The effect of X-radiation on fumarase activity during different stages of cell division in Tetrahymena pyriformis GL

Abstract

1. 1. Tetrahymena pyriformis GL was grown in a two per cent solution of proteose peptone. 2. 2. Synchronous division was induced by the temperature flux method. 3. 3. The fumarase activity was tested at different stages of cell division in irradiated and non-irradiated cultures. 4. 4. There was a significant ( P < 0.05) difference in fumarase activity in all cases between the irradiated and non-irradiated determinations. 5. 5. A comparison of the enzymatic activity in the controls of each stage with the activity of the stages immediately preceding and following showed a significant ( P < 0.05) difference in all cases with the exception of the step from stage III to stage V. 6. 6. A comparison of the enzymatic activity in the experimentals of each stage with the activity of the stages immediately preceding and following showed a significant ( P < 0.05) difference in all cases. 7. 7. Ionizing radiation was found to inhibit fumarase activity. 8. 8. The highest rate of enzyme activity was found in the interphase stage of cell division. 9. 9. This acceleration of enzymatic activity is thought to be the result of an attempt of the organisms to replenish the energy needed to carry on the processes of cell division. 10. 10. The enzymatic activity was increased by the addition of phosphate ions. 11. 11. Basic and acid dyestuffs had toxic effects on the enzyme. 12. 12. An enlargement of the cells following exposure to ionizing radiation was noted.