COBALT 24 1 



Labeled vitamin B12 was produced by incorporation of 2 ppm Co with 

 a specific activity of 1.94 X 10^ counts/min/mg of Co''" into the fermenta- 

 tion broth in which Strcptomijccs griscus was grown. The activity of this 

 vitamin B12 was about 0.25 ^ic/mg. However, much higher activities 

 have since been produced (Co-10). In a study with pregnant rats, 0.2 fxg 

 of labeled vitamin B12 containing GO ^^c/mg was administered subcutane- 

 ously daily for 2 to 4 days (Co-11). Tissues and carcass residues were 

 digested with H2SO4 and HNO;j plus cobalt carrier in a Kjeldahl flask, and 

 the inorganic residues were transferred to planchets for counting with a 

 Geiger tube. 



The behavior of cobalt in soils was studied by adding labeled cobalt 

 to a 5-g sample of soil and then following its removal in extracting solu- 

 tions of ammonium acetate, 2.5 per cent acetic acid, and 0.1 A'^ HCl. 

 Radioactivity was measured on 100-ml samples using the Marinelli beaker 

 arrangement; an amount of activity measuring 5200 counts/min was 

 employed per 5-g soil sample (Co-12). 



Co-l. Ely, Ray E., K. M. Dunn, C. F. Huffman, C. L. Comar, and George K. Davis: 

 The Effect of Methionine on the Tissue Distribution of Radioactive Cobalt 

 Injected Intravenously into Dairy Calves, /. Animal Sci., 12: 394-401 (1953). 



Co-2. Keener, H. A., G. P. Percival, K. S. Morrow, and G. H. Ellis: Cobalt Tolerance 

 in Young Dairy Cattle, J. Dairy Sci., 32: 527-533 (1949). 



Co-3. Ellis, G. H., and J. F. Thompson: Determination of Cobalt in Biological 

 Materials with Nitrosocresol, Ind. Eng. Chem. Anal. Ed., 17: 254-257 (1945). 



Co-4. Comar, C. L., George K. Davis, and Ruth F. Taylor: Cobalt Metabolism 

 Studies: Radioactive Cobalt Procedures with Rats and Cattle, Arch. Biochem., 

 9: 149-158 (1946). 



Co-5. Ulrich, Frank, and D. Harold Copp: The Metabolism of Radioactive Cobalt 

 (Co®°) in Normal and Alloxan Diabetic Rats, Arch. Biochem. and Biophys., 31 : 

 148-153 (1951). 



Co-6. Comar, C. L., and George K. Davis: Cobalt Metabolism Studies. III. Excre- 

 tion and Tissue Distribution of Radioactive Cobalt Administered to Cattle, 

 Arch. Biochem., 12: 257-266 (1947). 



Co-7. Comar, C. L., and George K. Davis: Cobalt Metabolism Studies. IV. Tissue 

 Distribution of Radioactive Cobalt Administered to Rabbits, Swine, and 

 Young Calves, J. Biol. Chem., 170: 379-389 (1947). 



Co-8. Braude, R. : The Distribution of Radioactive Cobalt in Pigs, Brit. J. Nutrition, 

 3: 289 (1949). 



Co-9. Monroe, R. A., H. E. Sauberlich, C. L. Comar, and S. L. Hood: Vitamin B12 

 Biosynthesis after Oral and Intravenous Administration of Inorganic Co^" to 

 Sheep, Proc. Soc. Exptl. Biol. Med., 80: 250-257 (1952). 

 Co-10. Chaiet, Louis, Charles Roaenblum, and David T. Woodbury: Biosynthesis 

 of Radioactive Vitamin B,,. Containing Cobalt^o, Science, 111 : 601-602 (1950). 

 Co-11. Chow, Bacon F., Lois Barrmvs, and C. T. Ling: The Distribution of Radio- 

 activity in the Organs of the Fetus or of Young Rats Born by Mothers Injected 

 with Vitamin B12 Containing Co^", Arch. Biochem. and Biophys., 34: 151 157 

 (1951). 

 Co-12. Banerjee, Dilip K., Roger H. Bray, and S. W. Melsted: Some Aspects of the 

 Chemistry of Cobalt in Soils, Soil Sci., 75: 421-431 (1953). 



