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PubMed1955

Mitochondrial changes induced by potassium and sodium in the duodenal absorptive cell as studied with the electron microscope.

Duodenal absorptive cells from animals fed large amounts of sodium or potassium contain many mitochondria with internal granules. Many mitochondrial granules are also present in cells which transport large amounts of cation. The hypothesis is advanced that the mitochondrial granule represents cation segregated within the mitochondrion. A mechanism is suggested for the segregation of excessive intracellular potassium, and for the transport of cations across cells.

Animals↗
PubMed1953

The effect of sodium and potassium ions on the impedance change accompanying the spike in the squid giant axon.

Decrease of the sodium concentration of the medium depresses both the spike and the associated impedance change in almost identical fashion. Elevation of the potassium level also depresses both phenomena, but affects the impedance change more than the spike; it slows the return to the initial impedance level. The effects on the threshold to brief square waves are also described. These results appear largely accounted for by the observations of Hodgkin and Huxley with the voltage clamp technique and by their recent hypothesis as to nature of the spike processes.

Animals↗
PubMed1955

Role of electrolytes and starvation in altering apparent radiosensitivity of baker's yeast.

1. Respiration and fermentation of yeast receiving 90,000 r of 250 kv. x-rays were studied under a variety of conditions. This dose will nearly completely inhibit growth or colony formation. 2. The apparent effects of irradiation are quite dependent on the K(+) and H(+) of the suspending medium. At pH 4.5 stimulatory effects were observed in KH(2)PO(2) buffer and inhibition in potassium-free (T-S-T) buffer. At pH 6.5 the situation was reversed and the effects were very small (about 10 per cent). Addition of K(+) to irradiated yeast in T-S-T buffer at pH 4.5 can completely reverse the inhibition seen. 3. Starving increases the apparent radiosensitivity of respiration and fermentation, probably by depletion of metabolite and/or electrolyte reserves. 4. Treatment with a cation exchange resin (dowex 50) results in marked inhibition of these processes in irradiated yeast, either fresh or starved. This was most effective if given after irradiation. Almost complete inhibition of anaerobic CO(2) production occurs with starvation, irradiation, and dowex treatment combined. 5. The effects of starvation and cation exchange resin treatment can be reversed, though not completely, by adding K(+) to the medium.

Electrolytes↗
PubMed1957

The effect of temperature, potassium, and sodium on the conductance change accompanying the action potential in the squid giant axon.

Conductance changes associated with the response of the squid giant axon have been studied at two temperature ranges (26-27 degrees C.; 9-10 degrees C.) and with modified concentrations of sodium and potassium in the medium. The phase of "initial after-conductance," during which the membrane resistance increases above the resting value, is smaller at the lower temperature. At both temperature ranges it is diminished by doubling K(+) in the medium and enhanced by removal of K(+). Halving the Na(+) of the medium also enhances this phase when K(+) is absent, but not otherwise. The time course of the conductance changes alters in form with changes of the external medium. These changes indicate independent changes in the complex of ionic events associated with the response. The experiments therefore confirm the reality of the phase of increased membrane resistance. The magnitude of this change appears to be considerable and requires a transient decrease in the mobility and/or concentration of ions in the membrane. The possible cause of this decrease is discussed.

Action Potentials↗
PubMed1958

Effects of potassium, sodium, and azide on the ionic movements that accompany activity in frog nerves.

Stimulation of intact or desheathed frog sciatic nerves produced an increase in the sodium content and a decrease in the potassium content of this tissue. In desheathed preparations the magnitudes of the changes in ionic contents decreased as the concentration of the potassium in the bathing solution was increased, while changing the external sodium concentration produced small effects on the ionic shifts. During tetanization, the rate of decline of the compound action potential also decreased as the external potassium concentration increased. Eliminating the activity respiration with 0.2 mM azide did not greatly modify the changes in sodium and potassium distribution that accompanied activity in either intact or desheathed nerves.

Action Potentials↗
PubMed1958

The effect of ions upon the response of smooth muscle to cooling.

The slow tonic responses of the anterior byssus retractor of Mytilus edulis to rapid cooling were investigated by simultaneously recording tension and resting potential changes after soaking the muscle in banthine, a powerful neuromuscular blocking agent. The quantitative relations between the amount of cooling and the amount of associated depolarization necessary for contraction at various concentrations of potentiating potassium can be expressed in a family of curves. The plateaus of the curves for sea water and for potassium-free sea water were beneath the depolarization value necessary for contraction, so that it is clear that no amount of cooling with sea water alone or with potassium-free sea water would ever be effective. When the muscle is treated with subthreshold amounts of potassium and rapidly cooled in various concentrations of sodium ion and calcium ion, respectively, the sodium and calcium do not affect the amount of depolarization. Acetylcholine, in subthreshold amounts, has a potentiating effect, but, unlike potassium and cooling, acts through the nervous apparatus. Mytilus muscle will respond to cooling with tonic contraction whenever a critical threshold amount of depolarization is achieved. Cooling alone cannot trigger the contraction since it cannot bring about sufficient depolarization. Cooling can result in contraction, however, if used in conjunction with some other subthreshold depolarizing agent. Cooling affects the contractile mechanism by first causing membrane breakdown and depolarization.

Acetylcholine↗
PubMed1958

Potassium-dependent sodium extrusion by cells of Porphyra perforata, a red marine alga.

Potassium-free artificial sea water causes a loss of cell potassium and a gain of cell sodium in Porphyra perforata, which is not attributable to an inhibition of respiration. On adding KCl or RbCl to such low potassium, high sodium tissues, net accumulation of potassium or rubidium takes place, accompanied by net extrusion of sodium. Rates of potassium or rubidium accumulation and sodium extrusion are proportional to the amount of KCl or RbCl added only at low concentrations. Saturation of rates is evident at KCl or RbCl concentrations above 20-30 mM, suggesting the role of an ion carrier mechanism of transport. Evidence for and against mutually dependent sodium extrusion and potassium or rubidium accumulation is discussed.

Eukaryota↗