Histidine trophic deficiency (His -) strain of Salmonella typhimurium can only divide a few times in medium containing a trace amount of histidine, except for a very few cells that spontaneously revert to mutations, forming microscopic colonies. After being treated by the mutagens, a large number of cells revert to mutation, synthesize histidine by themselves, and develop into visible colonies. Count the number of regressive colonies on the lowest trophic plate to determine whether the subject is mutagenic. Some chemicals need to be metabolically activated to have mutagenic effects. Adding mammalian microsomal enzymes in the test system can make up for the lack of metabolic activation system in vitro test.

Thymidine kinase, a product of the TK gene, catalyzes the production of thymidine monophosphate (TMP) from deoxythymidine (TDR) in vivo. Under normal circumstances, this reaction is not necessary for life because the majority of TMP in the body comes from deoxyuracil nucleotide (dUMP), which is a dUMP methylation reaction catalyzed by thymidylate synthase to produce TMP. However, when a thymidine analogue (TFT-trifluorothymidine) is added to the cell culture, the TFT, catalyzed by thymidine kinase, can produce trifluorothymidine, which is then incorporated into DNA, resulting in lethal mutations, and the cell cannot survive. If TK gene mutation leads to thymidine kinase deficiency, TFT cannot be phosphorylated, nor can it be incorporated into DNA, so cells can grow in medium containing TFT, that is, they show resistance to TFT. According to the number of mutant colonies, the mutation frequency was calculated to determine the mutagenicity of the tested species.TK gene mutation test can detect a variety of genetic changes, including point mutations, large deletions, recombination, chromosomal aneuploidy, and other large-scale genomic changes. The target cell lines used in the experiment mainly included mouse lymphoma cells L5178Y. The test sample is considered positive when the mutation frequency is dose-dependent, which is twice or more than that of the negative control.

The peripheral blood lymphocytes or human and mammalian somatic cell lines can be used as materials. The commonly used somatic cell lines include Chinese hamster ovary cells (CHO), Chinese hamster lung fibroblasts (V79 and CHL), and human embryonic lung diploid fibroblasts.

Chromosomal aberrations can be divided into chromosome structural aberrations and number aberrations. Chromosomal structural aberrations can be divided into fissure, deletion, short film and interchange.

After joining and not join the metabolic activation system under the condition of the cultured mammalian cells exposed to objects, subjects with middle blockers split phase (such as colchicine or colchicine) treatment, make the cell stops in the middle of split phase, then harvest cells, production, dyeing, microscope analysis of chromosome aberration distortion type, cell distortion, total structure aberration rate. In vitro experiments are often more sensitive than in vivo experiments because the subject is in direct contact with cells.

Micronuclei are chromatids or acentric segments or rings of chromosomes that remain in the cytoplasm when chromosomes regularly enter into daughter cells to form nuclei in the late stage of mitosis. After the terminal stage, it forms one or several regular subnuclei alone, which are contained in the cytoplasm of the cell. Because it is much smaller than the nucleus, it is called micronucleus.

Ames test

2

30 cm2

15 cm2

1g

Gene mutation test

2

400 cm2

200 cm2

13g

Chromosome aberration test

2

400 cm2

200 cm2

13g

Micronucleus Test

2

240 cm2

120 cm2

8 g