Accession Number : AD0654715

Title :   EFFECTS OF ULTRAVIOLET LIGHT IRRADIATION AND HEAT SHOCKS ON CELL DIVISION IN SYNCHRONIZED TETRAHYMENA,

Corporate Author : NAVAL RADIOLOGICAL DEFENSE LAB SAN FRANCISCO CALIF

Personal Author(s) : Nachtwey,D. S. ; Giese,A. C.

Report Date : 24 MAY 1967

Pagination or Media Count : 28

Abstract : The division of synchronized Tetrahymena pyriformis (strain W) irradiated with low doses of ultraviolet light is delayed if the irradiation is administered during the first 30 minutes after the end of the synchronizing treatment. After a short period of transition, division in most cells is not delayed even by relatively high doses. The delay induced by a particular low dose administered at any time up to the transition to insensitivity is essentially constant. The division of synchronized cells is delayed by heat shocks (34 plus or minus 0.1C, for 20 minutes) applied at any time up to approximately 60 minutes after the end of the synchronizing treatment. After this time, for any single cell in a sample, there is an instantaneous transition to heat-shock insensitivity. The delays in cell division induced by heat shocks increase with time from the end of the synchronizing treatment, attaining a maximum just before the transition to insensitivity. The two different transition times in the responses of synchronized cells to UV and to heat shock are interpreted as representing the completion of two different processes in the final preparation of the cells for division. The qualitative and quantitative differences between the responses to UV and to heat shock suggest that two different substances are involved, one sensitive to UV and one to heat. Some evidence is presented that suggests that the completion of the heat-sensitive process depends upon the UV-sensitive process. (Author)

Descriptors :   (*CILIATA, CELL DIVISION), (*CELL DIVISION, *ULTRAVIOLET RADIATION), HEAT TOLERANCE, RADIATION EFFECTS, RADIATION DOSAGE, SENSITIVITY, RADIOBIOLOGY

Subject Categories : Radiobiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE