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Biomedical subjects

C S SPYROPOULOS

Publications and source records attributed to C S SPYROPOULOS.

16 recordsLinked to original sources
PubMed1959

Prolongation of response of node of Ranvier by metal ions.

The response of the node of Ranvier can be prolonged up to 5 to 6 seconds by addition to the medium of minute amounts of certain metal ions. This prolongation involves a change from a triangular to a rectangular configuration. The properties of the prolonged nerve-fiber responses are very similar to those of heart muscle.

Ions↗
PubMed1957

The effects of hydrostatic pressure upon the normal and narcotized nerve fiber.

The properties of the giant axon of the squid Loligo pealii were studied at different hydrostatic pressures from 14.7 to 16,000 psi. At 4000 psi the resting potential, the membrane resistance, membrane capacity, the conduction velocity, the amplitude of the action potential, and the maximal change in the membrane impedance during activity were only slightly affected. At the same pressure the duration of the falling phase of the action potential was increased by about 40 to 60 per cent and the duration of the rising phase by about 20 to 35 per cent. The duration of the membrane impedance change during activity was increased by 50 to 100 per cent at 4000 psi. At pressures even slightly above atmospheric the threshold membrane current was appreciably reduced. At about 3000 to 7000 psi the fiber fired spontaneously. At pressures considerably above 5000 psi the membrane resistance decreased to about one-half to one-third the original value. The narcotizing effect upon the nerve fiber of 3 to 7 per cent ethanol was partly or almost completely opposed by low temperatures or high pressures.

Action Potentials↗
PubMed1956

Changes in the duration of the electric response of single nerve fibers following repetitive stimulation.

Single nerve fibers were isolated from the nerve innervating the sartorius or semitendinosus muscle of the toad (Bufo marinus). Single nerve fiber responses were recorded with three arrangements of the "bridge insulator" method. During stimulation at 50 to 150 pulses per second for 20 to 140 minutes the spike duration was progressively increased. After tetanization the spike duration usually continued to increase at a more rapid rate. Within 5 to 60 minutes further prolongation stopped and within 1 to 10 hours the spike duration was normal. The duration of the response of tetanized fibers was from 2.5 to more than 10 times the spike duration of untetanized fibers. Prolongation was observed in nerve fibers isolated from nerves tetanized in vivo.

Electric Stimulation↗