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Biomedical subjects

H Washio

Publications and source records attributed to H Washio.

At least 37 records · Page 2Linked to original sources
PubMed1974

Effect of external calcium and of temperature on contraction in snake muscle fibers.

The effect of external calcium and of temperature on the contractile responses has been studied in voltage clamped snake twitch muscle fibers. Increasing [Ca(++)](o) from 0.2 to 7.0 mM raised contractile threshold by 15-20 mV, the latter coinciding with the appearance of delayed rectification. The duration of contracture, the rates of rise and decay of tension depended on the level of depolarization and [Ca(++)](o). The minimum duration of repolarization necessary to restore the contractile response was much shorter in high [Ca(++)](o). When the bathing solution was cooled to 10 from 20 degrees C the time-course of contracture was markedly prolonged and the outward current was reduced without significant change in maximum tension. The threshold for contraction tended to be somewhat lower at the lower temperature. The contractile repriming was much slower at low temperature. However, reduction in temperature slowed the rate of recovery much less at low [Ca(++)](o) than at normal [Ca(++)](o).

Animals↗
PubMed1973

The effect of glycerol treatment of voltage-clamped snake muscle fibers.

The effect of glycerol treatment on the membrane currents and tension development was studied in voltage clamped snake muscle fibers. In muscle fibers which were exposed for 1 h to a normal saline containing 400 mM glycerol and then returned to a normal medium, graded depolarizations did not accompany contractile responses. However, when the fiber was depolarized to a certain level, an increment of outward current appeared which partially inactivated with time. The threshold for delayed rectification in glycerol-treated fibers was almost the same as that of intact fibers in spite of the absence of contractile tension. The results suggest that the delayed rectification may be attributed at least in part to the surface membrane and that the contractile activation probably does not depend simply on the inactivating outward currents through the delayed rectification channel.

Animals↗
PubMed1972

The ionic requirements for the initiation of action potentials in insect muscle fibers.

Electrical properties of locust leg muscle fibers were studied by means of intracellular electrodes. In most fibers, a depolarizing current pulse initiated a local response. A delayed decrease in membrane resistance appeared with more than about 10 mv depolarization. In some fibers a regenerative response also was found. Membrane constants were measured, applying the short cable model. The value of the space constant lambda was 1.6 mm and the calculated value of R(m) was about 1750 ohm cm(2). Action potentials could be elicited when the bathing fluid contained more than 2-5 mM Ba or Sr. Similar responses were seen with 2 mM Ca in the presence of tetraethylammonium (TEA). The overshoot of these action potentials increased with increasing [Ca(++)](o), [Sr(++)](o), or [Ba(++)](o), the increment for a 10-fold increase being about 29 mv for Ca and Sr and between 40 and 50 mv for Ba. These action potentials were inhibited by Mn ions but were not affected by tetrodotoxin or procaine. In solutions containing Ba or Sr, action potentials generated were suppressed by addition of Ca. The removal of Na ions did not change the configuration of the action potential. The results suggest that an increase in permeability to Ca, Ba, or Sr ions makes a major contribution to the initiation of action potentials in this tissue.

Action Potentials↗