Evaluation of the Interaction of Three Genotoxic Agents in Eliciting Sister-Chromatid Exchanges Using Response Surface Methodology

Chinese hamster cells (V79) were treated with ethylnitrosourea(ENU), bischloroethylnitrosourea (BCNU), and cis-diamminedichloroplatinum(II)(DDP) alone and in combination. Sister chromatid exchanges (SCEs)were quantitated as measures of genotoxicity of the three agents.The combination experiment employed a factorial design in whichcells were treated, in various concentration combinations, withall agents simultaneously. Response surface methodology usinga polynomial model in treatment variables to approximate themean the distribution of SCE events was employed for analysisof the interactions of the three genotoxic agents. Due to unequalvariances of the number of SCEs in the various treatment groups,a weighted leastsquares analysis was used to estimate the parametersof the dose-response relationship. The single-agent resultssuggest that the DDP concentration-response curve has a muchsteeper slope than the ENU and BCNU curves, and is concave downwardas compared to the relatively linear concentration-responsecurves of ENU and BCNU. The combination results suggest thatENU and DDP are involved in a negative interaction. The BCNTJ/DDPinteraction, the ENU/BCNU interaction, and the three-factorinteraction are not statistically significant. The analysisof these data demonstrates the usefulness of a statistical procedurefor evaluating the biological effects resulting from exposureto multiple cytotoxic agents. The methodology can be used withmany other types of endpoints and is not limited by the numberof treatment agents.     

Chronic Toxicity, Reproductive, and Teratogenic Studies of Hexazinone

Chronic Toxicity, Reproductive, and Teratogenic Studies of Hexazinone.Kennedy, G. L., Jr., and Kaplan, A. M. (1984). Fundam. Appl.Toxicol. 4, 960–971. Hexazinone [3-cydohexyl-6-(dimethylammino)-1-methyl-1,3,5-triazine2,4(1H,3H)-dione; CAS 51235-04-2] was tested for oral toxicityin rats (both 90-day and 2-year feeding studies), mice (8-weekand 2-year feeding studies), and dogs (90-day feeding study).The teratogenic potential was evaluated in rabbits and ratsand functional reproductive capacity was studied in rats. Ninety-dayfeeding of up to 1000 ppm produced no signs of a toxic responsein rats. Rats fed 5000 ppm had growth curves slightly inferiorto those of the controls as the only detectable difference.Extending the feeding period to 2 years produced decreased bodyweights in males fed 2500 ppm (top level tested) and in femalesfed either 1000 or 2500 ppm. All other indices of response,including the type and distribution of tumors, were similarin the test and control rats with the no-effect level being200 ppm. Eight-week feeding of up to 10,000 ppm in mice producedincreased liver weight only at the highest level without anyother changes. Two-year feeding of either 200, 2500, or 10,000ppm resulted in sloughing of the distal tip of the tail andincreased liver weights among mice fed 10,000 ppm. Hypertrophyof centrilobular hepatocytes and hyperplasic nodules were increasedin mice fed either 2500 or 10,000 ppm. No evidence of a tumorigenicresponse was evident The no-effect level was 200 ppm. Dogs fed5000 ppm for 90 days had decreased rate of body weight gainwith clinical enzyme changes suggestive of liver damage. Microscopicexamination of the liver failed to reveal any alterations anddogs fed either 200 or 1000 ppm were indistinguishable fromcontrols. The no-effect level in the dog was 1000 ppm. No evidenceof a teratogenic response was seen in either rats or rabbitsand reproduction capacity in rats fed up to 2500 ppm for threegenerations was unaffected     

The Use of Heparin in Autoimmune Hemolytic Disease

Seven patients with various forms of autoimmune hemolytic anemia weretreated with parenteral heparin. A therapeutic failure resulted in all instances.Heparin therapy did not induce a clinical response or reduce the magnitude ofhemolysis. There was no demonstrable in vivo or in vitro effect of this drugon direct and indirect antiglobulin and bromelin tests. Serum complementlevels and the degree of erythrocyte mobility were unaffected by heparin during the therapeutic trial.

Submitted on July 8, 1969 Accepted on November 25, 1969