Mechanical and Electrical Responses of the Squid Giant Axon to Simple Elongation

1993 ◽  
Vol 115 (1) ◽  
pp. 13-22 ◽  
Author(s):  
J. A. Galbraith ◽  
L. E. Thibault ◽  
D. R. Matteson
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Cell Model ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Nerve Tissue ◽  
Resting Potential ◽  
Nonlinear Load ◽  
Functional Changes

There is a limited amount of information available on the mechanical and functional response of the nervous system to loading. While deformation of cerebral, spinal, or peripheral nerve tissue can have particularly severe consequences, most research in this area has concentrated on either demonstrating in-vivo functional changes and disclosing the effected anatomical pathways, or describing material deformations of the composite structure. Although such studies have successfully produced repeatable traumas, they have not addressed the mechanisms of these mechanically induced injuries. Therefore, a single cell model is required in order to gain further understanding of this complex phenomena. An isolated squid giant axon was subjected to controlled uniaxial loading and its mechanical and physiological responses were monitored with an instrument specifically designed for these experiments. These results determined that the mechanical properties of the isolated axon are similar to those of other soft tissues, and include features such as a nonlinear load-deflection curve and a hysteresis loop upon unloading. The mechanical response was modeled with the quasi-linear viscoelastic theory (Fung, 1972). The physiological response of the axon to quasi-static loading was a small reversible hyperpolarization; however, as the rate of loading was increased, the axon depolarized and the magnitude and the time needed to recover to the original resting potential increased in a nonlinear fashion. At elongations greater than twenty percent an irreversible injury occurs and the membrane potential does not completely recover to baseline.

scholarly journals DEMONSTRATION OF TWO STABLE POTENTIAL STATES IN THE SQUID GIANT AXON UNDER TETRAETHYLAMMONIUM CHLORIDE

1957 ◽  
Vol 40 (6) ◽  
pp. 859-885 ◽  
Author(s):  
Ichiji Tasaki ◽  
Susumu Hagiwara
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Membrane Conductance ◽  
Giant Axon ◽  
Membrane Resistance ◽  
Squid Giant Axon ◽  
Resting Potential ◽  
Unstable State ◽  
Stable States ◽  
Tetraethylammonium Chloride

1. Intracellular injection of tetraethylammonium chloride (TEA) into a giant axon of the squid prolongs the duration of the action potential without changing the resting potential (Fig. 3). The prolongation is sometimes 100-fold or more. 2. The action potential of a giant axon treated with TEA has an initial peak followed by a plateau (Fig. 3). The membrane resistance during the plateau is practically normal (Fig. 4). Near the end of the action potential, there is an apparent increase in the membrane resistance (Fig. 5D and Fig. 6, right). 3. The phenomenon of abolition of action potentials was demonstrated in the squid giant axon treated with TEA (Fig. 7). Following an action potential abolished in its early phase, there is no refractoriness (Fig. 8). 4. By the method of voltage clamp, the voltage-current relation was investigated on normal squid axons as well as on axons treated with TEA (Figs. 9 and 10). 5. The presence of stable states of the membrane was demonstrated by clamping the membrane potential with two voltage steps (Fig. 11). Experimental evidence was presented showing that, in an "unstable" state, the membrane conductance is not uniquely determined by the membrane potential. 6. The effect of low sodium water was investigated in the axon treated with TEA (Fig. 12). 7. The similarity between the action potential of a squid axon under TEA and that of the vertebrate cardiac muscle was stressed. The experimental results were interpreted as supporting the view that there are two stable states in the membrane. Initiation and abolition of an action potential were explained as transitions between the two states.

scholarly journals Mechanical Response Changes in Porcine Tricuspid Valve Anterior Leaflet Under Osmotic-Induced Swelling

2019 ◽  
Vol 6 (3) ◽  
pp. 70 ◽  
Author(s):  
Samuel D. Salinas ◽  
Margaret M. Clark ◽  
Rouzbeh Amini
Keyword(s):  
Tricuspid Valve ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Control Group ◽  
Anterior Leaflet ◽  
Buffer Solution ◽  
Tissue Samples ◽  
The Impact

Since many soft tissues function in an isotonic in-vivo environment, it is expected that physiological osmolarity will be maintained when conducting experiments on these tissues ex-vivo. In this study, we aimed to examine how not adhering to such a practice may alter the mechanical response of the tricuspid valve (TV) anterior leaflet. Tissue specimens were immersed in deionized (DI) water prior to quantification of the stress–strain responses using an in-plane biaxial mechanical testing device. Following a two-hour immersion in DI water, the tissue thickness increased an average of 107.3% in the DI water group compared to only 6.8% in the control group, in which the tissue samples were submerged in an isotonic phosphate buffered saline solution for the same period of time. Tissue strains evaluated at 85 kPa revealed a significant reduction in the radial direction, from 34.8% to 20%, following immersion in DI water. However, no significant change was observed in the control group. Our study demonstrated the impact of a hypo-osmotic environment on the mechanical response of TV anterior leaflet. The imbalance in ions leads to water absorption in the valvular tissue that can alter its mechanical response. As such, in ex-vivo experiments for which the native mechanical response of the valves is important, using an isotonic buffer solution is essential.

scholarly journals Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon

1961 ◽  
Vol 45 (1) ◽  
pp. 93-103 ◽  
Author(s):  
William J. Adelman ◽  
John W. Moore
Keyword(s):  
Sea Water ◽  
Giant Axon ◽  
Sodium Concentration ◽  
Squid Giant Axon ◽  
Ion Concentration ◽  
Resting Potential ◽  
Slow Increase ◽  
Sodium Permeability ◽  
Sodium Accumulation ◽  
Sodium Flux

Voltage clamp measurements of the sodium potential have been made on the resting squid giant axon to study the effect of variations in external divalent ion concentration upon net sodium flux. From these measurements the intracellular sodium concentration and the net sodium inflow were calculated using the Nernst relation and constant activity coefficients. While an axon bathed in artificial sea water shows a slow increase in internal sodium concentration, the rate of sodium accumulation is increased about two times by reducing external calcium and magnesium concentrations to 0.1 times their normal values. The mean inward net sodium flux increases from a mean control value of 97 pmole/cm2 sec. to 186 pmole/cm2 sec. in low divalent solution. Associated with these effects of external divalent ion reduction are a marked decrease in action potential amplitude, little or no change in resting potential, and a shift along the voltage axis of the curve relating peak sodium conductance to membrane potential similar to that obtained by Frankenhaeuser and Hodgkin (1957). These results implicate divalent ions in long term (minutes to hours) sodium permeability.

scholarly journals Monomer-polymer equilibria in the axon: direct measurement of tubulin and actin as polymer and monomer in axoplasm.

1984 ◽  
Vol 98 (6) ◽  
pp. 2064-2076 ◽  
Author(s):  
J R Morris ◽  
R J Lasek
Keyword(s):  
Axonal Transport ◽  
Direct Measurement ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
The Other ◽  
Significant Fraction ◽  
Dissociation Reaction ◽  
Basic Principles

The monomer-polymer equilibria for tubulin and actin were analyzed for the cytoskeleton of the squid giant axon. Two methods were evaluated for measuring the concentrations of monomer, soluble (equilibrium) polymer, and stable polymer in extruded axoplasm. One method, the Kinetic Equilibration Paradigm ( KEP ), employs the basic principles of diffusion to distinguish freely diffusible monomer from proteins that are present in the form of polymer. The other method is pharmacological and employs either taxol or phalloidin to stabilize the microtubules and microfilaments, respectively. The results of the two methods agree and demonstrate that 22-36% of the tubulin and 41-47% of the actin are monomeric. The in vivo concentration of monomeric actin and tubulin were two to three times higher than the concentration required to polymerize these proteins in vitro, suggesting that assembly of these proteins is regulated by additional mechanisms in the axon. A significant fraction of the polymerized actin and tubulin in the axoplasm was stable microtubules and microfilaments, which suggests that the dissociation reaction is blocked at both ends of these polymers. These results are discussed in relationship to the axonal transport of the cytoskeleton and with regard to the ability of axons to change their shape in response to environmental stimuli.

scholarly journals The Effects of Several Alcohols on the Properties of the Squid Giant Axon

1964 ◽  
Vol 48 (2) ◽  
pp. 265-277 ◽  
Author(s):  
Clay M. Armstrong ◽  
Leonard Binstock
Keyword(s):  
Potassium Conductance ◽  
Membrane Conductance ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Sodium Ion ◽  
Ion Current ◽  
Resting Potential ◽  
Membrane Capacity ◽  
Monomolecular Films ◽  
Steady State Inactivation

The effects of several alcohols on the resting potential, action potential, and voltage-clamp currents of the squid giant axon have been measured. All the alcohols employed are similar in that they depress maximum sodium conductance much more than maximum potassium conductance. Octyl alcohol differs from the others (C2 through C5) in that it has less tendency to depolarize the axon. Depolarization is always accompanied by a decrease of gK near the resting potential, such that the ratio gK/gleak is decreased. Steady-state inactivation of the sodium ion current is unaffected by alcohols, as is membrane capacity. Resting membrane conductance is usually decreased by alcohols. The findings are discussed in relation to work on monomolecular films.

Swelling of Collagen-Hyaluronic Acid Tissue-Equivalents: An Experimental Model to Evaluate Residual Stress in Soft Tissues

2013 ◽  
Author(s):  
Victor K. Lai ◽  
Spencer P. Lake ◽  
Bumjun Kim ◽  
Emily M. Weiss ◽  
Robert T. Tranquillo ◽  
...  
Keyword(s):  
Residual Stress ◽  
Hyaluronic Acid ◽  
Type I Collagen ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Tensile Load ◽  
Type I ◽  
Swelling Properties ◽  
Tissue Equivalents

Collagen gel tissue-equivalents (TEs), which are simple model tissues with tunable properties, have been used to explore many properties of soft tissues, such as how structural and compositional properties affect mechanical function [1–4]. One aspect not captured in previous TE formulations is residual stress due to interactions among components, which has an important functional role in many tissues (e.g., blood vessels [5], ligaments [6], annulus fibrosus [7]). Since the in vivo stress state of native tissues is not easily replicated in TE fabrication, a different method for “pre-stressing” collagen networks of TEs was necessary. To this end, co-gel TEs were fabricated by adding hyaluronic acid (HA) to reconstituted Type-I collagen (Col) gels. When placed in solutions of varying osmolarity, HA-Col TEs swell as the HA binds water, which in turn will stretch (and stress) the collagen network. In this way, TEs with residual stress (i.e., pre-stressed collagen fibers) can be fabricated and evaluated in order to elucidate relationships between residual stress and functional properties. Therefore, the goals of the present study were to fabricate HA-Col TEs, make initial measurements of their swelling properties, and quantify the mechanical response and changes in microstructural organization under applied tensile load.

scholarly journals EFFECTS OF EXTERNAL IONS ON MEMBRANE POTENTIALS OF A LOBSTER GIANT AXON

1958 ◽  
Vol 41 (3) ◽  
pp. 529-542 ◽  
Author(s):  
John C. Dalton
Keyword(s):  
Action Potential ◽  
Sea Water ◽  
Giant Axon ◽  
Membrane Potentials ◽  
Squid Giant Axon ◽  
Resting Potential ◽  
Magnesium Concentration ◽  
Constant Field ◽  
Order Of Magnitude ◽  
External Calcium

The effects of varying external concentrations of normally occurring cations on membrane potentials in the lobster giant axon have been studied and compared with data presently available from the squid giant axon. A decrease in the external concentration of sodium ions causes a reversible reduction in the amplitude of the action potential and its rate of rise. No effect on the resting potential was detected. The changes are of the same order of magnitude, but greater than would be predicted for an ideal sodium electrode. Increase in external potassium causes a decrease in resting potential, and a decrease in potassium causes an increase in potential. The data so obtained are similar to those which have been reported for the squid giant axon, and cannot be exactly fitted to the Goldman constant field equation. Lowering external calcium below 25 mM causes a reduction in resting and action potentials, and the occasional occurrence of repetitive activity. The decrease in action potential is not solely attributable to a decrease in resting potential. Increase of external calcium from 25 to 50 mM causes no change in transmembrane potentials. Variations of external magnesium concentration between zero and 50 mM had no measurable effect on membrane potentials. These studies on membrane potentials do not indicate a clear choice between the use of sea water and Cole's perfusion solution as the better external medium for studies on lobster nerve.

scholarly journals Resting and Action Potentials of the Squid Giant Axon in Vivo

1960 ◽  
Vol 43 (5) ◽  
pp. 961-970 ◽  
Author(s):  
John W. Moore ◽  
Kenneth S. Cole
Keyword(s):  
Sea Water ◽  
Giant Axon ◽  
Blood Oxygenation ◽  
Resting Potential ◽  
Liquid Junction ◽  
Axon Membrane ◽  
Nernst Potential ◽  
Initial Action ◽  
Calculated Liquid

Blood oxygenation and circulation were maintained in Loligo pealii for several hours by a strong flow of sea water over both gills on the open, flat mantle. Potentials were measured with a 3 M KCl-filled glass microelectrode penetrating the giant axon membrane. An hour or more after the mantle was opened, the potentials were similar to those observed in excised axons and in preparations without circulation; spike height 100 mv.; undershoot 12 mv., decaying at 6 v./sec.; resting potential 63 mv. However, the earliest (20 minute) resting potentials were up to 70 mv. and 73 mv. Occasional initial action potential measurements (40 to 50 minute) showed a decay of the undershoot that was less than one-tenth the rate observed later. This suggests that in even better preparations there would be no decay, thereby increasing the resting potential and spike height by 12 mv. With the calculated liquid junction potential of 4 mv. the absolute resting potential in the "normal" axon in vivo is estimated to be about 77 mv., which is close to the Nernst potential for the potassium ratio between squid blood and axoplasm. The differences between such a normal axon and the usual isolated axon can be accounted for by a negligible leakage conductance in the normal axon.

Neurofilaments and Paired Helical Filaments

1985 ◽  
Vol 43 ◽  
pp. 740-743
Author(s):  
J. Metuzals
Keyword(s):  
Animal Model ◽  
Posttranslational Modifications ◽  
Posttranslational Modification ◽  
Giant Axon ◽  
Paired Helical Filaments ◽  
Squid Giant Axon ◽  
In Vitro Experiments ◽  
Thin Sections ◽  
Structural Relationships

It has been demonstrated that the neurofibrillary tangles in biopsies of Alzheimer patients, composed of typical paired helical filaments (PHF), consist also of typical neurofilaments (NF) and 15nm wide filaments. Close structural relationships, and even continuity between NF and PHF, have been observed. In this paper, such relationships are investigated from the standpoint that the PHF are formed through posttranslational modifications of NF. To investigate the validity of the posttranslational modification hypothesis of PHF formation, we have identified in thin sections from frontal lobe biopsies of Alzheimer patients all existing conformations of NF and PHF and ordered these conformations in a hypothetical sequence. However, only experiments with animal model preparations will prove or disprove the validity of the interpretations of static structural observations made on patients. For this purpose, the results of in vitro experiments with the squid giant axon preparations are compared with those obtained from human patients. This approach is essential in discovering etiological factors of Alzheimer's disease and its early diagnosis.

Biological and biomedical applications of collagenous biomaterials

1990 ◽  
Vol 48 (3) ◽  
pp. 856-857
Author(s):  
Yasushi P. Kato ◽  
Michael G. Dunn ◽  
Frederick H. Silver ◽  
Arthur J. Wasserman
Keyword(s):  
Biomedical Applications ◽  
Soft Tissues ◽  
Collagen Fibers ◽  
Bone Collagen ◽  
Cover Slip ◽  
Fibroblast Migration ◽  
Cellular Expression ◽  
Defect Repair

Collagenous biomaterials have been used for growing cells in vitro as well as for augmentation and replacement of hard and soft tissues. The substratum used for culturing cells is implicated in the modulation of phenotypic cellular expression, cellular orientation and adhesion. Collagen may have a strong influence on these cellular parameters when used as a substrate in vitro. Clinically, collagen has many applications to wound healing including, skin and bone substitution, tendon, ligament, and nerve replacement. In this report we demonstrate two uses of collagen. First as a fiber to support fibroblast growth in vitro, and second as a demineralized bone/collagen sponge for radial bone defect repair in vivo.For the in vitro study, collagen fibers were prepared as described previously. Primary rat tendon fibroblasts (1° RTF) were isolated and cultured for 5 days on 1 X 15 mm sterile cover slips. Six to seven collagen fibers, were glued parallel to each other onto a circular cover slip (D=18mm) and the 1 X 15mm cover slip populated with 1° RTF was placed at the center perpendicular to the collagen fibers. Fibroblast migration from the 1 x 15mm cover slip onto and along the collagen fibers was measured daily using a phase contrast microscope (Olympus CK-2) with a calibrated eyepiece. Migratory rates for fibroblasts were determined from 36 fibers over 4 days.

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