Abstract
During contractures of the turtle ventricle rapid changes in length induce sinusoidal oscillations under isotonic conditions. They are due to delayed responses to stretching and release, which can be demonstrated also under isometric conditions. Oscillations of two distinct frequencies are produced under different conditions and are distinguished as high- and low-frequency oscillations. In depolarized muscles the frequency is such that the duration of one cycle is about the same as that of a normal twitch, while in high-Ca solutions the duration can be the same as in high-K solutions or about six times lower. As reported previously, twitches are followed by weak mechanical and electrical oscillations. Their frequency agrees with the high-frequency oscillations. The same effects can also be induced by stretching and release. It is suggested that the phenomena observed are due to feedback mechanisms which originate in the contractile mechanism. The high-frequency oscillations are similar to those observed previously in other muscles, particularly insect fibrillar muscle, and are not due to changes in Ca concentration. The other mechanisms involve the membrane and possibly the intracellular Ca stores.
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Selected References
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- Bozler E. Feedback in the contractile mechanism of the frog heart. J Gen Physiol. 1972 Sep;60(3):239–247. doi: 10.1085/jgp.60.3.239. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brady A. J. Active state in cardiac muscle. Physiol Rev. 1968 Jul;48(3):570–600. doi: 10.1152/physrev.1968.48.3.570. [DOI] [PubMed] [Google Scholar]
- Brady A. J. Time and displacement dependence of cardiac contractility: problems in defining the active state and force-velocity relations. Fed Proc. 1965 Nov-Dec;24(6):1410–1420. [PubMed] [Google Scholar]
- Einwächter H. M., Haas H. G., Kern R. Membrane current and contraction in frog atrial fibres. J Physiol. 1972 Dec;227(1):141–171. doi: 10.1113/jphysiol.1972.sp010024. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., HOROWICZ P. Potassium contractures in single muscle fibres. J Physiol. 1960 Sep;153:386–403. doi: 10.1113/jphysiol.1960.sp006541. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HUXLEY A. F. Muscle structure and theories of contraction. Prog Biophys Biophys Chem. 1957;7:255–318. [PubMed] [Google Scholar]
- Kaufmann R. L., Bayer R. M., Harnasch C. Autoregulation of contractility in the myocardial cell. Displacement as a controlling parameter. Pflugers Arch. 1972;332(2):96–116. [PubMed] [Google Scholar]
- Kaufmann R. L., Lab M. J., Hennekes R., Krause H. Feedback interaction of mechanical and electrical events in the isolated mammalian ventricular myocardium (cat papillary muscle). Pflugers Arch. 1971;324(2):100–123. doi: 10.1007/BF00592656. [DOI] [PubMed] [Google Scholar]
- New W., Trautwein W. The ionic nature of slow inward current and its relation to contraction. Pflugers Arch. 1972;334(1):24–38. doi: 10.1007/BF00585998. [DOI] [PubMed] [Google Scholar]
- Pringle J. W. The contractile mechanism of insect fibrillar muscle. Prog Biophys Mol Biol. 1967;17:1–60. doi: 10.1016/0079-6107(67)90003-x. [DOI] [PubMed] [Google Scholar]
- Rüegg J. C., Steiger G. J., Schädler M. Mechanical activation of the contractile system in skeletal muscle. Pflugers Arch. 1970;319(2):139–145. doi: 10.1007/BF00592492. [DOI] [PubMed] [Google Scholar]
- Schädler M., Steiger G. J., Rüegg J. C. Mechanical activation and isometric oscillation in insect fibrillar muscle. Pflugers Arch. 1971;330(3):217–229. doi: 10.1007/BF00588613. [DOI] [PubMed] [Google Scholar]
- Steiger G. J. Stretch activation and myogenic oscillation of isolated contractile structures of heart muscle. Pflugers Arch. 1971;330(4):347–361. doi: 10.1007/BF00588586. [DOI] [PubMed] [Google Scholar]