Printed in Great Britain EFFECTS OF DMSO ON VACUOLE FORMATION, CONTRACTILE VACUOLE FUNCTION, AND NUCLEAR DIVISION IN TETRAHYMENA

Increasing concentrations of dimethyl sulphoxide (DMSO) affect vacuole formation in Tetrahymena, as measured quantitatively by the uptake of carmine particles. The rate of vacuole formation decreased to about 50 % of the control value in 5 0 % DMSO (v/v) and to zero in 7 5 %. At the latter concentration, the inhibition was expressed immediately; however, the effect of i-h exposure was reversible after removal of DMSO by washing. In vivo obser-vations revealed abnormal function of the contractile vacuole in 7 5 % DMSO, while cell motility and cell division appeared to be unaffected. Although cell division occurred there was little or no increase in cell number, as studied over a cell generation time. Feulgen preparations showed that nuclear division was inhibited and that cell division resulted in one anucleate and one nucleate daughter cell. This effect was also observed in some dividing cells at lower con-centrations of DMSO. The effect of DMSO on Tetrahymena was dependent not only on the concentration of the compound but also on the physiological state of the cells