Accession Number : AD0467261

Title :   ACTINOMYCIN D: BLOCKAGE OF CELL DIVISION OF SYNCHRONIZED TETRAHYMENA PYRIFORMIS,

Corporate Author : NAVAL RADIOLOGICAL DEFENSE LAB SAN FRANCISCO CA

Personal Author(s) : Nachtwey, D. Stuart ; Dickinson, William J.

Report Date : 30 JUL 1965

Pagination or Media Count : 37

Abstract : Synchronized Tetrahymena pyriformis cells were exposed to the antibiotic, actinomycin D, a supposed specific inhibitor of DNA-dependent RNA synthesis, in an attempt to gain information on the role of the synthesis of such RNA in the preparations of the cell for division. The following variables were studied: concentration of the drug, time after the end of the synchronizing treatment at which exposure started, and the duration of exposure. The drug at sufficiently high concentrations irreversibly blocks cell division if added early enough in the synchronized cell cycle. The higher is the concentration of drug, the later is the time in the cell cycle that the drug may be added and still block the first synchronized division. The time of addition of the drug that will lead to a block of cell division is related to the concentration of the drug by a saturation-type curve. This curve extrapolates to an asymptote of 47 minutes before cell separation. Pulse exposures to the drug also irreversibly block cell division if started before certain times prior to the first or second synchronized divisions and if started during a time when cells are forming food vacuoles. These data indicate that actinomycin D enters the cells via food vacuoles and interferes with some division-essential process that is not completed at least by 47 minutes before cell separation. (Author)

Descriptors :   (*PROTOZOA, GROWTH(PHYSIOLOGY)), (*ANTIBIOTICS, INHIBITION), ANTIMETABOLITES, DESOXYRIBONUCLEIIACIDS, REBONUCLEIC ACIDS, CULTURE MEDIA, CELL DIVISION, CELLS(BIOLOGY).

Distribution Statement : APPROVED FOR PUBLIC RELEASE