Abstract
In a previous paper 1 we have shown that peptone prepared from the yolk of egg is non-toxic for growing chicken cells even when added in considerable concentration to the medium. Egg yolk digested to the point of crystallizing out an a-amino acid is toxic. We tested a large number of a-amino acids and have found that all are toxic for the cells. In low dilution they stimulate the contraction of heart muscle fragments but did not affect the growth. In higher dilution they inhibit the growth of cells completely and killed.
Having established this fact it became of interest to study the effect of dipeptids in a similar manner. Leucyl-glycin and carnosin have been tested. The leucyl-glycin was a synthetic product. The carnosin was obtained from muscle. It was prepared by Dr. D. W. Wilson.
Both of these substances are toxic in large doses. Their toxicity is not as marked, however, as is that of the α-amino acids. The leucylglycin is more toxic than the carnosin.
During the course of these experiments we prepared and tested peptones prepared from beef. These were found not to affect in any way the growth of the cells.
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