Cytoplasmic DNA-Containing Bodies and the Response of Amoebae to Dimidium Bromide

The growth of Amoeba proteus (T1P) and Amoeba discoides (T1) in the trypanocidal phenanthridlnium, dimidium bromide was examined. At concentrations of drug between 2 and 4 µg/ml, A. proteus divided twice before inhibition and death. A. discoides was able to undergo an additional cycle of division before death. At other concentrations there were no differences in their response. Heterotransfers between these strains resembled A. discoides, both dividing three times before death. Examination of clones derived from the micro-injection of small quantities of A. discoides cytoplasm into A. proteus showed that the ability to divide additionally in dimidium bromide could be transferred. Some other strains of A. proteus (DP, T4P) also resembled A. discoides in their response.

Cells of all the strains used were treated with acridine orange and observed under the fluorescence microscope for the presence of DNA- and RNA-containing cytoplasmic ‘bodies’. All strains able to undergo an additional division cycle also possessed cytoplasmic DNAcontaining bodies. The converse was not 100%, but this may be due to a quantitative difference in the number of DNA-containing bodies in the cytoplasm. It is proposed that the difference in response to dimidium bromide observed in A. proteus and A. discoides may be associated with the presence of DNA- and RNA-containing bodies in the cytoplasm of A. discoides.

The Viability of the Anucleate Cytoplasm Of Amoeba Proteus

The viability of Amoeba proteus cytoplasm was tested at 1- to 2-day intervals throughout the 14 days following enucleation. Viability was demonstrated by renucleating the anucleate cytoplasms and observing whether the resultant amoebae could resume normal activities such as moving, feeding and dividing. Four lines of A. proteus were studied, approximately 200 transfers being made on amoebae of each line. The introduction of a nucleus into anucleate cytoplasm initiated a temporary reactivation followed by a period of relative inactivity before either death by cytolysis or permanent reactivation with feeding, growth and division. Though approximately 70% of anucleate cytoplasms were still viable 6 days after enucleation, temporary reactivation disappeared about this time and the period of relative inactivity which generally followed it increased in duration from a few days to several weeks. Few amoebae which were able to divide failed to form clones. Anucleate cytoplasms of wheat-cultured amoebae remained viable for longer periods than anucleate cytoplasms of tetrahymena-fed amoebae.