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Potassium Replacement

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181. EFFECTS OF POTASSIUM ON THE POTENTIAL OF HALICYSTIS Full Text available with Trip Pro

EFFECTS OF POTASSIUM ON THE POTENTIAL OF HALICYSTIS Sea water in which sodium has been replaced by potassium produces about the same degree of negativity in Halicystis and in Valonia. With increasing dilution of this sea water up to 1 / 16 the degree of negativity steadily falls off in Halicystis. This differs from the situation in Valonia where Damon finds that with increasing dilution the negativity passes through a minimum after which increasing dilution produces increasing negativity

1938 The Journal of general physiology

182. A MODEL OF THE POTASSIUM EFFECT Full Text available with Trip Pro

A MODEL OF THE POTASSIUM EFFECT The protoplasm of certain cells is able to distinguish electrically between K(+) and Na(+). This has been called the potassium effect. This is illustrated by experiments with Nitella. When 0.01 M KCl which has stood in contact with Nitella is replaced by 0.01 M NaCl the P.D. changes in a positive direction by an amount which varies between 30 and 95 mv. This ability to distinguish between K(+) and Na(+) disappears with the removal of an organic substance from (...) the cell. The amount of this substance is doubtless too small to make it possible to obtain enough for analysis. An attempt has therefore been made to find an organic compound which can produce similar effects. It is found that when M/1 KCl in contact with nitrobenzene (previously shaken with M/1 KCl) is replaced by M/1 NaCl the potential changes in a positive direction to the extent of 67 mv. which compares favorably with the values found in Nitella. This is not due to a greater mobility

1943 The Journal of general physiology

183. POTASSIUM ACCUMULATION IN THE PROXIMAL CONVOLUTED TUBULES OF THE FROG'S KIDNEY Full Text available with Trip Pro

POTASSIUM ACCUMULATION IN THE PROXIMAL CONVOLUTED TUBULES OF THE FROG'S KIDNEY 1. In a manner similar to that of the sartorius muscle, the isolated kidney of the frog can accumulate K against a gradient to upwards of three times its normal concentration. 2. The K-accumulating region is identified as the proximal tubule, which in the isolated tissue immersed over 24 hours in the cold (2-3 degrees C.) amounts to about 90 per cent of the nephron minus the glomerulus. In the fresh tissue (...) tubules is in accordance with the equations established for the sartorius muscle, and, as theoretically expected, there is no volume increase (but rather a small decrease) with the large accumulations, when the external Na concentration is maintained throughout. 5. With K accumulation in isotonic mixtures large volume changes occur as K is progressively substituted for Na. Over the range of external K concentration of 10 to 100 mM per litre the weight of the whole kidney changes to 2.5 times

1946 The Journal of general physiology

184. Effects of noradrenaline on potassium efflux, membrane potential and electrolyte levels in tissue slices prepared from guinea-pig liver Full Text available with Trip Pro

content rose.6. Traverses of the slices with micro-electrodes showed many negative-going deflexions of 30-40 mV in amplitude. The evidence suggests that these correspond to the membrane potentials of the parenchymal cells.7. Noradrenaline (1 muM) caused a reversible hyperpolarization of about 10 mV. The response became larger on replacing external chloride by isethionate or methylsulphate, but was little affected by a reduction in external potassium.8. After slices had been bathed in potassium (...) Effects of noradrenaline on potassium efflux, membrane potential and electrolyte levels in tissue slices prepared from guinea-pig liver 1. Some effects of noradrenaline on potassium efflux, electrolyte levels, membrane potential and current distribution in guinea-pig liver slices have been examined.2. The slices (thickness ca. 300 mum) were prepared from the median lobe of the liver and incubated at 38 degrees C in a mammalian Ringer fluid containing 2 mM pyruvate. After an initial recovery

1972 The Journal of physiology

185. Post-stimulus hyperpolarization and slow potassium conductance increase in Aplysia giant neurone Full Text available with Trip Pro

Post-stimulus hyperpolarization and slow potassium conductance increase in Aplysia giant neurone 1. Intracellular records from Aplysia giant (R2) cell somata showed long lasting 4-10 mV hyperpolarizations after passage of outward current through a second intracellular electrode.2. An increase in membrane slope conductance occurred simultaneously with the post-stimulus hyperpolarization (PSH).3. Both the PSH and conductance-increase varied strongly with stimulus amplitude and duration.4. Both (...) the PSH and the conductance increase occurred in Ca-free medium containing tetrodotoxin, when action-potential production was completely blocked.5. The PSH persisted in the presence of ouabain or DNP, with cooling, with removal of external K(+), and in media where all the Na(+) was replaced with Li(+), suggesting that it was not due to the activity of an electrogenic pump.6. A reversal potential for the PSH was demonstrated by application of maintained inward current following the end of an outward

1972 The Journal of physiology

186. The effect of potassium loading on sodium excretion and plasma renin activity in Addisonian man. Full Text available with Trip Pro

days in the control period and then for 3-4 days after potassium intake had been increased to 200-300 meq/day. Potassium loading induced a natriuresis. Hence, patients were either sodium replaced (six studies in four patients) or allowed to become sodium depleted (three patients). Potassium loading without replacement was associated with a decrease in weight, negative sodium balance, hyperkalemia, and a positive potassium balance. PRA rose during the experimental period. Potassium loading (...) with sodium replacement was associated with little change in weight or sodium balance. Hyperkalemia and positive potassium balance were present to the same degree as found in the studies without sodium replacement. When all PRA values are considered (both morning and evening values) there was no significant change with potassium loading (+ 1.31 ng/ml per h; range + 6.9 to -2.0). We conclude that hyperkalemia or a positive potassium balance did not suppress PRA in Addisonian man in these studies when

1975 Journal of Clinical Investigation

187. Membrane potentials in pinched-off presynaptic nerve ternimals monitored with a fluorescent probe: evidence that synaptosomes have potassium diffusion potentials. Full Text available with Trip Pro

Membrane potentials in pinched-off presynaptic nerve ternimals monitored with a fluorescent probe: evidence that synaptosomes have potassium diffusion potentials. 1. Some physiological properties of tissue fractions from rat brain homogenates have been examined. Of the three fractions studied (presynaptic nerve terminals, mitochondria and fragmented membranes), only the nerve terminals (synaptosomes) have the ability to accumulate 42K from physiological salt solutions. 2. The ability (...) . In the squid axon, the fluorescent emission of CC5 is directly proportional to membrane potential; depolarization causes an increase in fluorescence. 5. The fluorescence of synaptosomes ('synaptosome fluorescence') treated with CC5 is increased when [K]o is increased or [K]o is reduced; replacement of external Na by Li or choline has little effect on the synaptosome fluorescence. In quantitative terms, synaptosome fluorescence is proportional to log ([K]o plus 0-05[Na]o). Rb is about as effective as K

1975 The Journal of physiology

188. Effects of potassium, veratridine, and scorpion venom on calcium accumulation and transmitter release by nerve terminals in vitro. Full Text available with Trip Pro

Effects of potassium, veratridine, and scorpion venom on calcium accumulation and transmitter release by nerve terminals in vitro. 1. 45-Ca uptake by pinched-off nerve terminals (synaptosomes) of rat brain incubated in standard physiological saline (including 132 mM-Na + 5mM-K + 1-2 mM-Ca) at 30 degrees C averages about 0-5 mumole Ca per g protein per minute. This may be equivalent to a Ca influx of about 0-03 p-mole/cm-2 sec. 2. The rate of 45-Ca uptake is increased when the concentration of K (...) in the medium is increased above 15-20 mM, K replacing Na isosmotically. Maximum stimulation, a three- to six-fold increase in the rate of Ca uptake, occurs when [K]o is about 60 mM. The effect of increased [K]o is reversible. 3. The K-stimulated Ca uptake is associated primarily with the nerve terminal fraction of brain homogenates. The entering Ca is not accompanied by extracellular markers such as mannitol or inulin. Replacement of external chloride by methylsulphate or sulphate does not prevent

1975 The Journal of physiology

189. Control of the delayed outward potassium currents in bursting pace-maker neurones of the snail, Helix pomatia. Full Text available with Trip Pro

Control of the delayed outward potassium currents in bursting pace-maker neurones of the snail, Helix pomatia. The net outward current in bursting pace-maker neurones of the snail (Helix pomatia) during sustained and repeated voltage clamp pulses was studied. The properties of currents remaining in cobalt-Ringer or after TEA injection were compared with those in untreated cells. 2. With sustained voltage clamp depolarizations the net outward current first increases to a maximum at 150 msec (...) and then declines to 60% or less of its peak intensity. This depression, which is greater during repetition of short pulses (e.g. 100 msec pulses at 0-5 sec intervals), represents a true decrease in the outward flow of K (designated IK) and is not due to a decreased driving force resulting from extracellular K accumulation. The steady-state current-voltage (I-V) relationship for IK is N-shaped (Heyer & Lux, 1976). 3. A component of IK persists when Ca and Mg in the medium are replaced by Co (ICo-res

1976 The Journal of physiology

190. The effects of lithium and sodium on the potassium conductance of snail neurones. Full Text available with Trip Pro

The effects of lithium and sodium on the potassium conductance of snail neurones. 1. The iontophoretic injection of lithium into snail neurones reversibly increased the resting relative potassium permeability (PK). 2. Long exposures to snail Ringer containing 25 mM-Li and correspondingly reduced Na also caused an increase in PK. This did not occur with Ringer in which the same reduction of Na was made by replacing it with Tris. 3. Replacement of part of the Ringer Na by either Li or Tris led

1976 The Journal of physiology

191. Post-tetanic hyperpolarization, sodium-potassium-activated adenosine triphosphatase and high energy phosphate levels in garfish olfactory nerve. Full Text available with Trip Pro

Post-tetanic hyperpolarization, sodium-potassium-activated adenosine triphosphatase and high energy phosphate levels in garfish olfactory nerve. 1. While much is now known about the Na-K-ATPase and the posttetanic hyperpolarization of nervous tissue, they have yet to be studied together in the same preparation. 2. The post-tetanic hyperpolarization was studied in desheathed garfish olfactory nerve. The rate constant of decay of the post-tetanic hyperpolarization was determined by monitoring (...) . 5. The rate constants of the enzyme showed a dependence on Na+ concentration that paralleled the way in which the post-tetanic hyperpolarization rate constants varied as a function of the number of impulses. When Na+ was completely replaced by Li+, neither enzyme activity nor post-tetanic hyperpolarization could be measured. 6. The pH optimum for enzyme activity was between pH 7-0 and 7-8, while the optimal pH for post-tetanic hyperpolarization was above pH 8-0. 7. Metabolite levels

1976 The Journal of physiology

192. Temperature dependence of a sodium—potassium permeability ratio of a molluscan neurone Full Text available with Trip Pro

Temperature dependence of a sodium—potassium permeability ratio of a molluscan neurone 1. The temperature dependence of the membrane potential of a molluscan giant neurone was examined under conditions which block the electrogenic activity of the Na-K exchange pump.2. When the Na pump was blocked by ouabain or the removal of external K, the membrane potential depolarized as temperature was increased.3. This depolarization was prevented by the replacement of external Na with impermeant cations (...) , but was greater when Na was replaced with Li.4. All observed effects of ouabain were attributable to inhibition of the Na pump. The depolarization in response to ouabain at warmer temperatures was completely reversible, and the rate of both onset and reversibility of the ouabain effect was dependent upon temperature.5. Using a modified form of the constant field equation, the internal K concentration and the Na-K permeability ratio, P(Na)/P(K), were calculated from the experimental data.6. P(Na)/P(K

1970 The Journal of physiology

193. Effects of Sodium, Potassium, and Calcium Ions on Slow and Spike Potentials in Single Photoreceptor Cells Full Text available with Trip Pro

Effects of Sodium, Potassium, and Calcium Ions on Slow and Spike Potentials in Single Photoreceptor Cells The influence of changes in the ionic composition of the bathing medium on responses of the retinula cell of the honeybee drone to light was examined by means of intracellular microelectrodes. The resting potential of the cell was influenced mainly by the concentration of K. The peak of the receptor potential (the transient), which in a normal solution and with strong light approaches zero (...) membrane potential, overshot this level in a K-rich solution. An increase in the concentration of K also raised the level of the steady-state phase of the receptor potential (the plateau). The amplitude of the receptor potential was decreased and the spike potential rapidly abolished when Na was replaced by either sucrose, choline, or Tris. In a Ca-free solution the amplitude of the response and especially that of the plateau, was increased. An increase in Ca had the opposite effects. All these changes

1969 The Journal of general physiology

194. The activities and concentrations of sodium and potassium in toad oocytes Full Text available with Trip Pro

The activities and concentrations of sodium and potassium in toad oocytes 1. The activity of potassium, a(K), in the cytoplasm of oocytes from the toad, Bufo bufo, as measured by potassium-sensitive glass micro-electrodes, was 82 mM. The concentration of potassium, C(K), in oocytes from the same ovaries, as determined by flame photometric analysis, was 113 mM. The ratio a(K)/C(K) = 0.73 does not differ significantly from the measured activity coefficient of the normal Ringer bathing solution (...) that about half the sodium in the cell is sequestered in some manner, such that it is unavailable to affect a cation-sensitive micro-electrode.3. When the oocytes were bathed for 5 hr in a sodium-free, lithium-substituted, Ringer solution the a(Na)/C(Na) ratio decreased to 0.06-0.10. This drop in the a(Na)/C(Na) ratio implies that the sodium available to the cation-sensitive micro-electrode can leave the cell much faster than the sequestered sodium.

1969 The Journal of physiology

195. Oesophageal obstruction and ulceration caused by oral potassium therapy Full Text available with Trip Pro

Oesophageal obstruction and ulceration caused by oral potassium therapy A case is described of oesophageal ulceration and hold up following oral potassium therapy. The patient had recently undergone mitral valve replacement.

1970 British Heart Journal

196. Potassium: Effect on DNA Synthesis and Multiplication of Baby-Hamster Kidney Cells Full Text available with Trip Pro

Potassium: Effect on DNA Synthesis and Multiplication of Baby-Hamster Kidney Cells The relations between DNA synthesis, cell multiplication, and external potassium concentration have been investigated in cultured baby-hamster kidney cells. When the potassium concentration was raised from 8 mM to 114 mM by equimolar replacement of sodium, DNA synthesis and cell multiplication were almost completely inhibited. This inhibition was reversible even after 72 hr of incubation in medium with a high (...) concentration of potassium. There is a consistent difference between the cultured cells and polyoma virus-transformed cells in response to high-potassium medium, a higher-potassium concentration being required to inhibit multiplication of polyoma virus-transformed cells to the same extent as that of the nontransformed cells.

1972 Proceedings of the National Academy of Sciences of the United States of America

197. The time course of potassium contracture of single muscle fibres Full Text available with Trip Pro

of tension in the uninterrupted contractures.4. Addition of tetracaine or removal of calcium also causes the fibre to relax from a potassium contracture, although at a slower rate than that obtained by lowering the external potassium concentration. In these cases, however, no tension is redeveloped when the standard contracture medium is reapplied. When calcium in the contracture medium is replaced by nickel, the contracture time course is not diminished.5. The results obtained with potassium (...) The time course of potassium contracture of single muscle fibres 1. At 3 degrees C the long duration of potassium contractures and the delay in the repriming process allow one to carry out solution changes while the responses are still in progress, making it possible to study the processes that determine the contracture time course.2. The contractures can be cut short by suddenly lowering the external potassium concentration to normal values. Re-exposure to the high potassium medium causes

1972 The Journal of physiology

198. The hyperpolarization of frog skeletal muscle fibres induced by removing potassium from the bathing medium Full Text available with Trip Pro

in the different fibres.6. Hyperpolarization induced by K-free solution was reduced or abolished on cooling to ca 10 degrees C; on substitution of Tris or Li for Na; and upon inhibition of the Na pump with DNP (0.025-0.2 mM) or ouabain (0.05 mM). The latter agent was not as effective as the other conditions.7. Only small, slowly developing depolarization occurred when Na was replaced with Tris or Li.8. The various effects in K-free solutions were reversed on returning to the control conditions.9 (...) The hyperpolarization of frog skeletal muscle fibres induced by removing potassium from the bathing medium 1. The time course of changes in resting potential after removing K(0) was studied in twenty-four single fibres and in 136 fibres from small bundle (two to four fibres) preparations of frog semitendinosus muscles.2. The initial resting potentials in the control saline ranged between -88 and -98 mV. The potentials returned to nearly the initial values when control conditions were reinstated

1971 The Journal of physiology

199. Stimulation of amylase secretion from the perfused cat pancreas by potassium and other alkali metal ions Full Text available with Trip Pro

the reduction in secretory rate.6. During perfusion with excess potassium a vasodepressor material with the properties of acetylcholine was detected in the effluent from the gland.7. The reduction in secretory rate, when perfusate sodium was replaced by potassium, was equal to that obtained when sodium was replaced by sucrose.8. It is concluded that potassium stimulates amylase secretion indirectly by releasing acetylcholine from nerve terminals in the gland, and that the reduction in secretory rate is due (...) Stimulation of amylase secretion from the perfused cat pancreas by potassium and other alkali metal ions 1. In the isolated cat pancreas, stimulated maximally with secretin, increasing the perfusate potassium concentration (at the expense of sodium ions) caused a copious secretion of amylase from the gland, reduced the volume rate of secretion and caused vasoconstriction.2. Rubidium and caesium had similar effects to potassium: lithium, though depressing secretory rate, had no effect on enzyme

1971 The Journal of physiology

200. High Potassium and Low Sodium Contractures in Sheep Cardiac Muscle Full Text available with Trip Pro

High Potassium and Low Sodium Contractures in Sheep Cardiac Muscle Contractures develop in sheep atrial trabeculae if Tyrode's solution is rapidly replaced by a solution containing elevated potassium, reduced sodium, or both. Two phases of the contracture can be identified on the basis of differences in physiological behavior: a rapid and transient phase that predominates during the first few seconds of the contracture, and a slowly developed phase that is responsible for the steady level

1971 The Journal of general physiology

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