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Biomedical subjects

B C ABBOTT

Publications and source records attributed to B C ABBOTT.

At least 19 recordsLinked to original sources
PubMed1965

ELECTRICAL AND MECHANICAL RESPONSES IN DEEP ABDOMINAL EXTENSOR MUSCLES OF CRAYFISH AND LOBSTER.

Electrical and mechanical studies have been made of the deep abdominal extensor muscles, medial (DEAM) and lateral (DEAL), of crayfish and lobster. The medial muscle responds to direct (intracellular) and indirect stimulation with a transient membrane depolarization which exhibits the properties of a propagated non-decremental action potential but does not overshoot the zero level. The amplitude is about 30 mv in crayfish and 50 mv in lobster. It is followed by a fast all-or-none twitch whose duration at 20 degrees C is 30 to 50 msec. and whose developed tension is 500 gm/cm(2) or about half the tetanic value. Membrane potential is K(+)-dependent and immersion in high K(+) induces a brief transient tension rise as in other twitch-type muscles. The action potential and twitch are normal even if all external Na(+) is replaced with sucrose but vary with external Ca(++), the action potential increasing 8 to 10 mv for a twofold increase in Ca(++). The lateral muscle (DEAL) is much slower and responds to intracellular stimulation only with an electrotonic or a local response. Mechanical responses and relaxation speeds are slow with minimal duration of contraction of 0.5 to 2 seconds. Immersion in high K solutions induces large maintained tensions. Sarcomere length in the fast DEAM is uniform and about 2 micro at rest, but in the DEAL speed is less and sarcomere length is greater averaging about 4.5 micro but with a mixed population of fibers.

Action Potentials↗
PubMed1959

A study of inotropic mechanisms in the papillary muscle preparation.

The length-tension diagram, the force-velocity relation, the characteristics of the series elasticity, and the duration of the active state have been studied on the papillary muscle preparation of the cat heart, and on other examples of cardiac muscle. Positive inotropic changes such as the staircase phenomenon and post-extrasystolic potentiation occur without lengthening, but frequently with shortening, of the duration of the active state. They are accompanied by an increased velocity of contraction, and may be caused either by an intensification of the active state or by an alteration of the force-velocity characteristics of the contractile component. The changes in the force-velocity relation point to an adaptation of the velocity-efficiency relation in dependence on the frequency of contraction.

Animals↗