the inactive state of the cells, can be followed with ease by the light microscope.
Once the observation was made, the obvious question was whether this cellular process is
caused directly by the electrical factors at the fracture site. These were measured and found to be
similar to those found at the site of the regenerating salamander limb. Since the red cells exist naturally
as discrete cells circulating freely in the blood stream, they are an ideal cell population for evaluating
this hypothesis; they can be readily harvested, immediately introduced into an appropriate in vitro
situation, and exposed to the electrical factors without delay, without complicating biochemical factors
such as hormones or enzymes, or the other factors introduced by long term cell culture.
This experiment was carried out in a chamber that permitted both application of electrical
current and direct visualization by the light microscope as the currents were being administered.
Morphological changes typical of the dedifferentiation sequence were observed to take place within a
few hours at total current ranges between 300 and 700 pamp. The lucite chamber in which the cells
were suspended was 1 cm in diameter, approximating the size of the fracture hematoma, and from the
measured voltages and resistances in the animal this amount of current was calculated to be identical to
that present in vivo at the fracture site. Currents below and above this range were progressively less
efficient in producing the morphological change until all effects ceased below 1 and above 1000 pamp
for this size chamber. In the original experiments the changed cells were observed to have a markedly
increased uptake of tritiated mixed amino acids and to survive for several days in cell culture media
(normal unchanged red cells die under such circumstances).
In the simplest analysis, some component of the bone itself may be considered to have the
property of transduction inherent in its structure. It is now known that the structure of bone is that of a
complex, biphasic material with an organizational complexity extending down to the molecular level.
The basic phase is the collagen fibril, a long-chain fibrous protein produced by the bone cells
(osteocytes) and deposited in a highly organized pattern that determines the gross structure of each
bone. The second phase is a microcrystalline, inorganic mineral, hydroxyapatite, that is deposited in a
very precise fashion directly on the pre-existing collagen fibers. Both materials, in their correct
relationship at the molecular level, are necessary to produce bone with its unique mechanical
properties. By using appropriate chemical extraction treatment, either phase can be removed leaving
the other intact; that is, a "bone" of collagen alone or one of apatite alone. Each lacks the normal
characteristics of whole bone; the collagen alone being soft and flexible, and the apatite alone being
hard and very brittle, yet each looks very much like an intact whole bone. In life, the intact bone is
composed mainly of this biphasic material, which is actually non-living. The only living portion of the
bone is the population of the bone cells, the osteocytes, which constitutes approximately 10% of the
total mass.
ELECTROMAGNETISM & LIFE - 38