Coordinated Excitation of Flexor Inhibitors in the Crayfish

1980 ◽  
Vol 86 (1) ◽  
pp. 187-195
Author(s):  
CHIKAO UYAMA ◽  
TAKASHI MATSUYAMA
Keyword(s):  
Giant Axon ◽  
Experimental Results ◽  
Abdominal Ganglion ◽  
Giant Axons ◽  
The Third ◽  
Nerve Cords

In isolated abdominal nerve cords of crayfish, the medial or lateral giant axons were stimulated at a position just rostral to the first abdominal ganglion. Recordings of the impulse sequences of the flexor inhibitor (FI) were made from the anterior five ganglia, three ganglia at a time. In 20% of our preparations, one giant axon impulse caused one to four FI impulses in every abdominal third root. An equal number of FI impulses were usually produced by each abdominal ganglion for any given stimulation. The earliest FI impulse was observed at the third root of the fourth ganglion. FI impulses occurred with increasing latencies rostrally and caudally from the fourth ganglion. The FI responses to medial and lateral giant axons stimulation were essentially equivalent. FI impulses were recorded from the rostral three abdominal ganglia, while the caudal ganglia were cut off one after another from the sixth to the third ganglion. Little change was noted until after the removal of the fourth ganglion, which usually caused all FI impulses to disappear. From these experimental results, we propose a model of central mechanisms for FI excitation.

Microelectrode Study of the Resting and Action Potentials of the Cockroach Giant Axon with Special Reference to the Role Played by the Nerve Sheath

1967 ◽  
Vol 47 (2) ◽  
pp. 357-373
Author(s):  
Y. PICHON ◽  
J. BOISTEL
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Maximum Rate ◽  
Diffusion Processes ◽  
Extracellular Fluid ◽  
Giant Axon ◽  
Resting Potential ◽  
Giant Axons ◽  
The Mean ◽  
Nerve Cords

1. The use of very fine-tipped and mechanically strong microelectrodes has allowed reliable recordings of resting and action potentials to be made in cockroach giant axons in sheathed and desheathed nerve cords. 2. When the microelectrode was withdrawn from a giant axon in an intact connective the first positive change in the potential from the resting level, was in most cases followed by a negative deflexion to the original zero level, the ‘sheath potential’. The values of this ‘sheath potential’ together with the resting potential, the action potential, the maximum rate of rise and maximum rate of fall of the action potential have been measured in three different salines. 3. In normal saline, resting potentials were lower in sheathed preparations (58·1 ± 55·4 mV.) than in desheathed ones (67·4 ± 6·2 mV.), whereas action potentials were higher in the former (103±5·9 mV.) than in the latter (85·9±4·6 mV.). 4. Elevation of K+ and Ca2+ concentrations in the saline to the haemolymph level resulted in a decrease of resting and action potentials in desheathed cords, to 57·3±5·3 mV. and 36·5±7·6 mV. respectively. No alterations in the membrane potentials were recorded in intact connectives bathed in this saline, the mean resting potential being 55·6±4·2 mV. and the mean action potential 107·9±6·0 mV. Local desheathing of the nerve cord led only to local disturbance of the resting and action potentials, thus indicating that diffusion processes along the extracellular spaces were very slow. 5. The use of a saline in which cation concentrations have been elevated to the extracellular level resulted in normal resting potentials (64·6±3·3 mV.) and action potentials (90·9±7·2 mV.) in desheathed cords, despite the relatively high potassium concentration (17·1 mM./l.). 6. Recordings of the maximum rates of rise and rates of fall showed that there was no significant modification in the shape of the action potential in these different experimental conditions. 7. The values of the ‘sheath potential’ were very variable from one impalement to another and it is suggested that this potential might be related to variations of the microelectrode tip potential bathed in different ionic solutions. 8. The low resting potentials and high action potentials of giant axons in intact nerve cords may result from an excess of inorganic cations in the extracellular fluid.

LED Display Image Correction Based on Computer Simulation

2012 ◽  
Vol 182-183 ◽  
pp. 1751-1755
Author(s):  
Xi Feng Zheng ◽  
Feng Chang
Keyword(s):  
Computer Simulation ◽  
Correction Method ◽  
Experimental Results ◽  
Image Correction ◽  
The Third

For the purposes of correcting the LED display image, a method based on computer simulation is proposed. First, the development of the LED display panel is introduced. Second, analyze the causes of the problem which image in LED display panel has serious high non-uniformity, and introduce the existed correction techniques which are used to reduce the non-uniformity of LED display image. Simultaneously, point out the ground for shortcomings of these techniques. Third, describe the principle of correction method based on computer simulation detail from two steps, which are the luminous collection and luminous copulation. Forth, describe the realization steps of this method in accordance with the third step. Finally, this method is supplied in a LED display panel, whose resolution is 640×480. Experimental results show that this method is able to reduce the non-uniformity of images from 11.06% to 0.98%..

Preliminary observations on escape swimming and giant neurons in Aglantha digitale (Hydromedusae: Trachylina)

1980 ◽  
Vol 58 (4) ◽  
pp. 549-552 ◽  
Author(s):  
S. Donaldson ◽  
G. O. Mackie ◽  
A. Roberts
Keyword(s):  
Action Potentials ◽  
Giant Axon ◽  
Synaptic Delay ◽  
Giant Axons ◽  
A Value ◽  
Giant Synapses ◽  
Run Up

Aglantha can swim in two ways, one of which, fast swimming, is evoked by contact with predators and serves for escape. The response consists of two or three violent contractions of which the first propels the animal a distance equivalent to five body lengths. Peak velocities in the range 0.3–0.4 m s−1 were measured. Drag is reduced by contraction of the tentacles.Coordination of escape swimming and tentacle contraction is achieved by a system of giant axons. A giant axon runs down each tentacle; action potentials in these elements show a one-for-one correspondence with potentials recorded from a ring-shaped axon lying in the margin near the tentacle bases. The ring giant synapses with eight motor giants which run up the subumbrella innervating the swimming muscles.Conduction velocities in the giant axons may be as high as 4.0 m s−1 in the case of the largest (40 μm diameter) axons. A value of 1.6 ms was obtained for minimum synaptic delay between the ring and motor giant axons.

Quanta of the Third Kind

2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Frank Wilczek
Keyword(s):  
Quantum Mechanics ◽  
Experimental Results ◽  
Quantum Mechanical ◽  
The Third

Quantum mechanics is nearly one hundred years old; and yet the challenge it presents to the imagination is so great that scientists are still coming to terms with some of its most basic implications. Theoretical insights and recent experimental results in anyon physics are leading physicists to revise and expand their ideas about what quantum-mechanical particles are and how they behave.

Organization of the Giant Axons of the Cockroach Periplaneta Americana

1969 ◽  
Vol 50 (3) ◽  
pp. 615-627
Author(s):  
M. E. SPIRA ◽  
I. PARNAS ◽  
F. BERGMANN
Keyword(s):  
Nerve Cord ◽  
Periplaneta Americana ◽  
Thoracic Ganglion ◽  
American Cockroach ◽  
Abdominal Ganglion ◽  
Common Pathway ◽  
Average Delay ◽  
Giant Axons ◽  
Stimulation Of

1. Stimulation of the connectives between the suboesophageal and prothoracic ganglia of the American cockroach induced ipsilateral descending spikes in the abdominal giant axons with an average delay of 0·6 msec, per thoracic ganglion. 2. Nicotine at 5 µg./ml. had no effect on conduction in the abdomen but blocked ascending responses sequentially at the 6th abdominal ganglion then at the levels of T1; T2, and T3. 3. Simultaneous descending and ascending impulses resulted in mutual extinction along the nerve cord with the point of collision depending on the interval between stimuli. 4. It is suggested that a common pathway subserves ascending and descending giant impulses and models for bi-directional conduction are discussed.

Neuromuscular transmission in the jellyfish Aglantha digitale

1985 ◽  
Vol 116 (1) ◽  
pp. 1-25 ◽  
Author(s):  
P. A. Kerfoot ◽  
G. O. Mackie ◽  
R. W. Meech ◽  
A. Roberts ◽  
C. L. Singla
Keyword(s):  
Dimensional Space ◽  
Thin Sheet ◽  
Current Source ◽  
Giant Axon ◽  
The Body ◽  
Two Dimensional ◽  
Bathing Medium ◽  
Giant Axons ◽  
Motor Neurones ◽  
Stimulation Of

In the jellyfish Aglantha digitale escape swimming is mediated by the nearly synchronous activity of eight giant motor axons which make direct synaptic contact with contractile myoepithelial cells on the under-surface of the body wall. The delay in transmission at these synapses was 0.7 +/− 0.1 ms (+/− S.D.;N = 6) at 12 degrees C as measured from intracellular records. Transmission depended on the presence of Ca2+ in the bathing medium. It was not blocked by increasing the level of Mg2+ to 127 mmol l-1. The myoepithelium is a thin sheet of electrically coupled cells and injection of current at one point was found to depolarize the surrounding cells. The potential change declined with distance from the current source as expected for two-dimensional current spread. The two-dimensional space constant (lambda) was 770 micron for current flow in the circular direction and 177 micron for radial flow. The internal resistance of the epithelium (178–201 omega cm) and the membrane time constant (5–10 ms) were direction independent. No propagated epithelial action potentials were observed. Spontaneous miniature synaptic potentials of similar amplitude and rise-time were recorded intracellularly at distances of up to 1 mm from the motor giant axon. Ultrastructural evidence confirms that neuro-myoepithelial synapses also occur away from the giant axons. It is likely that synaptic sites are widespread in the myoepithelium, probably associated with the lateral motor neurones as well as the giant axons. Local stimulation of lateral motor neurones generally produced contraction in distinct fields. We suppose that stimulation of a single motor giant axon excites a whole population of lateral motor neurones and hence a broad area of the myoepithelium.

An Analytical Model for the Effective Dielectric Constant of a 0-3-0 Composite

2010 ◽  
Author(s):  
K. A. Cook-Chennault ◽  
S. Banerjee
Keyword(s):  
Dielectric Constant ◽  
Aspect Ratio ◽  
Analytical Model ◽  
Experimental Results ◽  
Effective Dielectric Constant ◽  
The Third ◽  
Third Phase ◽  
Three Phase ◽  
Phase 0 ◽  
Experimental Values

An analytical expression for prediction of the effective dielectric constant of a three phase 0-3-0 ferroelectric composite is presented. The analytical results are verified with the experimental results from Nan et al [1]. We extend the analytical model, so that the influence of the shape of the third phase inclusion, on the effective dielectric constant of the composite, can be investigated. The results indicate that the dielectric constant increases ∼7 times, when the aspect ratio of the conductive inclusion is increased from 1 (sphere) to 10 (spheroid). The analytical predictions compare favorably with the experimental values.

Ultrastructure of region of a low safety factor in inhomogeneous giant axon of the cockroach

1976 ◽  
Vol 39 (4) ◽  
pp. 900-908 ◽  
Author(s):  
M. Castel ◽  
M. E. Spira ◽  
I. Parnas ◽  
Y. Yarom
Keyword(s):  
Electron Microscopy ◽  
Glial Cells ◽  
Extracellular Space ◽  
Light And Electron Microscopy ◽  
Giant Axon ◽  
Serial Sections ◽  
Giant Axons ◽  
Chemical Synapses ◽  
Cytoplasmic Processes ◽  
Periaxonal Space

1. The structure of the ventral giant axons of the cockroach at the level of ganglion T3 was studied by means of light and electron microscopy. 2. From serial sections and cobalt injections, the axons diameter was found to range between 40 and 60 mum at the caudal end of ganglion T3; toward the center of T3 they narrow to 20-40 mum, and again expand to 30-45 mum anteriorly in ganglion T3. 3. Each giant axon sends off several branches, 1-15 mum in diameter, into the neuropil. The giant axons and the bases of their branches are enveloped by cytoplasmic processes of glial cells. The periaxonal space is about 100-200 A. 4. Distally the branches are devoid of glial envelopes and the extracellular space between the branches and other axonal profiles is about 200 A. Terminals with presumptive chemical synapses on the giant axon branches were found. Clear vesicles, 300-400 A in diameter, are seen clustered together. The width of the supposedly synaptic gap is about 100 A. 5. In some areas the branches and other axonal profiles form close appositions.

scholarly journals Molecular identification of SqKv1A. A candidate for the delayed rectifier K channel in squid giant axon.

1996 ◽  
Vol 108 (3) ◽  
pp. 207-219 ◽  
Author(s):  
J J Rosenthal ◽  
R G Vickery ◽  
W F Gilly
Keyword(s):  
Time Course ◽  
Xenopus Oocytes ◽  
Giant Axon ◽  
K Channel ◽  
Delayed Rectifier ◽  
Giant Fiber ◽  
Western Blots ◽  
Internal Solution ◽  
Giant Axons ◽  
K Currents

We have cloned the cDNA for a squid Kvl potassium channel (SqKv1A). SqKv1A mRNA is selectively expressed in giant fiber lobe (GFL) neurons, the somata of the giant axons. Western blots detect two forms of SqKv1A in both GFL neuron and giant axon samples. Functional properties of SqKv1A currents expressed in Xenopus oocytes are very similar to macroscopic currents in GFL neurons and giant axons. Macroscopic K currents in GFL neuron cell bodies, giant axons, and in Xenopus oocytes expressing SqKv1A, activate rapidly and inactivate incompletely over a time course of several hundred ms. Oocytes injected with SqKv1A cRNA express channels of two conductance classes, estimated to be 13 and 20 pS in an internal solution containing 470 mM K. SqKv1A is thus a good candidate for the "20 pS" K channel that accounts for the majority of rapidly activating K conductance in both GFL neuron cell bodies and the giant axon.

GENETIC ALGORITHMS FOR POLYGONAL APPROXIMATION OF DIGITAL CURVES

1999 ◽  
Vol 13 (07) ◽  
pp. 1061-1082 ◽  
Author(s):  
PENG-YENG YIN
Keyword(s):  
Genetic Algorithm ◽  
Genetic Algorithms ◽  
Learning Strategy ◽  
Approximation Error ◽  
Experimental Results ◽  
Polygonal Approximation ◽  
The Third ◽  
Digital Curve

In this paper, three polygonal approximation approaches using genetic algorithms are proposed. The first approach approximates the digital curve by minimizing the number of sides of the polygon and the approximation error should be less than a prespecified tolerance value. The second approach minimizes the approximation error by searching for a polygon with a given number of sides. The third approach, which is more practical, determines the approximating polygon automatically without any given condition. Moreover, a learning strategy for each of the proposed genetic algorithm is presented to improve the results. The experimental results show that the proposed approaches have better performances than those of existing methods.

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