422 VITAMIN Bi2 



coworkers^ stated that blood non-protein nitrogen was "greatly elevated" 

 in deficient chicks receiving the basal diet plus either vitamin-free casein 

 or "a protein" but was lowered to control levels when an alcohol-soluble 

 liver fraction was added to the basal diet. Schultze^ found that acute 

 uremia occurred in newborn rats from mothers on diets containing soybean 

 protein and methionine as the only sources of amino acids. The uremia was 

 prevented by injecting the young subcutaneously with 0.05 y of vitamin 

 Bi2 soon after birth. It was noted^ that the blood levels of non-protein 

 nitrogen and of seven individual amino acids were lower in chicks which 

 received a supplement containing vitamin B12 than in chicks on a basal 

 diet deficient in the vitamin. 



B. VITAMIN B12 AND THYROTOXICITY 



The feeding of thyroxine or desiccated thyroid in large doses to adult 

 rats has been reported to cause losses of body and ovarian weight, accom- 

 panied by anestrus, which can be prevented by high levels of thiamine or 

 yeast. ^ These supplements were reported not to be effective in young 

 rats.^" The existence of a dietary factor in liver which alleviated the toxicity 

 of thyroid powder for immature rats was noted in 1947 by Ershoff,^^ who 

 found that yeast, wheat germ, casein, and ten synthetic B vitamins were 

 ineffective, and by Betheil and coworkers, who reported that high levels 

 of yeast or moderate levels of dried liver were similarly effective. ^^ These 

 findings were used by Robblee and coworkers in studies with chicks.'^ It 

 was found that the thyrotoxic condition was counteracted by supplementing 

 the diet with fish solubles or by injecting anti-pernicious anemia liver 

 extract, and the conclusion was drawn that the addition of either 0.125% 

 desiccated thyroid or 0.02 to 0.03 % iodinated casein to the basal diet 

 improved the assay procedure for the unidentified chick growth factor 

 present in fish solubles and liver extract. The use of thyroid-supplemented 

 diets in the assay of liver preparations with rats and mice was adopted 

 by various investigators,^*-^^ and rats on such diets were shown to respond 



6 J. McGinnis, P. T. Hsu, and W. D. Graham, Poultry Sci. 27, 674 (1948). 



^M. O. Schultze, Proc. Soc. Exptl. Biol. Med. 72, 613 (1949). 



8 L. W. Charkey, H. S. Wilgus. A. R. Patton, and F. X. Gassner, Proc. Soc. Exptl. 



Biol. Med. 73, 21 (1950). 

 3 V. A. Drill, R. Overman, and J. H. Leathem, Endocrinology 32, 327 (1943). 

 »" B. H. Ershoff, Endocrinology 37, 218 (1945). 



11 B. H. Ershoff, Proc. Soc. Exptl. Biol. Med. 64, 500 (1947). 



12 J. J. Betheil, V. D. Wiebelhaus, and H. A. Lardy, ./. Nutrition 34, 431 (1947). 



13 A. R. Robblee, C. A. Nichol, W. W. Cravens, C. A. Elvehjem, and J. G. Halpin, 

 Proc. Soc. Exptl. Biol. Med. 67, 400 (1948). 



" U. D. Register, W. R. Ruegamer, and C. A. Elvehjem, J. Biol. (Jhcm. 177, 129 

 (1949). 



