A Regenerative Calcium Response in Paramecium

1972 ◽  
Vol 56 (3) ◽  
pp. 667-681
Author(s):  
YUTAKA NAITOH ◽  
ROGER ECKERT ◽  
KENNETH FRIEDMAN
Keyword(s):  
Surface Membrane ◽  
Maximum Amplitude ◽  
Outward Current ◽  
Fold Increase ◽  
Ion Concentration ◽  
Regenerative Response ◽  
Stimulus Current ◽  
Delayed Rectification ◽  
Graded Response ◽  
Maximum Rate Of Rise

1. Standard intracellular current-passing and recording techniques were used to investigate the electrical properties of the membrane of Paramecium caudatum. 2. The surface membrane produces regenerative depolarizations graded in amplitude and rate of rise with the intensity of applied outward current pulses. In a solution of 1 mM-CaCl2, 1 mM-KCl and 1 mM Tris-HCl at pH 7.2 and 18 °C the overshoot reaches a maximum amplitude of + 5 to + 15 mV, and shows a maximum rate of rise of about 7 V/sec. 3. The overshoot is insensitive to Li,+, Na+, Cl-, TTX and procaine, but increases slightly (up to 10 mV/10-fold rise in ion concentration) in the presence of K+, Rb+, Cs+, NH+4, Mg2+ and tetraethylammonium. 4. The overshoot increases 22-25 mV for each 10-fold increase in external [Ca]. Ba2+ and Sr2+ convert the graded response to one that is all-or-none. 5. Repolarization following the peak of the response is more rapid than expected from the time constant of the resting membrane, suggesting delayed rectification. 6. A conditioning depolarization causes inactivation of the regenerative response, and hyperpolarization depresses the response to a given stimulus current. Refractoriness persists for up to 200 msec after each response. 7. The regenerative response of the membrane is consistent with a transient increase in conductance to Ca2+ (Ba2+, Sr2+) with a consequent inwardly directed calcium current. This agrees with recent evidence that ciliary reversal (which accompanies depolarization) is produced by an influx of Ca2+.

scholarly journals The Effect of Glycerol Treatment of Voltage-Clamped Snake Muscle Fibers

1973 ◽  
Vol 61 (2) ◽  
pp. 176-184 ◽  
Author(s):  
Hiroshi Washio
Keyword(s):  
Normal Saline ◽  
Surface Membrane ◽  
Muscle Fibers ◽  
Outward Current ◽  
Tension Development ◽  
Normal Medium ◽  
Outward Currents ◽  
Delayed Rectification ◽  
Glycerol Treatment ◽  
Contractile Activation

The effect of glycerol treatment on the membrane currents and tension development was studied in voltage clamped snake muscle fibers. In muscle fibers which were exposed for 1 h to a normal saline containing 400 mM glycerol and then returned to a normal medium, graded depolarizations did not accompany contractile responses. However, when the fiber was depolarized to a certain level, an increment of outward current appeared which partially inactivated with time. The threshold for delayed rectification in glycerol-treated fibers was almost the same as that of intact fibers in spite of the absence of contractile tension. The results suggest that the delayed rectification may be attributed at least in part to the surface membrane and that the contractile activation probably does not depend simply on the inactivating outward currents through the delayed rectification channel.

Solitary Wave with Quantisation of Electron’s Orbit in a Magnetised Plasma in the Presence of Heavy Negative Ions

2020 ◽  
Vol 75 (3) ◽  
pp. 211-223 ◽  
Author(s):  
Manoj Kr. Deka ◽  
Apul N. Dev
Keyword(s):  
Magnetic Field ◽  
Solitary Wave ◽  
Electron Density ◽  
Maximum Amplitude ◽  
Negative Ions ◽  
Ion Concentration ◽  
Negative Ion ◽  
Maximum Height ◽  
Degenerate Plasma ◽  
Analytical Scheme

AbstractThe propagation characteristics of solitary wave in a degenerate plasma in the presence of Landau-quantised magnetic field and heavy negative ion are studied. The nature of solitary wave in such plasma under the influence of magnetic quantisation and the concentration of both electrons and negative ions, as well as in the presence of degenerate temperature, are studied with the help of a time-independent analytical scheme of the solution of Zakharov–Kuznetsov equation. The electron density, as well as the magnetic quantisation parameter, has an outstanding effect on the features of solitary wave proliferation in such plasma. Interestingly, for any fixed electron density, the magnetic quantisation parameter has an equal control on the maximum height and dispersive properties of the solitary wave. Toward higher temperatures and higher magnetic fields, the width of the solitary wave decreases. For a lower magnetic field, the maximum amplitude of the solitary wave decreases rapidly at higher values of degenerate temperature and negative ion concentration; however, at a lower value of degenerate temperature, the maximum amplitude increases with increasing negative ion concentration.

Delayed rectifier K+ current in rabbit atrial myocytes

1995 ◽  
Vol 269 (2) ◽  
pp. H524-H532 ◽  
Author(s):  
K. Muraki ◽  
Y. Imaizumi ◽  
M. Watanabe ◽  
Y. Habuchi ◽  
W. R. Giles
Keyword(s):  
Maximum Amplitude ◽  
Outward Current ◽  
Cell Voltage ◽  
Inward Rectification ◽  
Resting Membrane Potential ◽  
Delayed Rectifier ◽  
Wave Form ◽  
Class Iii ◽  
Atrial Myocytes ◽  
K Current

The role of delayed rectifier K+ current(s) (IK) in rabbit left atrium was examined by applying the whole cell voltage-clamp technique to isolated single myocytes. Right-triangular waveforms, which mimic the shape of atrial action potentials (APs), and selective blockers were used to compare the contribution of IK with other K+ currents to repolarization of the APs. IK measured at 34 degrees C in atrial myocytes was very small; the maximum peak amplitude of the tail current (IK,tail) at -40 mV was approximately 50 pA. The IK,tail was almost abolished in most cells (approximately 80%) by the application of 1 microM E-4031, a class III antiarrhythmic drug. The E-4031-sensitive current recorded with the triangular command wave-form showed strong inward rectification and had a maximum amplitude of approximately 30 pA at -40 mV. Total outward current elicited by triangular command pulses depended strongly on stimulation frequency. The main frequency-dependent component was a Ca(2+)-independent transient K+ current (I(t)). I(t) elicited by triangular pulses at 1 Hz was substantially reduced by 4-aminopyridine (4-AP) at potentials positive to 0 mV but was not changed significantly by 1 microM E-4031; 100 microM E-4031 reduced I(t) by approximately 30%. The shape of the APs which were recorded from a single rabbit atrial cell strongly depended on the pulse frequency. Application of 1 microM E-4031 increased action potential duration (APD) in > 50% of cells examined but had little effect on the resting membrane potential (RMP). Application of 0.1 mM BaCl2 also lengthened APD and reduced RMP by approximately 20 mV.(ABSTRACT TRUNCATED AT 250 WORDS)

Loss of mGluR-mediated hyperpolarizations and increase in mGluR depolarizations in basolateral amygdala neurons in kindling-induced epilepsy

1996 ◽  
Vol 76 (4) ◽  
pp. 2808-2812 ◽  
Author(s):  
K. H. Holmes ◽  
N. B. Keele ◽  
P. Shinnick-Gallagher
Keyword(s):  
Basolateral Amygdala ◽  
Metabotropic Glutamate Receptor ◽  
Maximum Amplitude ◽  
Outward Current ◽  
Response Relationship ◽  
Inward Current ◽  
Group I ◽  
Hyperpolarizing Response ◽  
Group Ii

1. Intracellular recordings were made from neurons of the basolateral amygdala (BLA) in in vitro slice preparations to determine long-term differences in metabotropic glutamate receptor (mGluR) agonist-induced membrane responses in control and amygdala-kindled rats. 2. (2S,3S,4S)-alpha-(carboxycyclopropyl)glycine-1 (L-CCG-I; 100 microM) typically evoked a hyperpolarization/outward current in control BLA neurons; the hyperpolarization is mediated through a group-II-like mGluR subtype of receptor and is recorded in accommodating neurons that cease firing in the presence of a long (400 ms) depolarizing current injection (0.5 nA). In amygdala-kindled slices, L-CCG-I (100 microM) hyperpolarized only 1 of 13 BLA neurons. 3. 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) (100 microM) elicited a hyperpolarization/depolarization (outward/inward current) in control neurons and evoked only a membrane depolarization (inward current) in kindled BLA neurons; this depolarization is similar to that mediated by group I mGluR activation in other neurons. 4. In control nonaccommodating neurons the concentration-response relationship for the 1S,3R-ACPD-induced inward current had a median effective concentration (EC50) of 49 microM and a maximum amplitude of 182 +/- 30 (mean +/- SE) pA. In kindled nonaccommodating neurons the EC50 of the concentration-response relationship for 1S,3R-ACPD was shifted to 29 microM and the maximum value increased to 265 +/- 15 pA, reflecting an increase in efficacy. 5. These data suggest that amygdala kindling causes lasting changes in mGluR responses in the BLA reflecting a downregulation of a group-II-like mGluR subtype mediating the hyperpolarizing response and an upregulation of a group I mGluR1 or 5 subtype. The hyperpolarizing response reduced by kindling and the increase in the group I mGluR response may reflect an alteration in the balance between inhibition and excitation and may contribute to the transition to epileptiform bursting in kindled neurons.

scholarly journals Anomalous Rectification in the Squid Giant Axon Injected with Tetraethylammonium Chloride

1965 ◽  
Vol 48 (5) ◽  
pp. 859-872 ◽  
Author(s):  
Clay M. Armstrong ◽  
Leonard Binstock
Keyword(s):  
Action Potential ◽  
Outward Current ◽  
Giant Axon ◽  
Potassium Ion ◽  
Ion Concentration ◽  
High Potassium ◽  
Tetraethylammonium Chloride ◽  
Voltage Curve ◽  
Instantaneous Current ◽  
Current Voltage Curve

The injection of tetraethylammonium chloride into the giant axon of the squid prolongs the action potential and eliminates most of the late current under voltage-clamp. Experiments on fibers in an external medium of high potassium ion concentration demonstrate that injected tetraethylammonium chloride causes rectification of the instantaneous current-voltage curve for potassium by excluding outward current. This interference with the flow of outward potassium ion current underlies the prolongation of the action potential seen in tetraethylammonium-injected fibers.

scholarly journals A conductance maximum observed in an inward-rectifier potassium channel.

1994 ◽  
Vol 104 (3) ◽  
pp. 477-486 ◽  
Author(s):  
Z Lu ◽  
R MacKinnon
Keyword(s):  
Single Channel ◽  
Outward Current ◽  
Inward Rectifier ◽  
Ion Concentration ◽  
K Channel ◽  
Single Channels ◽  
Ligand Interaction ◽  
Membrane Biology ◽  
Maximum Value ◽  
Conduction Pathway

One prediction of a multi-ion pore is that its conductance should reach a maximum and then begin to decrease as the concentration of permeant ion is raised equally on both sides of the membrane. A conductance maximum has been observed at the single-channel level in gramicidin and in a Ca(2+)-activated K+ channel at extremely high ion concentration (> 1,000 mM) (Hladky, S. B., and D. A. Haydon. 1972. Biochimica et Biophysica Acta. 274:294-312; Eisenmam, G., J. Sandblom, and E. Neher. 1977. In Metal Ligand Interaction in Organic Chemistry and Biochemistry. 1-36; Finkelstein, P., and O. S. Andersen. 1981. Journal of Membrane Biology. 59:155-171; Villarroel, A., O. Alvarez, and G. Eisenman. 1988. Biophysical Journal. 53:259a. [Abstr.]). In the present study we examine the conductance-concentration relationship in an inward-rectifier K+ channel, ROMK1. Single channels, expressed in Xenopus oocytes, were studied using inside-out patch recording in the absence of internal Mg2+ to eliminate blockade of outward current. Potassium, at equal concentrations on both sides of the membrane, was varied from 10 to 1,000 mM. As K+ was raised from 10 mM, the conductance increased steeply and reached a maximum value (39 pS) at 300 mM. The single-channel conductance then became progressively smaller as K+ was raised beyond 300 mM. At 1000 mM K+, the conductance was reduced to approximately 75% of its maximum value. The shape of the conductance-concentration curve observed in the ROMK1 channel implies that it has multiple K(+)-occupied binding sites in its conduction pathway.

scholarly journals Oscillatory membrane potential changes in cells of mesenchymal origin: the role of an intracellular calcium regulating system

1979 ◽  
Vol 81 (1) ◽  
pp. 49-61
Author(s):  
P. G. Nelson ◽  
M. P. Henkart
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Potential ◽  
Intracellular Calcium ◽  
Calcium Ion ◽  
Surface Membrane ◽  
Ion Concentration ◽  
Free Calcium ◽  
Potassium Ions ◽  
Calcium Ion Concentration

A number of mesenchymal cells (fibroblasts, macrophages and megakaryocytes) respond to a variety of stimuli with large hyperpolarizations lasting several seconds (the H.A. response). The H.A. responses can occur as repetitive trains or oscillations. These hyperpolarizations are due to an increase of the surface membrane permeability to potassium ions which is probably mediated by an increase in the cytoplasmic free calcium ion concentration. Evidence is discussed which suggests that the source of this increased calcium, is least in part, an intracellular sequestering system, probably the endoplasmic reticulum. A model capable of producing oscillatory changes in membrane potential is proposed based on such an intracellular calcium sequestering and releasing system.

Heparin Induces Synthesis and Secretion of Tissue Factor Pathway Inhibitor from Endothelial Cells In Vitro

2000 ◽  
Vol 83 (06) ◽  
pp. 937-943 ◽  
Author(s):  
Birgit Svensson ◽  
Randi Olsen ◽  
Mirella Ezban ◽  
Bjarne Østerud ◽  
Ruth Paulssen ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Surface Membrane ◽  
Molecular Size ◽  
Fold Increase ◽  
Coagulation System ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Stimulation Of

SummaryTFPI is a potent inhibitor of the extrinsic coagulation system constitutively synthesized by endothelial cells. A major portion of intravascular TFPI is stored associated with endothelial cells, and administration of unfractionated heparin (UFH) in vivo causes a prompt mobilization of TFPI into the circulation. The present study was conducted to investigate how UFH affected the synthesis, secretion and anticoagulant potency of TFPI in endothelial cells in vitro. A spontaneously transformed immortal endothelial cell line was used (ECV304). Stimulation of ECV304 cells with UFH caused a prompt dose-dependent (0-5 IU UFH/ml) release of TFPI to the medium accompanied by no change of TFPI at the surface membrane assessed by immunocytochemical methods. Northern blot analysis revealed two mRNA transcripts for TFPI with a molecular size of 1.4 kb and 4.4 kb, respectively. Stimulation of ECV304 cells for 24 hrs with various concentrations of UFH caused a dose-dependent increase of TFPI in the medium (6.2-29.6 ng/106 cells within the concentration range 0-10 IU/ml). A similar dose-dependent increase in the expression of both TFPI mRNA species was observed. Long-term incubation of ECV304 cells with 5.0 IU/ml UFH caused a 5-10 fold increase in the TFPI concentration accumulated in the medium over 48 hrs. The increased TFPI mRNA expression induced by UFH appeared already after 10 min, peaked after 2-4 hrs, remained augmented throughout the entire period of UFH exposure, and preceeded the synthesis-dependent increase in TFPI release by 2-4 hrs. The procoagulant activity of the cells was downregulated by 36 % and the contribution of TFPI to the anticoagulant potency of ECV304 cells was moderately increased after 24 hrs heparin stimulation. It is suggested that these mechanisms are of major importance for the anticoagulant function of heparins.

scholarly journals Giant smooth muscle cells of Beroë. Ultrastructure, innervation, and electrical properties.

1980 ◽  
Vol 75 (1) ◽  
pp. 79-105 ◽  
Author(s):  
M L Hernandez-Nicaise ◽  
G O Mackie ◽  
R W Meech
Keyword(s):  
Action Potentials ◽  
Single Cells ◽  
Surface Membrane ◽  
Mean Values ◽  
Nerve Net ◽  
Low Concentrations ◽  
Intracellular Stimulation ◽  
Longitudinal Muscles ◽  
Maximum Rate Of Rise ◽  
Tetraethylammonium Ions

Beroë muscle fibers are single cells which may be 20-40 micrometer in diameter in mature specimens. Longitudinal muscles may be 6 cm or more long. There is no striation pattern and the muscles were observed to contract in a tonic fashion when stretched. They are innervated by a nerve net, and external recording revealed what are probably nerve net impulses. Intracellular stimulation of the muscles themselves was found to initiate large propagating action potentials which were recorded intracellularly. The action potentials were insensitive to tetrodotoxin (10(-5) g/ml), tetraethylammonium ions (50 mM), MnCl2 (25 mM), and low concentrations of verapamil (2 X 10(-6) g/ml). Full-size action potentials were recorded in sodium- or calcium-deficient salines, but were small and graded in salines deficient in both sodium and calcium. Cable analysis yielded mean values for lambda (1.95 mm), Ri (154 omega cm), Rm (9,253 omega cm2), and tau m (13.9 ms). The conduction velocity depended primarily on fiber diameter and maximum rate of rise of the action potential and could be predicted from the theoretical analysis of Hunter et al. (1975 Prog. Biophys. Mol. Biol. 30: 99-144). The calculated membrane capacity (less than microF/cm2) indicates little infolding of the surface membrane, a conclusion which is in agreement with anatomical studies.

In vivo Ca2+ dynamics during cooling after eccentric contractions in rat skeletal muscle

2020 ◽  
Author(s):  
Ryo Takagi ◽  
Ayaka Tabuchi ◽  
Tomoyo Asamura ◽  
Seiya Hirayama ◽  
Ryo Ikegami ◽  
...  
Keyword(s):  
Muscle Fiber ◽  
Contractile Function ◽  
Fold Increase ◽  
Ion Concentration ◽  
Eccentric Contractions ◽  
Fiber Damage ◽  
Intracellular Calcium Ion ◽  
Mechanistic Basis ◽  
Calcium Ion Concentration

The effect of cooling on in vivo intracellular calcium ion concentration ([Ca2+]i) after eccentric contractions (ECs) remains to be determined. We tested the hypothesis that cryotherapy following ECs promotes an increased [Ca2+]i and induces greater muscle damage in two muscles with substantial IIb and IIx fiber populations. The thin spinotrapezius (SPINO) muscles of Wistar rats were used for in vivo [Ca2+]i imaging and tibialis anterior (TA) muscles provided greater fidelity and repeatability of contractile function measurements. SPINO [Ca2+]i was estimated using fura 2-AM and the magnitude, location and temporal profile of [Ca2+]i determined as the temperature near the muscle surface post-ECs was decreased from 30oC (control) to 20oC or 10oC. Subsequently, in the TA the effect of post-ECs cooling to 10oC on muscle contractile performance was determined at 1 and 2 days after ECs. TA muscle samples were examined by hematoxylin and eosin staining to assess damage. In SPINO reducing the muscle temperature from 30oC to 10oC post-ECs resulted in a 3.7-fold increase in the spread of high [Ca2+]i sites generated by ECs (P<0.05). These high [Ca2+]i sites demonstrated partial reversibility when rewarmed to 30oC. Dantrolene, a ryanodine receptor Ca2+ release inhibitor, reduced the presence of high [Ca2+] sites at 10oC. In the TA cooling exacerbated ECs-induced muscle strength deficits post-ECs via enhanced muscle fiber damage (P<0.05). By demonstrating that cooling post-ECs potentiates [Ca2+]i derangements, this in vivo approach supports a putative mechanistic basis for how post-exercise cryotherapy might augment muscle fiber damage and decrease subsequent exercise performance.

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