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It has long been known that radiomimetic chemical agents which produce chromosome aberrations in plant and animal cells may also produce mutations.The early discovery by Kihlman and Levan (1949) that caffeine induces aberrations in plant chromosomes and the more recent report by Ostertag (1966) that caffeine breaks human chromosomes has led to further tests of the radiomimetic effect of beverages, food additives and home insecticides. Agents which break plant chromosomes may not break animal chromosomes, but the correlation is high (Kihlman 1966). The onion root tip technique provides a rapid method for making preliminary tests of suspected radiomimetic agents. MATERIALS AND METHODSThe agents to be tested were made up in concentrations which permit essentially normal growth of the onion root tips. Ten cc of the solution was poured over 5 layers of paper toweling in a petri dish and about 100 onion seeds were sown on the moist paper. When the roots were 0.5-1.0 cm long, usually in 3 days, they were fixed in alcohol-acetic acid for 24 hours and then transferred to alcohol until the aceto-carmine smears were made. The chromosome aberrations, which were scored at anaphase, consisted of acentric fragments and dicentric bridges.There was considerable variations in aberration frequency, but the analysis of 10 root tips, each with an average of more than 100 anaphases, for each test, gave reasonably consistent results. RESULTSThe fantastic increase in the use of artificial sweeteners in beverages and food products in recent years, and the controversy regarding their use, led us to test the radiomimetic effects of "Sucaryl", which contains 8 % of sodium cyclamate and 0.8 % of saccharin; and saccharin tablets which contain 1/4 grain of saccharin.At the concentrations recommended, 6 drops of sucaryl per 6 oz. cup or 1 saccharin tablet per cup, the aberration frequency did not exceed that of the controls. At relatively high concentrations both agents were radiomimetic.For comparative purposes tests of moderate concentrations of sugar and salt were included. Higher concentrations of sugar greatly retared growth of the root tips. The results are shown in Table 1.

Cycasin, methylazoxy-methanol-beta-glucoside, a carcinogenic compound that occurs naturally in cycad plants, induces chromosome aberrations in the root-tip cells of Allium cepa. Germination and growth in an aqueous solution of cycasin at a concentration of only 3 percent of that found in Cycas circinalis induced as many aberrations in chromosomes as did about 200 roentgens of gamma irradiation.

the differences iIi the incorporation of radioactive uridine into brain RNA represents an increase in RNA synthesis that is part of the molecular basis of learning. Good sense, however, compels caution, and alternative hypotheses are considered.

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