Nuclear Transplantation Studies of the Action of Dimidium Bromide on Amoebae

Abstract

DIMIDIUM bromide (2 : 7-diamino-9-phenyl-10-methyl phenanthridinium bromide) is a trypanocidal phenanthridinium compound which has been shown to effect nucleic acid synthesis in various organisms; for example, flagellate protozoa, bacteria, yeasts and tissue culture cells¹. Growth of the free-living amoebae, Amoeba proteus and Amoeba discoides, is inhibited by this drug, the cells showing a characteristic response which depends on the concentration of drug used². In concentrations of dimidium bromide below 1 µg/ml., cells of both strains of amoebae divide three times before inhibition and death. In concentrations of dimidium bromide between 4 and 8 µg/ml., both strains divide only twice before death. There is a difference in the response of the two strains in concentrations of drug between 2 and 4 µg/ml.; A. proteus divides twice while A. discoides undergoes an additional cycle of division before inhibition and death. This difference is thought to be associated with the presence in the cytoplasm of our strain of A. discoides of “bodies” containing DNA and RNA^2–4. Similar results have been obtained using the 10-ethyl analogue ethidium bromide.