Skip to main content
NCBI home page
Biophysical Journal logoLink to Biophysical Journal
. 1990 Mar;57(3):663–667. doi: 10.1016/S0006-3495(90)82585-6

Magnetic field of a single muscle fiber. First measurements and a core conductor model.

J M van Egeraat 1, R N Friedman 1, J P Wikswo Jr 1
PMCID: PMC1280763  PMID: 2306511

Abstract

We present the first measurements of the magnetic field from a single muscle fiber of the frog gastrocnemius, obtained by using a toroidal pickup coil coupled to a room-temperature, low-noise amplifier. The axial currents associated with the magnetic fields of single fibers were biphasic and had peak-to-peak amplitudes ranging between 50 and 100 nA, depending primarily on the fiber radius. With an intracellular microelectrode, we measured the action potential of the same fiber, which allowed us to determine that the intracellular conductivity of the muscle fiber in the core conductor approximation was 0.20 +/- 0.09 S/m. Similarly, we found that the effective membrane capacitance was 0.030 +/- 0.011 F/m2. These results were not significantly affected by the anisotropic conductivity of the muscle bundle. We demonstrate how our magnetic technique can be used to determine the transmembrane action potential without penetrating the membrane with a microelectrode, thereby offering a reliable, stable, and atraumatic method for studying contracting muscle fibers.

Full text

PDF
663

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Adrian R. H., Chandler W. K., Hodgkin A. L. Voltage clamp experiments in striated muscle fibres. J Physiol. 1970 Jul;208(3):607–644. doi: 10.1113/jphysiol.1970.sp009139. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Adrian R. H., Peachey L. D. Reconstruction of the action potential of frog sartorius muscle. J Physiol. 1973 Nov;235(1):103–131. doi: 10.1113/jphysiol.1973.sp010380. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Barach J. P., Roth B. J., Wikswo J. P., Jr Magnetic measurements of action currents in a single nerve axon: a core-conductor model. IEEE Trans Biomed Eng. 1985 Feb;32(2):136–140. doi: 10.1109/TBME.1985.325434. [DOI] [PubMed] [Google Scholar]
  4. FALK G., FATT P. LINEAR ELECTRICAL PROPERTIES OF STRIATED MUSCLE FIBRES OBSERVED WITH INTRACELLULAR ELECTRODES. Proc R Soc Lond B Biol Sci. 1964 Apr 14;160:69–123. doi: 10.1098/rspb.1964.0030. [DOI] [PubMed] [Google Scholar]
  5. FATT P., KATZ B. An analysis of the end-plate potential recorded with an intracellular electrode. J Physiol. 1951 Nov 28;115(3):320–370. doi: 10.1113/jphysiol.1951.sp004675. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Gielen F. L., Roth B. J., Wikswo J. P., Jr Capabilities of a toroid-amplifier system for magnetic measurement of current in biological tissue. IEEE Trans Biomed Eng. 1986 Oct;33(10):910–921. doi: 10.1109/TBME.1986.325661. [DOI] [PubMed] [Google Scholar]
  7. Hodgkin A. L., Nakajima S. The effect of diameter on the electrical constants of frog skeletal muscle fibres. J Physiol. 1972 Feb;221(1):105–120. doi: 10.1113/jphysiol.1972.sp009742. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Roth B. J., Wikswo J. P., Jr The magnetic field of a single axon. A comparison of theory and experiment. Biophys J. 1985 Jul;48(1):93–109. doi: 10.1016/S0006-3495(85)83763-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Valdiosera R., Clausen C., Eisenberg R. S. Impedance of frog skeletal muscle fibers in various solutions. J Gen Physiol. 1974 Apr;63(4):460–491. doi: 10.1085/jgp.63.4.460. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Wikswo J. P., Barach J. P., Freeman J. A. Magnetic field of a nerve impulse: first measurements. Science. 1980 Apr 4;208(4439):53–55. doi: 10.1126/science.7361105. [DOI] [PubMed] [Google Scholar]
  11. Wikswo J. P., Jr, Samson P. C., Giffard R. P. A low-noise low input impedance amplifier for magnetic measurements of nerve action currents. IEEE Trans Biomed Eng. 1983 Apr;30(4):215–221. doi: 10.1109/tbme.1983.325220. [DOI] [PubMed] [Google Scholar]

Articles from Biophysical Journal are provided here courtesy of The Biophysical Society

RESOURCES