A method has been described by which whole cells may be separated from the thymus tissue of rats. Cells obtained by this method have been found capable of incorporating leucine, valine, glycine, and alanine (labeled with C14 in the carboxyl position) at a rate equal to or slightly higher than that observed in slices of thymus tissue, in Yoshida ascites tumor cells from the rat, and in Ehrlich hyperdiploid ascites tumor cells from the mouse.

Cells isolated by this technic continued to synthesize protein in vitro for at least 4 hours. Gentle washing did not alter this capacity of the cells.

The results obtained with “nuclei” prepared by the method of Allfrey and Mirsky agreed closely with results obtained from “cells” prepared by the technic described here. Both “cells” and “nuclei” incorporated C14-labeled amino acids into protein more readily when suspended in Tyrode solution with added rat serum than when suspended in Allfrey and Mirsky's medium (sucrose-CaCl2-phosphate buffer).

The data reported here indicate that, in suspensions of “nuclei” prepared by Allfrey and Mirsky's method, as well as in suspensions of cells prepared by the method we have used, we have been dealing with preparations which react like intact, viable cells. Such cells, isolated from the thymus gland, afford an excellent normal control tissue for metabolic comparison with ascites tumor cells.

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This investigation was supported in part by a grant (No. C-2867) from the National Cancer Institute, National Institutes of Health, United States Public Health Service; and by a grant from the Massachusetts Division, American Cancer Society.

This is Publication #1020 of the Cancer Commission of Harvard University.

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