A Critical Study of the Evidence for Peripheral Inhibitory Axons in Insects

1968 ◽  
Vol 49 (1) ◽  
pp. 201-222
Author(s):  
P. N. R. USHERWOOD
Keyword(s):  
Potassium Concentration ◽  
Chloride Concentration ◽  
Chloride Ions ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Critical Study ◽  
Muscle Fibres ◽  
High Concentration ◽  
Bathing Medium

1. The metathoracic anterior coxal adductor (a.c.a.) muscle of the locust and the grasshopper is innervated by a peripheral inhibitory axon similar to the inhibitory axon which innervates the metathoracic extensor tibiae muscles of these insects. No evidence was found to justify calling this axon an inhibitory-conditioning axon. 2. Hyperpolarizing inhibitory postsynaptic potentials (IPSPs) are normally recorded from a.c.a. muscle fibres during stimulation of this axon, and if the bathing medium contains a high concentration of potassium ions the tonic fibres of the a.c.a. muscle relax slightly during inhibitory stimulation. 3. The IPSPs are chloride potentials and can be converted to depolarizing responses by changing either the external or internal chloride concentration of the a.c.a. muscle fibres. Depolarizing IPSPs are frequently accompanied by small contractions of a.c.a. muscle fibres innervated by the inhibitory axon. 4. The a.c.a. muscle fibres are permeable to potassium and chloride ions but influx of potassium chloride is much faster than efflux. Therefore when a.c.a. muscle fibres are loaded with chloride by exposing them to high-K saline (20-100 m-equiv. potassium/l.) and are then returned to normal (10 m-equiv. potassium/l.) saline the internal chloride concentration remains elevated for some time and during this period the equilibrium potential for the inhibitory response is less negative than the resting potential and the IPSPs are depolarizing. 5. Depolarizing IPSPs are usually recorded from a.c.a. muscle fibres of locusts and grasshoppers when these fibres are transferred from their normal bathing medium, haemolymph, to 10 K saline. Probably the main reason for this reversal of the IPSPs is the entry of KCl into the muscle fibres during dissection of the nerve-muscle preparations. Large quantities of KCl would be released into the environment surrounding these preparations from muscle fibres cut and removed during dissection. 6.Depolarizing IPSPs were more frequently recorded from muscle fibres of grassfed locusts than from fibres of starved locusts. The potassium concentration of haemolymph of grass fed locusts is higher than that of locust saline (10 m-equiv./l.). 7. The potassium concentration of locust haemolymph presumably fluctuates in vivo but these fluctuations are too slow to affect the sign of the IPSP. The IPSPs are therefore always hyperpolarizing in vivo. 8. The effect of changes in the potassium concentration of the bathing medium on the magnitude and polarity of the IPSP could account for the diverse responses recorded previously from a.c.a. muscle fibres of locusts and grasshoppers.

Long-term Adaptations of Sabella Giant Axons to Hyposmotic Stress

1978 ◽  
Vol 75 (1) ◽  
pp. 253-263
Author(s):  
J. E. TREHERNE ◽  
Y. PICHON
Keyword(s):  
Sea Water ◽  
Potassium Concentration ◽  
Resting Potential ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Appreciable Change ◽  
Axon Membrane ◽  
Giant Axons

Reprint requests should be addressed to Dr Treherne. Sabella is a euryhaline osmoconformer which is killed by direct transfer to 50% sea water, but can adapt to this salinity with progressive dilution of the sea water. The giant axons were adapted to progressive dilution of the bathing medium (both in vivo and in vitro) and were able to function at hyposmotic dilutions (down to 50%) sufficient to induce conduction block in unadapted axons. Hyposmotic adaptation of the giant axon involves a decrease in intracellular potassium concentration which tends to maintain a relatively constant resting potential during adaptation despite the reduction in external potassium concentration. There is no appreciable change in the intracellular sodium concentration, but the relative sodium permeability of the active membrane increases during hyposmotic adaptation. This increase partially compensates for the reduction in sodium gradient across the axon membrane, during dilution of the bathing media, by increasing the overshoot of the action potentials recorded in hyposmotically adapted axons.

scholarly journals One-Step Synthesis of Green Fluorescent Carbon Dots for Chloride Detecting and for Bioimaging

2021 ◽  
Vol 9 ◽  
Author(s):  
Juan Yue ◽  
Ling Yu ◽  
Li Li ◽  
Pai Liu ◽  
Qian Mei ◽  
...  
Keyword(s):  
Carbon Dots ◽  
Limit Of Detection ◽  
Chloride Concentration ◽  
Chloride Ion ◽  
Silver Ions ◽  
Chloride Ions ◽  
Cell Functions ◽  
Green Fluorescent ◽  
Fluorescent Carbon

The chloride ion is an essential ion in organisms, which plays an important role in maintaining normal cell functions. It is involved in many cell activities, such as cell proliferation, cell excitability regulation, immune response, and volume regulation. Accurate detection of the chloride ion can balance its concentration in vivo, which is of great significance. In this study, we developed a green fluorescent carbon quantum dot to detect chloride concentration through the “off–on” mechanism. First, the fluorescence of carbon dots is quenched by the complex of sulfhydryl and silver ions on the surface of carbon dots. Then, the addition of chloride ions pulls away the silver ions and restores the fluorescence. The fluorescence recovery is linearly related to the concentration of chloride ions, and the limit of detection is 2.817 μM, which is much lower than those of other reported chloride probes. Besides, cell and zebrafish experiments confirmed the biosafety and biocompatibility of the carbon dots, which provided a possibility for further applications in bioimaging in vivo.

Contribution of changes in the chloride driving force to the fading of I GABA in frog melanotrophs

2000 ◽  
Vol 278 (3) ◽  
pp. E430-E443 ◽  
Author(s):  
Frank le Foll ◽  
Olivier Soriani ◽  
Hubert Vaudry ◽  
Lionel Cazin
Keyword(s):  
Driving Force ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Resting Potential ◽  
Perforated Patch ◽  
Induced Currents ◽  
Patch Configuration ◽  
Intracellular Chloride Concentration ◽  
Current Reversal

Chloride redistribution during type A γ-aminobutyric acid (GABAA) currents ( I GABA) has been investigated in cultured frog pituitary melanotrophs with imposed intracellular chloride concentration ([Cl−]i) in the whole cell configuration or with unaltered [Cl−]i using the gramicidin-perforated patch approach. Prolonged GABA exposures elicited reproducible decaying currents. The decay of I GABAwas associated with both a transient fall of conductance ( g GABA) and shift of current reversal potential ( E GABA). The shift of E GABAappeared to be time and driving force dependent. In the gramicidin-perforated patch configuration, repeated GABA exposures induced currents that gradually vanished. The fading of I GABA was due to persistent shifts of E GABA as a result of g GABArecovering from one GABA application to another. In cells alternatively clamped at potentials closely flanking resting potential and submitted to a train of brief GABA pulses, a reversal of I GABA was observed after 150 s recording. It is demonstrated that, in intact frog melanotrophs, shifts of E GABA combine with genuine receptor desensitization to depress I GABA. These findings strongly suggest that shifts of E GABA may act as a negative feedback, reducing the bioelectrical and secretory responses induced by an intense release of GABA in vivo.

The Water Balance of a Serpulid Polychaete, Mercierella Enigmatica (Fauvel)

1974 ◽  
Vol 60 (2) ◽  
pp. 351-370
Author(s):  
HELEN LE B. SKAER
Keyword(s):  
Action Potential ◽  
Electrical Activity ◽  
Muscle Cell ◽  
Cell Membranes ◽  
External Medium ◽  
Ionic Composition ◽  
Chloride Concentration ◽  
Chloride Ions ◽  
Resting Potential ◽  
Inward Current

1. The electrical activity of the two types of longitudinal muscles of an osmoconforming polychaete worm, Mercierella enigmatica, have been studied in media of widely varying osmotic and ionic composition. Activity persists practically unaltered in both types of muscle cell. 2. The possible effects of osmotically induced changes in cell volume on the ionic gradients across the cell membranes are considered. It is concluded that the normal gradients are unlikely to be maintained as a result of such changes. 3. The involvement of ion pumps in the maintenance of the normal gradients across the muscle cell membranes has been studied using specific and metabolic poisons. It is evident that the persistence of electrical activity in media of altered ionic content does not depend on the sodium-potassium exchange pump. 4. The ionic basis of the overshoot of action potentials recorded from cells of the small resting potential type has been studied. It is concluded that calcium ions but not sodium ions are responsible for the inward current although there is a component of the inward current carried by some other as yet unidentified ion. 5. Alterations in the external concentrations of chloride ions are found to alter both the height of the overshoot and the length of the action potential. 6. Profound alterations in the overshoot height are produced only when the normal ratio of calcium to chloride concentration in the external medium is altered. Possible mechanisms to explain these effects are discussed. 7. It is suggested that the stability of the action potential in the muscle cells of M. enigmatica, despite large fluctuations in the salinity of the external medium, depends on the constancy of the ratios between the concentrations of the ions in the fluids bathing the cells and not on the absolute concentrations of the ions.

scholarly journals Shift of Intracellular Chloride Concentration in Ganglion and Amacrine Cells of Developing Mouse Retina

2006 ◽  
Vol 95 (4) ◽  
pp. 2404-2416 ◽  
Author(s):  
Ling-Li Zhang ◽  
Hemal R. Pathak ◽  
Douglas A. Coulter ◽  
Michael A. Freed ◽  
Noga Vardi
Keyword(s):  
Gaba Receptors ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Amacrine Cells ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Mouse Retina ◽  
Intracellular Chloride ◽  
Excitatory Action ◽  
Intracellular Chloride Concentration

GABA and glycine provide excitatory action during early development: they depolarize neurons and increase intracellular calcium concentration. As neurons mature, GABA and glycine become inhibitory. This switch from excitation to inhibition is thought to result from a shift of intracellular chloride concentration ([Cl−]i) from high to low, but in retina, measurements of [Cl−]i or chloride equilibrium potential ( ECl) during development have not been made. Using the developing mouse retina, we systematically measured [Cl−]i in parallel with GABA's actions on calcium and chloride. In ganglion and amacrine cells, fura-2 imaging showed that before postnatal day (P) 6, exogenous GABA, acting via ionotropic GABA receptors, evoked calcium rise, which persisted in HCO3−- free buffer but was blocked with 0 extracellular calcium. After P6, GABA switched to inhibiting spontaneous calcium transients. Concomitant with this switch we observed the following: 6-methoxy- N-ethylquinolinium iodide (MEQ) chloride imaging showed that GABA caused an efflux of chloride before P6 and an influx afterward; gramicidin-perforated-patch recordings showed that the reversal potential for GABA decreased from −45 mV, near threshold for voltage-activated calcium channel, to −60 mV, near resting potential; MEQ imaging showed that [Cl−]i shifted steeply around P6 from 29 to 14 mM, corresponding to a decline of ECl from −39 to −58 mV. We also show that GABAergic amacrine cells became stratified by P4, potentially allowing GABA's excitatory action to shape circuit connectivity. Our results support the hypothesis that a shift from high [Cl−]i to low causes GABA to switch from excitatory to inhibitory.

Study of the Susceptibility of Oxygen-Free Phosphorous Doped Copper to Corrosion in Simulated Groundwater in the Presence of Chloride and Sulfide

2006 ◽  
Vol 985 ◽  
Author(s):  
Ivan Escobar ◽  
Claudia Lamas ◽  
Lars Werme ◽  
Virginia Oversby
Keyword(s):  
Electrochemical Impedance ◽  
Copper Chloride ◽  
Chloride Concentration ◽  
Copper Surface ◽  
Chloride Ions ◽  
Transport Processes ◽  
Ion Concentration ◽  
Spent Fuel ◽  
High Concentration ◽  
Chloride Complexes

AbstractCopper of the quality oxygen free and high conductivity, doped with phosphorus (Cu OFP) has been chosen as the material for the fabrication of high level nuclear waste containers in Sweden. This material will be the corrosion barrier for spent fuel in the environment of a deep geological repository. It is planned that the service life of this container will be 100,000 years. During this time water with high concentration of chloride ions might come in contact with the copper surface. If pH conditions are appropriate, this might cause pitting corrosion. This work reports a study of the susceptibility of Cu OFP to corrosion when chloride ions are present, both deionized water (DW) and in standard synthetic underground water (SUW). The techniques used were electrochemical methods such as corrosion potential evolution and Tafel curves. In addition, this system was studied with Electrochemical Impedance Spectroscopy (EIS). We also used characterization techniques such as Scanning Electronic Microscopy (SEM), Energy Disperse Spectroscopy (EDS) . The main conclusions are that copper is more susceptible to corrosion at high chloride ion concentration. Additionally, when the chloride concentration is low, it is possible to form copper chloride crystals, but at the highest concentration, copper chloride complexes are formed, leaving the copper surface without deposits. When the chloride concentration is low (<0.1 M) the corrosion process is mainly controlled by diffusion, while at higher concentrations (0.1M to 1M) corrosion is controlled by transport processes. At low concentration of sulfide ( <3*10-5M), copper corrosion in the presence of chloride is controlled by diffusional processes.

The regulation of chloride homeostasis in the small nonspiking visual interneurons of the fly compound eye

1994 ◽  
Vol 71 (4) ◽  
pp. 1381-1389 ◽  
Author(s):  
R. O. Uusitalo ◽  
M. Weckstrom
Keyword(s):  
Time Constant ◽  
Compound Eye ◽  
Substrate Inhibition ◽  
Potassium Acetate ◽  
Physiological Effect ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Sodium Load ◽  
Chloride Accumulation

1. We have used intracellular recordings and ionophoretic injections in vivo to investigate the ion exchange mechanisms responsible for the maintenance of the ion gradients in the large monopolar cells (LMCs) of the first optic ganglion of the blowfly, Calliphora vicinia. 2. Ionophoretic chloride injections caused a rapid approximately 20-mV depolarization of the resting potential (Erp) and abolished or even reversed the light-ON response (OR), which is caused by histamine-gated chloride conductance, as the chloride equilibrium potential (ECl) was increased beyond the Erp, i.e., 50 mV upward. Ionophoretic sodium injections were found to mimic the action of the ionophoretic chloride injections and thus also to cause chloride accumulation inside the cell. 3. Ionophoretic injections of bicarbonate only had the effect of hyperpolarizing the Erp by 5-15 mV for 1-25 s, but chloride gradient, i.e., ECl remained unchanged. Intracellular proton load caused depolarization of the Erp by 15 +/- 5 mV (mean +/- SE) for 20-25 s and a slight 15 +/- 5-mV decrease of the peak OR. Ionophoretic injections of potassium, acetate, and furosemide failed to cause any physiological effect. 4. The time constant for the recovery of the peak OR after sodium load increased linearly as a function of injected charge whereby the time constant for the recovery after chloride accumulation increased slowly up to 50 nC of injected charge, after which it increased rapidly, possibly indicating substrate inhibition. The time constant for the recovery of peak OR after sodium load was from 5 to 65 nC greater than that of chloride.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretion by the Malpighian Tubules of Rhodnius. The Movements of Ions and Water

1969 ◽  
Vol 51 (1) ◽  
pp. 71-97 ◽  
Author(s):  
S. H. P. MADDRELL
Keyword(s):  
Chloride Concentration ◽  
Fluid Secretion ◽  
Chloride Ions ◽  
Malpighian Tubules ◽  
Minor Role ◽  
Special Role ◽  
Sodium Ions ◽  
Bathing Medium ◽  
Rapid Flow ◽  
Bathing Fluid

1. The Malpighian tubules of Rhodnius will secrete at a normal rate in solutions containing no potassium ions and the rate is unaffected by changes in the potassium concentration, when the balance of cationic concentration is made up by sodium ions. 2. In the absence of sodium ions the rate of secretion is much reduced. The addition of very small amounts of sodium-containing solution brings about an abrupt recovery in the rate and thereafter the rate is unaffected by further increases in the sodium concentration. 3. In solutions containing either sodium or potassium with choline making up the balance of monovalent cations, the rate of fluid secretion depends linearly on the concentration of either sodium or potassium. 4. The tubules will concentrate either sodium or potassium when they are present at low concentration in the bathing fluid, even in the face of a very much larger concentration of the other cation. This suggests that there are separate mechanisms for the handling of these two ions. 5. Secretion can be supported by a solution containing ammonium ions in place of sodium and potassium. The tubules behave, at least in the short term, as if they were unable to distinguish ammonium from potassium. 6. Chloride ions appear to play a special role in that only bromide ions and, to a limited extent, nitrate ions will substitute for them. The rate of secretion depends linearly on the chloride concentration. 7. The tubules secrete a fluid which is practically iso-osmotic to the bathing fluid. The rate of secretion depends inversely on the osmolarity of the bathing fluid. The rate of movement of solute is little affected by these changes of osmolarity. It appears that water movements follow, and are closely linked with, solute movements. 8. Copper, cyanide, iodoacetate and azide ions and 2,4-dinitrophenol all stop secretion when added to the bathing medium. Ouabain, acetazolamide and mammalian ADH all have no effect on the rate of secretion and ouabain has no effect on the composition of the secreted fluid. 5-Hydroxytryptamine (serotonin) will stimulate a rapid flow of secretion. 9. Apparent neurosecretory axons have been found which supply the tubules. They do not contain enough diuretic activity to do more than play a minor role in diuresis. They may contribute to the rapid onset of diuresis or may affect the Malpighian tubules in some other way. 10. The evidence suggests that the tubules function by secreting chloride, potassium and sodium ions into the lumen (it is speculated that this may conceivably involve the active transport of all three ions) and that water movements closely follow these ion movements so that a rapid flow of iso-osmotic fluid is achieved.

A voltage-gated chloride conductance in rat cultured astrocytes

1986 ◽  
Vol 228 (1252) ◽  
pp. 267-288 ◽  
Keyword(s):  
Time Course ◽  
Reversal Potential ◽  
Outward Current ◽  
Chloride Ions ◽  
Chloride Conductance ◽  
Equilibrium Potential ◽  
Free Calcium ◽  
Patch Clamp Technique ◽  
Bathing Medium ◽  
Cultured Astrocytes

Large voltage-dependent outward currents are recorded with the wholecell patch-clamp technique from rat cultured astrocytes under conditions where an outward movement of potassium ions is excluded (either by blockage of the potassium channels pharmacologically or by replacement of the internal potassium by the impermeant large organic cation N -methyl-( + )-glucamine). The current, which is activated at potentials more positive than —40 to —50 mV, is normally carried by an inward movement of chloride ions. Its reversal potential is the same as the chloride equilibrium potential. With depolarization to +60 mV (for 225 ms) little or no inactivation of the current occurs: with depolarizations to +90 to +110 mV a time-dependent decay is seen. The current, which is often not marked immediately after formation of the whole-cell clamp, generally increases over a period of a few minutes to a maximum (after which it usually declines), as if some as yet unknown intracellular factor keeping the channels closed were being washed away from the membrane. The time course of this phenomenon is not affected by changing of the internal free calcium concentration (from 10 -8 to 10 -6 m) or by an intracellular mixture of cyclic AMP (1 mm), ATP (4 mm) and Mg + (2 mm). The conductance is slightly increased when the chloride of the bathing medium is replaced by bromide; is much reduced on replacement by methylsulphate, sulphate, isethionate, or acetate; and is virtually abolished on replacement by the large anion gluconate. The outward current is inhibited by the disulphonate stilbenes DIDS and SITS; this blocking action was initially partly reversible, although never completely so. It is suggested that the chloride conductance plays a role in the spatial buffering of potassium by astrocytes.

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