Growth Factors, Minerals and Vitamins The short life span of mature blood cells requires their continuous replacement, a process termed hematopoiesis New cell production must be responsive to both basal needs and situations of increased demand HEMATOPOIETIC AGENTS

VITAMIN B 12 Vitamin B 12 and folic acid are dietary essentials A deficiency of either vitamin results in defective synthesis of DNA in any cell in which chrosomal replication and division are taking place An early sign of deficiency is a megaloblastic anemia

VITAMIN B 12 Cyanocobalamin Hydroxocobalamin Methylcobalamin 5-Deoxyadenosylcobalamin

VITAMIN B 12 Metabolic functions The active coenzymes CH 3 B 12 and Deoxyadensoyl B 12 are essential for cell growth and replacation. CH 3 B 12 is required for the formation of methionine and its derivative S-adenosylmethionine from homocysteine. 5-Deoxyadenosylcobalamin is requred for the isomerization of L-methylmalonyl CoA to succinyl CoA.

FOLIC ACID Metabolic Functions Conversion of homocysteine to methionine (CH 3 H 4 PteGlu) Conversion of serine to glycine (H 4 PteGlu) Synthesis of thymidilate (5,10-CH 2 H 4 PteGlu) Histidine metabolism (H 4 PteGlu) Synthesis of purines Utilization or generation of formate