Nerve growth in the absence of growth cone filopodia and the effects of a small applied electric field

1989 ◽  
Vol 93 (4) ◽  
pp. 715-721
Author(s):  
C.D. McCaig
Keyword(s):  
Electric Field ◽  
Growth Cone ◽  
Applied Electric Field ◽  
Slow Growth ◽  
Cytochalasin D ◽  
Nerve Growth ◽  
Guidance Cues ◽  
Turning Behaviour

Nerve orientation may involve a biasing of the distribution of tension at the growth cone. Chemical and electrical guidance cues cause more filopodia to appear on one side of the growth cone and this may determine turning behaviour. In a small applied electric field, filopodia predominate on the cathodal side of the growth cone and nerves turn towards the cathode. Removing all filopodia by treatment with cytochalasin D did not prevent nerves from continued slow growth and nerves still oriented towards the cathode. It is concluded that nerves can perform some types of orienting behaviour in the complete absence of filopodia.

Studies on the mechanism of embryonic frog nerve orientation in a small applied electric field

1989 ◽  
Vol 93 (4) ◽  
pp. 723-730
Author(s):  
C.D. McCaig
Keyword(s):  
Calcium Channels ◽  
Electric Field ◽  
Growth Cone ◽  
Applied Electric Field ◽  
Asymmetric Distribution ◽  
Pharmacological Agents ◽  
Nerve Growth ◽  
Drug Treatments ◽  
Turning Behaviour ◽  
Blockers Of Calcium Channels

The mechanism of nerve orientation in an applied electric field has been investigated using a number of pharmacological agents. Galvanotropism may depend on redistribution within the plasma membrane of integral membrane proteins (IMP); blocking this with concanavalin A inhibited orientation. Orientation may depend also on an influx of Ca2+; Co2+ and La3+ blockade of calcium channels inhibited turning in an electric field. Organic blockers of calcium channels did not influence orientation, suggesting that L-type Ca2+ channels may not be present at the growth cone. Procedures that may induce asymmetric entry of Ca2+ on the anodal side of cells caused a reversal of normal galvanotropism, with growth directed towards the anode. This may implicate local levels of cytoplasmic Ca2+ within the growth cone in controlling turning behaviour. An asymmetric distribution of filopodia precedes and may predict the direction of nerve growth in an electric field. Various pharmacological agents perturbed the distribution of filopodia in such a way that this did not reflect subsequent orientation. It is suggested that, normally, local Ca2+ increases and an asymmetry of filopodia operate together in determining orientation, but that filopodial activity is subordinate to and can be overriden by local Ca2+ levels in the growth cone. In addition, two of the drug treatments markedly increased rates of nerve growth, which may be of importance in nerve regeneration.

Electric fields, contact guidance and the direction of nerve growth

Development ◽  
1986 ◽  
Vol 94 (1) ◽  
pp. 245-255
Author(s):  
Colin D. McCaig
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Free Choice ◽  
Contact Guidance ◽  
Orthogonal Direction ◽  
Nerve Growth ◽  
Guidance Cues

Nerve orientation in response to electrical guidance cues in one direction and contact guidance cues in an orthogonal direction has been studied. Where neurites had a free choice between following contact guidance cues or electrical cues, the direction of nerve growth was determined predominantly by the vector of the applied electric field.

Nerve growth in a small applied electric field and the effects of pharmacological agents on rate and orientation

1990 ◽  
Vol 95 (4) ◽  
pp. 617-622
Author(s):  
C.D. McCaig
Keyword(s):  
Electric Field ◽  
Applied Electric Field ◽  
Ganglioside Gm1 ◽  
Normal Pattern ◽  
Pharmacological Agents ◽  
Rate Of Growth ◽  
Threefold Increase ◽  
Turning Behaviour ◽  
Rates Of Growth ◽  
Cyclase Activator

The rate of growth and orientation of embryonic Xenopus nerves exposed to pharmacological agents, to an applied electric field or to both simultaneously were studied. The adenyl cyclase activator forskolin (100 microM) induced a threefold increase in the rate of elongation, as did an electric field alone. Together, their effect in augmenting rate of growth was additive, but only at a concentration of 50 microM forskolin. The normal pattern of faster growth towards cathode than anode was not present in nerves treated with the lectin concanavalin A, which also inhibits normal turning behaviour towards the cathode. Nerve orientation towards the cathode and augmented rates of growth were found in the presence of forskolin or ganglioside GM1. It is suggested that a combined approach of drug treatment and an applied electric field may be useful in promoting nerve regeneration.

Integrated interactions between chondroitin sulphate proteoglycans and weak dc electric fields regulate nerve growth cone guidance in vitro

1997 ◽  
Vol 110 (16) ◽  
pp. 1957-1965
Author(s):  
L. Erskine ◽  
C.D. McCaig
Keyword(s):  
Electric Fields ◽  
Growth Cone ◽  
Chondroitin Sulphate ◽  
Side Chains ◽  
Keratan Sulphate ◽  
Nerve Growth ◽  
Guidance Cues ◽  
Chondroitin Sulphate Proteoglycans ◽  
Growth Cone Guidance

During development and regenerative growth, neuronal pathways are defined in part by several endogenous cues that collectively determine directed growth. The interactions between such cues largely are unknown. To address potential interactions, we have examined in vitro the combined effect on nerve growth of two endogenous growth cone guidance cues: chondroitin sulphate proteoglycans and weak dc electric fields. Addition to the culture medium of a chondroitin 6-sulphate/keratan sulphate containing PG (BNC-PG) markedly enhanced the cathodal re-orientation of embryonic Xenopus neurites in an electric field, whereas a proteoglycan containing chondroitin 4-sulphate (RC-PG) was inhibitory. These effects of BNC-PG and RC-PG were reproduced by their chondroitin sulphate glycosaminoglycan side chains alone. Chondroitin 6-sulphate or chondroitin 4-sulphate, respectively, enhanced and inhibited cathodally-directed nerve re-orientation. This was dependent on the integrity of the glycosaminoglycan chain structure; when digested into their disaccharide subunits both molecules became inactive. Keratan sulphate, a minor component of BNC-PG, was found to be inhibitory, whereas dermatan sulphate, an epimer of chondroitin 4-sulphate, had no effect. We conclude that in vitro specific interactions between these two nerve guidance cues do occur and that the specificity of the response is critically dependent on the charge pattern of the proteoglycans chondroitin sulphate side chains. The expression of a host of proteoglycans with differing glycosaminoglycan side chains varies in both time and place in the developing nervous system, thus the scope is vast for spatial and temporal modulation of nerve guidance by interacting cues.

LIQUID CRYSTLASLIGHT SCATTERING BY FLUCTUATIONS INDUCED BY AN APPLIED ELECTRIC FIELD IN A NEMATIC LIQUID CRYSTAL (APAPA)

1972 ◽  
Vol 33 (C1) ◽  
pp. C1-63-C1-67 ◽  
Author(s):  
M. BERTOLOTTI ◽  
B. DAINO ◽  
P. Di PORTO ◽  
F. SCUDIERI ◽  
D. SETTE
Keyword(s):  
Liquid Crystal ◽  
Electric Field ◽  
Nematic Liquid Crystal ◽  
Applied Electric Field

Improved technique for measuring mechanical deformations induced by an applied electric field to an organic insulator

2012 ◽  
Vol 15 (2-3) ◽  
pp. 127-139
Author(s):  
Tung Tran Anh ◽  
Laurent Berquez ◽  
Laurent Boudou ◽  
Juan Martinez-Vega ◽  
Alain Lacarnoy
Keyword(s):  
Electric Field ◽  
Applied Electric Field ◽  
Mechanical Deformations ◽  
Improved Technique

Solution for a Semi-Permeable Interface Crack in Elastic Dielectric/Piezoelectric Bimaterials

2008 ◽  
Vol 75 (1) ◽  
Author(s):  
Q. Li ◽  
Y. H. Chen
Keyword(s):  
Electric Field ◽  
Mechanical Loading ◽  
Interface Crack ◽  
Applied Electric Field ◽  
Crack Tip ◽  
Crack Model ◽  
Permeable Crack ◽  
Impermeable Crack ◽  
Silicon Oil ◽  
Elastic Dielectric

A semi-permeable interface crack in infinite elastic dielectric/piezoelectric bimaterials under combined electric and mechanical loading is studied by using the Stroh complex variable theory. Attention is focused on the influence induced from the permittivity of the medium inside the crack gap on the near-tip singularity and on the energy release rate (ERR). Thirty five kinds of such bimaterials are considered, which are constructed by five kinds of elastic dielectrics and seven kinds of piezoelectrics, respectively. Numerical results for the interface crack tip singularities are calculated. We demonstrate that, whatever the dielectric phase is much softer or much harder than the piezoelectric phase, the structure of the singular field near the semi-permeable interface crack tip in such bimaterials always consists of the singularity r−1∕2 and a pair of oscillatory singularities r−1∕2±iε. Calculated values of the oscillatory index ε for the 35 kinds of bimaterials are presented in tables, which are always within the range between 0.046 and 0.088. Energy analyses for five kinds of such bimaterials constructed by PZT-4 and the five kinds of elastic dielectrics are studied in more detail under four different cases: (i) the crack is electrically conducting, (ii) the crack gap is filled with air/vacuum, (iii) the crack gap is filled with silicon oil, and (iv) the crack is electrically impermeable. Detailed comparisons on the variable tendencies of the crack tip ERR against the applied electric field are given under some practical electromechanical loading levels. We conclude that the different values of the permittivity have no influence on the crack tip singularity but have significant influences on the crack tip ERR. We also conclude that the previous investigations under the impermeable crack model are incorrect since the results of the ERR for the impermeable crack show significant discrepancies from those for the semi-permeable crack, whereas the previous investigations under the conducting crack model may be accepted in a tolerant way since the results of the ERR show very small discrepancies from those for the semi-permeable crack, especially when the crack gap is filled with silicon oil. In all cases under consideration the curves of the ERR for silicon oil are more likely tending to those for the conducting crack rather than to those for air or vacuum. Finally, we conclude that the variable tendencies of the ERR against the applied electric field have an interesting load-dependent feature when the applied mechanical loading increases. This feature is due to the nonlinear relation between the normal electric displacement component and the applied electromechanical loadings from a quadratic equation.

Synergistic use of electroosmotic flow and magnetic forces for nucleic acid extraction

The Analyst ◽  
2020 ◽  
Vol 145 (6) ◽  
pp. 2412-2419 ◽  
Author(s):  
Rachel N. Deraney ◽  
Lindsay Schneider ◽  
Anubhav Tripathi
Keyword(s):  
Nucleic Acid ◽  
Electric Field ◽  
Microfluidic Chip ◽  
Applied Electric Field ◽  
Electroosmotic Flow ◽  
Acid Extraction ◽  
Nucleic Acid Extraction ◽  
Magnetic Forces ◽  
Extraction And Purification

NA extraction and purification utilitzing a microfluidic chip with applied electric field to induce electroosmotic flow opposite the magnetic NA-bound bead mix.

Sign in / Sign up

Export Citation Format

Share Document