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 Membrane Potentials of the Lobster Giant Axon Obtained by Use of the Sucrose-Gap Technique

1962 ◽  
Vol 45 (6) ◽  
pp. 1195-1216 ◽  
Author(s):  
Fred J. Julian ◽  
John W. Moore ◽  
David E. Goldman
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Sea Water ◽  
Sucrose Solution ◽  
Chloride Concentration ◽  
Giant Axon ◽  
Membrane Resistance ◽  
Resting Potential ◽  
Gap Technique ◽  
Sucrose Gap

A method similar to the sucrose-gap technique introduced be Stäpfli is described for measuring membrane potential and current in singly lobster giant axons (diameter about 100 micra). The isotonic sucrose solution used to perfuse the gaps raises the external leakage resistance so that the recorded potential is only about 5 per cent less than the actual membrane potential. However, the resting potential of an axon in the sucrose-gap arrangement is increased 20 to 60 mv over that recorded by a conventional micropipette electrode when the entire axon is bathed in sea water. A complete explanation for this effect has not been discovered. The relation between resting potential and external potassium and sodium ion concentrations shows that potassium carries most of the current in a depolarized axon in the sucrose-gap arrangement, but that near the resting potential other ions make significant contributions. Lowering the external chloride concentration decreases the resting potential. Varying the concentration of the sucrose solution has little effect. A study of the impedance changes associated with the action potential shows that the membrane resistance decreases to a minimum at the peak of the spike and returns to near its initial value before repolarization is complete (a normal lobster giant axon action potential does not have an undershoot). Action potentials recorded simultaneously by the sucrose-gap technique and by micropipette electrodes are practically superposable.

Afterhyperpolarization Current in Myenteric Neurons of the Guinea Pig Duodenum

2001 ◽  
Vol 85 (5) ◽  
pp. 1941-1951 ◽  
Author(s):  
Fivos Vogalis ◽  
John B. Furness ◽  
Wolf A. A. Kunze
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Dwell Time ◽  
High Probability ◽  
Resting Potential ◽  
Bathing Solution ◽  
Inward Current ◽  
Current Pulses ◽  
Mean Variance ◽  
Small Conductance

Whole cell patch and cell-attached recordings were obtained from neurons in intact ganglia of the myenteric plexus of the guinea pig duodenum. Two classes of neuron were identified electrophysiologically: phasically firing AH neurons that had a pronounced slow afterhyperpolarization (AHP) and tonically firing S neurons that lacked a slow AHP. We investigated the properties of the slow AHP and the underlying current ( I AHP) to address the roles of Ca2+ entry and Ca2+ release in the AHP and the characteristics of the K+channels that are activated. AH neurons had a resting potential of −54 mV and the AHP, which followed a volley of three suprathreshold depolarizing current pulses delivered at 50 Hz through the pipette, averaged 11 mV at its peak, which occurred 0.5–1 s following the stimulus. The duration of these AHPs averaged 7 s. Under voltage-clamp conditions, I AHP's were recorded at holding potentials of −50 to −65 mV, following brief depolarization of AH neurons (20–100 ms) to positive potentials (+35 to +50 mV). The null potential of the I AHP at its peak was −89 mV. The AHP and I AHP were largely blocked by ω-conotoxin GVIA (0.6–1 μM). Both events were markedly decreased by caffeine (2–5 mM) and by ryanodine (10–20 μM) added to the bathing solution. Pharmacological suppression of the I AHP with TEA (20 mM) or charybdotoxin (50–100 nM) unmasked an early transient inward current at −55 mV following step depolarization that reversed at −34 mV and was inhibited by niflumic acid (50–100 μM). Mean-variance analysis performed on the decay of the I AHPrevealed that the AHP K+ channels have a mean chord conductance of ∼10 pS, and there are ∼4,000 per AH neuron. Spectral analysis showed that the AHP channels have a mean open dwell time of 2.8 ms. Cell-attached patch recordings from AH neurons confirmed that the channels that open following action currents have a small unitary conductance (10–17 pS) and open with a high probability (≤0.5) within the first 2 s following an action potential. These results indicate that the AHP is largely a consequence of Ca2+ entry through ω-conotoxin GVIA-sensitive Ca2+ channels during the action potential, Ca2+-triggered Ca2+ release from caffeine-sensitive stores and the opening of Ca2+-sensitive small-conductance K+ channels.

scholarly journals Membrane Currents in Mammalian Ventricular Heart Muscle Fibers Using a Voltage-Clamp Technique

1971 ◽  
Vol 57 (3) ◽  
pp. 290-296 ◽  
Author(s):  
Gerhard Giebisch ◽  
Silvio Weidmann
Keyword(s):  
Action Potential ◽  
Outward Current ◽  
Time Dependent ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Initial Amplitude ◽  
Inward Current ◽  
Gap Technique ◽  
Sucrose Gap

Bundles of sheep ventricular fibers were voltage-clamped utilizing a modified sucrose gap technique and intracellular voltage control. An action potential was fired off in the usual way, and the clamp circuit was switched on at preselected times during activity. Clamping the membrane back to its resting potential during the early part of an action potential resulted in a surge of inward current. The initial amplitude of this current surge decreased as the clamp was switched on progressively later during the action potential. Inward current decreasing as a function of time was also recorded if the membrane potential was clamped beyond the presumed K equilibrium potential (to -130 mv). Clamping the membrane to the inside positive range (+40 mv to +60 mv) at different times of an action potential resulted in a step of outward current which was not time-dependent. The results suggest that normal repolarization of sheep ventricle depends on a time-dependent decrease of inward current (Na, Ca) rather than on a time-dependent increase of outward current (K).

scholarly journals Calcium Ions and the Action Potential in Nitella

1962 ◽  
Vol 15 (1) ◽  
pp. 69 ◽  
Author(s):  
GP Findlay
Keyword(s):  
Cell Membrane ◽  
Action Potential ◽  
Electrical Activity ◽  
Calcium Ions ◽  
Current Flow ◽  
External Medium ◽  
Feedback Circuit ◽  
Predetermined Level ◽  
Voltage Clamping ◽  
Main Factor

Experiments are described in which a "voltage� clamping" technique has been applied to large ecorticate internodal cells of the freshwater alga Nitella. In this technique, a feedback circuit is used to change the potential difference between the vacuole of the cell and the external medium to some predetermined level and maintain it as close as possible to this level during the electrical activity of the cell. It is shown that the main factor in the phenomena of potential change and current flow, during the initial stages of the action potential in Nitella, is a tran-sient increase in the permeability of the cell membrane to calcium ions, and a consequent flow of these ions into the cell from the external medium.

Electrical activity alterations induced by chronic absorption of lindane (γ-hexachlorocyclohexane) trace concentrations in adult rat heart

2005 ◽  
Vol 83 (3) ◽  
pp. 243-251 ◽  
Author(s):  
Martin-Pierre Sauviat ◽  
Suzanne Bouvet ◽  
Gaston Godeau ◽  
Nicole Pages
Keyword(s):  
Left Ventricle ◽  
Action Potential ◽  
Electrical Activity ◽  
Heart Muscle ◽  
Female Rats ◽  
Resting Potential ◽  
Muscle Membrane ◽  
Papillary Muscles ◽  
Adult Rat ◽  
Trace Concentrations

The heart of adult rat offspring, born to mothers treated with trace concentrations of lindane (0.5 to 2 ppb) through a beverage and to mothers chronically treated with lindane (CL-T) with the same trace concentration, also through a beverage, during lactation and growth has a round shape and accumulates lindane. The left ventricle (LV) presents a hypertrophied area, atrophied papillary muscles, and unorganized collagen bundles and layers. These observations led us to study the electrical activity of their left ventricle papillary muscles (LVPM) by recording action potential using intracellular microelectrodes. CL-T shortened LVPM action potential duration (APD): 1 ppb shortened the plateau; 2 ppb shortened the plateau and the slow repolarizing phase. In CL-T (2 ppb) and untreated groups, low temperature (22 °C) decreased the resting potential and prolonged APD. TEA (tetraethylammonium; 1-2 mmol/L) partially lengthened CL-T (2 ppb lindane) APD. Quinidine (0.2 mmol/L) and E-4031 (10 nmol/L) prolonged CL-T APD, suggesting that the rapid delayed outward K+ current (IKr) was increased. Our results indicate the silent effects of chronic exposure to trace concentrations of lindane on the morphological and electrical activity of heart muscle. They demonstrate that chronic lindane treatment of female rats alters the tissue integrity and electrical activity in the LV of their offspring.Key words: heart muscle, membrane potential, lindane, K+ channel.

scholarly journals Ionic dependence of secretory and electrical activity evoked by elevated K+ in a peptidergic neurosecretory system

1984 ◽  
Vol 113 (1) ◽  
pp. 289-321 ◽  
Author(s):  
I. M. Cooke ◽  
B. A. Haylett
Keyword(s):  
Electrical Activity ◽  
Normal Saline ◽  
Intracellular Recording ◽  
Resting Potential ◽  
Neurosecretory System ◽  
Repetitive Firing ◽  
Inward Current ◽  
Dependent Inactivation ◽  
High K ◽  
Net Uptake

Secretion of the octapeptide erythrophore- (red pigment-) concentrating hormone (ECH, RPCH) and extracellularly monitored electrical activity were followed simultaneously from individual, isolated sinus glands (neurohaemal organs), of the crab Cardisoma carnifex. Following introduction of saline having elevated [K], 100–196 mmol l-1 (5–11 X normal), secretion (bioassayed from 1-min fractions during continuous perfusion) increases from barely detectable (less than 1 fmol min-1) to a peak, average 31 fmol min-1, within 5 min, and immediately subsides. Additional responses are obtainable following a period, greater than 30 min, of normal saline perfusion. Secretory responses to K are Ca-dependent. If Ca is restored (in high K) following perfusion in 0-Ca, high K, only a small secretory response is observed. Addition of Mn (10 mmol l-1, normal Ca) reduces secretion to one-tenth. Increased net uptake of 45Ca of 2.5- to 6-fold is observed in individual sinus glands exposed to 10 X K compared to paired, unstimulated organs. The pattern and Ca-dependence of secretory responses to K are unaffected, but the amount of secretion is augmented in Na-deficient or TTX-containing salines. Intracellular recording confirms that brief (10–40 s) bouts of intense firing recorded extracellularly upon commencing a high K perfusion include repetitive firing by terminals, superimposed on rapid depolarization. Firing ceases as the membrane potential reaches a depolarized value (−18 to −15 mV for [K] 100–176 mmol l-1), which is then maintained until restoration of normal saline, when slow repolarization ensues. In 0-Ca, spontaneous impulse firing is increased, resting potential depolarized by 5 to 15 mV, but the bout of impulse firing and the maintained depolarization in response to K are similar. Thus, mechanisms of secretion of a crustacean peptide neurohormone appear closely similar to those of other systems characterized: responsiveness to elevated K, dependence on Ca, depolarization-, but not secretion-dependent inactivation, and lack of dependence on Na inward current. Intracellular recording here permits direct observation of electrical responses of terminals.

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.

Calcium dependent electrical activity in twitch muscle fibres of the frog

1976 ◽  
Vol 194 (1114) ◽  
pp. 141-150 ◽  
Keyword(s):  
Action Potential ◽  
Electrical Activity ◽  
Membrane Conductance ◽  
Chloride Ions ◽  
Muscle Fibres ◽  
Mean Values ◽  
Calcium Dependent ◽  
External Calcium

When twitch muscle fibres of the frog were equilibrated in chloride free saline with 2.5–20 mM tetraethylammonium sulphate [(TEA) 2 SO 4 ], the action potential was followed by a long depolarizing response. This response was greatly reduced by adding chloride ions (10 mM). In 20 mM (TEA) 2 SO 4 the response consisted of an initial depolarization of – 23 mV lasting several seconds, followed by a slow delayed spike reaching + 23 mV. After the delayed spike the cell remained continuously depolarized creeping to a steady depolarization of + 25 mV (mean values). The response can be attributed to an increase in membrane conductance to calcium since the phenomenon was abolished by removing external calcium or by adding cobalt or D-600, and was not greatly affected by reducing or removing external sodium or by adding tetrodotoxin.

scholarly journals PROLONGED ACTION POTENTIALS FROM SINGLE NODES OF RANVIER

1958 ◽  
Vol 42 (1) ◽  
pp. 137-162 ◽  
Author(s):  
Paul Mueller
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
External Medium ◽  
Resting Potential ◽  
Prolonged Action ◽  
Nodes Of Ranvier ◽  
Duration Of Action ◽  
Na Ions ◽  
Cathodal Current ◽  
Kinetics Of

The duration of action potentials from single nodes of Ranvier can be increased by several methods. Extraction of water from the node (e.g. by 2 to 3 M glycerin) causes increased durations up to 1000 msec. 1 to 5 min. after application of the glycerin the duration of the action potential again decreases to the normal value. Another type of prolonged action potential can be observed in solutions which contain K or Rb ions at concentrations between 50 mM and 2 M. The nodes respond only if the resting potential is restored by anodal current. The kinetics of these action potentials is slightly different. Their maximal durations are longer (up to 10 sec.). Like the normal action potential, they are initiated by cathodal make or anodal break. They also occur in external solutions which contain no sodium. The same type of action potentials as in KCl is found when the node is depolarized for some time (15 to 90 sec., 100 to 200 mv.) and is then stimulated by cathodal current. These action potentials require no K or Na ions in the external medium. Their maximal duration increases with the strength and duration of the preceding depolarization. The possible origin of the action potentials in KCl and after depolarization, and their relation to the normal action potentials and the negative after-potential are discussed.

Factors Influencing the Separation of Glu-Plasminogen Affinity Forms I and II by Affinity Chromatography

1984 ◽  
Vol 52 (03) ◽  
pp. 347-349 ◽  
Author(s):  
Daan W Traas ◽  
Bep Hoegee-de Nobel ◽  
Willem Nieuwenhuizen
Keyword(s):  
Affinity Chromatography ◽  
Dissociation Constants ◽  
Ionic Composition ◽  
Chloride Ions ◽  
Factors Influencing ◽  
Two Factors ◽  
Human Plasminogen

SummaryNative human plasminogen, the proenzyme of plasmin (E. C. 3.4.21.7) occurs in blood in two well defined forms, affinity forms I and II. In this paper, the feasibility of separating these forms of human native plasminogen by affinity chromatography, is shown to be dependent on two factors: 1) the ionic composition of the buffer containing the displacing agent: buffers of varying contents of sodium, Tris, phosphate and chloride ions were compared, and 2) the type of adsorbent. Two adsorbents were compared: Sepharose-lysine and Sepharose-bisoxirane-lysine. Only in the phosphate containing buffers, irrespective of the type of adsorbent, the affinity forms can be separated. The influence of the adsorbent can be accounted for by a large difference in dissociation constants of the complex between plasminogen and the immobilized lysine.

Sign in / Sign up

Export Citation Format

Share Document