THE INHIBITION OF TWO STEROID-ACTIVATED NICOTINAMIDE-ADENINE DINUCLEOTIDE (PHOSPHATE) TRANSHYDROGENASES BY FOLIC ACID AND FOLIC ACID ANTIMETABOLITES

1. It was found that steroid-mediated nicotinamide-adenine dinucleotide (phosphate) transhydrogenases can be inhibited in vitro by folic acid and its antimetabolites. The most potent inhibitor was methotrexate, a drug with a high therapeutic index against experimental cancer. 2. The inhibitions produced by a combination of folic acid and the analogues were additive, as were those between the folic acid compounds and antagonistic steroid hormones.

THE EFFECT OF 6-MERCAPTOPURINE AND AMINOPTERIN ON EXPERIMENTAL IMMUNE THYROIDITIS IN GUINEA PIGS

The influence of 6-mercaptopurine and aminopterin was studied on immune response and immune thyroiditis in guinea pigs immunized with thyroid extract. 1. Both compounds depressed delayed hypersensitivity to thyroglobulin and immune thyroiditis. 2. Antibody formation to thyroglobulin was strongly depressed by aminopterin but not significantly influenced by 6-mercaptopurine. 3. Immune response and thyroiditis were suppressed as long as the compounds were administered; after discontinuation of treatment, immune response and thyroiditis appeared in the same time intervals as observed in control animals after initiation of immunization. 4. Treatment with 6-mercaptopurine and aminopterin 10 days after immunization lead to suppression of delayed hypersensitivity and thyroiditis. 5. Treatment with 6-mercaptopurine of animals after onset of thyroiditis lead to suppression of delayed hypersensitivity and disappearance or diminution of round cell infiltration in the thyroid. 6. The results are discussed in terms of the pathogenesis of experimental immune thyroiditis, the mode of action of these antimetabolites on this experimental immune disease, and in view of the potential value of these compounds in human diseases.

CHROMOSOMAL LOCATION OF THYMINE AND ARGININE GENES IN ESCHERICHIA COLI AND AN F' INCORPORATING THEM

Ishibashi, Masahide (Osaka University, Osaka, Japan), Yoshinobu Sugino, and Yukinori Hirota. Chromosomal location of thymine and arginine genes in Escherichia coli and an F' incorporating them. J. Bacteriol. 87:554-561. 1964.-The gene responsible for thymine requirement or independence in Escherichia coli K-12 is located on the chromosome, near Arg(2) (arginine) and between Sm (streptomycin) and Ade (adenine). A new F' (called F(15)) carrying the Thy (thymine) gene as well as the Arg(2) gene was discovered. The Thy(+) (thymine independent) gene on F(15) relieves the defect of all Thy(-) (thymine requiring) mutants of E. coli examined, such as E. coli 15 T(-), B3, and Thy(-) mutants obtained by aminopterine treatment. It can also be transferred to Thy(-) mutants of Salmonella typhimurium and Serratia marcescens, converting them to Thy(+).

THE INHIBITION OF NICOTINAMIDE-ADENINE DINUCLEOTIDE-LINKED 3-ALPHA-HYDROXY STEROID DEHYDROGENASE BY CERTAIN ANTIMETABOLIC DRUGS

1. The inhibition of NAD-linked 3alpha-hydroxy steroid dehydrogenase in vitro by some of the more therapeutically effective antimetabolic drugs has been investigated. 2. Antipurine and antifolic acid drugs inhibit this system, as does folic acid. 3. Combinations of antifolic acid drugs and folic acid itself produce an additive but not synergic inhibition. 4. Antimetabolic drugs give inhibitions that are additive to those produced by antagonistic steroid hormones.

INHIBITION OF THE LYMPHOCYTE RESPONSE TO INFLAMMATION WITH ANTIMETABOLITES

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