The measurement of small ionic currents in living organisms by means of sensitive magnetometry

Lennard, Rosemary F (1984). The measurement of small ionic currents in living organisms by means of sensitive magnetometry. PhD thesis The Open University.



Recent research on developing and healing tissues suggests that small quasl-d. c Ionic currents (of magnitude 10-20/iA) may play a controlling role In the Initiation and organisation of growing tissues, but the difficulties of measuring such small currents has led to confusing results. Sensitive magnetometry provides a method of demonstrating, and, to some extent, locating such currents.

A novel SQUID magnetometer system has been built and used to Investigate the magnetic fields around the uninjured human leg, and the developing chick embryo In ovo. Analysis of the magnetic fields around the human leg reveals the presence of macroscopic current loops (of magnitude up to 12/iA) within the leg. These currents are broadly similar In all subjects, and show day-to-day reproducibility In Individuals. They change predictably with time of muscle relaxation, and revert to the original signal on muscular exertion. These currents are of significance when considering the therapeutic use of Injected current for the healing of non-union in bone.

The magnetic fields around eggs are detectable from day two of Incubation, and Increase In magnitude until day four or five, by which time there Is a magnetic field pattern with a null line over or near the centre of the egg. After day five the magnetic field Is reduced In size and of more complex pattern. The magnetic fields disappear If the egg Is cooled, and reappear on rewarmlng. Mathematical analysis suggests that the magnetic fields have a source deeper within the egg than the embryo Itself, probably the extra- embryonic membranes.

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