Mutation data score

Validation of the Mutatox test system has been und way for ova 3 years and several comparative studies have been published [51-54]. Two types of studies have been undolaken. Pure compound studies have been performed to establish a database of sensitivity using an accepted list of compounds wiA known genotoxic activity. These lest data were compared with the commonly used Salmonella reverse mutation assay developed by Ames [55] as well as carcinogenicity scores (Table 14.1). 

Use of spontaneous recessive lethal strains as testers The usual result of such homology tests is that all spontaneous recessive lethal mutations show homology and give negative trikaryon tests. Occasionally, two or more different spontaneous recessive lethal mutations will be found. It is possible to correct the data in the treated series by using one of each of the different spontaneous recessive lethals as a tester. New trikaryons are made between these testers and the strains carrying recessive lethal mutations in the treated series. These new trikaryons are plated and scored as described previously. 

Adjustment of data When the trikaryons utilizing the spontaneous recessive lethal mutations as testers have been scored, the results of these tests are used to distinguish recessive lethal mutations of spontaneous origin in the treated series. By subtracting the number of spontaneous recessive lethal mutations from the total recessive lethal mutations in a given treatment series, we can derive the actual frequency resulting from treatment. 

Great care should be taken in any mutation screening program to increase the objectivity of the data collection by such devices as double-blind scoring of control and treated series. Preliminary pilot studies should be run to determine the effect of various concentrations of the tested chemical on the fertility as well as the viability of the tested individual. If the effect is markedly adverse and if the experimental test procedure permits, the number of treated parents and the number of untreated mates should be adjusted so that more nearly equal numbers of progeny, and hence a more nearly uniform nutritional environment, will obtain in the treated and control series. 

Descriptions of the types and combinations of visible somatic mutations or aberrations found in stamen hairs and details of the computer-oriented scoring techniques are given. Several types of data characteristically obtained from the stamen-hair system are discussed. These include cell mutation frequencies and their dose-response curves, relative biological effectiveness, cell survival curves, mutation rates, and relationships of specific aberrant cell types to each other, to the cell number in the hair, and to their positions within the hair. 

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