scholarly journals A cytomechanical investigation of neurite growth on different culture surfaces.

1992 ◽  
Vol 118 (3) ◽  
pp. 655-661 ◽  
Author(s):  
P Lamoureux ◽  
J Zheng ◽  
R E Buxbaum ◽  
S R Heidemann
Keyword(s):  
Sensory Neurons ◽  
Growth Cone ◽  
Rate Sensitivity ◽  
Neurite Growth ◽  
Growth Cones ◽  
Elongation Rate ◽  
Collagen Type Iv ◽  
Mean Values ◽  
Axonal Elongation ◽  
Applied Tension

We have examined the relationship between tension, an intrinsic stimulator of axonal elongation, and the culture substrate, an extrinsic regulator of axonal elongation. Chick sensory neurons were cultured on three substrata: (a) plain tissue culture plastic; (b) plastic treated with collagen type IV; and (c) plastic treated with laminin. Calibrated glass needles were used to increase the tension loads on growing neurites. We found that growth cones on all substrata failed to detach when subjected to two to threefold and in some cases 5-10-fold greater tensions than their self-imposed rest tension. We conclude that adhesion to the substrate does not limit the tension exerted by growth cones. These data argue against a "tug-of-war" model for substrate-mediated guidance of growth cones. Neurite elongation was experimentally induced by towing neurites with a force-calibrated glass needle. On all substrata, towed elongation rate was proportional to applied tension above a threshold tension. The proportionality between elongation rate and tension can be regarded as the growth sensitivity of the neurite to tension, i.e., its growth rate per unit tension. On this basis, towed growth on all substrata can be described by the simple linear equation: elongation rate = sensitivity x (applied tension - tension threshold) The numerical values of tension thresholds and neurite sensitivities varied widely among different neurites. On all substrata, thresholds varied from near zero to greater than 200 mudynes, with some tendency for thresholds to cluster between 100 and 150 mudynes. Similarly, the tension sensitivity of neurites varied between 0.5 and 5.0 microns/h/mudyne. The lack of significant differences among sensitivity or threshold values on the various substrata suggest to use that the substratum does not affect the internal "set points" of the neurite for its response to tension. The growth cone of chick sensory neurons is known to pull on its neurite. The simplest cytomechanical model would assume that both growth cone-mediated elongation and towed growth are identical as far as tension input and elongation rate are concerned. We used the equation above and mean values for thresholds and sensitivity from towing experiments to predict the mean growth cone-mediated elongation rate based on mean rest tensions. These predictions are consistent with the observed mean values.

scholarly journals The role of microtubules in growth cone turning at substrate boundaries.

1995 ◽  
Vol 128 (1) ◽  
pp. 127-137 ◽  
Author(s):  
E Tanaka ◽  
M W Kirschner
Keyword(s):  
Growth Cone ◽  
Collagen Type ◽  
Axon Growth ◽  
Growth Cones ◽  
Collagen Type Iv ◽  
Early Step ◽  
Growth Cone Collapse ◽  
Type Iv ◽  
And Behaviors

To understand the role of microtubules in growth cone turning, we observed fluorescently labeled microtubules in neurons as they encountered a substrate boundary. Neurons growing on a laminin-rich substrate avoided growing onto collagen type IV. Turning growth cones assumed heterogeneous morphologies and behaviors that depended primarily in their extent of adhesion to the substrate. We grouped these behaviors into three categories-sidestepping, motility, and growth-mediated reorientation. In sidestepping and motility-mediated reorientation, the growth cone and parts of the axon were not well attached to the substrate so the acquisition of an adherent lamella caused the entire growth cone to move away from the border and consequently reoriented the axon. In these cases, since the motility of the growth cone dominates its reorientation, the microtubules were passive, and reorientation occurred without significant axon growth. In growth-mediated reorientation, the growth cone and axon were attached to the substrate. In this case, microtubules reoriented within the growth cone to stabilize a lamella. Bundling of the reoriented microtubules was followed by growth cone collapse to form new axon, and further, polarized lamellipodial extension. These observations indicate that when the growth cone remains adherent to the substrate during turning, the reorientation and bundling of microtubules is an important, early step in growth cone turning.

scholarly journals Delayed Retraction of Filopodia in Gelsolin Null Mice

1997 ◽  
Vol 138 (6) ◽  
pp. 1279-1287 ◽  
Author(s):  
Mei Lu ◽  
Walter Witke ◽  
David J. Kwiatkowski ◽  
Kenneth S. Kosik
Keyword(s):  
Growth Cone ◽  
Hippocampal Neurons ◽  
Neurite Growth ◽  
Time Lapse ◽  
Growth Cones ◽  
Wild Type ◽  
Dynamic Studies ◽  
Shape Changes ◽  
Time Lapse Video ◽  
Cultured Hippocampal Neurons

Growth cones extend dynamic protrusions called filopodia and lamellipodia as exploratory probes that signal the direction of neurite growth. Gelsolin, as an actin filament-severing protein, may serve an important role in the rapid shape changes associated with growth cone structures. In wild-type (wt) hippocampal neurons, antibodies against gelsolin labeled the neurite shaft and growth cone. The behavior of filopodia in cultured hippocampal neurons from embryonic day 17 wt and gelsolin null (Gsn−) mice (Witke, W., A.H. Sharpe, J.H. Hartwig, T. Azuma, T.P. Stossel, and D.J. Kwiatkowski. 1995. Cell. 81:41–51.) was recorded with time-lapse video microscopy. The number of filopodia along the neurites was significantly greater in Gsn− mice and gave the neurites a studded appearance. Dynamic studies suggested that most of these filopodia were formed from the region of the growth cone and remained as protrusions from the newly consolidated shaft after the growth cone advanced. Histories of individual filopodia in Gsn− mice revealed elongation rates that did not differ from controls but an impaired retraction phase that probably accounted for the increased number of filopodia long the neutrite shaft. Gelsolin appears to function in the initiation of filopodial retraction and in its smooth progression.

scholarly journals Computational modeling of neurons: intensity-duration relationship of extracellular electrical stimulation for changes in intracellular calcium

2016 ◽  
Vol 115 (1) ◽  
pp. 602-616 ◽  
Author(s):  
Robert D. Adams ◽  
Rebecca K. Willits ◽  
Amy B. Harkins
Keyword(s):  
Electrical Stimulation ◽  
Intracellular Calcium ◽  
Growth Cone ◽  
Pulse Train ◽  
Neurite Growth ◽  
Growth Cones ◽  
Train Duration ◽  
Voltage Dependent ◽  
Duration Relationship ◽  
Relationship Of

In many instances of extensive nerve damage, the injured nerve never adequately heals, leaving lack of nerve function. Electrical stimulation (ES) has been shown to increase the rate and orient the direction of neurite growth, and is a promising therapy. However, the mechanism in which ES affects neuronal growth is not understood, making it difficult to compare existing ES protocols or to design and optimize new protocols. We hypothesize that ES acts by elevating intracellular calcium concentration ([Ca2+]i) via opening voltage-dependent Ca2+ channels (VDCCs). In this work, we have created a computer model to estimate the ES Ca2+ relationship. Using COMSOL Multiphysics, we modeled a small dorsal root ganglion (DRG) neuron that includes one Na+ channel, two K+ channels, and three VDCCs to estimate [Ca2+]i in the soma and growth cone. As expected, the results show that an ES that generates action potentials (APs) can efficiently raise the [Ca2+]i of neurons. More interestingly, our simulation results show that sub-AP ES can efficiently raise neuronal [Ca2+]i and that specific high-voltage ES can preferentially raise [Ca2+]i in the growth cone. The intensities and durations of ES on modeled growth cone calcium rise are consistent with directionality and orientation of growth cones experimentally shown by others. Finally, this model provides a basis to design experimental ES pulse parameters, including duration, intensity, pulse-train frequency, and pulse-train duration to efficiently raise [Ca2+]i in neuronal somas or growth cones.

NrCAM, cerebellar granule cell receptor for the neuronal adhesion molecule F3, displays an actin-dependent mobility in growth cones

1999 ◽  
Vol 112 (18) ◽  
pp. 3015-3027 ◽  
Author(s):  
C. Faivre-Sarrailh ◽  
J. Falk ◽  
E. Pollerberg ◽  
M. Schachner ◽  
G. Rougon
Keyword(s):  
Growth Cone ◽  
Actin Filaments ◽  
Cerebellar Granule Cells ◽  
Leading Edge ◽  
Growth Cones ◽  
Inhibitory Effect ◽  
Immunoglobulin Superfamily ◽  
Cerebellar Granule ◽  
Axonal Elongation ◽  
Neuronal Adhesion

The neuronal adhesion glycoprotein F3 is a multifunctional molecule of the immunoglobulin superfamily that displays heterophilic binding activities. In the present study, NrCAM was identified as the functional receptor mediating the inhibitory effect of F3 on axonal elongation from cerebellar granule cells. F3Fc-conjugated microspheres binding to neuronal growth cones resulted from heterophilic interaction with NrCAM but not with L1. Time-lapse video-microscopy indicated that F3Fc beads bind at the leading edge and move retrogradely to reach the base of the growth cone within a lapse of 30–60 seconds. Such velocity (5.7 microm/minute) is consistent with a coupling between F3 receptors and the retrograde flow of actin filaments. When actin filaments were disrupted by cytochalasin B, the F3Fc beads remained immobile at the leading edge. The retrograde mobility appeared to be dependent on NrCAM clustering since it was induced upon binding with cross-linked but not dimeric F3Fc chimera. These data indicate that F3 may control growth cone motility by modulating the linkage of its receptor, NrCAM, to the cytoskeleton. They provide further insights into the mechanisms by which GPI-anchored adhesion molecules may exert an inhibitory effect on axonal elongation.

scholarly journals A Src-astic response to mounting tension

2001 ◽  
Vol 155 (3) ◽  
pp. 327-330 ◽  
Author(s):  
Daniel G. Jay
Keyword(s):  
Growth Cone ◽  
Local Environment ◽  
Growth Cones ◽  
Feedback Mechanism ◽  
Critical Question ◽  
Guidance Cues ◽  
Applied Tension ◽  
Nerve Growth Cone ◽  
Positive Feedback Mechanism ◽  
Guidance Information

The nerve growth cone binds to a complex array of guidance cues in its local environment that influence cytoskeletal interactions to control the direction of subsequent axon outgrowth. How this occurs is a critical question and must certainly involve signal transduction pathways. The paper by Suter and Forscher (2001)(this issue) begins to address how one such pathway, an Src family tyrosine kinase, enhances cytoskeletal linkage to apCAM, a permissive extracellular cue for Aplysia growth cones. Interestingly, they show that applied tension increases this kinase's localized phosphorylation that in turn further strengthens linkage. This suggests a potential positive feedback mechanism for amplifying and discriminating guidance information to guide growth cone motility.

scholarly journals Differences in the organization of actin in the growth cones compared with the neurites of cultured neurons from chick embryos.

1983 ◽  
Vol 97 (4) ◽  
pp. 963-973 ◽  
Author(s):  
P C Letourneau
Keyword(s):  
Growth Cone ◽  
Actin Filaments ◽  
Electron Microscopic Observation ◽  
Neurite Growth ◽  
Growth Cones ◽  
Chick Embryos ◽  
Heavy Meromyosin ◽  
Electron Microscopic ◽  
Cytochemical Localization ◽  
Triton X

Sensory neurons from chick embryos were cultured on substrata that support neurite growth, and were fixed and prepared for both cytochemical localization of actin and electron microscopic observation of actin filaments in whole-mounted specimens. Samples of cells were treated with the detergent Triton X-100 before, during, or after fixation with glutaraldehyde to determine the organization of actin in simpler preparations of extracted cytoskeletons. Antibodies to actin and a fluorescent derivative of phallacidin bound strongly to the leading margins of growth cones, but in neurites the binding of these markers for actin was very weak. This was true in all cases of Triton X-100 treatment, even when cells were extracted for 4 min before fixation. In whole-mounted cytoskeletons there were bundles and networks of 6-7-nm filaments in leading edges of growth cones but very few 6-7-n filaments were present among the microtubules and neurofilaments in the cytoskeletons of neurites. These filaments, which are prominent in growth cones, were identified as actin because they were stabilized against detergent extraction by the presence of phallacidin or the heavy meromyosin and S1 fragments of myosin. In addition, heavy meromyosin and S1 decorated these filaments as expected for binding to F-actin. Microtubules extended into growth cone margins and terminated within the network of actin filaments and bundles. Interactions between microtubule ends and these actin filaments may account for the frequently observed alignment of microtubules with filopodia at the growth cone margins.

scholarly journals Rac is required for growth cone function but not neurite assembly

1997 ◽  
Vol 110 (5) ◽  
pp. 635-641 ◽  
Author(s):  
P. Lamoureux ◽  
Z.F. Altun-Gultekin ◽  
C. Lin ◽  
J.A. Wagner ◽  
S.R. Heidemann
Keyword(s):  
Pc12 Cells ◽  
Growth Cone ◽  
Elongation Rate ◽  
Dominant Negative ◽  
Normal Density ◽  
Spontaneous Growth ◽  
Neurite Elongation ◽  
Dominant Negative Form ◽  
Applied Tension ◽  
Negative Form

Recent work has suggested that rac1 and other members of the rho family of small GTP-binding proteins play an important role in the formation of neural processes. We have explored the mechanism of this effect by comparing the spontaneous, growth cone-mediated growth and experimental tension-induced growth of axons in normal PC12 cells and in mutant cells expressing a dominant negative form of rac. PC12 that have been primed by exposure to NGF, but not naive PC12 cells, initiate a microtubule-rich process de novo in response to tension applied to cell body. As in chick sensory neurons, neurite elongation rate is proportional to applied tension above a threshold. Addition of cyclic AMP, which has been shown to rapidly augment NGF-induced neurite outgrowth in PC12, causes a rapid increase in the rate of neurite elongation at a given tension level. Expression of a dominant negative form of rac1 inhibits spontaneous, growth cone-mediated neurite elongation in response to NGF, but does not substantially affect tension-induced neurite elongation. That is, rac-deficient cells show a normal linear relationship between applied tension and elongation rate and the elongations contain a normal density of axial microtubules by immunofluorescent assay. Thus, rac1 is apparently required for the mechanisms that normally generate tension in an elongating neurite, but if this tension is provided from an outside source, then axonal elongation can proceed normally in rac1-deficient cells. We conclude that rac1 is required for the adhesive and motile function of growth cones rather than the assembly of neurites per se.

scholarly journals Mechanical tension produced by nerve cells in tissue culture

1979 ◽  
Vol 37 (1) ◽  
pp. 391-410 ◽  
Author(s):  
D. Bray
Keyword(s):  
Tissue Culture ◽  
Sensory Neurons ◽  
Growth Cone ◽  
High Probability ◽  
Growth Cones ◽  
Cultured Neurons ◽  
Mechanical Tension ◽  
Standard Methods

Evidence is presented that (a) the growth cone of cultured neurons can exert mechanical tension, and (b) that the direction of advance of the growth cone is determined by the tension existing between it and the rest of the cell. (a) The evidence that growth cones can pull comes from a vectorial analysis of the outlines of individually isolated sensory neurons. The angles formed in these outgrowths are very close to those of tension-generated networks anchored at their free ends and these values are restored shortly after an experimental displacement. The relative mechanical tension on each segment of an outgrowth can be calculated by standard methods and is found to decrease at each branch point. It appears to be correlated with the diameter of the fibre so that thicker fibres maintain more tension than thinner ones. (b) The influence of tension on the direction of advance of the growth cone is shown by 2 kinds of experient. If a growing neurite is pulled to one side with a microelectrode then the direction of its advance is changed immediately according to the new stress. If the mechanical tension on the growth cone of a neurite is released by amputation or displacement the growth cone is found to have a high probability of branching shortly afterwards. The ability of the growth cone to exert tension is discussed in relation to evidence that microspikes have contractile properties and in terms of the distribution of microfilaments within the neurite. It is suggested that the exertion of tension by a growth cone could serve to guide the neurite along paths of high adhesivity both in vitro and in vivo.

scholarly journals Increase in Growth Cone Size Correlates with Decrease in Neurite Growth Rate

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Yuan Ren ◽  
Daniel M. Suter
Keyword(s):  
Cell Culture ◽  
Growth Rate ◽  
Growth Cone ◽  
Cell Biology ◽  
Inverse Correlation ◽  
Neurite Growth ◽  
Growth Cones ◽  
Average Growth ◽  
Cellular Analysis ◽  
Large Growth

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

Sign in / Sign up

Export Citation Format

Share Document