Recovery and abscopal effects after inhibitory X-irradiation in earthworm regeneration.

Abstract

AbstractA seven step series of whole body irradiations beginning with 1,872 R and ending with 20,000 R showed that 10,000 R is not sufficient to block posterior regeneration from the fiftieth segment in the barnyard earthworm, Eisenia foetida but that 20,000 R is completely effective.With partial body irradiation at 20,000 or 30,000 R, if the five segments adjacent to the cut surface are exposed and the rest of the body shielded, there is no regeneration by the end of four weeks when controls have regenerated a mean of 34 segments and a minimum of 23 and stopped forming new ones. At the end of seven or more weeks all the partially irradiated worms had recovered and regenerated up to means of 17.3, 20.0, and even 26.3 segments.An abscopal effect was clearly evident in worms in which the first 40 segments were irradiated and the rest of the body, including the ten segments adjacent to the cut surface, shielded. All such worms regenerated without appreciable delay but markedly fewer segments than the controls. The question then arises as to why regenerating blastemas which are fully competent to regenerate a mean of 25 segments do not continue to proliferate until they have formed about 35 like the controls.