Toxicity of Rubber Stoppers for Tissue Cultures. ∗ †

Abstract

Discussion and Conclusions

In most laboratories, it is customary to treat new rubber stoppers with hot alkali and acid in order to remove surface impurities. But in the present experiments, based on more than 500 cultures, stoppers that were strongly toxic in the beginning remained toxic even after the most rigorous treatment. It should be emphasized that the toxicity of rubber stoppers is much more evident in cultures maintained in synthetic media than in media containing such naturally-occurring ingredients as blood plasma, blood serum and tissue extracts. For this reason, extreme care should be taken to avoid toxic stoppers in all experiments in which protein-free media are used. And since animal cells cultivated in synthetic media serve as extremely sensitive test objects, the information reported here can almost certainly be applied to other biological systems.