A statistical model to estimate variance in long term-low dose mutation assays: testing of the model in a human lymphoblastoid mutation assay.

Long term-low dose mutation assays offer a means to study the genetic effects of environmental mutagens at concentrations relevant to human exposure. These assays involve continuous induction of mutants, serial dilution of cultures and sampling to determine the mutant fraction as a function of time and mutagen concentration. An arithmetic model for the expected variance among identically treated cultures is presented. This model provides means to calculate a predicted variance of the mutant fractions and mutation rates in typical long term-low dose experiments. We have calculated the expected variances of the mutant fraction with this model and compared them to the observed variances among 4 independent experiments in which human lymphoblastoid cells were treated for 5, 10, 15 and 20 days with a non-toxic concentration of the mutagen 4-aminobiphenyl. Mutations at the HPRT locus were measured by determining the 6-thioguanine-resistant mutant fraction. The expected and observed variances of the mutant fractions are in close agreement. This model is adequate to predict the variance of the mutant fraction and should be useful in experimental design and objective evaluation of long term-low dose mutation assays.

[1]  E. Furth,et al.  Quantitative assay for mutation in diploid human lymphoblasts using microtiter plates. , 1981, Analytical biochemistry.

[2]  W. Thilly,et al.  Variance estimation in single-cell mutation assays: comparison to experimental observations in human lymphoblasts at 4 gene loci. , 1985, Mutation research.

[3]  W. Thilly,et al.  Ultraviolet light-induced mutation of diploid human lymphoblasts. , 1983, Mutation research.

[4]  W. Thilly,et al.  Internal standards for survival: increasing the accuracy for human cell mutation assays. , 1987, Mutation research.

[5]  Model‐Based Statistical Procedures for the Analysis of in Vitro Mutagenesis Assays , 1986 .

[6]  H. Liber,et al.  Mutation of human lymphoblasts exposed to low concentrations of chemical mutagens for long periods of time. , 1983, Mutation research.

[7]  W. Thilly,et al.  Assay for gene mutation in a human lymphoblast line, AHH-1, competent for xenobiotic metabolism. , 1984, Mutation research.

[8]  H. H. Evans,et al.  The influence of dose rate on the lethal and mutagenic effects of X-rays in proliferating L5178Y cells differing in radiation sensitivity. , 1985, International journal of radiation biology and related studies in physics, chemistry, and medicine.

[9]  J. Little,et al.  Evidence for linear response for the induction of mutations in human cells by x-ray exposures below 10 rads. , 1985, Proceedings of the National Academy of Sciences of the United States of America.

[10]  W. Thilly,et al.  An internal survival standard for Salmonella typhimurium forward mutation assays. , 1986, Mutation research.

[11]  W. Thilly,et al.  Mutation of human lymphoblasts by methylnitrosourea. , 1976, Chemico-biological interactions.