Propagation of electrical signals along giant nerve fibres

1952 ◽  
Vol 140 (899) ◽  
pp. 177-183 ◽  
Keyword(s):  
Sea Water ◽  
Giant Axon ◽  
High Concentration ◽  
Nerve Fibres ◽  
Giant Fibre ◽  
Electrical Signals ◽  
Small Fibre ◽  
The Central Nervous System ◽  
Good Conductor ◽  
Ionic Movement

In this part of the discussion we shall attempt to describe the way in which electrical signals are propagated along the giant nerve fibres of squids and cuttlefish. These fibres consist of cylinders of protoplasm, 0.2 to 0.6 mm in diameter, and ire bounded by a thin membrane which acts as a barrier to ionic movement. The protoplasm, or axoplasm as it is commonly called, is an aqueous gel which is a reasonably good conductor of electricity. It contains a high concentration of K + and a low concentration of Na + and Cl - , this situation being the reverse of that in the animal’s blood or sea water. Axons which are left in sea water slowly lose potassium and gain sodium. This process takes about 24 hours and is roughly 80 000 times slower than the diffusion of ions out of a cylinder of gelatin of the same size. The interchange of sodium and potassium is very greatly accelerated by stimulating the fibres. Experiments with tracers, such as those made by Keynes & Lewis (1951) or Rothenberg (1950), allow the interchange to be measured quantitatively, and there is general agreement that the impulse is associated with an entry of 3 to 4 µ µ mol of Na + through 1 cm 2 of membrane and an exit of a corresponding quantity of K + . These quantities are very small compared with the total number of ions inside the fibre. In the giant axon of the squid the quantity of potassium lost in each impulse corresponds to only about 1 millionth if the total internal potassium. One would therefore expect that a giant fibre should be able to carry a great many impulses without recharging its batteries by metabolism. On the other hand, a very small fibre such as a dendrite in the central nervous system should be much more dependent on metabolism since the ratio of surface to volume may be nearly 1000 times greater.

scholarly journals Fused neurons and synaptic contacts in the giant nerve fibres of cephalopods

1939 ◽  
Vol 229 (564) ◽  
pp. 465-503 ◽  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Giant Cells ◽  
Nerve Cells ◽  
The Body ◽  
Complete Fusion ◽  
Nerve Fibres ◽  
Giant Fibre ◽  
The Central Nervous System ◽  
Giant Fibre System

The fact that there are two very large nerve cells in the central nervous system of the squid, Loligo , was discovered by Williams (1909), who also gave a brief description of their connexions. His account appears never to have been amplified, or indeed even mentioned, by any subsequent worker until these enormous nerve fibres were accidentally rediscovered in 1933 (see Young 1935 a , 1936 a, b, c ). Williams considered that the whole giant-fibre system on each side of the body consists of the processes of one of the two main giant cells. In fact the arrangement is much more complicated than this, and contains two curiously opposite features of the greatest interest for the neurologist (Young 1936 £). First, the processes of the two main giant cells provide a clear case of the complete fusion of the axons of two nerve cells, thus infringing the strict canon of the neuron theory. Nevertheless, and this is the second point, there are also present, elsewhere in the system, discontinuous synapses which are perhaps more clear and easy to study than any yet described.

MEASURES FOR ENVIRONMENT CONSERVATION IN ENCLOSED COASTAL SEAS

2017 ◽  
Author(s):  
Keizo Negi ◽  
Keizo Negi ◽  
Takuya Ishikawa ◽  
Takuya Ishikawa ◽  
Kenichiro Iba ◽  
...  
Keyword(s):  
Water Pollution ◽  
Water Quality ◽  
Water Mass ◽  
Sea Water ◽  
Red Tide ◽  
Water Environment ◽  
Quality Standard ◽  
Tokyo Bay ◽  
View Point ◽  
High Concentration

Japan experienced serious water pollution during the period of high economic growth in 1960s. It was also the period that we had such damages to human health, fishery and living conditions due to red tide as much of chemicals, organic materials and the like flowing into the seas along the growing population and industries in the coastal areas. Notable in those days was the issues of environment conservation in the enclosed coastal seas where pollutants were prone to accumulate inside due to low level of water circulation, resulting in the issues including red tide and oxygen-deficient water mass. In responding to these issues, we implemented countermeasures like effluent control with the Water Pollution Control Law and improvement/expansion of sewage facilities. In the extensive enclosed coastal seas of Tokyo Bay, Ise Bay and the Seto Inland Sea, the three areas of high concentration of population, we implemented water quality total reduction in seven terms from 1979, reducing the total quantities of pollutant load of COD, TN and TP. Sea water quality hence has been on an improvement trend as a whole along the steady reduction of pollutants from the land. We however recognize that there are differences in improvement by sea area such as red tide and oxygen-deficient water mass continue to occur in some areas. Meanwhile, it has been pointed out that bio-diversity and bio-productivity should be secured through conservation/creation of tidal flats and seaweed beds in the view point of “Bountiful Sea” To work at these challenges, through the studies depending on the circumstances of the water environment in the enclosed coastal seas, we composed “The Policy of Desirable State of 8th TPLCS” in 2015. We have also added the sediment DO into the water quality standard related to the life-environmental items in view of the preservation of aquatic creatures in the enclosed water areas. Important from now on, along the Policy, is to proceed with necessary measures to improve water quality with good considerations of differences by area in the view point of “Beautiful and bountiful Sea”.

scholarly journals Self-buffering capacity of a human sulfatase for central nervous system delivery

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yi Wen ◽  
Nazila Salamat-Miller ◽  
Keethkumar Jain ◽  
Katherine Taylor
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Buffering Capacity ◽  
The Self ◽  
High Concentration ◽  
Formulation Design ◽  
The Central Nervous System ◽  
Therapeutic Enzymes ◽  
Intrathecal Space

AbstractDirect delivery of therapeutic enzymes to the Central Nervous System requires stringent formulation design. Not only should the formulation design consider the delicate balance of existing ions, proteins, and osmolality in the cerebrospinal fluid, it must also provide long term efficacy and stability for the enzyme. One fundamental approach to this predicament is designing formulations with no buffering species. In this study, we report a high concentration, saline-based formulation for a human sulfatase for its delivery into the intrathecal space. A high concentration formulation (≤ 40 mg/mL) was developed through a series of systematic studies that demonstrated the feasibility of a self-buffered formulation for this molecule. The self-buffering capacity phenomenon was found to be a product of both the protein itself and potentially the residual phosphates associated with the protein. To date, the self-buffered formulation for this molecule has been stable for up to 4 years when stored at 5 ± 3 °C, with no changes either in the pH values or other quality attributes of the molecule. The high concentration self-buffered protein formulation was also observed to be stable when exposed to multiple freeze–thaw cycles and was robust during in-use and agitation studies.

scholarly journals Structural complexes in the squid giant axon membrane sensitive to ionic concentrations and cardiac glycosides

1976 ◽  
Vol 69 (1) ◽  
pp. 19-28 ◽  
Author(s):  
GM Villegas ◽  
J Villegas
Keyword(s):  
Cardiac Glycosides ◽  
Sea Water ◽  
Giant Axon ◽  
Structural Features ◽  
Nerve Fibers ◽  
Axon Membrane ◽  
Ionic Concentrations ◽  
Low Concentrations ◽  
High Calcium ◽  
Active Ion Transport

Giant nerve fibers of squid Sepioteuthis sepiodea were incubated for 10 min in artificial sea water (ASW) under control conditions, in the absence of various ions, and in the presence of cardiac glycosides. The nerve fibers were fixed in OsO(4) and embedded in Epon, and structural complexes along the axolemma were studied. These complexes consist of a portion of axolemma exhibiting a three-layered substructure, an undercoating of a dense material (approximately 0.1μm in length and approximately 70-170 A in thickness), and a narrowing to disappearance of the axon-Schwann cell interspace. In the controls, the incidence of complexes per 1,000μm of axon perimeter was about 137. This number decreased to 10-25 percent when magnesium was not present in the incubating media, whatever the calcium concentration (88, 44, or 0 mM). In the presence of magnesium, the number and structural features of the complexes were preserved, though the number decreased to 65 percent when high calcium was simultaneously present. The complexes were also modified and decreased to 26-32 percent by incubating the nerves in solutions having low concentrations of sodium and potassium. The adding of 10(-5) M ouabain or strophanthoside to normal ASW incubating solution decreased them to 20-40 percent. Due to their sensitivity to changes in external ionic concentrations and to the presence of cardiac glycosides, the complexes are proposed to represent the structural correlate of specialized sites for active ion transport, although other factors may be involved.

Motility and energy-rich phosphorus compounds in spermatozoa of Octopus dofleini martini

1971 ◽  
Vol 178 (1051) ◽  
pp. 151-160 ◽  
Keyword(s):  
Sea Water ◽  
Phosphorus Compounds ◽  
Short Exposure ◽  
Motile Sperm ◽  
High Concentration ◽  
Irreversible Loss ◽  
Prolonged Incubation ◽  
The North ◽  
Sperm Suspension ◽  
The North Pacific

The spermatozoa of the giant octopus of the North Pacific, freshly removed from spermatophores, showed very little motility, but on dilution with sea-water or 2.7 % NaCl, followed by dialysis against either of these two media, they became intensely motile and remained so for several days at 2 to 10 °C. At higher temperatures, particularly above 25 °C, octopus spermatozoa lost their motility rapidly. At 35 °C, complete and irreversible loss of motility occurred within less than 1 min. The motility of octopus spermatozoa at 2 to 10 °C persisted under both anaerobic and aerobic conditions and did not require the presence of exogenous glycolysable sugar. The addition of spermatophoric plasma to a motile sperm suspension inhibited motility. Other inhibitors were sodium azide, 2, 4-dinitrophenol and ethylenediaminetetra-acetate, at 0.001 M concentrations. ATP, ADP and arginine phosphate have been identified and quantitatively measured in octopus spermatozoa. On prolonged incubation of motile sperm suspensions a t 3 °C, ATP and ADP did not decline appreciably, whilst arginine phosphate decreased considerably. The decrease was even more pronounced in sperm suspensions which had first been inactivated by short exposure to 35 °C, prior to prolonged incubation at 3 °C. Glycogen, the main carbohydrate store of octopus spermatozoa, remained at a high concentration even in sperm suspensions kept for 5 days at 3 °C, and there was no appreciable difference in that respect between a sample containing motile spermatozoa and one in which, at the outset of incubation, the spermatozoa were immobilized by heating to 35 °C.

The Environmental Relations of Vegetation Pattern on Chenier Beach Ridges on Bathurst Island, Northern Territory

1993 ◽  
Vol 41 (3) ◽  
pp. 275 ◽  
Author(s):  
RJ Fensham
Keyword(s):  
Sea Water ◽  
Acid Soils ◽  
Soil Nutrient ◽  
Vegetation Pattern ◽  
High Concentration ◽  
Radiocarbon Dates ◽  
Beach Ridges ◽  
Nutrient Levels ◽  
Environmental Relations ◽  
Monsoon Rainforest

Radiocarbon dates confirm a chronological sequence for late Holocene beach ridges at Wangiti Beach on Bathurst Island. The vegetation on these beach ridges can be clearly related to topography and distance from the sea. Monsoon rainforest occurs on the fore-dunes where the nutrient levels of the young sediments are relatively high. The mid-dunes support woodland dominated by Melalueca viridiflora and have nutrient-poor acid soils. Vegetation with a high component of monsoon rainforest species occupies the rear dunes, which have a high concentration of seawater macronutrient cations despite their older age than more seaward dunes. The relatively low elevation of the rear dunes supports the suggestion that soil nutrient levels are enriched by sea water or marine sediments during infrequent inundation events such as those during cyclones.

scholarly journals LONGITUDINAL IMPEDANCE OF THE SQUID GIANT AXON

1941 ◽  
Vol 24 (6) ◽  
pp. 771-788 ◽  
Author(s):  
Kenneth S. Cole ◽  
Richard F. Baker
Keyword(s):  
Sea Water ◽  
Low Frequency ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Dielectric Characteristics ◽  
Impedance Characteristics ◽  
Longitudinal Impedance ◽  
Electrode Length ◽  
Interpolar Distance ◽  
Inductive Reactance

Longitudinal alternating current impedance measurements have been made on the squid giant axon over the frequency range from 30 cycles per second to 200 kc. per second. Large sea water electrodes were used and the inter-electrode length was immersed in oil. The impedance at high frequency was approximately as predicted theoretically on the basis of the poorly conducting dielectric characteristics of the membrane previously determined. For the large majority of the axons, the impedance reached a maximum at a low frequency and the reactance then vanished at a frequency between 150 and 300 cycles per second. Below this frequency, the reactance was inductive, reaching a maximum and then approaching zero as the frequency was decreased. The inductive reactance is a property of the axon and requires that it contain an inductive structure. The variation of the impedance with interpolar distance indicates that the inductance is in the membrane. The impedance characteristics of the membrane as calculated from the measured longitudinal impedance of the axon may be expressed by an equivalent membrane circuit containing inductance, capacity, and resistance. For a square centimeter of membrane the capacity of 1 µf with dielectric loss is shunted by the series combination of a resistance of 400 ohms and an inductance of one-fifth henry.

The role of support cells in the growth and differentiation of neurones in the abdominal ganglion of Aplysia

1981 ◽  
Vol 95 (1) ◽  
pp. 205-214
Author(s):  
S. M. Schacher
Keyword(s):  
Cell Body ◽  
Synapse Formation ◽  
Sea Water ◽  
Secretory Granules ◽  
Body Growth ◽  
Abdominal Ganglion ◽  
Morphological Properties ◽  
High Concentration ◽  
Premature Release

During the late premetamorphic stages of development, the abdominal ganglion of Aplysia is surrounded by a group of support cells which later develop morphological properties characteristic of glial cells. These support cells contain large secretory granules whose contents are released primarily after the onset of the metamorphic phase. The release of the granule contents may signal the burst of neuronal growth and maturation that occurs following metamorphosis. The evidence supporting this idea is the following: (1) The release of the granule material after the onset of metamorphosis coincides with an increase in cell body growth and a more marked increase in the density of synapses within the neuropil. Both release and neuronal maturation can be blocked when metamorphosis is postponed by withholding the appropriate macroalgal substrate. (2) Premature release of the granule contents 2-3 weeks before metamorphosis with artificial sea water containing a high concentration of potassium results in an increase in cell body growth, density of synapses, and the number of spines formed and contacts received by specific identified cells. (3) Artificially inducing the release of the granule material in animals whose metamorphosis has been prevented (by withholding the appropriate substrate) still produces an increase in cell body growth and density of synapses. These results suggest that the release of material from support cell granules provides a general stimulus for neuronal differentiation including cell body growth, spine development, and synapse formation.

The Giant Nerve-Fibres in the Central Nervous System of Myxicola (Polychaeta, Sabellidae)

1948 ◽  
Vol s3-89 (5) ◽  
pp. 1-45
Author(s):  
J.A. C. NICOL
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Nerve Cord ◽  
Size Structure ◽  
Nerve Cells ◽  
The Body ◽  
Usual Sense ◽  
Fibrous Sheath ◽  
Giant Fibre ◽  
The Central Nervous System

1. A description is given of the main features of the central nervous system of Myxicola infundibulum Rénier. 2. The nerve-cord is double in the first four thoracic segments and single posteriorly. It shows segmental swellings but is not ganglionated in the usual sense in that nerve-cell accumulations are not related directly to such swellings of the cord. 3. A very large axon lies within the dorsal portion of the nerve-cord and extends from the supra-oesophageal ganglia to the posterior end of the animal. It is small in the head ganglia where it passes transversely across the mid-line, increases in diameter in the oesophageal connectives, and expands to very large size, up to 1 mm., in the posterior thorax and anterior abdomen, and gradually tapers off to about 100µ in the posterior body. It shows segmental swellings corresponding to those of the nerve-cord in each segment. It occupies about 27 per cent, of the volume of the central nervous system and 0.3 per cent, of the volume of the animal. The diameter of the fibre increases during contraction of the worm. 4. The giant fibre is a continuous structure throughout its length, without internal dividing membranes or septa. Usually a branch of the giant fibre lies in each half of the nerve-cord in the anterior thoracic segments and these several branches are continuous with one another longitudinally and transversely. 5. The giant fibre is connected with nerve-cells along its entire course; it arises from a pair of cells in the supra-oesophageal ganglia, and receives the processes of many nerve-cells in each segment. There is no difference between the nerve-cells of the giant fibre and the other nerve-cells of the cord. 6. A distinct fibrous sheath invests the giant fibre. A slight concentration of lipoid can be revealed in this sheath by the use of Sudan black. 7. About eight peripheral branches arise from the giant fibre in each segment. They have a complex course in the nerve-cord where they anastomose with one another and receive the processes of nerve-cells. Peripherally, they are distributed to the longitudinal musculature. 8. Specimens surviving 16 days following section of the nerve-cord in the thorax have shown that the giant fibre does not degenerate in front of or behind a cut, thus confirming that it is a multicellular structure connected to nerve-cells in the thorax and abdomen. 9. It is concluded that the giant fibre of M. infundibulum is a large syncytial structure, extending throughout the entire central nervous system and the body-wall of the animal. 10. The giant fibre system of M. aesthetica resembles that of M. infundibulum. 11. Some implications of the possession of such a giant axon are discussed. It is suggested that its size, structure, and simplicity lead to rapid conduction and thus effect a considerable saving of reaction time, of considerable value to the species when considered in the light of the quick contraction which it mediates. The adoption of a sedentary mode of existence has permitted this portion of the central nervous system to become developed at the expense of other elements concerned with errant habits.

scholarly journals Effect of Temperature on the Potential and Current Thresholds of Axon Membrane

1962 ◽  
Vol 46 (2) ◽  
pp. 257-266 ◽  
Author(s):  
Rita Guttman ◽  
Keyword(s):  
Sea Water ◽  
Sucrose Solution ◽  
Giant Axon ◽  
Threshold Current ◽  
Squid Giant Axon ◽  
Effect Of Temperature ◽  
Threshold Potential ◽  
Axon Membrane ◽  
Central Segment ◽  
The Mean

The effect of temperature on the potential and current thresholds of the squid giant axon membrane was measured with gross external electrodes. A central segment of the axon, 0.8 mm long and in sea water, was isolated by flowing low conductance, isoosmotic sucrose solution on each side; both ends were depolarized in isoosmotic KCl. Measured biphasic square wave currents at five cycles per second were applied between one end of the nerve and the membrane of the central segment. The membrane potential was recorded between the central sea water and the other depolarized end. The recorded potentials are developed only across the membrane impedance. Threshold current values ranged from 3.2 µa at 267deg;C to 1 µa at 7.5°C. Threshold potential values ranged from 50 mv at 26°C to 6 mv at 7.5°C. The mean Q10 of threshold current was 2.3 (SD = 0.2), while the Q10 for threshold potentials was 2.0 (SD = 0.1).

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