the specific functions expressed by differentiated cells are extinguished when these cells are crossed with somatic cells of another histotype or with cells of the same differentiation that fail to express these functions : in rat hepatoma x mouse fibroblast hybrids , tyrosine aminotransferase ( tat ) and phosphoenolypyruvate carboxykinase ( pepck ) activities are extinguished as they are in hybrids between the same rat hepatoma cell line and mouse hepatoma cells that do not express these two enzymes .
C0007634
cells
C0007589
cells