Marvin S. Legator

A Host-Mediated Microbial Assay for the Detection of Mutagenic Compounds:

Summary A procedure was established whereby a microbial indicator was incorporated in an animal system to identify and characterize mutagenic agents. The organisms, histidine auxotrophs of Salmonella typhimurium, were injected into mice intraperitoneally, and the test compound was administered intramuscularly. Mutagenesis, indicated by an increase in the incidence of prototrophs in the population, was induced by dimethylnitrosamine, N-methyl-N′-nitro-N-nitrosoguanidine, and streptozotocin. Such a system appears capable of detecting microbial mutagenic activity in compounds which remain or become physiologically active after administration.

Cytogenetic studies in rats of cyclohexylamine, a metabolite of cyclamate.

Cyclohexylamine, the major known metabolite of cyclamate, was tested in vivo for possible cytogenetic effects. In rats injected with this metabolite, there was a direct relation between dose concentration and percentage of spermatogonial and bone marrow cells showing chromosomal breaks. Single chromatid breaks predominated with infrequent exchange figures.

Cytogenetic effects of DDT and derivatives of DDT in a cultured mammalian cell line.

Cytogenetic effects of p,p′-DDT, o,p′-DDT, p,p′-DDD, o,p′-DDD, p,p′-DDE, o,p′-DDE and p,p′-DDA were investigated in a mammalian cell line (rat kangaroo). In this cell line, p,p′-DDA was toxic at 200 μg/ml, and the other compounds caused toxic effects at concentrations of 20–50 μg/ml. Mitotic inhibition was moderate in cultures treated with p,p′- or o,p′-DDT and slight in those treated with p,p′- and o,p′-DDD or DDE; none was observed with p,pt-DDA. The p,p′-isomers of DDT, DDD and DDE produced a 2-fold increase in chromosome abnormalities as compared with their corresponding o,p′-isomers. At a concentration of 10 μg/ml, the p,p′-isomers of DDT, DDD and DDE caused chromosome damage in 22.4, 15.5 and 13.7% of the cells, respectively. Of these cells, approximately 12% of the chromosome damage caused by p,p′-DDT and p,p′-DDE was exchange figures; only 1.2% of the abnormalities caused by p,p′-DDD was exchange figures. The o,p′-isomers and control cells exhibited no exchange figures.

MUTAGENIC EFFECTS OF CAPTAN

Captan (N-trichloromethylthio-4-cyclohexene1,2-dicarboximide) has proved fungicidal against a wide variety of plant and animal pathogens.’ This fungicide and its related compounds are widely used as agricultural sprays, seed treatments, and as protectants in paints, plastics, leather, and fabrics. A low toxicity has been reported in laboratory and farm animals3 Although Captan has been in wide use for over a decade, comparatively little is known about the genetic effect of this compound. The present study was undertaken to determine possible mutagenic effects of Captan. The mutagenic activity was evaluated in bacteria, in a heteroploid human embryonic lung cell line, and in a cell line derived from the kidney of the rat-kangaroo (Protorus tridactylis) .

Cycasin: Detection of Associated Mutagenic Activity in vivo

Cycasin and its lagycone, methylazoxymethanol, increase the mutant frequency of Salmonella typhimurium histidine auxotrophs when tested in the hostmediated assay. As expected, the degree of cycasin-related mutagenic activity depends on the facility with which the compound can be enzymatically deglucosylated by the normal intestinal flora.

Cytogenetic and mutagenic effects of DDT and DDE in a Chinese hamster cell line

Abstract The mutagenic and cytogenetic effects of the chlorinated hydrocarbon 1,11-trichloro-2,2-bis( p -chlorophenyl)ethane] (DDT), and its metabolite [1,1-dichloro-2,2-bis( p -chlorophenyl)ethylene] (DDE) were investigated in vitro using a Chinese hamster cell line. A forward mutation system utilizing the 8-azaguanine sensitive to 8-azaguanine resistant marker was used as the index of mutagenic action. Methyl methanesulfonate (MMS) was used as the positive control. In all experiments, DDE consistently produced a significant increase in the mutation frequency over the control level, while DDT proved inactive. Resultsof the cytogenetic studies indicated that DDE-treated cells had a significant increase in chromosome aberrations over those occuring in the control population; exchange figures and chromatid breaks wre evident. DDT produced no significant increase in chromosome abnormalities. The Chinese hamster cell populations exposed to DDE also manifested an increased number of polyploid cells over the control level.

Effect of Aflatoxin on Human Leukocytes

Summary Aflatoxin inhibits mitosis and causes breakage and translocations in the chromosomes of cultured human leukocytes. The nonrandom pattern of breakage was confined mainly to the largest chromosomes of the human complement. Chromosome nos. 1 and 2 were particularly affected, while groups E, F, and G exhibited a lower than expected frequency of breaks. The effect of aflatoxin on human leukocytes is of the delayed type which is characteristic of chromosome breaking compounds such as alkylating agents 11 , 12 .

A collaborative study of in vivo cytogenetic analysis: I. Interpretation of slide preparations

Abstract A collaborative study was conducted to determine the validity and reproducibility of an in vivo cytogenetic technique, which consisted of examining bone marrow cells from rats for chromosome abnormalities. Four laboratories participated: government, industry, a contract laboratory and an academic institution. The rats were treated and sacrificed, and slides were prepared in the laboratories of the Food and Drug Administration with all of the collaborators participating. Three dose levels of the unknown test compound ( p,′p -DDT), a positive control compound (trimethylphosphate), or the solvent control (corn oil) were given either ip or po and as either a single treatment or daily for 5 days. The rats were sacrificed at 18, 24 or 48 hr after the single treatment or at 6 hr after the last of the multiple treatments. Results showed that agreement between laboratories was close for the criterion of breaks, and even closer for the categories of rearrangement figures and cells with more than 10 aberrations. The number of aberrations per cell appears to be the most accurate, since this criterion showed the closest agreement between laboratories at the various time intervals.

Photoactivation of chlorpromazine: cytogenetic and mutagenic effects

Abstract The mutagenic and cytogenetic effects of chlorpromazine (CPZ), a tranquilizer of the phenothiazine class, was investigated in a Chinese hamster cell line. CPZ photoactivated by exposure to dark light UV caused an increase in the number of chromosome aberrations and mutation frequency (HG-PRT+ → HG-PRT−). CPZ without dark light exposure was inactive in this test system.

Cytogenic Effects of hycanthone in the rat

Abstract Hycanthone methanesulfonate (HCT), a new drug used for the treatment of schistosomiasis, was examined for its ability to produce chromosomal abnormalities in rat bone marrow cells. Rats were given intraperitoneal injections of HCT at 40, 80, or 100 mg/kg and were killed at 6, 24, or 48 h. All levels produced a significant increase cells with abnormalities at all three time periods. There was a significant linear relationship between arithmetic dose and the proportion of cells affected. Based on two of the three experiments peformed, assuming the same slope holds in the vicinity of 0, the upper 95% confidence limits on the expected risk at level of 0.5] mg/kg would be a 0.055% increase in affected cells above control values.