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.

The Different Connections and Motor Outputs of Lateral and Medial Giant Fibres in the Crayfish

1971 ◽  
Vol 54 (2) ◽  
pp. 391-404
Author(s):  
JAMES L. LARIMER ◽  
ALAN C. EGGLESTON ◽  
LEONA M. MASUKAWA ◽  
DONALD KENNEDY
Keyword(s):  
High Speed ◽  
Motor Neurone ◽  
Giant Axons ◽  
Procion Yellow ◽  
High Speed Cinematography ◽  
Motor Neurones ◽  
Motor Outputs ◽  
Giant Fibres ◽  
Tonic System ◽  
Stimulation Of

1. High-speed cinematography was used to analyse the abdominal movements of crayfish in response to separate stimulation of medial and lateral giant axons. These films showed that the medial giant fibres command complete abdominal flexions with little flaring of the tail appendages. The lateral giants, in contrast, evoked a relatively weak flexion of the middle abdominal segments, accompanied by promotion of the exopodites of the uropods. 2. An examination of the muscles activated by the two types of giant fibres shows that differences in the connexions between the giant fibres and specific motor neurones can account for the behavioural differences observed. 3. The output of the giant fibres was determined in the sixth abdominal ganglion, where their differential effects are most pronounced. The medial giants activate motor neurones whose axons emerge from root 6 of the sixth ganglion. The lateral giants activate motor neurones whose axons emerge via roots 2 and 3, as well as those emerging via root 6. 4. The larger motor neurones associated with the giant axons in the sixth root of the sixth ganglion have been mapped by Procion Yellow injection, and the terminations of the central giant axons in the sixth ganglion have also been determined. The connexions revealed by this technique are consistent with the physiological findings. 5. The evidence suggests that root 6 of the sixth ganglion is homologous with root 3 of the more anterior ganglia. However, the giant motor neurone of the sixth ganglion has not been identified. 6. The medial and lateral giant fibres, and perhaps other specific ‘command’ interneurones, can thus drive specific ensembles of phasic motor neurones to provide a range of stereotyped quick movements. In this respect the organization of the phasic system of interneurones and motor neurones resembles that in the tonic system.

Giant Axons and Synergic Contractions in Branchiomma Vesiculosum

1951 ◽  
Vol 28 (1) ◽  
pp. 22-31 ◽  
Author(s):  
J. A. COLIN NICOL
Keyword(s):  
Time Course ◽  
Body Wall ◽  
Giant Axon ◽  
The Body ◽  
Single Muscle ◽  
Graphic Method ◽  
Giant Axons ◽  
Maximal Tension ◽  
Contraction And Relaxation ◽  
Electrical Stimuli

Synergic contractions following giant axon stimulation in Branchiomma vesiculosum have been investigated by the graphic method of recording. Isotonic and isometric levers were used, and electrical stimuli from condenser discharges were applied to the surface of the animal. Single muscle twitches occur at stimulation frequencies up to 2 per sec., above which clonus, and finally tetanus result. At high rates of stimulation fatigue rapidly sets in; this fatigue is reversible. Data for the time course of contractions are presented. Maximal tension develops about 255 msec. after the beginning of contraction, and relaxation occupies about 1.8 sec. Maximal tension developed isometrically under stimulation at different frequencies (12 per min. to 13 per sec.) was measured. Maximal tension is developed initially, and there is no evidence for facilitation. Extension of the animal and of strips of the body wall under tension are described. The results are discussed in terms of the habits of the animal, and compared with similar studies of other invertebrates.

Osmotic stimulation of Na(+)-K(+)-Cl- cotransport in squid giant axon is [Cl-]i dependent

1990 ◽  
Vol 258 (4) ◽  
pp. C749-C753 ◽  
Author(s):  
G. E. Breitwieser ◽  
A. A. Altamirano ◽  
J. M. Russell
Keyword(s):  
Giant Axon ◽  
Dose Dependence ◽  
Squid Giant Axon ◽  
Dependent Manner ◽  
Transport Activity ◽  
Concentration Dependent Manner ◽  
Giant Axons ◽  
Stepwise Increase ◽  
Osmotic Stimulation ◽  
Stimulation Of

The effects of increasing extracellular osmolality on unidirectional Cl- fluxes through the Na(+)-K(+)-Cl- cotransporter were studied in internally dialyzed squid giant axons. Hyperosmotic seawater stimulated bumetanide-sensitive Cl-influx at 150 mM intracellular Cl- concentration ([Cl-]i), whereas Cl- efflux was unaffected under comparable ionic conditions. Stimulation of bumetanide-sensitive Cl- influx was proportional to the increase in extracellular osmolality. Bumetanide-sensitive Cl- influx began to increase after a latency of approximately 20 min after a stepwise increase of extracellular osmolality and continued to increase for at least 70 min. The increased bumetanide-sensitive Cl- influx measured after 65 min of exposure to hyperosmotic external fluid was a function of the intracellular Cl- concentration; stimulation by hyperosmotic external fluids was observed at physiological [Cl-]i levels (greater than 100 mM) but not at lower [Cl-]i levels. Under both normo- and hyperosmotic conditions, intracellular Cl- inhibited Na(+)-K(+)-Cl- cotransport influx in a concentration-dependent manner. However, in hyperosmotic seawater, the dose dependence of inhibition by intracellular Cl- was shifted to higher [Cl-]i values. Therefore, we conclude that hyperosmotic extracellular fluids stimulate influx via the Na(+)-K(+)-Cl- cotransport by resetting the relation between [Cl-]i and transport activity.

Central circuitry in the jellyfish Aglantha digitale. III. The rootlet and pacemaker systems

2000 ◽  
Vol 203 (12) ◽  
pp. 1797-1807 ◽  
Author(s):  
G.O. Mackie ◽  
R.W. Meech
Keyword(s):  
Neuromuscular Junctions ◽  
Close Contact ◽  
Distinct Type ◽  
Giant Axon ◽  
Nerve Ring ◽  
Excitatory Postsynaptic Potential ◽  
Interconnected System ◽  
Giant Axons ◽  
Secondary Consequence ◽  
Stimulation Of

Tactile stimulation of the subumbrella of Aglantha digitale was found to evoke an escape swimming response similar to that evoked by stimulation of the outer surfaces of the margin but that does not involve the ring giant axon. Evidence is presented that conduction around the margin takes place via an interconnected system of rootlet interneurones. Confocal microscopy of carboxyfluorescein-filled axons showed that the rootlet neurones run out from the bases of the motor giant axons within the inner nerve ring and come into close contact with those of the neighbouring motor giant axons on either side. Transmission between the rootlet neurones has the properties of chemical synaptic transmission. A distinct type of fast excitatory postsynaptic potential (rootlet PSP) was recorded in motor giant axons following stimulation of nearby axons in 3–5 mmol l(−)(1) Mn(2+), which lowered the PSP below spike threshold. Immune labelling with anti-syntaxin 1 showed structures tentatively identified as synapses in the inner nerve ring, including some on the rootlet neurones. Neuromuscular junctions were not labelled. A secondary consequence of stimulating motor giant axons was the triggering of events in the pacemaker system. Triggering was blocked in 105 mmol l(−)(1) Mg(2+), indicating a synaptic link. Activity in the pacemaker system led indirectly to tentacle contractions (as described in earlier papers in this series), but the contractions were not as sudden or as violent as those seen when escape swimming was mediated by the ring giant axon. Events triggered in the pacemaker system fed back into the motor giants, producing postsynaptic potentials that appeared as humps in the spike after-potential. The conduction velocity of events propagating in the relay system was increased when the rootlet pathway was simultaneously excited (piggyback effect). With the addition of the rootlet pathway, the number of identified systems concerned with locomotion, feeding and tentacle contractions comes to fourteen, and the list is probably nearly complete.

Modulation of spike frequency by regions of special axonal geometry and by synaptic inputs

1976 ◽  
Vol 39 (4) ◽  
pp. 882-899 ◽  
Author(s):  
M. E. Spira ◽  
Y. Yarom ◽  
I. Parnas
Keyword(s):  
Conduction Block ◽  
Membrane Conductance ◽  
Giant Axon ◽  
Membrane Resistance ◽  
High Frequency Stimulation ◽  
Extracellular Potassium ◽  
Synaptic Inputs ◽  
Giant Axons ◽  
Synaptic Potentials ◽  
Stimulation Of

1. Spike propagation across the nonhomogeneous section of the giant axon in ganglion T3 of the cockroach was analyzed by intracellular microelectrodes recording at the posterior and anterior ends of T3. Ascending and descending potentials were evoked by stimulation of A5-A6 and T2-T3 connectives. 2. At high frequencies, descending and ascending impulses exhibit the following: a) consecutive reduction in the spike amplitude, b) a decrease in the afterhyperpolarization; c) gradual appearance of a prepotential together with an increase in delay of spike initiation; d) failure of full spike invasion into the recording area, showing only a decremental potential. 3. The duration of a train required to block spike propagation when the whole connective is stimulated is much shorter (about 6 times) than that required when a single giant axon is stimulated. 4. The conduction block is associated with a marked decrease in effective membrane resistance, greater than that expected from depolarization and delayed rectification. 5. Synaptic potentials could be recorded in the giant axons in the caudal base of ganglion T3 after stimulation of either the ipsilateral or contralateral connectives at both ends of the ganglion. These synaptic potentials could be blocked by d-tubocurarine (d-TC) or low Ca2+-high Mg2+. 6. Activation of these synapses produces a marked increase in membrane conductance, blocking propagation of spike trains through the ganglion. 7. After these synapses are blocked by d-TC or low Ca2+-high Mg2+, high-frequency stimulation still produces a conduction block. 8. It seems that conduction of spike during repetitive stimulation is affected both by accumulation of extracellular potassium, which depolarizes the membrane and causes sodium inactivation, and by activation of synaptic inputs to shunt the membrane in this region. 8. Each of these two mechanisms by itself can produce conduction block along the giant axons in ganglion T3.

scholarly journals Withdrawal Reflex and Conduction Block in the Giant Axons of a Sabellid Worm (Pseudopotamilla Occelata)

1986 ◽  
Vol 126 (1) ◽  
pp. 433-444
Author(s):  
TAKASHIRO HIGUCHI ◽  
HIROYUKI NAKAMURA ◽  
KATSUHIKO SAWAUCHI ◽  
HIROSHI OKUMURA
Keyword(s):  
Action Potentials ◽  
Conduction Block ◽  
Giant Axon ◽  
The Body ◽  
Axon Membrane ◽  
Histological Studies ◽  
Giant Axons ◽  
Withdrawal Reflex ◽  
Anterior Half ◽  
Longitudinal Muscles

1. Body contraction in the sabellid worm, Pseudopotamilla occelata, during the rapid withdrawal reflex occurred only in the anterior half of the body. End-to-end shortening was never observed. The longitudinal muscles are well-developed in the anterior half, and poorly developed in the posterior half. 2. Conduction of action potentials along the giant axons was blocked at the midbody, and was responsible for the anteriorly restricted body contraction. 3. Electrophysiological and histological studies excluded the possibility that conduction block resulted from a safety factor attributable to the special geometry of the axons. 4. Current injection across the giant axon membrane in the region of the conduction block indicated that changes in the properties of the membrane were responsible for the conduction block.

scholarly journals Determination of load distribution in a given medium according to the values of the loads at certain points

2021 ◽  
pp. 167-175
Author(s):  
Oleksandr Mostovenko ◽  
Serhii Kovalov ◽  
Svitlana Botvinovska
Keyword(s):  
Boundary Conditions ◽  
Load Distribution ◽  
Numerical Solutions ◽  
Dimensional Space ◽  
Geometric Model ◽  
Three Dimensional ◽  
The Body ◽  
Three Dimensions ◽  
Two Dimensional ◽  
One Dimensional

Taking into account force, temperature and other loads, the stress and strain state calculations methods of spatial structures involve determining the distribution of the loads in the three-dimensional body of the structure [1, 2]. In many cases the output data for this distribution can be the values of loadings in separate points of the structure. The problem of load distribution in the body of the structure can be solved by three-dimensional discrete interpolation in four-dimensional space based on the method of finite differences, which has been widely used in solving various engineering problems in different fields. A discrete conception of the load distribution at points in the body or in the environment is also required for solving problems by the finite elements method [3-7]. From a geometrical point of view, the result of three-dimensional interpolation is a multivariate of the four-dimensional space [8], where the three dimensions are the coordinates of a three-dimensional body point, and the fourth is the loading at this point. Such interpolation provides for setting of the three coordinates of the point and determining the load at that point. The simplest three-dimensional grid in the three-dimensional space is the grid based on a single sided hypercube. The coordinates of the nodes of such a grid correspond to the numbering of nodes along the coordinate axes. Discrete interpolation of points by the finite difference method is directly related to the numerical solutions of differential equations with given boundary conditions and also requires the setting of boundary conditions. If we consider a three-dimensional grid included into a parallelepiped, the boundary conditions are divided into three types: 1) zero-dimensional (loads at points), where the three edges of the grid converge; 2) one-dimensional (loads at points of lines), where the four edges of the grid converge; 3) two-dimensional (loads at the points of faces), where the five edges of the grid converge. The zero-dimensional conditions are boundary conditions for one-dimensional interpolation of the one-dimensional conditions, which, in turn, are boundary conditions for two-dimensional conditions, and the two-dimensional conditions are boundary conditions for determining the load on the inner points of the grid. If a load is specified only at certain points of boundary conditions, then the interpolation problem is divided into three stages: one-dimensional load interpolation onto the line nodes, two-dimensional load interpolation onto the surface nodes and three-dimensional load interpolation onto internal grid nodes. The proposed method of discrete three-dimensional interpolation allows, according to the specified values of force, temperature or other loads at individual points of the three-dimensional body, to interpolate such loads on all nodes of a given regular three-dimensional grid with cubic cells. As a result of interpolation, a discrete point framework of the multivariate is obtained, which is a geometric model of the distribution of physical characteristics in a given medium according to the values of these characteristics at individual points.

IX. Lines of induction in a magnetic field

1901 ◽  
Vol 195 (262-273) ◽  
pp. 303-327 ◽  
Keyword(s):  
Magnetic Field ◽  
Circular Cylinder ◽  
Viscous Liquid ◽  
Thin Sheet ◽  
The Body ◽  
Two Dimensional ◽  
Transparent Medium ◽  
Exact Position ◽  
Stream Lines ◽  
Lines Of Force

The following paper, which is partly experimental and partly mathematical, has arisen from the discovery that two-dimensional cases of magnetic lines of force could apparently be represented by the flow of a viscous liquid.* The original experiments upon which this assumption was made, showed that the stream lines which were obtained by the method in question, gave results very similar to those which had been calculated and plotted for the cases of an elliptical and circular cylinder. In order to ascertain definitely that the stream lines under these circum­stances actually gave the exact position and direction of the corresponding magnetic lines of force, a result which, if verified, could be used for many practical investi­gations—it was necessary to undertake a long research dealing with the various points involved, a research which has proved extremely laborious, extending without intermission over a period of nearly two years. In the first place it was necessary to devise some method by which a thin sheet of transparent or semi-transparent medium could be obtained of any required thickness, and on which, when placed between two sheets of glass, the required section of the body to be investigated could be formed.

scholarly journals The Telson Flexor Neuromuscular System of the Crayfish: III. The Role of Feedforward Inhibition in Shaping a Stereotyped Behaviour Pattern

1987 ◽  
Vol 127 (1) ◽  
pp. 295-311
Author(s):  
J. P. C. DUMONT ◽  
J. J. WINE
Keyword(s):  
Sensory Input ◽  
Giant Axon ◽  
Behaviour Pattern ◽  
Flexor Muscles ◽  
Motor Neurones ◽  
Observed Behaviour ◽  
Direct Input ◽  
Stimulation Of ◽  
Feedforward Inhibition

1. The telson flexor system is homologous to the fast flexor system of anterior ganglia (Dumont & Wine, 1986a), but important differences exist in connections to the telson motor giants (MoGs) (Dumont & Wine, 1986b). In this paper, we describe additional differences in connections to the telson non-giant fast flexor (FF) motor neurones and to the telson flexor inhibitor (FI). 2. The telson FF motor neurones in ganglion 6 (G6) receive inputs similar to those in G4 and G5 (Miller, Hagiwara & Wine, 1985). The escape command neurones (lateral giants, LGs, and medial giants, MGs) in common provide weak disynaptic input via the telson segmental giant (SG6), and relatively strong trisynaptic input via SG2, SG3 and the corollary discharge interneurones 12 and 13. There may also be some direct input from the MGs, but it, as well as the connections from SG6, appears to vary in different preparations. 3. The compound PSP produced in telson FFs by a single LG or MG impulse was suprathreshold in only five of 55 experiments in isolated abdominal nerve cords, but the probability that a motor neurone would fire increased with additional giant axon impulses, showing that temporal summation of excitation outweighed the possible recruitment of inhibition. Firing probability was higher in semi-intact preparations, where at least one posterior telson FF was fired by a single LG impulse 50% of the time. As was pointed out previously (Dumont & Wine, 1986b), telson flexion would disrupt the behaviour pattern expected from LG commands. 4. Two pathways of feedforward inhibition were found which prevent such disruption. The sensory input that recruits the LG also recruits powerful feedforward inhibition of the telson FF motor neurones, which reduces the probability that they will be fired by the LG. The same sensory stimulus also evokes inhibition of FFs in G5, excitation of FFs in G2 and G3, and mixed excitation and inhibition of FFs in G4. In addition, the telson FIs fire at short latency during LG-mediated tailflips. This occurs because the telson FIs are excited by sensory input. In fact, the firing threshold of the telson FIs to sensory input is lower than that of the LGs, at least for electrical stimulation of nerves. When the LGs do fire, they produce additional excitation of the FIs. The telson FIs also are excited by the LGs but not by the MGs. In contrast, the anterior homologues of the telson FIs receive equivalent, delayed excitation from both MGs and LGs, and weaker sensory input, so that they tend to fire only after the peak of flexion (Wine & Mistick, 1977). 5. The predicted net effect of these connections is that the telson flexor muscles should not contract during naturally elicited LG tailflips, and this is consistent with observed behaviour. The results can be interpreted as providing additional examples of potentially maladaptive central connections which are not expressed in behaviour because of feedforward inhibition.

Evaluation of clinical efficacy of Derinat® in form of spray in practice of district therapist

2019 ◽  
Vol 1 (9) ◽  
pp. 38-46
Author(s):  
A. P. Babkin ◽  
A. A. Zuikova ◽  
O. N. Krasnorutskaya ◽  
Yu. A. Kotova ◽  
D. Yu. Bugrimov ◽  
...  
Keyword(s):  
Clinical Efficacy ◽  
Respiratory Diseases ◽  
Viral Infections ◽  
Pharmacological Action ◽  
The Body ◽  
Natural Resistance ◽  
Acute Respiratory Diseases ◽  
T Helpers ◽  
T Killers ◽  
Stimulation Of

The widespread worldwide spread of acute respiratory diseases is an urgent problem in health care. Expressed polyetiology of respiratory diseases does not allow to limit the use of specific vaccine preparations and dictates the need to use to combat them a variety of non-specific means that stimulate the natural resistance of the human body. The main pharmacological action of sodium deoxyribonucleate is the stimulation of phagocytic activity of T-helpers and T-killers, increasing the functional activity of neutrophils and monocytes/ macrophages, providing regeneration and repair processes in the epithelial component of antiviral protection of the body. Based on the above, the study of the clinical efficacy of Derinat® in the form of spray in the treatment of acute respiratory viral infections is relevant.

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