scholarly journals Quantitative analysis of resting membrane electrogenesis in insect (diptera) skeletal muscle. I. Intracellular K+, Na+ and Cl- activities, measured using liquid ion-exchanger and neutral ion-carrier microelectrodes

1988 ◽  
Vol 136 (1) ◽  
pp. 417-432
Author(s):  
J. Dawson ◽  
M. B. Djamgoz
Keyword(s):  
Mean Value ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Calliphora Erythrocephala ◽  
Electrophysiological Properties ◽  
Intracellular Na Activity ◽  
Body Wall Muscles ◽  
Ion Sensitive Microelectrodes ◽  
The Mean ◽  
Intracellular K Activity

Electrophysiological properties of skeletal body-wall muscles of prepupal Calliphora erythrocephala were investigated using double-barrelled intracellular ion-sensitive microelectrodes. The most realistic estimate of the intracellular K+ activity, obtained using K+-sensitive microelectrodes based on a neutral carrier, was 115 mmoll-1. The K+ equilibrium potential was consistently more negative than the prevailing resting potential, the average difference being −15 mV. The intracellular Na+ activity and the Na+ equilibrium potential were 7 mmoll-1 and +46 mV on average, respectively. The mean value of the intracellular Cl- activity was 40 mmoll-1, and this was apparently higher than that required for passive distribution of Cl-. However, when reversibly exposed to a Ringer containing no Cl-, cells could rapidly exchange most of their intracellular Cl-, although the resting membrane potentials were only transiently affected. It is concluded that an anionic interferent exists inside muscles, that this artefactually elevates the measured intracellular Cl- activities, and that Cl- makes no contribution to resting membrane electrogenesis.

scholarly journals Ion Activities and Electrochemical Gradients in the Mealworm Rectal Complex

1991 ◽  
Vol 155 (1) ◽  
pp. 375-402 ◽  
Author(s):  
M. J. O'DONNELL ◽  
J. MACHIN
Keyword(s):  
Active Transport ◽  
Mean Value ◽  
Ph Values ◽  
Tubule Lumen ◽  
Perinephric Space ◽  
Ion Sensitive Microelectrodes ◽  
Ion Activities ◽  
The Mean ◽  
Equilibrium Activity ◽  
Electrochemical Equilibrium

Ion activities and potential differences in cellular and extracellular compartments of the rectal complex of Tenebrio molitor L. larvae have been recorded simultaneously using double-barrelled ion-sensitive microelectrodes. On average, the tubule lumen (TL) was 44mV positive to the haemolymph. Values of aK in the posterior rectal complex exceeding 2700 mmol l−1 were measured, sufficient to account for much of the osmolality of 6.8 osmol kg−1 driving uptake of water from the rectal lumen. The mean value of 797 mmol l−1 exceeded the Nernst equilibrium activity more than 75-fold, indicating active transport of K+. Intracellular potassium activities in the tubules (153 mmol l−1) were high relative to the values in other insect cells, but moderate relative to TL values. Tubule lumen Na+ activities as high as 400 mmol l−1 and pH values of 6.8 were well above the equilibrium values of 11 mmol l−1 and 7.9, respectively, indicating active transport of these cations as well. The ease and frequency of impaling a perinephric space (PNS) surrounding the tubules established it as a functional compartment. On average, the PNS was 22 mV negative to the haemolymph. Potassium activities in the PNS were close to electrochemical equilibrium with the haemolymph, whereas mean aNa and pH were reduced fivefold and 0.5 units, respectively, below the corresponding Nernst equilibrium values. The results suggest that cations move from haemolymph to PNS, and that the PNS is the immediate source for cation transport into the tubule lumen. Cl− was close to electrochemical equilibrium with the haemolymph in both compartments, and presumably enters the tubule lumen as a passive consequence of positive potential differences (PDs) in the tubule lumen.

Measurements of the Intracellular Potassium Activity of Retzius Cells in the Leech Central Nervous System

1981 ◽  
Vol 91 (1) ◽  
pp. 87-101
Author(s):  
JOACHIM W. DEITMER ◽  
WOLF R. SCHLUE
Keyword(s):  
Cell Membrane ◽  
External Solution ◽  
Equilibrium Potential ◽  
The Mean ◽  
K Concentration ◽  
Retzius Cells ◽  
Intracellular K Activity ◽  
K Permeability ◽  
K Activity ◽  
External K

The intracellular K activity of leech Retzius cells was measured using double-barrelled, liquid ion exchanger, microelectrodes. At the normal external K+ concentration of 4 mm (equivalent to 3 mm-K activity, assuming an activity coefficient of 0.75) the mean K activity was 101.3 ± 7.6 mm (S.D., n = 14) in the cell bodies, and 4.35 ± 0.4 mV (n = 27) in the extracellular spaces surrounding them, indicating a K+ equilibrium potential of - 80 mV. The mean membrane potential was - 43.6 + 4.9 mV (n = 14). In a K-free external solution, or in the presence of 5 × 10−4m-ouabain, the intracellular K activity decreased by up to 14 mm min−1. This indicates an efflux of K+ ions across the cell membrane of approximately 2 × 10−10 mol cm−2s, and an apparent K+ permeability coefficient of 8 × 10−8 cms−1. The cell membrane depolarized upon removal of K+ and upon addition of ouabain, and transiently hyperpolarized beyond its initial level on return to the normal external K+ concentration. The recovery from this hyperpolarization paralleled the increase of the intracellular K activity following the re-addition of K+. Our results suggest that, despite the high K+ permeability of the Retzius cell membrane, the intracellular K activity is maintained at a high level by an electrogenic pump.

Effect of sugars and amino acids on amphibian intestinal Cl- transport and intracellular Na+, K+, and Cl- activity

1986 ◽  
Vol 250 (1) ◽  
pp. G109-G117
Author(s):  
J. F. White ◽  
K. Burnup ◽  
D. Ellingsen
Keyword(s):  
Cellular Level ◽  
Equilibrium Potential ◽  
Cl Transport ◽  
Luminal Membrane ◽  
Intracellular Na Activity ◽  
The Difference ◽  
Effect Of Glucose ◽  
Intracellular K Activity ◽  
Intestinal Ion Transport ◽  
K Activity

The effect of glucose, galactose, and valine on intestinal Cl- transport and intracellular Cl-, Na+, and K+ activity was investigated in isolated segments of Amphiuma small intestine. By use of double-barreled Cl- -specific microelectrodes, it was observed that galactose and valine reduced the luminal membrane potential (psi m) and eliminated the difference between the Cl- equilibrium potential (ECl) and psi m, i.e., the Cl- accumulation potential (ECl-psi m) approached zero. Simultaneously, Cl- absorption (JnetCl) was reduced in short-circuited tissues and Na+ absorption was enhanced. In contrast, after exposure to glucose, psi m and ECl-psi m declined only transiently and JnetCl was unaltered. In tissues pretreated with galactose to reduce Cl- transport, addition of glucose to the serosal medium restored Cl- accumulation across the luminal membrane and the Cl- absorptive current. Glucose, galactose, and valine each reduced intracellular K+ activity significantly. Galactose and valine each increased [corrected] intracellular Na activity (aiNa) markedly, whereas glucose increased aiNa only slightly. In conclusion, intestinal ion transport can be limited by the availability of metabolic substrate. The nonmetabolized solutes galactose and valine inhibited Cl- uptake and net Cl- absorption while stimulating net Na absorption, as though net Na+ absorption has priority over Cl- transport at the cellular level. Cl- transport is reduced at both mucosal and serosal membranes. At the luminal membrane electrogenic Cl- uptake is slowed or a backleak of Cl- is enhanced; at the serosal membrane Cl- exchange with Na+ (and HCO3-) driven by the Na+ gradient is reduced. The availability of metabolizable glucose to the cell prevents the reduction in net Cl- absorption.

Effects of Ca2+/Mg2+ removal on aiNa, aiK, and tension in cardiac Purkinje fibers

1986 ◽  
Vol 251 (6) ◽  
pp. C920-C927 ◽  
Author(s):  
R. A. Chapman ◽  
H. A. Fozzard ◽  
I. R. Friedlander ◽  
C. T. January
Keyword(s):  
Divalent Cations ◽  
Calcium Paradox ◽  
Purkinje Fibers ◽  
Intracellular Na Activity ◽  
Cardiac Purkinje Fibers ◽  
Channel Blocking ◽  
Ionic Changes ◽  
Ion Sensitive Microelectrodes ◽  
Intracellular K Activity ◽  
K Activity

Sheep cardiac Purkinje fibers were exposed to solutions free of divalent cations for hour-long periods, while intracellular Na+ and K+ activities were measured using ion-sensitive microelectrodes. Intracellular Na+ activity (aiNa) increased to 50.1 +/- 8.1 mM, and intracellular K+ activity (aiK) decreased to 76.7 +/- 3.5 mM. These ionic changes could be blocked by the presence of Mg2+ or the Ca2+ channel blocking agents D 600 and nifedipine. The rise in aiNa and the fall in aiK was accentuated by the inhibition of the Na+-K+ pump with acetylstrophanthidin or by removal of extracellular K+. These results demonstrate that in cardiac Purkinje fibers removal of divalent cations produces intracellular loading of Na+ by Na+ entry through the Ca2+ channel. On reexposure to Ca2+-containing solutions, the cells become loaded with Ca2+, and the fibers exhibit large contractures. These observations implicate Na+-Ca2+ exchange in the entry of Ca2+ into these cells during Ca2+ repletion and in the etiology of the calcium paradox.

Na+ absorption in Aplysia intestine: Na+ fluxes and intracellular Na+ and K+ activities

1983 ◽  
Vol 244 (3) ◽  
pp. R412-R417 ◽  
Author(s):  
G. A. Gerencser
Keyword(s):  
Ion Exchanger ◽  
Equilibrium Potential ◽  
Sodium Absorption ◽  
Bathing Solution ◽  
Mucosal Membrane ◽  
Intracellular Na Activity ◽  
Flux Measurements ◽  
Intracellular K Activity ◽  
Liquid Ion Exchanger ◽  
Electrochemical Equilibrium

Microelectrodes were used to measure the potential difference (psi m) across the mucosal membrane of epithelial cells lining the villi of isolated Aplysia californica intestine. In substrate-free NaCl seawater medium psi m was -55.1 +/- 1.2 mV. The cell interior was negative relative to the mucosal bathing solution. Intracellular K+ activity, determined in the absorptive cells with single-barreled liquid ion-exchanger microelectrodes, was 383 +/- 15 mM. Since the calculated K+ equilibrium potential exceeds the membrane potential, K+ is accumulated by the intestinal absorptive cell. Intracellular Na+ activity (aiNa) was also determined in the intestinal cells of Aplysia with single-barreled liquid ion-exchanger microelectrodes and was 17.2 +/- 2.5 mM. aiNa was much less than that predicted by the electrochemical equilibrium value for Na+ across the mucosal membrane. From these data the steady-state transapical Na+ and K+ electrochemical potential differences were calculated. Serosal ouabain abolished net sodium absorption as determined by flux measurements. These results are consistent with the operation of a basolateral Na+ - K+ pump.

Multiple potassium conductances and their functions in neurons from cat sensorimotor cortex in vitro

1988 ◽  
Vol 59 (2) ◽  
pp. 424-449 ◽  
Author(s):  
P. C. Schwindt ◽  
W. J. Spain ◽  
R. C. Foehring ◽  
C. E. Stafstrom ◽  
M. C. Chubb ◽  
...  
Keyword(s):  
Voltage Clamp ◽  
Sensorimotor Cortex ◽  
Divalent Cations ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Delayed Rectifier ◽  
Outward Currents ◽  
Potassium Conductances ◽  
The Mean

1. Potassium conductances were studied in large layer V neurons using an in vitro slice preparation of cat sensorimotor cortex. The kinetics and pharmacological sensitivity of K+ currents were studied directly using single microelectrode voltage clamp and indirectly by evoking single or multiple spikes and recording the spike repolarization and subsequent afterhyperpolarizations (AHPs). 2. A fast-decaying afterhyperpolarization (fAHP) and a subsequent medium-duration afterhyperpolarization (mAHP) followed a single spike. The amplitude and duration of the mAHP increased when multiple spikes were evoked at a fast rate (e.g., 100 Hz), and a slower afterhyperpolarization (sAHP) appeared only after sustained repetitive firing. 3. All AHPs were reduced by membrane potential hyperpolarization and raised extracellular K+ concentration, suggesting they were caused by an increased K+ conductance. Only the mAHP and sAHP reversed at the estimated value of potassium equilibrium potential (-100 mV), whereas the mean reversal potential of the fAHP was nearly identical to the mean value of resting potential (-71 mV). 4. Mechanisms underlying spike repolarization, the fAHP, and the mAHP were investigated. Two rapidly activating outward currents, a fast-inactivating current and a slowly inactivating delayed rectifier, were detected by voltage clamp. Both currents were reduced rapidly by tetraethylammonium (TEA). The fast transient current was reduced slowly after divalent cations were substituted for Ca2+ (through a mechanism unrelated to blockade of Ca2+ channels), whereas the delayed rectifier was unaffected. 5. Spike duration was increased and the fAHP was abolished only by blocking agents that reduced the fast outward currents. Effects of extracellular and intracellular TEA were similar. Effects of TEA and Ca2+-free perfusate were additive and resembled the effects of intracellular Cs+. The addition of apamin, d-tubocurare, or Cd2+ was ineffective. We conclude that the two fast outward currents reflect pharmacologically and kinetically separate K+ conductances that are primarily responsible for spike repolarization and the fAHP. 6. Voltage-clamp studies revealed two additional outward currents, which were persistent and Ca2+-mediated. Each current activated and deactivated slowly, but the kinetics of one component were approximately 10 times slower than the other. The decay of these currents gave rise to AHPs resembling the mAHP and the early sAHP. 7. Neither the mAHP nor the sAHP was reduced by TEA. The mAHP was reduced when divalent cations were substituted for Ca2+ or when Cd2+, apamin, or d-tubocurare were added.(ABSTRACT TRUNCATED AT 400 WORDS)

Relative contributions of passive equilibrium and active transport to the distribution of chloride in mammalian cortical neurons

1988 ◽  
Vol 60 (1) ◽  
pp. 105-124 ◽  
Author(s):  
S. M. Thompson ◽  
R. A. Deisz ◽  
D. A. Prince
Keyword(s):  
Time Constant ◽  
Cortical Neurons ◽  
Time Course ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Gamma Aminobutyric Acid ◽  
The Mean ◽  
Mean Time

1. Active and passive factors affecting the chloride gradient of cortical neurons were assessed using intracellular recordings from neurons in slices of cingulate cortex maintained in vitro. The chloride equilibrium potential (ECl-) was estimated indirectly from the reversal potentials of responses to perisomatic gamma-aminobutyric acid (GABA) application and the Cl(-)-dependent inhibitory postsynaptic potential (IPSP). Under control conditions the mean resting potential (Vm; -69.7 mV) was not significantly different than the mean IPSP reversal potential (EIPSP; -70.1 mV). 2. Increasing the external potassium concentration ([K+]o) from 1 to 10 mM shifted the mean EIPSP from -80.4 to -61.8 mV. The mean EIPSP was approximately equal to the mean Vm at all [K+]oS. The conditions of Donnan equilibrium are not met in [K+]o less than 10 mM. 3. Polarization of Vm up to 20 mV away from EIPSP for 4 min with maintained current injection had no significant effect on EIPSP. 4. The GABA reversal potential was maintained 37-52 mV less negative than Vm after equilibration in saline in which the external chloride concentration had been reduced from 133 to 5 mM by substitution with isethionate. Vm and input resistance were not significantly different from control values in cells recorded under these conditions. 5. We conclude that Cl- is not passively distributed in cortical neurons, perhaps due to a low resting Cl- permeability. 6. Impalement with electrodes containing 2 M KCl resulted in a rapid 10 mV depolarizing shift in EIPSP that then remained relatively constant. Intracellular iontophoresis of Cl- resulted in a further depolarizing shift of EIPSP of 5-10 mV that returned to control in less than 1 min. The time course of recovery of IPSP amplitude could be fit with a single exponential having a mean time constant of 6.9 +/- 1.5 s and was independent of the amount of Cl- injected or stimulation frequency. 7. Reductions in temperature from 37 to 32 degrees C significantly increased the mean time constant of IPSP recovery from Cl- injection to 11.1 +/- 3.3 s, corresponding to Q10 = 2.6.(ABSTRACT TRUNCATED AT 400 WORDS)

Long-period modulated superstructures in Pd-12.5 at.%Ce and Pd-15 at.%Ce alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 164-165
Author(s):  
Noriyuki Kuwano ◽  
Masaru Itakura ◽  
Kensuke Oki
Keyword(s):  
Electron Microscopy ◽  
Mean Value ◽  
Heavy Elements ◽  
Arc Furnace ◽  
X Ray ◽  
Long Period ◽  
Ultra High Purity ◽  
Heat Treated ◽  
Atomic Scattering ◽  
The Mean

Pd-Ce alloys exhibit various anomalies in physical properties due to mixed valences of Ce, and the anomalies are thought to be strongly related with the crystal structures. Since Pd and Ce are both heavy elements, relative magnitudes of (fcc-fpd) are so small compared with <f> that superlattice reflections, even if any, sometimes cannot be detected in conventional x-ray powder patterns, where fee and fpd are atomic scattering factors of Ce and Pd, and <f> the mean value in the crystal. However, superlattices in Pd-Ce alloys can be analyzed by electron microscopy, thanks to the high detectability of electron diffraction. In this work, we investigated modulated superstructures in alloys with 12.5 and 15.0 at.%Ce.Ingots of Pd-Ce alloys were prepared in an arc furnace under atmosphere of ultra high purity argon. The disc specimens cut out from the ingots were heat-treated in vacuum and electrothinned to electron transparency by a jet method.

Partition Coefficient Ratios and Tumour Perfusion Studied with 85mKr and 133Xe

1987 ◽  
Vol 26 (06) ◽  
pp. 253-257
Author(s):  
M. Mäntylä ◽  
J. Perkkiö ◽  
J. Heikkonen
Keyword(s):  
Partition Coefficient ◽  
Partition Coefficients ◽  
Regional Blood Flow ◽  
Blood Perfusion ◽  
Compartmental Analysis ◽  
Malignant Tumour ◽  
Mean Value ◽  
Perfusion Rate ◽  
Biological Variables ◽  
The Mean

The relative partition coefficients of krypton and xenon, and the regional blood flow in 27 superficial malignant tumour nodules in 22 patients with diagnosed tumours were measured using the 85mKr- and 133Xe-clearance method. In order to minimize the effect of biological variables on the measurements the radionuclides were injected simultaneously into the tumour. The distribution of the radiotracers was assumed to be in equilibrium at the beginning of the experiment. The blood perfusion was calculated by fitting a two-exponential function to the measuring points. The mean value of the perfusion rate calculated from the xenon results was 13 ± 10 ml/(100 g-min) [range 3 to 38 ml/(100 g-min)] and from the krypton results 19 ± 11 ml/(100 g-min) [range 5 to 45 ml/(100 g-min)]. These values were obtained, if the partition coefficients are equal to one. The equations obtained by using compartmental analysis were used for the calculation of the relative partition coefficient of krypton and xenon. The partition coefficient of krypton was found to be slightly smaller than that of xenon, which may be due to its smaller molecular weight.

Detection of Soluble Fibrin Monomer Complexes in Blood by Means of Protamine Sulphate Test

1968 ◽  
Vol 20 (01/02) ◽  
pp. 044-049 ◽  
Author(s):  
B Lipiński ◽  
K Worowski
Keyword(s):  
Human Subjects ◽  
Coronary Thrombosis ◽  
Mean Value ◽  
Healthy Human ◽  
Protamine Sulphate ◽  
Soluble Fibrin ◽  
Fibrin Monomer ◽  
Dog Plasma ◽  
The Mean ◽  
Precipitable Protein

SummaryIn the present paper described is a simple test for detecting soluble fibrin monomer complexes (SFMC) in blood. The test consists in mixing 1% protamine sulphate with diluted oxalated plasma or serum and reading the optical density at 6190 Å. In experiments with dog plasma, enriched with soluble fibrin complexes, it was shown that OD read in PS test is proportional to the amount of fibrin recovered from the precipitate. It was found that SFMC level in plasma increases in rabbits infused intravenously with thrombin and decreases after injection of plasmin with streptokinase. In both cases PS precipitable protein in serum is elevated indicating enhanced fibrinolysis. In healthy human subjects the mean value of OD readings in plasma and sera were found to be 0.30 and 0.11, while in patients with coronary thrombosis they are 0.64 and 0.05 respectively. The origin of SFMC in circulation under physiological and pathological conditions is discussed.

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