RADIATION EFFECT ON THE PERMEABILITY OF YEAST CELLS TO SODIUM AND POTASSIUM IONS (thesis)
The movement of potassium ions from the cell to the outside medium, where the potassium concentration is lower than that inside the cell, is often considered as a diffusion process, whereas the movement in the opposite direction is defined as active transport. If the process is pure diffusion then the amount of potassium leakage should be expected to be a linear function of the cell surface area, and if there is energy involved in the active transport then the amount of potassium uptake is expected to be a linear function of the cell volume. Haploid, diploid, tetraploid, and hexaploid cells of a related polyploid series of yeast, Saccharomyces cerevisiae, were used in this study. The cells have characteristics surface areas and volumes, which increase with ploidy. The dry weight, the ash weight, the potassium, and the sodium contents of the cells were determined. The effects of nitrogen, oxygen, and dextrose on the uptake and leakage of sodium and potassium ions were studied with and without radiation. The potassium content of the cells was proportional to the dry weight, whereas the sodium content was proportional to the cell surface area with the exception of the haploid. The potassium leakage from the cells into the distilled water medium was found to be largely due to a diffusion process. The annount and the time rate of K/sup +/ loss were larger and higher in cells of larger ploidy and with higher dose. The K/sup +/ leakage was proportional to the cell surface area in both control and irradiated cells. In the presence of dextrose, active transport took place. The ratio of the potassium uptake by the hexaploid to that by the diploid was 3: 1, the same as the ratio of their respective volumes. Oxygen also initiated the active transport process. Nitrogen did not have any obvious effect on the leakage and the uptake of potassium. The order of the radiosensitivity for potassium retentivity of cells of different ploidies does not follow the same sequence as that of lethality. Radiation up to 107 kr did not seem to impair the active transport process. In contrast to the behavior of potassium ions, loss of the sodium ions from the cells to the distilled water medium was not found to vary with dose. The outward movement of the sodium ions could not be explained as primarily due to a diffusion process. Nitrogen and dextrose did not have any obvious effect on the sodium leakage. Oxygen, however, was found to increase the rate of sodium leakage. (auth)
- Research Organization:
- California. Univ., Berkeley. Lawrence Radiation LAb.
- DOE Contract Number:
- W-7405-ENG-48
- NSA Number:
- NSA-14-008351
- OSTI ID:
- 4191861
- Report Number(s):
- UCRL-9012
- Country of Publication:
- United States
- Language:
- English
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