Phosphorus metabolism in yeast accompanying an inhibition of cell division by x-rays.

Cell division is one of the most radiosensitive cell processes known. An inhibition of division, sometimes also termed a division delay (Lea, 1947; Burns, 1956), can be observed independently of effects upon growth and survival (Spoerl et al., 1954). Though the specific location of the division inhibition is not known, this effect undoubtedly differs from injuries which have been described as cell division effects (Zirkle and Tobias, 1953), but which probably include an inhibition of growth and which result usually in cell death. Hevesy (1945) suggested that the primary effect involved in an inhibition of cell division by ionizing radiation was an interference with deoxyribonucleic acid formation. Such an interference is now a well-established radiation effect. However, Howard and Pelc (1953) described a radiation inhibition of root cell division which occurred before P32 uptake into the cell was retarded. Katchman et al. (1955) found no reduction in nucleic acid in irradiated, growing, but nondividing bacteria. Kelly (1956) reported that deoxyribonucleic acid continues to form for some time in growing ascite tumor cells in which division has been inhibited by radiation. Ducoff (1956) also found little effect upon deoxyribonucleic acid when division in Tetrahymena was inhibited by radiation. These observations indicate that some reaction(s) involved in division is more sensitive to radiation than deoxypentosenucleic acid synthesis. This report presents studies aimed at uncovering the sensitive reactions involved, and provides added evidence that nucleic acid formation need not be inhibited when division is stopped. The formation of various phosphorus-containing compounds of yeast cells is followed in irradiated, growing, but nondividing cultures and control cultures.