OBJECTIVES: 1. Completion of methods for determination of the activity of delta-aminolevulinate synthase in intact cells of chick embryo liver in culture. 2. Completion of evidence to support the hypothesis that induction of the synthesis of delta-aminolevulinate synthase requires an increase in active mRNA and depletion of heme; the two reactions are in tandem and therefore synergistic. 3. Studies on the mechanism of delta-aminolevulinic acid synthesis in plants to determine the pathway from alpha-ketoglutarate possibly through diketovaleric acid. 4. Studies of the control mechanisms for plasma protein synthesis by chick embryo liver cells in culture.