Groups of 20 female

A VARIETY of neoplasms has been induced by the injection of polycyclic hydrocarbons, urethane, alkylating agents and nitrosamines into newborni mice (Pietra, Spencer and Shubik, 1959;Pietra, Rappaport and Shubik. 1961 FioreDonati, Chieco-Bianchi, de Benedictis and Maiorano, 1961;Roe. Mitchley and Walters, 1963;Toth, Magee and Shubik, 1964). The experiments to be described were designed to investigate the sensitivity of newborn mice with a viewN to using the technique for screening compounds for carcinogenic activity. A range of doses of DMBA has been tested for activity in newborn mice, and the sensitivity of the newborn to the induction of lung tumours has been coinpared witlh that of sucklings and young adults. MATERIALS AND METHODSChemical agents.-9,10-Dimethyl-1,2-benzanthracene (DMBA) was obtained from Roche Products Ltd. and gelatine powder from British Drug Houses. A suspension of DMBA in 300 aqueous gelatine was prepared by adding an acetone solution of the compound to aqueous gelatine warmed to 560 C. The acetone was driven off in a stream of nitrogen while the temperature was maintainied at this level. The dose of DMBA administered to each mouse was cointainied in 002 ml. aqueous gelatine.Mice.-BALB 'c (Bittner agent free) mice were used in both experiments.The line was originally obtained from Dr. H. B. Andervont of the National Cancer Institute, Bethesda, Maryland, and has been maintained in this Institute by brother-sister mating since 1952. The mice were housed in metal cages and given water and fed a cubed diet (Diet 86, Messrs. Dixon and Sons, Ware, Herts.) ad libitum. Every mouse was vaccinated at 6 to S weeks of age as a precaution against ectromelia. Suckling and young adult mice were injected subcutaneously in the flank and newborn mice in the scapular region. In the case of the newborn, the needle was inserted at the root of the tail and the material was deposited in the scapular region to minimise leakage. Losses due to cannibalism by the mother were small. The mice were weaned at 4 weeks, numbered on the ears and housed. 4-6 to a cage, according to group and sex. They were inspected every day. and examined thoroughly once a week, and sick mice were killed and autopsied. All surviving mice were killed 40 weeks after the day of injection and examined post mortem.

No abstract