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.

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 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 Ca2+ influx and neurite growth in response to purified N-cadherin and laminin.

1994 ◽  
Vol 127 (5) ◽  
pp. 1461-1475 ◽  
Author(s):  
J L Bixby ◽  
G B Grunwald ◽  
R J Bookman
Keyword(s):  
Single Cells ◽  
Neurite Growth ◽  
Growth Cones ◽  
Signaling Mechanisms ◽  
Highly Sensitive ◽  
Voltage Dependent ◽  
Cell Type Specific ◽  
Influx Pathways ◽  
Neuronal Growth Cones ◽  
Fibroblastic Cells

The signaling mechanisms underlying neurite growth induced by cadherins and integrins are incompletely understood. In our experiments, we have examined these mechanisms using purified N-cadherin and laminin (LN). We find that unlike the neurite growth induced by fibroblastic cells expressing transfected N-cadherin (Doherty, P., and F.S. Walsh. 1992. Curr. Opin. Neurobiol. 2:595-601), growth induced by purified N-cadherin in chick ciliary ganglion (CG), sensory, or forebrain neurons is not sensitive to inhibition by pertussis toxin. Using fura-2 imaging of single cells, we show that soluble N-cadherin induces Ca2+ increases in CG neuron cell bodies, and, importantly, in growth cones. In contrast, N-cadherin can induce Ca2+ decreases in glial cells. N-cadherin-induced neuronal Ca2+ responses are sensitive to Ni2+, but are relatively insensitive to diltiazem and omega-conotoxin. Similarly, neurite growth induced by purified N-cadherin is inhibited by Ni2+, but is unaffected by diltiazem and conotoxin. Soluble LN also induced small Ca2+ responses in CG neurons. LN-induced neurite growth, like that induced by N-cadherin, is insensitive to diltiazem and conotoxin, but is highly sensitive to Ni2+ inhibition. K+ depolarization experiments suggest that voltage-dependent Ca2+ influx pathways in CG neurons (cell bodies and growth cones) are largely blocked by the combination of diltiazem and Ni2+. Our results demonstrate that cadherin signaling involves cell type-specific Ca2+ changes in responding cells, and in particular, that N-cadherin can cause Ca2+ increases in neuronal growth cones. Our findings are consistent with the current idea that distinct neuronal transduction pathways exist for cell adhesion molecules compared with integrins, but suggest that the involvement of Ca2+ signals in both of these pathways is more complex than previously appreciated.

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.

Optimization of pulse train duration for the electrical stimulation of a skeletal muscle ventricle in the dog

1990 ◽  
Vol 18 (5) ◽  
pp. 467-478 ◽  
Author(s):  
Stephen F. Badylak ◽  
Jerry E. Wessale ◽  
Leslie A. Geddes ◽  
Wolfgang Janas
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Pulse Train ◽  
Train Duration ◽  
Stimulation Of

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 Effects of electrical stimulation on isolated rodent gastric smooth muscle cells evaluated via a joint computational simulation and experimental approach

2009 ◽  
Vol 297 (4) ◽  
pp. G672-G680 ◽  
Author(s):  
P. Du ◽  
S. Li ◽  
G. O'Grady ◽  
L. K. Cheng ◽  
A. J. Pullan ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Electrical Stimulation ◽  
Pulse Train ◽  
Pulse Width ◽  
Computational Simulation ◽  
Minimum Energy ◽  
Experimental Studies ◽  
Single Pulse ◽  
Plateau Phase ◽  
Wide Range

Gastric electrical stimulation (GES) involves the delivery of electrical impulses to the stomach for therapeutic purposes. New GES protocols are needed that are optimized for improved motility outcomes and energy efficiency. In this study, a biophysically based smooth muscle cell (SMC) model was modified on the basis of experimental data and employed in conjunction with experimental studies to define the effects of a large range of GES protocols on individual SMCs. For the validation studies, rat gastric SMCs were isolated and subjected to patch-clamp analysis during stimulation. Experimental results were in satisfactory agreement with simulation results. The results define the effects of a wide range of GES parameters (pulse width, amplitude, and pulse-train frequency) on isolated SMCs. The minimum pulse width required to invoke a supramechanical threshold response from SMCs (defined at −30 mV) was 65 ms (at 250-pA amplitude). The minimum amplitude required to invoke this threshold was 75 pA (at 1,000-ms pulse width). The amplitude of the invoked response beyond this threshold was proportional to the stimulation amplitude. A high-frequency train of stimuli (40 Hz; 10 ms, 150 pA) could invoke and maintain the SMC plateau phase while requiring 60% less power and accruing ∼30% less intracellular Ca2+ concentration during the plateau phase than a comparable single-pulse protocol could in a demonstrated example. Validated computational simulations are an effective strategy for efficiently identifying effective minimum-energy GES protocols, and pulse-train protocols may also help to reduce the power consumption of future GES devices.

Control of secretion in anterior pituitary cells--linking ion channels, messengers and exocytosis

1988 ◽  
Vol 139 (1) ◽  
pp. 287-316
Author(s):  
W. T. Mason ◽  
S. R. Rawlings ◽  
P. Cobbett ◽  
S. K. Sikdar ◽  
R. Zorec ◽  
...  
Keyword(s):  
Ion Channels ◽  
Intracellular Calcium ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Cell Types ◽  
Pituitary Cell ◽  
Pituitary Cells ◽  
Calcium Activity ◽  
Anterior Pituitary Cells ◽  
Voltage Dependent

Normal anterior pituitary cells, in their diversity and heterogeneity, provide a rich source of models for secretory function. However, until recently they have largely been neglected in favour of neoplastic, clonal tumour cell lines of pituitary origin, which have enabled a number of studies on supposedly homogeneous cell types. Because many of these lines appear to lack key peptide and neurotransmitter receptors, as well as being degranulated with accompanying abnormal levels of secretion, we have developed a range of normal primary anterior pituitary cell cultures using dispersion and enrichment techniques. By studying lactotrophs, somatotrophs and gonadotrophs we have revealed a number of possible transduction mechanisms by which receptors for hypothalamic peptides and neurotransmitters may control secretion. In particular, the transduction events controlling secretion from pituitary cells may differ fundamentally from those found in other cell types. Patch-clamp recordings in these various pituitary cell preparations have revealed substantial populations of voltage-dependent Na+, Ca2+ and K+ channels which may support action potentials in these cells. Although activation of these channels may gate Ca2+ entry to the cells under some conditions, our evidence taken with that of other laboratories suggests that peptide-receptor interactions leading to hormone secretion occur independently of significant membrane depolarization. Rather, secretion of hormone and rises in intracellular calcium measured with new probes for intracellular calcium activity, can occur in response to hypothalamic peptide activation in the absence of substantial changes in membrane potential. These changes in intracellular calcium activity almost certainly depend on both intracellular and extracellular calcium sources. In addition, strong evidence of a role for multiple intracellular receptors and modulators in the secretory event suggests we should consider the plasma membrane channels important for regulation of hormone secretion to be predominantly agonist-activated, rather than of the more conventional voltage-dependent type. Likewise, evidence from new methods for recording single ion channels suggests the existence of intracellular sites for channel modulation, implying they too may play an important role in secretory regulation. We shall consider new data and new technology which we hope will provide key answers to the many intriguing questions surrounding the control of pituitary hormone secretion. We shall highlight our work with recordings of single ion channels activated by peptides, and recent experiments using imaging of intracellular ionized free calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Characterization of receptors mediating the actions of dopamine on an identified inhibitory motoneurone of the cockroach

1991 ◽  
Vol 155 (1) ◽  
pp. 203-217 ◽  
Author(s):  
J. P. Davis ◽  
R. M. Pitman
Keyword(s):  
Periplaneta Americana ◽  
Voltage Dependence ◽  
Negative Resistance ◽  
Membrane Potentials ◽  
Dopaminergic Agonists ◽  
Current Voltage ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Ly 171555 ◽  
Relationship Of

1. The effects of a number of dopaminergic agonists and antagonists upon the soma of a prothoracic inhibitory motoneurone of the cockroach (Periplaneta americana) have been recorded under voltage-clamp conditions. 2. Dopamine generates inward currents that are extremely voltage-dependent: currents increase rapidly at membrane potentials more negative than about −120 to −150 mV and also show a peak at membrane potentials of approximately −20 mV. As a result of this voltage-dependence, dopamine induces a region of negative resistance in the current-voltage relationship of the neurone. 3. The dopaminergic agonists apomorphine, bromocriptine, ergometrine and A-6,7-DTN mimic the action of dopamine on this neurone, all having a similar voltage-dependence to that of dopamine. The selective D-1 receptor agonist SK&F82526 and the D-2 agonist LY 171555, however, were both inactive on the preparation. 4. Responses to dopamine were suppressed by a number of D-1 and D-2 receptor antagonists, indicating that the pharmacological profile of the dopamine-sensitive receptor in this insect preparation is different from that of vertebrate dopamine receptors.

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