ISSN:
1432-0886
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary N-nitroso-N-methylurea was tested for its ability to induce chromosomal aberrations in root-tip meristems of Vicia faba and in two ascites tumour strains (Ehrlich mouse ascites carcinoma and S2-sarcoma) of the mouse. In all cases the agent was found to be active (Table 1,8). The effectivity of the agent in aberration induction was strikingly different in the two tumour strains and possible reasons for that are discussed. In Vicia the radiomimetic activity of nitrosomethylurea was studied in more detail. The compound had a delayed effect (Table 2) and the aberrations induced were exclusively of the chromatid type. They were preferentially localized in the heterochromatic segments of the chromosomes and unevenly (not length proportional) distributed between the chromosomes. The distribution-ratio of aberrations between the short (5 pairs) and long chromosomes (one pair) was in favour of the short ones and dependent on concentration and duration of treatment (Table 1,2). The distribution of isolocus breaks and chromatid translocations between cells was in accordance with expectation on the basis of a Poisson-distribution (Table 3) and the effectivity of nitrosomethylurea was dependent on the temperature of the treatment solution (Table 4). The agent was almost inactive in the absence of oxygen and its activity was greatly reduced when the meristems were pretreated with the enzymeinhibitor sodium azide. Pretreatments with 2,4-dinitrophenol, KCN, hydroxylamine and chloromycetin did not affect significantly the rate of induced aberrations (Table 5). Pretreatment with the chelator EDTA sensitized to the radiomimetic effects of nitrosomethylurea (Table 6). Breaks induced by the compound stayed open for approximately 4–8 hours (Table 7). The experimental results are discussed and the tentative conclusion as to the mode of action of nitrosomethylurea is, that the aberrations become induced by a breakdown product of the agent the formation of which is dependent on the presence of oxygen and an enzyme containing heavy metal. Probably this decomposition product is not an alkylating agent.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00320565
