardening (BH) steels is developed suitable to predict the BH as well as the macroscopic behavior of strain-aged steels in tensile tests, such as the lower yield stress and the yield point elongation or Lüders strain. A description of the strain aging kinetics is given by considering two aging steps: Cottrell atmospheres formation and precipitation of coherent carbides. The modeling includes the effect of solute carbon content, aging time, temperature, and prestrain. Then, a numerical approach of Lüders phenomenon using finite element (FE) method codes is conducted. The strain aging model is eventually coupled with the previous numerical study thanks to a local mechanical behavior that schematically describes the local dislocation behavior. Simulations of tensile tests are performed and agree well with experiments carried out on aluminum-killed (AlK) and ULC BH steels, in terms of lower yield stress and yield point elongation. Effects of aging treatment, grain size, and strain rate on the macroscopic behavior are particularly enlightened.

  5. Pure neuritic leprosy: Current status and relevance.

    PubMed

    Rao, P Narasimha; Suneetha, Sujai

    2016-01-01

    Pure neuritic leprosy has always been an enigma due to its clinical and management ambiguities. Although only the Indian Association of Leprologist's classification recognizes 'pure neuritic leprosy' as a distinct sub group of leprosy, cases nonetheless are reported from various countries of Asia, Africa, South America and Europe, indicating its global relevance. It is important to maintain pure neuritic leprosy as a subgroup as it constitutes a good percentage of leprosy cases reported from India, which contributes to more than half of global leprosy numbers. Unfortunately, a high proportion of these patients present with Grade 2 disability at the time of initial reporting itself due to the early nerve involvement. Although skin lesions are absent by definition, when skin biopsies were performed from the skin along the distribution of the affected nerve, a proportion of patients demonstrated leprosy pathology, revealing sub-clinical skin involvement. In addition on follow-up, skin lesions are noted to develop in up to 20% of pure neuritic leprosy cases, indicating its progression to manifest cutaneous disease. Over the decades, the confirmation of diagnosis of pure neuritic leprosy has been subjective, however, with the arrival and use of high-resolution ultrasonography (HRUS) for nerve imaging, we have a tool not only to objectively measure and record the nerve thickening but also to assess the morphological alterations in the nerve including echo texture, fascicular pattern and vascularity. Management of pure neuritic leprosy requires multidrug therapy along with appropriate dose of systemic corticosteroids, for both acute and silent neuritis. Measures for pain relief, self-care of limbs and physiotherapy are important to prevent as well as manage disabilities in this group of patients.

  6. Diazinon and diazoxon impair the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons

    PubMed Central

    Pizzurro, Daniella M.; Dao, Khoi; Costa, Lucio G.

    2014-01-01

    Evidence from in vivo and epidemiological studies suggests that organophosphorus insecticides (OPs) are developmental neurotoxicants, but possible underlying mechanisms are still unclear. Astrocytes are increasingly recognized for their active role in normal neuronal development. This study sought to investigate whether the widely-used OP diazinon (DZ), and its oxygen metabolite diazoxon (DZO), would affect glial-neuronal interactions as a potential mechanism of developmental neurotoxicity. Specifically, we investigated the effects of DZ and DZO on the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons. The results show that both DZ and DZO adversely affect astrocyte function, resulting in inhibited neurite outgrowth in hippocampal neurons. This effect appears to be mediated by oxidative stress, as indicated by OP-induced increased reactive oxygen species production in astrocytes and prevention of neurite outgrowth inhibition by antioxidants. The concentrations of OPs were devoid of cytotoxicity, and cause limited acetylcholinesterase inhibition in astrocytes (18 and 25% for DZ and DZO, respectively). Among astrocytic neuritogenic factors, a most important one is the extracellular matrix protein fibronectin. DZ and DZO decreased levels of fibronectin in astrocytes, and this effect was also attenuated by antioxidants. Underscoring the importance of fibronectin in this context, adding exogenous fibronectin to the co-culture system successfully prevented inhibition of neurite outgrowth caused by DZ and DZO. These results indicate that DZ and DZO increase oxidative stress in astrocytes, and this in turn modulates astrocytic fibronectin, leading to impaired neurite outgrowth in hippocampal neurons. PMID:24342266

  7. Applied electric field enhances DRG neurite growth: influence of stimulation media, surface coating and growth supplements

    NASA Astrophysics Data System (ADS)

    Wood, Matthew D.; Willits, Rebecca Kuntz

    2009-08-01

    Electrical therapies have been found to aid repair of nerve injuries and have been shown to increase and direct neurite outgrowth during stimulation. This enhanced neural growth existed even after the electric field (EF) or stimulation was removed, but the factors that may influence the enhanced growth, such as stimulation media or surface coating, have not been fully investigated. This study characterized neurite outgrowth and branching under various conditions: EF magnitude and application time, ECM surface coating, medium during EF application and growth supplements. A uniform, low-magnitude EF (24 or 44 V m-1) was applied to dissociated chick embryo dorsal root ganglia seeded on collagen or laminin-coated surfaces. During the growth period, cells were either exposed to NGF or N2, and during stimulation cells were exposed to either unsupplemented media (Ca2+) or PBS (no Ca2+). Parallel controls for each experiment included cells exposed to the chamber with no stimulation and cells remaining outside the chamber. After brief electrical stimulation (10 min), neurite length significantly increased 24 h after application for all conditions studied. Of particular interest, increased stimulation time (10-100 min) further enhanced neurite length on laminin but not on collagen surfaces. Neurite branching was not affected by stimulation on any surface, and no preferential growth of neurites was noted after stimulation. Overall, the results of this report suggest that short-duration electric stimulation is sufficient to enhance neurite length under a variety of conditions. While further data are needed to fully elucidate a mechanism for this increased growth, these data suggest that one focus of those investigations should be the interaction between the growth cone and the substrata.

  8. Waves of actin and microtubule polymerization drive microtubule-based transport and neurite growth before single axon formation

    PubMed Central

    Winans, Amy M; Collins, Sean R; Meyer, Tobias

    2016-01-01

    Many developing neurons transition through a multi-polar state with many competing neurites before assuming a unipolar state with one axon and multiple dendrites. Hallmarks of the multi-polar state are large fluctuations in microtubule-based transport into and outgrowth of different neurites, although what drives these fluctuations remains elusive. We show that actin waves, which stochastically migrate from the cell body towards neurite tips, direct microtubule-based transport during the multi-polar state. Our data argue for a mechanical control system whereby actin waves transiently widen the neurite shaft to allow increased microtubule polymerization to direct Kinesin-based transport and create bursts of neurite extension. Actin waves also require microtubule polymerization, arguing that positive feedback links these two components. We propose that actin waves create large stochastic fluctuations in microtubule-based transport and neurite outgrowth, promoting competition between neurites as they explore the environment until sufficient external cues can direct one to become the axon. DOI: http://dx.doi.org/10.7554/eLife.12387.001 PMID:26836307

  9. The Selector Gene apterous and Notch Are Required to Locally Increase Mechanical Cell Bond Tension at the Drosophila Dorsoventral Compartment Boundary

    PubMed Central

    Michel, Marcus; Aliee, Maryam; Rudolf, Katrin; Bialas, Lisa; Jülicher, Frank; Dahmann, Christian

    2016-01-01

    The separation of cells with distinct fates and functions is important for tissue and organ formation during animal development. Regions of different fates within tissues are often separated from another along straight boundaries. These compartment boundaries play a crucial role in tissue patterning and growth by stably positioning organizers. In Drosophila, the wing imaginal disc is subdivided into a dorsal and a ventral compartment. Cells of the dorsal, but not ventral, compartment express the selector gene apterous. Apterous expression sets in motion a gene regulatory cascade that leads to the activation of Notch signaling in a few cell rows on either side of the dorsoventral compartment boundary. Both Notch and apterous mutant clones disturb the separation of dorsal and ventral cells. Maintenance of the straight shape of the dorsoventral boundary involves a local increase in mechanical tension at cell bonds along the boundary. The mechanisms by which cell bond tension is locally increased however remain unknown. Here we use a combination of laser ablation of cell bonds, quantitative image analysis, and genetic mutants to show that Notch and Apterous are required to increase cell bond tension along the dorsoventral compartment boundary. Moreover, clonal expression of the Apterous target gene capricious results in cell separation and increased cell bond tension at the clone borders. Finally, using a vertex model to simulate tissue growth, we find that an increase in cell bond tension at the borders of cell clones, but not throughout the cell clone, can lead to cell separation. We conclude that Apterous and Notch maintain the characteristic straight shape of the dorsoventral compartment boundary by locally increasing cell bond tension. PMID:27552097

  10. The Influence of Short-Chain Alcohols on Interfacial Tension, Mechanical Properties, Area/Molecule, and Permeability of Fluid Lipid Bilayers

    PubMed Central

    Ly, Hung V.; Longo, Marjorie L.

    2004-01-01

    We used micropipette aspiration to directly measure the area compressibility modulus, bending modulus, lysis tension, lysis strain, and area expansion of fluid phase 1-stearoyl, 2-oleoyl phosphatidylcholine (SOPC) lipid bilayers exposed to aqueous solutions of short-chain alcohols at alcohol concentrations ranging from 0.1 to 9.8 M. The order of effectiveness in decreasing mechanical properties and increasing area per molecule was butanol>propanol>ethanol>methanol, although the lysis strain was invariant to alcohol chain-length. Quantitatively, the trend in area compressibility modulus follows Traube's rule of interfacial tension reduction, i.e., for each additional alcohol CH2 group, the concentration required to reach the same area compressibility modulus was reduced roughly by a factor of 3. We convert our area compressibility data into interfacial tension values to: confirm that Traube's rule is followed for bilayers; show that alcohols decrease the interfacial tension of bilayer-water interfaces less effectively than oil-water interfaces; determine the partition coefficients and standard Gibbs adsorption energy per CH2 group for adsorption of alcohol into the lipid headgroup region; and predict the increase in area per headgroup as well as the critical radius and line tension of a membrane pore for each concentration and chain-length of alcohol. The area expansion predictions were confirmed by direct measurements of the area expansion of vesicles exposed to flowing alcohol solutions. These measurements were fitted to a membrane kinetic model to find membrane permeability coefficients of short-chain alcohols. Taken together, the evidence presented here supports a view that alcohol partitioning into the bilayer headgroup region, with enhanced partitioning as the chain-length of the alcohol increases, results in chain-length-dependent interfacial tension reduction with concomitant chain-length-dependent reduction in mechanical moduli and membrane thickness. PMID

  11. Polyester with Pendent Acetylcholine-Mimicking Functionalities Promotes Neurite Growth.

    PubMed

    Wang, Shaofei; Jeffries, Eric; Gao, Jin; Sun, Lijie; You, Zhengwei; Wang, Yadong

    2016-04-20

    Successful regeneration of nerves can benefit from biomaterials that provide a supportive biochemical and mechanical environment while also degrading with controlled inflammation and minimal scar formation. Herein, we report a neuroactive polymer functionalized by covalent attachment of the neurotransmitter acetylcholine (Ach). The polymer was readily synthesized in two steps from poly(sebacoyl diglyceride) (PSeD), which previously demonstrated biocompatibility and biodegradation in vivo. Distinct from prior acetylcholine-biomimetic polymers, PSeD-Ach contains both quaternary ammonium and free acetyl moieties, closely resembling native acetylcholine structure. The polymer structure was confirmed via (1)H nuclear magnetic resonance and Fourier-transform infrared spectroscopy. Hydrophilicity, charge, and thermal properties of PSeD-Ach were determined by tensiometer, zetasizer, differential scanning calorimetry, and thermal gravimetric analysis, respectively. PC12 cells exhibited the greatest proliferation and neurite outgrowth on PSeD-Ach and laminin substrates, with no significant difference between these groups. PSeD-Ach yielded much longer neurite outgrowth than the control polymer containing ammonium but no the acetyl group, confirming the importance of the entire acetylcholine-like moiety. Furthermore, PSeD-Ach supports adhesion of primary rat dorsal root ganglions and subsequent neurite sprouting and extension. The sprouting rate is comparable to the best conditions from previous report. Our findings are significant in that they were obtained with acetylcholine-like functionalities in 100% repeating units, a condition shown to yield significant toxicity in prior publications. Moreover, PSeD-Ach exhibited favorable mechanical and degradation properties for nerve tissue engineering application. Humidified PSeD-Ach had an elastic modulus of 76.9 kPa, close to native neural tissue, and could well recover from cyclic dynamic compression. PSeD-Ach showed a gradual in

  12. Synergistic Effects of 3D ECM and Chemogradients on Neurite Outgrowth and Guidance: A Simple Modeling and Microfluidic Framework

    PubMed Central

    Srinivasan, Parthasarathy; Zervantonakis, Ioannis K.; Kothapalli, Chandrasekhar R.

    2014-01-01

    During nervous system development, numerous cues within the extracellular matrix microenvironment (ECM) guide the growing neurites along specific pathways to reach their intended targets. Neurite motility is controlled by extracellular signal sensing through the growth cone at the neurite tip, including chemoattractive and repulsive cues. However, it is difficult to regenerate and restore neurite tracts, lost or degraded due to an injury or disease, in the adult central nervous system. Thus, it is important to evaluate the dynamic interplay between ECM and the concentration gradients of these cues, which would elicit robust neuritogenesis. Such information is critical in understanding the processes involved in developmental biology, and in developing high-fidelity neurite regenerative strategies post-injury, and in drug discovery and targeted therapeutics for neurodegenerative conditions. Here, we quantitatively investigated this relationship using a combination of mathematical modeling and in vitro experiments, and determined the synergistic role of guidance cues and ECM on neurite outgrowth and turning. Using a biomimetic microfluidic system, we have shown that cortical neurite outgrowth and turning under chemogradients (IGF-1 or BDNF) within 3D scaffolds is highly regulated by the source concentration of the guidance cue and the physical characteristics of the scaffold. A mechanistic-driven partial differential equation model of neurite outgrowth has been proposed, which could also be used prospectively as a predictive tool. The parameters for the chemotaxis term in the model are determined from the experimental data using our microfluidic assay. Resulting model simulations demonstrate how neurite outgrowth was critically influenced by the experimental variables, which was further supported by experimental data on cell-surface-receptor expressions. The model results are in excellent agreement with the experimental findings. This integrated approach represents a

  13. Differential intensity-dependent effects of magnetic stimulation on the longest neurites and shorter dendrites in neuroscreen-1 cells

    NASA Astrophysics Data System (ADS)

    Lin, Ching-Yi; Huang, Whitney J.; Li, Kevin; Swanson, Roy; Cheung, Brian; Lin, Vernon W.; Lee, Yu-Shang

    2015-04-01

    Objective. Magnetic stimulation (MS) is a potential treatment for neuropsychiatric disorders. This study investigates whether MS-regulated neuronal activity can translate to specific changes in neuronal arborization and thus regulate synaptic activity and function. Approach. To test our hypotheses, we examined the effects of MS on neurite growth of neuroscreen-1 (NS-1) cells over the pulse frequencies of 1, 5 and 10 Hz at field intensities controlled via machine output (MO). Cells were treated with either 30% or 40% MO. Due to the nature of circular MS coils, the center region of the gridded coverslip (zone 1) received minimal (∼5%) electromagnetic current density while the remaining area (zone 2) received maximal (∼95%) current density. Plated NS-1 cells were exposed to MS twice per day for three days and then evaluated for length and number of neurites and expression of brain-derived neurotrophic factor (BDNF). Main results. We show that MS dramatically affects the growth of the longest neurites (axon-like) but does not significantly affect the growth of shorter neurites (dendrite-like). Also, MS-induced changes in the longest neurite growth were most evident in zone 1, but not in zone 2. MS effects were intensity-dependent and were most evident in bolstering longest neurite outgrowth, best seen in the 10 Hz MS group. Furthermore, we found that MS-increased BDNF expression and secretion was also frequency-dependent. Taken together, our results show that MS exerts distinct effects when different frequencies and intensities are applied to the neuritic compartments (longest neurite versus shorter dendrite(s)) of NS-1 cells. Significance. These findings support the concept that MS increases BDNF expression and signaling, which sculpts longest neurite arborization and connectivity by which neuronal activity is regulated. Understanding the mechanisms underlying MS is crucial for efficiently incorporating its use into potential therapeutic strategies.

  14. Acetylcholinesterase modulates neurite outgrowth on fibronectin.

    PubMed

    Giordano, C; Poiana, G; Augusti-Tocco, G; Biagioni, S

    2007-05-04

    Acetylcholinesterase (AChE) has been reported to be involved in the modulation of neurite outgrowth. To understand the role played by different domains, we transfected neuroblastoma cells with three constructs containing the invariant region of AChE, differing in the exon encoding the C-terminus and therefore in AChE cellular fate and localization. All isoforms increased neurite extension, suggesting the involvement of the invariant domain [A. De Jaco, G. Augusti-Tocco, S. Biagioni, Alternative AChE molecular forms exhibit similar ability to induce neurite outgrowth, J. Neurosci. Res. 70 (2002) 756-765]. The peripheral anionic site (PAS) is encoded by invariant exons and represents the domain involved in non-cholinergic functions of AChE. Masking of PAS with fasciculin results in a significant decrease of neurite outgrowth in all clones overexpressing AChE. A strong reduction was also observed when clones were cultured on fibronectin. Treatment of clones with fasciculin, therefore masking PAS, abolished the fibronectin-induced reduction. The inhibition of the catalytic site cannot revert the fibronectin effect. Finally, when clones were cultured on fibronectin in the presence of heparin, a ligand of fibronectin, the inhibitory effect was completely reversed. Our results indicate that PAS could directly or indirectly mediate AChE/fibronectin interactions.

  15. NIF (neurite-inducing factor): a novel peptide inducing neurite formation in PC12 cells.

    PubMed

    Wagner, J A

    1986-01-01

    Neurite-inducing factor (NIF) is a novel protein that has been partially purified from mouse submaxillary glands. NIF induces neurite formation in PC12 pheochromocytoma cells, and the NIF-induced neurites are indistinguishable from NGF-induced neurites in both their morphology and the time course of their formation. Neurite-inducing activity can be recovered at a position corresponding to a molecular weight of 20,000 Da after fractionation of partially purified preparations via SDS-PAGE. Partially purified preparations of NIF are about half as potent as pure beta NGF, and since the neurite-inducing activity does not correspond to any of the major proteins in this fraction, specific activity of purified NIF will probably be significantly greater than the 60 ng/ml found for our partially purified material. NIF is distinct from beta NGF by four criteria: (1) antibodies to beta NGF can block the activity of beta NGF, but not the activity of NIF; (2) beta NGF can induce ornithine decarboxylase (ODC) in PC12 cells at concentrations significantly below those required to induce neurites, while NIF induces ODC only at concentrations greatly in excess of those required to induce neurite formation; (3) by the criterion of SDS-PAGE, there is insufficient beta NGF in our partially purified preparations of NIF to explain the biological activity of this fraction; and (4) the biological activity of NIF has a molecular weight (20,000 Da) that is distinct from beta NGF (13,000 Da). We conclude that NIF is probably a novel peptide that is very active in promoting morphological differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

  16. Neurite outgrowth inhibitors in gliotic tissue.

    PubMed

    Nieto-Sampedro, M

    1999-01-01

    Gliotic tissue is the major obstacle to axon regeneration after CNS injury. We designed tissue culture assays to search for molecules responsible for neurite outgrowth inhibition in gliotic tissue. All the inhibitory activity in injured brain tissue was located in a plasma membrane heparan-sulphate and condroitin-sulphate type-proteoglycan of apparent molecular weight 200 kDalton. The proteoglycan core protein (apparent MW 48,000 kD) was biologically inactive, whereas the glycosamine-glycan (GAG) chains accounted for the inhibitory activity. Because of its cell location and mode of induction, the inhibitor was called injured membrane proteoglycan, IMP. IMP prevented neurite outgrowth initiation when attached to the culture substrate and caused growth cone collapse when added in solution to neurons with already growing neurites. We concluded that IMP was responsible for preventing injured CNS fibre regeneration. Double-staining immunohistochemistry of normal and gliotic tissue with anti-IMP monoclonal antibodies together with glial and neuronal markers, permitted the unequivocal definition of inhibitor presenting cells by confocal microscopy. IMP-immunostaining in normal CNS was observed exclusively on neurons. However, after a lesion, immunostaining occurred primarily on intensely GFAP-positive reactive astrocytes, but not on OX-42 positive microglia. The availability of antibodies permitted rapid affinity-purification of the neurite inhibitor and comparison with similar molecules possibly expressed during development. IMP itself or a highly related form, was expressed in embryonic brain, reaching maximal expression around postnatal day 3 and decreasing strongly in normal adult tissue. Perinatal rat brain proteoglycans inhibited neurite outgrowth similarly, though not identically, to IMP. Our data suggest that perinatal membrane and injured membrane proteoglycans may differ in GAG composition. IMP-like immunoreactivity was also found in developing brain

  17. The impact of laminin on 3D neurite extension in collagen gels

    NASA Astrophysics Data System (ADS)

    Swindle-Reilly, Katelyn E.; Papke, Jason B.; Kutosky, Hannah P.; Throm, Allison; Hammer, Joshua A.; Harkins, Amy B.; Kuntz Willits, Rebecca

    2012-08-01

    The primary goal of this research was to characterize the effect of laminin on three-dimensional (3D) neurite growth. Gels were formed using type I collagen at concentrations of 0.4-2.0 mg mL-1 supplemented with laminin at concentrations of 0, 1, 10, or 100 µg mL-1. When imaged with confocal microscopy, laminin was shown to follow the collagen fibers; however, the addition of laminin had minimal effect on the stiffness of the scaffolds at any concentration of collagen. Individual neurons dissociated from E9 chick dorsal root ganglia were cultured in the gels for 24 h, and neurite lengths were measured. For collagen gels without laminin, a typical bimodal response of neurite outgrowth was observed, with increased growth at lower concentrations of collagen gel. However, alteration of the chemical nature of the collagen gel by the laminin additive shifted, or completely mitigated, the bimodal neurite growth response seen in gels without laminin. Expression of integrin subunits, α1, α3, α6 and β1, were confirmed by PCR and immunolabeling in the 3D scaffolds. These results provide insight into the interplay between mechanical and chemical environment to support neurite outgrowth in 3D. Understanding the relative impact of environmental factors on 3D nerve growth may improve biomaterial design for nerve cell regeneration.

  18. Hydrogel Design for Supporting Neurite Outgrowth and Promoting Gene Delivery to Maximize Neurite Extension

    PubMed Central

    Shepard, Jaclyn A.; Stevans, Alyson C.; Holland, Samantha; Wang, Christine E.; Shikanov, Ariella; Shea, Lonnie D.

    2012-01-01

    Hydrogels capable of gene delivery provide a combinatorial approach for nerve regeneration, with the hydrogel supporting neurite outgrowth and gene delivery inducing the expression of inductive factors. This report investigates the design of hydrogels that balance the requirements for supporting neurite growth with those requirements for promoting gene delivery. Enzymatically-degradable PEG hydrogels encapsulating dorsal root ganglia explants, fibroblasts, and lipoplexes encoding nerve growth factor were gelled within channels that can physically guide neurite outgrowth. Transfection of fibroblasts increased with increasing concentration of Arg-Gly-Asp (RGD) cell adhesion sites and decreasing PEG content. The neurite length increased with increasing RGD concentration within 10% PEG hydrogels, yet was maximal within 7.5% PEG hydrogels at intermediate RGD levels. Delivering lipoplexes within the gel produced longer neurites than culture in NGF-supplemented media or co-culture with cells exposed to DNA prior to encapsulation. Hydrogels designed to support neurite outgrowth and deliver gene therapy vectors locally may ultimately be employed to address multiple barriers that limit regeneration. PMID:22038654

  19. Transient neurites of retinal horizontal cells exhibit columnar tiling via homotypic interactions.

    PubMed

    Huckfeldt, Rachel M; Schubert, Timm; Morgan, Josh L; Godinho, Leanne; Di Cristo, Graziella; Huang, Z Josh; Wong, Rachel O L

    2009-01-01

    Sensory neurons with common functions are often nonrandomly arranged and form dendritic territories that show little overlap, or tiling. Repulsive homotypic interactions underlie such patterns in cell organization in invertebrate neurons. It is unclear how dendro-dendritic repulsive interactions can produce a nonrandom distribution of cells and their spatial territories in mammalian retinal horizontal cells, as mature horizontal cell dendrites overlap substantially. By imaging developing mouse horizontal cells, we found that these cells transiently elaborate vertical neurites that form nonoverlapping columnar territories on reaching their final laminar positions. Targeted cell ablation revealed that the vertical neurites engage in homotypic interactions that result in tiling of neighboring cells before the establishment of their dendritic fields. This developmental tiling of transient neurites correlates with the emergence of a nonrandom distribution of the cells and could represent a mechanism that organizes neighbor relationships and territories of neurons before circuit assembly.

  20. Arylsulfatase B modulates neurite outgrowth via astrocyte chondroitin-4-sulfate: dysregulation by ethanol.

    PubMed

    Zhang, Xiaolu; Bhattacharyya, Sumit; Kusumo, Handojo; Goodlett, Charles R; Tobacman, Joanne K; Guizzetti, Marina

    2014-02-01

    In utero ethanol exposure causes fetal alcohol spectrum disorders, associated with reduced brain plasticity; the mechanisms of these effects are not well understood, particularly with respect to glial involvement. Astrocytes release factors that modulate neurite outgrowth. We explored the hypothesis that ethanol inhibits neurite outgrowth by increasing the levels of inhibitory chondroitin sulfate proteoglycans (CSPGs) in astrocytes. Astrocyte treatment with ethanol inhibited the activity of arylsulfatase B (ARSB), the enzyme that removes sulfate groups from chondroitin-4-sulfate (C4S) and triggers the degradation of C4S, increased total sulfated glycosaminoglycans (GAGs), C4S, and neurocan core-protein content and inhibited neurite outgrowth in neurons cocultured with ethanol-treated astrocytes in vitro, effects reversed by treatment with recombinant ARSB. Ethanol also inhibited ARSB activity and increased sulfate GAG and neurocan levels in the developing hippocampus after in vivo ethanol exposure. ARSB silencing increased the levels of sulfated GAGs, C4S, and neurocan in astrocytes and inhibited neurite outgrowth in cocultured neurons, indicating that ARSB activity directly regulates C4S and affects neurocan expression. In summary, this study reports two major findings: ARSB modulates sulfated GAG and neurocan levels in astrocytes and astrocyte-mediated neurite outgrowth in cocultured neurons; and ethanol inhibits the activity of ARSB, increases sulfated GAG, C4S, and neurocan levels, and thereby inhibits astrocyte-mediated neurite outgrowth. An unscheduled increase in CSPGs in the developing brain may lead to altered brain connectivity and to premature decrease in neuronal plasticity and therefore represents a novel mechanism by which ethanol can exert its neurodevelopmental effects.

  1. Diazinon and diazoxon impair the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons

    SciTech Connect

    Pizzurro, Daniella M.; Dao, Khoi; Costa, Lucio G.

    2014-02-01

    Evidence from in vivo and epidemiological studies suggests that organophosphorus insecticides (OPs) are developmental neurotoxicants, but possible underlying mechanisms are still unclear. Astrocytes are increasingly recognized for their active role in normal neuronal development. This study sought to investigate whether the widely-used OP diazinon (DZ), and its oxygen metabolite diazoxon (DZO), would affect glial–neuronal interactions as a potential mechanism of developmental neurotoxicity. Specifically, we investigated the effects of DZ and DZO on the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons. The results show that both DZ and DZO adversely affect astrocyte function, resulting in inhibited neurite outgrowth in hippocampal neurons. This effect appears to be mediated by oxidative stress, as indicated by OP-induced increased reactive oxygen species production in astrocytes and prevention of neurite outgrowth inhibition by antioxidants. The concentrations of OPs were devoid of cytotoxicity, and cause limited acetylcholinesterase inhibition in astrocytes (18 and 25% for DZ and DZO, respectively). Among astrocytic neuritogenic factors, the most important one is the extracellular matrix protein fibronectin. DZ and DZO decreased levels of fibronectin in astrocytes, and this effect was also attenuated by antioxidants. Underscoring the importance of fibronectin in this context, adding exogenous fibronectin to the co-culture system successfully prevented inhibition of neurite outgrowth caused by DZ and DZO. These results indicate that DZ and DZO increase oxidative stress in astrocytes, and this in turn modulates astrocytic fibronectin, leading to impaired neurite outgrowth in hippocampal neurons. - Highlights: • DZ and DZO inhibit astrocyte-mediated neurite outgrowth in rat hippocampal neurons. • Oxidative stress is involved in inhibition of neuritogenesis by DZ and DZO. • DZ and DZO decrease expression of the neuritogenic

  2. Specification Report for TACOM Track Tensioning Programme

    DTIC Science & Technology

    1992-05-01

    design proceeds and further details are available. Mechanical Components Track Tensioning Actuator Type Equal area folded design Active area 100 (mm 2...92 Hose Type Steel braided P.T.F.E hoses with swaged end fittings Sizes: Front to rear distribution -12 Tensioner control valve to tensioner -10 min...Gas spring to tensioner -12 min Chosen supplier and type Aeroquip, AE 246 Tensioner Control Valve Type Two stage electrohydraulic servo valve Rated

  3. An algorithm for neurite outgrowth reconstruction

    NASA Technical Reports Server (NTRS)

    Weaver, Christina M.; Pinezich, John D.; Lindquist, W. Brent; Vazquez, Marcelo E.

    2003-01-01

    We present a numerical method which provides the ability to analyze digitized microscope images of retinal explants and quantify neurite outgrowth. Few parameters are required as input and limited user interaction is necessary to process an entire experiment of images. This eliminates fatigue related errors and user-related bias common to manual analysis. The method does not rely on stained images and handles images of variable quality. The algorithm is used to determine time and dose dependent, in vitro, neurotoxic effects of 1 GeV per nucleon iron particles in retinal explants. No neurotoxic effects are detected until 72 h after exposure; at 72 h, significant reductions of neurite outgrowth occurred at doses higher than 10 cGy.

  4. Detailed finite element analysis and preliminary study of the effects of friction and fastener pre-tension on the mechanical behavior of fastened built-up members

    NASA Astrophysics Data System (ADS)

    Bonachera Martin, Francisco Javier

    The characterization of fatigue resistance is one of the main concerns in structural engineering, a concern that is particularly important in the evaluation of existing bridge members designed or erected before the development of fatigue design provisions. The ability of a structural member to develop alternate load paths after the failure of a component is known as member-level or internal redundancy. In fastened built-up members, these alternate load paths are affected by the combination of fastener pre-tension and friction between the structural member components in contact. In this study, a finite element methodology to model and analyze riveted and bolted built-up members was developed in ABAQUS and validated with experimental results. This methodology was used to created finite element models of three fastened plates subjected to tension, in which the middle plate had failed, in order to investigate the fundamental effects of combined fastener pre-tension and friction on their mechanical behavior. Detailed finite element models of riveted and bolted built-up flexural members were created and analyze to understand the effect of fastener pre-tension in member-level redundancy and resistance to fatigue and fracture. The obtained results showed that bolted members are able to re-distribute a larger portion of the load away from the failing component into the rest of the member than riveted members, and that this transfer of load also took place over a smaller length. Superior pre-tension of bolts, in comparison to rivets, results in larger frictional forces that develop at the contact interfaces between components and constitute additional alternate load paths that increase member-level redundancy which increase the fatigue and fracture resistance of the structural member during the failure of one of its components. Although fatigue and fracture potential may be mitigated by compressive stresses developing around the fastener hole due to fastener pre-tension, it

  5. Synchronous symmetry breaking in neurons with different neurite counts.

    PubMed

    Wissner-Gross, Zachary D; Scott, Mark A; Steinmeyer, Joseph D; Yanik, Mehmet Fatih

    2013-01-01

    As neurons develop, several immature processes (i.e., neurites) grow out of the cell body. Over time, each neuron breaks symmetry when only one of its neurites grows much longer than the rest, becoming an axon. This symmetry breaking is an important step in neurodevelopment, and aberrant symmetry breaking is associated with several neuropsychiatric diseases, including schizophrenia and autism. However, the effects of neurite count in neuronal symmetry breaking have never been studied. Existing models for neuronal polarization disagree: some predict that neurons with more neurites polarize up to several days later than neurons with fewer neurites, while others predict that neurons with different neurite counts polarize synchronously. We experimentally find that neurons with different neurite counts polarize synchronously. We also show that despite the significant differences among the previously proposed models, they all agree with our experimental findings when the expression levels of the proteins responsible for symmetry breaking increase with neurite count. Consistent with these results, we observe that the expression levels of two of these proteins, HRas and shootin1, significantly correlate with neurite count. This coordinated symmetry breaking we observed among neurons with different neurite counts may be important for synchronized polarization of neurons in developing organisms.

  6. Synchronous Symmetry Breaking in Neurons with Different Neurite Counts

    PubMed Central

    Wissner-Gross, Zachary D.; Scott, Mark A.; Steinmeyer, Joseph D.; Yanik, Mehmet Fatih

    2013-01-01

    As neurons develop, several immature processes (i.e., neurites) grow out of the cell body. Over time, each neuron breaks symmetry when only one of its neurites grows much longer than the rest, becoming an axon. This symmetry breaking is an important step in neurodevelopment, and aberrant symmetry breaking is associated with several neuropsychiatric diseases, including schizophrenia and autism. However, the effects of neurite count in neuronal symmetry breaking have never been studied. Existing models for neuronal polarization disagree: some predict that neurons with more neurites polarize up to several days later than neurons with fewer neurites, while others predict that neurons with different neurite counts polarize synchronously. We experimentally find that neurons with different neurite counts polarize synchronously. We also show that despite the significant differences among the previously proposed models, they all agree with our experimental findings when the expression levels of the proteins responsible for symmetry breaking increase with neurite count. Consistent with these results, we observe that the expression levels of two of these proteins, HRas and shootin1, significantly correlate with neurite count. This coordinated symmetry breaking we observed among neurons with different neurite counts may be important for synchronized polarization of neurons in developing organisms. PMID:23408951

  7. Mesenchymal stem cell-derived exosomes from different sources selectively promote neuritic outgrowth.

    PubMed

    Lopez-Verrilli, M A; Caviedes, A; Cabrera, A; Sandoval, S; Wyneken, U; Khoury, M

    2016-04-21

    Mesenchymal stem cells (MSCs) obtained from bone marrow (BM) have been shown to promote neuronal growth and survival. However, the comparative effects of MSCs of different sources, including menstrual MSCs (MenSCs), BM, umbilical cord and chorion stem cells on neurite outgrowth have not yet been explored. Moreover, the modulatory effects of MSCs may be mediated by paracrine mechanisms, i.e. by molecules contained in the MSC secretome that includes soluble factors and extracellular vesicles such as microvesicles and/or exosomes. The biogenesis of microvesicles, characterized by a vesicle diameter of 50 to 1000 nm, involves membrane shedding while exosomes, of 30 to 100 nm in diameter, originate in the multivesicular bodies within cells. Both vesicle types, which can be harvested from the conditioned media of cell cultures by differential centrifugation steps, regulate the function of target cells due to their molecular content of microRNA, mRNA, proteins and lipids. Here, we compared the effect of human menstrual MSCs (MenSCs) mediated by cell-cell contact, by their total secretome or by secretome-derived extracellular vesicles on neuritic outgrowth in primary neuronal cultures. The contact of MenSCs with cortical neurons inhibited neurite outgrowth while their total secretome enhanced it. The extracellular vesicle fractions showed a distinctive effect: while the exosome-enriched fraction enhanced neurite outgrowth, the microvesicle-enriched fraction displayed an inhibitory effect. When we compared exosome fractions of different human MSC sources, MenSC exosomes showed superior effects on the growth of the longest neurite in cortical neurons and had a comparable effect to BM-SC exosomes on neurite outgrowth in dorsal root ganglia neurons. Thus, the growth-stimulating effects of exosomes derived from MenSCs as well as the opposing effects of both extracellular vesicle fractions provide important information regarding the potential use of MenSCs as therapeutic

  8. Optimizing neurotrophic factor combinations for neurite outgrowth

    NASA Astrophysics Data System (ADS)

    Deister, C.; Schmidt, C. E.

    2006-06-01

    Most neurotrophic factors are members of one of three families: the neurotrophins, the glial cell-line derived neurotrophic factor family ligands (GFLs) and the neuropoietic cytokines. Each family activates distinct but overlapping cellular pathways. Several studies have shown additive or synergistic interactions between neurotrophic factors from different families, though generally only a single combination has been studied. Because of possible interactions between the neurotrophic factors, the optimum concentration of a factor in a mixture may differ from the optimum when applied individually. Additionally, the effect of combinations of neurotrophic factors from each of the three families on neurite extension is unclear. This study examines the effects of several combinations of the neurotrophin nerve growth factor (NGF), the GFL glial cell-line derived neurotrophic factor (GDNF) and the neuropoietic cytokine ciliary neurotrophic factor (CNTF) on neurite outgrowth from young rat dorsal root ganglion (DRG) explants. The combination of 50 ng ml-1 NGF and 10 ng ml-1 of each GDNF and CNTF induced the highest level of neurite outgrowth at a 752 ± 53% increase over untreated DRGs and increased the longest neurite length to 2031 ± 97 µm compared to 916 ± 64 µm for untreated DRGs. The optimum concentrations of the three factors applied in combination corresponded to the optimum concentration of each factor when applied individually. These results indicate that the efficacy of future therapies for nerve repair would be enhanced by the controlled release of a combination of neurotrophins, GFLs and neuropoietic cytokines at higher concentrations than used in previous conduit designs.

  9. Integrin α5β1 expression on dopaminergic neurons is involved in dopaminergic neurite outgrowth on striatal neurons

    PubMed Central

    Izumi, Yasuhiko; Wakita, Seiko; Kanbara, Chisato; Nakai, Toshie; Akaike, Akinori; Kume, Toshiaki

    2017-01-01

    During development, dopaminergic neurons born in the substantia nigra extend their axons toward the striatum. However, the mechanisms by which the dopaminergic axons extend the striatum to innervate their targets remain unclear. We previously showed that paired-cultivation of mesencephalic cells containing dopaminergic neurons with striatal cells leads to the extension of dopaminergic neurites from the mesencephalic cell region to the striatal cell region. The present study shows that dopaminergic neurites extended along striatal neurons in the paired-cultures of mesencephalic cells with striatal cells. The extension of dopaminergic neurites was suppressed by the pharmacological inhibition of integrin α5β1. Using lentiviral vectors, short hairpin RNA (shRNA)-mediated knockdown of integrin α5 in dopaminergic neurons suppressed the neurite outgrowth to the striatal cell region. In contrast, the knockdown of integrin α5 in non-dopaminergic mesencephalic and striatal cells had no effect. Furthermore, overexpression of integrin α5 in dopaminergic neurons differentiated from embryonic stem cells enhanced their neurite outgrowth on striatal cells. These results indicate that integrin α5β1 expression on dopaminergic neurons plays an important role in the dopaminergic neurite outgrowth on striatal neurons. PMID:28176845

  10. Intact glycosaminoglycans from intervertebral disc-derived notochordal cell-conditioned media inhibit neurite growth while maintaining neuronal cell viability.

    PubMed

    Purmessur, Devina; Cornejo, Marisa C; Cho, Samuel K; Roughley, Peter J; Linhardt, Robert J; Hecht, Andrew C; Iatridis, James C

    2015-05-01

    Painful human intervertebral discs (IVDs) exhibit nerve growth deep into the IVD. Current treatments for discogenic back pain do not address the underlying mechanisms propagating pain and are often highly invasive or only offer temporary symptom relief. The notochord produces factors during development that pattern the spine and inhibit the growth of dorsal root ganglion (DRG) axons into the IVD. We hypothesize that notochordal cell (NC)-conditioned medium (NCCM) includes soluble factors capable of inhibiting neurite growth and may represent a future therapeutic target. To test if NCCM can inhibit neurite growth and determine if NC-derived glycosaminoglycans (GAGs) are necessary candidates for this inhibition. Human neuroblastoma (SH-SY5Y) cells and rat DRG cells were treated with NCCM in two-dimensional culture in vitro, and digestion and mechanistic studies determined if specific GAGs were responsible for inhibitory effects. Notochordal cell-conditioned medium was generated from porcine nucleus pulposus tissue that was cultured in Dulbecco's modified eagle's medium for 4 days. A dose study was performed using SH-SY5Y cells that were seeded in basal medium for 24 hours and neurite outgrowth and cell viability were assessed after treatment with basal media or NCCM (10% and 100%) for 48 hours. Glycosaminoglycans from NCCM were characterized using multiple digestions and liquid chromatography mass spectroscopy (LC-MS). Neurite growth was assessed on both SH-SY5Y and DRG cells after treatment with NCCM with and without GAG digestion. Notochordal cell-conditioned medium significantly inhibited the neurite outgrowth from SH-SY5Y cells compared with basal controls without dose or cytotoxic effects; % of neurite expressing cells were 39.0±2.9%, 27.3±3.6%, and 30.2±2.7% and mean neurite length was 60.3±3.5, 50.8±2.4, 53.2±3.7 μm for basal, 10% NCCM, and 100% NCCM, respectively. Digestions and LC-MS determined that chondroitin-6-sulfate was the major GAG chain in

  11. Surface Tension

    SciTech Connect

    2011-01-01

    Surface tension in the kitchen sink. At Berkeley Lab's Molecular Foundry, scientists study surface tension to understand how molecules "self-assemble." The coin trick in the video uses the re-arrangement of water molecules to seemingly create order out of disorder. The same principle can be used to create order in otherwise hard-to-handle nano materials. Scientists can then transfer these ordered materials onto surfaces by dipping them through the air-water interface, or (as we've recently shown) squeeze them so that they collapse into the water as two-molecule-thick nano sheets. http://newscenter.lbl.gov/feature-stories/2011/10/17/shaken-not-stirred/

  12. Surface Tension of Spacetime

    NASA Astrophysics Data System (ADS)

    Perko, Howard

    2017-01-01

    Concepts from physical chemistry and more specifically surface tension are introduced to spacetime. Lagrangian equations of motion for membranes of curved spacetime manifold are derived. The equations of motion in spatial directions are dispersion equations and can be rearranged to Schrodinger's equation where Plank's constant is related to membrane elastic modulus. The equation of motion in the time-direction has two immediately recognizable solutions: electromagnetic waves and corpuscles. The corpuscular membrane solution can assume different genus depending on quantized amounts of surface energy. A metric tensor that relates empty flat spacetime to energetic curved spacetime is found that satisfies general relativity. Application of the surface tension to quantum electrodynamics and implications for quantum chromodynamics are discussed. Although much work remains, it is suggested that spacetime surface tension may provide a classical explanation that combines general relativity with field theories in quantum mechanics and atomic particle physics.

  13. Tiam1 as a Signaling Mediator of Nerve Growth Factor-Dependent Neurite Outgrowth

    PubMed Central

    Vilar, Marçal; Paratcha, Gustavo; Ledda, Fernanda

    2010-01-01

    Nerve Growth Factor (NGF)-induced neuronal differentiation requires the activation of members of the Rho family of small GTPases. However, the molecular mechanisms through which NGF regulates cytoskeletal changes and neurite outgrowth are not totally understood. In this work, we identify the Rac1-specific guanine exchange factor (GEF) Tiam1 as a novel mediator of NGF/TrkA-dependent neurite elongation. In particular, we report that knockdown of Tiam1 causes a significant reduction in Rac1 activity and neurite outgrowth induced by NGF. Physical interaction between Tiam1 and active Ras (Ras-GTP), but not tyrosine phosphorylation of Tiam1, plays a central role in Rac1 activation by NGF. In addition, our findings indicate that Ras is required to associate Tiam1 with Rac1 and promote Rac1 activation upon NGF stimulation. Taken together, these findings define a novel molecular mechanism through which Tiam1 mediates TrkA signaling and neurite outgrowth induced by NGF. PMID:20333299

  14. Saccharin enhances neurite extension by regulating organization of the microtubules.

    PubMed

    Yamashita, Hiroo; Muroi, Yoshikage; Ishii, Toshiaki

    2013-11-06

    In the present study, we found that saccharin, an artificial calorie-free sweetener, promotes neurite extension in the cultured neuronal cells. The purposes of this study are to characterize the effect of saccharine on neurite extension and to determine how saccharin enhances neurite extension. The analyses were performed using mouse neuroblastoma N1E-115 cells and rat pheochromocytoma PC12 cells. Neurite extension was evaluated by counting the cells bearing neurites and measuring the length of neurites. Formation, severing and transportation of the microtubules were evaluated by immunostaining and western blotting analysis. Deprivation of glucose increased the number of N1E-115 cells bearing long processes. And the effect was inhibited by addition of glucose. Saccharin increased the number of these cells bearing long processes in a dose-dependent manner and total neurite length and longest neurite length in each cell. Saccharin also had a similar effect on NGF-treated PC12 cells. Saccharin increased the amount of the microtubules reconstructed after treatment with nocodazole, a disruptor of microtubules. The effect of saccharin on microtubule reconstruction was not influenced by dihydrocytochalasin B, an inhibitor of actin polymerization, indicating that saccharin enhances microtubule formation without requiring actin dynamics. In the cells treated with vinblastine, an inhibitor of microtubule polymerization, after microtubule reorganization, filamentous microtubules were observed more distantly from the centrosome in saccharin-treated cells, indicating that saccharin enhances microtubule severing and/or transportation. These results suggest that saccharin enhances neurite extension by promoting microtubule organization. © 2013.

  15. Potentiation of NGF-induced neurite outgrowth in PC12 cells by papaverine: role played by PLC-γ, IP3 receptors.

    PubMed

    Itoh, Kanako; Ishima, Tamaki; Kehler, Jan; Hashimoto, Kenji

    2011-03-04

    Papaverine, an inhibitor of phosphodiesterase (PDE) 10A, is gaining attention for its potential in the treatment of neuropsychiatric diseases such as schizophrenia. However, the precise mechanisms underlying the putative neuroprotective/neurotrophic actions of papaverine remain unclear. Thus, we investigated the effects of papaverine on nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells. Papaverine potentiated NGF-induced neurite outgrowth in PC12 cells in a concentration-dependent manner. In contrast, the selective PDE10A inhibitor MP-10 had no effect on NGF-induced neurite outgrowth. The potentiation of NGF-induced neurite outgrowth by papaverine was blocked by the PLC-γ inhibitor U73122. Furthermore, papaverine's potentiation of NGF-induced neurite outgrowth was also blocked by the co-administration of inositol 1,4,5-trisphosphate (IP(3)) receptor antagonists (xestospongin C and 2-aminoethoxydiphenyl borate (2-APB)) and by reduced expression of IP(3) receptor gene (i.e., itpr1 and itpr3) by siRNA. Our findings suggest that papaverine could potentiate NGF-induced neurite outgrowth, and that activation of PLC-γ and IP(3) receptors might be involved in the mechanism underlying papaverine's potentiation of neurite outgrowth in PC12 cells.

  16. Tension Structure

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The fabric structure pictured is the Campus Center of La Verne College, La Verne, California. Unlike the facilities shown on the preceding pages, it is not air-supported. It is a "tension structure," its multi-coned fabric membrane supported by a network of cables attached to steel columns which function like circus tent poles. The spider-web in the accompanying photo is a computer graph of the tension pattern. The designers, Geiger-Berger Associates PC, of New York City, conducted lengthy computer analysis to determine the the best placement of columns and cables. The firm also served as structural engineering consultant on the Pontiac Silverdome and a number of other large fabric structures. Built by Birdair Structures, Inc., Buffalo, New York, the La Verne Campus Center was the first permanent facility in the United States enclosed by the space-spinoff fabric made of Owens-Corning Beta fiber glass coated with Du Pont Teflon TFE. The flexible design permits rearrangement of the interior to accommodate athletic events, student activities, theatrical productions and other recreational programs. Use of fabric covering reduced building cost 30 percent below conventional construction.

  17. White matter microstructure pathology in classic galactosemia revealed by neurite orientation dispersion and density imaging.

    PubMed

    Timmers, Inge; Zhang, Hui; Bastiani, Matteo; Jansma, Bernadette M; Roebroeck, Alard; Rubio-Gozalbo, M Estela

    2015-03-01

    White matter abnormalities have been observed in patients with classic galactosemia, an inborn error of galactose metabolism. However, magnetic resonance imaging (MRI) data collected in the past were generally qualitative in nature. Our objective was to investigate white matter microstructure pathology and examine correlations with outcome and behaviour in this disease, by using multi-shell diffusion weighted imaging. In addition to standard diffusion tensor imaging (DTI), neurite orientation dispersion and density imaging (NODDI) was used to estimate density and orientation dispersion of neurites in a group of eight patients (aged 16-21 years) and eight healthy controls (aged 15-20 years). Extensive white matter abnormalities were found: neurite density index (NDI) was lower in the patient group in bilateral anterior areas, and orientation dispersion index (ODI) was increased mainly in the left hemisphere. These specific regional profiles are in agreement with the cognitive profile observed in galactosemia, showing higher order cognitive impairments, and language and motor impairments, respectively. Less favourable white matter properties correlated positively with age and age at onset of diet, and negatively with behavioural outcome (e.g. visual working memory). To conclude, this study provides evidence of white matter pathology regarding density and dispersion of neurites in these patients. The results are discussed in light of suggested pathophysiological mechanisms.

  18. Arthroscopic suprapectoral and open subpectoral biceps tenodesis: a comparison of restoration of length-tension and mechanical strength between techniques.

    PubMed

    Werner, Brian C; Lyons, Matthew L; Evans, Cody L; Griffin, Justin W; Hart, Joseph M; Miller, Mark D; Brockmeier, Stephen F

    2015-04-01

    This study aimed to (1) evaluate the ex vivo restoration of the long head biceps length-tension for both arthroscopic suprapectoral biceps tenodesis (ASPBT) and open subpectoral biceps tenodesis (OSPBT) techniques and (2) assess how location in the proximal humerus affects pullout strength for tenodesis using an interference screw implant. Eighteen matched cadaveric shoulders were randomized to OSPBT or ASPBT groups (9 each). Tenodesis was performed using clinical techniques. Preoperatively, a metallic bead was placed in the biceps tendon and a fluoroscopic image was obtained. Postoperatively, an image was obtained to evaluate the location of the tenodesis and the metallic bead and determine tensioning. Biomechanical load-to-failure testing was then performed. The ASPBT technique resulted in an average of 2.15 ± 0.62 cm of biceps overtensioning compared with 0.78 ± 0.35 cm (P < .001) in the OSPBT group. The average load to failure in the ASPBT group was 138.8 ± 29.1 N compared with 197 ± 38.6 N (P = .002) in the OSPBT group. Failure caused by implant pullout was significantly more frequent in the ASPBT group (7 of 9) than in the OSPBT group (1 of 9). The described ASPBT technique using an interference screw implant has the tendency to overtension the biceps and has a significantly decreased ultimate load to failure compared with an open subpectoral technique in matched cadaveric specimens. This study shows differences in the biomechanical properties of OSPBT and ASPBT. Modification of currently published ASPBT techniques may be necessary to improve restoration of the physiological length-tension relationship of the biceps. Clinical studies may need to clarify if the lower ultimate load to failure for the ASPBT technique is clinically significant. Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

  19. Increased synapsin expression and neurite sprouting in lamprey brain after spinal cord injury.

    PubMed

    Lau, Billy Y B; Foldes, Andrea E; Alieva, Naila O; Oliphint, Paul A; Busch, David J; Morgan, Jennifer R

    2011-04-01

    Spinal cord injury induces structural plasticity throughout the mammalian nervous system, including distant locations in the brain. Several types of injury-induced plasticity have been identified, such as neurite sprouting, axon regeneration, and synaptic remodeling. However, the molecular mechanisms involved in injury-induced plasticity are unclear as is the extent to which injury-induced plasticity in brain is conserved across vertebrate lineages. Due to its robust roles in neurite outgrowth and synapse formation during developmental processes, we examined synapsin for its potential involvement in injury-induced plasticity. We used lamprey, a vertebrate that undergoes robust anatomical plasticity and functional recovery after spinal cord injury. At 3 and 11 weeks after spinal cord transection, synapsin I mRNA was upregulated >2-fold in lamprey brain, as assayed by semi-quantitative RT-PCR. Other synaptic vesicle-associated genes remained unchanged. In situ hybridization revealed that synapsin I mRNA was increased globally throughout the lamprey brain. Immunolabeling for synapsin I protein revealed a significant increase in both the intensity and density of synapsin I-positive structures in lamprey hindbrain at 11 weeks post-transection, relative to controls. Moreover, the number of structures immunolabeled for phospho-synapsin (serine 9) increased after injury, suggestive of neurite sprouting. Indeed, at the ultrastructural level, there was an increase in neurite density at 11 weeks post-transection. Taken together, these data show that neurite sprouting in the brain is an evolutionarily conserved response to a distant spinal cord injury and suggest that synapsin and its phosphorylation at serine 9 play key roles in the sprouting mechanism. Copyright © 2011 Elsevier Inc. All rights reserved.

  20. Insulin signaling regulates neurite growth during metamorphic neuronal remodeling

    PubMed Central

    Gu, Tingting; Zhao, Tao; Hewes, Randall S.

    2014-01-01

    Summary Although the growth capacity of mature neurons is often limited, some neurons can shift through largely unknown mechanisms from stable maintenance growth to dynamic, organizational growth (e.g. to repair injury, or during development transitions). During insect metamorphosis, many terminally differentiated larval neurons undergo extensive remodeling, involving elimination of larval neurites and outgrowth and elaboration of adult-specific projections. Here, we show in the fruit fly, Drosophila melanogaster (Meigen), that a metamorphosis-specific increase in insulin signaling promotes neuronal growth and axon branching after prolonged stability during the larval stages. FOXO, a negative effector in the insulin signaling pathway, blocked metamorphic growth of peptidergic neurons that secrete the neuropeptides CCAP and bursicon. RNA interference and CCAP/bursicon cell-targeted expression of dominant-negative constructs for other components of the insulin signaling pathway (InR, Pi3K92E, Akt1, S6K) also partially suppressed the growth of the CCAP/bursicon neuron somata and neurite arbor. In contrast, expression of wild-type or constitutively active forms of InR, Pi3K92E, Akt1, Rheb, and TOR, as well as RNA interference for negative regulators of insulin signaling (PTEN, FOXO), stimulated overgrowth. Interestingly, InR displayed little effect on larval CCAP/bursicon neuron growth, in contrast to its strong effects during metamorphosis. Manipulations of insulin signaling in many other peptidergic neurons revealed generalized growth stimulation during metamorphosis, but not during larval development. These findings reveal a fundamental shift in growth control mechanisms when mature, differentiated neurons enter a new phase of organizational growth. Moreover, they highlight strong evolutionarily conservation of insulin signaling in neuronal growth regulation. PMID:24357229

  1. A clinico-pathological study of primary neuritic leprosy.

    PubMed

    Pannikar, V K; Arunthathi, S; Chacko, C J; Fritschi, E P

    1983-04-01

    Normally neural involvement in leprosy is an ascending neuritis from the nerve involvement in the dermal lesions. However, in some cases neural involvement is seen in the absence of any dermal lesions. In some of these pure neuritic cases, dermal lesions appear sometime later. It is, therefore, more appropriate to designate such cases as 'primary neuritic' cases. This study is aimed at diagnosing primary neuritic leprosy among patients presenting with only neuritic symptoms. An attempt is also made to classify primary neuritic leprosy on a clinical and histopathological basis. During the period 1979-80, 30 patients reported to the out patient department of Schieffelin Leprosy Research and Training Centre, Karigiri with complaints of neuritic origin. In addition to clinical examination and routine skin smears, investigations such as skin, nerve and nasal biopsies, nerve conduction velocity and lepromin testing were carried out where feasible. 17 of these patients were diagnosed as primary neuritic leprosy and in 7 patients other neurological conditions were diagnosed. The remaining 6 patients were kept under observation and have not shown evidence of leprosy during a two year period of following-up. It is interesting that 4 of the 17 primary neuritic cases developed patches during follow-up period of two years. In the final analysis 7 patients (41.2%) were classified into the lepromatous group and 10 patients (58.8%) in the non-lepromatous group (Table-6). This classification will have a bearing on duration of treatment and for their subsequent release from control.

  2. μ2-Dependent endocytosis of N-cadherin is regulated by β-catenin to facilitate neurite outgrowth.

    PubMed

    Chen, Yi-Ting; Tai, Chin-Yin

    2017-02-22

    Circuit formation in the brain requires neurite outgrowth throughout development to establish synaptic contacts with target cells. Active endocytosis of several adhesion molecules facilitates the dynamic exchange of these molecules at the surface and promotes neurite outgrowth in developing neurons. The endocytosis of N-cadherin, a calcium-dependent adhesion molecule, has been implicated in the regulation of neurite outgrowth, but the mechanism remains unclear. Here, we identified that a fraction of N-cadherin internalizes through clathrin-mediated endocytosis (CME). Two tyrosine-based motifs in the cytoplasmic domain of N-cadherin recognized by the μ2 subunit of the AP-2 adaptor complex are responsible for CME of N-cadherin. Moreover, β-catenin, a core component of the N-cadherin adhesion complex, inhibits N-cadherin endocytosis by masking the 2 tyrosine-based motifs. Removal of β-catenin facilitates μ2 binding to N-cadherin, thereby increasing clathrin-mediated N-cadherin endocytosis and neurite outgrowth without affecting the steady-state level of surface N-cadherin. These results identify and characterize the mechanism controlling N-cadherin endocytosis through β-catenin-regulated μ2 binding to modulate neurite outgrowth.

  3. Real-time detection of neurite outgrowth using microfluidic device

    NASA Astrophysics Data System (ADS)

    Kim, Samhwan; Jang, Jongmoon; Choi, Hongsoo; Moon, Cheil

    2013-05-01

    We developed a simple method for real-time detection of the neurite outgrowth using microfluidic device. Our microfluidic device contains three compartmentalized channels which are for cell seeding, hydrogel and growth factors. Collagen gel is filled in the middle channel and pheochromocytoma (PC12) cells are seeded in the left channel. To induce differentiation of PC12 cells, 50 ng/ml to1000 ng/ml of nerve growth factor (NGF) is introduced into the right channel. After three days of NGF treatment, PC12 cells begin to extend neurites and formed neurite network from sixth day. Quantification of neurite outgrowth is analyzed by measuring the total area of neurites. On sixth day, the area is doubled compared to the area on third day and increases by 20 times on ninth day.

  4. Sensing the Tension

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Spanning over 4 decades, NASA's bolt tension monitoring technology has benefited automakers, airplane builders, and other major manufacturers that rely on the devices to evaluate the performance of computerized torque wrenches and other assembly line mechanisms. In recent years, the advancement of ultrasonic sensors has drastically eased this process for users, ensuring that proper tension and torque are being applied to bolts and fasteners, with less time needed for data analysis. Langley Research Center s Nondestructive Evaluation Branch is one of the latest NASA programs to incorporate ultrasonic sensors within a bolt tension measurement instrument. As a multi-disciplined research group focused on spacecraft and aerospace transportation safety, one of the branch s many commitments includes transferring problem solutions to industry. In 1998, the branch carried out this obligation in a licensing agreement with Micro Control, Inc., of West Bloomfield, Michigan. Micro Control, an automotive inspection company, obtained the licenses to two Langley patents to provide an improved-but-inexpensive means of ultrasonic tension measurement.

  5. Reelin Prevents Apical Neurite Retraction during Terminal Translocation and Dendrite Initiation

    PubMed Central

    O'Dell, Ryan S.; Cameron, David A.; Zipfel, Warren R.

    2015-01-01

    The mechanisms controlling cortical dendrite initiation and targeting are poorly understood. Multiphoton imaging of developing mouse cortex reveals that apical dendrites emerge by direct transformation of the neuron's leading process during the terminal phase of neuronal migration. During this ∼110 min period, the dendritic arbor increases ∼2.5-fold in size and migration arrest occurs below the first stable branch point in the developing arbor. This dendritic outgrowth is triggered at the time of leading process contact with the marginal zone (MZ) and occurs primarily by neurite extension into the extracellular matrix of the MZ. In reeler cortices that lack the secreted glycoprotein Reelin, a subset of neurons completed migration but then retracted and reorganized their arbor in a tangential direction away from the MZ soon after migration arrest. For these reeler neurons, the tangential oriented primary neurites were longer lived than the radially oriented primary neurites, whereas the opposite was true of wild-type (WT) neurons. Application of Reelin protein to reeler cortices destabilized tangential neurites while stabilizing radial neurites and stimulating dendritic growth in the MZ. Therefore, Reelin functions as part of a polarity signaling system that links dendritogenesis in the MZ with cellular positioning and cortical lamination. SIGNIFICANCE STATEMENT Whether the apical dendrite emerges by transformation of the leading process of the migrating neuron or emerges de novo after migration is completed is unclear. Similarly, it is not clear whether the secreted glycoprotein Reelin controls migration and dendritic growth as related or separate processes. Here, multiphoton microscopy reveals the direct transformation of the leading process into the apical dendrite. This transformation is coupled to the successful completion of migration and neuronal soma arrest occurs below the first stable branch point of the nascent dendrite. Deficiency in Reelin causes

  6. Laminin promotes neuritic regeneration from cultured peripheral and central neurons

    PubMed Central

    1983-01-01

    The ability of axons to grow through tissue in vivo during development or regeneration may be regulated by the availability of specific neurite-promoting macromolecules located within the extracellular matrix. We have used tissue culture methods to examine the relative ability of various extracellular matrix components to elicit neurite outgrowth from dissociated chick embryo parasympathetic (ciliary ganglion) neurons in serum-free monolayer culture. Purified laminin from both mouse and rat sources, as well as a partially purified polyornithine-binding neurite promoting factor (PNPF-1) from rat Schwannoma cells all stimulate neurite production from these neurons. Laminin and PNPF-1 are also potent stimulators of neurite growth from cultured neurons obtained from other peripheral as well as central neural tissues, specifically avian sympathetic and sensory ganglia and spinal cord, optic tectum, neural retina, and telencephalon, as well as from sensory ganglia of the neonatal mouse and hippocampal, septal, and striatal tissues of the fetal rat. A quantitative in vitro bioassay method using ciliary neurons was used to (a) measure and compare the specific neurite-promoting activities of these agents, (b) confirm that during the purification of laminin, the neurite-promoting activity co- purifies with the laminin protein, and (c) compare the influences of antilaminin antibodies on the neurite-promoting activity of laminin and PNPF-1. We conclude that laminin and PNPF-1 are distinct macromolecules capable of expressing their neurite-promoting activities even when presented in nanogram amounts. This neurite-promoting bioassay currently represents the most sensitive test for the biological activity of laminin. PMID:6643580

  7. Effect of viscosity on neurite outgrowth and fractal dimension.

    PubMed

    Caserta, F; Hausman, R E; Eldred, W D; Kimmel, C; Stanley, H E

    1992-03-02

    The growth mechanism by which neurons achieve their characteristic ramified morphology has long been of interest, but determining whether physical parameters, such as viscosity, are important has been difficult due to a lack of useful hypotheses and standard reproducible techniques. We have recently shown that neurons exhibit fractal behavior and that their fractal dimension (df) is consistent with a physical process called diffusion-limited aggregation (DLA). We suggested that this DLA behavior might stem from viscosity differences, chemical gradients or electrical fields (Caserta et al., Phys. Rev. Lett., 64 (1990) 95-98). DLA is a model for a large family of growth processes. In order for a process to fit the DLA model, the growth rate must be proportional to the gradient of a field at a point on the growing structure (Feder, Plenum, New York, 1988, Ch. 4). Chemical, electrical, or fluid pressure fields can fit the model depending on the particular physical system under study. Here, we studied growth of retinal neurons from chick embryos in culture media of various fluid viscosities. Thus, we test whether DLA in this system was based on a fluid pressure field. As viscosity was increased from 1 to 4.3 cps, the number of neurite branches decreased 98%. However, there was no effect on df. Over this range of viscosities, total cellular protein synthesis decreased only 17%. The results indicate that, while differences in viscosity between the interior and exterior of the cell affect neurite outgrowth, they do not affect the fractal behavior of neurons. Thus, viscosity differences are not the basis for the DLA pattern of neuronal arborization.

  8. Serum-induced neurite retraction in CAD cells--involvement of an ATP-actin retractile system and the lack of microtubule-associated proteins.

    PubMed

    Chesta, María E; Carbajal, Agustín; Arce, Carlos A; Bisig, Carlos G

    2014-11-01

    Cultured catecholamine-differentiated cells [which lack the microtubule-associated proteins (MAPs): MAP1B, MAP2, Tau, STOP, and Doublecortin] proliferate in the presence of fetal bovine serum, and, in its absence, cease dividing and generate processes similar to the neurites of normal neurons. The reintroduction of serum induces neurite retraction, and proliferation resumes. The neurite retraction process in catecholamine-differentiated cells was partially characterized in this study. Microtubules in the cells were found to be in a highly dynamic state, and tubulin in the microtubules consisted primarily of the tyrosinated and deacetylated isotypes. Increased levels of acetylated or Δ2-tubulin (which are normally absent) did not prevent serum-induced neurite retraction. Treatment of differentiated cells with lysophosphatidic acid or adenosine deaminase induced neurite retraction. Inhibition of Rho-associated protein kinase, ATP depletion and microfilament disruption each (individually) blocked serum-induced neurite retraction, suggesting that an ATP-dependent actomyosin system underlies the mechanism of neurite retraction. Nocodazole treatment induced neurite retraction, but this effect was blocked by pretreatment with the microtubule-stabilizing drug paclitaxel (Taxol). Paclitaxel did not prevent serum-induced or lysophosphatidic acid-induced retraction, suggesting that integrity of microtubules (despite their dynamic state) is necessary to maintain neurite elongation, and that paclitaxel-induced stabilization alone is not sufficient to resist the retraction force induced by serum. Transfection with green fluorescent protein-Tau conferred resistance to retraction caused by serum. We hypothesize that, in normal neurons (cultured or in vivo), MAPs are necessary not only to stabilize microtubules, but also to establish interactions with other cytoskeletal or membrane components to form a stable structure capable of resisting the retraction force.

  9. C. elegans fmi-1/flamingo and Wnt pathway components interact genetically to control the anteroposterior neurite growth of the VD GABAergic neurons

    PubMed Central

    Najarro, Elvis Huarcaya; Ackley, Brian D.

    2013-01-01

    Directed axonal growth is essential to establish neuronal networks. During the early development of the VD neurons, an anterior neurite that will become the VD axon extends along the anteroposterior (A/P) axis in the ventral nerve cord (VNC) in Caenorhabditis elegans. Little is known about the cellular and molecular mechanisms that are important for correct neurite growth in the VNC. In fmi-1/flamingo mutant animals, we observed that some postembryonically born VD neurons had a posterior neurite instead of a normal anterior neurite, which caused aberrant VD commissure patterning along the A/P axis. In addition, VD anterior neurites had underextension defects in the VNC in fmi-1 animals, whereas VD commissure growth along the dorsoventral (D/V) axis occurred normally in these animals, suggesting that fmi-1 is important for neurite growth along the A/P axis but not the D/V axis. We also uncovered unknown details of the early development of the VD neurons, indicating that the neurite defects arose during their early development. Interestingly, though fmi-1 is present at this time in the VNC, we did not observe FMI-1 in the VD neurons themselves, suggesting that fmi-1 might be working in a cell non-autonomous fashion. Furthermore, fmi-1 appears to be working in a novel pathway, independently from the planar cell polarity pathway and in parallel to lin-17/frizzled and dsh-1/dishevelled, to determine the direction of neurite growth. Our findings indicate that redundant developmental pathways regulate neurite growth in the VNC in C. elegans. PMID:23376536

  10. C. elegans fmi-1/flamingo and Wnt pathway components interact genetically to control the anteroposterior neurite growth of the VD GABAergic neurons.

    PubMed

    Huarcaya Najarro, Elvis; Ackley, Brian D

    2013-05-01

    Directed axonal growth is essential to establish neuronal networks. During the early development of the VD neurons, an anterior neurite that will become the VD axon extends along the anteroposterior (A/P) axis in the ventral nerve cord (VNC) in Caenorhabditis elegans. Little is known about the cellular and molecular mechanisms that are important for correct neurite growth in the VNC. In fmi-1/flamingo mutant animals, we observed that some postembryonically born VD neurons had a posterior neurite instead of a normal anterior neurite, which caused aberrant VD commissure patterning along the A/P axis. In addition, VD anterior neurites had underextension defects in the VNC in fmi-1 animals, whereas VD commissure growth along the dorsoventral (D/V) axis occurred normally in these animals, suggesting that fmi-1 is important for neurite growth along the A/P axis but not the D/V axis. We also uncovered unknown details of the early development of the VD neurons, indicating that the neurite defects arose during their early development. Interestingly, though fmi-1 is present at this time in the VNC, we did not observe FMI-1 in the VD neurons themselves, suggesting that fmi-1 might be working in a cell non-autonomous fashion. Furthermore, fmi-1 appears to be working in a novel pathway, independently from the planar cell polarity pathway and in parallel to lin-17/frizzled and dsh-1/dishevelled, to determine the direction of neurite growth. Our findings indicate that redundant developmental pathways regulate neurite growth in the VNC in C. elegans.

  11. Actin cortex architecture regulates cell surface tension.

    PubMed

    Chugh, Priyamvada; Clark, Andrew G; Smith, Matthew B; Cassani, Davide A D; Dierkes, Kai; Ragab, Anan; Roux, Philippe P; Charras, Guillaume; Salbreux, Guillaume; Paluch, Ewa K

    2017-06-01

    Animal cell shape is largely determined by the cortex, a thin actin network underlying the plasma membrane in which myosin-driven stresses generate contractile tension. Tension gradients result in local contractions and drive cell deformations. Previous cortical tension regulation studies have focused on myosin motors. Here, we show that cortical actin network architecture is equally important. First, we observe that actin cortex thickness and tension are inversely correlated during cell-cycle progression. We then show that the actin filament length regulators CFL1, CAPZB and DIAPH1 regulate mitotic cortex thickness and find that both increasing and decreasing thickness decreases tension in mitosis. This suggests that the mitotic cortex is poised close to a tension maximum. Finally, using a computational model, we identify a physical mechanism by which maximum tension is achieved at intermediate actin filament lengths. Our results indicate that actin network architecture, alongside myosin activity, is key to cell surface tension regulation.

  12. GSK-3β activation mediates Nogo-66-induced inhibition of neurite outgrowth in N2a cells.

    PubMed

    Shen, Jian-ying; Yi, Xu-xia; Xiong, Nan-xiang; Wang, Hai-jun; Duan, Xiao-wei; Zhao, Hong-yang

    2011-11-14

    The axons of the adult mammalian brain and spinal cord fail to regenerate after injury, and it has been suggested that Nogo-66 could prevent CNS axon repair. However, the mechanism of Nogo-66 inhibiting neurite outgrowth remains unknown. Our previous results indicated that protein kinase B (PKB) is involved in the inhibition of the neurite outgrowth by Nogo-66. Glycogen synthase kinase-3β (GSK-3β) is implicated in many processes in the nervous system, including differentiation, specification, polarity, plasticity and axon growth. In addition, GSK-3β is one of the most important molecules downstream of PKB. In the present study, we report on the role of GSK-3β signaling on Nogo-66-treated mouse neuroblastoma N2a cells. Nogo-66 reduced the phosphorylation of GSK-3β at Ser9 in N2a cells. In contrast, pretreatment with SB216763, a specific inhibitor of GSK-3β, resulted in an amelioration of neurite outgrowth by Nogo-66, compared with the Nogo-66 alone group (P<0.05). Moreover, we performed RNA interference experiments to knock down GSK-3β expression levels in N2a cells via transient transfection of shRNA plasmids. The inhibition of neurite outgrowth by Nogo-66 was subdued in shRNA cells, compared to the non-RNAi cells (P<0.05). Taken together, these data suggest that GSK-3β is involved in the inhibition by Nogo-66 of neurite outgrowth in N2a cells.

  13. Enhancement of neurite outgrowth in neuronal-like cells following boron nitride nanotube-mediated stimulation.

    PubMed

    Ciofani, Gianni; Danti, Serena; D'Alessandro, Delfo; Ricotti, Leonardo; Moscato, Stefania; Bertoni, Giovanni; Falqui, Andrea; Berrettini, Stefano; Petrini, Mario; Mattoli, Virgilio; Menciassi, Arianna

    2010-10-26

    In this paper, we propose an absolutely innovative technique for the electrical stimulation of cells, based on piezoelectric nanoparticles. Ultrasounds are used to impart mechanical stress to boron nitride nanotubes incubated with neuronal-like PC12 cells. By virtue of their piezoelectric properties, these nanotubes can polarize and convey electrical stimuli to the cells. PC12 stimulated with the present method exhibit neurite sprout 30% greater than the control cultures after 9 days of treatment.

  14. Experimental microembolism induces localized neuritic pathology in guinea pig cerebrum.

    PubMed

    Li, Jian-Ming; Cai, Yan; Liu, Fei; Yang, La; Hu, Xia; Patrylo, Peter R; Cai, Huaibin; Luo, Xue-Gang; Xiao, Dong; Yan, Xiao-Xin

    2015-05-10

    Microbleeds are a common finding in aged human brains. In Alzheimer's disease (AD), neuritic plaques composed of β-amyloid (Aβ) deposits and dystrophic neurites occur frequently around cerebral vasculature, raising a compelling question as to whether, and if so, how, microvascular abnormality and amyloid/neuritic pathology might be causally related. Here we used a guinea pig model of cerebral microembolism to explore a potential inductive effect of vascular injury on neuritic and amyloid pathogenesis. Brains were examined 7-30 days after experimental microvascular embolization occupying ~0.5% of total cortical area. Compared to sham-operated controls, glial fibrillary acidic protein immunoreactivity was increased in the embolized cerebrum, evidently around intracortical vasculature. Swollen/sprouting neurites exhibiting increased reactivity of nicotinamide adenine dinucleotide phosphate diaphorase, parvalbumin, vesicular glutamate transporter 1 and choline acetyltransferase appeared locally in the embolized brains in proximity to intracortical vasculature. The embolization-induced swollen/sprouting neurites were also robustly immunoreactive for β-amyloid precursor protein and β-secretase-1, the substrate and initiating enzyme for Aβ genesis. These experimental data suggest that microvascular injury can induce multisystem neuritic pathology associated with an enhanced amyloidogenic potential in wild-type mammalian brain.

  15. Experimental microembolism induces localized neuritic pathology in guinea pig cerebrum

    PubMed Central

    Li, Jian-Ming; Cai, Yan; Liu, Fei; Yang, La; Hu, Xia; Patrylo, Peter R.; Cai, Huaibin; Luo, Xue-Gang; Xiao, Dong; Yan, Xiao-Xin

    2015-01-01

    Microbleeds are a common finding in aged human brains. In Alzheimer's disease (AD), neuritic plaques composed of β-amyloid (Aβ) deposits and dystrophic neurites occur frequently around cerebral vasculature, raising a compelling question as to whether, and if so, how, microvascular abnormality and amyloid/neuritic pathology might be causally related. Here we used a guinea pig model of cerebral microembolism to explore a potential inductive effect of vascular injury on neuritic and amyloid pathogenesis. Brains were examined 7-30 days after experimental microvascular embolization occupying ~0.5% of total cortical area. Compared to sham-operated controls, glial fibrillary acidic protein immunoreactivity was increased in the embolized cerebrum, evidently around intracortical vasculature. Swollen/sprouting neurites exhibiting increased reactivity of nicotinamide adenine dinucleotide phosphate diaphorase, parvalbumin, vesicular glutamate transporter 1 and choline acetyltransferase appeared locally in the embolized brains in proximity to intracortical vasculature. The embolization-induced swollen/sprouting neurites were also robustly immunoreactive for β-amyloid precursor protein and β-secretase-1, the substrate and initiating enzyme for Aβ genesis. These experimental data suggest that microvascular injury can induce multisystem neuritic pathology associated with an enhanced amyloidogenic potential in wild-type mammalian brain. PMID:25871402

  16. Mechanical characterization of thin film, water-based polymer gels through simple tension testing of laminated bilayers.

    PubMed

    Krone, Ryan; Havenstrite, Karen; Shafi, Bilal

    2013-11-01

    We present a method of characterizing the nonlinear stress-strain behavior of thin films of extremely soft, water-based polymer gels using uniaxial tension testing of bilayer laminates, in conjunction with methods of membrane nonlinear elasticity. A custom tensile testing apparatus is used to conduct quasi-static, uniaxial extension tests of narrow strips of thin, laminated sheets of bonded hydrogel and silicone rubber, submerged in a saline bath. The tensile load is measured via sensitive load cell and the position of material markers, at a central test-section of the sample, is optically tracked via digital image tracking methods. Stress-strain relationships are calculated for the hydrogel component of the bilayer, considered hyperelastic, homogeneous, isotropic, and incompressible, using membrane theories of finite hyperelasticity. We present the stress response for strains up to about 35% for poly(ethylene glycol) (PEG)-based hydrogels (>90% water) with polymer concentrations by weight of 5% to 10%. Polynomial functions are fit to the data for each formulation, whereby the one-dimensional strain-energy function for each formulation is determined by taking the indefinite integral.

  17. Enterobacter cloacae as biosurfactant producing bacterium: differentiating its effects on interfacial tension and wettability alteration Mechanisms for oil recovery during MEOR process.

    PubMed

    Sarafzadeh, Pegah; Hezave, Ali Zeinolabedini; Ravanbakhsh, Moosa; Niazi, Ali; Ayatollahi, Shahab

    2013-05-01

    Microbial enhanced oil recovery (MEOR) process utilizes microorganisms or their metabolites to mobilize the trapped oil in the oil formation after primary and secondary oil recovery stages. MEOR technique is considered as more environmentally friendly and low cost process. There are several identified mechanisms for more oil recovery using MEOR processes however; wettability alteration and interfacial tension (IFT) reduction are the important ones. Enterobacter Cloacae, a facultative bio-surfactant producer bacterium, was selected as a bacterial formulation due to its known performance on IFT reduction and wettability alteration. To quantify the effects of these two mechanisms, different tests including oil spreading, in situ and ex situ core flooding, wettability measurement (Amott), IFT, viscosity and pH measurements were performed. The obtained results revealed that the experimental procedure used in this study was able to quantitatively identify the individual effects of both mechanisms on the ultimate microbial oil recovery. The results demonstrated considerable effects of both mechanisms on the tertiary oil recovery; however after a proper shut in time period, more tertiary oil was recovered because of wettability alteration mechanism. Finally, SEM images taken from the treated cores showed biofilm formation on the rock pore surfaces, which is responsible for rock surface wettability alteration. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Small membranes under negative surface tension

    NASA Astrophysics Data System (ADS)

    Avital, Yotam Y.; Farago, Oded

    2015-03-01

    We use computer simulations and a simple free energy model to study the response of a bilayer membrane to the application of a negative (compressive) mechanical tension. Such a tension destabilizes the long wavelength undulation modes of giant vesicles, but it can be sustained when small membranes and vesicles are considered. Our negative tension simulation results reveal two regimes—(i) a weak negative tension regime characterized by stretching-dominated elasticity and (ii) a strong negative tension regime featuring bending-dominated elastic behavior. This resembles the findings of the classic Evans and Rawicz micropipette aspiration experiment in giant unilamellar vesicles (GUVs) [E. Evans and W. Rawicz, Phys, Rev. Lett. 64, 2094 (1990)]. However, in GUVs the crossover between the two elasticity regimes occurs at a small positive surface tension, while in smaller membranes it takes place at a moderate negative tension. Another interesting observation concerning the response of a small membrane to negative surface tension is related to the relationship between the mechanical and fluctuation tensions, which are equal to each other for non-negative values. When the tension decreases to negative values, the fluctuation tension γ drops somewhat faster than the mechanical tension τ in the small negative tension regime, before it saturates (and becomes larger than τ) for large negative tensions. The bending modulus exhibits an "opposite" trend. It remains almost unchanged in the stretching-dominated elastic regime, and decreases in the bending-dominated regime. Both the amplitudes of the thermal height undulations and the projected area variations diverge at the onset of mechanical instability.

  19. Rates of hypoxia induction alter mechanisms of O2 uptake and the critical O2 tension of goldfish.

    PubMed

    Regan, Matthew D; Richards, Jeffrey G

    2017-07-15

    The rate of hypoxia induction (RHI) is an important but overlooked dimension of environmental hypoxia that may affect an organism's survival. We hypothesized that, compared with rapid RHI, gradual RHI will afford an organism more time to alter plastic phenotypes associated with O2 uptake and subsequently reduce the critical O2 tension (Pcrit) of the rate of O2 uptake (ṀO2 ). We investigated this by determining Pcrit values for goldfish exposed to short (∼24 min), typical (∼84 min) and long (∼480 min) duration Pcrit trials to represent different RHIs. Consistent with our predictions, long duration Pcrit trials yielded significantly lower Pcrit values (1.0-1.4 kPa) than short and typical duration trials, which did not differ (2.6±0.3 and 2.5±0.2 kPa, respectively). Parallel experiments revealed these time-related shifts in Pcrit were associated with changes to aspects of the O2 transport cascade that took place over the hypoxia exposures: gill surface areas and haemoglobin-O2 binding affinities were significantly higher in fish exposed to gradual RHIs over 480 min than fish exposed to rapid RHIs over 60 min. Our results also revealed that the choice of respirometric technique (i.e. closed versus intermittent) does not affect Pcrit or routine ṀO2 , despite the significantly reduced water pH and elevated CO2 and ammonia levels measured following closed-circuit Pcrit trials of ∼90 min. Together, our results demonstrate that gradual RHIs result in alterations to physiological parameters that enhance O2 uptake in hypoxic environments. An organism's innate Pcrit is therefore most accurately determined using rapid RHIs (<90 min) so as to avoid the confounding effects of hypoxic acclimation. © 2017. Published by The Company of Biologists Ltd.

  20. Fracture mechanics evaluation of progressive fatigue damage in a circular-hole-notched GRP composite under combined tension/torsion loading

    NASA Astrophysics Data System (ADS)

    Takemura, Kenichi; Fujii, Toru

    Progressive failure from a circular hole in glass-fiber-reinforced plastics (GRP) under combined tension/torsion cyclic loading has been investigated. Thin-walled tubular specimens were used. The composition of the specimens was the same as in previous work. As pseudo-crack growth was observed under fatigue loading leading to the final failure, fracture mechanics methods were applied to characterize the fatigue failure process. The energy release rate was used as a parameter for progressive failure. Fatigue life under combined cyclic loading was estimated on the basis of the relationship between pseudo-crack-growth rate and energy release rate. The prediced S/N lines agree with the experimental results in all except a few cases.

  1. Guaifenesin derivatives promote neurite outgrowth and protect diabetic mice from neuropathy.

    PubMed

    Hadimani, Mallinath B; Purohit, Meena K; Vanampally, Chandrashaker; Van der Ploeg, Randy; Arballo, Victor; Morrow, Dwane; Frizzi, Katie E; Calcutt, Nigel A; Fernyhough, Paul; Kotra, Lakshmi P

    2013-06-27

    In diabetic patients, an early index of peripheral neuropathy is the slowing of conduction velocity in large myelinated neurons and a lack of understanding of the basic pathogenic mechanisms hindered therapeutics development. Racemic (R/S)-guaifenesin (1) was identified as a potent enhancer of neurite outgrowth using an in vitro screen. Its R-enantiomer (R)-1 carried the most biological activity, whereas the S-enantiomer (S)-1 was inactive. Focused structural variations to (R/S)-1 was conducted to identify potentially essential groups for the neurite outgrowth activity. In vivo therapeutic studies indicated that both (R/S)-1 and (R)-1 partially prevented motor nerve conduction velocity slowing in a mouse model of type 1 diabetes. In vitro microsomal assays suggested that compounds (R)-1 and (S)-1 are not metabolized rapidly, and PAMPA assay indicated moderate permeability through the membrane. Findings revealed here could lead to the development of novel drugs for diabetic neuropathy.

  2. Bond Tension in Tethered Macromolecules

    PubMed Central

    Sheiko, Sergei S.; Panyukov, Sergey; Rubinstein, Michael

    2016-01-01

    The paper presents scaling analysis of mechanical tension generated in densely branched macromolecules tethered to a solid substrate with a short linker. Steric repulsion between branches results in z-fold amplification of tension in the linker, where z is the number of chain-like arms. At large z ~ 100–1000, the generated tension may exceed the strength of covalent bonds and sever the linker. Two types of molecular architectures were considered: polymer stars and polymer “bottlebrushes” tethered to a solid substrate. Depending on the grafting density, one distinguishes the so-called mushroom, loose grafting, and dense grafting regimes. In isolated (mushroom) and loosely tethered bottlebrushes, the linker tension is by a factor of z smaller than the tension in a tethered star with the same number of arms z. In densely tethered stars, the effect of interchain distance (d) and number of arms (z) on the magnitude of linker tension is given by f ≅ f0z3/2(b/d) for stars in a solvent environment and f ≅ f0z2 (b/d)2 for dry stars, where b is the Kuhn length and f0 ≅ kBT/b is intrinsic bond tension. These relations are also valid for tethered bottlebrushes with long side chains. However, unlike molecular stars, bottlebrushes demonstrate variation of tension along the backbone f ≅ f0s z1/2 / d as a function of distance s from the free end of the backbone. In dense brushes (d≅bz) with z ≅ 1000, the backbone tension increases from f ≅ f0 = 1 pN at the free end of the backbone (s ≅ b) to its maximum f ≅ zf0 ≅ 1 nN at the linker to the substrate (s ≅ zb). PMID:27516626

  3. Bond Tension in Tethered Macromolecules.

    PubMed

    Sheiko, Sergei S; Panyukov, Sergey; Rubinstein, Michael

    2011-06-14

    The paper presents scaling analysis of mechanical tension generated in densely branched macromolecules tethered to a solid substrate with a short linker. Steric repulsion between branches results in z-fold amplification of tension in the linker, where z is the number of chain-like arms. At large z ~ 100-1000, the generated tension may exceed the strength of covalent bonds and sever the linker. Two types of molecular architectures were considered: polymer stars and polymer "bottlebrushes" tethered to a solid substrate. Depending on the grafting density, one distinguishes the so-called mushroom, loose grafting, and dense grafting regimes. In isolated (mushroom) and loosely tethered bottlebrushes, the linker tension is by a factor of [Formula: see text] smaller than the tension in a tethered star with the same number of arms z. In densely tethered stars, the effect of interchain distance (d) and number of arms (z) on the magnitude of linker tension is given by f ≅ f0z(3/2)(b/d) for stars in a solvent environment and f ≅ f0z(2) (b/d)(2) for dry stars, where b is the Kuhn length and f0 ≅ kBT/b is intrinsic bond tension. These relations are also valid for tethered bottlebrushes with long side chains. However, unlike molecular stars, bottlebrushes demonstrate variation of tension along the backbone f ≅ f0s z(1/2) / d as a function of distance s from the free end of the backbone. In dense brushes [Formula: see text] with z ≅ 1000, the backbone tension increases from f ≅ f0 = 1 pN at the free end of the backbone (s ≅ b) to its maximum f ≅ zf0 ≅ 1 nN at the linker to the substrate (s ≅ zb).

  4. Serum- and substratum-dependent modulation of neuritic growth.

    PubMed

    Skaper, S D; Selak, I; Varon, S

    1983-01-01

    Explants of embryonic day 8 (E8) chicken dorsal root ganglia (DRG) have been cultured with medium containing serum or the serum-free supplement N1 on one of three substrata: collagen, polyornithine (PORN), or PORN exposed to a polyornithine-binding neurite-promoting factor (PNPF-PORN). Replicate cultures were maintained with or without nerve growth factor (NGF). NGF elicited its classical neuritic outgrowth on all three substrata in serum-containing or serum-free medium. In the absence of NGF, however, a gradation of increasing neurite growth was seen with: PNPF-PORN greater than PORN greater than collagen. This response occurred in both media. In addition, the neuritic halo in each instance was markedly more developed in the absence of serum, especially on PNPF-PORN. Nonneuronal behaviors reflected both serum and substratum influences: thus, nonneuronal outgrowth consisted mainly of flat cells with serum and collagen, was nonexistent with serum and PORN or PNPF-PORN, and involved mostly Schwann-like scattered cells in the absence of serum on any one substratum. The serum-dependent behaviors of ganglionic neurites were examined further with explants from chicken E11 sympathetic ganglia. A single substratum was used (PORN), without exogenous trophic factor. Neurite outgrowth was depressed by the presence of fetal calf serum, thus supporting the generality of this phenomenon. Lastly, PC12 cells, a clonal line of rat pheochromocytoma, will grow neurites in the presence of NGF after 48 hr in serum-free, but not serum-containing media. Addition of serum to serum-free cultures at this time results in the rapid and complete retraction of neurites.

  5. An anisotropic hyperelastic constitutive model of brain white matter in biaxial tension and structural-mechanical relationships.

    PubMed

    Labus, Kevin M; Puttlitz, Christian M

    2016-09-01

    Computational models of the brain require accurate and robust constitutive models to characterize the mechanical behavior of brain tissue. The anisotropy of white matter has been previously demonstrated; however, there is a lack of data describing the effects of multi-axial loading, even though brain tissue experiences multi-axial stress states. Therefore, a biaxial tensile experiment was designed to more fully characterize the anisotropic behavior of white matter in a quasi-static loading state, and the mechanical data were modeled with an anisotropic hyperelastic continuum model. A probabilistic analysis was used to quantify the uncertainty in model predictions because the mechanical data of brain tissue can show a high degree of variability, and computational studies can benefit from reporting the probability distribution of model responses. The axonal structure in white matter can be heterogeneous and regionally dependent, which can affect computational model predictions. Therefore, corona radiata and corpus callosum regions were tested, and histology and transmission electron microscopy were performed on tested specimens to relate the distribution of axon orientations and the axon volume fraction to the mechanical behavior. These measured properties were implemented into a structural constitutive model. Results demonstrated a significant, but relatively low anisotropic behavior, yet there were no conclusive mechanical differences between the two regions tested. The inclusion of both biaxial and uniaxial tests in model fits improved the accuracy of model predictions. The mechanical anisotropy of individual specimens positively correlated with the measured axon volume fraction, and, accordingly, the structural model exhibited slightly decreased uncertainty in model predictions compared to the model without structural properties.

  6. Experimental Investigation of Mechanical Behavior of an Oxide/Oxide Ceramic Composite in Interlaminar Shear and under Combined Tension-Torsion Loading

    DTIC Science & Technology

    2014-03-27

    SHEAR AND UNDER COMBINED TENSION- TORSION LOADING THESIS Skyler R. Hilburn, Captain, USAF AFIT-ENY-14-M-26 DEPARTMENT OF THE AIR...OXIDE/OXIDE CERAMIC COMPOSITE IN INTERLAMINAR SHEAR AND UNDER COMBINED TENSION- TORSION LOADING THESIS Presented to the Faculty Department of...MECHNICAL BEHAVIOR OF AN OXIDE/OXIDE CERAMIC COMPOSITE IN INTERLAMINAR SHEAR AND UNDER COMBINED TENSION- TORSION LOADING Skyler R. Hilburn

  7. Both the C1 domain and a basic amino acid cluster at the C-terminus are important for the neurite and branch induction ability of DGKβ.

    PubMed

    Kano, Takuya; Kouzuki, Takeshi; Mizuno, Satoru; Ueda, Shuji; Yamanoue, Minoru; Sakane, Fumio; Saito, Naoaki; Shirai, Yasuhito

    2014-04-25

    We previously reported that diacylglycerol kinase β (DGKβ) induces neurites and branches, contributing to higher brain function including emotion and memories. However, the detailed molecular mechanism of DGKβ function remains unknown. Therefore, we constructed various mutants of DGKβ and compared their enzyme activity, intracellular localization, and ability to induce neurites and branching in SH-SY5Y cells. Even when RVH-domain and EF-hand motif were deleted, the mutant showed similar plasma membrane localization and neurite induction compared to wild type (WT), although the kinase activity of the mutant was three times higher than that of WT. In contrast, further deletion of C1 domain reduced the activity to 50% and abolished plasma membrane localization and neurite induction ability. When 34 amino acids were deleted from C-terminus, the mutants completely lost enzyme activity, plasma membrane localization, and the ability to induce neurites. A kinase-negative mutant of DGKβ retained plasma membrane localization and induced significant neurites and branches; however, the rate of induction was weaker than that of WT. Furthermore, C1A and C1B mutants, which have a mutation in a cysteine residue in the C1A or C1B domain, and the RK/E mutant, which has substitutions of arginine and lysine to glutamic acid in a cluster of basic amino acids at the C-terminus, lost their plasma membrane localization and neurite induction ability. These results indicate that in addition to kinase activity, plasma membrane localization via the C1 domain and basic amino acids at the C-terminus were indispensable for neurite induction by DGKβ. Copyright © 2014 Elsevier Inc. All rights reserved.

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

    PubMed

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

    2009-07-07

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

  9. Neurite Outgrowth in PC12 Cells Stimulated by Components from Dendranthema × grandiflorum cv. “Mottenohoka” Is Enhanced by Suppressing Phosphorylation of p38MAPK

    PubMed Central

    Kimura, Hirokazu; Tsukagoshi, Hiroyuki; Kozawa, Kunihisa; Koketsu, Mamoru; Ninomiya, Masayuki; Furukawa, Shoei

    2013-01-01

    Components from Dendranthema × grandiflorum cv. “Mottenohoka” that promote neurite outgrowth of PC12 cells were identified and the mechanism of neurite outgrowth stimulated by isolated components was studied. Components that promoted the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK 1/2) of PC12 cells were isolated. From various structural analyses, the active components were identified as acacetin and luteolin. The effects of acacetin or luteolin on PC12 cells were evaluated by electro-blotting and immunostaining. Slight neurite outgrowth in PC12 cells was observed within 2 days of culture after stimulation by luteolin or acacetin. However, NGF-stimulation induced remarkable neurite outgrowth in comparison. Neurite outgrowth by luteolin or acacetin was significantly enhanced by pretreatment with SB203580 (a p38MAPK inhibitor). The results of this study into the phosphorylation of ERK 1/2 and p38MAPK by flavonoids suggest that the inhibition of p38MAPK phosphorylation may effectively enhance neurite outgrowth. PMID:23554829

  10. Neurite Outgrowth at the Biomimetic Interface

    PubMed Central

    Kofron, Celinda M.; Liu, Yu-Ting; López-Fagundo, Cristina Y.; Mitchel, Jennifer A.; Hoffman-Kim, Diane

    2010-01-01

    Understanding the cues that guide axons and how we can optimize these cues to achieve directed neuronal growth is imperative for neural tissue engineering. Cells in the local environment influence neurons with a rich combination of cues. This study deconstructs the complex mixture of guidance cues by working at the biomimetic interface - isolating the topographical information presented by cells and determining its capacity to guide neurons. We generated replica materials presenting topographies of oriented astrocytes (ACs), endothelial cells (ECs), and Schwann cells (SCs) as well as computer-aided design materials inspired by the contours of these cells (bioinspired-CAD). These materials presented distinct topographies and anisotropies and in all cases were sufficient to guide neurons. Dorsal root ganglia (DRG) cells and neurites demonstrated the most directed response on bioinspired-CAD materials which presented anisotropic features with 90° edges. DRG alignment was strongest on SC bioinspired-CAD materials followed by AC bioinspired-CAD materials, with more uniform orientation to EC bioinspired-CAD materials. Alignment was strongest on SC replica materials followed by AC and EC replicas. These results suggest that the topographies of anisotropic tissue structures are sufficient for neuronal guidance. This work is discussed in the context of feature dimensions, morphology, and guidepost hypotheses. PMID:20440561

  11. SH2B1 orchestrates signaling events to filopodium formation during neurite outgrowth.

    PubMed

    Chen, Kuan-Wei; Chang, Yu-Jung; Chen, Linyi

    2015-01-01

    Morphogenesis during development is fundamental to the differentiation of several cell types. As neurite outgrowth marks neuritogenesis, formation of filopodia precede the formation of dendrites and axons. While the structure of filopodia is well-known, the initiation of filopodia during neurite outgrowth is not clear. SH2B1 is known to promote neurite outgrowth of PC12 cells, hippocampal and cortical neurons. As a signaling adaptor protein, SH2B1 interacts with several neurotrophin receptors, and regulates signaling as well as gene expression. Our recent findings suggest that SH2B1 can be recruited to the plasma membrane and F-actin fractions by IRSp53. IRSp53 bends plasma membrane and facilitates actin bundling to set the stage for filopodium formation. We further demonstrate that SH2B1-IRSp53 complexes enhance the formation of filopodia, dendrites and dendritic branches of hippocampal and cortical neurons. While the molecular mechanism underlying filopodium initiation is not clear, we propose that SH2B1-neurotrophin interacting sites may mark the putative sites of filopodium initiation.

  12. SH2B1 orchestrates signaling events to filopodium formation during neurite outgrowth

    PubMed Central

    Chen, Kuan-Wei; Chang, Yu-Jung; Chen, Linyi

    2015-01-01

    Morphogenesis during development is fundamental to the differentiation of several cell types. As neurite outgrowth marks neuritogenesis, formation of filopodia precede the formation of dendrites and axons. While the structure of filopodia is well-known, the initiation of filopodia during neurite outgrowth is not clear. SH2B1 is known to promote neurite outgrowth of PC12 cells, hippocampal and cortical neurons. As a signaling adaptor protein, SH2B1 interacts with several neurotrophin receptors, and regulates signaling as well as gene expression. Our recent findings suggest that SH2B1 can be recruited to the plasma membrane and F-actin fractions by IRSp53. IRSp53 bends plasma membrane and facilitates actin bundling to set the stage for filopodium formation. We further demonstrate that SH2B1-IRSp53 complexes enhance the formation of filopodia, dendrites and dendritic branches of hippocampal and cortical neurons. While the molecular mechanism underlying filopodium initiation is not clear, we propose that SH2B1-neurotrophin interacting sites may mark the putative sites of filopodium initiation. PMID:26479731

  13. Contact-associated neurite outgrowth and branching of immature cortical interneurons.

    PubMed

    Sang, Qian; Tan, Seong-Seng

    2003-06-01

    When juvenile interneurons arrive at the cortical environment following tangential migration, they are faced with the task of positioning themselves in cortical space in preparation for local circuit wiring. This includes integration into different cortical layers and cessation of migration at various positions to ensure adequate coverage. Little is known about the signals or mechanisms that initiate a conversion from the migratory phenotype to the arborization phenotype. This study looks at the immediate changes in interneuron morphology after culturing for 24 h in a three-dimensional collagen gel. Immature interneurons taken from different stages of corticogenesis showed increased neurite branching and outgrowth after interneuronal contacts were made. These responses were suppressed in the presence of Slit and brain-derived neurotrophic factor (BDNF) if the interneurons were sourced from early to mid-stages of corticogenesis. However, interneurons taken from the late period of corticogenesis responded to Slit and BDNF by increasing branching and neurite outgrowth. These results suggest an initial interneuronal cell contact as a stimulus for propagating neuronal arborization that may lead to the formation of inhibitory neuronal circuits. In addition, we have identified the late corticogenetic period when interneurons are most sensitive to the neurite promoting effects of Slit and BDNF.

  14. Neurite beading is sufficient to decrease the apparent diffusion coefficient after ischemic stroke.

    PubMed

    Budde, Matthew D; Frank, Joseph A

    2010-08-10

    Diffusion-weighted MRI (DWI) is a sensitive and reliable marker of cerebral ischemia. Within minutes of an ischemic event in the brain, the microscopic motion of water molecules measured with DWI, termed the apparent diffusion coefficient (ADC), decreases within the infarcted region. However, although the change is related to cell swelling, the precise pathological mechanism remains elusive. We show that focal enlargement and constriction, or beading, in axons and dendrites are sufficient to substantially decrease ADC. We first derived a biophysical model of neurite beading, and we show that the beaded morphology allows a larger volume to be encompassed within an equivalent surface area and is, therefore, a consequence of osmotic imbalance after ischemia. The DWI experiment simulated within the model revealed that intracellular ADC decreased by 79% in beaded neurites compared with the unbeaded form. To validate the model experimentally, excised rat sciatic nerves were subjected to stretching, which induced beading but did not cause a bulk shift of water into the axon (i.e., swelling). Beading-induced changes in cell-membrane morphology were sufficient to significantly hinder water mobility and thereby decrease ADC, and the experimental measurements were in excellent agreement with the simulated values. This is a demonstration that neurite beading accurately captures the diffusion changes measured in vivo. The results significantly advance the specificity of DWI in ischemia and other acute neurological injuries and will greatly aid the development of treatment strategies to monitor and repair damaged brain in both clinical and experimental settings.

  15. Modeling extracellular electrical stimulation: I. Derivation and interpretation of neurite equations.

    PubMed

    Meffin, Hamish; Tahayori, Bahman; Grayden, David B; Burkitt, Anthony N

    2012-12-01

    Neuroprosthetic devices, such as cochlear and retinal implants, work by directly stimulating neurons with extracellular electrodes. This is commonly modeled using the cable equation with an applied extracellular voltage. In this paper a framework for modeling extracellular electrical stimulation is presented. To this end, a cylindrical neurite with confined extracellular space in the subthreshold regime is modeled in three-dimensional space. Through cylindrical harmonic expansion of Laplace's equation, we derive the spatio-temporal equations governing different modes of stimulation, referred to as longitudinal and transverse modes, under types of boundary conditions. The longitudinal mode is described by the well-known cable equation, however, the transverse modes are described by a novel ordinary differential equation. For the longitudinal mode, we find that different electrotonic length constants apply under the two different boundary conditions. Equations connecting current density to voltage boundary conditions are derived that are used to calculate the trans-impedance of the neurite-plus-thin-extracellular-sheath. A detailed explanation on depolarization mechanisms and the dominant current pathway under different modes of stimulation is provided. The analytic results derived here enable the estimation of a neurite's membrane potential under extracellular stimulation, hence bypassing the heavy computational cost of using numerical methods.

  16. Schwann cell migration and neurite outgrowth are influenced by media conditioned by epineurial fibroblasts.

    PubMed

    van Neerven, S G A; Pannaye, P; Bozkurt, A; Van Nieuwenhoven, F; Joosten, E; Hermans, E; Taccola, G; Deumens, R

    2013-11-12

    The regenerative capacity of the peripheral nervous system is largely related to Schwann cells undergoing proliferation and migration after injury and forming growth-supporting substrates for severed axons. Novel data show that fibroblasts to a certain extent regulate the pro-regenerative behavior of Schwann cells. In the setting of peripheral nerve injury, the fibroblasts that form the epineurium come into close contact with both Schwann cells and peripheral axons, but the potential influence on these latter two cell types has not been studied yet. In the present study we explored whether culture media, conditioned by epineurial fibroblasts can influence Schwann cells and/or neurite outgrowth from dorsal root ganglia neurons in vitro. Our data indicate that epineurial fibroblast-conditioned culture media substantially increase Schwann cell migration and the outgrowth of neurites. Schwann cell proliferation remained largely unaffected. These same read-out parameters were assayed in a condition where epineurial fibroblasts were subjected to stretch-cell-stress, a mechanical stressor that plays an important role in traumatic peripheral nerve injuries. Stretch-cell-stress of epineurial fibroblasts did not further change the positive effects of conditioned media on Schwann cell migration and neurite outgrowth. From these data we conclude that an as yet unknown pro-regenerative role can be attributed to epineurial fibroblasts, implying that such cells may affect the outcome of severe peripheral nerve injury. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

  17. Liraglutide Promotes Cortical Neurite Outgrowth via the MEK-ERK Pathway.

    PubMed

    Li, Meng; Li, Shilun; Li, Yukun

    2015-10-01

    Liraglutide is the glucagon-like peptide-1 (GLP-1) synthetic form which has been approved by the US Food and Drug Administration to be released onto the market. The metabolic benefits of incretin hormone as an anti-diabetic agent are widely recognized, but its potential extra-pancreatic effects of GLP-1 analog (liraglutide) in the central nerve system are less well known. To this purpose, we used immunofluorescence method to examine the effect of liraglutide on neurite outgrowth in primary cortical neuron culture by measuring neurite length and confirmed the promotion effect. Then, we investigated the potential mechanisms and found that liraglutide promoted neurite outgrowth in a dose-dependant manner, and this effect could be partially inhibited by MEK-ERK inhibitor U0126. Besides, liraglutide induced an increase of p-ERK/ERK expression, which could be blocked in the presence of U0126. Similarly, phosphorylated transcription factor (p-CREB) level shared the same trend with p-ERK/ERK ratio after liraglutide treatment. Collectively, our data illustrated that that liraglutide exerts neurotrophin-like activity partly via MEK-ERK pathway, which might offer a novel idea for treatment of axon-associated neurological diseases.

  18. Pulsed electromagnetic fields potentiate neurite outgrowth in the dopaminergic MN9D cell line.

    PubMed

    Lekhraj, Rukmani; Cynamon, Deborah E; DeLuca, Stephanie E; Taub, Eric S; Pilla, Arthur A; Casper, Diana

    2014-06-01

    Pulsed electromagnetic fields (PEMF) exert biological effects and are in clinical use to facilitate bone repair and wound healing. Research has demonstrated that PEMF can induce signaling molecules and growth factors, molecules that play important roles in neuronal differentiation. Here, we tested the effects of a low-amplitude, nonthermal, pulsed radiofrequency signal on morphological neuronal differentiation in MN9D, a dopaminergic cell line. Cells were plated in medium with 10% fetal calf serum. After 1 day, medium was replaced with serum-containing medium, serum-free medium, or medium supplemented with dibutyryl cyclic adenosine monophosphate (Bt2 cAMP), a cAMP analog known to induce neurite outgrowth. Cultures were divided into groups and treated with PEMF signals for either 30 min per day or continuously for 15 min every hour for 3 days. Both serum withdrawal and Bt2 cAMP significantly increased neurite length. PEMF treatment similarly increased neurite length under both serum-free and serum-supplemented conditions, although to a lesser degree in the presence of serum, when continuous treatments had greater effects. PEMF signals also increased cell body width, indicating neuronal maturation, and decreased protein content, suggesting that this treatment was antimitotic, an effect reversed by the inhibitor of cAMP formation dideoxyadenosine. Bt2 cAMP and PEMF effects were not additive, suggesting that neurite elongation was achieved through a common pathway. PEMF signals increased cAMP levels from 3 to 5 hr after treatment, supporting this mechanism of action. Although neuritogenesis is considered a developmental process, it may also represent the plasticity required to form and maintain synaptic connections throughout life. Copyright © 2014 Wiley Periodicals, Inc.

  19. Astroglial differentiation is required for support of neurite outgrowth.

    PubMed

    Wang, L C; Baird, D H; Hatten, M E; Mason, C A

    1994-05-01

    Models of astrocyte differentiation stress a lineage program that involves a progressive loss of astroglial support of neuronal differentiation. These models predict that astroglial promotion of neurite extension declines with the "age" of the astrocyte. An alternative view is that astroglial support of neurite growth is regulated by epigenetic factors that induce the cells either to differentiate and support neuronal functions or to undergo cell proliferation and fail to support neurons. To compare the contribution of astroglial cell "age" to astroglial support of neurite extension, mouse cerebellar astroglia were maintained in vitro for 3-90 d, and assayed for their ability to support neurite formation. When cultured in isolation, astroglial support of neurite extension declined with time in vitro, as assayed by quantifying outgrowth from explants of pontine nuclei, falling from a robust level just after the astroglia were harvested to negligible levels 21-90 d later. Since previous studies have shown that neurons can change the state of astroglial cells (Hatten, 1985), we tested the neurite promoting activity of astroglia that were cultured for 21-90 d in vitro and subsequently induced to differentiate by the addition of neurons. When granule neurons were added to aged astroglia and pontine explants plated 2 d later, neurite growth from the explants was exuberant, regardless of the time astroglia spent in vitro prior to the addition of neurons. The state of astroglia that were growth promoting or growth inhibiting was examined by bromodeoxyuridine staining and with antisera to glial filament protein. Aged astroglia cultured alone and thus inhibitory to axon growth, proliferated at high rates and had polygonal shapes. In contrast, aged astroglia to which neurons had been added, proliferated at low rates and developed process-bearing stellate shapes. To test further whether proliferation levels related to the growth-supporting properties of astroglia, astroglia

  20. Changing growth of neurites of sensory ganglion by terahertz radiation

    NASA Astrophysics Data System (ADS)

    Tsurkan, M. V.; Smolyanskaya, O. A.; Bespalov, V. G.; Penniyainen, V. A.; Kipenko, A. V.; Lopatina, E. V.; Krylov, B. V.

    2012-02-01

    Application of terahertz radiation for the creation of medical equipment and solving of biological problems has become widely spread. From this point of view, the influence of THz radiation on the nerve fibers is of primary concern. In addition, several studies indicated both stimulating and depressive effects on nerve cells. However, the mechanism of this effect has not yet been studied, including the dose and exposure time. Our research was devoted to the impact of broadband pulsed THz radiation in the frequency range of 0.05 to 2 THz on the neurite growth in the sensory ganglia of 10-12-day chicken embryos. Dependence of changes in functional responses of cells on the average output power has been found. An increase in the stimulating effect was observed at the lowest power density used (0.5 μW/cm2). Through non-destructive process and choosing the correct parameters of THz radiation, potential control of neural response becomes possible, which can subsequently lead to new medical treatments.

  1. Mechanical analysis of the strains generated by water tension in plant stems. Part I: stress transmission from the water to the cell walls.

    PubMed

    Alméras, Tancrède; Gril, Joseph

    2007-11-01

    Plant tissues shrink and swell in response to changes in water pressure. These strains can be easily measured, e.g., at the surface of tree stems, to obtain indirect information about plant water status and other physiological parameters. We developed a mechanical model to clarify how water pressure is transmitted to cell walls and causes shrinkage of plant tissues, particularly in the case of thick-walled cells such as wood fibers. Our analysis shows that the stress inside the fiber cell walls is lower than the water tension. The difference is accounted for by a stress transmission factor that depends on two main effects. The first effect is the dilution of the stress through the cell wall, because water acts at the lumen border and is transmitted to the outer border of the cell, which has a larger circumference. The second effect is the partial conversion of radial stress into tangential stress. Both effects are quantified as functions of parameters of the cell wall structure and its mechanical properties.

  2. Contact inhibition of locomotion and mechanical cross-talk between cell–cell and cell–substrate adhesion determine the pattern of junctional tension in epithelial cell aggregates

    PubMed Central

    Coburn, Luke; Lopez, Hender; Caldwell, Benjamin J.; Moussa, Elliott; Yap, Chloe; Priya, Rashmi; Noppe, Adrian; Roberts, Anthony P.; Lobaskin, Vladimir; Yap, Alpha S.; Neufeld, Zoltan; Gomez, Guillermo A.

    2016-01-01

    We used a computational approach to analyze the biomechanics of epithelial cell aggregates—islands, stripes, or entire monolayers—that combines both vertex and contact-inhibition-of-locomotion models to include cell–cell and cell–substrate adhesion. Examination of the distribution of cell protrusions (adhesion to the substrate) in the model predicted high-order profiles of cell organization that agree with those previously seen experimentally. Cells acquired an asymmetric distribution of basal protrusions, traction forces, and apical aspect ratios that decreased when moving from the edge to the island center. Our in silico analysis also showed that tension on cell–cell junctions and apical stress is not homogeneous across the island. Instead, these parameters are higher at the island center and scale up with island size, which we confirmed experimentally using laser ablation assays and immunofluorescence. Without formally being a three-dimensional model, our approach has the minimal elements necessary to reproduce the distribution of cellular forces and mechanical cross-talk, as well as the distribution of principal stress in cells within epithelial cell aggregates. By making experimentally testable predictions, our approach can aid in mechanical analysis of epithelial tissues, especially when local changes in cell–cell and/or cell–substrate adhesion drive collective cell behavior. PMID:27605701

  3. Experimental observations on mechanical response of three-phase NiTi shape memory alloy under uniaxial tension

    NASA Astrophysics Data System (ADS)

    Xiao, Yao; Zeng, Pan; Lei, Liping

    2016-10-01

    In this paper, the mechanical behavior of three-phase NiTi shape memory alloy (SMA) is examined in a wide temperature range using in situ digital image correlation. By varying the temperature and the cooling/heating history, we get the specimens with initial austenite (A), initial R-phase (R), initial martensite (M), initial mixture of A and R, initial mixture of R and M and initial mixture of A and M. It is observed in the experiments that NiTi SMA exhibits localized A → M transformation and R → M transformation while homogenous R-reorientation and martensitic reorientation. Moreover, the influence of the initial mixed states, i.e. mixture of A and M, mixture of R and M and mixture of A and R, on the mechanical response of NiTi SMA is discussed. Interestingly, we find that the specimens with initial mixture of R and M demonstrate homogenous deformation manner and the emergence of R in M facilitates the transformation of NiTi SMA greatly. The three-phase phase diagram is also established. The thermal dependences of the critical transformation stresses associated with various transformation processes are calculated for further theoretical investigation and simulation.

  4. [Tension pneumocephalus secondary to non-invasive mechanical ventilation in a patient with severe traumatic brain injury].

    PubMed

    Andreu-Ruiz, Antonio; Ros-Argente Del Castillo, Tomas; Moya-Sánchez, José; Garcia-Ortega, Ana Azahara

    2017-09-28

    The presence of air inside intracranial cavity is a rare entity known as pneumocephalus and in most cases doesńt present any clinical repercussion except in case of elevated intracranial pressure that can lead to a decreasing level of consciousness, coma and even death. We present a rare case of a young male, without medical precedents of interest, hospitalized in an intensive care unit for vigilance after a traffic accident with asymptomatic crane encephalic trauma and cranial computerized tomography without meaningful findings. During the intensive care unit stay positive pressure is applied in airway with non-invasive mechanical ventilation that produces air entrance in cranial cavity (pneumocephalus) causing neurological deterioration and necessity of urgent surgery. Copyright © 2017 Sociedad Española de Neurocirugía. Publicado por Elsevier España, S.L.U. All rights reserved.

  5. Skin tension related to tension reduction sutures.

    PubMed

    Hwang, Kun; Kim, Han Joon; Kim, Kyung Yong; Han, Seung Ho; Hwang, Se Jin

    2015-01-01

    The aim of this study was to compare the skin tension of several fascial/subcutaneous tensile reduction sutures. Six upper limbs and 8 lower limbs of 4 fresh cadavers were used. At the deltoid area (10 cm below the palpable acromion) and lateral thigh (midpoint from the palpable greater trochanter to the lateral border of the patella), and within a 3 × 6-cm fusiform area of skin, subcutaneous tissue defects were created. At the midpoint of the defect, a no. 5 silk suture was passed through the dermis at a 5-mm margin of the defect, and the defect was approximated. The initial tension to approximate the margins was measured using a tensiometer.The tension needed to approximate skin without any tension reduction suture (S) was 6.5 ± 4.6 N (Newton). The tensions needed to approximate superficial fascia (SF) and deep fascia (DF) were 7.8 ± 3.4 N and 10.3 ± 5.1 N, respectively. The tension needed to approximate the skin after approximating the SF was 4.1 ± 3.4 N. The tension needed to approximate the skin after approximating the DF was 4.9 ± 4.0 N. The tension reduction effect of approximating the SF was 38.8 ± 16.4% (2.4 ± 1.5 N, P = 0.000 [ANOVA, Scheffé]). The tension reduction effect of approximating the DF was 25.2% ± 21.9% (1.5 ± 1.4 N, P = 0.001 [ANOVA, Scheffé]). The reason for this is thought to be that the SF is located closely to the skin unlike the DF. The results of this study might be a basis for tension reduction sutures.

  6. Flow in porous media, phase behavior and ultralow interfacial tensions: mechanisms of enhanced petroleum recovery. Final technical report

    SciTech Connect

    Davis, H.T.; Scriven, L.E.

    1982-01-01

    A major program of university research, longer-ranged and more fundamental in approach than industrial research, into basic mechanisms of enhancing petroleum recovery and into underlying physics, chemistry, geology, applied mathematics, computation, and engineering science has been built at Minnesota. The 1982 outputs of the interdisciplinary team of investigators were again ideas, instruments, techniques, data, understanding and skilled people: forty-one scientific and engineering papers in leading journals; four pioneering Ph.D. theses; numerous presentations to scientific and technical meetings, and to industrial, governmental and university laboratories; vigorous program of research visits to and from Minnesota; and two outstanding Ph.D.'s to research positions in the petroleum industry, one to a university faculty position, one to research leadership in a governmental institute. This report summarizes the 1982 papers and theses and features sixteen major accomplishments of the program during that year. Abstracts of all forty-five publications in the permanent literature are appended. Further details of information transfer and personnel exchange with industrial, governmental and university laboratories appear in 1982 Quarterly Reports available from the Department of Energy and are not reproduced here. The Minnesota program continues in 1983, notwithstanding earlier uncertainty about the DOE funding which finally materialized and is the bulk of support. Supplemental grants-in-aid from nine companies in the petroleum industry are important, as are the limited University and departmental contributions. 839 references, 172 figures, 29 tables.

  7. Endochondral growth in growth plates of three species at two anatomical locations modulated by mechanical compression and tension.

    PubMed

    Stokes, Ian A F; Aronsson, David D; Dimock, Abigail N; Cortright, Valerie; Beck, Samantha

    2006-06-01

    Sustained mechanical loading alters longitudinal growth of bones, and this growth sensitivity to load has been implicated in progression of skeletal deformities during growth. The objective of this study was to quantify the relationship between altered growth and different magnitudes of sustained altered stress in a diverse set of nonhuman growth plates. The sensitivity of endochondral growth to differing magnitudes of sustained compression or distraction stress was measured in growth plates of three species of immature animals (rats, rabbits, calves) at two anatomical locations (caudal vertebra and proximal tibia) with two different ages of rats and rabbits. An external loading apparatus was applied for 8 days, and growth was measured as the distance between fluorescent markers administered 24 and 48 h prior to euthanasia. An apparently linear relationship between stress and percentage growth modulation (percent difference between loaded and control growth plates) was found, with distraction accelerating growth and compression slowing growth. The growth-rate sensitivity to stress was between 9.2 and 23.9% per 0.1 MPa for different growth plates and averaged 17.1% per 0.1 MPa. The growth-rate sensitivity to stress differed between vertebrae and the proximal tibia (15 and 18.6% per 0.1 MPa, respectively). The range of control growth rates of different growth plates was large (30 microns/day for rat vertebrae to 366 microns/day for rabbit proximal tibia). The relatively small differences in growth-rate sensitivity to stress for a diverse set of growth plates suggest that these results might be generalized to other growth plates, including human. These data may be applicable to planning the management of progressive deformities in patients having residual growth.

  8. ENDOCHONDRAL GROWTH IN GROWTH PLATES OF THREE SPECIES AT TWO ANATOMICAL LOCATIONS MODULATED BY MECHANICAL COMPRESSION AND TENSION

    PubMed Central

    Stokes, Ian A.F.; Aronsson, David D.; Dimock, Abigail N.; Cortright, Valerie; Beck., Samantha

    2006-01-01

    SUMMARY Purpose Sustained mechanical loading alters longitudinal growth of bones, and this growth sensitivity to load has been implicated in progression of skeletal deformities during growth. The objective of this study was to quantify the relationship between altered growth and different magnitudes of sustained altered stress in a diverse set of non-human growth plates. Methods The sensitivity of endochondral growth to differing magnitudes of sustained compression or distraction stress was measured in growth plates of three species of immature animals (rats, rabbits, calves) at two anatomical locations (caudal vertebra and proximal tibia) with two different ages of rats and rabbits. An external loading apparatus was applied for eight days and growth was measured as the distance between fluorescent markers administered 24 and 48 hours prior to euthanasia. Results An apparently linear relationship between stress and percentage growth modulation (percent difference between loaded and control growth plates) was found, with distraction accelerating growth and compression slowing growth. The growth-rate sensitivity to stress was between 9.2 and 23.9% per 0.1 MPa for different growth plates, and averaged 17.1% per 0.1 MPa. The growth-rate sensitivity to stress differed between vertebrae and the proximal tibia (15 and 18.6 percent per 0.1 MPa respectively). The range of control growth rates of different growth plates was large (30 microns/day for rat vertebrae to 366 microns/day for rabbit proximal tibia). Conclusions The relatively small differences in growth-rate sensitivity to stress for a diverse set of growth plates suggests that these results might be generalized to other growth plates, including human. These data may be applicable to planning the management of progressive deformities in patients having residual growth. PMID:16705695

  9. Demonstration of Surface Tension.

    ERIC Educational Resources Information Center

    Rosenthal, Andrew J.

    2001-01-01

    Surface tension is a fundamental obstacle in the spontaneous formation of bubbles, droplets, and crystal nuclei in liquids. Describes a simple overhead projector demonstration that illustrates the power of surface tension that can prevent so many industrial processes. (ASK)

  10. Demonstration of Surface Tension.

    ERIC Educational Resources Information Center

    Rosenthal, Andrew J.

    2001-01-01

    Surface tension is a fundamental obstacle in the spontaneous formation of bubbles, droplets, and crystal nuclei in liquids. Describes a simple overhead projector demonstration that illustrates the power of surface tension that can prevent so many industrial processes. (ASK)

  11. Ultrafast optical recording reveals distinct capsaicin-induced ion dynamics along single nociceptive neurite terminals in vitro

    NASA Astrophysics Data System (ADS)

    Goldstein, Robert H.; Katz, Ben; Lev, Shaya; Binshtok, Alexander M.

    2017-07-01

    Pain signals are detected by terminals of nociceptive peripheral fibers situated among the keratinocytes and epithelial cells. Despite being key structures for pain-related stimuli detection and transmission, little is known about the functional organization of terminals. This is mainly due to their minute size, rendering them largely inaccessible by conventional experimental approaches. Here, we report the implementation of an ultrafast optical recording approach for studying cultured neurite terminals, which are readily accessible for assay manipulations. Using this approach, we were able to study capsaicin-induced calcium and sodium dynamics in the nociceptive processes, at a near-action potential time resolution. The approach was sensitive enough to detect differences in latency, time-to-peak, and amplitude of capsaicin-induced ion transients along the terminal neurites. Using this approach, we found that capsaicin evokes distinctive calcium signals along the neurite. At the terminal, the signal was insensitive to voltage-gated sodium channel blockers, and showed slower kinetics and smaller signal amplitudes, compared with signals that were measured further up the neurite. These latter signals were mainly abolished by sodium channel blockers. We propose this ultrafast optical recording approach as a model for studying peripheral terminal signaling, forming a basis for studying pain mechanisms in normal and pathological states.

  12. Comparative sensitivity of human and rat neural cultures to chemical-induced inhibition of neurite outgrowth

    SciTech Connect

    Harrill, Joshua A.; Freudenrich, Theresa M.; Robinette, Brian L.; Mundy, William R.

    2011-11-15

    There is a need for rapid, efficient and cost-effective alternatives to traditional in vivo developmental neurotoxicity testing. In vitro cell culture models can recapitulate many of the key cellular processes of nervous system development, including neurite outgrowth, and may be used as screening tools to identify potential developmental neurotoxicants. The present study compared primary rat cortical cultures and human embryonic stem cell-derived neural cultures in terms of: 1) reproducibility of high content image analysis based neurite outgrowth measurements, 2) dynamic range of neurite outgrowth measurements and 3) sensitivity to chemicals which have been shown to inhibit neurite outgrowth. There was a large increase in neurite outgrowth between 2 and 24 h in both rat and human cultures. Image analysis data collected across multiple cultures demonstrated that neurite outgrowth measurements in rat cortical cultures were more reproducible and had higher dynamic range as compared to human neural cultures. Human neural cultures were more sensitive than rat cortical cultures to chemicals previously shown to inhibit neurite outgrowth. Parallel analysis of morphological (neurite count, neurite length) and cytotoxicity (neurons per field) measurements were used to detect selective effects on neurite outgrowth. All chemicals which inhibited neurite outgrowth in rat cortical cultures did so at concentrations which did not concurrently affect the number of neurons per field, indicating selective effects on neurite outgrowth. In contrast, more than half the chemicals which inhibited neurite outgrowth in human neural cultures did so at concentrations which concurrently decreased the number of neurons per field, indicating that effects on neurite outgrowth were secondary to cytotoxicity. Overall, these data demonstrate that the culture models performed differently in terms of reproducibility, dynamic range and sensitivity to neurite outgrowth inhibitors. While human neural

  13. Integrin-mediated neurite outgrowth in neuroblastoma cells depends on the activation of potassium channels

    PubMed Central

    1993-01-01

    Electrical signals elicited by integrin interaction with ECM components and their role in neurite outgrowth were studied in two clones (N1 and N7) isolated from 41A3 murine neuroblastoma cell line. Although the two clones similarly adhered to fibronectin (FN) and vitronectin (VN), this adhesion induced neurite outgrowth in N1 but not in N7 cells. Patch clamp recordings in whole cell configuration showed that, upon adhesion to FN or VN but not to platelet factor 4 (PF4), N1 cells undergo a marked (approximately equal to 20 mV) hyperpolarization of the resting potential (Vrest) that occurred within the first 20 min after cell contact with ECM, and persisted for approximately 1 h before reverting to the time zero values. This hyperpolarization was totally absent in N7 cells. A detailed analysis of the molecular mechanisms involved in N1 and N7 cell adhesion to ECM substrata was performed by using antibodies raised against the FN receptor and synthetic peptides variously competing with the FN or VN binding to integrin receptor (GRGDSP and GRGESP). Antibodies, as well as GRGDSP, abolished adhesion of N1 and N7 clones to FN and VN, revealing a similar implication of integrins in the adhesion of these clones to the ECM proteins. However, these anti-adhesive treatments, while ineffective on Vrest of N7 cells, abolished in N1 cells the FN- or VN-induced hyperpolarization and neurite outgrowth, that appeared therefore strictly associated and integrin-mediated phenomena. The nature of this association was deepened through a comparative analysis of the integrin profiles and the ion channels of N1 and N7 cells. The integrin immunoprecipitation profile resulted very similarly in the two clones, with only minor differences concerning the alpha V containing complexes. Both clones possessed Ca2+ and K+ delayed rectifier (KDR) channels, while only N1 cells were endowed with inward rectifier K+ (KIR) channels. The latter governed the Vrest, and, unlike KDR channels, were blocked by

  14. Alpha-Synuclein affects neurite morphology, autophagy, vesicle transport and axonal degeneration in CNS neurons

    PubMed Central

    Koch, J C; Bitow, F; Haack, J; d'Hedouville, Z; Zhang, J-N; Tönges, L; Michel, U; Oliveira, L M A; Jovin, T M; Liman, J; Tatenhorst, L; Bähr, M; Lingor, P

    2015-01-01

    Many neuropathological and experimental studies suggest that the degeneration of dopaminergic terminals and axons precedes the demise of dopaminergic neurons in the substantia nigra, which finally results in the clinical symptoms of Parkinson disease (PD). The mechanisms underlying this early axonal degeneration are, however, still poorly understood. Here, we examined the effects of overexpression of human wildtype alpha-synuclein (αSyn-WT), a protein associated with PD, and its mutant variants αSyn-A30P and -A53T on neurite morphology and functional parameters in rat primary midbrain neurons (PMN). Moreover, axonal degeneration after overexpression of αSyn-WT and -A30P was analyzed by live imaging in the rat optic nerve in vivo. We found that overexpression of αSyn-WT and of its mutants A30P and A53T impaired neurite outgrowth of PMN and affected neurite branching assessed by Sholl analysis in a variant-dependent manner. Surprisingly, the number of primary neurites per neuron was increased in neurons transfected with αSyn. Axonal vesicle transport was examined by live imaging of PMN co-transfected with EGFP-labeled synaptophysin. Overexpression of all αSyn variants significantly decreased the number of motile vesicles and decelerated vesicle transport compared with control. Macroautophagic flux in PMN was enhanced by αSyn-WT and -A53T but not by αSyn-A30P. Correspondingly, colocalization of αSyn and the autophagy marker LC3 was reduced for αSyn-A30P compared with the other αSyn variants. The number of mitochondria colocalizing with LC3 as a marker for mitophagy did not differ among the groups. In the rat optic nerve, both αSyn-WT and -A30P accelerated kinetics of acute axonal degeneration following crush lesion as analyzed by in vivo live imaging. We conclude that αSyn overexpression impairs neurite outgrowth and augments axonal degeneration, whereas axonal vesicle transport and autophagy are severely altered. PMID:26158517

  15. Shoc2/Sur8 Protein Regulates Neurite Outgrowth

    PubMed Central

    Leon, Gonzalo; Sanchez-Ruiloba, Lucia; Perez-Rodriguez, Andrea; Gragera, Teresa; Martinez, Natalia; Hernandez, Silvia; Anta, Berta; Calero, Olga; Garcia-Dominguez, Carlota A.; Dura, Lara M.; Peña-Jimenez, Daniel; Castro, Judit; Zarich, Natasha; Sanchez-Gomez, Pilar; Calero, Miguel; Iglesias, Teresa; Oliva, Jose L.; Rojas, Jose M.

    2014-01-01

    The Shoc2 protein has been implicated in the positive regulation of the Ras-ERK pathway by increasing the functional binding interaction between Ras and Raf, leading to increased ERK activity. Here we found that Shoc2 overexpression induced sustained ERK phosphorylation, notably in the case of EGF stimulation, and Shoc2 knockdown inhibited ERK activation. We demonstrate that ectopic overexpression of human Shoc2 in PC12 cells significantly promotes neurite extension in the presence of EGF, a stimulus that induces proliferation rather than differentiation in these cells. Finally, Shoc2 depletion reduces both NGF-induced neurite outgrowth and ERK activation in PC12 cells. Our data indicate that Shoc2 is essential to modulate the Ras-ERK signaling outcome in cell differentiation processes involved in neurite outgrowth. PMID:25514808

  16. Shoc2/Sur8 protein regulates neurite outgrowth.

    PubMed

    Leon, Gonzalo; Sanchez-Ruiloba, Lucia; Perez-Rodriguez, Andrea; Gragera, Teresa; Martinez, Natalia; Hernandez, Silvia; Anta, Berta; Calero, Olga; Garcia-Dominguez, Carlota A; Dura, Lara M; Peña-Jimenez, Daniel; Castro, Judit; Zarich, Natasha; Sanchez-Gomez, Pilar; Calero, Miguel; Iglesias, Teresa; Oliva, Jose L; Rojas, Jose M

    2014-01-01

    The Shoc2 protein has been implicated in the positive regulation of the Ras-ERK pathway by increasing the functional binding interaction between Ras and Raf, leading to increased ERK activity. Here we found that Shoc2 overexpression induced sustained ERK phosphorylation, notably in the case of EGF stimulation, and Shoc2 knockdown inhibited ERK activation. We demonstrate that ectopic overexpression of human Shoc2 in PC12 cells significantly promotes neurite extension in the presence of EGF, a stimulus that induces proliferation rather than differentiation in these cells. Finally, Shoc2 depletion reduces both NGF-induced neurite outgrowth and ERK activation in PC12 cells. Our data indicate that Shoc2 is essential to modulate the Ras-ERK signaling outcome in cell differentiation processes involved in neurite outgrowth.

  17. The transcription factor ATF-3 promotes neurite outgrowth.

    PubMed

    Seijffers, Rhona; Allchorne, Andrew J; Woolf, Clifford J

    2006-01-01

    Dorsal root ganglion (DRG) neurons regenerate after a peripheral nerve injury but not after injury to their axons in the spinal cord. A key question is which transcription factors drive the changes in gene expression that increase the intrinsic growth state of peripherally injured sensory neurons? A prime candidate is activating transcription factor-3 (ATF-3), a transcription factor that we find is induced in all DRG neurons after peripheral, but not central axonal injury. Moreover, we show in adult DRG neurons that a preconditioning peripheral, but not central axonal injury, increases their growth, correlating closely with the pattern of ATF-3 induction. Using viral vectors, we delivered ATF-3 to cultured adult DRG neurons and find that ATF-3 enhances neurite outgrowth. Furthermore, ATF-3 promotes long sparsely branched neurites. ATF-3 overexpression did not increase c-Jun expression. ATF-3 may contribute, therefore, to neurite outgrowth by orchestrating the gene expression responses in injured neurons.

  18. Fine Needle Aspiration Cytology in Diagnosis of Pure Neuritic Leprosy

    PubMed Central

    Kumar, Bipin; Pradhan, Anju

    2011-01-01

    Leprosy is a chronic infection affecting mainly the skin and peripheral nerve. Pure neuritic form of this disease manifests by involvement of the nerve in the absence of skin lesions. Therefore, it can sometimes create a diagnostic problem. It often requires a nerve biopsy for diagnosis, which is an invasive procedure and may lead to neural deficit. Fine needle aspiration cytology (FNAC) of an affected nerve can be a valuable and less invasive procedure for the diagnosis of such cases. We report five suspected cases of pure neuritic Hansen's disease involving the common and superficial peroneal, ulnar, and median nerve, who underwent FNAC. Smears revealed nerve fibers infiltrated by chronic inflammatory cells in all cases, presence of epithelioid cells granulomas, and Langhans giant cells in three cases, and acid fast bacilli in two cases. In conclusion, FNAC is a safe, less invasive, and time saving procedure for the diagnosis of pure neuritic leprosy. PMID:21660285

  19. Phosphorylation of Runx2, induced by cyclic mechanical tension via ERK1/2 pathway, contributes to osteodifferentiation of human periodontal ligament fibroblasts.

    PubMed

    Ren, Dapeng; Wei, Fulan; Hu, Lihua; Yang, Shuangyan; Wang, Chunling; Yuan, Xiao

    2015-10-01

    Occlusal force is an important stimulus for maintaining periodontal homeostasis. This is attributed to the quality of human periodontal ligament fibroblasts (hPDLFs) that could transfer occlusal force into biological signals modulating osteoblst differentiation. However, few studies investigated the mechanism of occlusal force-induced osteodifferentiation of hPDLFs. In our study, we used the cyclic mechanical tension (CMT) at 10% elongation with 0.5 Hz to mimic occlusal force, and explored its effects on osteogenesis of hPDLFs. Firstly, elevated expressions of several osteoblast marker genes (Runx2, ATF4, SP7, OCN, and BSP), as well as activated ERK1/2 pathway were detected during CMT loading for 1, 3, 6, 12, 18, and 24 h. To gain further insight into how CMT contributed to those effects, we focused on the classic ERK1/2-Runx2 pathway by inhibiting ERK1/2 and overexpressing Runx2. Our results reflected that Runx2 overexpression alone could induce osteodifferentiation of hPDLFs. Meanwhile, CMT loading could intensify while combined ERK1/2 blockage could weaken this process. Furthermore, we found that CMT promoted Runx2 transcription and phosphorylation via ERK1/2; protein level of phospho-Runx2 (p-Runx2), rather than Runx2, was in parallel with mRNA expressions of SP7, OCN, and BSP. Taken together, our study proved that p-Runx2, elevated by CMT via ERK1/2 pathway, is the predominate factor in promoting osteoblast differentiation of hPDLFs. © 2015 Wiley Periodicals, Inc.

  20. Automatic quantification of neurite outgrowth by means of image analysis

    NASA Astrophysics Data System (ADS)

    Van de Wouwer, Gert; Nuydens, Rony; Meert, Theo; Weyn, Barbara

    2004-07-01

    A system for quantification of neurite outgrowth in in-vitro experiments is described. The system is developed for routine use in a high-throughput setting and is therefore needs fast, cheap, and robust. It relies on automated digital microscopical imaging of microtiter plates. Image analysis is applied to extract features for characterisation of neurite outgrowth. The system is tested in a dose-response experiment on PC12 cells + Taxol. The performance of the system and its ability to measure changes on neuronal morphology is studied.

  1. Compartmentalization of central neurons in Drosophila: a new strategy of mosaic analysis reveals localization of presynaptic sites to specific segments of neurites.

    PubMed

    Löhr, Robert; Godenschwege, Tanja; Buchner, Erich; Prokop, Andreas

    2002-12-01

    Synaptogenesis in the CNS has received far less attention than the development of neuromuscular synapses, although only central synapses allow the study of neuronal postsynaptic mechanisms and display a greater variety of structural and functional features. This neglect is attributable mainly to the enormous complexity of the CNS, which makes the visualization of individual synapses on defined neuronal processes very difficult. We overcome this obstacle and demonstrate by confocal microscopy the specific arrangement of output synapses on individual neurites. These studies are performed via genetic mosaic strategies in the CNS of the fruitfly Drosophila melanogaster. First, we use targeted expression of synaptic proteins by the UAS/Gal4 system. Second, we apply a newly developed transplantation-based mosaic strategy that takes advantage of the intrinsic regulation and localization of synaptic proteins in single-cell clones. We propose the existence of three distinct neuritic compartments: (1) primary neurites that appear to form the main transport pathways and are mostly void of output synapses, (2) neuritic compartments that contain output synapses, and (3) neuritic compartments that are postsynaptic in nature. In addition we show that mutations of the kakapo gene have no obvious effect on the distribution of output synapses in the CNS, whereas neuromuscular synapses are severely reduced. This suggests that synaptogenic mechanisms in the CNS might differ from those at neuromuscular junctions.

  2. Pleurotus giganteus (Berk.) Karunarathna & K.D. Hyde: Nutritional value and in vitro neurite outgrowth activity in rat pheochromocytoma cells

    PubMed Central

    2012-01-01

    Background Drugs dedicated to alleviate neurodegenerative diseases like Parkinson’s and Alzheimer’s have always been associated with debilitating side effects. Medicinal mushrooms which harness neuropharmacological compounds offer a potential possibility for protection against such diseases. Pleurotus giganteus (formerly known as Panus giganteus) has been consumed by the indigenous people in Peninsular Malaysia for many years. Domestication of this wild mushroom is gaining popularity but to our knowledge, medicinal properties reported for this culinary mushroom are minimal. Methods The fruiting bodies P. giganteus were analysed for its nutritional values. Cytotoxicity of the mushroom’s aqueous and ethanolic extracts towards PC12, a rat pheochromocytoma cell line was assessed by using 3-[4,5-dimethythiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Neurite outgrowth stimulation assay was carried out with nerve growth factor (NGF) as control. To elucidate signaling mechanisms involved by mushroom extract-induced neurite outgrowth, treatment of specific inhibitor for MEK/ERK and PI3K signalling pathway was carried out. Results The fruiting bodies of P. giganteus were found to have high carbohydrate, dietary fibre, potassium, phenolic compounds and triterpenoids. Both aqueous and ethanolic extracts induced neurite outgrowth of PC12 cells in a dose- and time-dependant manner with no detectable cytotoxic effect. At day 3, 25 μg/ml of aqueous extract and 15 μg/ml of ethanolic extract showed the highest percentage of neurite-bearing cells, i.e. 31.7 ± 1.1% and 33.3 ± 0.9%; respectively. Inhibition treatment results suggested that MEK/ERK and PI3K/Akt are responsible for neurite outgrowth of PC12 cells stimulated by P. giganteus extract. The high potassium content (1345.7 mg/100 g) may be responsible for promoting neurite extension, too. Conclusions P. giganteus contains bioactive compounds that mimic NGF and are responsible for neurite

  3. Pleurotus giganteus (Berk.) Karunarathna & K.D. Hyde: Nutritional value and in vitro neurite outgrowth activity in rat pheochromocytoma cells.

    PubMed

    Phan, Chia-Wei; Wong, Wei-Lun; David, Pamela; Naidu, Murali; Sabaratnam, Vikineswary

    2012-07-19

    Drugs dedicated to alleviate neurodegenerative diseases like Parkinson's and Alzheimer's have always been associated with debilitating side effects. Medicinal mushrooms which harness neuropharmacological compounds offer a potential possibility for protection against such diseases. Pleurotus giganteus (formerly known as Panus giganteus) has been consumed by the indigenous people in Peninsular Malaysia for many years. Domestication of this wild mushroom is gaining popularity but to our knowledge, medicinal properties reported for this culinary mushroom are minimal. The fruiting bodies P. giganteus were analysed for its nutritional values. Cytotoxicity of the mushroom's aqueous and ethanolic extracts towards PC12, a rat pheochromocytoma cell line was assessed by using 3-[4,5-dimethythiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Neurite outgrowth stimulation assay was carried out with nerve growth factor (NGF) as control. To elucidate signaling mechanisms involved by mushroom extract-induced neurite outgrowth, treatment of specific inhibitor for MEK/ERK and PI3K signalling pathway was carried out. The fruiting bodies of P. giganteus were found to have high carbohydrate, dietary fibre, potassium, phenolic compounds and triterpenoids. Both aqueous and ethanolic extracts induced neurite outgrowth of PC12 cells in a dose- and time-dependant manner with no detectable cytotoxic effect. At day 3, 25 μg/ml of aqueous extract and 15 μg/ml of ethanolic extract showed the highest percentage of neurite-bearing cells, i.e. 31.7 ± 1.1% and 33.3 ± 0.9%; respectively. Inhibition treatment results suggested that MEK/ERK and PI3K/Akt are responsible for neurite outgrowth of PC12 cells stimulated by P. giganteus extract. The high potassium content (1345.7 mg/100 g) may be responsible for promoting neurite extension, too. P. giganteus contains bioactive compounds that mimic NGF and are responsible for neurite stimulation. Hence, this mushroom may be

  4. MARK2 Rescues Nogo-66-Induced Inhibition of Neurite Outgrowth via Regulating Microtubule-Associated Proteins in Neurons In Vitro.

    PubMed

    Zuo, Yu-Chao; Xiong, Nan-Xiang; Shen, Jian-Ying; Yu, Hua; Huang, Yi-Zhi; Zhao, Hong-Yang

    2016-11-01

    The ability of neurons in the adult mammalian central nervous system (CNS) to regenerate after injury is limited by inhibitors in CNS myelin. Nogo-66 is the most important myelin inhibitor but the mechanisms of Nogo-66 inhibition of neurite outgrowth remain poorly understood. Particularly, the relationship between Nogo-66 and microtubule-affinity regulating kinase 2 (MARK2) has not been examined. This study investigated the role of MARK2 in Nogo-66 inhibition and the function of MARK2 in neurite elongation in neurons in vitro. MARK2 and phosphorylated MARK2 at Ser212 (p-Ser212) alterations in Neuro 2a cells were assessed at different Nogo-66 exposure times; the relationships between MARK2 and microtubule-associated proteins (MAPs) were determined via the overexpression or interference of MARK2. Our study reports that Nogo-66 inhibited the expression of total MARK2 but also reduced Ser212 phosphorylation of MARK2, whereas levels of MAP1-b and tau varied depending on MARK2 overexpression or reduced expression. Furthermore, MARK2 increased the proportion of tyrosinated α-tubulin, thereby disrupting the stability of tubulin, most likely affecting axonal growth. In line with these results, overexpression of MARK2 promoted neurite elongation and therefore is able to rescue the inhibitory effect of Nogo-66 on neurite growth. In conclusion, the intracellular PKB/MARK2/MAPs/α-tubulin pathway appears to be essential for neurite elongation in neurons in vitro. These results suggest a critical role for MARK2 in overcoming Nogo-66-induced inhibition of axon outgrowth in neurons. Pharmacological activators of MARK2 may be applicable to promote successful axonal outgrowth following many types of CNS injuries.

  5. Cdc42hs Facilitates Cytoskeletal Reorganization and Neurite Outgrowth by Localizing the 58-Kd Insulin Receptor Substrate to Filamentous Actin

    PubMed Central

    Govind, Sheila; Kozma, Robert; Monfries, Clinton; Lim, Louis; Ahmed, Sohail

    2001-01-01

    Cdc42Hs is involved in cytoskeletal reorganization and is required for neurite outgrowth in N1E-115 cells. To investigate the molecular mechanism by which Cdc42Hs regulates these processes, a search for novel Cdc42Hs protein partners was undertaken by yeast two-hybrid assay. Here, we identify the 58-kD substrate of the insulin receptor tyrosine kinase (IRS-58) as a Cdc42Hs target. IRS-58 is a brain-enriched protein comprising at least four protein–protein interaction sites: a Cdc42Hs binding site, an Src homology (SH)3-binding site, an SH3 domain, and a tryptophan, tyrptophan (WW)-binding domain. Expression of IRS-58 in Swiss 3T3 cells leads to reorganization of the filamentous (F)-actin cytoskeleton, involving loss of stress fibers and formation of filopodia and clusters. In N1E-115 cells IRS-58 induces neurite outgrowth with high complexity. Expression of a deletion mutant of IRS-58, which lacks the SH3- and WW-binding domains, induced neurite extension without complexity in N1E-115 cells. In Swiss 3T3 cells and N1E-115 cells, IRS-58 colocalizes with F-actin in clusters and filopodia. An IRS-581267N mutant unable to bind Cdc42Hs failed to localize with F-actin to induce neurite outgrowth or significant cytoskeletal reorganization. These results suggest that Cdc42Hs facilitates cytoskeletal reorganization and neurite outgrowth by localizing protein complexes via adaptor proteins such as IRS-58 to F-actin. PMID:11157984

  6. cAMP response element-binding protein and Yes-associated protein form a feedback loop that promotes neurite outgrowth.

    PubMed

    Chen, Lei; Feng, Peimin; Peng, Anjiao; Qiu, Xiangmiao; Zhu, Xi; He, Shixu; Zhou, Dong

    2017-08-31

    The cAMP response element-binding (CREB) protein is a member of the CREB/activating transcription factor family that is activated by various extracellular stimuli. It has been shown that CREB-dependent transcription stimulation plays a key role in neuronal differentiation and plasticity, but the underlying mechanisms remain largely elusive. Here, we show that Yes-associated protein (YAP) is a direct target induced by CREB upon retinoic acid (RA)-induced neurite outgrowth stimuli in N2a cells. Interestingly, YAP knockout using the CRISPR/Cas9 system inhibits neuronal differentiation and reduced neurite length. We further show that YAP could directly bind to CREB via its N-terminal region, and loss of YAP results in instability of phosphorylated CREB upon neurite outgrowth stimuli. Transient expression of YAP could largely restore CREB expression and neurite outgrowth in YAP knockout cells. Together, our results suggest that CREB and YAP form a positive feedback loop that is critical to maintain the stability of phosphorylated CREB and promote neurite outgrowth. © 2017 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

  7. Nerve Growth Factor Regulates Transient Receptor Potential Vanilloid 2 via Extracellular Signal-Regulated Kinase Signaling To Enhance Neurite Outgrowth in Developing Neurons

    PubMed Central

    Cohen, Matthew R.; Johnson, William M.; Pilat, Jennifer M.; Kiselar, Janna; DeFrancesco-Lisowitz, Alicia; Zigmond, Richard E.

    2015-01-01

    Neurite outgrowth is key to the formation of functional circuits during neuronal development. Neurotrophins, including nerve growth factor (NGF), increase neurite outgrowth in part by altering the function and expression of Ca2+-permeable cation channels. Here we report that transient receptor potential vanilloid 2 (TRPV2) is an intracellular Ca2+-permeable TRPV channel upregulated by NGF via the mitogen-activated protein kinase (MAPK) signaling pathway to augment neurite outgrowth. TRPV2 colocalized with Rab7, a late endosome protein, in addition to TrkA and activated extracellular signal-regulated kinase (ERK) in neurites, indicating that the channel is closely associated with signaling endosomes. In line with these results, we showed that TRPV2 acts as an ERK substrate and identified the motifs necessary for phosphorylation of TRPV2 by ERK. Furthermore, neurite length, TRPV2 expression, and TRPV2-mediated Ca2+ signals were reduced by mutagenesis of these key ERK phosphorylation sites. Based on these findings, we identified a previously uncharacterized mechanism by which ERK controls TRPV2-mediated Ca2+ signals in developing neurons and further establish TRPV2 as a critical intracellular ion channel in neuronal function. PMID:26416880

  8. c-Jun Amino-Terminal Kinase is Involved in Valproic Acid-Mediated Neuronal Differentiation of Mouse Embryonic NSCs and Neurite Outgrowth of NSC-Derived Neurons.

    PubMed

    Lu, Lu; Zhou, Hengxing; Pan, Bin; Li, Xueying; Fu, Zheng; Liu, Jun; Shi, Zhongju; Chu, Tianci; Wei, Zhijian; Ning, Guangzhi; Feng, Shiqing

    2017-04-01

    Valproic acid (VPA), an anticonvulsant and mood-stabilizing drug, can induce neuronal differentiation, promote neurite extension and exert a neuroprotective effect in central nervous system (CNS) injuries; however, comparatively little is known regarding its action on mouse embryonic neural stem cells (NSCs) and the underlying molecular mechanism. Recent studies suggested that c-Jun N-terminal kinase (JNK) is required for neurite outgrowth and neuronal differentiation during neuronal development. In the present study, we cultured mouse embryonic NSCs and treated the cells with 1 mM VPA for up to 7 days. The results indicate that VPA promotes the neuronal differentiation of mouse embryonic NSCs and neurite outgrowth of NSC-derived neurons; moreover, VPA induces the phosphorylation of c-Jun by JNK. In contrast, the specific JNK inhibitor SP600125 decreased the VPA-stimulated increase in neuronal differentiation of mouse embryonic NSCs and neurite outgrowth of NSC-derived neurons. Taken together, these results suggest that VPA promotes neuronal differentiation of mouse embryonic NSCs and neurite outgrowth of NSC-derived neurons. Moreover, JNK activation is involved in the effects of VPA stimulation.

  9. Long non-coding RNA Malat1 promotes neurite outgrowth through activation of ERK/MAPK signalling pathway in N2a cells.

    PubMed

    Chen, Lei; Feng, Peimin; Zhu, Xi; He, Shixu; Duan, Jialan; Zhou, Dong

    2016-11-01

    Accumulating evidence suggests that long non-coding RNAs (lncRNAs) are playing critical roles in neurogenesis, yet the underlying molecular mechanisms remain largely elusive. Neurite outgrowth is an early step in neuronal differentiation and regeneration. Using in vitro differentiation of neuroblastoma-derived Neuro-2a (N2a) cell as a model, we performed expression profiling to identify lncRNAs putatively relevant for neurite outgrowth. We identified that Metastasis-associated lung adenocarcinoma transcript 1 (Malat1) was one of the most significantly up-regulated lncRNAs during N2a cell differentiation. Malat1 knockdown resulted in defects in neurite outgrowth as well as enhanced cell death. To pinpoint signalling pathways perturbed by Malat1 depletion, we then performed a reporter-based screening to examine the activities of 50 signalling pathways in Malat1 knockdown cells. We found that Malat1 knockdown resulted in conspicuous inhibition of Mitogen-Activated Protein Kinase (MAPK) signaling pathway as well as abnormal activation of Peroxisome proliferator-activated receptor (PPAR) and P53 signalling pathway. Inhibition of ERK/MAPK pathway with PD98059 potently blocked N2a cell neurite outgrowth, whereas phorbol 12-myristate 13-acetate-induced ERK activation rescued defects in neurite outgrowth and cell death induced by Malat1 depletion. Together, our results established a critical role of Malat1 in the early step of neuronal differentiation through activating ERK/MAPK signalling pathway.

  10. Permanent tensions in organization.

    PubMed

    Jansson, Noora

    2015-01-01

    The purpose of this paper is to investigate the relationship between permanent tensions and organizational change. This study used paradox theory and a case study. The case organization is a public university hospital in Finland involving several stakeholders. The analysis suggests that the relationship between permanent tensions and organizational change is a paradox that is part of organizational reality. As an organization learns to live with its permanent tensions, the renewal paradox settles into equilibrium. When tensions are provoked, the paradox is disturbed until it finds a new balance. This flexible nature of the paradox is the force that keeps the different stakeholders simultaneously empowered to maintain their unique missions and cohesive in order to benefit from the larger synergy. This research suggests that identification and evaluation of each permanent tension within an organization is important when executing organizational change. The fact that certain tensions are permanent and cannot be solved may have an influence on how planned change initiatives are executed. The results show that permanent tensions may be harnessed for the benefit of an organizational change. This research demonstrates originality by offering an alternative view of tensions, a view which emphasizes not only their permanent and plural nature but their importance for enabling the organization to change at its own, non-disruptive pace. The research also proposes a new concept, the "renewal paradox", to enhance understanding of the relationship between permanent tensions and organizational change.

  11. Berberine, a natural antidiabetes drug, attenuates glucose neurotoxicity and promotes Nrf2-related neurite outgrowth

    SciTech Connect

    Hsu, Ya-Yun; Tseng, Yu-Ting; Lo, Yi-Ching

    2013-11-01

    Reactive oxygen intermediates production and apoptotic damage induced by high glucose are major causes of neuronal damage in diabetic neuropathy. Berberine (BBR), a natural antidiabetes drug with PI3K-activating activity, holds promise for diabetes because of its dual antioxidant and anti-apoptotic activities. We have previously reported that BBR attenuated H{sub 2}O{sub 2} neurotoxicity via activating the PI3K/Akt/Nrf2-dependent pathway. In this study, we further explored the novel protective mechanism of BBR on high glucose-induced apoptotic death and neurite damage of SH-SY5Y cells. Results indicated BBR (0.1–10 nM) significantly attenuated reactive oxygen species (ROS) production, nucleus condensation, and apoptotic death in high glucose-treated cells. However, AG1024, an inhibitor of insulin growth factor-1 (IGF-1) receptor, significantly abolished BBR protection against high glucose-induced neuronal death. BBR also increased Bcl-2 expression and decreased cytochrome c release. High glucose down-regulated IGF-1 receptor and phosphorylation of Akt and GSK-3β, the effects of which were attenuated by BBR treatment. BBR also activated nuclear erythroid 2-related factor 2 (Nrf2), the key antioxidative transcription factor, which is accompanied with up-regulation of hemeoxygenase-1 (HO-1). Furthermore, BBR markedly enhanced nerve growth factor (NGF) expression and promoted neurite outgrowth in high glucose-treated cells. To further determine the role of the Nrf2 in BBR neuroprotection, RNA interference directed against Nrf2 was used. Results indicated Nrf2 siRNA abolished BBR-induced HO-1, NGF, neurite outgrowth and ROS decrease. In conclusion, BBR attenuated high glucose-induced neurotoxicity, and we are the first to reveal this novel mechanism of BBR as an Nrf2 activator against glucose neurotoxicity, providing another potential therapeutic use of BBR on the treatment of diabetic complications. - Highlights: • BBR attenuates high glucose-induced ROS

  12. Calcineurin-dependent cofilin activation and increased retrograde actin flow drive 5-HT-dependent neurite outgrowth in Aplysia bag cell neurons.

    PubMed

    Zhang, Xiao-Feng; Hyland, Callen; Van Goor, David; Forscher, Paul

    2012-12-01

    Neurite outgrowth in response to soluble growth factors often involves changes in intracellular Ca(2+); however, mechanistic roles for Ca(2+) in controlling the underlying dynamic cytoskeletal processes have remained enigmatic. Bag cell neurons exposed to serotonin (5-hydroxytryptamine [5-HT]) respond with a threefold increase in neurite outgrowth rates. Outgrowth depends on phospholipase C (PLC) → inositol trisphosphate → Ca(2+) → calcineurin signaling and is accompanied by increased rates of retrograde actin network flow in the growth cone P domain. Calcineurin inhibitors had no effect on Ca(2+) release or basal levels of retrograde actin flow; however, they completely suppressed 5-HT-dependent outgrowth and F-actin flow acceleration. 5-HT treatments were accompanied by calcineurin-dependent increases in cofilin activity in the growth cone P domain. 5-HT effects were mimicked by direct activation of PLC, suggesting that increased actin network treadmilling may be a widespread mechanism for promoting neurite outgrowth in response to neurotrophic factors.

  13. Fetal calf serum-mediated inhibition of neurite growth from ciliary ganglion neurons in vitro.

    PubMed

    Davis, G E; Skaper, S D; Manthorpe, M; Moonen, G; Varon, S

    1984-01-01

    Embryonic chick ciliary ganglion (CG) neurons cultured in fetal calf serum-containing medium have been previously reported to extend neurites on polyornithine (PORN) substrata precoated with a neurite-promoting factor (PNPF) from rat schwannoma-conditioned medium. On PORN substrata alone, however, no neuritic growth occurred. This was interpreted as evidence that PORN was an incompetent substratum for ciliary neuritic growth. In this study, we now find that an untreated PORN substratum allows neuritic growth in serum-free defined medium. When PNPF was added to PORN, a more rapid and extensive neuritic response occurred. After 5 hr of culture, a 60% neuritic response occurred on PNPF/PORN, whereas no neurons initiated neurites until 10-12 hr on PORN. The inhibitory effect of fetal calf serum noted above on PORN could be obtained in part by pretreating the substratum with serum for 1 hr. Maximal inhibitory effects in the PORN pretreatment were achieved after 30 min and were not further improved by treatments up to 4 hr. Bovine serum albumin was also found to inhibit neurite growth on PORN to about 60% of the inhibition obtained by an equivalent amount of serum protein. Fetal calf serum was shown to cause a 15% reduction in the percentage of neurons bearing neurites after its addition to 18-hr serum-free PORN cultures and to cause statistically significant reductions in neurite lengths measured 2 hr later.

  14. Induction of Neurite Outgrowth in PC12 Cells Treated with Temperature-Controlled Repeated Thermal Stimulation

    PubMed Central

    Kudo, Tada-aki; Kanetaka, Hiroyasu; Mochizuki, Kentaro; Tominami, Kanako; Nunome, Shoko; Abe, Genji; Kosukegawa, Hiroyuki; Abe, Toshihiko; Mori, Hitoshi; Mori, Kazumi; Takagi, Toshiyuki; Izumi, Shin-ichi

    2015-01-01

    To promote the functional restoration of the nervous system following injury, it is necessary to provide optimal extracellular signals that can induce neuronal regenerative activities, particularly neurite formation. This study aimed to examine the regulation of neuritogenesis by temperature-controlled repeated thermal stimulation (TRTS) in rat PC12 pheochromocytoma cells, which can be induced by neurotrophic factors to differentiate into neuron-like cells with elongated neurites. A heating plate was used to apply thermal stimulation, and the correlation of culture medium temperature with varying surface temperature of the heating plate was monitored. Plated PC12 cells were exposed to TRTS at two different temperatures via heating plate (preset surface temperature of the heating plate, 39.5°C or 42°C) in growth or differentiating medium for up to 18 h per day. We then measured the extent of growth, neuritogenesis, or acetylcholine esterase (AChE) activity (a neuronal marker). To analyze the mechanisms underlying the effects of TRTS on these cells, we examined changes in intracellular signaling using the following: tropomyosin-related kinase A inhibitor GW441756; p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580; and MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor U0126 with its inactive analog, U0124, as a control. While a TRTS of 39.5°C did not decrease the growth rate of cells in the cell growth assay, it did increase the number of neurite-bearing PC12 cells and AChE activity without the addition of other neuritogenesis inducers. Furthermore, U0126, and SB203580, but not U0124 and GW441756, considerably inhibited TRTS-induced neuritogenesis. These results suggest that TRTS can induce neuritogenesis and that participation of both the ERK1/2 and p38 MAPK signaling pathways is required for TRTS-dependent neuritogenesis in PC12 cells. Thus, TRTS may be an effective technique for regenerative neuromedicine. PMID:25879210

  15. Chroman-like cyclic prenylflavonoids promote neuronal differentiation and neurite outgrowth and are neuroprotective.

    PubMed

    Oberbauer, Eleni; Urmann, Corinna; Steffenhagen, Carolin; Bieler, Lara; Brunner, Doris; Furtner, Tanja; Humpel, Christian; Bäumer, Bastian; Bandtlow, Christine; Couillard-Despres, Sebastien; Rivera, Francisco J; Riepl, Herbert; Aigner, Ludwig

    2013-11-01

    Flavonoids target a variety of pathophysiological mechanisms and are therefore increasingly considered as compounds encompassed with therapeutic potentials in diseases such as cancer, diabetes, arteriosclerosis, and neurodegenerative diseases and mood disorders. Hops (Humulus lupulus L.) is rich in flavonoids such as the flavanone 8-prenylnaringenin, which is the most potent phytoestrogen identified so far, and the prenylchalcone xanthohumol, which has potent tumor-preventive, anti-inflammatory and antiviral activities. In the present study, we questioned whether hops-derived prenylflavonoids and synthetic derivatives thereof act on neuronal precursor cells and neuronal cell lines to induce neuronal differentiation, neurite outgrowth and neuroprotection. Therefore, mouse embryonic forebrain-derived neural precursors and Neuro2a neuroblastoma-derived cells were stimulated with the prenylflavonoids of interest, and their potential to activate the promoter of the neuronal fate-specific doublecortin gene and to stimulate neuronal differentiation and neurite outgrowth was analyzed. In this screening, we identified highly "neuroactive" compounds, which we termed "enhancement of neuronal differentiation factors" (ENDFs). The most potent molecule, ENDF1, was demonstrated to promote neuronal differentiation of neural stem cells and neurite outgrowth of cultured dorsal root ganglion neurons and protected neuronal PC12 cells from cobalt chloride-induced as well as cholinergic neurons of the nucleus basalis of Meynert from deafferentation-induced cell death. The results indicate that hops-derived prenylflavonoids such as ENDFs might be powerful molecules to promote neurogenesis, neuroregeneration and neuroprotection in cases of chronic neurodegenerative diseases, acute brain and spinal cord lesion and age-associated cognitive impairments.

  16. Study of laser uncaging induced morphological alteration of rat cortical neurites using atomic force microscopy.

    PubMed

    Tian, Jian; Tu, Chunlong; Liang, Yitao; Zhou, Jian; Ye, Xuesong

    2015-09-30

    Activity-dependent structural remodeling is an important aspect of neuronal plasticity. In the previous researches, neuronal structure variations resulting from external interventions were detected by the imaging instruments such as the fluorescence microscopy, the scanning/transmission electron microscopy (SEM/TEM) and the laser confocal microscopy. In this article, a new platform which combined the photochemical stimulation with atomic force microscopy (AFM) was set up to detect the activity-dependent structural remodeling. In the experiments, the cortical neurites on the glass coverslips were stimulated by locally uncaged glutamate under the ultraviolet (UV) laser pulses, and a calcium-related structural collapse of neurites (about 250 nm height decrease) was observed by an AFM. This was the first attempt to combine the laser uncaging with AFM in living cell researches. With the advantages of highly localized stimulation (<5 μm), super resolution imaging (<3.8 nm), and convenient platform building, this system was suitable for the quantitative observation of the neuron mechanical property variations and morphological alterations modified by neural activities under different photochemical stimulations, which would be helpful for studying physiological and pathological mechanisms of structural and functional changes induced by the biomolecule acting.

  17. Ionomycin-induced calcium influx induces neurite degeneration in mouse neuroblastoma cells: analysis of a time-lapse live cell imaging system.

    PubMed

    Nakamura, Saki; Nakanishi, Ayumi; Takazawa, Minami; Okihiro, Shunsuke; Urano, Shiro; Fukui, Koji

    2016-01-01

    Reactive oxygen species induce neuronal cell death. However, the detailed mechanisms of cell death have not yet been elucidated. Previously, we reported neurite degeneration before the induction of cell death. Here, we attempted to elucidate the mechanisms of neurite degeneration before the induction of cell death using the neuroblastoma N1E-115 cell line and a time-lapse live cell imaging system. Treatment with the calcium ionophore ionomycin induced cell death and neurite degeneration in a concentration- and time-dependent manner. Treatment with a low concentration of ionomycin immediately produced a significant calcium influx into the intracellular region in N1E-115 cells. After 1-h incubation with ionomycin, the fluorescence emission of MitoSOX(TM) increased significantly compared to the control. Finally, analysis using a new mitochondrial specific fluorescence dye, MitoPeDPP, indicated that treatment with ionomycin significantly increased the mitochondrial lipid hydroperoxide production in N1E-115 cells. The fluorescence emissions of Fluo-4 AM and MitoPeDPP were detected in the cell soma and neurite regions in ionomycin-treated N1E-115 cells. However, the emissions of neurites were much lower than those of the cell soma. TBARS values of ionomycin-treated cells significantly increased compared to the control. These results indicate that ionomycin induces calcium influx into the intracellular region and reactive oxygen species production in N1E-115 cells. Lipid hydroperoxide production was induced in ionomycin-treated N1E-115 cells. Calcium influx into the intracellular region is a possible activator of neurite degeneration.

  18. Introducing surface tension to spacetime

    NASA Astrophysics Data System (ADS)

    Perko, H. A.

    2017-05-01

    Concepts from physical chemistry of surfaces and surface tension are applied to spacetime. More specifically, spacetime is modeled as a spatial fluid continuum bound together by a multi-dimensional membrane of time. A metric tensor that relates empty flat spacetime to energetic curved spacetime is found. Equations of motion for an infinitesimal unit of spacetime are derived. The equation of motion in a time-like direction is a Klein-Gordon type equation. The equations of motion in space-like directions take the form of Schrodinger’s equation where Plank’s constant is related to membrane elastic modulus. Although much work remains, it is suggested that the spacetime surface tension may serve as a mechanical model for many phenomena in quantum mechanics and atomic particle physics.

  19. Perspectives on Campus Tensions.

    ERIC Educational Resources Information Center

    Nichols, David C., Ed.

    The purpose of this book was to provide background information and insight on campus tensions, and suggest ideas on how to go about reducing these tensions. The papers are divided into 5 parts. Part I, The New Situation, includes papers by Kenneth E. Boulding, William M. Birenbaum, Marcus G. Raskin, and Peter Schrag. Part II, Where the Students…

  20. Tension type headache

    PubMed Central

    Chowdhury, Debashish

    2012-01-01

    Tension type headaches are common in clinical practice. Earlier known by various names, the diagnosis has had psychological connotations. Recent evidence has helped clarify the neurobiological basis and the disorder is increasingly considered more in the preview of neurologists. The classification, clinical features, differential diagnosis and treatment of tension type headache are discussed in this paper. PMID:23024570

  1. [Tension-type headaches].

    PubMed

    Trkanjec, Zlatko; Aleksić-Shihabi, Anka

    2008-05-01

    Tension-type headache is one of the most common and most significant primary headaches. Tension-type headache is a very heterogeneous disorder. It can be divided into episodic and chronic tension-type headache. The pain is a dull, pressing, tightening, typically band-like sensation. The pain is of non-pulsating quality, the location is bilateral, and there is no nausea, vomiting, phonophobia or photophobia. There are no prodromal symptoms or aura. The pain is mild to moderate and it does not aggravate with routine physical activities. Some patients have increased tenderness of pericranial muscles. Psychological factors are common in tension-type headache. Nitric oxide has an important role in the pathophysiology of chronic tension-type headache. Probably it promotes central sensitization and therefore increases nociception. In differential diagnosis of tension type-headache, all structural and metabolic diseases causing headache have to be ruled out, as well as all other primary headaches. All comorbid and coexistent states should also be considered. In the treatment of tension-type headache, pharmacological and non-pharmacological methods are employed. Analgesics, myorelaxants, anxiolytics and antidepressants are most commonly used, as well as physical therapy, massage, acupuncture, behavioral therapy and psychotherapy. Recently, the applications of botulinum toxin and acupuncture have been described in the treatment and prophylaxis of tension-type headache.

  2. Perspectives on Campus Tensions.

    ERIC Educational Resources Information Center

    Nichols, David C., Ed.

    The purpose of this book was to provide background information and insight on campus tensions, and suggest ideas on how to go about reducing these tensions. The papers are divided into 5 parts. Part I, The New Situation, includes papers by Kenneth E. Boulding, William M. Birenbaum, Marcus G. Raskin, and Peter Schrag. Part II, Where the Students…

  3. Tensions in Distributed Leadership

    ERIC Educational Resources Information Center

    Ho, Jeanne; Ng, David

    2017-01-01

    Purpose: This article proposes the utility of using activity theory as an analytical lens to examine the theoretical construct of distributed leadership, specifically to illuminate tensions encountered by leaders and how they resolved these tensions. Research Method: The study adopted the naturalistic inquiry approach of a case study of an…

  4. P120-Catenin Protects Endplate Chondrocytes From Intermittent Cyclic Mechanical Tension Induced Degeneration by Inhibiting the Expression of RhoA/ROCK-1 Signaling Pathway.

    PubMed

    Xu, Hong-Guang; Ma, Ming-Ming; Zheng, Quan; Shen, Xiang; Wang, Hong; Zhang, Shu-Feng; Xu, Jia-Jia; Wang, Chuan-Dong; Zhang, Xiao-Ling

    2016-08-15

    The changes of endplate chondrocytes induced by intermittent cyclic mechanical tension (ICMT) were observed by realtime reverse transcription-polymerase chain reaction, immunofluorescence, and Western blot analysis. To investigate the role of RhoA/ROCK-1 signaling pathway and E-cadherin/P120-catenin complex in endplate chondrocytes degeneration induced by ICMT. ICMT can induce the endplate chondrocyte degeneration. However, the relationship between P120-catenin or RhoA/ROCK-1 signaling pathway and endplate chondrocytes degeneration induced by ICMT is not clear. ICMT (strain at 0.5 Hz sinusoidal curve at 8% elongation) was applied to rat endplate chondrocytes for 6 days, 16 hours a day. The cell viability and apoptosis were examined by the LIVE/DEAD assay and flow cytometry. Histological staining was used to examine the lumbar disc tissue morphology and extracellular matrix. To regulate RhoA/ROCK-1 signaling pathway and the expression of E-cadherin and P120-catenin, RhoA/ROCK-1 pathway-specific inhibitors, E-cadherin, and p120-catenin plasmid were applied. Coimmunoprecipitation was employed to examine the interaction between E-cadherin and P120-catenin, P120-catenin, and RhoA. The related gene expression and protein location was examined by realtime reverse transcription-polymerase chain reaction, Western blot, and immunofluorescence. There was no change of viability verified by LIVE/DEAD assay and flow cytometry after ICMT loading. ICMT loading led to RhoA/ROCK-1 signaling activation and the loss of the chondrogenic phenotype of endplate chondrocytes. Inhibition of RhoA/ROCK-1 signaling pathway significantly ameliorated the degeneration induced by ICMT. The expression of P120-catenin and E-cadherin were inhibited by ICMT. ICMT reduced the interaction between P120-catenin and E-cadherin. Furthermore, over-expression of P120-catenin and E-cadherin can suppress the expression of chondrogenic gene, over-expression of P120-catenin can suppress the RhoA/ROCK-1

  5. STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED ...

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

    STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED BY ARCHITECTURAL FINISH. TENSION RING ROLLER SUPPORT AT COLUMN OBSCURED BY COLUMN COVERINGS. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  6. Tension generation by threads of contractile proteins

    PubMed Central

    1977-01-01

    Threads of contractile proteins were formed via extrusion and their isometric tensions and isotonic contraction velocities were measured. We obtained reproducible data by using a new and sensitive tensiometer. The force-velocity curves of actomyosin threads were similar to those of muscle, with isometric tensions of the order of 10g/cm2 and maximum contraction velocites of the order of 10(-2) lengths/s. The data could be fitted by Hill's equation. Addition of tropomyosin and troponin to the threads increased isometric tension and maximum contraction velocity. Threads which contained troponin and tropomyosin required Ca++ for contraction and the dependence of their isometric tension on the level of free Ca++ was like that of muscle. The dependence of tension or of contraction velocity upon temperature or upon ionic strength is similar for actomyosin threads and muscle fibers. In contrast, the dependence of most parameters which are characteristic of the actomyosin interaction in solution (or suspension) upon these variables is not similar to the dependence of the muscle fiber parameters. The conclusion we have drawn from these results is that the mechanism of tension generation in the threads is similar to the mechanism that exists in muscle. Because the protein composition of the thread system can be manipulated readily and because the tensions and velocities of the threads can be related directly to the physiological parameters of muscle fibers, the threads provide a powerful method for studying contractile proteins. PMID:137958

  7. Automated quantification of neurite outgrowth orientation distributions on patterned surfaces

    NASA Astrophysics Data System (ADS)

    Payne, Matthew; Wang, Dadong; Sinclair, Catriona M.; Kapsa, Robert M. I.; Quigley, Anita F.; Wallace, Gordon G.; Razal, Joselito M.; Baughman, Ray H.; Münch, Gerald; Vallotton, Pascal

    2014-08-01

    Objective. We have developed an image analysis methodology for quantifying the anisotropy of neuronal projections on patterned substrates. Approach. Our method is based on the fitting of smoothing splines to the digital traces produced using a non-maximum suppression technique. This enables precise estimates of the local tangents uniformly along the neurite length, and leads to unbiased orientation distributions suitable for objectively assessing the anisotropy induced by tailored surfaces. Main results. In our application, we demonstrate that carbon nanotubes arrayed in parallel bundles over gold surfaces induce a considerable neurite anisotropy; a result which is relevant for regenerative medicine. Significance. Our pipeline is generally applicable to the study of fibrous materials on 2D surfaces and should also find applications in the study of DNA, microtubules, and other polymeric materials.

  8. Androgen regulation of axon growth and neurite extension in motoneurons

    PubMed Central

    Fargo, Keith N.; Galbiati, Mariarita; Foecking, Eileen M.; Poletti, Angelo; Jones, Kathryn J.

    2008-01-01

    Androgens act on the CNS to affect motor function through interaction with a widespread distribution of intracellular androgen receptors (AR). This review highlights our work on androgens and process outgrowth in motoneurons, both in vitro and in vivo. The actions of androgens on motoneurons involve the generation of novel neuronal interactions that are mediated by the induction of androgen-dependent neurite or axonal outgrowth. Here, we summarize the experimental evidence for the androgenic regulation of the extension and regeneration of motoneuron neurites in vitro using cultured immortalized motoneurons, and axons in vivo using the hamster facial nerve crush paradigm. We place particular emphasis on the relevance of these effects to SBMA and peripheral nerve injuries. PMID:18387610

  9. Rho kinase regulates neurite outgrowth of hippocampal neurons via calcium dependent cytoskeleton regulation

    PubMed Central

    Ji, Zhisheng; Cai, Zhenbin; Zhang, Jifeng; Liu, Nannuan; Chen, Jing; Tan, Minghui; Lin, Hongsheng; Guo, Guoqing

    2017-01-01

    Objective: To investigate whether calcium is involved in downstream signal transduction in neurite outgrowth regulated by Rho kinase. Methods: In vitro primary hippocampal neurons were cultured and treated with Rho kinase agonist (LPA) or antagonist (Y-27632). Then, the cytoskeleton and neurite outgrowth were observed. After addition of calcium antagonist BAPTA/AM to reduce intracellular calcium, the cytoskeleton distribution and neurite outgrowth were observed. Results: The activation or inhibition of Rho kinase could significantly alter the number and length of neurites of hippocampal neurons. Rho kinase regulated the cytoskeleton to regulate the neurite outgrowth, and LPA could significantly increase intracellular calcium. After BAPTA/AM treatment, the length and branch number of neurites of neurons reduced markedly. BAPTA/AM was able to reduce intracellular calcium and decrease neuronal cytoskeleton. Treatment with both BAPTA/AM and LPA could stop the retraction of neurites, but the length and branch number of neurites remained unchanged after treatment with Y-27632 and LPA. Conclusion: Calcium may affect the cytoskeleton arrangement to regulate neurite outgrowth, and calcium is involved in the downstream signal transduction of Rho kinase regulated neurite outgrowth of hippocampal neurons. PMID:28337305

  10. Large-scale analysis of neurite growth dynamics on micropatterned substrates†‡

    PubMed Central

    Wissner-Gross, Zachary D.; Scott, Mark A.; Ku, David; Ramaswamy, Priya

    2011-01-01

    During both development and regeneration of the nervous system, neurons display complex growth dynamics, and several neurites compete to become the neuron’s single axon. Numerous mathematical and biophysical models have been proposed to explain this competition, which remain experimentally unverified. Large-scale, precise, and repeatable measurements of neurite dynamics have been difficult to perform, since neurons have varying numbers of neurites, which themselves have complex morphologies. To overcome these challenges using a minimal number of primary neurons, we generated repeatable neuronal morphologies on a large scale using laser-patterned micron-wide stripes of adhesive proteins on an otherwise highly non-adherent substrate. By analyzing thousands of quantitative time-lapse measurements of highly reproducible neurite growth dynamics, we show that total neurite growth accelerates until neurons polarize, that immature neurites compete even at very short lengths, and that neuronal polarity exhibits a distinct transition as neurites grow. Proposed neurite growth models agree only partially with our experimental observations. We further show that simple yet specific modifications can significantly improve these models, but still do not fully predict the complex neurite growth behavior. Our high-content analysis puts significant and nontrivial constraints on possible mechanistic models of neurite growth and specification. The methodology presented here could also be employed in large-scale chemical and target-based screens on a variety of complex and subtle phenotypes for therapeutic discoveries using minimal numbers of primary neurons. PMID:20976322

  11. Studies of Schwann cell proliferation. III. Evidence for the surface localization of the neurite mitogen

    PubMed Central

    1980-01-01

    In the preceding paper (Salzer et al., 1980, J. Cell Biol. 84:753-- 766), evidence was presented that a neurite membrane fraction could be used to stimulate Schwann cell proliferation in culture. In this study, we present evidence that the mitogenic signal by which intact neurites or neurite membranes stimulate Schwann cell proliferation is located at the neurite surface. This conclusion is based on the following observations: (a) stimulation of Schwann cell proliferation by neurons requires direct contact between neurites and Schwann cells, separation of the two cells by a permeable collagen diaphragm 6 microns thick prevents Schwann cell proliferation; (b) treatment of intact neurites with trypsin before preparation of neurite membranes abolishes the ability of these membranes to be mitogenic for Schwann cells; and (c) the mitogenic activity of neurite homogenates is exclusively localized in the particulate rather than the soluble fraction of the homogenate. The mitogenic component on the neurite surface is heat labile, and is inactivated by aldehyde fixation. Preliminary data suggest that the mitogenic effect of neurite on Schwann cells is not mediated by 3',5'- cyclic AMP. PMID:6153659

  12. BIG1, a brefeldin A-inhibited guanine nucleotide-exchange protein regulates neurite development via PI3K-AKT and ERK signaling pathways.

    PubMed

    Zhou, C; Li, C; Li, D; Wang, Y; Shao, W; You, Y; Peng, J; Zhang, X; Lu, L; Shen, X

    2013-12-19

    The elongation of neuron is highly dependent on membrane trafficking. Brefeldin A (BFA)-inhibited guanine nucleotide-exchange protein 1 (BIG1) functions in the membrane trafficking between the Golgi apparatus and the plasma membrane. BFA, an uncompetitive inhibitor of BIG1 can inhibit neurite outgrowth and polarity development. In this study, we aimed to define the possible role of BIG1 in neurite development and to further investigate the potential mechanism. By immunostaining, we found that BIG1 was extensively colocalized with synaptophysin, a marker for synaptic vesicles in soma and partly in neurites. The amount of both protein and mRNA of BIG1 were up-regulated during rat brain development. BIG1 depletion significantly decreased the neurite length and inhibited the phosphorylation of phosphatidylinositide 3-kinase (PI3K) and protein kinase B (AKT). Inhibition of BIG1 guanine nucleotide-exchange factor (GEF) activity by BFA or overexpression of the dominant-negative BIG1 reduced PI3K and AKT phosphorylation, indicating regulatory effects of BIG1 on PI3K-AKT signaling pathway is dependent on its GEF activity. BIG1 siRNA or BFA treatment also significantly reduced extracellular signal-regulated kinase (ERK) phosphorylation. Overexpression of wild-type BIG1 significantly increased ERK phosphorylation, but the dominant-negative BIG1 had no effect on ERK phosphorylation, indicating the involvement of BIG1 in ERK signaling regulation may not be dependent on its GEF activity. Our result identified a novel function of BIG1 in neurite development. The newly recognized function integrates the function of BIG1 in membrane trafficking with the activation of PI3K-AKT and ERK signaling pathways which are critical in neurite development. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

  13. Neurite outgrowth in human iPSC-derived neurons

    EPA Pesticide Factsheets

    Data on morphology of rat and human neurons in cell cultureThis dataset is associated with the following publication:Druwe, I., T. Freudenrich , K. Wallace , T. Shafer , and W. Mundy. Comparison of Human Induced PluripotentStem Cell-Derived Neurons and Rat Primary CorticalNeurons as In Vitro Models of Neurite Outgrowth. Applied In vitro Toxicology. Mary Ann Liebert, Inc., Larchmont, NY, USA, 2(1): 26-36, (2016).

  14. Non-cytotoxic Concentration of Cisplatin Decreases Neuroplasticity-Related Proteins and Neurite Outgrowth Without Affecting the Expression of NGF in PC12 Cells.

    PubMed

    Ferreira, Rafaela Scalco; Dos Santos, Neife Aparecida Guinaim; Martins, Nádia Maria; Fernandes, Laís Silva; Dos Santos, Antonio Cardozo

    2016-11-01

    Cisplatin is the most effective and neurotoxic platinum chemotherapeutic agent. It induces a peripheral neuropathy characterized by distal axonal degeneration that might progress to degeneration of cell bodies and apoptosis. Most symptoms occur nearby distal axonal branches and axonal degeneration might induce peripheral neuropathy regardless neuronal apoptosis. The toxic mechanism of cisplatin has been mainly associated with DNA damage, but cisplatin might also affect neurite outgrowth. Nevertheless, the neurotoxic mechanism of cisplatin remains unclear. We investigated the early effects of cisplatin on axonal plasticity by using non-cytotoxic concentrations of cisplatin and PC12 cells as a model of neurite outgrowth and differentiation. PC12 cells express NGF-receptors (trkA) and respond to NGF by forming neurites, branches and synaptic vesicles. For comparison, we used a neuronal model (SH-SY5Y cells) that does not express trkA nor responds to NGF. Cisplatin did not change NGF expression in PC12 cells and decreased neurite outgrowth in both models, suggesting a NGF/trkA independent mechanism. It also reduced axonal growth (GAP-43) and synaptic (synapsin I and synaptophysin) proteins in PC12 cells, without inducing mitochondrial damage or apoptosis. Therefore, cisplatin might affect axonal plasticity before DNA damage, NGF/trkA down-regulation, mitochondrial damage or neuronal apoptosis. This is the first study to show that neuroplasticity-related proteins might be early targets of the neurotoxic action of cisplatin and their role on cisplatin-induced peripheral neuropathy should be investigated in vivo.

  15. Plexin B3 promotes neurite outgrowth, interacts homophilically, and interacts with Rin

    PubMed Central

    Hartwig, Christine; Veske, Andres; Krejcova, Sarka; Rosenberger, Georg; Finckh, Ulrich

    2005-01-01

    Background Plexins, known to date as receptors of semaphorins, are implicated in semaphorin-mediated axon repulsion and growth cone collapse. However, subtype-specific functions of the majority of the nine members of the mammalian plexin family are largely unknown. In order to investigate functional properties of B-plexins, we analyzed the expression of human and murine plexin B3 and expressed full-length human plexins B2 (B2) and B3 (B3) in NIH-3T3 cells. Results Unexpectedly, B3 strongly and B2 moderately stimulate neurite outgrowth of primary murine cerebellar neurons. Both plexins mediate Ca2+/Mg2+-dependent cell aggregation due to homophilic trans-interaction, which is strong in the case of B3 and moderate for B2. Using different deletion constructs we show that the sema domain of B3 is essential for homophilic interaction. Using yeast two-hybrid analysis, we identified the neuron-specific and calmodulin-binding Ras-related GTPase Rin as an interaction partner of the intracellular part of B3, but not of B2. Rin, also known for its neurite outgrowth-inducing characteristics, co-localizes and co-immunoprecipitates with B3 in co-transfected COS-7 cells. Conclusion Our data suggest an involvement of homophilic interaction of B3 in semaphorin-independent signaling mechanisms positively influencing neuronal morphogenesis or function. Furthermore the neuron-specific small GTPase Rin is involved in downstream signaling of plexin B3. PMID:16122393

  16. Managing tension headaches at home

    MedlinePlus

    Tension-type headache - self-care; Muscle contraction headache - self-care; Headache - benign - self-care; Headache - tension- self-care; Chronic headaches - tension - self-care; Rebound headaches - ...

  17. Neurite outgrowth on cultured spiral ganglion neurons induced by erythropoietin.

    PubMed

    Berkingali, Nurdanat; Warnecke, Athanasia; Gomes, Priya; Paasche, Gerrit; Tack, Jan; Lenarz, Thomas; Stöver, Timo

    2008-09-01

    The morphological correlate of deafness is the loss of hair cells with subsequent degeneration of spiral ganglion neurons (SGN). Neurotrophic factors have a neuroprotective effect, and especially brain-derived neurotrophic factor (BDNF) has been demonstrated to protect SGN in vitro and after ototoxic trauma in vivo. Erythropoietin (EPO) attenuates hair cell loss in rat cochlea explants that were treated with gentamycin. Recently, it has also been shown that EPO reduces the apoptose rate in hippocampal neurons. Therefore, the aim of the study was to examine the effects of EPO on SGN in vitro. Spiral ganglion cells were isolated from neonatal rats and cultured for 48 h in serum-free medium supplemented with EPO and/or BDNF. Results showed that survival rates of SGN were not significantly improved when cultivated with EPO alone. Also, EPO did not further increase BDNF-induced survival of SGN. However, significant elongation of neurites was determined when SGN were cultivated with EPO alone. Even though a less than additive effect was observed, combined treatment with BDNF and EPO led to a significant elongation of neurites when compared to individual treatment with BDNF or EPO. It can be concluded that EPO induces neurite outgrowth rather than promoting survival. Thus, EPO presents as an interesting candidate to enhance and modulate the regenerative effect of BDNF on SGN.

  18. Stimulation of neuronal neurite outgrowth using functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Matsumoto, K.; Sato, C.; Naka, Y.; Whitby, R.; Shimizu, N.

    2010-03-01

    Low concentrations (0.11-1.7 µg ml - 1) of functionalized carbon nanotubes (CNTs), which are multi-walled CNTs modified by amino groups, when added with nerve growth factor (NGF), promoted outgrowth of neuronal neurites in dorsal root ganglion (DRG) neurons and rat pheochromocytoma cell line PC12h cells in culture media. The quantity of active extracellular signal-regulated kinase (ERK) was higher after the addition of both 0.85 µg ml - 1 CNTs and NGF than that with NGF alone. CNTs increased the number of cells with neurite outgrowth in DRG neurons and PC12h cells after the inhibition of the ERK signaling pathway using a mitogen-activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor. Active ERK proteins were detected in MEK inhibitor-treated neurons after the addition of CNTs to the culture medium. These results demonstrate that CNTs may stimulate neurite outgrowth by activation of the ERK signaling pathway. Thus, CNTs are biocompatible and are promising candidates for biological applications and devices.

  19. Oriented Schwann cell monolayers for directed neurite outgrowth.

    PubMed

    Thompson, Deanna M; Buettner, Helen M

    2004-08-01

    Schwann cells are an important component of the peripheral nervous system and participate in peripheral nerve regeneration. They create a supportive environment for neurite outgrowth by releasing trophic factors and up-regulating permissive molecules on their surface. In addition, Schwann cells are able to self-organize into linear arrays in vitro and in vivo, suggesting a possible role in neurite guidance. Previously, we showed that Schwann cell placement and orientation in subconfluent cultures can be controlled using microlithographically patterned laminin substrates (Thompson, D. M., and H. M. Buettner. Tissue Eng. 7(3):247-266, 2001). In the current study, these substrates were used to create oriented Schwann cell monolayers. Both Schwann cell orientation and coverage were quantified in response to seeding density, culture medium, and micropattern dimensions. In serum-free medium, increasing the seeding density yielded a linear increase in coverage of the substrate area but decreased cell alignment. In an alternate approach, Schwann cells were first seeded in serum-free medium at moderate seeding density, allowed to align, then expanded in serum-containing growth medium. This produced complete coverage without large seeding densities while preserving alignment to the micropattern. Alignment and coverage were unaffected by micropattern dimensions. This work provides a useful methodology for investigating Schwann cell guidance effects on growing neurites.

  20. A miniature tension sensor to measure surgical suture tension of deformable musculoskeletal tissues during joint motion.

    PubMed

    Kiriyama, Yoshimori; Matsumoto, Hideo; Toyama, Yoshiaki; Nagura, Takeo

    2014-02-01

    The aim of this study was to develop a new suture tension sensor for musculoskeletal soft tissue that shows deformation or movements. The suture tension sensor was 10 mm in size, which was small enough to avoid conflicting with the adjacent sensor. Furthermore, the sensor had good linearity up to a tension of 50 N, which is equivalent to the breaking strength of a size 1 absorbable suture defined by the United States Pharmacopeia. The design and mechanism were analyzed using a finite element model prior to developing the actual sensor. Based on the analysis, adequate material was selected, and the output linearity was confirmed and compared with the simulated result. To evaluate practical application, the incision of the skin and capsule were sutured during simulated total knee arthroplasty. When conventional surgery and minimally invasive surgery were performed, suture tensions were compared. In minimally invasive surgery, the distal portion of the knee was dissected, and the proximal portion of the knee was dissected additionally in conventional surgery. In the skin suturing, the maximum tension was 4.4 N, and this tension was independent of the sensor location. In contrast, the sensor suturing the capsule in the distal portion had a tension of 4.4 N in minimally invasive surgery, while the proximal sensor had a tension of 44 N in conventional surgery. The suture tensions increased nonlinearly and were dependent on the knee flexion angle. Furthermore, the tension changes showed hysteresis. This miniature tension sensor may help establish the optimal suturing method with adequate tension to ensure wound healing and early recovery.

  1. The soma and neurites of primary afferent neurons in the guinea-pig intestine respond differentially to deformation

    PubMed Central

    Kunze, W A A; Clerc, N; Furness, J B; Gola, M

    2000-01-01

    Intrinsic primary afferent neurons in the small intestine are exposed to distortion of their processes and of their cell bodies. Recordings of mechanosensitivity have previously been made from these neurons using intracellular microelectrodes, but this form of recording has not permitted detection of generator potentials from the processes, or of responses to cell body distortion.We have developed a technique to record from enteric neurons in situ using patch electrodes. The mechanical stability of the patch recordings has allowed recording in cell-attached and whole cell configuration during imposed movement of the neurons.Pressing with a fine probe initiated generator potentials (14 ± 9 mV) from circumscribed regions of the neuron processes within the same myenteric ganglion, at distances from 100 to 500 μm from the cell body that was patched. Generator potentials persisted when synaptic transmission was blocked with high Mg2+, low Ca2+ solution.Soma distortion, by pressing down with the whole cell recording electrode, inhibited action potential firing. Consistent with this, moderate intra-electrode pressure (10 mbar; 1 kPa) increased the opening probability of large-conductance (BK) potassium channels, recorded in cell-attached mode, but suction was not effective. In outside-out patches, suction, but not pressure, increased channel opening probability. Mechanosensitive BK channels have not been identified on other neurons.The BK channels had conductances of 195 ± 25 pS. Open probability was increased by depolarization, with a half-maximum activation at a patch potential of 20 mV and a slope factor of 10 mV. Channel activity was blocked by charybdotoxin (20 nM).Stretch that increased membrane area under the electrode by 15 % was sufficient to double open probability. Similar changes in membrane area occur when the intestine changes diameter and wall tension under physiological conditions. Thus, the intestinal intrinsic primary afferent neurons are detectors of

  2. A Sonic hedgehog coreceptor, BOC regulates neuronal differentiation and neurite outgrowth via interaction with ABL and JNK activation.

    PubMed

    Vuong, Tuan Anh; Leem, Young-Eun; Kim, Bok-Geon; Cho, Hana; Lee, Sang-Jin; Bae, Gyu-Un; Kang, Jong-Sun

    2017-01-01

    Neurite outgrowth is a critical step for neurogenesis and remodeling synaptic circuitry during neuronal development and regeneration. An immunoglobulin superfamily member, BOC functions as Sonic hedgehog (Shh) coreceptor in canonical and noncanonical Shh signaling in neuronal development and axon outgrowth/guidance. However signaling mechanisms responsible for BOC action during these processes remain unknown. In our previous studies, a multiprotein complex containing BOC and a closely related protein CDO promotes myogenic differentiation through activation of multiple signaling pathways, including non-receptor tyrosine kinase ABL. Given that ABL and Jun. N-terminal kinase (JNK) are implicated in actin cytoskeletal dynamics required for neurogenesis, we investigated the relationship between BOC, ABL and JNK during neuronal differentiation. Here, we demonstrate that BOC and ABL are induced in P19 embryonal carcinoma (EC) cells and cortical neural progenitor cells (NPCs) during neuronal differentiation. BOC-depleted EC cells or Boc(-/-) NPCs exhibit impaired neuronal differentiation with shorter neurite formation. BOC interacts with ABL through its putative SH2 binding domain and seems to be phosphorylated in an ABL activity-dependent manner. Unlike wildtype BOC, ABL-binding defective BOC mutants exhibit impaired JNK activation and neuronal differentiation. Finally, Shh treatment enhances JNK activation which is diminished by BOC depletion. These data suggest that BOC interacts with ABL and activates JNK thereby promoting neuronal differentiation and neurite outgrowth. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Neurite outgrowth mediated by the heat shock protein Hsp90α: a novel target for the antipsychotic drug aripiprazole

    PubMed Central

    Ishima, T; Iyo, M; Hashimoto, K

    2012-01-01

    Aripiprazole is an atypical antipsychotic drug approved for the treatment of psychiatric disorders such as schizophrenia, bipolar disorder, major depressive disorder and autism. The drug shows partial agonistic activity at dopamine D2 receptors and 5-hydroxytryptamine (5-HT) 5-HT1A receptors, and antagonistic activity at 5-HT2A receptors. However, the precise mechanistic pathways remain unclear. In this study, we examined the effects of aripiprazole on neurite outgrowth. Aripiprazole significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration-dependent manner. The 5-HT1A receptor antagonist WAY-100635, but not the dopamine D2 receptor antagonist sulpiride, blocked the effects of aripiprazole, although, only partially. Specific inhibitors of inositol 1,4,5-triphosphate (IP3) receptors and BAPTA-AM, a chelator of intracellular Ca2+, blocked the effects of aripiprazole. Moreover, specific inhibitors of several common signaling pathways phospholipase C-γ (PLC-γ), phosphatidylinositol-3 kinase (PI3K), mammalian target of rapamycin, p38 MAPK, c-Jun N-terminal kinase, Akt, Ras, Raf, ERK, MAPK) also blocked the effects of aripiprazole. Using proteomic analysis, we found that aripiprazole significantly increased levels of the heat shock protein Hsp90α in cultured cells. The effects of aripiprazole on NGF-induced neurite outgrowth were significantly attenuated by treatment with Hsp90α RNA interference, but not by the negative control of Hsp90α. These findings suggest that both 5-HT1A receptor activation and Ca2+ signaling via IP3 receptors, as well as their downstream cellular signaling pathways play a role in the promotion of aripiprazole-induced neurite outgrowth. Furthermore, aripiprazole-induced increases in Hsp90α protein expression may form part of the therapeutic mechanism for this drug. PMID:23047241

  4. Antillatoxin, a novel lipopeptide, enhances neurite outgrowth in immature cerebrocortical neurons through activation of voltage-gated sodium channels.

    PubMed

    Jabba, S V; Prakash, A; Dravid, S M; Gerwick, W H; Murray, T F

    2010-03-01

    Antillatoxin (ATX) is a structurally novel lipopeptide that activates voltage-gated sodium channels (VGSC) leading to sodium influx in cerebellar granule neurons and cerebrocortical neurons 8 to 9 days in vitro (Li et al., 2001; Cao et al., 2008). However, the precise recognition site for ATX on the VGSC remains to be defined. Inasmuch as elevation of intracellular sodium ([Na(+)](i)) may increase N-methyl-d-aspartate receptor (NMDAR)-mediated Ca(2+) influx, Na(+) may function as a signaling molecule. We hypothesized that ATX may enhance neurite outgrowth in cerebrocortical neurons by elevating [Na(+)](i) and augmenting NMDAR function. ATX (30-100 nM) robustly stimulated neurite outgrowth, and this enhancement was sensitive to the VGSC antagonist, tetrodotoxin. To unambiguously demonstrate the enhancement of NMDA receptor function by ATX, we recorded single-channel currents from cell-attached patches. ATX was found to increase the open probability of NMDA receptors. Na(+)-dependent up-regulation of NMDAR function has been shown to be regulated by Src family kinase (SFK) (Yu and Salter, 1998). The Src kinase inhibitor PP2 abrogated ATX-enhanced neurite outgrowth, suggesting a SFK involvement in this response. ATX-enhanced neurite outgrowth was also inhibited by the NMDAR antagonist, (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801), and the calmodulin-dependent kinase kinase (CaMKK) inhibitor, 1,8-naphthoylene benzimidazole-3-carboxylic acid (STO-609), demonstrating the requirement for NMDAR activation with subsequent downstream engagement of the Ca(2+)-dependent CaMKK pathway. These results with the structurally and mechanistically novel natural product, ATX, confirm and generalize our earlier results with a neurotoxin site 5 ligand. These data suggest that VGSC activators may represent a novel pharmacological strategy to regulate neuronal plasticity through NMDAR-dependent mechanisms.

  5. The influence of magnetic fields exposure on neurite outgrowth in PC12 rat pheochromocytoma cells

    NASA Astrophysics Data System (ADS)

    Fan, W.; Ding, J.; Duan, W.; Zhu, Y. M.

    2004-11-01

    The aim of present work was to investigate the influence of magnetic fields exposure on neurite outgrowth in PC12 cells. The neurite number per cell, length of neurites and directions of neurite growth with respect to the direction of the magnetic field were analyzed after exposure to 50 Hz electromagnetic field for 96 h. A promotion was observed under a weak field (0.23 mT), as the average number of neurites per cell increased to 2.38±0.06 compared to 1.91±0.07 neurites/cell of the control dishes, while inhibition and directional outgrowth was evident under a relatively stronger field (1.32 mT). Our work shows that biological systems can be very sensitive to the strength of electromagnetic field.

  6. Na+/Ca2+ exchanger inhibitors inhibit neurite outgrowth in PC12 cells.

    PubMed

    Oda, Toru; Kume, Toshiaki; Izumi, Yasuhiko; Ishihara, Kumatoshi; Sugmimoto, Hachiro; Akaike, Akinori

    2011-01-01

    To elucidate the role of Na(+)/Ca(2+) exchanger (NCX) in neurite outgrowth, we investigated the effects of NCX inhibitors on neurite outgrowth in PC12 cells. KB-R7943 and 3',4'-dichlorobenzamil, NCX inhibitors, inhibited the neurite outgrowth caused by nerve growth factor (NGF). NCX inhibitors inhibited the neurite outgrowth caused by dibutylyl cAMP, which rapidly reorganizes the cytoskeleton. KB-R7943 inhibited the neurite outgrowth caused by Y-27632, an inhibitor of Rho kinase (ROCK) that regulates actin. However, NCX inhibitors did not inhibit NGF-induced phosphorylation of extracellular signal-regulated kinase. These results suggest that NCX inhibitor affects downstream of the Rho-ROCK signal transduction pathways in neurite outgrowth.

  7. DNA Spools under Tension

    NASA Astrophysics Data System (ADS)

    Kulić, I. M.; Schiessel, H.

    2004-06-01

    DNA spools, structures in which DNA is wrapped and helically coiled onto itself or onto a protein core, are ubiquitous in nature. We develop a general theory describing the nonequilibrium behavior of DNA spools under linear tension. Two puzzling and seemingly unrelated recent experimental findings, the sudden quantized unwrapping of nucleosomes and that of DNA toroidal condensates under tension, are theoretically explained and shown to be of the same origin. The study provides new insights into nucleosome and chromatin fiber stability and dynamics.

  8. Neurites from PC12 cells are connected to each other by synapse-like structures.

    PubMed

    Jeon, Chan-Young; Jin, Jae-Kwang; Koh, Young-Ho; Chun, Wook; Choi, Ihn-Geun; Kown, Hyung-Joo; Kim, Yong-Sun; Park, Jae-Bong

    2010-10-01

    PC12 cells have been used as a model of sympathetic neurons. Nerve growth factor (NGF), basic fibroblast growth factor (bFGF), and cAMP induce neurite outgrowth from PC12 cells. cAMP induced a greater number of neurites than did NGF. In particular, we attempted to elucidate whether PC12 cell neurites, induced by several factors including NGF, bFGF, and cAMP, form synapses, and whether each neurite has presynaptic and postsynaptic properties. Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we observed that neurites are connected to each other. The connected regions presented dense core vesicles and a clathrin-coated membrane invagination. In addition, typical maker proteins for axon and dendrite were identified by an immuno-staining method. Tau-1, an axonal marker in neurons, was localized at a high concentration in the terminal tips of neurites from PC12 cells, which were connected to neurite processes containing MAP-2, a dendritic marker in neurons. Furthermore, neurites containing SV2 and synaptotagmin, markers of synaptic vesicles, were in contact with neurites harboring drebrin, a marker of the postsynaptic membrane, suggesting that neurites from PC12 cells induced by NGF, bFGF, and cAMP may form synapse-like structures. Tat-C3 toxin, a Rho inhibitor, augmented neurite outgrowth induced by NGF, bFGF, and cAMP. Tat-C3 toxin together with neurotrophins also exhibited synapse-like structures between neurites. However, it remains to be studied whether RhoA inhibition plays a role in the formation of synapse-like structures in PC12 cells. (c) 2010 Wiley-Liss, Inc.

  9. Film tension of liquid nano-film from molecular modeling

    NASA Astrophysics Data System (ADS)

    Peng, Tiefeng; Yang, Siyuan; Xiang, Fan; Liang, Yunpei; Li, Qibin; Gao, Xuechao; Liu, Sanjun

    2017-02-01

    Due to its geometry simplicity, the forces of thin liquid film are widely investigated and equivalently employed to explore the phys-chemical properties and mechanical stability of many other surfaces or colloid ensembles. The surface tension of bulk liquid (σ∞) and film tension (γ) are the most important parameters. Considering the insufficiency of detailed interpretation of film tension under micro-scale circumstances, a method for film tension was proposed based on numerical modeling. Assuming surface tension at different slab thicknesses being identical to the surface tension of film, the surface tension and disjoining pressure were subsequently used to evaluate the film tension based on the derivation of film thermodynamics, and a decreasing tendency was discovered for low temperature regions. The influence of saline concentration on nano-films was also investigated, and the comparison of film tensions suggested that higher concentration yielded larger film tension, with stronger decreasing intensity as a function of film thickness. Meanwhile, at thick film range (15-20 nm), film tension of higher concentration film continued to decrease as thickness increase, however it arrived to constant value for that of lower concentration. Finally, it was found that the film tension was almost independent on the film curvature, but varied with the thickness. The approach is applicable to symmetric emulsion films containing surfactants and bi-layer lipid films.

  10. Micropatterned Methacrylate Polymers Direct Spiral Ganglion Neurite and Schwann Cell Growth

    PubMed Central

    Clarke, Joseph C.; Tuft, Bradley W.; Clinger, John D.; Levine, Rachel; Figueroa, Lucas Sievens; Guymon, C. Allan; Hansen, Marlan R.

    2011-01-01

    Significant advances in the functional outcomes achieved with cochlear implantation will likely require tissue-engineering approaches to improve the neural prosthesis interface. One strategy is to direct spiral ganglion neuron (SGN) axon growth in a highly organized fashion to approximate or contact stimulating electrodes. Here we assessed the ability of micropatterns induced by photopolymerization in methacrylate (MA) polymer systems to direct cultured neonatal rat SGN neurite growth and alignment of SG Schwann cells (SGSCs). SGN survival and neurite length were comparable among various polymer compositions. Remarkably, there was no significant difference in SGN survival or neurite length between laminin and non-laminin coated MA polymer substrates, suggesting high biocompatibility with SG tissue. Micropatterning with photopolymerization generated microchannels with a ridge periodicity of 50 µm and channel depths of 0.6–1.0 µm. SGN neurites grew within the grooves of the microchannels. These topographies strongly induced alignment of dissociated SGN neurites and SGSCs to parallel the pattern. By contrast, fibroblasts failed to align with the micropattern suggesting cell specific responses to topographical cues. SGN neurites extending from explants turned to parallel the pattern as they encountered the microchannels. The extent of turning was significantly correlated with angle at which the neurite initially encountered the pattern. These results indicate that SGN neurites respond to microtopographical features and that these features can be used to direct neurite growth in a highly organized fashion. PMID:21616131

  11. IPP5 inhibits neurite growth in primary sensory neurons by maintaining TGF-β/Smad signaling.

    PubMed

    Han, Qing-Jian; Gao, Nan-Nan; Guo-QiangMa; Zhang, Zhen-Ning; Yu, Wen-Hui; Pan, Jing; Wang, Qiong; Zhang, Xu; Bao, Lan

    2013-01-15

    During nerve regeneration, neurite growth is regulated by both intrinsic molecules and extracellular factors. Here, we found that inhibitor 5 of protein phosphatase 1 (IPP5), a newly identified inhibitory subunit of protein phosphatase 1 (PP1), inhibited neurite growth in primary sensory neurons as an intrinsic regulator. IPP5 was highly expressed in the primary sensory neurons of rat dorsal root ganglion (DRG) and was downregulated after sciatic nerve axotomy. Knocking down IPP5 with specific shRNA increased the length of the longest neurite, the total neurite length and the number of neurite ends in cultured rat DRG neurons. Mutation of the PP1-docking motif K(8)IQF(11) or the PP1-inhibiting motif at Thr(34) eliminated the IPP5-induced inhibition of neurite growth. Furthermore, biochemical experiments showed that IPP5 interacted with type I transforming growth factor-β receptor (TβRI) and PP1 and enhanced transforming growth factor-β (TGF-β)/Smad signaling in a PP1-dependent manner. Overexpressing IPP5 in DRG neurons aggravated TGF-β-induced inhibition of neurite growth, which was abolished by blocking PP1 or IPP5 binding to PP1. Blockage of TGF-β signaling with the TβRI inhibitor SB431542 or Smad2 shRNA attenuated the IPP5-induced inhibition of neurite growth. Thus, these data indicate that selectively expressed IPP5 inhibits neurite growth by maintaining TGF-β signaling in primary sensory neurons.

  12. Toward a general psychological model of tension and suspense

    PubMed Central

    Lehne, Moritz; Koelsch, Stefan

    2015-01-01

    Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena. PMID:25717309

  13. The effect of vesicle shape, line tension, and lateral tension on membrane-binding proteins

    NASA Astrophysics Data System (ADS)

    Hutchison, Jaime B.

    Model membranes allow for the exploration of complex biological phenomena with simple, controllable components. In this thesis we employ model membranes to determine the effect of vesicle properties such as line tension, lateral tension, and shape on membrane-binding proteins. We find that line tension at the boundary between domains in a phase separated vesicle can accumulate model membrane-binding proteins (green fluorescent protein with a histidine tag), and that those proteins can, in turn, alter vesicle shape. These results suggest that domains in biological membranes may enhance the local concentration of membrane-bound proteins and thus alter protein function. We also explore how membrane mechanical and chemical properties alter the function of the N-BAR domain of amphiphysin, a membrane-binding protein implicated in endocytosis. We find that negatively charged lipids are necessary for N-BAR binding to membranes at detectable levels, and that, at least for some lipid species, binding may be cooperative. Measurements of N-BAR binding as a function of vesicle tension reveal that modest membrane tension of around 2 mN/m, corresponding to a strain of around 1%, strongly increases N-BAR binding. We attribute this increase in binding with tension to the insertion of N-BAR's N-terminal amphipathic helix into the membrane which increases the membrane area. We propose that N-BAR, which was previously described as being able to sense membrane curvature, may be sensing strain instead. Measurements of membrane deformation by N-BAR as a function of membrane tension reveal that tension can hinder membrane deformation. Thus, tension may favor N-BAR binding yet suppress membrane deformation/tubulation, which requires work against tension. These results suggest that membrane tension, a parameter that is often not controlled in model membranes but is tightly controlled in biological cells, may be important in regulating protein binding and assembly and, hence, protein

  14. Managing the right tension.

    PubMed

    Dodd, Dominic; Favaro, Ken

    2006-12-01

    Of all the competing objectives every company faces, three pairs stand out: profitability versus growth, the short term versus the long term, and the whole organization versus the units. In each case, progress on one front usually comes at the expense of progress on the other. The authors researched the performance of more than 1000 companies worldwide over the past two decades and found that most struggle to succeed across the three tensions. From 1983 to 2003, for example, only 32% of these companies more often than not achieved positive profitability and revenue growth at the same time. The problem, the authors discovered, is not so much that managers don't recognize the tensions--those are all too familiar to anyone who has ever run a business. Rather, it is that managers frequently don't focus on the tension that matters most to their company. Even when they do identify the right tension, they usually make the mistake of prioritizing a "lead" objective within it-for example, profitability over growth. As a result, companies often end up moving first in this direction, then in that, and then back again, never quite resolving the tension. The companies that performed best adopted a very different approach. Instead of setting a lead objective, they looked at how best to strengthen what the two sides of each tension have in common: For profitability and growth,the common bond is customer benefit; for the short term and the long, it is sustainable earnings; and for the whole and its parts, it is particular organizational resources and capabilities. The authors describe how companies can select the right tension, what traps they may fall into when they focus on one side over the other, and how to escape these traps by managing to the bonds between objectives.

  15. Human Umbilical Tissue-Derived Cells Promote Synapse Formation and Neurite Outgrowth via Thrombospondin Family Proteins

    PubMed Central

    Koh, Sehwon; Kim, Namsoo; Yin, Henry H.; Harris, Ian R.; Dejneka, Nadine S.

    2015-01-01

    Cell therapy demonstrates great potential for the treatment of neurological disorders. Human umbilical tissue-derived cells (hUTCs) were previously shown to have protective and regenerative effects in animal models of stroke and retinal degeneration, but the underlying therapeutic mechanisms are unknown. Because synaptic dysfunction, synapse loss, degeneration of neuronal processes, and neuronal death are hallmarks of neurological diseases and retinal degenerations, we tested whether hUTCs contribute to tissue repair and regeneration by stimulating synapse formation, neurite outgrowth, and neuronal survival. To do so, we used a purified rat retinal ganglion cell culture system and found that hUTCs secrete factors that strongly promote excitatory synaptic connectivity and enhance neuronal survival. Additionally, we demonstrated that hUTCs support neurite outgrowth under normal culture conditions and in the presence of the growth-inhibitory proteins chondroitin sulfate proteoglycan, myelin basic protein, or Nogo-A (reticulon 4). Furthermore, through biochemical fractionation and pharmacology, we identified the major hUTC-secreted synaptogenic factors as the thrombospondin family proteins (TSPs), TSP1, TSP2, and TSP4. Silencing TSP expression in hUTCs, using small RNA interference, eliminated both the synaptogenic function of these cells and their ability to promote neurite outgrowth. However, the majority of the prosurvival functions of hUTC-conditioned media was spared after TSP knockdown, indicating that hUTCs secrete additional neurotrophic factors. Together, our findings demonstrate that hUTCs affect multiple aspects of neuronal health and connectivity through secreted factors, and each of these paracrine effects may individually contribute to the therapeutic function of these cells. SIGNIFICANCE STATEMENT Human umbilical tissue-derived cells (hUTC) are currently under clinical investigation for the treatment of geographic atrophy secondary to age-related macular

  16. Surface Tension Microscopy

    NASA Astrophysics Data System (ADS)

    Neumann, Burkhard; Engel, Horst; Schleifenbaum, Bernd

    1989-12-01

    A new microscopic technique will be presented for imaging surface topography and the locally varying surface tension of the object. With this technique it is possible to image the locally varying chemical composition of the specimen surface on a microscopic scale because the surface tension depends on the chemical composition. The imaging technique can be described as follows: By a simple preparation technique a thin (thickness several microns) liquid layer (e.g. immersion oil), is placed on the surface of the specimen. The resulting surface tension forces the boundary of the liquid layer to move. As the surface tension is a function of the location the boundary is modulated according to the magnitude of the surface tension at each place. Thus registering the shape of the moving boundary of the liquid layer at equidistant time intervals yields information on the specimen surface. The shape of the moving boundary is detected by a light microscope with differential interference contrast in combination with an image analysis system suited for real-time processing of image sequences in a threshold detection mode.

  17. Blood Vessel Tension Tester

    NASA Technical Reports Server (NTRS)

    1978-01-01

    In the photo, a medical researcher is using a specially designed laboratory apparatus for measuring blood vessel tension. It was designed by Langley Research Center as a service to researchers of Norfolk General Hospital and Eastern Virginia Medical School, Norfolk, Virginia. The investigators are studying how vascular smooth muscle-muscle in the walls of blood vessels-reacts to various stimulants, such as coffee, tea, alcohol or drugs. They sought help from Langley Research Center in devising a method of measuring the tension in blood vessel segments subjected to various stimuli. The task was complicated by the extremely small size of the specimens to be tested, blood vessel "loops" resembling small rubber bands, some only half a millimeter in diameter. Langley's Instrumentation Development Section responded with a miniaturized system whose key components are a "micropositioner" for stretching a length of blood vessel and a strain gage for measuring the smooth muscle tension developed. The micropositioner is a two-pronged holder. The loop of Mood vessel is hooked over the prongs and it is stretched by increasing the distance between the prongs in minute increments, fractions of a millimeter. At each increase, the tension developed is carefully measured. In some experiments, the holder and specimen are lowered into the test tubes shown, which contain a saline solution simulating body fluid; the effect of the compound on developed tension is then measured. The device has functioned well and the investigators say it has saved several months research time.

  18. Stimulation of neurite outgrowth using an electrically conducting polymer

    PubMed Central

    Schmidt, Christine E.; Shastri, Venkatram R.; Vacanti, Joseph P.; Langer, Robert

    1997-01-01

    Damage to peripheral nerves often cannot be repaired by the juxtaposition of the severed nerve ends. Surgeons have typically used autologous nerve grafts, which have several drawbacks including the need for multiple surgical procedures and loss of function at the donor site. As an alternative, the use of nerve guidance channels to bridge the gap between severed nerve ends is being explored. In this paper, the electrically conductive polymer—oxidized polypyrrole (PP)—has been evaluated for use as a substrate to enhance nerve cell interactions in culture as a first step toward potentially using such polymers to stimulate in vivo nerve regeneration. Image analysis demonstrates that PC-12 cells and primary chicken sciatic nerve explants attached and extended neurites equally well on both PP films and tissue culture polystyrene in the absence of electrical stimulation. In contrast, PC-12 cells interacted poorly with indium tin oxide (ITO), poly(l-lactic acid) (PLA), and poly(lactic acid-co-glycolic acid) surfaces. However, PC-12 cells cultured on PP films and subjected to an electrical stimulus through the film showed a significant increase in neurite lengths compared with ones that were not subjected to electrical stimulation through the film and tissue culture polystyrene controls. The median neurite length for PC-12 cells grown on PP and subjected to an electrical stimulus was 18.14 μm (n = 5643) compared with 9.5 μm (n = 4440) for controls. Furthermore, animal implantation studies reveal that PP invokes little adverse tissue response compared with poly(lactic acid-co-glycolic acid). PMID:9256415

  19. Stimulation of Neurite Outgrowth Using an Electrically Conducting Polymer

    NASA Astrophysics Data System (ADS)

    Schmidt, Christine E.; Shastri, Venkatram R.; Vacanti, Joseph P.; Langer, Robert

    1997-08-01

    Damage to peripheral nerves often cannot be repaired by the juxtaposition of the severed nerve ends. Surgeons have typically used autologous nerve grafts, which have several drawbacks including the need for multiple surgical procedures and loss of function at the donor site. As an alternative, the use of nerve guidance channels to bridge the gap between severed nerve ends is being explored. In this paper, the electrically conductive polymer--oxidized polypyrrole (PP)--has been evaluated for use as a substrate to enhance nerve cell interactions in culture as a first step toward potentially using such polymers to stimulate in vivo nerve regeneration. Image analysis demonstrates that PC-12 cells and primary chicken sciatic nerve explants attached and extended neurites equally well on both PP films and tissue culture polystyrene in the absence of electrical stimulation. In contrast, PC-12 cells interacted poorly with indium tin oxide (ITO), poly(L-lactic acid) (PLA), and poly(lactic acid-coglycolic acid) surfaces. However, PC-12 cells cultured on PP films and subjected to an electrical stimulus through the film showed a significant increase in neurite lengths compared with ones that were not subjected to electrical stimulation through the film and tissue culture polystyrene controls. The median neurite length for PC-12 cells grown on PP and subjected to an electrical stimulus was 18.14 μ m (n = 5643) compared with 9.5 μ m (n = 4440) for controls. Furthermore, animal implantation studies reveal that PP invokes little adverse tissue response compared with poly(lactic acid-coglycolic acid).

  20. Minocycline Promotes Neurite Outgrowth of PC12 Cells Exposed to Oxygen-Glucose Deprivation and Reoxygenation Through Regulation of MLCP/MLC Signaling Pathways.

    PubMed

    Tao, Tao; Feng, Jin-Zhou; Xu, Guang-Hui; Fu, Jie; Li, Xiao-Gang; Qin, Xin-Yue

    2017-04-01

    Minocycline, a semi-synthetic second-generation derivative of tetracycline, has been reported to exert neuroprotective effects both in animal models and in clinic trials of neurological diseases. In the present study, we first investigated the protective effects of minocycline on oxygen-glucose deprivation and reoxygenation-induced impairment of neurite outgrowth and its potential mechanism in the neuronal cell line, PC12 cells. We found that minocycline significantly increased cell viability, promoted neurite outgrowth and enhanced the expression of growth-associated protein-43 (GAP-43) in PC12 cells exposed to oxygen-glucose deprivation/reoxygenation injury. In addition, immunoblots revealed that minocycline reversed the overexpression of phosphorylated myosin light chain (MLC) and the suppression of activated extracellular signal-regulated kinase 1/2 (ERK1/2) caused by oxygen-glucose deprivation/reoxygenation injury. Moreover, the minocycline-induced neurite outgrowth was significantly blocked by Calyculin A (1 nM), an inhibitor of myosin light chain phosphatase (MLCP), but not by an ERK1/2 inhibitor (U0126; 10 μM). These findings suggested that minocycline activated the MLCP/MLC signaling pathway in PC12 cells after oxygen-glucose deprivation/reoxygenation injury, which resulted in the promotion of neurite outgrowth.

  1. The adhesion molecule KAL-1/anosmin-1 regulates neurite branching through a SAX-7/L1CAM–EGL-15/FGFR receptor complex

    PubMed Central

    Díaz-Balzac, Carlos A.; Lázaro-Peña, María I.; Ramos-Ortiz, Gibram A.; Bülow, Hannes E.

    2015-01-01

    Summary Neurite branching is essential for correct assembly of neural circuits, yet remains a poorly understood process. For example, the neural cell adhesion molecule KAL-1/anosmin-1, which is mutated in Kallmann Syndrome regulates neurite branching through mechanisms largely unknown. Here we show that KAL-1/anosmin-1 mediates neurite branching as an autocrine co-factor with EGL-17/FGF through a receptor complex consisting of the conserved cell adhesion molecule SAX-7/L1CAM and the fibroblast growth factor receptor EGL-15/FGFR. This protein complex, which appears conserved in humans, requires the immunoglobulin (Ig) domains of SAX-7/L1CAM and the FN(III) domains of KAL-1/anosmin-1 for formation in vitro as well as function in vivo. The kinase domain of the EGL-15/FGFR is required for branching, and genetic evidence suggests that ras-mediated signaling downstream of EGL-15/FGFR is necessary to effect branching. Our studies establish a molecular pathway that regulates neurite branching during development of the nervous system. PMID:26004184

  2. Impaired neurogenesis and neurite outgrowth in an HIV-gp120 transgenic model is reversed by exercise via BDNF production and Cdk5 regulation

    PubMed Central

    Lee, Myoung-Hwa; Amin, Niranjana D.; Venkatesan, Arun; Wang, Tongguang; Tyagi, Richa; Pant, Harish C.; Nath, Avindra

    2013-01-01

    Human immunodeficiency virus (HIV) infection associated neurocognitive disorders (HAND) is accompanied with brain atrophy. In these patients, impairment of adult neurogenesis and neurite outgrowth in the hippocampus may contribute to the cognitive dysfunction. Although running exercises can enhance neurogenesis and normalize neurite outgrowth, the underlying molecular mechanisms are not well understood. The HIV envelope protein, gp120, has been shown to impair neurogenesis. Using a gp120 transgenic mouse model, we demonstrate that exercise stimulated neural progenitor cell (NPC) proliferation in the hippocampal dentate gyrus and increased the survival rate and generation of newborn cells. However sustained exercise activity was necessary since the effects were reversed by detraining. Exercise also normalized dendritic outgrowth of neurons. Furthermore, it also increased the expression of hippocampal brainderived neurotrophic factor (BDNF) and normalized hyperactivation of cyclin-dependent kinase 5 (Cdk5). Hyper-activated Cdk5 or gp120 treatment led to aberrant neurite outgrowth and BDNF treatment normalized the neurite outgrowth in NPC cultures. These results suggest that sustained exercise has trophic activity on the neuronal lineage which is mediated by Cdk5 modulation of the BDNF pathway. PMID:23982957

  3. Valproic Acid Modifies Synaptic Structure and Accelerates Neurite Outgrowth Via the Glycogen Synthase Kinase-3β Signaling Pathway in an Alzheimer's Disease Model.

    PubMed

    Long, Zhi-Min; Zhao, Lei; Jiang, Rong; Wang, Ke-Jian; Luo, Shi-Fang; Zheng, Min; Li, Xiao-Feng; He, Gui-Qiong

    2015-11-01

    Tau hyperphosphorylation and amyloid β-peptide overproduction, caused by altered localization or abnormal activation of glycogen synthase kinase-3β (GSK-3β), is a pathogenic mechanism in Alzheimer's disease (AD). Valproic acid (VPA) attenuates senile plaques and neuronal loss. Here, we confirmed that VPA treatment improved spatial memory in amyloid precursor protein (APP)/presenilin 1 (PS 1) double-transgenic mice and investigated the effect of VPA on synaptic structure and neurite outgrowth. We used ultrastructural analysis, immunocytochemistry, immunofluorescence staining, and Western blot analysis to assess the effect of VPA treatment in mice. VPA treatment thickened the postsynaptic density, increased the number of presynaptic vesicles, and upregulated the expression of synaptic markers PSD-95 and GAP43. VPA increased neurite length of hippocampal neurons in vivo and in vitro. In VPA-treated AD mouse brain, inactivated GSK-3β (pSer9-GSK-3β) was markedly increased, while hyperphosphorylation of tau at Ser396 and Ser262 was decreased; total tau levels remained similar. VPA treatment notably improved pSer133-cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) levels, which are associated with synaptic function and neurite outgrowth. VPA improves behavioral deficits in AD, modifies synaptic structure, and accelerates neurite outgrowth, by inhibiting the activity of GSK-3β, decreasing hyperphosphorylated tau, enhancing CREB and BDNF expression. © 2015 John Wiley & Sons Ltd.

  4. Potentiation of Nerve Growth Factor-Induced Neurite Outgrowth by Fluvoxamine: Role of Sigma-1 Receptors, IP3 Receptors and Cellular Signaling Pathways

    PubMed Central

    Nishimura, Tomoko; Ishima, Tamaki; Iyo, Masaomi; Hashimoto, Kenji

    2008-01-01

    Background Selective serotonin reuptake inhibitors (SSRIs) have been widely used and are a major therapeutic advance in psychopharmacology. However, their pharmacology is quite heterogeneous. The SSRI fluvoxamine, with sigma-1 receptor agonism, is shown to potentiate nerve-growth factor (NGF)-induced neurite outgrowth in PC 12 cells. However, the precise cellular and molecular mechanisms underlying potentiation by fluvoxamine are not fully understood. In this study, we examined the roles of cellular signaling pathways in the potentiation of NGF-induced neurite outgrowth by fluvoxamine and sigma-1 receptor agonists. Methods and Findings The effects of three SSRIs (fluvoxamine, sertraline, paroxetine) and three sigma-1 receptor agonists (SA4503, 4-phenyl-1-(4-phenylbutyl) piperidine (PPBP), and dehydroepiandrosterone (DHEA)-sulfate) on NGF-induced neurite outgrowth in PC12 cells were examined. Also examined were the effects of the sigma-1 receptor antagonist NE-100, inositol 1,4,5-triphosphate (IP3) receptor antagonist, and specific inhibitors of signaling pathways in the potentiation of NGF-induced neurite outgrowth by selective sigma-1 receptor agonist SA4503. Fluvoxamine (but not sertraline or paroxetine) and the sigma-1 receptor agonists SA4503, PPBP, and DHEA-sulfate significantly potentiated NGF-induced neurite outgrowth in PC12 cells in a concentration-dependent manner. The potentiation by fluvoxamine and the three sigma-1 receptor agonists was blocked by co-administration of the selective sigma-1 receptor antagonist NE-100, suggesting that sigma-1 receptors play a role in blocking the enhancement of NGF-induced neurite outgrowth. Moreover, the potentiation by SA4503 was blocked by co-administration of the IP3 receptor antagonist xestospongin C. In addition, the specific inhibitors of phospholipase C (PLC-γ), phosphatidylinositol 3-kinase (PI3K), p38MAPK, c-Jun N-terminal kinase (JNK), and the Ras/Raf/mitogen-activated protein kinase (MAPK) signaling pathways

  5. Axelrod's model with surface tension

    NASA Astrophysics Data System (ADS)

    Pace, Bruno; Prado, Carmen P. C.

    2014-06-01

    In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding from the set of potentially interacting neighbors those that would never possibly exchange. Although the alteration proposed does not alter the state space topologically, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behavior is considerably richer, and cultural regions become stable leading to the formation of different spatiotemporal patterns. A metastable "glassy" phase emerges between the globalized phase and the disordered, multicultural phase.

  6. [Treatment of tension headache].

    PubMed

    Schoenen, J

    2000-01-01

    The scientific basis of tension- type headache suffers from the lack of precise pathophysiological knowledge and the heterogenecity of this disorder. Treatment of acute tension-type headache episodes is more effective with an NSAIDs (ibuprofen 400-800mg, naproxen 550-825mg, ketoprofen 50-75mg) than with aspirin or paracetamol. Caffein containing preparations of NSAIDs are slightly superior, but should not be taken frequently to avoid headache chronification. For chronic tension-type headache, relaxation therapies with EMG biofeedback and tricyclics have about the same efficacy rate of 40-50p.100. Physical therapy and acupuncture are in general less effective. There is thus clearly a need for better strategies, e.g. combination of available therapies and novel approaches.

  7. Tension solar mirror

    SciTech Connect

    Russo, W.P.

    1986-09-02

    A solar collector is described comprising a central tower having a solar receiver thereon; tension towers positioned concentrically about the central tower;a rigid inner ring disposed about the central tower and sized to permit vertical movement relative to the central tower; cables extending between the inner ring and the tops of each of the tension towers; and a reflectively-coated sheet of flexible material attached to the upper surface of the cables; whereby the action of gravity on the cables and the sheet form a concave reflector for focusing solar energy onto the solar receiver.

  8. [Association between the frequency and duration, but not the intensity, of headache with mechanical hypersensitivity and the health of patients with tension-type headache].

    PubMed

    Palacios-Cena, M; Fernandez-Munoz, J J; Cigaran-Mendez, M; Moron-Verdasco, A; Fernandez-de-Las-Penas, C

    2015-03-16

    Introduccion. La asociacion entre las variables clinicas de la cefalea y otras variables neurofisiologicas o de salud es controvertida. Objetivo. Determinar la asociacion de la frecuencia, duracion e intensidad del dolor con la sensibilidad mecanica craneocervical, considerando el efecto de otras variables de salud y fisicas. Pacientes y metodos. Se incluyeron 72 pacientes con cefalea de tension. Se mantuvo un diario mensual para determinar la frecuencia, duracion e intensidad del dolor. Se calcularon los umbrales de dolor a la presion (UDP) y la sensibilidad a la palpacion sobre la region craneocervical, calidad de vida (Short Form-36), discapacidad, depresion y movilidad cervical. Se introdujeron todas las variables en modelos de regresion logistica jerarquica para determinar las interacciones. Resultados. Se encontraron correlaciones entre la frecuencia y duracion de la cefalea, pero no la intensidad, con el resto de variables. El analisis de regresion mostro que la combinacion del UDP sobre el temporal, dolor corporal, edad y rol fisico explicaba el 22,3% de la varianza de la frecuencia, mientras que la combinacion de salud general, UDP sobre el trapecio superior y frecuencia del dolor explicaba el 20% de la varianza de la duracion (p < 0,001). Conclusiones. Este estudio ha encontrado que la frecuencia y la duracion de la cefalea, pero no la intensidad, se encuentran asociadas con variables neurofisiologicas, como el UDP sobre el cuello/cabeza o la percepcion de dolor generalizado en la cefalea tensional. Otras variables, como la edad, el rol fisico y la salud general tambien mostraron una asociacion con la frecuencia y la duracion de la cefalea.

  9. Are Merkel cell-neurite reciprocal synapses involved in the initiation of tactile responses in salamander skin?

    PubMed Central

    Diamond, J; Holmes, M; Nurse, C A

    1986-01-01

    In salamander skin the Merkel cell-neurite complexes located near the base of the epidermis are the morphological correlates of the rapidly adapting touch receptors (Parducz, Leslie, Cooper, Turner & Diamond, 1977). The present electron microscopic studies revealed that these complexes contain reciprocal synapses polarized in the direction Merkel cell to neurite, and in the opposite direction, neurite to Merkel cell. The possible involvement of chemical transmission in the initiation of the mechanosensory response, was studied in vitro with the aid of a stable skin-nerve preparation in which single mechanoreceptors were activated under controlled conditions. Mechanosensitivity was measured with a calibrated prodder (tip diameter 10-30 micron) applied to random or selected points on the surface of the skin while the afferent impulse was recorded in the attached nerve twig. In some experiments the (tungsten) prodder was also used as a surface electrode, allowing the same mechanosensory axon to be excited mechanically (i.e. physiologically), and/or electrically. When applied at a single 'touch spot', suitably timed subthreshold mechanical and subthreshold electrical stimuli could summate to produce a single action potential. The temperature coefficient (Q10) between 5 and 15 degrees C for the latency of the afferent spike was small, in the range 1.3-2, whether it was evoked by mechanical or electrical stimulation. The latency following the mechanical stimulus, which included the transduction step, was longer than that following the electrical stimulus by 0.5-2.5 ms, and this additional delay was also relatively insensitive to temperature. In several cases removal of the epidermis with its Merkel cells (and presumably the most distal portions of the afferent nerve terminations) did not render the remaining skin totally insensitive to mechanical stimulation; however, the remaining receptive elements, though still rapidly adapting, generally had increased mechanosensory

  10. Dynamic aspects of amphibian neurite growth and the effects of an applied electric field.

    PubMed Central

    McCaig, C D

    1986-01-01

    The dynamics of growth of earliest spinal neurites from Xenopus laevis have been studied in vitro in the presence and absence of an applied d.c. electric field. Control and cathode-directed neurites grew at a rate of about 30 micron/h: growth of anodal-facing neurites was 8 times slower. Periods of arrested growth were common in cultured neurones; these lasted 2-3 times longer in an applied electric field. The likelihood and the severity of neurite reabsorption was greatest in neurites directed towards the anode. Many neurites turned to direct their growth towards the cathode. As this happened their rate of growth increased 2-3-fold. The electric field further shaped neurite morphology by increasing the number of filopodia at the growth cone and by increasing the number of cytoplasmic spines along a neurite shaft. The electric field induced an asymmetry in the distribution of these cytoplasmic projections; greater numbers being found on the cathodal-facing than on the anodal-facing side. Implications of these data for nerve growth in development and in regeneration are discussed. Images Plate 1 PMID:3795068

  11. Repeated, intermittent treatment with amphetamine induces neurite outgrowth in rat pheochromocytoma cells (PC12 cells).

    PubMed

    Park, Yang Hae; Kantor, Lana; Wang, Kevin K W; Gnegy, Margaret E

    2002-09-27

    Repeated, intermittent treatment with amphetamine (AMPH) leads to long-term neurobiological adaptations in rat brain including an increased number and branching of dendritic spines. This effect depends upon several different cell types in the intact brain. Here we demonstrate that repeated, intermittent AMPH treatment induces neurite outgrowth in cultured PC12 cells without the requirement for integrated synaptic pathways. PC12 cells were treated with 1 micro M AMPH for 5 min a day, for 5 days. After 10 days of withdrawal, there was an increase in the percentage of cells with neurites ( approximately 30%) and the length of neurites as well as an increase in the level of GAP-43 and neurofilament-M. Neurite outgrowth was enhanced as withdrawal time was increased. Neurite outgrowth was much greater following repeated, intermittent treatment with AMPH compared to continuous or single treatment with AMPH. Pretreatment with cocaine, a monoamine transporter blocker, inhibited the AMPH-mediated increase in neurite outgrowth. Neither NGF antibody nor DA receptor antagonists blocked AMPH-induced neurite outgrowth, demonstrating that AMPH-induced neurite outgrowth is not dependent on endogenous NGF release or DA receptors. Thus we have demonstrated that repeated, intermittent treatment with AMPH has a neurotrophic effect in PC12 cells. The effect requires the action of AMPH on the norepinephrine transporter, and shares characteristics in its development with other forms of sensitization but does not require an intact neuroanatomy.

  12. Munc18 and Munc13 regulate early neurite outgrowth

    PubMed Central

    Broeke, Jurjen H.P.; Roelandse, Martijn; Luteijn, Maartje J.; Boiko, Tatiana; Matus, Andrew; Toonen, Ruud F.; Verhage, Matthijs

    2010-01-01

    Background information. During development, growth cones of outgrowing neurons express proteins involved in vesicular secretion, such as SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) proteins, Munc13 and Munc18. Vesicles are known to fuse in growth cones prior to synapse formation, which may contribute to outgrowth. Results. We tested this possibility in dissociated cell cultures and organotypic slice cultures of two release-deficient mice (Munc18-1 null and Munc13-1/2 double null). Both types of release-deficient neurons have a decreased outgrowth speed and therefore have a smaller total neurite length during early development [DIV1–4 (day in vitro 1–4)]. In addition, more filopodia per growth cone were observed in Munc18-1 null, but not WT (wild-type) or Munc13-1/2 double null neurons. The smaller total neurite length during early development was no longer observed after synaptogenesis (DIV14–23). Conclusion. These data suggest that the inability of vesicle fusion in the growth cone affects outgrowth during the initial phases when outgrowth speed is high, but not during/after synaptogenesis. Overall, the outgrowth speed is probably not rate-limiting during neuronal network formation, at least in vitro. In addition, Munc18, but not Munc13, regulates growth cone filopodia, potentially via its previously observed effect on filamentous actin. PMID:20497124

  13. Creating Tension in Writing.

    ERIC Educational Resources Information Center

    Folta, Bernarr

    This paper discusses the rationale and teaching methods for a six-week unit, for a high school freshman English Class, on perception, semantics, and writing, which places special focus on developing tension in student writing. The first four objectives of the course focus on perception and the next two focus on semantics. The seventh…

  14. Coping with Dialectical Tensions.

    ERIC Educational Resources Information Center

    Brockriede, Wayne

    This paper discusses some of the central issues involved in philosophizing about rhetoric by raising two primary questions within the context of three traditional branches of philosophy: ontology, axiology, and epistemology. The two questions raised are: What are dialectical tensions in a philosophy of rhetoric? and How does a person try to cope…

  15. The Tension Literature.

    ERIC Educational Resources Information Center

    Frederick, A. B.

    This is a bibliography of literature on the subject of tension. Books, films, and periodicals with a bearing on stress, relaxation, anxiety, and/or methods of controlling stress are listed from the fields of physiology, psychology, and philosophy. New methods such as transcendental meditation and biofeedback are analyzed briefly and criteria are…

  16. Neurite outgrowth of NG108-15 cells induced by heat shock protein 90 inhibitors.

    PubMed

    Jin, Erika; Sano, Mamoru

    2008-12-01

    We previously reported that radicicol (Rad) and geldanamycin (Geld), heat shock protein 90 (Hsp90) inhibitors, potentiate neurite growth of cultured sensory neurons from chick embryo. We now show that the antibiotics induce neurite growth in NG108-15 cells. Treatment of the cells with these drugs caused transient decrease in protein levels of Raf1, ERK1/2, phosphorylated ERK1/2, Akt1, and CDK4. The neurite growth of NG108-15 induced by the inhibitors was blocked by actynomycin D, but the neurite growth stimulated by dbcAMP in the cells was not affected. The neurite growth could be due to a change in the synthesis of some specific protein(s) and is speculated to be due to the transient downregulation of particular-signaling molecules stabilized by Hsp90.

  17. P2X1 Receptor-Mediated Ca(2+) Influx Triggered by DA-9801 Potentiates Nerve Growth Factor-Induced Neurite Outgrowth.

    PubMed

    Back, Moon Jung; Lee, Hae Kyung; Lee, Joo Hyun; Fu, Zhicheng; Son, Mi Won; Choi, Sang Zin; Go, Hyo Sang; Yoo, Sungjae; Hwang, Sun Wook; Kim, Dae Kyong

    2016-11-16

    Nerve growth factor (NGF)-induced neuronal regeneration has emerged as a strategy to treat neuronal degeneration-associated disorders. However, direct NGF administration is limited by the occurrence of adverse effects at high doses of NGF. Therefore, development of a therapeutic strategy to promote the NGF trophic effect is required. In view of the lack of understanding of the mechanism for potentiating the NGF effect, this study investigated molecular targets of DA-9801, a well-standardized Dioscorea rhizome extract, which has a promoting effect on NGF. An increase in intracellular calcium ion level was induced by DA-9801, and chelation of extracellular calcium ions with ethylene-bis(oxyethylenenitrilo)tetraacetic acid (EGTA) suppressed the potentiating effect of DA-9801 on NGF-induced neurite outgrowth. In addition, EGTA treatment reduced the DA-9801-induced phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2), the major mediators of neurite outgrowth. To find which calcium ion-permeable channel contributes to the calcium ion influx induced by DA-9801, we treated PC12 cells with various inhibitors of calcium ion-permeable channels. NF449, a P2X1 receptor selective antagonist, significantly abolished the potentiating effect of DA-9801 on NGF-induced neurite outgrowth and abrogated the DA-9801-induced ERK1/2 phosphorylation. In addition, transfection with siRNA of P2X1 receptor significantly reduced the DA-9801-enhanced neurite outgrowth. In conclusion, calcium ion influx through P2X1 receptor mediated the promoting effect of DA-9801 on NGF-induced neurite outgrowth via ERK1/2 phosphorylation.

  18. The Akt-nitric oxide-cGMP pathway contributes to nerve growth factor-mediated neurite outgrowth in apolipoprotein E knockout mice.

    PubMed

    Hashikawa-Hobara, Narumi; Hashikawa, Naoya; Yutani, Chikao; Zamami, Yoshito; Jin, Xin; Takatori, Shingo; Mio, Mitsunobu; Kawasaki, Hiromu

    2011-08-01

    Apolipoprotein E (apo)-deficient [apoE(-/-)] mice have peripheral sensory nerve defects and a reduced and delayed response to noxious thermal stimuli. However, to date, no report has focused on the influence of apoE deficiency on calcitonin gene-related peptide (CGRP)-containing nerve fiber extensions. We have shown that the density of CGRP-containing nerve fibers decreases in mesenteric arteries of apoE(-/-) mice compared with wild-type mice. Here, we investigated whether apoE deficiency is involved in nerve growth factor (NGF)-induced CGRP-containing nerve regeneration using apoE(-/-) mice. NGF-mediated CGRP-like immunoreactivity (LI)-neurite outgrowth in apoE(-/-) cultured dorsal root ganglia (DRG) cells was significantly lower than that in wild-type cultures. However, the level of NGF receptor mRNA in apoE(-/-) DRG cells was similar to that in wild-type mice. To clarify the mechanism of the impaired ability of NGF-mediated neurite outgrowth, we focused on the Akt-nitric oxide (NO)-cGMP pathway. Expression of phosphorylated Akt was significantly reduced in apoE(-/-) DRG. The NO donor, sodium nitroprusside or S-nitroso-N-acetylpenicillamine, did not affect NGF-mediated neurite outgrowth in apoE(-/-) cultured DRG cells. However, 8-bromoguanosine 3',5'-cyclic monophosphate sodium salt n-hydrate, a cGMP analog, induced NGF-mediated nerve facilitation similar to wild-type NGF-mediated neurite outgrowth levels. Furthermore, in apoE(-/-) DRG, soluble guanylate cyclase expression was significantly lower than that in wild-type DRG. These results suggest that in apoE(-/-) mice the Akt-NO-cGMP pathway is impaired, which may be caused by NGF-mediated CGRP-LI-neurite outgrowth defects.

  19. Intracellular calcium and cyclic nucleotide levels modulate neurite guidance by microtopographical substrate features.

    PubMed

    Li, Shufeng; Tuft, Bradley; Xu, Linjing; Polacco, Marc; Clarke, Joseph C; Guymon, C Allan; Hansen, Marlan R

    2016-08-01

    Micro- and nanoscale surface features have emerged as potential tools to direct neurite growth into close proximity with next generation neural prosthesis electrodes. However, the signaling events underlying the ability of growth cones to respond to topographical features remain largely unknown. Accordingly, this study probes the influence of [Ca(2+) ]i and cyclic nucleotide levels on the ability of neurites from spiral ganglion neurons (SGNs) to precisely track topographical micropatterns. Photopolymerization and photomasking were used to generate micropatterned methacrylate polymer substrates. Dissociated SGN cultures were plated on the micropatterned surfaces. Calcium influx and release from internal stores were manipulated by elevating extracellular K(+) , maintenance in calcium-free media, or bath application of various calcium channel blockers. Cyclic nucleotide activity was increased by application of cpt-cAMP or 8-Br-cGMP. Elevation of [Ca(2+) ]i by treatment of cultures with elevated potassium reduced neurite alignment to physical microfeatures. Maintenance of cultures in Ca(2+) -free medium or treatment with the non-selective voltage-gated calcium channel blocker cadmium or L-type Ca(2+) channel blocker nifedipine did not signficantly alter SGN neurite alignment. By contrast, ryanodine or xestospongin C, which block release of internal calcium stores via ryanodine-sensitive channels or inositol-1,4,5-trisphosphate receptors respectively, each significantly decreased neurite alignment. Cpt-cAMP significantly reduced neurite alignment while 8-Br-cGMP significantly enhanced neurite alignment. Manipulation of [Ca(2+) ]i or cAMP levels significantly disrupts neurite guidance while elevation of cGMP levels increases neurite alignment. The results suggest intracellular signaling pathways similar to those recruited by chemotactic cues are involved in neurite guidance by topographical features. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2037

  20. Axonal shearing in mature cortical neurons induces attempted regeneration and the reestablishment of neurite polarity.

    PubMed

    Blizzard, Catherine A; King, Anna E; Haas, Matilda A; O'Toole, David A; Vickers, James C; Dickson, Tracey C

    2009-12-01

    While functional recovery after injury is limited, it has become evident that the mature central nervous system does retain some ability to regenerate. This study investigated the intrinsic capacity of relatively mature cortical neurons (21 days in vitro) to respond to axonal loss. Neurons, growing as clusters on poly-L-lysine, were completely sheared of axons through chemical and mechanical disruption and transferred to either an intact astrocyte monolayer or a substrate of poly-L-lysine. Injured neurons exhibited a regenerative sprouting response that was independent of neuronal cell division or neural progenitors, as demonstrated by negative bromodeoxyuridine (BrdU) and the neuronal precursor intermediate filament nestin, labeling. At 24 h after injury, neurons had extended appropriately polarized neurites, demonstrated by compartmentalized microtubule-associated proteins MAP2 and tau immunolabeling. Newly sprouting axons were tipped by growth cones; however, growth cones on the tips of sprouting axons (mean area, 26.32 +/- 2.20 microm) were significantly (p<0.05) smaller than their developmental counterparts (mean area, 48.64 +/- 5.9 microm), independent of substrate. Furthermore, live imaging indicated that regenerating neurons exhibited distinct axonal dynamics, with a significant (p<0.05) reduction (70%) in pausing, considered vital for interstitial branching and pathfinding, relative to developmental growth cones. This study indicates that mature cultured cortical pyramidal and interneurons have the intrinsic potential to survive, extend processes, and reestablish neurite polarity following significant physical damage. These results may aid in defining the cellular basis of neuronal structural plasticity and defining the role of astrocyte reactivity in the response to trauma.

  1. Sodium channel activation augments NMDA receptor function and promotes neurite outgrowth in immature cerebrocortical neurons

    PubMed Central

    George, Joju; Dravid, Shashank M.; Prakash, Anand; Xie, Jun; Peterson, Jennifer; Jabba, Sairam V.; Baden, Daniel G.; Murray, Thomas F.

    2009-01-01

    A range of extrinsic signals, including afferent activity, affect neuronal growth and plasticity. Neuronal activity regulates intracellular Ca2+ and activity-dependent calcium signaling has been shown to regulate dendritic growth and branching (Konur and Ghosh, 2005). NMDA receptor (NMDAR) stimulation of Ca2+/calmodulin-dependent protein kinase signaling cascades has moreover been demonstrated to regulate neurite/axonal outgrowth (Wayman et al., 2004). We used a sodium channel activator, brevetoxin (PbTx-2), to explore the relationship between intracellular [Na+] and NMDAR-dependent development. PbTx-2 alone, at a concentration of 30 nM, did not affect Ca2+ dynamics in DIV-2 cerebrocortical neurons; however, this treatment robustly potentiated NMDA-induced Ca2+ influx. The 30 nM PbTx-2 treatment produced a maximum [Na+]i of 16.9 ± 1.5 mM representing an increment of 8.8 ± 1.8 mM over basal. The corresponding membrane potential change produced by 30 nM PbTx-2 was modest and therefore insufficient to relieve the voltage-dependent Mg2+ block of NMDARs. To unambiguously demonstrate the enhancement of NMDA receptor function by PbTx-2, we recorded single-channel currents from cell-attached patches. PbTx-2 treatment was found to increase both the mean open time and open probability of NMDA receptors. These effects of PbTx-2 on NMDA receptor function were dependent on extracellular Na+ and activation of Src kinase. The functional consequences of PbTx-2-induced enhancement of NMDAR function were evaluated in immature cerebrocortical neurons. PbTx-2 concentrations between 3 and 300 nM enhanced neurite outgrowth. Voltage-gated sodium channel activators may accordingly represent a novel pharmacologic strategy to regulate neuronal plasticity through an NMDA receptor and Src family kinase-dependent mechanism. PMID:19279266

  2. Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. 3: Tension-compression anisotropy

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gaab, T. P.; Gayda, J.; Hemker, K. J.

    1985-01-01

    Single crystal superalloy specimens with various crystallographic directions along their axes were tested in compression at room temperature, 650, 760, 870, and 980 deg C. These results are compared with the tensile behavior studied previously. The alloy, Rene N4, was developed for gas turbine engine blades and has the nominal composition 3.7 Al, 4.2 Ti, 4 Ta, 0.5 Nb, 6 W, 1.5 Mo 9 Cr. 7.5 Co, balance Ni, in weight percent. Slip trace analysis showed that primary cube slip occurred even at room temperature for the 111 specimens. With increasing test temperature more orientations exhibited primary cube slip, until at 870 deg C only the 100 and 011 specimens exhibited normal octahedral slip. The yield strength for octahedral slip was numerically analysed using a model proposed by Lall, Chin, and Pope to explain deviations from Schmid's Law in the yielding behavior of a single phase Gamma prime alloy, Ni3(Al, Nb). The Schmid's Law deviations in Rene N4 were found to be largely due to a tension-compression anisotropy. A second effect, which increases trength for orientations away from 001, was found to be small in Rene N4. Analysis of recently published data on the single crystal superalloy PWA 1480 yielded the same result.

  3. Respective roles of neurofilaments, microtubules, MAP1B, and tau in neurite outgrowth and stabilization.

    PubMed Central

    Shea, T B; Beermann, M L

    1994-01-01

    The respective roles of neurofilaments (NFs), microtubules (MTs), and the microtubule-associated proteins (MAPs) MAP 1B and tau on neurite outgrowth and stabilization were probed by the intracellular delivery of specific antisera into transiently permeabilized NB2a/d1 cells during treatment with dbcAMP. Intracellular delivery of antisera specific for the low (NF-L), middle (NF-M), or extensively phosphorylated high (NF-H) molecular weight subunits did not prevent initial neurite elaboration, nor did it induce retraction of existing neurites elaborated by cells that had been previously treated for 1 d with dbcAMP. By contrast, intracellular delivery of antisera directed against tubulin reduced the percentage of cells with neurites at both these time points. Intracellular delivery of anti-NF-L and anti-NF-M antisera did not induce retraction in cells treated with dbcAMP for 3 d. However, intracellular delivery of antisera directed against extensively phosphorylated NF-H, MAP1B, tau, or tubulin induced similar levels of neurite retraction at this time. Intracellular delivery of monoclonal antibodies (RT97 or SMI-31) directed against phosphorylated NF-H induced neurite retraction in cell treated with dbcAMP for 3 d; a monoclonal antibody (SMI-32) directed against nonphosphorylated NF-H did not induce neurite retraction at this time. By contrast, none of the above antisera induced retraction of neurites in cells treated with dbcAMP for 7 d. Neurites develop resistance to retraction by colchicine, first detectable in some neurites after 3 d and in the majority of neurites after 7 d of dbcAMP treatment. We therefore examined whether or not colchicine resistance was compromised by intracellular delivery of the above antisera. Colchicine treatment resulted in rapid neurite retraction after intracellular delivery of antisera directed against extensively phosphorylated NF-H, MAP1B, or tau into cells that had previously been treated with dbcAMP for 7 d. By contrast, colchicine

  4. Device for Tensioning Sheet Members

    DTIC Science & Technology

    1998-07-30

    FOR TENSIONING SHEET MEMBERS BACKGROUND OF THE INVENTION Field of the Invention This invention pertains generally to tensioning devices and more...particularly to a device for tensioning thin-sheet materials so as to prevent wrinkling. Description of the Related Art Solar power sources utilized...the system. SUMMARY OF THE INVENTION The object of this invention is to provide an apparatus for loading a thin-sheet material with tensioning

  5. Modification of Upper Thread Tensioner of Sewing Machine

    NASA Astrophysics Data System (ADS)

    Klouček, P.; Škop, P.

    Standard mechanical upper thread tensioner of sewing machines is more and more limited in use for industrial sewing machines due to increasing requests for quality and raising velocity of machines. If we omit mostly manual settings of force made only by sense, the most problematic things are influence of different friction coefficient of the different batch of threads and strong relation between thread tension and sewing machine velocity. The article describes the development focused to the elimination of the most significant disadvantages of a standard tensioner and mainly finding of new conception of the tensioner with electromagnetic brake, development and testing of its prototype.

  6. Static tensioning promotes hamstring tendons force relaxation more reliably than cycling tensioning.

    PubMed

    Piedade, Sérgio Rocha; Dal Fabbro, Inácio Maria; Mischan, Martha Maria; Piedade, Cezar; Maffulli, Nicola

    2017-08-01

    Graft elongation might be a major reason for increased anterior laxity after anterior cruciate ligament (ACL) reconstruction. This study analyzed the force relaxation values and their stabilization when single strands of the gracilis and semitendinosus tendons underwent cyclic and static tensioning at 2.5% strain level, and compared the efficiency of static and cyclic tensioning in promoting force relaxation. Eighteen gracilis tendons and 18 semitendinosus tendons from nine male cadavers (mean age: 22.44years) were subjected to 10 in vitro cyclic loads at 2.5% strain level, or to a static load at 2.5% strain level. During cyclic loading, the reduction in force values tended to stabilize after the sixth cyclic load, while, in the case of static loading, this stabilization occurred by the second minute. Comparing static and cyclic loading, the gracilis tendon had similar mechanical responses in both conditions, while the semitendinosus tendon showed greater force relaxation in static compared with cyclic loading. Considering that the semitendinosus tendon is the main component of the hamstring graft, its biomechanical response to loading should guide the tensioning protocol. Therefore, static tensioning seems more effective for promoting force relaxation of the semitendinosus tendon than cyclic tensioning. The gracilis tendon showed a similar mechanical response to either tensioning protocols. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Surface tension and microgravity

    NASA Astrophysics Data System (ADS)

    Meseguer, J.; Sanz-Andrés, A.; Pérez-Grande, I.; Pindado, S.; Franchini, S.; Alonso, G.

    2014-09-01

    The behaviour of confined liquids on board an orbiting spacecraft is mainly driven by surface tension phenomena, which cause an apparently anomalous response of the liquid when compared with the behaviour that can be observed on an Earth laboratory provided that the amount of liquid is high enough. The reason is that in an orbiting spacecraft the different inertial forces acting on the bulk of the liquid are almost zero, causing thus capillary forces to be the dominant ones. Of course, since gravity forces are proportional to the liquid volume, whereas surface tension forces are proportional to the liquid surface, there are situations on Earth where capillarity can be the dominant effect, as it happens when very small volume liquid samples are considered. However, work with small size samples may require the use of sophisticated optical devices. Leaving aside the neutral buoyancy technique, a way of handling large liquid interfaces is by using drop towers, where the sample falls subjected to the action of Earth’s gravity. This approach is suitable when the characteristic time of the problem under consideration is much smaller than the drop time. In this work the transformation of an out-of-use chimney into a drop tower is presented. Because of the miniaturization, hardiness and low cost of current electronic devices, a drop tower can be used as an inexpensive tool for undergraduate students to experimentally analyse a large variety of surface tension driven phenomena.

  8. Tension-type headache.

    PubMed

    Diamond, S

    1999-01-01

    Tension-type headaches, the most prevalent form of headache, are differentiated as being either episodic or chronic. The episodic form is a physiologic response to stress, anxiety, depression, emotional conflicts, fatigue, or repressed hostility. Treatment focuses on the use of over-the-counter or prescribed simple analgesics for pain relief. Successful treatment of the chronic form depends on recognition of depression or persistent anxiety states. Primary care physicians can effectively manage most of these patients with nonhabituating anxiolytic or antidepressant medications; however, referrals for psychotherapy may be required in some cases. When tension-type headaches occur in children and adolescents, the physician must explore the patient's family and social relationships as well as school performance. In addition to nonhabituating drug therapies, family counseling and biofeedback may be helpful. In coexisting migraine and tension-type headaches, nonhabituating analgesics may be used for the relief of acute pain; the use of ergotamine and triptans should be restricted to relief of the hard or sick headache. Tricyclic antidepressants or monoamine oxidase inhibitors are the gold standards for prophylaxis, although the selective serotonin reuptake inhibitors may be indicated in less severe cases. Several forms of biofeedback have also proved effective. Nonetheless, some patients with this form of headache may require psychiatric treatment for severe depression.

  9. Micropatterning of Neurite Outgrowth in vitro Using Micropipette Drawing

    NASA Astrophysics Data System (ADS)

    Goto, Miho; Moriguchi, Hiroyuki; Takayama, Yuzo; Kotani, Kiyoshi; Jimbo, Yasuhiko

    To understand the relationship between neuronal-network functions and single-neuron activity, construction of artificial neuronal network is one of the promising approaches. Cell patterning is a useful technique to get single-neuron-based networks in vitro. Here in this work, we propose a simple method to get simple neuronal networks, based on neurite-outgrowth guidance. Our method, referred to as “micropipette drawing” is a quite simple photomask-free technique. Growth-guiding patterns are drawn with a micropipette containing cell-adhesive solution on non-adhesive substrates. Guiding structures of approximately 10 μm width were successfully drawn and rat hippocampal neurons were cultured on the patterns. The patterned neuronal networks could be maintained for more than a week.

  10. Rabies virus neuritic paralysis: immunopathogenesis of nonfatal paralytic rabies.

    PubMed Central

    Weiland, F; Cox, J H; Meyer, S; Dahme, E; Reddehase, M J

    1992-01-01

    Two pathogenetically distinct disease manifestations are distinguished in a murine model of primary rabies virus infection with the Evelyn-Rokitnicky-Abelseth strain, rabies virus neuritic paralysis (RVNP) and fatal encephalopathogenic rabies. RVNP develops with high incidence in immunocompetent mice after intraplantar infection as a flaccid paralysis restricted to the infected limb. The histopathologic correlate of this monoplegia is a degeneration of the myelinated motor neurons of the peripheral nerve involved. While, in this model, fatal encephalopathogenic rabies develops only after depletion of the CD4 subset of T lymphocytes and without contribution of the CD8 subset, RVNP is identified as an immunopathological process in which both the CD4 and CD8 subsets of T lymphocytes are critically implicated. Images PMID:1629964

  11. Students' difficulties with tension in massless strings

    NASA Astrophysics Data System (ADS)

    Flores-García, S.; Alfaro-Avena, L. L.; Chávez-Pierce, J. E.; Luna-González, J.; González-Quezada, M. D.

    2010-12-01

    Many students enrolled in introductory mechanics courses have difficulties with understanding the concept of static equilibrium. Some of these difficulties are related to the concept of force in the context of tension in massless strings. We identify three kinds of misconceptions: Students' beliefs that the angle of the string and proximity to the object are related to the tension. Students also use incorrect compensation arguments to reason about situations where both the angle and proximity change simultaneously. These difficulties were identified during investigations conducted in laboratory and lecture sessions at three universities in the United States and Mexico.

  12. Entropic Tension in Crowded Membranes

    PubMed Central

    Lindén, Martin; Sens, Pierre; Phillips, Rob

    2012-01-01

    Unlike their model membrane counterparts, biological membranes are richly decorated with a heterogeneous assembly of membrane proteins. These proteins are so tightly packed that their excluded area interactions can alter the free energy landscape controlling the conformational transitions suffered by such proteins. For membrane channels, this effect can alter the critical membrane tension at which they undergo a transition from a closed to an open state, and therefore influence protein function in vivo. Despite their obvious importance, crowding phenomena in membranes are much less well studied than in the cytoplasm. Using statistical mechanics results for hard disk liquids, we show that crowding induces an entropic tension in the membrane, which influences transitions that alter the projected area and circumference of a membrane protein. As a specific case study in this effect, we consider the impact of crowding on the gating properties of bacterial mechanosensitive membrane channels, which are thought to confer osmoprotection when these cells are subjected to osmotic shock. We find that crowding can alter the gating energies by more than in physiological conditions, a substantial fraction of the total gating energies in some cases. Given the ubiquity of membrane crowding, the nonspecific nature of excluded volume interactions, and the fact that the function of many membrane proteins involve significant conformational changes, this specific case study highlights a general aspect in the function of membrane proteins. PMID:22438801

  13. Computer vision profiling of neurite outgrowth dynamics reveals spatiotemporal modularity of Rho GTPase signaling

    PubMed Central

    Fusco, Ludovico; Lefort, Riwal; Smith, Kevin; Benmansour, Fethallah; Gonzalez, German; Barillari, Caterina; Rinn, Bernd; Fleuret, Francois; Fua, Pascal

    2016-01-01

    Rho guanosine triphosphatases (GTPases) control the cytoskeletal dynamics that power neurite outgrowth. This process consists of dynamic neurite initiation, elongation, retraction, and branching cycles that are likely to be regulated by specific spatiotemporal signaling networks, which cannot be resolved with static, steady-state assays. We present NeuriteTracker, a computer-vision approach to automatically segment and track neuronal morphodynamics in time-lapse datasets. Feature extraction then quantifies dynamic neurite outgrowth phenotypes. We identify a set of stereotypic neurite outgrowth morphodynamic behaviors in a cultured neuronal cell system. Systematic RNA interference perturbation of a Rho GTPase interactome consisting of 219 proteins reveals a limited set of morphodynamic phenotypes. As proof of concept, we show that loss of function of two distinct RhoA-specific GTPase-activating proteins (GAPs) leads to opposite neurite outgrowth phenotypes. Imaging of RhoA activation dynamics indicates that both GAPs regulate different spatiotemporal Rho GTPase pools, with distinct functions. Our results provide a starting point to dissect spatiotemporal Rho GTPase signaling networks that regulate neurite outgrowth. PMID:26728857

  14. Long-term neurite orientation on astrocyte monolayers aligned by microtopography.

    PubMed

    Sørensen, Annette; Alekseeva, Tijna; Katechia, Kashyap; Robertson, Mary; Riehle, Mathis O; Barnett, Susan C

    2007-12-01

    After spinal cord injury neuronal connections are not easily re-established. Success has been hampered by the lack of orientation of neurites inside scar tissue and a lack of neurites crossing out of the site of injury. Oriented scaffolds in biodegradable polymers could be an excellent way to support both the orientation of neurites within the injury site as well as aiding their crossing out of the lesion. To establish the validity of using grooved micro-topography in polycaprolactone in combination with glia we have studied the long-term (3 weeks) orientation of neuronal cells on monolayers of astrocytes on the top of grooved topographies of various dimensions. We find that neurites are significantly aligned by groove/ridge type topographies which are "buried" under a monolayer of astrocytes for up to 3 weeks. This alignment is significantly lower than that of neurites growing directly on the topography, but these neurons do not survive on the poly-l-lysine coated polymer for more than a week. The alignment of neurites on the astrocyte layer to the underlying topography decreases over time, and with groove width. Topographies with 12.5 or 25 microm lateral dimension appear optimal for the long-term alignment and can support myelination. We have shown for the first time that micro-topography can act through an overlaid astrocyte layer and results in aligned neurites in long-term culture and that these can be myelinated by endogenous oligodendrocytes.

  15. Triggering of high-speed neurite outgrowth using an optical microheater.

    PubMed

    Oyama, Kotaro; Zeeb, Vadim; Kawamura, Yuki; Arai, Tomomi; Gotoh, Mizuho; Itoh, Hideki; Itabashi, Takeshi; Suzuki, Madoka; Ishiwata, Shin'ichi

    2015-11-16

    Optical microheating is a powerful non-invasive method for manipulating biological functions such as gene expression, muscle contraction, and cell excitation. Here, we demonstrate its potential usage for regulating neurite outgrowth. We found that optical microheating with a water-absorbable 1,455-nm laser beam triggers directional and explosive neurite outgrowth and branching in rat hippocampal neurons. The focused laser beam under a microscope rapidly increases the local temperature from 36 °C to 41 °C (stabilized within 2 s), resulting in the elongation of neurites by more than 10 μm within 1 min. This high-speed, persistent elongation of neurites was suppressed by inhibitors of both microtubule and actin polymerization, indicating that the thermosensitive dynamics of these cytoskeletons play crucial roles in this heat-induced neurite outgrowth. Furthermore, we showed that microheating induced the regrowth of injured neurites and the interconnection of neurites. These results demonstrate the efficacy of optical microheating methods for the construction of arbitrary neural networks.

  16. CHLORHEXIDINE INHIBITS L1 CELL ADHESION MOLECULE MEDIATED NEURITE OUTGROWTH IN VITRO

    PubMed Central

    Milstone, Aaron M.; Bamford, Penny; Aucott, Susan W.; Tang, Ningfeng; White, Kimberly R.; Bearer, Cynthia F.

    2013-01-01

    Background Chlorhexidine is a skin disinfectant that reduces skin and mucous membrane bacterial colonization and inhibits organism growth. Despite numerous studies assessing chlorhexidine safety in term infants, residual concerns have limited its use in hospitalized neonates, especially low birth weight preterm infants. The aim of this study was to assess the potential neurotoxicity of chlorhexidine on the developing central nervous system using a well-established in vitro model of neurite outgrowth that includes laminin and L1 cell adhesion molecule (L1) as neurite outgrowth promoting substrates. Methods Cerebellar granule neurons are plated on either poly L-lysine, L1 or laminin. Chlorhexidine, hexachlorophene or their excipients are added to the media. Neurons are grown for 24 h, then fixed and neurite length measured. Results Chlorhexidine significantly reduced the length of neurites grown on L1 but not laminin. Chlorhexidine concentrations as low as 125 ng/ml statistically significantly reduced neurite length on L1. Hexachlorophene did not affect neurite length. Conclusion Chlorhexidine at concentrations detected in the blood following topical applications in preterm infants specifically inhibited L1 mediated neurite outgrowth of cerebellar granule neurons. It is now vital to determine whether the blood brain barrier is permeable to chlorhexidine in preterm infants. PMID:24126818

  17. Neurite outgrowth at the interface of 2D and 3D growth environments

    NASA Astrophysics Data System (ADS)

    Kofron, Celinda M.; Fong, Vivian J.; Hoffman-Kim, Diane

    2009-02-01

    Growing neurons navigate complex environments, but in vitro systems for studying neuronal growth typically limit the cues to flat surfaces or a single type of cue, thereby limiting the resulting growth. Here we examined the growth of neurons presented with two-dimensional (2D) substrate-bound cues when these cues were presented in conjunction with a more complex three-dimensional (3D) architecture. Dorsal root ganglia (DRG) explants were cultured at the interface between a collagen I matrix and a glass coverslip. Laminin (LN) or chondroitin sulfate proteoglycans (CSPG) were uniformly coated on the surface of the glass coverslip or patterned in 50 µm tracks by microcontact printing. Quantitative analysis of neurite outgrowth with a novel grid system at multiple depths in the gel revealed several interesting trends. Most of the neurites extended at the surface of the gel when LN was presented whereas more neurites extended into the gel when CSPG was presented. Patterning of cues did not affect neurite density or depth of growth. However, neurite outgrowth near the surface of the gel aligned with LN patterns, and these extensions were significantly longer than neurites extended in other cultures. In interface cultures, DRG growth patterns varied with the type of cue where neurite density was higher in cultures presenting LN than in cultures presenting CSPG. These results represent an important step toward understanding how neurons integrate local structural and chemical cues to make net growth decisions.

  18. Positive and negative cues for modulating neurite dynamics and receptor expression.

    PubMed

    Wrobel, Melissa R; Sundararaghavan, Harini G

    2017-03-27

    Many current peripheral nerve repair strategies focus on delivering positive, growth promoting cues (e.g. extracellular matrix, ECM) while eliminating negative, growth inhibiting cues (e.g. chondroitin sulfate proteoglycans, CSPGs) at the injury site. We hypothesized that recapitulating the positive and negative cues of the peripheral nerve injury microenvironment would improve regeneration. First, we tested the effects of a characteristic CSPG, chondroitin sulfate A (CSA) on neurite dynamics of dissociated chick embryo dorsal root ganglion (DRG) neurons using time lapse video microscopy. DRG growth was recorded on different adhesive substrates, including a novel, porcine-derived spinal cord matrix (SCM). The SCM significantly increased frequency of neurite extension coordinated by a significant reduction in the neurites' time spent stalled. The SCM also mitigated inhibitory effects of CSA, producing longer neurites than the controls without CSA treatment. Next we aimed to elucidate receptors involved in mediating this behavior by testing the ability of CSA to upregulate cell-substrate binding receptors using flow cytometry. Our results showed a significant increase in syndecan-3 receptor expression in neurons treated with CSA. Furthermore, syndecans would most likely bind to the sulfated glycosaminoglycans measured in the SCM. Finally, we evaluated neurite growth on biomaterial scaffolds featuring CSA and SCM cues. Our results showed significantly increased neurite outgrowth on electrospun hyaluronic acid fibers with SCM and low levels of CSA. Higher incorporation of CSA maintained its inhibitory properties. Future work will evaluate coupling CSPGs with growth-permissive ECM to assess the combined effect on neurite outgrowth.

  19. Neurite dispersion: a new marker of multiple sclerosis spinal cord pathology?

    PubMed

    Grussu, Francesco; Schneider, Torben; Tur, Carmen; Yates, Richard L; Tachrount, Mohamed; Ianuş, Andrada; Yiannakas, Marios C; Newcombe, Jia; Zhang, Hui; Alexander, Daniel C; DeLuca, Gabriele C; Gandini Wheeler-Kingshott, Claudia A M

    2017-09-01

    Conventional magnetic resonance imaging (MRI) of the multiple sclerosis spinal cord is limited by low specificity regarding the underlying pathological processes, and new MRI metrics assessing microscopic damage are required. We aim to show for the first time that neurite orientation dispersion (i.e., variability in axon/dendrite orientations) is a new biomarker that uncovers previously undetected layers of complexity of multiple sclerosis spinal cord pathology. Also, we validate against histology a clinically viable MRI technique for dispersion measurement (neurite orientation dispersion and density imaging, NODDI), to demonstrate the strong potential of the new marker. We related quantitative metrics from histology and MRI in four post mortem spinal cord specimens (two controls; two progressive multiple sclerosis cases). The samples were scanned at high field, obtaining maps of neurite density and orientation dispersion from NODDI and routine diffusion tensor imaging (DTI) indices. Histological procedures provided markers of astrocyte, microglia, myelin and neurofilament density, as well as neurite dispersion. We report from both NODDI and histology a trend toward lower neurite dispersion in demyelinated lesions, indicative of reduced neurite architecture complexity. Also, we provide unequivocal evidence that NODDI-derived dispersion matches its histological counterpart (P < 0.001), while DTI metrics are less specific and influenced by several biophysical substrates. Neurite orientation dispersion detects a previously undescribed and potentially relevant layer of microstructural complexity of multiple sclerosis spinal cord pathology. Clinically feasible techniques such as NODDI may play a key role in clinical trial and practice settings, as they provide histologically meaningful dispersion indices.

  20. Effects of selective inhibition of protein kinase C, cyclic AMP-dependent protein kinase, and Ca(2+)-calmodulin-dependent protein kinase on neurite development in cultured rat hippocampal neurons.

    PubMed

    Cabell, L; Audesirk, G

    1993-06-01

    parameter that was measured (including viability). These results suggest that these three protein kinases selectively modulate different aspects of neurite development. The university of effects caused by calmodulin inhibition make it impossible to determine if there are specific targets of calmodulin action involved in neurite development. Finally, our data indicate that some superficially similar characteristics of neuronal differentiation, such as neurite initiation and branching, may be controlled by quite different molecular mechanisms.

  1. Carbon speciation and surface tension of fog

    USGS Publications Warehouse

    Capel, P.D.; Gunde, R.; Zurcher, F.; Giger, W.

    1990-01-01

    The speciation of carbon (dissolved/particulate, organic/inorganic) and surface tension of a number of radiation fogs from the urban area of Zurich, Switzerland, were measured. The carbon species were dominated by "dissolved" organic carbon (DOC; i.e., the fraction that passes through a filter), which was typically present at levels of 40-200 mg/L. Less than 10% of the DOC was identified as specific individual organic compounds. Particulate organic carbon (POC) accounted for 26-41% of the mass of the particles, but usually less than 10% of the total organic carbon mass. Inorganic carbon species were relatively minor. The surface tensions of all the measured samples were less than pure water and were correlated with their DOC concentrations. The combination of high DOC and POC and low surface tension suggests a mechanism for the concentration of hydrophobic organic contaminants in the fog droplet, which have been observed by numerous investigators. ?? 1990 American Chemical Society.

  2. Repulsive gravity in tension stars

    NASA Astrophysics Data System (ADS)

    Katz, J.; Lynden-Bell, D.

    1991-09-01

    In stars, pressure opposes the attractive force of gravity. In general relativity, if the pressure is negative (a tension) and P is less than -1/3 rho(c)-squared, then the resulting gravity is repulsive. Such material is invoked in cosmology to give the inflation of the universe. In tension stars, this repulsive gravity is balanced by the tension. The simplest tension stars only exist in esoteric situations beyond the neck of an Einstein-Rosen bridge in Schwarzschild space. Here, tension material is confined within a massive shell of normal matter. The resulting object, while still repulsive inside, has an attractive exterior gravity and can, in principle, exist without horizons.

  3. TBC1D12 is a novel Rab11-binding protein that modulates neurite outgrowth of PC12 cells

    PubMed Central

    2017-01-01

    Recycling endosomes are generally thought to play a central role in endocytic recycling, but recent evidence has indicated that they also participate in other cellular events, including cytokinesis, autophagy, and neurite outgrowth. Rab small GTPases are key regulators in membrane trafficking, and although several Rab isoforms, e.g., Rab11, have been shown to regulate recycling endosomal trafficking, the precise mechanism by which these Rabs regulate recycling endosomes is not fully understood. In this study, we focused on a Rab-GTPase-activating protein (Rab-GAP), one of the key regulators of Rabs, and comprehensively screened 43 mammalian Tre-2/Bub2/Cdc16 (TBC)/Rab-GAP-domain-containing proteins (TBC proteins) for proteins that specifically localize on recycling endosomes in mouse embryonic fibroblasts (MEFs). Four of the 43 mammalian TBC proteins screened, i.e., TBC1D11, TBC1D12, TBC1D14, and EVI5, were found to colocalize well with transferrin receptor, a well-known recycling endosome marker. We further investigated the biochemical properties of TBC1D12, a previously uncharacterized TBC protein. The results showed that TBC1D12 interacted with active Rab11 through its middle region and that it did not display Rab11-GAP activity in vitro. The recycling endosomal localization of TBC1D12 was found to depend on the expression of Rab11. We also found that TBC1D12 expression had no effect on common Rab11-dependent cellular events, e.g., transferrin recycling, in MEFs and that it promoted neurite outgrowth, a specialized Rab11-dependent cellular event, of PC12 cells independently of its GAP activity. These findings indicated that TBC1D12 is a novel Rab11-binding protein that modulates neurite outgrowth of PC12 cells. PMID:28384198

  4. Nanostructured Polyaniline Coating on ITO Glass Promotes the Neurite Outgrowth of PC 12 Cells by Electrical Stimulation.

    PubMed

    Wang, Liping; Huang, Qianwei; Wang, Jin-Ye

    2015-11-10

    A conducting polymer polyaniline (PANI) with nanostructure was synthesized on indium tin oxide (ITO) glass. The effect of electrical stimulation on the proliferation and the length of neurites of PC 12 cells was investigated. The dynamic protein adsorption on PANI and ITO surfaces in a cell culture medium was also compared with and without electrical stimulation. The adsorbed proteins were characterized using SDS-PAGE. A PANI coating on ITO surface was shown with 30-50 nm spherical nanostructure. The number of PC 12 cells was significantly greater on the PANI/ITO surface than on ITO and plate surfaces after cell seeding for 24 and 36 h. This result confirmed that the PANI coating is nontoxic to PC 12 cells. The electrical stimulation for 1, 2, and 4 h significantly enhanced the cell numbers for both PANI and ITO conducting surfaces. Moreover, the application of electrical stimulation also improved the neurite outgrowth of PC 12 cells, and the number of PC 12 cells with longer neurite lengths increased obviously under electrical stimulation for the PANI surface. From the mechanism, the adsorption of DMEM proteins was found to be enhanced by electrical stimulation for both PANI/ITO and ITO surfaces. A new band 2 (around 37 kDa) was observed from the collected adsorbed proteins when PC 12 cells were cultured on these surfaces, and culturing PC 12 cells also seemed to increase the amount of band 1 (around 90 kDa). When immersing PANI/ITO and ITO surfaces in a DMEM medium without a cell culture, the number of band 3 (around 70 kDa) and band 4 (around 45 kDa) proteins decreased compared to that of PC 12 cell cultured surfaces. These results are valuable for the design and improvement of the material performance for neural regeneration.

  5. Role of the GM1 ganglioside oligosaccharide portion in the TrkA-dependent neurite sprouting in neuroblastoma cells.

    PubMed

    Chiricozzi, Elena; Pomè, Diego Yuri; Maggioni, Margherita; Di Biase, Erika; Parravicini, Chiara; Palazzolo, Luca; Loberto, Nicoletta; Eberini, Ivano; Sonnino, Sandro

    2017-08-10

    GM1 ganglioside (II(3) NeuAc-Gg4 Cer) is known to promote neurite formation in neuroblastoma cells by activating TrkA-MAPK pathway. The molecular mechanism by which GM1 is involved in the neurodifferentiation process is still unknown, however, in vitro and in vivo evidences have suggested that the oligosaccharide portion of this ganglioside could be involved. Here, we report that, similarly to the entire GM1 molecule, its oligosaccharide II(3) NeuAc-Gg4, rather than its ceramide (Cer) portion is responsible for the neurodifferentiation process by augmenting neurite elongation and increasing the neurofilament protein expression in murine neuroblastoma cells, Neuro2a. Conversely, asialo-GM1, GM2 and GM3 oligosaccharides are not effective in neurite elongation on Neuro2a cells, whereas the effect exerted by the Fuc-GM1 oligosaccharide (IV(2) αFucII(3) Neu5Ac-Gg4 ) is similar to that exerted by GM1 oligosaccharide. The neurotrophic properties of GM1 oligosaccharide are exerted by activating the TrkA receptor and the following phosphorylation cascade. By photolabeling experiments performed with a nitrophenylazide containing GM1 oligosaccharide, labeled with tritium, we showed a direct interaction between the GM1 oligosaccharide and the extracellular domain of TrkA receptor. Moreover, molecular docking analyses confirmed that GM1 oligosaccharide binds the TrkA-NGF complex leading to a binding free energy of approx. -11.5 kcal/mol, acting as a bridge able to increase and stabilize the TrkA-NGF molecular interactions. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  6. New potent accelerator of neurite outgrowth from Lawsonia inermis flower under non-fasting condition.

    PubMed

    Oda, Yoshimi; Nakashima, Souichi; Nakamura, Seikou; Yano, Mamiko; Akiyama, Masanori; Imai, Kayo; Kimura, Tomohito; Nakata, Akiko; Tani, Miyuki; Matsuda, Hisashi

    2016-07-01

    The methanolic extract of Lawsonia inermis L. (henna) showed accelerative effects on nerve growth factor-induced neurite outgrowth in PC12 cells under non-fasting conditions. To elucidate the active constituents responsible for the neuronal differentiation, we conducted a search of the constituents and examined their accelerative effects on neurite outgrowth in PC12 cells. We isolated a new acetophenone glycoside, inermioside A, which exerted a significant accelerative effect on neurite outgrowth. We also confirmed the activities of nine known compounds, including quercetin and lalioside. In addition, we found that quercetin, one of the active constituents, increased Vav3 mRNA expression.

  7. Genetic Analysis of a Novel Tubulin Mutation That Redirects Synaptic Vesicle Targeting and Causes Neurite Degeneration in C. elegans

    PubMed Central

    Chen, Yen-Chih; McDonald, Kent L.; Gurling, Mark; Lee, Albert; Garriga, Gian; Pan, Chun-Liang

    2014-01-01

    Neuronal cargos are differentially targeted to either axons or dendrites, and this polarized cargo targeting critically depends on the interaction between microtubules and molecular motors. From a forward mutagenesis screen, we identified a gain-of-function mutation in the C. elegans α-tubulin gene mec-12 that triggered synaptic vesicle mistargeting, neurite swelling and neurodegeneration in the touch receptor neurons. This missense mutation replaced an absolutely conserved glycine in the H12 helix with glutamic acid, resulting in increased negative charges at the C-terminus of α-tubulin. Synaptic vesicle mistargeting in the mutant neurons was suppressed by reducing dynein function, suggesting that aberrantly high dynein activity mistargeted synaptic vesicles. We demonstrated that dynein showed preference towards binding mutant microtubules over wild-type in microtubule sedimentation assay. By contrast, neurite swelling and neurodegeneration were independent of dynein and could be ameliorated by genetic paralysis of the animal. This suggests that mutant microtubules render the neurons susceptible to recurrent mechanical stress induced by muscle activity, which is consistent with the observation that microtubule network was disorganized under electron microscopy. Our work provides insights into how microtubule-dynein interaction instructs synaptic vesicle targeting and the importance of microtubule in the maintenance of neuronal structures against constant mechanical stress. PMID:25392990

  8. Genetic analysis of a novel tubulin mutation that redirects synaptic vesicle targeting and causes neurite degeneration in C. elegans.

    PubMed

    Hsu, Jiun-Min; Chen, Chun-Hao; Chen, Yen-Chih; McDonald, Kent L; Gurling, Mark; Lee, Albert; Garriga, Gian; Pan, Chun-Liang

    2014-11-01

    Neuronal cargos are differentially targeted to either axons or dendrites, and this polarized cargo targeting critically depends on the interaction between microtubules and molecular motors. From a forward mutagenesis screen, we identified a gain-of-function mutation in the C. elegans α-tubulin gene mec-12 that triggered synaptic vesicle mistargeting, neurite swelling and neurodegeneration in the touch receptor neurons. This missense mutation replaced an absolutely conserved glycine in the H12 helix with glutamic acid, resulting in increased negative charges at the C-terminus of α-tubulin. Synaptic vesicle mistargeting in the mutant neurons was suppressed by reducing dynein function, suggesting that aberrantly high dynein activity mistargeted synaptic vesicles. We demonstrated that dynein showed preference towards binding mutant microtubules over wild-type in microtubule sedimentation assay. By contrast, neurite swelling and neurodegeneration were independent of dynein and could be ameliorated by genetic paralysis of the animal. This suggests that mutant microtubules render the neurons susceptible to recurrent mechanical stress induced by muscle activity, which is consistent with the observation that microtubule network was disorganized under electron microscopy. Our work provides insights into how microtubule-dynein interaction instructs synaptic vesicle targeting and the importance of microtubule in the maintenance of neuronal structures against constant mechanical stress.

  9. Cable tensioned membrane solar collector module with variable tension control

    DOEpatents

    Murphy, Lawrence M.

    1985-01-01

    Disclosed is a solar collector comprising a membrane for concentrating sunlight, a plurality of elongated structural members for suspending the membrane member thereon, and a plurality of control members for adjustably tensioning the membrane member, as well as for controlling a focus produced by the membrane members. Each control member is disposed at a different corresponding one of the plurality of structural members. The collector also comprises an elongated flexible tensioning member, which serves to stretch the membrane member and to thereafter hold it in tension, and a plurality of sleeve members, which serve to provide the membrane member with a desired surface contour during tensioning of the membrane member. The tensioning member is coupled to the structural members such that the tensioning member is adjustably tensioned through the structural members. The tensioning member is also coupled to the membrane member through the sleeve members such that the sleeve members uniformly and symmetrically stretch the membrane member upon applying tension to the tensioning member with the control members.

  10. Cable tensioned membrane solar collector module with variable tension control

    DOEpatents

    Murphy, L.M.

    1984-01-09

    Disclosed is a solar collector comprising a membrane member for concentrating sunlight, a plurality of elongated structural members for suspending the membrane member thereon, and a plurality of control members for adjustably tensioning the membrane member, as well as for controlling a focus produced by the membrane members. Each control member is disposed at a different corresponding one of the plurality of structural members. The collector also comprises an elongated flexible tensioning member, which serves to stretch the membrane member and to thereafter hold it in tension, and a plurality of sleeve members which serve to provide the membrane member with a desired surface contour during tensioning of the membrane member. The tensioning member is coupled to the structural members such that the tensioning member is adjustably tensioned through the structural members. The tensioning member is also coupled to the membrane member through the sleeve members such that the sleeve members uniformly and symmetrically stretch the membrane member upon applying tension to the tensioning member with the control members.

  11. Dynamic film and interfacial tensions in emulsion and foam systems

    SciTech Connect

    Kim, Y.H.; Koczo, K.; Wasan, D.T.

    1997-03-01

    In concentrated fluid dispersions the liquid films are under dynamic conditions during film rupture or drainage. Aqueous foam films stabilized with sodium decylsulfonate and aqueous emulsion films stabilized with the nonionic Brij 58 surfactant were formed at the tip of a capillary and the film tension was measured under static and dynamic conditions. In the stress relaxation experiments the response of the film tension to a sudden film area expansion was studied. These experiments also allowed the direct measurement of the Gibbs film elasticity. In the dynamic film tension experiments, the film area was continuously increased by a constant rate and the dynamic film tension was monitored. The measured film tensions were compared with the interfacial tensions of the respective single air/water and oil/water interfaces, which were measured using the same radius of curvature, relative expansion, and expansion rate as in the film studies. It was found that under dynamic conditions the film tension is higher than twice the single interfacial tension (IFT) and a mechanism was suggested to explain the difference. When the film, initially at equilibrium, is expanded and the interfacial area increases, a substantial surfactant depletion occurs inside the film. As a result, the surfactant can be supplied only from the adjoining meniscus (Plateau border) by surface diffusion, and the film tension is controlled by the diffusion and adsorption of surfactant in the meniscus. The results have important implications for the stability and rheology of foams and emulsions with high dispersed phase ratios (polyhedral structure).

  12. Epac and the high affinity rolipram binding conformer of PDE4 modulate neurite outgrowth and myelination using an in vitro spinal cord injury model

    PubMed Central

    Boomkamp, S D; McGrath, M A; Houslay, M D; Barnett, S C

    2014-01-01

    Background and Purpose cAMP and pharmacological inhibition of PDE4, which degrades it, are promising therapeutic targets for the treatment of spinal cord injury (SCI). Using our previously described in vitro SCI model, we studied the mechanisms by which cAMP modulators promote neurite outgrowth and myelination using enantiomers of the PDE4-specific inhibitor rolipram and other modulators of downstream signalling effectors. Experimental Approach Rat mixed neural cell myelinating cultures were cut with a scalpel and treated with enantiomers of the PDE4-specific inhibitor rolipram, Epac agonists and PKA antagonists. Neurite outgrowth, density and myelination were assessed by immunocytochemistry and cytokine levels analysed by qPCR. Key Results Inhibition of the high-affinity rolipram-binding state (HARBS), rather than the low-affinity rolipram binding state (LARBS) PDE4 conformer promoted neurite outgrowth and myelination. These effects were mediated through the activation of Epac and not through PKA. Expression of the chemokine CXCL10, known to inhibit myelination, was markedly elevated in astrocytes after Rho inhibition and this was blocked by inhibition of Rho kinase or PDE4. Conclusions and Implications PDE4 inhibitors targeted at the HARBS conformer or Epac agonists may provide promising novel targets for the treatment of SCI. Our study demonstrates the differential mechanisms of action of these compounds, as well as the benefit of a combined pharmacological approach and highlighting potential promising targets for the treatment of SCI. These findings need to be confirmed in vivo. PMID:24467222

  13. NGF induces the expression of group IIA secretory phospholipase A2 in PC12 cells: the newly synthesized enzyme is addressed to growing neurites.

    PubMed

    Nardicchi, Vincenza; Ferrini, Monica; Pilolli, Francesca; Angeli, Emanuela Biagioni; Persichetti, Emanuele; Beccari, Tommaso; Mannucci, Roberta; Arcuri, Cataldo; Donato, Rosario; Dorman, Robert V; Goracci, Gianfrancesco

    2014-08-01

    We proposed that group IIA secretory phospholipase A(2) (GIIA) participates in neuritogenesis based on our observations that the enzyme migrates to growth cones and neurite tips when PC12 cells are induced to differentiate by nerve growth factor (NGF) (Ferrini et al., Neurochem Res 35:2168-2174, 2010). The involvement of other secretory PLA(2) isoforms in neuronal development has been suggested by others but through different mechanisms. In the present study, we compared the subcellular distribution of GIIA and group X sPLA(2) (GX) after stimulation of PC12 cells with NGF. We found that GIIA, but not GX, localized at the neuritic tips after treatment with NGF, as demonstrated by immunofluorescence analysis. We also found that NGF stimulated the expression and the activity of GIIA. In addition, NGF induced the expressed myc-tagged GIIA protein to migrate to neurite tips in its active form. We propose that GIIA expression, activity, and subcellular localization is regulated by NGF and that the enzyme may participate in neuritogenesis through intracellular mechanisms, most likely by facilitating the remodelling of glycerophospholipid molecular species by deacylation-reacylation reactions necessary for the incorporation of polyunsaturated fatty acids.

  14. Plasminogen activator inhibitor-1 aids survival of neurites on neurons derived from pheochromocytoma (PC-12) cells.

    PubMed

    Soeda, Shinji; Imatoh, Takuya; Ochiai, Takashi; Koyanagi, Satoru; Shimeno, Hiroshi

    2004-04-09

    Plasminogen activator inhibitor-1 is a serpin that regulates the activities of plasminogen activators. However, its physiological roles in the CNS are incompletely understood. We have found that plasminogen activator inhibitor-1 has a novel biological function in the CNS: the contribution to survival of neurites on neurons. PC-12 cells treated with nerve growth factor differentiated into neurons and formed a network of neurites. In a serum-free culture medium, these neurites disappeared within 24 h. The addition of plasminogen activator inhibitor-1 prevented the disintegration of the neuronal networks, while the addition of the serpin inhibitors aprotinin and antipain did not. The plasminogen activator inhibitor-1 maintained or promoted the phosphorylated state of extracellular signal-regulated kinase (ERK), but not of protein kinase B (Akt). These results are the first evidence that plasminogen activator inhibitor-1 in the CNS acts to maintain the morphology of neurites via activation of the ERK-related pathway in the neurons.

  15. ANALYSIS OF THE STRUCTURE OF MAGNETIC FIELDS THAT INDUCED INHIBITION OF STIMULATED NEURITE OUTGROWTH

    EPA Science Inventory

    The important experiments showing nonlinear amplitude dependences of the neurite outgrowth in pheochromocytoma nerve cells due to ELF magnetic field exposure had been carried out in a nonuniform ac magnetic field. The nonuniformity entailed larger than expected variances in magne...

  16. ROCK inhibition enhances neurite outgrowth in neural stem cells by upregulating YAP expression in vitro

    PubMed Central

    Jia, Xu-feng; Ye, Fei; Wang, Yan-bo; Feng, Da-xiong

    2016-01-01

    Spontaneous axonal regeneration of neurons does not occur after spinal cord injury because of inhibition by myelin and other inhibitory factors. Studies have demonstrated that blocking the Rho/Rho-kinase (ROCK) pathway can promote neurite outgrowth in spinal cord injury models. In the present study, we investigated neurite outgrowth and neuronal differentiation in neural stem cells from the mouse subventricular zone after inhibition of ROCK in vitro. Inhibition of ROCK with Y-27632 increased neurite length, enhanced neuronal differentiation, and upregulated the expression of two major signaling pathway effectors, phospho-Akt and phospho-mitogen-activated protein kinase, and the Hippo pathway effector YAP. These results suggest that inhibition of ROCK mediates neurite outgrowth in neural stem cells by activating the Hippo signaling pathway. PMID:27482229

  17. ANALYSIS OF THE STRUCTURE OF MAGNETIC FIELDS THAT INDUCED INHIBITION OF STIMULATED NEURITE OUTGROWTH

    EPA Science Inventory

    The important experiments showing nonlinear amplitude dependences of the neurite outgrowth in pheochromocytoma nerve cells due to ELF magnetic field exposure had been carried out in a nonuniform ac magnetic field. The nonuniformity entailed larger than expected variances in magne...

  18. Regulation of Cellular Tension in Adherent Cells

    NASA Astrophysics Data System (ADS)

    Oakes, Patrick

    2013-03-01

    Cells generate stress on their surrounding extracellular matrix (ECM) via myosin II motor generated forces which are transmitted through the actin cytoskeleton. The mechanisms in the cell which regulate the magnitude and spatial distribution of these stresses, however, remain unknown. Consistent with previous reports, we find that the total magnitude of traction force exerted on the ECM scales with cell size. Such scaling is observed across numerous cell types and reflects an inherent cellular tension determined by the level of myosin II activity. Surprisingly, while stiffness modulates the cellular spread area, we find this scaling relationship to be independent of ECM stiffness. To identify the biophysical mechanisms regulating the generation of tension, we utilize micro-patterning to isolate cell spread area from cell geometry and to spatially control the distribution of stress on the ECM. We find that traction stress magnitude is dependent on the local curvature of the cell. Changes in cell geometry result in a redistribution of local stresses, but little change in the total stress applied to the ECM. Finally, for a constant geometry, we find that both the total stress and the average stress exerted on the ECM increase with cell area. Together these data suggest that the cell can be modeled as a uniformly contracting mesh, where the magnitude of tension is regulated by the cell spread area, and the distribution of tension is regulated by local geometry.

  19. Coulomb string tension, asymptotic string tension, and the gluon chain

    SciTech Connect

    Greensite, Jeff; Szczepaniak, Adam P.

    2015-02-01

    We compute, via numerical simulations, the non-perturbative Coulomb potential and position-space ghost propagator in pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

  20. Coulomb string tension, asymptotic string tension, and the gluon chain

    DOE PAGES

    Greensite, Jeff; Szczepaniak, Adam P.

    2015-02-01

    We compute, via numerical simulations, the non-perturbative Coulomb potential and position-space ghost propagator in pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

  1. Tension in Cancer

    PubMed Central

    Löffek, Stefanie; Franzke, Claus-Werner; Helfrich, Iris

    2016-01-01

    Integrins represent a large family of cell receptors that mediate adhesion to the extracellular matrix (ECM), thereby modulating a variety of cellular functions that are required for proliferation, migration, malignant conversion and invasiveness. During tumorigenesis the conversion of a tumor cell from sessile, stationary phenotype to an invasive phenotype requires the ability of tumor cells to interact with their environment in order to transduce signals from the ECM into the cells. Hence, there is increasing evidence that changes in the composition, topography and tension of tumor matrix can be sensed by integrin receptors, leading to the regulation of intracellular signalling events which subsequently help to fuel cancer progression. The fact that intracellular signals perceived from integrin ligand binding impact on almost all steps of tumor progression, including tumor cell proliferation, survival, metastatic dissemination and colonization of a metastatic niche, renders integrins as ideal candidates for the development of therapeutic agents. In this review we summarize the role of integrins in cancer with the special focus on cancer therapies and the recent progress that has been made in the understanding of “integrin-induced tension in cancer”. Finally, we conclude with clinical evidence for the role of integrin-mediated mechanotransduction in the development of therapy-resistant tumors. PMID:27854331

  2. Separation anxiety: Stress, tension and cytokinesis

    SciTech Connect

    Mohan, Krithika; Iglesias, Pablo A.; Robinson, Douglas N.

    2012-07-15

    Cytokinesis, the physical separation of a mother cell into two daughter cells, progresses through a series of well-defined changes in morphology. These changes involve distinct biochemical and mechanical processes. Here, we review the mechanical features of cells during cytokinesis, discussing both the material properties as well as sources of stresses, both active and passive, which lead to the observed changes in morphology. We also describe a mechanosensory feedback control system that regulates protein localization and shape progression during cytokinesis. -- Highlights: Black-Right-Pointing-Pointer Cytokinesis progresses through three distinct mechanical phases. Black-Right-Pointing-Pointer Cortical tension initially resists deformation of mother cell. Black-Right-Pointing-Pointer Late in cytokinesis, cortical tension provides stress, enabling furrow ingression. Black-Right-Pointing-Pointer A mechanosensory feedback control system regulates cytokinesis.

  3. Design of 3D engineered protein hydrogels for tailored control of neurite growth

    PubMed Central

    Lampe, Kyle J.; Antaris, Alexander L.; Heilshorn, Sarah C.

    2013-01-01

    The design of bioactive materials allows for tailored studies probing cell-biomaterial interactions; however, relatively few studies have examined effects of ligand density and material stiffness on neurite growth in 3D. Elastin-like proteins (ELPs) have been designed with modular bioactive and structural regions to enable the systematic characterization of design parameters within 3D materials. To promote neurite outgrowth and better understand the effects of common biomaterial design parameters on neuronal cultures, we here focused on cell-adhesive ligand density and hydrogel stiffness as design variables for ELP hydrogels. With the inherent design freedom of engineered proteins, these 3D ELP hydrogels enabled decoupled investigation into the effects of biomechanics and biochemistry on neurite outgrowth from dorsal root ganglia (DRG). Increasing the cell-adhesive RGD ligand density from 0 to 1.9 × 107 ligands/μm3 led to a significant increase in the rate, length, and density of neurite outgrowth, as quantified by a high-throughput algorithm developed for dense neurite analysis. An approximately two-fold improvement in total neurite outgrowth was observed in materials with the higher ligand density at all time-points through 7 days. ELP hydrogels with initial elastic moduli of 0.5, 1.5, or 2.1 kPa and identical RGD ligand densities revealed that the most compliant materials led to the greatest outgrowth, with some neurites extending over 1800 μm by day 7. Given the ability of ELP hydrogels to efficiently promote neurite outgrowth within defined and tunable 3D microenvironments, these materials may be useful in developing therapeutic nerve guides and the further study of basic neuron-biomaterial interactions. PMID:23128159

  4. Effects of serum, tissue extract, conditioned medium, and culture substrata on neurite appearance from spinal cord explants of chick embryo.

    PubMed

    Tanaka, H; Sakai, M; Obata, K

    1982-07-01

    The effects of serum, tissue extracts, conditioned medium, (CM), and culture substrata on neurite appearance from spinal cord explants of 6- to 8-day-old chick embryos were investigated. In Eagle's minimum essential medium (MEM) with no supplement neurites from explants did not appear on collagen coating but on polyornithine coating (PORN). It is concluded that cell-to-substratum interaction is important in neurite appearance. CM, serum and tissue extract potentiated neurite appearance, but their activities were highly dependent on the coating. The amount of collagen was also crucial. On collagen, neurite appearance was observed only when promoting substances were present. CM and serum contained at least two components; one affected neurite appearance after deposition on collagen and the other affected neurite appearance when present in the culture medium. The former was included also in tissue extracts. Both of adsorbable and non-adsorbable components from any origin were necessary for effective induction of neurite appearance. Heat treatment and dialysis differentiated these active components. On PORN, CM highly potentiated neurite appearance. The activity of the CM was reproduced by its low molecular weight fraction. Serum also promoted neurite appearance, but to a lesser extent than CM. The effect of tissue extract was not remarkable.

  5. Soluble cpg15 from Astrocytes Ameliorates Neurite Outgrowth Recovery of Hippocampal Neurons after Mouse Cerebral Ischemia.

    PubMed

    Zhao, Jing-Jing; Hu, Jie-Xian; Lu, De-Xin; Ji, Chun-Xia; Qi, Yao; Liu, Xiao-Yan; Sun, Feng-Yan; Huang, Fang; Xu, Ping; Chen, Xian-Hua

    2017-02-08

    The present study focuses on the function of cpg15, a neurotrophic factor, in ischemic neuronal recovery using transient global cerebral ischemic (TGI) mouse model and oxygen-glucose deprivation (OGD)-treated primary cultured cells. The results showed that expression of cpg15 proteins in astrocytes, predominantly the soluble form, was significantly increased in mouse hippocampus after TGI and in the cultured astrocytes after OGD. Addition of the medium from the cpg15-overexpressed astrocytic culture into the OGD-treated hippocampal neuronal cultures reduces the neuronal injury, whereas the recovery of neurite outgrowths of OGD-injured neurons was prevented when cpg15 in the OGD-treated astrocytes was knocked down, or the OGD-treated-astrocytic medium was immunoadsorbed by cpg15 antibody. Furthermore, lentivirus-delivered knockdown of cpg15 expression in mouse hippocampal astrocytes diminishes the dendritic branches and exacerbates injury of neurons in CA1 region after TGI. In addition, treatment with inhibitors of MEK1/2, PI3K, and TrkA decreases, whereas overexpression of p-CREB, but not dp-CREB, increases the expression of cpg15 in U118 or primary cultured astrocytes. Also, it is observed that the Flag-tagged soluble cpg15 from the astrocytes transfected with Flag-tagged cpg15-expressing plasmids adheres to the surface of neuronal bodies and the neurites. In conclusion, our results suggest that the soluble cpg15 from astrocytes induced by ischemia could ameliorate the recovery of the ischemic-injured hippocampal neurons via adhering to the surface of neurons. The upregulated expression of cpg15 in astrocytes may be activated via MAPK and PI3K signal pathways, and regulation of CREB phosphorylation.SIGNIFICANCE STATEMENT Neuronal plasticity plays a crucial role in the amelioration of neurological recovery of ischemic injured brain, which remains a challenge for clinic treatment of cerebral ischemia. cpg15 as a synaptic plasticity-related factor may participate in

  6. VANG-1 and PRKL-1 Cooperate to Negatively Regulate Neurite Formation in Caenorhabditis elegans

    PubMed Central

    Su, Anna; Imai, Janice H.; Colavita, Antonio

    2011-01-01

    Neuritogenesis is a critical early step in the development and maturation of neurons and neuronal circuits. While extracellular directional cues are known to specify the site and orientation of nascent neurite formation in vivo, little is known about the genetic pathways that block inappropriate neurite emergence in order to maintain proper neuronal polarity. Here we report that the Caenorhabditis elegans orthologues of Van Gogh (vang-1), Prickle (prkl-1), and Dishevelled (dsh-1), core components of planar cell polarity (PCP) signaling, are required in a subset of peripheral motor neurons to restrict neurite emergence to a specific organ axis. In loss-of-function mutants, neurons display supernumerary neurites that extend inappropriately along the orthogonal anteroposterior (A/P) body axis. We show that autonomous and non-autonomous gene activities are required early and persistently to inhibit the formation or consolidation of growth cone protrusions directed away from organ precursor cells. Furthermore, prkl-1 overexpression is sufficient to suppress neurite formation and reorient neuronal polarity in a vang-1– and dsh-1–dependent manner. Our findings suggest a novel role for a PCP–like pathway in maintaining polarized neuronal morphology by inhibiting neuronal responses to extrinsic or intrinsic cues that would otherwise promote extraneous neurite formation. PMID:21912529

  7. Survival and neurite growth of chick embryo spinal cord cells in serum-free culture.

    PubMed

    Tanaka, H; Obata, K

    1982-07-01

    Cell survival and neurite growth were investigated in serum-free spinal cord cell cultures on polyornithine coating (PORN). Cells were obtained from 6- or 7-day-old chick embryos. Isolated spinal cord cells required promoting factors for their survival and neurite growth. The survival-promoting factors were initially present in spinal cord cells. High density cultures, co-cultures with spinal cord explants, and spinal cord extract promoted survival of isolated spinal cord cells in MEM with no additives. Other tissue extracts (brain, liver, heart and skeletal muscle), serum, and serum-free conditioned medium (SF-CM) of muscle or glioma C6 cells also promoted survival. The active substances in the brain extract and SF-CM were shown to be protein and were separated into 3 fractions (approximately molecular weight 150,000, 70,000, 40,000) by gel filtration chromatography. Survival and neurite growth were suggested to be promoted by different factors because: (1) survival was promoted by both tissue extract and SF-CM, but neurite growth was promoted only by SF-CM; (2) the neurite growth-stimulating activity of SF-CM was lost following dialysis and heat (100 degrees C, 2 min) treatment; however, the survival-promoting activity was not. It was also suggested that spinal cord cells produce neurite growth promoting factors, but did not initially contain these factors.

  8. Sigma-1 receptor enhances neurite elongation of cerebellar granule neurons via TrkB signaling.

    PubMed

    Kimura, Yuriko; Fujita, Yuki; Shibata, Kumi; Mori, Megumi; Yamashita, Toshihide

    2013-01-01

    Sigma-1 receptor (Sig-1R) is an integral membrane protein predominantly expressed in the endoplasmic reticulum. Sig-1R demonstrates a high affinity to various synthetic compounds including well-known psychotherapeutic drugs in the central nervous system (CNS). For that, it is considered as an alternative target for psychotherapeutic drugs. On the cellular level, when Sig-1R is activated, it is known to play a role in neuroprotection and neurite elongation. These effects are suggested to be mediated by its ligand-operated molecular chaperone activity, and/or upregulation of various Ca(2+) signaling. In addition, recent studies show that Sig-1R activation induces neurite outgrowth via neurotrophin signaling. Here, we tested the hypothesis that Sig-1R activation promotes neurite elongation through activation of tropomyosin receptor kinase (Trk), a family of neurotrophin receptors. We found that 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate (PRE-084), a selective Sig-1R agonist, significantly promoted neurite outgrowth, and K252a, a Trk inhibitor, attenuated Sig-1R-mediated neurite elongation in cerebellar granule neurons (CGNs). Moreover, we revealed that Sig-1R interacts with TrkB, and PRE-084 treatment enhances phosphorylation of Y515, but not Y706. Thus, our results indicate that Sig-1R activation promotes neurite outgrowth in CGNs through Y515 phosphorylation of TrkB.

  9. MorphoNeuroNet: an automated method for dense neurite network analysis.

    PubMed

    Pani, Giuseppe; De Vos, Winnok H; Samari, Nada; de Saint-Georges, Louis; Baatout, Sarah; Van Oostveldt, Patrick; Benotmane, Mohammed Abderrafi

    2014-02-01

    High content cell-based screens are rapidly gaining popularity in the context of neuronal regeneration studies. To analyze neuronal morphology, automatic image analysis pipelines have been conceived, which accurately quantify the shape changes of neurons in cell cultures with non-dense neurite networks. However, most existing methods show poor performance for well-connected and differentiated neuronal networks, which may serve as valuable models for inter alia synaptogenesis. Here, we present a fully automated method for quantifying the morphology of neurons and the density of neurite networks, in dense neuronal cultures, which are grown for more than 10 days. MorphoNeuroNet, written as a script for ImageJ, Java based freeware, automatically determines various morphological parameters of the soma and the neurites (size, shape, starting points, and fractional occupation). The image analysis pipeline consists of a multi-tier approach in which the somas are segmented by adaptive region growing using nuclei as seeds, and the neurites are delineated by a combination of various intensity and edge detection algorithms. Quantitative comparison showed a superior performance of MorphoNeuroNet to existing analysis tools, especially for revealing subtle changes in thin neurites, which have weak fluorescence intensity compared to the rest of the network. The proposed method will help determining the effects of compounds on cultures with dense neurite networks, thereby boosting physiological relevance of cell-based assays in the context of neuronal diseases. © 2013 International Society for Advancement of Cytometry.

  10. Bifenthrin causes neurite retraction in the absence of cell death: a model for pesticide associated neurodegeneration.

    PubMed

    Nandi, Avishek; Chandil, Daljit; Lechesal, Rethabile; Pryor, Stephen C; McLaughlin, Ashlea; Bonventre, Josephine A; Flynnx, Katherine; Weeks, Benjamin S

    2006-05-01

    Bifenthrin is a synthetic pyrethroid insecticide derivative of naturally occurring pyrethrins from chrysanthemum flowers. Bifenthrin is considered relatively safe and therefore incorporated as the active ingredient in preparations sold over the counter for household use. Recent studies have raised concern that chronic exposure to pesticides in the home setting may increase the risk for neurodegenerative diseases. To address this concer, in the present study, bifenthrin is added to pre-differentiated PC12 and effect of bifenthrin on the retraction of existing neurites is observed a model for neurodegeneration. PC12 cells were differentiated with nerve growth factor for twenty-four hours and then treated with what was determined to be a sublethal dose of bifenthrin for up to an additional 48 hours. The percent of cells with neurites was assessed at various times before and after nerve growth factor treatment. Bifenthrin toxicity was determined using trypan blue exclusion. Bifenthrin was not toxic to PC12 cells at concentrations ranging from 1 x 10(-10) M to 1 x 10(-4) M. Twenty-four hours after nerve growth factor treatment, a maximum percent of cells had formed neurites and with a treatment of 1 x 10(-5) M bifenthrin, approximately 80% of these neurites retracted in within 12 additional hours and almost all neurites had retracted within 48 hours. Trypan exclusion showed that these cells were viable. These data show that bifenthrin can stimulate the retraction of neurites in the absence of frank toxicity.

  11. Oxytocin Increases Neurite Length and Expression of Cytoskeletal Proteins Associated with Neuronal Growth.

    PubMed

    Lestanova, Z; Bacova, Z; Kiss, A; Havranek, T; Strbak, V; Bakos, J

    2016-06-01

    Neuropeptide oxytocin acts as a growth and differentiation factor; however, its effects on neurite growth are poorly understood. The aims of the present study were (1) to evaluate time effects of oxytocin on expression of nestin and MAP2; (2) to measure the effect of oxytocin on gene expression of β-actin, vimentin, cofilin, and drebrin; and (3) to measure changes in neurite length and number in response to oxytocin/oxytocin receptor antagonist L-371,257. Exposure of SH-SY5Y cells to 1 μM oxytocin resulted in a significant increase in gene expression and protein levels of nestin after 12, 24, and 48 h. Oxytocin treatment induced no changes in gene expression of MAP2; however, a decrease of protein levels was observed in all time intervals. Gene expression of β-actin, vimentin, and drebrin increased in response to oxytocin. Oxytocin induced significant elongation of neurites after 12, 24, and 48 h. No change in neurite length was observed in the presence of the combination of retinoic acid and oxytocin receptor antagonist L-371,257. Oxytocin treatment for 12 h increased the number of neurites. Overall, the present data suggest that oxytocin contributes to the regulation of expression of cytoskeletal proteins associated with growth of neuronal cones and induces neurite elongation mediated by oxytocin receptors at least in certain types of neuronal cells.

  12. Neurite outgrowth in cultured mouse pelvic ganglia - Effects of neurotrophins and bladder tissue.

    PubMed

    Ekman, Mari; Zhu, Baoyi; Swärd, Karl; Uvelius, Bengt

    2017-07-01

    Neurotrophic factors regulate survival and growth of neurons. The urinary bladder is innervated via both sympathetic and parasympathetic neurons located in the major pelvic ganglion. The aim of the present study was to characterize the effects of the neurotrophins nerve growth factor (NGF), brain derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) on the sprouting rate of sympathetic and parasympathetic neurites from the female mouse ganglion. The pelvic ganglion was dissected out and attached to a petri dish and cultured in vitro. All three factors (BDNF, NT-3 and NGF) stimulated neurite outgrowth of both sympathetic and parasympathetic neurites although BDNF and NT-3 had a higher stimulatory effect on parasympathetic ganglion cells. The neurotrophin receptors TrkA, TrkB and TrkC were all expressed in neurons of the ganglia. Co-culture of ganglia with urinary bladder tissue, but not diaphragm tissue, increased the sprouting rate of neurites. Active forms of BDNF and NT-3 were detected in urinary bladder tissue using western blotting whereas tissue from the diaphragm expressed NGF. Neurite outgrowth from the pelvic ganglion was inhibited by a TrkB receptor antagonist. We therefore suggest that the urinary bladder releases trophic factors, including BDNF and NT-3, which regulate neurite outgrowth via activation of neuronal Trk-receptors. These findings could influence future strategies for developing pharmaceuticals to improve re-innervation due to bladder pathologies. Copyright © 2017. Published by Elsevier B.V.

  13. Sigma-1 Receptor Enhances Neurite Elongation of Cerebellar Granule Neurons via TrkB Signaling

    PubMed Central

    Kimura, Yuriko; Fujita, Yuki; Shibata, Kumi; Mori, Megumi; Yamashita, Toshihide

    2013-01-01

    Sigma-1 receptor (Sig-1R) is an integral membrane protein predominantly expressed in the endoplasmic reticulum. Sig-1R demonstrates a high affinity to various synthetic compounds including well-known psychotherapeutic drugs in the central nervous system (CNS). For that, it is considered as an alternative target for psychotherapeutic drugs. On the cellular level, when Sig-1R is activated, it is known to play a role in neuroprotection and neurite elongation. These effects are suggested to be mediated by its ligand-operated molecular chaperone activity, and/or upregulation of various Ca2+ signaling. In addition, recent studies show that Sig-1R activation induces neurite outgrowth via neurotrophin signaling. Here, we tested the hypothesis that Sig-1R activation promotes neurite elongation through activation of tropomyosin receptor kinase (Trk), a family of neurotrophin receptors. We found that 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate (PRE-084), a selective Sig-1R agonist, significantly promoted neurite outgrowth, and K252a, a Trk inhibitor, attenuated Sig-1R-mediated neurite elongation in cerebellar granule neurons (CGNs). Moreover, we revealed that Sig-1R interacts with TrkB, and PRE-084 treatment enhances phosphorylation of Y515, but not Y706. Thus, our results indicate that Sig-1R activation promotes neurite outgrowth in CGNs through Y515 phosphorylation of TrkB. PMID:24116072

  14. Sensitivity of Neural Stem Cell Survival, Differentiation and Neurite Outgrowth within 3D Hydrogels to Environmental Heavy Metals

    PubMed Central

    Tasneem, Sameera; Farrell, Kurt; Lee, Moo-Yeal; Kothapalli, Chandrasekhar R.

    2015-01-01

    We investigated the sensitivity of embryonic murine neural stem cells exposed to 10 pM – 10 μM concentrations of three heavy metals (Cd, Hg, Pb), continuously for 14 days within 3D collagen hydrogels. Critical endpoints for neurogenesis such as survival, differentiation and neurite outgrowth were assessed. Results suggest significant compromise in cell viability within the first four days at concentrations ≥ 10 nM, while lower concentrations induced a more delayed effect. Mercury and lead suppressed neural differentiation at as low as 10 pM concentration within 7 days, while all three metals inhibited neural and glial differentiation by day 14. Neurite outgrowth remained unaffected at lower cadmium or mercury concentrations (≤ 100 pM), but was completely repressed beyond day 1 at higher concentrations. Higher metal concentrations (≥ 100 pM) suppressed NSC differentiation to motor or dopaminergic neurons. Cytokines and chemokines released by NSCs, and the sub-cellular mechanisms by which metals induce damage to NSCs have been quantified and correlated to phenotypic data. The observed degree of toxicity in NSC cultures is in the order: lead > mercury > cadmium. Results point to the use of biomimetic 3D culture models to screen the toxic effects of heavy metals during developmental stages, and investigate their underlying mechanistic pathways. PMID:26621541

  15. Controlled release of 6-aminonicotinamide from aligned, electrospun fibers alters astrocyte metabolism and dorsal root ganglia neurite outgrowth

    NASA Astrophysics Data System (ADS)

    Schaub, Nicholas J.; Gilbert, Ryan J.

    2011-08-01

    Following central nervous system (CNS) injury, activated astrocytes form a glial scar that inhibits the migration of axons ultimately leading to regeneration failure. Biomaterials developed for CNS repair can provide local delivery of therapeutics and/or guidance mechanisms to encourage cell migration into damaged regions of the brain or spinal cord. Electrospun fibers are a promising type of biomaterial for CNS injury since these fibers can direct cellular and axonal migration while slowly delivering therapy to the injury site. In this study, it was hypothesized that inclusion of an anti-metabolite, 6-aminonicotinamide (6AN), within poly-l-lactic acid electrospun fibers could attenuate astrocyte metabolic activity while still directing axonal outgrowth. Electrospinning parameters were varied to produce highly aligned electrospun fibers that contained 10% or 20% (w/w) 6AN. 6AN release from the fiber substrates occurred continuously over 2 weeks. Astrocytes placed onto drug-releasing fibers were less active than those cultured on scaffolds without 6AN. Dorsal root ganglia placed onto control and drug-releasing scaffolds were able to direct neurites along the aligned fibers. However, neurite outgrowth was stunted by fibers that contained 20% 6AN. These results show that 6AN release from aligned, electrospun fibers can decrease astrocyte activity while still directing axonal outgrowth.

  16. A novel role for PTEN in the inhibition of neurite outgrowth by Myelin-associated glycoprotein in cortical neurons

    PubMed Central

    Perdigoto, Ana Luisa; Chaudhry, Nagarathnamma; Barnes, Gregory N.; Filbin, Marie T.; Carter, Bruce D.

    2010-01-01

    Axonal regeneration in the central nervous system is prevented, in part, by inhibitory proteins expressed by myelin, including Myelin-associated glycoprotein (MAG). Although injury to the corticospinal tract can result in permanent disability, little is known regarding the mechanisms by which MAG affects cortical neurons. Here, we demonstrate that cortical neurons plated on MAG expressing CHO cells, exhibit a striking reduction in process outgrowth. Interestingly, none of the receptors previously implicated in MAG signaling, including the p75 neurotrophin receptor or gangliosides, contributed significantly to MAG-mediated inhibition. However, blocking the small GTPase Rho or its downstream effector kinase, ROCK, partially reversed the effects of MAG on the neurons. In addition, we identified the lipid phosphatase PTEN as a mediator of MAG’s inhibitory effects on neurite outgrowth. Knockdown or gene deletion of PTEN or over expression of activated AKT in cortical neurons resulted in significant, although partial, rescue of neurite outgrowth on MAG-CHO cells. Moreover, MAG decreased the levels of phospho-Akt, suggesting that it activates PTEN in the neurons. Taken together, these results suggest a novel pathway activated by MAG in cortical neurons involving the PTEN/PI3K/AKT axis. PMID:20869442

  17. Sonic hedgehog promotes neurite outgrowth of cortical neurons under oxidative stress: Involving of mitochondria and energy metabolism.

    PubMed

    He, Weiliang; Cui, Lili; Zhang, Cong; Zhang, Xiangjian; He, Junna; Xie, Yanzhao; Chen, Yanxia

    2017-01-01

    Oxidative stress has been demonstrated to be involved in the etiology of several neurobiological disorders. Sonic hedgehog (Shh), a secreted glycoprotein factor, has been implicated in promoting several aspects of brain remodeling process. Mitochondria may play an important role in controlling fundamental processes in neuroplasticity. However, little evidence is available about the effect and the potential mechanism of Shh on neurite outgrowth in primary cortical neurons under oxidative stress. Here, we revealed that Shh treatment significantly increased the viability of cortical neurons in a dose-dependent manner, which was damaged by hydrogen peroxide (H2O2). Shh alleviated the apoptosis rate of H2O2-induced neurons. Shh also increased neuritogenesis injuried by H2O2 in primary cortical neurons. Moreover, Shh reduced the generation of reactive oxygen species (ROS), increased the activities of SOD and and decreased the productions of MDA. In addition, Shh protected mitochondrial functions, elevated the cellular ATP levels and amelioratesd the impairment of mitochondrial complex II activities of cortical neurons induced by H2O2. In conclusion, all these results suggest that Shh acts as a prosurvival factor playing an essential role to neurite outgrowth of cortical neuron under H2O2 -induced oxidative stress, possibly through counteracting ROS release and preventing mitochondrial dysfunction and ATP as well as mitochondrial complex II activities against oxidative stress.

  18. Sensitivity of neural stem cell survival, differentiation and neurite outgrowth within 3D hydrogels to environmental heavy metals.

    PubMed

    Tasneem, Sameera; Farrell, Kurt; Lee, Moo-Yeal; Kothapalli, Chandrasekhar R

    2016-02-03

    We investigated the sensitivity of embryonic murine neural stem cells exposed to 10 pM-10 μM concentrations of three heavy metals (Cd, Hg, Pb), continuously for 14 days within 3D collagen hydrogels. Critical endpoints for neurogenesis such as survival, differentiation and neurite outgrowth were assessed. Results suggest significant compromise in cell viability within the first four days at concentrations ≥10 nM, while lower concentrations induced a more delayed effect. Mercury and lead suppressed neural differentiation at as low as 10 pM concentration within 7 days, while all three metals inhibited neural and glial differentiation by day 14. Neurite outgrowth remained unaffected at lower cadmium or mercury concentrations (≤100 pM), but was completely repressed beyond day 1 at higher concentrations. Higher metal concentrations (≥100 pM) suppressed NSC differentiation to motor or dopaminergic neurons. Cytokines and chemokines released by NSCs, and the sub-cellular mechanisms by which metals induce damage to NSCs have been quantified and correlated to phenotypic data. The observed degree of toxicity in NSC cultures is in the order: lead>mercury>cadmium. Results point to the use of biomimetic 3D culture models to screen the toxic effects of heavy metals during developmental stages, and investigate their underlying mechanistic pathways.

  19. [Polypragmasy in chronic tension headache?].

    PubMed

    Aull, S; Maly, J; Mraz, M; Schnider, P; Travniczek, A; Zeiler, K; Wessely, P

    1994-01-01

    The various forms of treatment (drugs as well as non-drug therapy) of patients suffering from tension type headache are presented. Analgesics and non-steroidal antirheumatics are used in the management of episodic tension type headache, as well as acute exacerbation of chronic tension type headache. In view of the presumably multifactorial pathogenesis, a multidimensional therapeutic approach is required in patients with chronic tension type headache. Antidepressive drugs (thymoleptics) are usually prescribed as basic therapy. Additional implementation of non-drug therapeutic measures tailored to individual symptomatology is advisable, such as EMG biofeedback, other relaxation techniques, massage, physiotherapy and--in selected cases--psychotherapy or acupuncture.

  20. Neuritic regeneration and synaptic reconstruction induced by withanolide A

    PubMed Central

    Kuboyama, Tomoharu; Tohda, Chihiro; Komatsu, Katsuko

    2005-01-01

    We investigated whether withanolide A (WL-A), isolated from the Indian herbal drug Ashwagandha (root of Withania somnifera), could regenerate neurites and reconstruct synapses in severely damaged neurons. We also investigated the effect of WL-A on memory-deficient mice showing neuronal atrophy and synaptic loss in the brain. Axons, dendrites, presynapses, and postsynapses were visualized by immunostaining for phosphorylated neurofilament-H (NF-H), microtubule-associated protein 2 (MAP2), synaptophysin, and postsynaptic density-95 (PSD-95), respectively. Treatment with Aβ(25–35) (10 μM) induced axonal and dendritic atrophy, and pre- and postsynaptic loss in cultured rat cortical neurons. Subsequent treatment with WL-A (1 μM) induced significant regeneration of both axons and dendrites, in addition to the reconstruction of pre- and postsynapses in the neurons. WL-A (10 μmol kg−1 day−1, for 13 days, p.o.) recovered Aβ(25–35)-induced memory deficit in mice. At that time, the decline of axons, dendrites, and synapses in the cerebral cortex and hippocampus was almost recovered. WL-A is therefore an important candidate for the therapeutic treatment of neurodegenerative diseases, as it is able to reconstruct neuronal networks. PMID:15711595

  1. Fragmentation in Biaxial Tension

    SciTech Connect

    Campbell, G H; Archbold, G C; Hurricane, O A; Miller, P L

    2006-06-13

    We have carried out an experiment that places a ductile stainless steel in a state of biaxial tension at a high rate of strain. The loading of the ductile metal spherical cap is performed by the detonation of a high explosive layer with a conforming geometry to expand the metal radially outwards. Simulations of the loading and expansion of the metal predict strain rates that compare well with experimental observations. A high percentage of the HE loaded material was recovered through a soft capture process and characterization of the recovered fragments provided high quality data, including uniform strain prior to failure and fragment size. These data were used with a modified fragmentation model to determine a fragmentation energy.

  2. Tension stimulation drives tissue formation in scaffold-free systems

    NASA Astrophysics Data System (ADS)

    Lee, Jennifer K.; Huwe, Le W.; Paschos, Nikolaos; Aryaei, Ashkan; Gegg, Courtney A.; Hu, Jerry C.; Athanasiou, Kyriacos A.

    2017-08-01

    Scaffold-free systems have emerged as viable approaches for engineering load-bearing tissues. However, the tensile properties of engineered tissues have remained far below the values for native tissue. Here, by using self-assembled articular cartilage as a model to examine the effects of intermittent and continuous tension stimulation on tissue formation, we show that the application of tension alone, or in combination with matrix remodelling and synthesis agents, leads to neocartilage with tensile properties approaching those of native tissue. Implantation of tension-stimulated tissues results in neotissues that are morphologically reminiscent of native cartilage. We also show that tension stimulation can be translated to a human cell source to generate anisotropic human neocartilage with enhanced tensile properties. Tension stimulation, which results in nearly sixfold improvements in tensile properties over unstimulated controls, may allow the engineering of mechanically robust biological replacements of native tissue.

  3. Membrane tension controls the assembly of curvature-generating proteins

    NASA Astrophysics Data System (ADS)

    Simunovic, Mijo; Voth, Gregory A.

    2015-05-01

    Proteins containing a Bin/Amphiphysin/Rvs (BAR) domain regulate membrane curvature in the cell. Recent simulations have revealed that BAR proteins assemble into linear aggregates, strongly affecting membrane curvature and its in-plane stress profile. Here, we explore the opposite question: do mechanical properties of the membrane impact protein association? By using coarse-grained molecular dynamics simulations, we show that increased surface tension significantly impacts the dynamics of protein assembly. While tensionless membranes promote a rapid formation of long-living linear aggregates of N-BAR proteins, increase in tension alters the geometry of protein association. At high tension, protein interactions are strongly inhibited. Increasing surface density of proteins leads to a wider range of protein association geometries, promoting the formation of meshes, which can be broken apart with membrane tension. Our work indicates that surface tension may play a key role in recruiting proteins to membrane-remodelling sites in the cell.

  4. Surface tension and the dodecahedron model for lung elasticity.

    PubMed

    Kimmel, E; Budiansky, B

    1990-05-01

    Macroscopic elastic moduli governing the incremental deformations of lung parenchyma are calculated on the basis of a model for an individual lung element in the shape of a regular dodecahedron. Elastic stiffness within the element is provided by pin-jointed tension members along the edges of the dodecahedron, surface tension is incorporated into its pentagonal faces, and the influence of transpulmonary pressure is simulated by an externally applied hydrostatic tension. The analysis is based on a variational statement of nonlinear structural mechanics, and the results show how the moduli depend on the effective inflation pressure, the constitutive behavior of the idealized truss members, and the surface-area dependent surface tension. The theory is discussed in the light of available experimental information. A more general analysis is needed to account for the effects of structural as well as surface-tension hysteresis.

  5. Effects of DDT and permethrin on neurite growth in cultured neurons of chick embryo brain and Lymnaea stagnalis.

    PubMed

    Ferguson, C A; Audesirk, G

    1990-01-01

    The pesticides permethrin and 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT), dissolved in either ethanol (EtOH) or dimethylsulphoxide (DMSO), were studied to determine their effect on neurite growth from cultured neurons of Lymnaea stagnalis and embryonic chicks. Both of these toxins decreased the percentage of neurons growing neurites, mean neurite length, and number of neurites/cell in a dose-dependent manner. DMSO increased the toxicity of permethrin and DDT in L. stagnalis neurons. EtOH was not used as a solvent with the embryonic chick cultures. Pre-existing neurites of L. stagnalis neurons exposed to permethrin regressed in a dose- and time-dependent manner. These two toxins may affect neurite outgrowth through interference with intracellular calcium regulation.

  6. Flow in porous media, phase behavior and ultralow interfacial tensions: Mechanisms of enhanced petroleum recovery: First annual report, October 1, 1985-September 30, 1986

    SciTech Connect

    Davis, H.T.; Scriven, L.E.

    1987-10-01

    A major program of university research, longer-ranged and more fundamental in approach than industrial research, into basic mechanisms of enhancing petroleum recovery and into underlying physics, chemistry, geology, applied mathematics, computation, and engineering science has been built at Minnesota. The 1985-86 outputs of the interdisciplinary team of investigators were again ideas, instruments, techniques, data, understanding and skilled people: 28 scientific and engineering publications in leading journals, two Ph.D. theses, the author of one going to industry, the other to a university, numerous presentations to scientific and technical meetings, and to industrial, governmental and university laboratories in the US., Europe and South America; and vigorous program of research visits to and from Minnesota. This report summarizes the papers and theses that emerged during the period 1 Oct 1985 to 30 Sept 1986 and features fifteen major accomplishments of the program during that year. Abstracts of the 28 publications and 2 theses are reported and several major accomplishments are reported in greater detail. Further details of information transfer and personnel exchange with industrial, governmental and university laboratories appear in Quarterly Reports available from the Department of Energy and are not reproduced here. The six sections in this report have been processed separately for inclusion in the Energy Data Base.

  7. Confronting Racial and Religious Tensions

    ERIC Educational Resources Information Center

    Wessler, Stephen

    2011-01-01

    When a community's demographics change quickly in terms of racial, religious, or ethnic makeup, Wessler notes, tension surfaces. Schools are the likeliest place for these kinds of tensions to openly come to a head. Schools can't always avoid conflicts among students who feel mutual prejudice and suspicion. But schools can address simmering…

  8. Confronting Racial and Religious Tensions

    ERIC Educational Resources Information Center

    Wessler, Stephen

    2011-01-01

    When a community's demographics change quickly in terms of racial, religious, or ethnic makeup, Wessler notes, tension surfaces. Schools are the likeliest place for these kinds of tensions to openly come to a head. Schools can't always avoid conflicts among students who feel mutual prejudice and suspicion. But schools can address simmering…

  9. [Neurite-stimulating effect of Hirudo medicinalis salivary gland secreting factors in organotypic culture of the dorsal root ganglia].

    PubMed

    Chalisova, N I; Baskova, I P; Zavalova, L L; Pennijainen, V A

    2001-06-01

    Effects of destabilise, bdellin, bdellin A, eglin were investigated in organotypic tissue culture of dorsal root ganglia (DRG) of 10-11-day old chick embryos. Native destabilase and bdellin A, bdellin B and eglin are more active inducing a more intensive neurite growth in DRG as compared with the control. A neurite-stimulating effect of the drug "pyjavit" seems to be associated with destabilase, bdellins and eglin neurite-stimulating activity.

  10. Novel High Content Screen Detects Compounds That Promote Neurite Regeneration from Cochlear Spiral Ganglion Neurons.

    PubMed

    Whitlon, Donna S; Grover, Mary; Dunne, Sara F; Richter, Sonja; Luan, Chi-Hao; Richter, Claus-Peter

    2015-11-02

    The bipolar spiral ganglion neurons (SGN) carry sound information from cochlear hair cells to the brain. After noise, antibiotic or toxic insult to the cochlea, damage to SGN and/or hair cells causes hearing impairment. Damage ranges from fiber and synapse degeneration to dysfunction and loss of cells. New interventions to regenerate peripheral nerve fibers could help reestablish transfer of auditory information from surviving or regenerated hair cells or improve results from cochlear implants, but the biochemical mechanisms to target are largely unknown. Presently, no drugs exist that are FDA approved to stimulate the regeneration of SGN nerve fibers. We designed an original phenotypic assay to screen 440 compounds of the NIH Clinical Collection directly on dissociated mouse spiral ganglia. The assay detected one compound, cerivastatin, that increased the length of regenerating neurites. The effect, mimicked by other statins at different optimal concentrations, was blocked by geranylgeraniol. These results demonstrate the utility of screening small compound libraries on mixed cultures of dissociated primary ganglia. The success of this screen narrows down a moderately sized library to a single compound which can be elevated to in-depth in vivo studies, and highlights a potential new molecular pathway for targeting of hearing loss drugs.

  11. Neuronal PINCH is Regulated by TNF-α and is Required for Neurite Extension

    PubMed Central

    Jatiani, Asavari; Pannizzo, Paola; Gualco, Elisa; Del-Valle, Luis

    2011-01-01

    During HIV infection of the CNS, neurons are damaged by viral proteins, such as Tat and gp120, or by inflammatory factors, such as TNF-α, that are released from infected and/or activated glial cells. Host responses to this damage may include the induction of survival or repair mechanisms. In this context, previous studies report robust expression of a protein called particularly interesting new cysteine histidine-rich protein (PINCH), in the neurons of HIV patients’ brains, compared with nearly undetectable levels in HIV-negative individuals (Rearden et al., J Neurosci Res 86:2535–2542, 2008), suggesting PINCH’s involvement in neuronal signaling during HIV infection of the brain. To address potential triggers for PINCH induction in HIV patients’ brains, an in vitro system mimicking some aspects of HIV infection of the CNS was utilized. We investigated neuronal PINCH expression, subcellular distribution, and biological consequences of PINCH sequestration upon challenge with Tat, gp120, and TNF-α. Our results indicate that in neurons, TNF-α stimulation increases PINCH expression and changes its subcellular localization. Furthermore, PINCH mobility is required to maintain neurite extension upon challenge with TNF-α. PINCH may function as a neuron-specific host-mediated response to challenge by HIV-related factors in the CNS. PMID:20689998

  12. Novel High Content Screen Detects Compounds That Promote Neurite Regeneration from Cochlear Spiral Ganglion Neurons

    PubMed Central

    Whitlon, Donna S.; Grover, Mary; Dunne, Sara F.; Richter, Sonja; Luan, Chi-Hao; Richter, Claus-Peter

    2015-01-01

    The bipolar spiral ganglion neurons (SGN) carry sound information from cochlear hair cells to the brain. After noise, antibiotic or toxic insult to the cochlea, damage to SGN and/or hair cells causes hearing impairment. Damage ranges from fiber and synapse degeneration to dysfunction and loss of cells. New interventions to regenerate peripheral nerve fibers could help reestablish transfer of auditory information from surviving or regenerated hair cells or improve results from cochlear implants, but the biochemical mechanisms to target are largely unknown. Presently, no drugs exist that are FDA approved to stimulate the regeneration of SGN nerve fibers. We designed an original phenotypic assay to screen 440 compounds of the NIH Clinical Collection directly on dissociated mouse spiral ganglia. The assay detected one compound, cerivastatin, that increased the length of regenerating neurites. The effect, mimicked by other statins at different optimal concentrations, was blocked by geranylgeraniol. These results demonstrate the utility of screening small compound libraries on mixed cultures of dissociated primary ganglia. The success of this screen narrows down a moderately sized library to a single compound which can be elevated to in-depth in vivo studies, and highlights a potential new molecular pathway for targeting of hearing loss drugs. PMID:26521685

  13. Dishevelled attenuates the repelling activity of Wnt signaling during neurite outgrowth in Caenorhabditis elegans

    PubMed Central

    Zheng, Chaogu; Diaz-Cuadros, Margarete; Chalfie, Martin

    2015-01-01

    Wnt proteins regulate axonal outgrowth along the anterior–posterior axis, but the intracellular mechanisms that modulate the strength of Wnt signaling in axon guidance are largely unknown. Using the Caenorhabditis elegans mechanosensory PLM neurons, we found that posteriorly enriched LIN-44/Wnt acts as a repellent to promote anteriorly directed neurite outgrowth through the LIN-17/Frizzled receptor, instead of controlling neuronal polarity as previously thought. Dishevelled (Dsh) proteins DSH-1 and MIG-5 redundantly mediate the repulsive activity of the Wnt signals to induce anterior outgrowth, whereas DSH-1 also provides feedback inhibition to attenuate the signaling to allow posterior outgrowth against the Wnt gradient. This inhibitory function of DSH-1, which requires its dishevelled, Egl-10, and pleckstrin (DEP) domain, acts by promoting LIN-17 phosphorylation and is antagonized by planar cell polarity signaling components Van Gogh (VANG-1) and Prickle (PRKL-1). Our results suggest that Dsh proteins both respond to Wnt signals to shape neuronal projections and moderate its activity to fine-tune neuronal morphology. PMID:26460008

  14. Regulation of early neurite morphogenesis by the Na+/H+ exchanger NHE1.

    PubMed

    Sin, Wun-Chey; Moniz, David M; Ozog, Mark A; Tyler, Jessica E; Numata, Masayuki; Church, John

    2009-07-15

    The ubiquitously expressed Na(+)/H(+) exchanger NHE1 plays an important role in regulating polarized membrane protrusion and directional motility in non-neuronal cells. Using NGF-differentiated PC12 cells and murine neocortical neurons in vitro, we now show that NHE1 plays a role in regulating early neurite morphogenesis. NHE1 was expressed in growth cones in which it gave rise to an elevated intracellular pH in actively extending neurites. The NHE1 inhibitor cariporide reversibly reduced growth cone filopodia number and the formation and elongation of neurites, especially branches, whereas the transient overexpression of full-length NHE1, but not NHE1 mutants deficient in either ion translocation activity or actin cytoskeletal anchoring, elicited opposite effects. In addition, compared with neocortical neurons obtained from wild-type littermates, neurons isolated from NHE1-null mice exhibited reductions in early neurite outgrowth, an effect that was rescued by overexpression of full-length NHE1 but not NHE1 mutants. Finally, the growth-promoting effects of netrin-1, but not BDNF or IGF-1, were markedly reduced by cariporide in wild-type neocortical neurons and were not observed in NHE1-null neurons. Although netrin-1 failed to increase growth cone intracellular pH or Na(+)/H(+) exchange activity, netrin-1-induced increases in early neurite outgrowth were restored in NHE1-null neurons transfected with full-length NHE1 but not an ion translocation-deficient mutant. Collectively, the results indicate that NHE1 participates in the regulation of early neurite morphogenesis and identify a novel role for NHE1 in the promotion of early neurite outgrowth by netrin-1.

  15. Gene dosage-dependent rescue of HSP neurite defects in SPG4 patients’ neurons

    PubMed Central

    Havlicek, Steven; Kohl, Zacharias; Mishra, Himanshu K.; Prots, Iryna; Eberhardt, Esther; Denguir, Naime; Wend, Holger; Plötz, Sonja; Boyer, Leah; Marchetto, Maria C.N.; Aigner, Stefan; Sticht, Heinrich; Groemer, Teja W.; Hehr, Ute; Lampert, Angelika; Schlötzer-Schrehardt, Ursula; Winkler, Jürgen; Gage, Fred H.; Winner, Beate

    2014-01-01

    The hereditary spastic paraplegias (HSPs) are a heterogeneous group of motorneuron diseases characterized by progressive spasticity and paresis of the lower limbs. Mutations in Spastic Gait 4 (SPG4), encoding spastin, are the most frequent cause of HSP. To understand how mutations in SPG4 affect human neurons, we generated human induced pluripotent stem cells (hiPSCs) from fibroblasts of two patients carrying a c.1684C>T nonsense mutation and from two controls. These SPG4 and control hiPSCs were able to differentiate into neurons and glia at comparable efficiency. All known spastin isoforms were reduced in SPG4 neuronal cells. The complexity of SPG4 neurites was decreased, which was paralleled by an imbalance of axonal transport with less retrograde movement. Prominent neurite swellings with disrupted microtubules were present in SPG4 neurons at an ultrastructural level. While some of these swellings contain acetylated and detyrosinated tubulin, these tubulin modifications were unchanged in total cell lysates of SPG4 neurons. Upregulation of another microtubule-severing protein, p60 katanin, may partially compensate for microtubuli dynamics in SPG4 neurons. Overexpression of the M1 or M87 spastin isoforms restored neurite length, branching, numbers of primary neurites and reduced swellings in SPG4 neuronal cells. We conclude that neurite complexity and maintenance in HSP patient-derived neurons are critically sensitive to spastin gene dosage. Our data show that elevation of single spastin isoform levels is sufficient to restore neurite complexity and reduce neurite swellings in patient cells. Furthermore, our human model offers an ideal platform for pharmacological screenings with the goal to restore physiological spastin levels in SPG4 patients. PMID:24381312

  16. Gene dosage-dependent rescue of HSP neurite defects in SPG4 patients' neurons.

    PubMed

    Havlicek, Steven; Kohl, Zacharias; Mishra, Himanshu K; Prots, Iryna; Eberhardt, Esther; Denguir, Naime; Wend, Holger; Plötz, Sonja; Boyer, Leah; Marchetto, Maria C N; Aigner, Stefan; Sticht, Heinrich; Groemer, Teja W; Hehr, Ute; Lampert, Angelika; Schlötzer-Schrehardt, Ursula; Winkler, Jürgen; Gage, Fred H; Winner, Beate

    2014-05-15

    The hereditary spastic paraplegias (HSPs) are a heterogeneous group of motorneuron diseases characterized by progressive spasticity and paresis of the lower limbs. Mutations in Spastic Gait 4 (SPG4), encoding spastin, are the most frequent cause of HSP. To understand how mutations in SPG4 affect human neurons, we generated human induced pluripotent stem cells (hiPSCs) from fibroblasts of two patients carrying a c.1684C>T nonsense mutation and from two controls. These SPG4 and control hiPSCs were able to differentiate into neurons and glia at comparable efficiency. All known spastin isoforms were reduced in SPG4 neuronal cells. The complexity of SPG4 neurites was decreased, which was paralleled by an imbalance of axonal transport with less retrograde movement. Prominent neurite swellings with disrupted microtubules were present in SPG4 neurons at an ultrastructural level. While some of these swellings contain acetylated and detyrosinated tubulin, these tubulin modifications were unchanged in total cell lysates of SPG4 neurons. Upregulation of another microtubule-severing protein, p60 katanin, may partially compensate for microtubuli dynamics in SPG4 neurons. Overexpression of the M1 or M87 spastin isoforms restored neurite length, branching, numbers of primary neurites and reduced swellings in SPG4 neuronal cells. We conclude that neurite complexity and maintenance in HSP patient-derived neurons are critically sensitive to spastin gene dosage. Our data show that elevation of single spastin isoform levels is sufficient to restore neurite complexity and reduce neurite swellings in patient cells. Furthermore, our human model offers an ideal platform for pharmacological screenings with the goal to restore physiological spastin levels in SPG4 patients.

  17. The influence of a weight-bearing platform on the mechanical behavior of two Ilizarov ring fixators: tensioned wires vs. half-pins

    PubMed Central

    2011-01-01

    Background A weight-bearing platform applied at the distal end of an Ilizarov external frame allows patients with hindfoot transfixations, foot deformities or plantar skin lesions to bear weight. This leads to an indirect loading of the fracture or osteotomy site. However, the effect on the fracture/osteotomy site's motion or compressive loads is unknown. The aim of this study was to analyze the mechanical effects of a weight-bearing platform on the traditional all-wire, four-ring frame in comparison to a two-ring frame consisting of half-pins. Methods Two frame configurations, with either anatomically positioned wires or half-pins, were analyzed with and without a weight-bearing platform applied underneath the distal ring. Composite tibiae with a mid-diaphyseal osteotomy of 3.5 mm were used in all the experiments. An axial load was applied with the use of a universal test machine (UTS®). Interfragmentary movements, the relative movements of bone fragments and movements between rings were recorded using displacement transducers. Compressive loads at the osteotomy site were recorded with loading cells. Results Indirect loading with a weight-bearing platform altered the force transmission through the osteotomy. Indirect loading of the tibiae decreased the extent of the axial micro-motion by 50% under the applied weight load when compared to direct weight loading (p < 0.05). The half pin frame was 25% stiffer than the wire frame under both direct and indirect loading of the tibiae (p < 0.05). Compressive loads under indirect loading were reduced by 67% in the wire frame and by 57% in the half-pin frames compared to direct loading of the bones (p < 0.05). While axial loading in the wire frames resulted in plain axial movements at the site of the osteotomy, it was coupled with translational movements and angular displacements in the half pin mountings. This effect was more apparent in the case of indirect loading. Conclusions A weight-bearing platform has substantial

  18. Micropatterned coumarin polyester thin films direct neurite orientation.

    PubMed

    McCormick, Aleesha M; Maddipatla, Murthy V S N; Shi, Shuojia; Chamsaz, Elaheh A; Yokoyama, Hiroshi; Joy, Abraham; Leipzig, Nic D

    2014-11-26

    Guidance and migration of cells in the nervous system is imperative for proper development, maturation, and regeneration. In the peripheral nervous system (PNS), it is challenging for axons to bridge critical-sized injury defects to achieve repair and the central nervous system (CNS) has a very limited ability to regenerate after injury because of its innate injury response. The photoreactivity of the coumarin polyester used in this study enables efficient micropatterning using a custom digital micromirror device (DMD) and has been previously shown to be biodegradable, making these thin films ideal for cell guidance substrates with potential for future in vivo applications. With DMD, we fabricated coumarin polyester thin films into 10×20 μm and 15×50 μm micropatterns with depths ranging from 15 to 20 nm to enhance nervous system cell alignment. Adult primary neurons, oligodendrocytes, and astrocytes were isolated from rat brain tissue and seeded onto the polymer surfaces. After 24 h, cell type and neurite alignment were analyzed using phase contrast and fluorescence imaging. There was a significant difference (p<0.0001) in cell process distribution for both emergence angle (from the body of the cell) and orientation angle (at the tip of the growth cone) confirming alignment on patterned surfaces compared to control substrates (unpatterned polymer and glass surfaces). The expected frequency distribution for parallel alignment (≤15°) is 14% and the two micropatterned groups ranged from 42 to 49% alignment for emergence and orientation angle measurements, where the control groups range from 12 to 22% for parallel alignment. Despite depths being 15 to 20 nm, cell processes could sense these topographical changes and preferred to align to certain features of the micropatterns like the plateau/channel interface. As a result this initial study in utilizing these new DMD micropatterned coumarin polyester thin films has proven beneficial as an axon guidance platform

  19. SURFACE TENSION OF SERUM

    PubMed Central

    du Noüy, P. Lecomte

    1925-01-01

    1. The injection of antigen into an animal determines a gradual change in the blood fluid which finds expression in two physicochemical manifestations that can readily be followed, namely a decrease in the static value of the surface tension of serum solutions, and a special form of crystallization when serum diluted with isotonic sodium chloride solution is allowed to evaporate under certain conditions. 2. The change in the blood is at a maximum around the 13th day after the first antigen injection, and decreases progressively thereafter until it can no longer be observed, which is usually around the 30th day. 3. The change follows the same course, whether a single large injection of antigen is made, or many smaller ones. It begins at the same time in either case, it comes to a maximum after the same period, and in its subsequent course it is not affected by the reinjection of antigen. The manifestations of the change would appear to be independent of the presence of antigen in the circulation. 4. The mean length of the protein molecules of the immune serum obtained after the injection of the antigen dealt with is little if at all different from that of the protein molecules of normal serum. 5. It is possible that this reaction is independent of the antibody formation. PMID:19869026

  20. Leucine-rich repeat kinase 2 interacts with p21-activated kinase 6 to control neurite complexity in mammalian brain.

    PubMed

    Civiero, Laura; Cirnaru, Maria Daniela; Beilina, Alexandra; Rodella, Umberto; Russo, Isabella; Belluzzi, Elisa; Lobbestael, Evy; Reyniers, Lauran; Hondhamuni, Geshanthi; Lewis, Patrick A; Van den Haute, Chris; Baekelandt, Veerle; Bandopadhyay, Rina; Bubacco, Luigi; Piccoli, Giovanni; Cookson, Mark R; Taymans, Jean-Marc; Greggio, Elisa

    2015-12-01

    Leucine-rich repeat kinase 2 (LRRK2) is a causative gene for Parkinson's disease, but the physiological function and the mechanism(s) by which the cellular activity of LRRK2 is regulated are poorly understood. Here, we identified p21-activated kinase 6 (PAK6) as a novel interactor of the GTPase/ROC domain of LRRK2. p21-activated kinases are serine-threonine kinases that serve as targets for the small GTP binding proteins Cdc42 and Rac1 and have been implicated in different morphogenetic processes through remodeling of the actin cytoskeleton such as synapse formation and neuritogenesis. Using an in vivo neuromorphology assay, we show that PAK6 is a positive regulator of neurite outgrowth and that LRRK2 is required for this function. Analyses of post-mortem brain tissue from idiopathic and LRRK2 G2019S carriers reveal an increase in PAK6 activation state, whereas knock-out LRRK2 mice display reduced PAK6 activation and phosphorylation of PAK6 substrates. Taken together, these results support a critical role of LRRK2 GTPase domain in cytoskeletal dynamics in vivo through the novel interactor PAK6, and provide a valuable platform to unravel the mechanism underlying LRRK2-mediated pathophysiology. We propose p21-activated kinase 6 (PAK6) as a novel interactor of leucine-rich repeat kinase 2 (LRRK2), a kinase involved in Parkinson's disease (PD). In health, PAK6 regulates neurite complexity in the brain and LRRK2 is required for its function, (a) whereas PAK6 is aberrantly activated in LRRK2-linked PD brain (b) suggesting that LRRK2 toxicity is mediated by PAK6.

  1. Essential role of NKCC1 in NGF-induced neurite outgrowth

    SciTech Connect

    Nakajima, Ken-ichi; Miyazaki, Hiroaki; Niisato, Naomi; Marunaka, Yoshinori . E-mail: marunaka@koto.kpu-m.ac.jp

    2007-08-03

    The Na{sup +}/K{sup +}/2Cl{sup -} cotransporter (NKCC) mediates electroneutral transport of 2Cl{sup -} coupled with Na{sup +} and K{sup +} across the plasma membrane, and plays crucial roles in Cl{sup -} uptake into the cells, homeostasis of cellular Cl{sup -}, and cell volume regulation. However, we have very limited information on the roles of ion transporters in neurite outgrowth in neuronal cells. In the present study, we report the role of NKCC1 (an isoform of NKCC) in NGF-induced neurite outgrowth of rat pheochromocytoma PC12D cells. The expression level of NKCC1 protein was increased by NGF treatment. Knock-down of NKCC1 by RNA interference (RNAi) drastically diminished the NGF-induced neurite outgrowth. Transfection of enhanced green fluorescent protein (EGFP)-tagged rat NKCC1 into cells for clarification of intracellular localization of NKCC1 revealed that the EGFP-rNKCC1 was mainly localized in the plasma membrane at growth cone during neurite outgrowth. These observations suggest that NKCC1 plays a fundamental role in NGF-induced neurite outgrowth of PC12D cells.

  2. FK962 induces neurite outgrowth in cultured monkey trigeminal ganglion cells.

    PubMed

    Nakajima, Emi; Walkup, Ryan D; Shearer, Thomas R; Azuma, Mitsuyoshi

    2017-01-01

    Corneal sensation, cell proliferation, and wound healing all depend on adequate corneal innervation. Disruption of corneal innervation can lead to dry eye and delayed wound healing. Our studies in rats and rabbits show that the substituted fluorobenzamide drug FK962 accelerates the extension of neuronal processes and recovery of corneal sensitivity. The purpose of the present study was 1) to determine whether FK962 induces sprouting and elongation of neurites in cultured monkey trigeminal ganglion cells, and 2) to investigate the involvement of the neurotrophic peptide GDNF in FK962-induced neurite elongation. Dissociated, cultured trigeminal ganglion cells, containing neuronal and Schwann cells were cultured for 48 h with or without FK962. Neuronal elongation was evaluated by immunostaining with a neurofilament-specific antibody. Culture with or without GDNF, or with antibody against GDNF, was used to determine the role of GDNF in FK962-induced neurite elongation. FK962 or GDNF were found to significantly induce neurite elongation. The GDNF antibody significantly inhibited elongation induced by FK962. GDNF was found to be a mediator of FK962-induced neurite elongation in a relevant primate model. FK962 may be a candidate drug for treatment of neurotrophic disorders in the human cornea.

  3. The role of bioactive compounds on the promotion of neurite outgrowth.

    PubMed

    More, Sandeep Vasant; Koppula, Sushruta; Kim, In-Su; Kumar, Hemant; Kim, Byung-Wook; Choi, Dong-Kug

    2012-06-04

    Neurite loss is one of the cardinal features of neuronal injury. Apart from neuroprotection, reorganization of the lost neuronal network in the injured brain is necessary for the restoration of normal physiological functions. Neuritogenic activity of endogenous molecules in the brain such as nerve growth factor is well documented and supported by scientific studies which show innumerable compounds having neurite outgrowth activity from natural sources. Since the damaged brain lacks the reconstructive capacity, more efforts in research are focused on the identification of compounds that promote the reformation of neuronal networks. An abundancy of natural resources along with the corresponding activity profiles have shown promising results in the field of neuroscience. Recently, importance has also been placed on understanding neurite formation by natural products in relation to neuronal injury. Arrays of natural herbal products having plentiful active constituents have been found to enhance neurite outgrowth. They act synergistically with neurotrophic factors to promote neuritogenesis in the diseased brain. Therefore use of natural products for neuroregeneration provides new insights in drug development for treating neuronal injury. In this study, various compounds from natural sources with potential neurite outgrowth activity are reviewed in experimental models.

  4. Inhibition of Nischarin Expression Promotes Neurite Outgrowth through Regulation of PAK Activity

    PubMed Central

    Ding, Yuemin; Li, Yuying; Lu, Lingchao; Zhang, Ruyi; Zeng, Linghui; Wang, Linlin; Zhang, Xiong

    2015-01-01

    Nischarin is a cytoplasmic protein expressed in various organs that plays an inhibitory role in cell migration and invasion and the carcinogenesis of breast cancer cells. We previously reported that Nischarin is highly expressed in neuronal cell lines and is differentially expressed in the brain tissue of adult rats. However, the physiological function of Nischarin in neural cells remains unknown. Here, we show that Nischarin is expressed in rat primary cortical neurons but not in astrocytes. Nischarin is localized around the nucleus and dendrites. Using shRNA to knockdown the expression of endogenous Nischarin significantly increases the percentage of neurite-bearing cells, remarkably increases neurite length, and accelerates neurite extension in neuronal cells. Silencing Nischarin expression also promotes dendrite elongation in rat cortical neurons where Nischarin interacts with p21-activated kinase 1/2 (PAK1/2) and negatively regulates phosphorylation of both PAK1 and PAK2. The stimulation of neurite growth observed in cells with decreased levels of Nischarin is partially abolished by IPA3-mediated inhibition of PAK1 activity. Our findings indicate that endogenous Nischarin inhibits neurite outgrowth by blocking PAK1 activation in neurons. PMID:26670864

  5. Enhanced Neurite Growth from Mammalian Neurons in Three-Dimensional Salmon Fibrin Gels

    PubMed Central

    Ju, Yo-El; Janmey, Paul A.; McCormick, Margaret; Sawyer, Evelyn S.; Flanagan, Lisa A.

    2007-01-01

    Three-dimensional fibrin matrices have been used as cellular substrates in vitro and as bridging materials for central nervous system repair. Cells can be embedded within fibrin gels since the polymerization process is non-toxic, making fibrin an attractive scaffold for transplanted cells. Most studies have utilized fibrin prepared from human or bovine blood proteins. However, fish fibrin may be well suited for neuronal growth since fish undergo remarkable central nervous system regeneration and molecules implicated in this process are present in fibrin. We assessed the growth of mammalian central nervous system neurons in bovine, human, and salmon fibrin and found that salmon fibrin gels encouraged the greatest degree of neurite (dendrite and axon) growth and were the most resistant to degradation by cellular proteases. The neurite growth-promoting effect was not due to the thrombin used to polymerize the gels or to any copurifying plasminogen. Co-purified fibronectin partially accounted for the effect on neurites, and blockade of fibrinogen/fibrin-binding integrins markedly decreased neurite growth. Anion exchange chromatography revealed different elution profiles for salmon and mammalian fibrinogens. These data demonstrate that salmon fibrin encourages the growth of neurites from mammalian neurons and suggest that salmon fibrin may be a beneficial scaffold for neuronal regrowth after CNS injury. PMID:17258313

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

    PubMed

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

    2006-06-01

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

  7. A Facile Method for Simultaneously Measuring Neuronal Cell Viability and Neurite Outgrowth

    PubMed Central

    K. Hancock, Michael; Kopp, Leisha; Kaur, Navjot; Hanson, Bonnie J.

    2015-01-01

    Neurite outgrowth is an important morphological phenotype of neuronal cells that correlates with their function and cell health, yet there are limited methods available for measuring this phenomenon. Current approaches to measuring neurite outgrowth are laborious and time-consuming, relying largely upon immunocytochemical staining of neuronal markers (e.g., beta-III tubulin or MAP2) followed by manual or automated microscopy for image acquisition and analysis. Here we report the development of a quick and simple dual-color fluorescent dye-based staining method that allows for the simultaneous measurement of neuronal cell health and relative neurite outgrowth from the same sample. An orangered fluorescent dye that stains cell membrane surfaces is used as an indirect reporter of changes in relative neurite outgrowth due to alterations in the number or length of membrane projections emanating from neuronal cell bodies. Cell viability is assessed simultaneously via the use of a cell-permeant dye that is converted by intracellular esterase activity from a non-fluorescent substrate to a green-fluorescent product. Using Neuroscreen-1 cells (a PC-12 subclone), primary rat cortex neurons, and human induced pluripotent stem cell (iPSC)-derived neurons, we demonstrate that this multiplex assay allows for rapid visualization and unbiased, quantitative plate reader analysis of neuronal cell health and neurite outgrowth. PMID:25853055

  8. Berberine regulates neurite outgrowth through AMPK-dependent pathways by lowering energy status

    SciTech Connect

    Lu, Jiaqi; Cao, Yuanzhao; Cheng, Kuoyuan; Xu, Bo; Wang, Tianchang; Yang, Qi; Yang, Qin; Feng, Xudong; Xia, Qing

    2015-06-10

    As a widely used anti-bacterial agent and a metabolic inhibitor as well as AMP-activated protein kinase (AMPK) activator, berberine (BBR) has been shown to cross the blood–brain barrier. Its efficacy has been investigated in various disease models of the central nervous system. Neurite outgrowth is critical for nervous system development and is a highly energy-dependent process regulated by AMPK-related pathways. In the present study, we aimed to investigate the effects of BBR on AMPK activation and neurite outgrowth in neurons. The neurite outgrowth of primary rat cortical neurons at different stages of polarization was monitored after exposure of BBR. Intracellular energy level, AMPK activation and polarity-related pathways were also inspected. The results showed that BBR suppressed neurite outgrowth and affected cytoskeleton stability in the early stages of neuronal polarization, which was mediated by lowered energy status and AMPK activation. Liver kinase B1 and PI3K–Akt–GSK3β signaling pathways were also involved. In addition, mitochondrial dysfunction and endoplasmic reticulum stress contributed to the lowered energy status induced by BBR. This study highlighted the knowledge of the complex activities of BBR in neurons and corroborated the significance of energy status during the neuronal polarization. - Highlights: • BBR inhibited neurite outgrowth in early stages of neuronal development. • Lowered neuronal energy status was induced by BBR treatment. • Neuronal energy stress induced by BBR activated AMPK-related pathways. • BBR induced mitochondrial dysfunction and endoplasmic reticulum stress.

  9. Rab22 controls NGF signaling and neurite outgrowth in PC12 cells.

    PubMed

    Wang, Liang; Liang, Zhimin; Li, Guangpu

    2011-10-01

    Rab22 is a small GTPase that is localized on early endosomes and regulates early endosomal sorting. This study reports that Rab22 promotes nerve growth factor (NGF) signaling-dependent neurite outgrowth and gene expression in PC12 cells by sorting NGF and the activated/phosphorylated receptor (pTrkA) into signaling endosomes to sustain signal transduction in the cell. NGF binding induces the endocytosis of pTrkA into Rab22-containing endosomes. Knockdown of Rab22 via small hairpin RNA (shRNA) blocks NGF-induced pTrkA endocytosis into the endosomes and gene expression (VGF) and neurite outgrowth. Overexpression of human Rab22 can rescue the inhibitory effects of the Rab22 shRNA, suggesting a specific Rab22 function in NGF signal transduction, rather than off-target effects. Furthermore, the Rab22 effector, Rabex-5, is necessary for NGF-induced neurite outgrowth and gene expression, as evidenced by the inhibitory effect of shRNA-mediated knockdown of Rabex-5. Disruption of the Rab22-Rabex-5 interaction via overexpression of the Rab22-binding domain of Rabex-5 in the cell also blocks NGF-induced neurite outgrowth, suggesting a critical role of Rab22-Rabex-5 interaction in the biogenesis of NGF-signaling endosomes to sustain the signal for neurite outgrowth. These data provide the first evidence for an early endosomal Rab GTPase as a positive regulator of NGF signal transduction and cell differentiation.

  10. Bingham-NODDI: Mapping anisotropic orientation dispersion of neurites using diffusion MRI.

    PubMed

    Tariq, Maira; Schneider, Torben; Alexander, Daniel C; Gandini Wheeler-Kingshott, Claudia A; Zhang, Hui

    2016-06-01

    This paper presents Bingham-NODDI, a clinically-feasible technique for estimating the anisotropic orientation dispersion of neurites. Direct quantification of neurite morphology on clinical scanners was recently realised by a diffusion MRI technique known as neurite orientation dispersion and density imaging (NODDI). However in its current form NODDI cannot estimate anisotropic orientation dispersion, which is widespread in the brain due to common fanning and bending of neurites. This work proposes Bingham-NODDI that extends the NODDI formalism to address this limitation. Bingham-NODDI characterises anisotropic orientation dispersion by utilising the Bingham distribution to model neurite orientation distribution. The new model estimates the extent of dispersion about the dominant orientation, separately along the primary and secondary dispersion orientations. These estimates are subsequently used to estimate the overall dispersion about the dominant orientation and the dispersion anisotropy. We systematically evaluate the ability of the new model to recover these key parameters of anisotropic orientation dispersion with standard NODDI protocol, both in silico and in vivo. The results demonstrate that the parameters of the proposed model can be estimated without additional acquisition requirements over the standard NODDI protocol. Thus anisotropic dispersion can be determined and has the potential to be used as a marker for normal brain development and ageing or in pathology. We additionally find that the original NODDI model is robust to the effects of anisotropic orientation dispersion, when the quantification of anisotropic dispersion is not of interest. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  11. Rosiglitazone promotes neurite outgrowth and mitochondrial function in N2A cells via PPARgamma pathway.

    PubMed

    Chiang, Ming-Chang; Cheng, Yi-Chuan; Chen, Han-Min; Liang, Yao-Jen; Yen, Chia-Hui

    2014-01-01

    Several pieces of evidence indicate that peroxisome proliferator-activated receptor gamma (PPARγ) stimulation promotes neuronal differentiation. However, to date, the effects of a synthetic PPARγ agonist (Rosiglitazone, Rosi) on neurite outgrowth have not yet been well described. Here we have evaluated the effects of Rosi on neurite outgrowth and mitochondrial function in the mouse neuroblastoma Neuro 2a (N2A) cell line. Our results show that Rosi promotes neurite outgrowth of N2A cells and significantly increases the population of neurite-bearing cells, with apparent increase of intracellular calcium and the expression of calmodulin-dependent kinase I (CaMKI). Rosi also increases the intracellular cAMP and expression of both protein kinase A (PKA) and cAMP response element binding protein (CREB). Phosphorylation of CREB was also detected in the Rosi treated N2A cells. Moreover, Rosi significantly increases the transcription of AMP-activated kinase (AMPK) and Sirtuin 1 (SIRT1). Besides, the expression of PPAR coactivator 1α (PGC1α), as well as the mRNA level its downstream genes, including nuclear respiratory factors 1 and 2 (NRF1 and NRF2) and mitochondrial transcription factor A (Tfam) were induced by Rosi treatments. Furthermore, Rosi increases the level of ATP, D-loop, and mitochondrial mass in N2A cells. Collectively, these findings provide an array of evidence that PPARγ activation provides beneficial neuronal networks within neurite outgrowth.

  12. Detection of neuritic plaques in Alzheimer’s disease by magnetic resonance microscopy

    PubMed Central

    Benveniste, Helene; Einstein, Gillian; Kim, Katie R.; Hulette, Christine; Johnson, G. Allan

    1999-01-01

    Magnetic resonance microscopy (MRM) theoretically provides the spatial resolution and signal-to-noise ratio needed to resolve neuritic plaques, the neuropathological hallmark of Alzheimer’s disease (AD). Two previously unexplored MR contrast parameters, T2* and diffusion, are tested for plaque-specific contrast to noise. Autopsy specimens from nondemented controls (n = 3) and patients with AD (n = 5) were used. Three-dimensional T2* and diffusion MR images with voxel sizes ranging from 3 × 10−3 mm3 to 5.9 × 10−5 mm3 were acquired. After imaging, specimens were cut and stained with a microwave king silver stain to demonstrate neuritic plaques. From controls, the alveus, fimbria, pyramidal cell layer, hippocampal sulcus, and granule cell layer were detected by either T2* or diffusion contrast. These structures were used as landmarks when correlating MRMs with histological sections. At a voxel resolution of 5.9 × 10−5 mm3, neuritic plaques could be detected by T2*. The neuritic plaques emerged as black, spherical elements on T2* MRMs and could be distinguished from vessels only in cross-section when presented in three dimension. Here we provide MR images of neuritic plaques in vitro. The MRM results reported provide a new direction for applying this technology in vivo. Clearly, the ability to detect and follow the early progression of amyloid-positive brain lesions will greatly aid and simplify the many possibilities to intervene pharmacologically in AD. PMID:10570201

  13. IL-1{beta} promotes neurite outgrowth by deactivating RhoA via p38 MAPK pathway

    SciTech Connect

    Temporin, Ko; Tanaka, Hiroyuki Kuroda, Yusuke; Okada, Kiyoshi; Yachi, Koji; Moritomo, Hisao; Murase, Tsuyoshi; Yoshikawa, Hideki

    2008-01-11

    Expression of the pro-inflammatory cytokine interleukin-1 beta (IL-1{beta}) is increased following the nervous system injury. Generally IL-1{beta} induces inflammation, leading to neural degeneration, while several neuropoietic effects have also been reported. Although neurite outgrowth is an important step in nerve regeneration, whether IL-1{beta} takes advantages on it is unclear. Now we examine how it affects neurite outgrowth. Following sciatic nerve injury, expression of IL-1{beta} is increased in Schwann cells around the site of injury, peaking 1 day after injury. In dorsal root ganglion (DRG) neurons and cerebellar granule neurons (CGNs), neurite outgrowth is inhibited by the addition of myelin-associated glycoprotein (MAG), activating RhoA. IL-1{beta} overcomes MAG-induced neurite outgrowth inhibition, by deactivating RhoA. Intracellular signaling experiments reveal that p38 MAPK, and not nuclear factor-kappa B (NF-{kappa}B), mediated this effect. These findings suggest that IL-1{beta} may contribute to nerve regeneration by promoting neurite outgrowth following nerve injury.

  14. A comparative first-principles study on electronic structures and mechanical properties of ternary intermetallic compounds Al8Cr4Y and Al8Cu4Y: Pressure and tension effects

    NASA Astrophysics Data System (ADS)

    Yang, Wenchao; Pang, Mingjun; Tan, Yong; Zhan, Yongzhong

    2016-11-01

    An investigation into the bulk properties, elastic properties and Debye temperature under pressure, and deformation mode under tension of Al8Cu4Y and Al8Cr4Y compounds was investigated by using first principles calculations based on density functional theory. The calculated lattice constants for the ternary compounds (Al8Cu4Y and Al8Cr4Y) are in good agreement with the experimental data. It can be seen from interatomic distances that the bonding between Al1 atom and Cr, Y, and Al2 atoms in Al8Cr4Y are stronger than Al8Cu4Y. The results of cohesive energy show that Al8Cr4Y should be easier to be formed and much stronger chemical bonds than Al8Cu4Y. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν can be obtained by using the Voigt-Reuss-Hill averaging scheme. From the results of elastic properties, Al8Cr4Y has the stronger mechanical behavior than Al8Cu4Y. Our calculations also show that pressure has a greater effect on mechanical behavior for both compounds. The ideal tensile strength are obtained by stress-strain relationships under [001](001) uniaxial tensile deformation, which are 15.4 and 23.4 GPa for Al8Cu4Y and Al8Cr4Y, respectively. The total and partial density of states and electron charge density under uniaxial tensile deformations for Al8Cu4Y and Al8Cr4Y compounds are also calculated and discussed in this work.

  15. An interlaminar tension strength specimen

    NASA Technical Reports Server (NTRS)

    Jackson, Wade C.; Martin, Roderick H.

    1992-01-01

    This paper describes a technique to determine interlaminar tension strength, sigma(sub 3c) of a fiber reinforced composite material using a curved beam. The specimen was a unidirectional curved beam, bent 90 degrees, with straight arms. Attached to each arm was a hinged loading mechanism which was held by the grips of a tensile testing machine. Geometry effects of the specimen, including the effects of loading arm length, inner radius, thickness, and width, were studied. The data sets fell into two categories: low strength corresponding to a macroscopic flaw related failure and high strength corresponding to a microscopic flaw related failure. From the data available, the loading arm length had no effect on sigma(sub 3c). The inner radius was not expected to have a significant effect on sigma(sub 3c), but this conclusion could not be confirmed because of differences in laminate quality for each curve geometry. The thicker specimens had the lowest value of sigma(sub 3c) because of poor laminate quality. Width was found to affect the value of sigma(sub 3c) only slightly. The wider specimens generally had a slightly lower strength since more material was under high stress, and hence, had a larger probability of containing a significant flaw.

  16. Cholinergic neuronotrophic factors: V. Segregation of survival- and neurite-promoting activities in heart-conditioned media.

    PubMed

    Adler, R; Varon, S

    1980-04-28

    Chick embryo ciliary ganglionic (CG) neurons will not survive in monolayer culture unless special supplements are provided in the medium. We have previously reported that two such supplements, chick embryo extract and medium conditioned over chick heart cell cultures (HCM) share the capacity to support survival of CG neurons but differ in their neurite-promoting effects. Thus, embryo extract elicited neuritic outgrowth only on collagen and HCM did so only on polyornithine (PORN), although both agents supported neuronal survival on both substrata. We report here the separation and quantitation of two different HCM components. One is a trophic agent which supports survival of CG neurons on either collagen or PORN, but does not seem to adsorb to either substratum. The other is a neurite-promoting factor (NPF) which adsorbs to PORN but not to collagen. Overnight incubation of HCM on PORN yields two products: (i) an NPF-deprived HCM, that has no neurite-promoting activity and (ii) an NPF-coated PORN, that promotes neuritic development of CG neurons trophically supported by either embryo extract or NPF-deprived HCM. CG requirements for neuritic outgrowth were also examined in explant cultures. No neurites were present after 24 h when explants were cultured in plain medium on PORN. Very extensive radial neuritic outgrowth was observed when explants were cultured in HCM on fresh PORN, or in NPF-deprived HCM on NPF-derivatized PORN. In contrast to what happens with dissociated cells, neuritic outgrowth was also present when ganglia were cultured in NPF-deprived HCM on fresh PORN. However, neurites grew radially only to a limited extent, after which they adopted a circular pattern grossly concentric to the ganglionic explant. It is proposed that explanted ciliary ganglia produce a neurite-promoting factor that coats the PORN substratum in widening circles.

  17. Effects of nerve growth factor and heart cell conditioned medium on neurite regeneration of aged sympathetic neurons in culture.

    PubMed

    Uchida, Y; Tomonaga, M

    1985-11-25

    The effects of nerve growth factor (NGF) and heart-cell-conditioned medium (HCM) on the neurite regeneration of aged sympathetic neurons were investigated in culture. Investigation of HCM was carried out by two different methods: one was the use of whole HCM on collagen substratum, which reflected component(s) effective in solution (HCM-S); the other was the use of polyornithine (PORN)-binding component(s) (P-HCM). Superior cervical ganglion neurons prepared from male mice from 6 to 30 months of age were cultured in MEM-10% FCS on collagen or gelatin-PORN substratum for 3 days. The number of neurons with neurites and the length of neurites were quantified as neurite production and elongation, respectively. Neuronal survival was not affected by addition of NGF, HCM-S or P-HCM. Neurite production of early adult neurons was enhanced by NGF, HCM-S or P-HCM. In contrast, neurite production of aged neurons was enhanced by only HCM-S, but not NGF or P-HCM. HCM-S did not promote neurite elongation in neurons at any age. Neurite elongation of early adult neurons was enhanced by NGF or P-HCM. Neurite elongation of aged neurons was enhanced by P-HCM. However, responsiveness of NGF for neurite elongation varied according to substrata. No age-related difference was found in neurite production and elongation in the absence of NGF, HCM-S or P-HCM. These results indicate that responsiveness of aged sympathetic neurons is various in different growth factors.

  18. DNA loops generate intracentromere tension in mitosis

    PubMed Central

    Lawrimore, Josh; Vasquez, Paula A.; Falvo, Michael R.; Taylor, Russell M.; Vicci, Leandra; Yeh, Elaine; Forest, M. Gregory

    2015-01-01

    The centromere is the DNA locus that dictates kinetochore formation and is visibly apparent as heterochromatin that bridges sister kinetochores in metaphase. Sister centromeres are compacted and held together by cohesin, condensin, and topoisomerase-mediated entanglements until all sister chromosomes bi-orient along the spindle apparatus. The establishment of tension between sister chromatids is essential for quenching a checkpoint kinase signal generated from kinetochores lacking microtubule attachment or tension. How the centromere chromatin spring is organized and functions as a tensiometer is largely unexplored. We have discovered that centromere chromatin loops generate an extensional/poleward force sufficient to release nucleosomes proximal to the spindle axis. This study describes how the physical consequences of DNA looping directly underlie the biological mechanism for sister centromere separation and the spring-like properties of the centromere in mitosis. PMID:26283798

  19. DNA loops generate intracentromere tension in mitosis.

    PubMed

    Lawrimore, Josh; Vasquez, Paula A; Falvo, Michael R; Taylor, Russell M; Vicci, Leandra; Yeh, Elaine; Forest, M Gregory; Bloom, Kerry

    2015-08-17

    The centromere is the DNA locus that dictates kinetochore formation and is visibly apparent as heterochromatin that bridges sister kinetochores in metaphase. Sister centromeres are compacted and held together by cohesin, condensin, and topoisomerase-mediated entanglements until all sister chromosomes bi-orient along the spindle apparatus. The establishment of tension between sister chromatids is essential for quenching a checkpoint kinase signal generated from kinetochores lacking microtubule attachment or tension. How the centromere chromatin spring is organized and functions as a tensiometer is largely unexplored. We have discovered that centromere chromatin loops generate an extensional/poleward force sufficient to release nucleosomes proximal to the spindle axis. This study describes how the physical consequences of DNA looping directly underlie the biological mechanism for sister centromere separation and the spring-like properties of the centromere in mitosis. © 2015 Lawrimore et al.

  20. Expression of a chimeric CSF1R-LTK mediates ligand-dependent neurite outgrowth.

    PubMed

    Yamada, Shigeru; Nomura, Takashi; Takano, Kota; Fujita, Satoshi; Miyake, Masato; Miyake, Jun

    2008-11-19

    In an earlier screening, we identified several genes for kinases that might control the extension of neurites. One of these genes encoded a leukocyte tyrosine kinase (LTK), which is a receptor tyrosine kinase whose ligands remain to be identified. To examine the possible role of this LTK in neurite outgrowth, we constructed a chimeric receptor, in which the extracellular domain of the receptor for colony-stimulating factor-1 was fused to the cytoplasmic domain of LTK, which allowed the selective activation of LTK by colony-stimulating factor-1. Our studies using this chimeric receptor suggest that activation of the tyrosine kinase activity of LTK is sufficient to promote neurite outgrowth through pathways that include reactions catalyzed by phosphatidylinositol 3-kinase and MAPK.

  1. GEFs and Rac GTPases control directional specificity of neurite extension along the anterior–posterior axis

    PubMed Central

    Zheng, Chaogu; Diaz-Cuadros, Margarete; Chalfie, Martin

    2016-01-01

    Although previous studies have identified many extracellular guidance molecules and intracellular signaling proteins that regulate axonal outgrowth and extension, most were conducted in the context of unidirectional neurite growth, in which the guidance cues either attract or repel growth cones. Very few studies addressed how intracellular signaling molecules differentially specify bidirectional outgrowth. Here, using the bipolar PLM neurons in Caenorhabditis elegans, we show that the guanine nucleotide exchange factors (GEFs) UNC-73/Trio and TIAM-1 promote anterior and posterior neurite extension, respectively. The Rac subfamily GTPases act downstream of the GEFs; CED-10/Rac1 is activated by TIAM-1, whereas CED-10 and MIG-2/RhoG act redundantly downstream of UNC-73. Moreover, these two pathways antagonize each other and thus regulate the directional bias of neuritogenesis. Our study suggests that directional specificity of neurite extension is conferred through the intracellular activation of distinct GEFs and Rac GTPases. PMID:27274054

  2. Reduced Neurite Density in Neuronal Cell Cultures Exposed to Serum of Patients with Bipolar Disorder

    PubMed Central

    Wollenhaupt-Aguiar, Bianca; Pfaffenseller, Bianca; Chagas, Vinicius de Saraiva; Castro, Mauro A A; Passos, Ives Cavalcante; Kauer-Sant’Anna, Márcia; Kapczinski, Flavio

    2016-01-01

    Background: Increased inflammatory markers and oxidative stress have been reported in serum among patients with bipolar disorder (BD). The aim of this study is to assess whether biochemical changes in the serum of patients induces neurotoxicity in neuronal cell cultures. Methods: We challenged the retinoic acid-differentiated human neuroblastoma SH-SY5Y cells with the serum of BD patients at early and late stages of illness and assessed neurite density and cell viability as neurotoxic endpoints. Results: Decreased neurite density was found in neurons treated with the serum of patients, mostly patients at late stages of illness. Also, neurons challenged with the serum of late-stage patients showed a significant decrease in cell viability. Conclusions: Our findings showed that the serum of patients with bipolar disorder induced a decrease in neurite density and cell viability in neuronal cultures. PMID:27207915