Regeneration of lost body parts is a well documented phenomenon for several species. There has recently been a resurgence of interest in the role of natural electric fields in humans and in the possibility of these fields influencing healing and regeneration. At the Children’s Hospital, Sheffield, approximately thirty patients are seen annu- ally with guillotine amputations of finger tips. They are treated ‘conservatively’, that is the wounds are cleaned and covered with a simple dressing. No suturing, skin grafting or other surgical procedures are used and no antibiotics are given. Provided the level of amputation is distal to the distal interphalangeal joint the results are highly successful with, in most cases, complete regrowth of the finger and finger nail and excellent cosmetic and functional results (Illingworth 1974). There have been many theories concerning the methods of regeneration and the factors that influence it (Singer 1952, 1954, Winter 1971). It seems that at the site of injury cells de-differentiate, a blastema is formed and re-differentiation follows in an attempt to reform the lost part. Recent work on salamanders, which have been extensively studied because of their regenerative ability, has suggested that naturally occurring electrical fields may influence that ability. By means of a vibrating probe, Borgens e: a1 (1977a) demonstrated steady currents leaving the stumps of regenerating newt limbs for 5 to 10 days after amputation: the currents were not affected by section of the main nerves of the limb. The stump of a salamander limb drives DC currents of amplitudes up to 100 FA cm-* outwards for approximately ten days prior to blastema formation (Jaffe and Nuccitelli 1977). These currents may help to initiate regeneration if artificially introduced into species which are not natural regenerators (Borgens er al 1977b) and cancellation or reversal of the current in the salamander will inhibit regeneration. We decided that it would be of interest to determine whether currents comparable to those observed in salamanders are Present in the vicinity of regenerating finger tips in children. 2. Method and results The salamander stump currents were measured with a vibrating probe (Jaffe and Nuccitelli 1974) which consists of two electrodes in a conducting fluid, one Stationary and one which oscillates. The differential voltage between these electrodes consists of components, the DC electrode off set and an alternating signal whose peak-to-peak 0~~~-0815/80/010087+3$01.00 01980 The Institute of Physics 87 88 Short Communication amplitude corresponds to the difference in potential between the two extreme positions of the moving electrode. If the amplitude of this alternating signal is E volts, the travel of the moving electrode d cm and the conductivity of the fluid in which the measure- ment is made is r~ Cl-’ cm-’ then the current density is given, in A cm-’, by A robust hand-held device based on this principle has been constructed. The moving electrode is vibrated electromagnetically at 20 Hz with a travel of approximately 0.1 cm and the probe has a voltage output of approximately 1.5 mV when measuring a current density of 100 FA cm-’ in physiologically normal saline. The probe does not touch the subjects’ finger: the test is painless and does not interfere with clinical management. Measurements were made on ten children who had finger tip amputations. They were made at 1 to 7 day intervals until two successive zero readings were obtained. The injured finger was immersed in physiologically normal saline for approximately two thirds of its length, and the probe was moved across the surface of the wound with the oscillating electrode approximately 0.1 cm from the tissue at its closest point. The electrode movement was kept perpendicular to the wound surface. The maximum reading of potential obtained was recorded and converted to current density by comparison with the reading obtained from a known calibration current density passed through the fluid immediately afterwards. Figure 1 shows the results obtained for the ten subjects. In curve C.T. there was a secondary rise in association with the develop- ment of a small nodule of new tissue on the finger tip.
Xanya Sofra Weiss
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