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Biomedical subjects

N Shigeto

Publications and source records attributed to N Shigeto.

At least 55 records · Page 3Linked to original sources
PubMed1980

The initial inward current in spherical clusters of chick embryonic heart cells.

The rapid inward sodium current in spherical clusters of 11-d-old embryonic chick heart cells, ranging in size between 65 and 90 micron diameter, was studied using the two-microelectrode voltage-clamp technique. Using these preparations, it was possible to resolve the activation phase of the rapid inward current for potentials negative to -25 mV at 37 degrees C. The rapid inward current exhibited a voltage and time dependence similar to that observed in other excitable tissues. It was initiated at potential steps more positive than -45 mV. The magnitude of the current reached its maximum value at a potential of approximately -20 mV. The measured reversal potential was that predicted by the Nernst equation for sodium ions. The falling phase of the current followed a single exponential time-course with a time constant of inactivation, tau h, ranging between 2.14 ms at -40 mV and 0.18 ms at -5 mV. The time constant of inactivation, tau h, determined by a single voltage-step protocol was compared to the constant, tau c, determined by a double voltage-step protocol and no significant different between the two constants of inactivation was found. Furthermore, the time constants of inactivation and reactivation at the same potential in the same preparation were similar. The results of this study demonstrate that the sodium current of heart cells recorded at 37 degrees C can be described by Hodgkin-Huxley kinetics with speeds approximately four times faster than the squid giant axon at 15 degrees C.

Action Potentials↗
PubMed1979

Adhesion between copper-plated acrylic tray resin and a polysulfide rubber impression material.

The method of copper plating on acrylic resin was developed, and the bond strength to polysulfide rubber was measured in comparison with that of the adhesive coating. The bond strength with copper plating was greater than with adhesive coating. The specimens with adhesive coating failed due to a rupture occurring at the elastomer-adhesive interface, while those with copper plating had cohesive-adhesive failure. The method of copper plating on acrylic resin improved the adhesion between the polysulfide rubber and the custom-built acrylic resin tray.

Acrylic Resins↗
PubMed1974

The effect of polarization on the action potentials of the rabbit AV nodal cells.

The resting potential of various parts of the AV nodal regions of an excised rabbit heart was changed by applying constant electrical current with a suction electrode. The membrane potential was recorded with an intracellular microelectrode and the maximum rate of rise of depolarization was computed. The action potential recorded from the AV nodal cell responded to constant current in a manner qualitatively similar to other myocardiums. The relationship between resting potential and amplitude of action potential was expressed by a straight line, while a sigmoidal relationship was observed between the resting potential and the maximum rate of rise of depolarization. Most of the initial current system in alpha region was inactivated at the control membrane potential. The maximum value of the maximum rate of rise of depolarization of alpha region was 30 V/sec which was lower than that of other parts of the nodal region.

Action Potentials↗