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Biomedical subjects

H Koike

Publications and source records attributed to H Koike.

At least 397 records · Page 22Linked to original sources
PubMed1971

Hyperpolarization of a barnacle photoreceptor membrane following illumination.

Membrane potential changes following illumination of a photoreceptor cell in the lateral ocellus of a barnacle (Balanus eburneus) were studied by means of intracellular recording and polarization techniques. Illumination produces a depolarizing response. When the illumination is terminated, the membrane potential temporarily becomes more negative than the resting potential prior to illumination. Although the amplitude of this postillumination hyperpolarization depends upon the intensity as well as the duration of the light pulse, the time course is fairly constant. The hyperpolarization is not associated with any significant membrane conductance increase and is abolished by 10(-5)M ouabain. It diminishes when the external Na or K ions are removed. An intracellular injection of Na ions produces a hyperpolarization similar to that following illumination. It is suggested that the postillumination hyperpolarization is produced by an electrogenic Na pump which is activated by the Na influx during illumination.

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PubMed1971

Mitral stenosis.

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PubMed1970

Membrane properties of a barnacle photoreceptor examined by the voltage clamp technique.

1. Electrical properties of the membrane of photoreceptor cells in the lateral ocelli of barnacles, Balanus amphitrite and B. eburneus were investigated by intracellular recording, polarization and voltage-clamp techniques.2. The resting potential of a dark adapted cell was 36.3 +/- 6.6 mV (S.D.) and depended mainly on the external K(+) concentration.3. Current-voltage relations obtained from voltage-clamp experiments in the absence of light were non-linear and varied with time after the onset of a step change in membrane potential; the steady state was reached after about 0.5 sec.4. Illumination resulted in a membrane potential change under current clamp and in a change of membrane current (light-initiated membrane current (L.I.C.): total membrane current with illumination minus current without illumination) under voltage-clamp conditions. Amplitudes and time course of L.I.C. depended on the light intensity as well as membrane potential.5. The L.I.C.-voltage relation was non-linear and corresponded with a slope conductance increase with increasing positive membrane potential.6. The reversal potential of L.I.C. was independent of the light intensity and the time after onset of illumination; the average value obtained in normal saline was +26.9 +/- 5.0 mV.7. The membrane conductance estimated from instantaneous L.I.C.-voltage relations agreed with the chord conductance of the non-linear L.I.C.-voltage relation.8. Decreasing external Na(+) concentration decreased the inward component of L.I.C. but not the outward component.9. Decreasing external Ca(2+) concentration increased the inward as well as the outward component of L.I.C.10. The reversal potential shifted in the negative direction with decreasing external Na(+) concentration (the rate was 10-15 mV for a tenfold change in concentration) and the rate was augmented in the absence of Ca(2+) but did not exceed 21 mV.11. The change of reversal potential with changes of external Ca(2+) concentration was negligible in normal Na(+) media but was significant in the absence of Na(+) (rate as high as 20 mV).12. Alteration of the external K(+) or Cl(-) concentrations did not affect the amplitude or reversal potential of L.I.C.13. The results indicate that illumination increases the membrane permeability mainly to Na(+) ions and that the primary effect of Ca(2+) ions is suppression of the permeability increase; Ca(2+) permeability may increase slightly during illumination.

Animals↗
PubMed1969

Current-voltage relations during illumination: photoreceptor membrane of a barnacle.

In voltage clamped photoreceptor cells of the barnacle, light-induced membrane current varied nonlinearly with membrane potential and changed sign at about + 27 millivolts (reversal potential) independently of light intensity. Instantaneous current-voltage relations were linear and intersected the voltage axis at the reversal potential. Illumination increased membrane conductance that was dependent on membrane potential, light intensity, and time.

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