My research career was focused on the molecular/cellular mechanisms that underlie the steep sarcomere length dependence of contractility in cardiac muscle, which defines the Frank-Starling relationship for the heart (increased blood flow back to the heart from increased physical activity leads to increased cardiac output). In summary we found that the steep length dependence of contractility in heart muscle reflects both structural elements, such as the effects of myofilament proximity on the likelihood of force generating interactions between cardiac thin and thick filaments (myosin crossbridges), the kinds and strength of interactions between the molecular components of cardiac thin filament regulatory apparatus (tropomyosin, toponin-T, troponin-I and troponin-C) in the presence of activating myoplasmic Ca2+ concentrations, as well as the state of phosphorylation of cardiac troponin-I. We employed mechanical measurements of isolated small cardiac trabeculae, low angle X-ray diffraction measurements of myofilamenet geometry and structure and fluorescent microscopy of fluorescently labeled thin filament regulatory proteins (troponin-C) to monitor Ca2+ and crossbirdge induced changes in thin filament activation. Currently I periodically consult with my friend and colleague Dr. Michael Regnier
Post-doctoral Fellow, Center for Bioengineering, University of Washington, 1980-1982
Post-doctoral Fellow Department Physiology/Biophysics, University of Washington, 1978-1980
Ph.D Biology, University of Southern California, 1975
BS Biology, Pacific Lutheran University, 1969
Bioengineering Analysis of Physiological Systems 1. Bioengineering 304 (Fall 2005)
Bioengineering Analysis of Physiological Systems 1. Bioengineering 304 (Fall 2004)
Bioengineering Analysis of Physiological Systems I. Bioengineering 304 (Fall, 2003)
Bioengineering Analysis of Physiological Systems II. Bioengineering 305 (Winter, 2002)
Bioengineering Analysis of Physiological Systems I. Bioengineering 304 (Fall, 2002)
Vijay S. Rao, F. Steven Korte, Maria V. Razumova, Erik R. Feest, Hsiao M. Hsu, Thomas Irving, Michael Regnier, Donald A. Martyn. 2013. N-terminal phosphorylation of cardiac troponin-I reduces length dependent calcium sensitivity of contraction in cardiac muscle. J. Physiol. 591: 475-90.
Smith, L., C. Tainter, M. Regnier and D. A. Martyn. 2009. Cooperative crossbridge activation of thin filaments contributes to the Frank-Starling mechanism in cardiac muscle. Biophysical J. 96: 1-11
Gillis, T.E., D.A. Martyn, A.J. Rivera, and M. Regnier. 2007. Investigation of thin filament near-neighbor regulatory unit interactions during force development in skinned cardiac and skeletal muscle. J. Physiol. 580.2: 561-576.
Martyn, D.A., L. Smith, K.L. Kreutziger, S. Xu, L.C. Yu and M. Regnier. 2007. The effects of force inhibition by sodium vanadate on crossbridge binding, force redevelopment kinetics and Ca2+-activation in cardiac muscle. Biophys. J. 92: 1-12.
Moreno-Gonzalez, A, T.E. Gillis, A.J. Rivera, P.B. Chase, D.A. Martyn and M. Regnier. 2007. Thin filament regulation of force redevelopment in rabbit skeletal muscle fibres. J. Physiol. 579: 313-326.
Xu, S., D.A. Martyn and L.C. Yu. 2006. Effects of temperature and ionic strength on myofilament structure of cardiac muscle: disorder-order transformation of the thick filament. Biophys. J. 91: 3768-3775.
Bell, M.G., E.B. Lankford, G.E. Gonye, G.C.R. Ellis-Davies, D.A. Martyn, M. Regnier and R.J. Barsotti. 2005. Kinetics of cardiac thin-filament activation probed by fluorescence polarization of rhodamine labeled troponin C in skinned guinea pig trabeculae. Biophys. J. 90(2): 531-543.
Fuchs, F. and D.A. Martyn. 2005. Invited Review. Length-dependent activation in cardiac muscle: some remaining questions. J. Musc. Res. Cell Motil. 26: 199-212
Warner-Clemmens, E., M. Entezari, D.A. Martyn and M. Regnier. 2005. Different effects of cardiac vs. skeletal muscle regulatory proteins on in vitro measures of actin filament speed and force. J. Physiol. 566.3: 737-746.
Martyn, D.A. 2004. Invited editorial. Myosin-binding protein-C: structural and functional complexity. J. Mol. Cardiol. 37: 813-815.
Adhikari, B.B., M. Regnier, A.J. Rivera, K.L. Kreutziger and D.A. Martyn. 2004. Cardiac length dependence of force and force redevelopment kinetics with altered crossbridge cycling. Biophys. J 87: 1784-1794.
Regnier, M., H. Martin, R.J. Barsotti, D.A. Martyn and E. Clemmens. 2004. Crossbridge vs. thin filament contributions to the level and rate of force development in cardiac muscle. Biophys. J. 87: 1815-1824.
Martyn, D.A., B. Adhikari, M. Regnier, J. Gu, S. Xu and L.C. Yu. 2004. Response of equatorial X-ray reflections and stiffness to altered sarcomere length and myofilament lattice spacing in relaxed skinned cardiac muscle. Biophys. J. 86: 1-10.
Kohler, J., Y. Chen, B. Brenner, A.M. Gordon, T. Kraft, D.A. Martyn, M. Regnier, A.J. Rivera, C.K. Wang and P.B. Chase. 2003. Familial hypertrophic cardiomyopathy mutations in troponin I (K182r, G203S, K206Q) enhance filament sliding. Physiol. Genom. 14: 117-128.
Martyn, D.A., P.B. Chase, M. Regnier and A.M. Gordon. 2002. A simple model of myofilament compliance predicts activation dependent crossbridge kinetics in skinned skeletal fibers. Biophys. J. 83: 3425-3434.
Martyn, D.A. and A.M. Gordon. 2001. Influence of length on force and activation dependent changes in cTnC structure in skinned cardiac and fast skeletal muscle. Biophys. J. 80: 2798-2808.
Martyn, D.A., M. Regnier, D. Xu and A.M. Gordon. 2001. Ca2+ and crossbridge dependent changes in N– and C-terminal structure of troponin C in rat cardiac muscle. Biophys. J. 80: 360-370.
Regnier, M., P.B. Chase and D.A. Martyn. 1999. Contractile properties of rabbit psoas fibres inhibited by berylium fluoride. J. Musc. Res. Cell. Motil. 20: 425-432.
Martyn, D.A., C.J. Freitag and A.M. Gordon. 1999. Ca2+ and crossbridge induced changes in troponin C in skinned skeletal muscle fibers: effects of force inhibition. Biophys. J. 76: 1480-1493.