MISCELLANEOUS WATER-SOLUBLE GROWTH FACTORS 



a gap between vitamin Bg, which has been fully discussed in Chapter V, 

 and vitamin Bjo- 



Vitamins Bio and Bn 



Concentrates of vitamins Bjo and B^^^ were prepared from liver. 

 Both factors were soluble in water, and were adsorbed on norit and 

 superfiltrol at pH 3 and eluted from the adsorbates by means of aqueous 

 alcoholic ammonia. Both factors were synthesised by a certain strain 

 of Mycobacterium tuberculosis in presence of ^-aminobenzoic acid.^ 



The existence of vitamins B^q and B^ was apparently confirmed by 

 the observation of McGinnis et al.^ that growth and feather pigmenta- 

 tion were impaired when chicks were reared on a diet of maize, peanut 

 meal, casein, soya bean oil, cod liver oil and salts, supplemented by 

 aneurine, riboflavine, pyridoxine, pantothenic acid and glycine. 



The S5anptoms said to be characteristic of a deficiency of vitamins 

 BjQ and B^, however, have been shown to be produced by a diet 

 deficient in folic acid and vitamin B^a- The addition of vitamin B^g 

 increased the growth rate, but did not improve feathering, whereas 

 the addition of folic acid improved feathering but the growth rate 

 still remained sub-optimal.* Clearly, therefore, vitamins B^q and B^^ 

 cannot be regarded as established members of the vitamin B complex. 



Vitamin B 



13 



An unidentified growth factor was isolated from distillers' dried 

 solubles by A. F. Novak and S. M. Hauge.^ This factor, termed 

 provisionally vitamin Bjg, stimulated the growth of rats at a level of 

 2 /xg. and gave a maximal response at 10 /^g. per day. It was isolated 

 by a process that included extraction with acid, precipitation of inert 

 material with alcohol, chromatographic adsorption of impurities on 

 fuller's earth, precipitation of the active fraction with phosphotungstic 

 acid and separation by chloroform extraction. 



Vitamin B14 



E. R. Norris and J. J. Majnarich ^ isolated a crystalline compound 

 from inrine that was highly active on cell proliferation in vitro and on 

 haemopoiesis in vivo ; 33 mg. were isolated from 100 1. of urine. Its 

 effect on bone-marrow proliferation was counteracted by 2-amino-4- 

 hydroxy-7-methylpteridine, which also antagonises the effect of 

 xanthopterine. Vitamin B14 was several million times as active as 

 xanthopterine, however. A single injection of o-oi jug. alleviated 

 anaemia and leucopenia in rats treated with sulphasuxidine. 



Whereas the activity of xanthopterine and pteroylglutamic acid on 



614 



