Short Communication NEURAMINIDASE EFFECT ON THE GROWTH OF A TRANS- PLANTABLE NICKEL SULFIDE-INDUCED RAT TUMOR

(Sanf ord, 1967; Currie and Bagshawe, 1969; Lundgren and Simmons, 1971; Simmons et al., 1971a). Tumor cells exposed to VCN in vitro generally fail to grow in normal immunocompetent recipients (Sanford, 1967; Currie and Bagshawe, 1969; Simmons et al., 1971a). These tumor recipients, however, were rendered immune to a further challenge with the same tumor, the response being immunospecific (Simmons et al., 1971a, b; Rios and Simmons, 1973; Kollmorgen et al., 1976). In this study a weakly immunogenic nickel sulfide (Ni3S2)-induced fibrosarcoma was employed to determine its immunostimulatory potential after treatment with VCN. Attempts to immunize these rats with subthreshold doses of live tumor cells or by excision of tumor grafts met with variable success. The animals used were highly inbred female Fischer (F344) rats which were 8-10 weeks' old at the time of experimentation. The tumor used was in its sixth transplant generation. This tumor was induced by intramuscular injection of Ni3S2 according to the method described previously (Abandowitz and Basrur, 1973). The tumor was then passaged and maintained in syngeneic rats in order to preserve its homogeneity. In untreated normal rats, an inoculation of 103 cells killed 100% of the recipients. No spontaneous regressions were observed while the tumor was maintained. Tumor tissue from a subcutaneous solid tumor approximately 2 cm in diameter was obtained asceptically and minced in a petri dish with cold (4 C) Hanks' balanced salt solution (HBSS). The mixture was centrifuged at 1,200 rpm for 10 min, the supernatant discarded and the tumor mince transferred to an