Woolley and Pringle (13) have recently reported the formation of 4-amino-5-carboxamidoimidazole during growth of Escherichia coli in the presence of 4-aminopteroylglutainic acid (aminopterin). Some of us have observed that excessive doses of folie acid speed up the leukemic process in mice and that folie acid will reverse the well known antileukemic action of aminopterin (11). This reversal of ...

Woolley and Pringle (13) have recently reported the formation of 4-amino-5-carboxamidoimidazole during growth of Escherichia coli in the presence of 4-aminopteroylglutainic acid (aminopterin). Some of us have observed that excessive doses of folie acid speed up the leukemic process in mice and that folie acid will reverse the well known antileukemic action of aminopterin (11). This reversal of ...

M EGALOBLASTIC ANEMIA is due chiefly to deficiency of vitamin B12 ( B12 ), of folic acid, or of both. Recent studies3’4’12’22 have been focused on the view that the metabolic defect leading to megaloblastosis may, in some way, be related to nucleic acid metabolism. However, the role of B12 coenzymes in mammalian nucleic acid metabolism has not been elucidated, nor are there exact data on the na...

A study of the formation of induced (adaptive) enzymes in purine or pyrimidine requiring mutants of Escherichia coli was reported in a previous publication (Pardee, 1954). The idea that synthesis of ribonucleic acid (RNA) is essential for protein synthesis is supported by the inability of the bacterial mutants to form protein and several enzymes, including f3galactosidase, in the absence of pur...

The antineoplastic alkaloid camptothecin inhibits nucleic acid synthesis in leukemia LI 210 cells; this inhibition is initially reversible, but becomes irreversible when exposure to the drug is prolonged. A drug-resistant subline, L1210/CN, can overcome camptothecin-induced inhibition of nucleic acid biosynthesis before this becomes irreversible. Unlike actinomycin D-resistant cell lines, L1210...