scholarly journals KINETICS OF ION MOVEMENT IN THE SQUID GIANT AXON

1955 ◽  
Vol 39 (2) ◽  
pp. 279-300 ◽  
Author(s):  
Abraham M. Shanes ◽  
Morris D. Berman
Keyword(s):  
Sea Water ◽  
Giant Axon ◽  
Cortical Layer ◽  
Central Segment ◽  
Exponential Decline ◽  
Rate Of Emergence ◽  
The Individual ◽  
Two Stages ◽  
Ion Species ◽  
Kinetics Of

The loss of Na22, K42, and Cl36 from single giant axons of the squid, Loligo pealii, following exposure to an artificial sea water containing these radioisotopes, occurs in two stages, an initial rapid one followed by an exponential decline. The time constants of the latter stage for the 3 ion species are, respectively, 290, 200, and 175 minutes. The outflux of sodium is depressed while that of potassium is accelerated in the absence of oxygen; the emergence of potassium is slowed by cocaine, while that of sodium is unaffected. One cm. ends of the axons take up about twice as much radiosodium as the central segment; this difference in activity is largely preserved during exposure to inactive solution. Such marked differences are not observed with radiopotassium. From the experimental data estimates are given of the influxes and outfluxes of the individual ions. The kinetics of outflux suggests a cortical layer of measureable thickness which contains the ions in different proportions from those in the medium and which governs the rate of emergence of these ions from the axon as though it contained very few but large (relative to ion dimensions) pores.

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).

Kinetics and Mechanism of Decomposition of 1,3-Bis(4-methylphenyl)triazene Catalyzed with Substituted Benzoic Acids in 25% Aqueous Methanol-General or Specific Catalysis?

1994 ◽  
Vol 59 (9) ◽  
pp. 2029-2041
Author(s):  
Oldřich Pytela ◽  
Taťjana Nevěčná
Keyword(s):  
Benzoic Acids ◽  
Hammett Equation ◽  
Aqueous Methanol ◽  
Mechanism Of Decomposition ◽  
Kinetics Of Decomposition ◽  
Independent Variable ◽  
Amino Derivatives ◽  
Substituted Benzoic Acids ◽  
The Individual ◽  
Kinetics Of

The kinetics of decomposition of 1,3-bis(4-methylphenyl)triazene catalyzed with 13 substituted benzoic acids of various concentrations have been measured in 25 vol.% aqueous methanol at 25.0 °C. The rate constants observed (297 data) have be used as values of independent variable in a series of models of the catalyzed decomposition. For the catalytic particles were considered the undissociated acid, its conjugated base, and the proton in both the specific and general catalyses. Some models presumed formation of reactive or nonreactive complexes of the individual reactants. The substituent effect is described by the Hammett equation. The statistically best model in which the observed rate constant is a superposition of a term describing the dependence on proton concentration and a term describing the dependence on the product of concentrations of proton and conjugated base is valid with the presumption of complete proton transfer from the catalyst acid to substrate, which has been proved. The behaviour of 4-dimethylamino, 4-amino, and 3-amino derivatives is anomalous (lower catalytic activity as compared with benzoic acid). This supports the presumed participation of conjugated base in the title process.

Kinetics of esterification of monoisopropylphenols with phosphoryl trichloride

1989 ◽  
Vol 54 (5) ◽  
pp. 1311-1317
Author(s):  
Miroslav Magura ◽  
Ján Vojtko ◽  
Ján Ilavský
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Reaction Rates ◽  
Activation Energies ◽  
The Individual ◽  
Kinetics Of

The kinetics of liquid-phase isothermal esterification of POCl3 with 2-isopropylphenol and 4-isopropylphenol have been studied within the temperature intervals of 110 to 130 and 90 to 110 °C, respectively. The rate constants and activation energies of the individual steps of this three-step reaction have been calculated from the values measured. The reaction rates of the two isomers markedly differ: at 110 °C 4-isopropylphenol reacts faster by the factors of about 7 and 20 for k1 and k3, respectively. This finding can be utilized in preparation of mixed triaryl phosphates, since the alkylation mixture after reaction of phenol with propene contains an excess of 2-isopropylphenol over 4-isopropylphenol.

Validation of the Chinese Version of the Multidimensional Workaholism Scale

2021 ◽  
pp. 106907272199427
Author(s):  
Yan Xu ◽  
Chaoping Li
Keyword(s):  
Factor Analysis ◽  
Reliability And Validity ◽  
Well Being ◽  
Chinese Version ◽  
Full Time ◽  
Work Family Conflict ◽  
Working Adults ◽  
Work Family ◽  
The Individual ◽  
Two Stages

The aim of this study was to translate the Multidimensional Workaholism Scale (MWS) into Chinese and then test its reliability and validity among full-time Chinese employees in two stages. In Study 1 ( N = 220), the MWS was translated and exploratory factor analysis was conducted resulting in a four-factor solution consistent with the original MWS: motivational, cognitive, emotional, and behavioral. In Study 2 ( N = 425), confirmatory factor analysis showed that a four-factor, bifactor model was the best fit for the data. Configural, metric, and scalar invariance models were tested which demonstrated that the Chinese version of the MWS did not differ across gender, age, and job position groups. Finally, workaholism and engagement were related and distinct from one another, and they correlated with emotional exhaustion, work-family conflict and life well-being uniquely. This study indicated that the Chinese version of the MWS is a valid and reliable tool for Chinese employees, and this has important practical implications for the individual health and career development of Chinese working adults.

scholarly journals THE KINETICS OF PENETRATION

1937 ◽  
Vol 20 (5) ◽  
pp. 737-766 ◽  
Author(s):  
A. G. Jacques
Keyword(s):  
Sea Water ◽  
Surface Layers ◽  
Marked Contrast ◽  
External Concentration ◽  
Protoplasmic Surface ◽  
Kinetics Of ◽  
External Ph

When 0.1 M NaI is added to the sea water surrounding Valonia iodide appears in the sap, presumably entering as NaI, KI, and HI. As the rate of entrance is not affected by changes in the external pH we conclude that the rate of entrance of HI is negligible in comparison with that of NaI, whose concentration is about 107 times that of HI (the entrance of KI may be neglected for reasons stated). This is in marked contrast with the behavior of sulfide which enters chiefly as H2S. It would seem that permeability to H2S is enormously greater than to Na2S. Similar considerations apply to CO2. In this respect the situation differs greatly from that found with iodide. NaI enters because its activity is greater outside than inside so that no energy need be supplied by the cell. The rate of entrance (i.e. the amount of iodide entering the sap in a given time) is proportional to the external concentration of iodide, or to the external product [N+]o [I-lo, after a certain external concentration of iodide has been reached. At lower concentrations the rate is relatively rapid. The reasons for this are discussed. The rate of passage of NaI through protoplasm is about a million times slower than through water. As the protoplasm is mostly water we may suppose that the delay is due chiefly to the non-aqueous protoplasmic surface layers. It would seem that these must be more than one molecule thick to bring this about. There is no great difference between the rate of entrance in the dark and in the light.

The effect of external salinity on drinking rate and rectal secretion in the larvae of the saline-water mosquito Aedes taeniorhynchus

1977 ◽  
Vol 66 (1) ◽  
pp. 97-110
Author(s):  
T. J. Bradley ◽  
J. E. Phillips
Keyword(s):  
Sea Water ◽  
External Medium ◽  
Narrow Range ◽  
Saline Water ◽  
Fluid Secretion ◽  
Osmotic Concentration ◽  
Drinking Rate ◽  
Aedes Taeniorhynchus ◽  
External Salinity ◽  
Kinetics Of

1. The drinking rate of the saline-water mosquito larva Aedes taeniorhyncus (100 nl.mg-1.h-1) is unaffected by the salinity of the external medium, but is directly proportional to the surface area of the animal. 2. Haemolymph Na+, Mg2+, K+, Cl-, SO42- and osmotic concentrations were measured in larvae adapted to 10%, 100% and 200% seawater and were found to be regulated within a narrow range. 3. With the exception of potassium, ionic concentrations in rectal secretion were found to increase with increasing concentrations of the sea water in which larvae were reared. 4. The osmotic concentration of rectal secretion was unaffected by changes in haemolymph osmotic concentration but did rise when sodium or chloride concentrations of the haemolymph were increased. High levels of these ions also stimulated the rate of fluid secretion. 5. Transport of chloride and sodium by the rectum exhibits the kinetics of allosteric rather than classical enzymes.

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 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.

scholarly journals Mineral composition and formation conditions of the Inkur tungsten deposit ores (Dzhidinsky ore field, South-Western Transbaikalia)

2020 ◽  
Vol 43 (3) ◽  
pp. 290-306
Author(s):  
L. B. Damdinova ◽  
B. B. Damdinov
Keyword(s):  
Mineral Composition ◽  
Tungsten Deposit ◽  
Homogeneous Solutions ◽  
Western Transbaikalia ◽  
Low Salinity ◽  
Mineral Associations ◽  
Formation Conditions ◽  
The Individual ◽  
Two Stages ◽  
Petrographic Description

The aim of the study is to clarify the mineral composition and determine the conditions of the formation of the quartz-hubnerite veins of the Inkur stockwork tungsten deposit (the Dzhidinsky ore field, South-Western Transbaikalia). The research methods include a mineralogical and petrographic description of the ore quartz-hubnerite veins; an electron microprobe analysis of the mineral associations; thermometry, cryometry, and Raman spectroscopy of the individual fluid inclusions in quartz, fluorite, hubnerite, and muscovite. The mineralogical and petrographic studies has made it possible to clarify the mineral composition of the Inkur deposit ores and determine the mineral paragenesis formation sequence. The fluid inclusion studies have established that the ore deposition was occurring in the relatively low-salinity (~5.7–14.6 wt. % eq. NaCl) homogeneous solutions due to a decrease of the temperature. The study of the salt composition of the solutions has identified Ca chloride as a prevailing component, with NaCl, KCl, and MgCl as admixtures. CO2 and N2 have been identified in the gas phase of inclusions. Two stages of mineral formation have been defined: high-temperature (≥300 °С) and low-temperature (≥2.00–300 °С). The conducted studies allow qualitative estimation of the chemical composition of the ore-forming solutions. It has been established that one of the main factors of the hubnerite deposition is a temperature factor.

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.

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