78 P-AMINOBENZOIC ACID 



foiiamides, and the inhibition is reversed by PABA in the experiments of 

 Bonner.*^' Sulfanilamide inhibition of the growth of onion iAUnnn capa) 

 rootlets is reversed with PABA, according to Stoll.^" Ciermination of rice 

 seeds is retarded by sulfanilamide, and the effect is reversed with PABA in 

 the experiments of Ribeiro.'" Chodat and Soloweitchik^- foinid that PABA 

 reduces the cytostatic influence of sulfanilamide on various species of 

 green algae. Growth of a fresh-water diatom {Nitzschia palea) is inhibited 

 by sulfonamides and the inhibition is reversed with PABA, according to 

 Wiedling.^^' ^* In experiments of Efimov,^^ PABA was reported to counter- 

 act the depressant effect of sulfanilamide on isolated frog hearts. PABA 

 has been reported to reverse the effect of sulfanilamide in inhibiting the 

 adsorption of methylene blue by charcoal. ^^ The foregoing enumeration of 

 antagonisms between PABA and the sulfonamides that have been demon- 

 strated in non-bacterial systems is by no means exhaustive. 



Although the aromatic sulfones are quite different from the sulfonamides 

 in structure and have a different spectrum of antibacterial activity, such as 

 might be expected if their mechanism of action were different, it has been 

 shown by Steenken and Heise^^ that PABA antagonizes in vitro the anti- 

 tubercular activity of promin. 



p-Aminosalicylic acid, a compound resembling both sulfanilamide and 

 PABA in structure, was found by Lehmann''*' ^^ to be a remarkably specific 

 chemotherapeutic agent against Mycobacterium tuberculosis both in vitro 

 and in vivo. 



«s J. Bonner, Proc. Natl. Acad. Sci. U. S. 28, 321 (1942). 



80 R. Stoll, Compt. rend. soc. biol. 137, 170 (1943). 



91 F. Ribeiro, J. Biol. Chem. 152, 665 (1944). 



'2 F. Chodat and S. Soloweitchik, Compt. rend. soc. phys. hist. nal. Genhve 59, 167 



(1942) [C. A. 38, 5530 (1944)]. 

 9^8. Wiedling, Nature 150, 290 (1942). 

 9*S. Wiedling, Science 94, 389 (1941). 



" N. I. Efimov, Farmakol. i Toksikol. 8, No. 5, 28 (1945) [C. A. 40, 7409 (1946)]. 

 9" H. C. Eyster, /. Cellular Comp. Physiol. 21, 191 (1943). 

 9^ W. Steenken, Jr., and F. H. Heise, Proc. Soc. Expil. Biol. Med. 52, 180 (1943). 



98 J. Lehmann, Lancet 250, 14, 15 (1946). 



99 J. Lehmann, Svenska Lakartidn. 43, 2029 (1946) [C. A. 41, 1334 (1947)]. 



