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Studies were initiated to determine the practicality of using various tissue cultures for the propagation of murine viruses isolated from laboratory animals. The cytopathogenic effects of 10 murine viruses known to cause disease in laboratory rodents were compared in monolayer cultures of L929, BHK-21, WI-38, BSC-1, and Vero cells. The susceptibility of primary hamster embryo, hamster kidney, mouse embryo, mouse kidney, and rat embryo cell cultures was also tested. Seven of the viruses produced effects in at least 1 of the cell substrates. The remaining 3 viruses, namely H-1, K, and mouse hepatitis, produced no effects in the cell cultures tested.

Effects of various oxygen concentrations and culture media on the maintenance of 4-day-old hamster trachea organ cultures and the yield of Sendai virus were studied. The basic media used were Eagle minimal essential medium, medium 199, and CMRL 1066 supplemented with glutamine and antibiotics and buffered with NaHCO3 or N-2-hydroxyethyl-piperazine-N'-2'-ethanesulfonic acid (HEPES). In addition, each medium was evaluated under a gas phase of 5% CO2 and 95% O2, 5% CO2 and 45% O2 and 50% N2, or 5% CO2 and 95% air. Culturing of explants with CMRL 1066 and medium 199 buffered with HEPES in the presence of 5% CO2 and air proved most efficient; ciliary movement and ciliated surface epithelium were maintained for periods up to 27 days. No significant difference in the rate of replication of Sendai virus was seen in the three different media with the two buffer systems in the three different gaseous phases. The addition of 0.2% bovine serum albumin to the media yielded greater quantities of virus, up to 200-fold increase in titer without producing changes in ciliary function. A distinctive pattern of morphological changes was observed in explants of trachea epithelia inoculated with Sendai virus. These results suggest the practical application in the use of whole hamster trachea explants as a diagnostic aid in the isolation of Sendai virus from laboratory rodents.

Bioassays of amosite, short-range (SR), intermediate-range (IR) or intermediate-range chrysotile asbestos in combination with the intestinal carcinogen 1,2-dimethylhydrazine dihydrochloride (DMH) were conducted with male and female Syrian golden hamsters. Amosite and both forms of chrysotile asbestos were administered at a concentration of 1% in pelleted diet for the entire lifetime of the hamsters starting with mothers of the test animals. Group sizes varied from 125-254. There was no adverse effect on body weight gain or survival by either type of asbestos or by IR chrysotile asbestos in combination with DMH. A significant increase (p less than 0.05) in adrenal cortical tumors was observed in male hamsters exposed to SR and IR chrysotile asbestos and in females treated with IR chrysotile asbestos when compared to the pooled control groups. However, statistical significance (p less than 0.05) was lost when these dosed groups were compared with temporal control groups. Neither of the male or female amosite asbestos groups showed increased neoplasia in any tissue or organ compared to the control groups. The cocarcinogen studies using IR chrysotile asbestos and 1,2-dimethylhydrazine dihydrochloride were considered inadequate because there was no increase in intestinal neoplasia in the DMH group.