Regeneration and division of Blepharisma following X-irradiation

Abstract

1. 1. The regeneration of irradiated fragments of Blepharisma undulans var. americanus, is delayed by X-irradiation, the delay being greater the larger the dose, the effect increasing at a rate greater than linear. Only the posterior fragments were used in these experiments and the reappearance of the food vacuoles was taken as the end point of reformation of functional mouth parts. 2. 2. The delay in regeneration of X-irradiated fragments is parallel to a delay in macronuclear reorganization which always accompanies regeneration. 3. 3. Subsequent division of the regenerated fragments is also delayed similarly to delay of regeneration. 4. 4. Decreasing the oxygen tension by flushing the culture with nitrogen decreases the effectiveness of a given dose of radiations but does not alter the qualitative nature of the results. Fragments irradiated in pure oxygen were no more retarded than those irradiated in air. 5. 5. Fragments of starved Blepharisma proved to be more susceptible to X-rays than fragments of well-fed animals, as indicated by more prolonged regeneration-delay as well as division delay. Again, only a quantitative difference in susceptibility to X-rays between experiments carried out in air and in nitrogen was observed. 6. 6. The delay in regeneration produced by X-rays is greatest when the irradiation occurs three hours after cutting, indicating a period of radiation sensitivity at this time. When the fragments are irradiated four and a half hours after cutting, regeneration is delayed very much less. 7. 7. The delay of division of the regenerated fragments referred to in #6 is much the same regardless of the time after cutting when irradiation occurs. 8. 8. Regeneration of fragments cut after X-irradiation is most delayed when the animals are cut soon after irradiation; the delay decreases progressively until in four to six hours after irradiation the delay is very small and in eight to twelve hours almost nil. 9. 9. Cutting the irradiated Blepharisma was found to accelerate recovery from division-retarding effects of X-rays.