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(Circulation Research. 2006;98:1110.)
© 2006 American Heart Association, Inc.

Editorials

When Is a Fly in the Ointment a Solution and not a Problem?

Neal D. Epstein, Julien S. Davis

From the Molecular Physiology Section, Molecular Cardiology Laboratory, National Heart, Lung, and Blood Institute, Bethesda, Md.

Correspondence to Neal D. Epstein, MD, Molecular Physiology Section, Molecular Cardiology Laboratory, NHLBI, NIH, 10 Center Drive, MSC 1760, Building 10, Room 7B-15, Bethesda, MD 20892. E-mail epsteinn@mail.nih.gov

See related article, pages 1212–1218

Key Words: stretch-activation • myosin kinetics • cardiac • regulatory light chain phosphorylation

An extract of the first 250 words of the full text is provided, because this article has no abstract.

You never know from where and when the next clue to any particular scientific problem will arise. In the case of cardiac function, it may have been in 1948 from Professor J.W.S. Pringle, who was trying to figure out how flies manage to fly upside down.¹ Having mounted a truncated fly wing apparatus on a gyroscopic base, he serendipitously noted that when inertial and damping conditions were just right, the truncated wings oscillated at more than 100 s^–1 independent of neuronal innervation (Figure, A). This, he surmised, was attributable to matching an intrinsic resonant property of insect flight muscle to the elastic and inertial properties of the wing and exoskeletal structure, producing a resonant system generating oscillatory power. He called this intrinsic property of insect flight muscle "stretch–activation" because it is a recurrent stretching in the face of persistent Ca²⁺ levels, not Ca²⁺ pulses, that activate the actomyosin interaction in these insect flight muscles. This resonant system resembles a parent pushing a child on a swing. The parent must push at the correct time; that is, the addition of energy to the system must be matched to the intrinsic resonance of the system.

View larger version (11K): [in this window] [in a new window]   A, Graph of what Pringle called "free oscillation" of the truncated wing apparatus. The work loop is counter-clockwise, so that as the muscle oscillates, tension is greater during shortening than at the same length during the stretch part of the cycle. The muscle is performing work on the apparatus during shortening. Adapted from Pringle1 with . . . [Full Text of this Article]

Related Article:

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Julian E. Stelzer, Sandy B. Dunning, and Richard L. Moss
Circ. Res. 2006 98: 1212-1218. [Abstract] [Full Text] [PDF]

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