Stephen M. Baylor, M.D.

faculty photo
Emeritus Professor of Physiology
Department: Physiology

Contact information
A406 Richards Building
3700 Hamilton Walk
Philadelphia, PA 19104-6085
Office: (215) 898-5559
Fax: (215) 573-5851
B.A. (Mathematics)
Knox College, Galesburg, IL, 1965.
M.A. (Mathematics)
University of Illinois, Urbana, IL, 1966.
Stanford Medical School, Palo Alto, CA, 1971.
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Description of Research Expertise

Research Interests
excitation-contraction coupling; intracellular calcium signaling.

Key words: excitation-contraction coupling; ryanodine receptors; calcium sparks; skeletal muscle.

Description of Research
Dr. Baylor's research is focused on excitation-contraction (E-C) coupling in vertebrate skeletal muscle and the role of the calcium ion (Ca) as an intracellular messenger. The methodology relies primarily on indicator dye measurements of myoplasmic free [Ca], both in resting muscle fibers and in fibers stimulated electrically. Much of the recent work has involved testing hypotheses about calcium and E-C coupling in fast twitch fibers of frog muscle, with some work also carried out on twitch fibers in other species (e.g., fast-twitch and slow-twitch fibers of mouse, super-fast fibers of toadfish and rattlesnake).

Areas of active investigation include: use of laser-scanning confocal microscopy to measure "calcium sparks", which are brief localized increases in fluorescence from a Ca-indicator such as fluo-3 that are thought to be reflective of the transient opening of one or a few RyRs (=ryanodine receptors), the Ca release channels of the sarcoplasmic reticulum (SR); the possibility that the mechanism of activation of RyRs involves both voltage-gating and Ca-gating; the nature of the mechanism whereby SR Ca release is inactivated by a rise in myoplasmic free [Ca]; the possibility that either activation or inactivation of SR Ca release may vary with the RyR isoform composition (RyR1, RyR3, etc.); estimation of local Ca movements within the sarcomere by means of computer modeling, including estimation of the kinetics of binding of Ca to the intracellular Ca buffers troponin, parvalbumin, ATP, and the SR Ca pump.

Rotation Projects
1. Analysis of myoplasmic calcium movements during activity of vertebrate skeletal muscle fibers
2. Search for calcium sparks in mammalian twitch muscle fibers

Lab personnel:
Stephen Hollingworth, PhD - Senior Research Investigator

Description of Other Expertise

Muscle physiology; Intracellular calcium signaling;

Selected Publications

Chandler, WK., Hollingworth, S., Baylor, SM. : Simulation of calcium sparks in frog cut skeletal muscle fibers. Journal of General Physiology 121: 311-324, Apr 2003.

Baylor, SM., Hollingworth, S.: Sarcoplasmic reticulum calcium release compared in slow- twitch and fast-twitch fibres of mouse muscle. Journal of Physiology 551: 125-138, Aug 2003.

Cheung, A., Dantzig, JA., Hollingworth, S., Baylor, SM., Goldman, YE., Mitchison, TJ., Straight, AF.: A small-molecule inhibitor of skeletal muscle myosin II. Nature Cell Biology 4(1): 83-88, Jan 2002.

Baylor, SM., Hollingworth, S., Chandler, WK.: Comparison of modeled and measured calcium sparks in intact skeletal muscle fibers of the frog. Journal of General Physiology 120: 349-368, Sep 2002.

Hollingworth, S., Peet, J., Chandler, WK., Baylor, SM.: Calcium sparks in intact frog skeletal muscle fibers. Journal of General Physiology 118: 311-324, Dec 2001.

Hollingworth S., Soeller C., Baylor SM., Cannell MB.: Sarcomeric Ca2+ gradients during activation of frog skeletal muscle fibres imaged with confocal and two-photon microscopy. Journal of Physiology 526 Pt 3: 551-60, Aug 2000.

Baylor, S.M. and Hollingworth, S: Measurement and interpretation of cytoplasmic [Ca2+]signals from calcium indicator dyes. News in Physiological Sciences 15: 19-26, 2000.

Baylor SM., Hollingworth S.: Model of sarcomeric Ca2+ movements, including ATP Ca2+ binding and diffusion, during activation of frog skeletal muscle. Journal of General Physiology 112(3): 297-316, Sep 1998.

Zhao M., Hollingworth S., Baylor SM.: AM-loading of fluorescent Ca2+ indicators into intact single fibers of frog muscle. Biophysical Journal 72(6): 2736-47, Jun 1997.

Hollingworth S., Zhao M., Baylor SM.: The amplitude and time course of the myoplasmic free [Ca2+] transient in fast-twitch fibers of mouse muscle. Journal of General Physiology 108(5): 455-69, Nov 1996.

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Last updated: 05/08/2017
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