CARBON 223 



Carbon 14 (5508 yr) Hcla OA'iii (lamnia 



Cat. No. Sp. Ad. Form Cost Chem. Conl. liudiochem. Cont. 



C-14-P-1 0.25-1.5 mc/mg BaCOj $36/mc — — 



MicaW. Int.C. 50% Self-abs. 



5 X 10-^ 0.9 X 10-« 6 (calc.) 



Critical Org. Body Air Water Effect. Ti,^ 



Fat and bone 250 mc lO"" 3 X IQ-^ 180 days 



Dosage Levels. Carbon 14 has been widely used as a label for so 

 many organic compounds in biological experiments that it is virtually 

 impossible to enumerate them individually and difficult to generalize. 

 The amount of activity required will depend upon the purpose of the 

 study (e.g., biosynthesis or tracer), the metabolic behavior of the labeled 

 compound, and the sensitivity of the measurement. Following are some 

 levels that have been used: With rats, mice, and guinea pigs, for routes of 

 administration such as oral, intraperitoneal, intravenous, and skin and for 

 such compounds as carbonate, bicarbonate, acetate, amino acids, ascorbic 

 acid, adrenahn, codeine, digitoxin, and ergosterol, the dosage has ranged 

 from 1 to 50 /xc With rabbits, 50 mc of labeled acetate has been employed 

 to follow fatty acid metabolism (C-1). With pigeons, 0.4 to 20 yuc has 

 been used to study biosynthesis of uric acid (C-2) ; goats, 5 mc of labeled 

 acetate to stud}^ lactose and glycerol formation (C-3) ; dairy cows, 7 mc 

 sodium carbonate and 5 mc sodium propionate (C-4, C-5) ; and 1 to 6 mc 

 of carbon-labeled substances has been used in perfused-udder studies 

 (C-6). About 2.7 X 10^ counts/min of C^^ was injected into the silk- 

 worm for synthesis of radioactive silk (C-7). Cockroaches have been 

 injected with 20 ^g of C ^''-labeled DDT with a specific activity of 1.5 mc/- 

 mmole (C-8). 



C^Mabeled acids were infiltrated into tobacco by cutting the leaves 

 underwater and submerging them in a solution of pH 5.5 containing 5000 

 to 20,000 counts/min/ml (C-9). The container was paraffin-coated, and 

 after the leaf was submerged, it was evacuated for 30 to 60 sec in a vacuum 

 desiccator, and the vacuum then released slowly. For studies on rubber 

 formation, guayule plants were grown in quartz sand with nutrient solu- 

 tion, and 0.231 mc of C'''-labeled acetate per plant was introduced and 

 allowed to remain in contact with the plant for 55 hr (C-10). In a tracer 

 study of C^^ movement in the geranium, the attached leaf was enclosed 

 in a glass photosynthetic chamber, and CO2 supplied at a concentration 

 of 1.5 per cent by volume containing about 0.25 mc C'^ (C-11). Radio- 

 active asparagine was prepared by placing 8- to 9-day-old seedlings in an 

 8-liter desiccator filled with air containing 5 per cent CO2 and 0.25 mc 

 C^^Oz for 24 hr under continuous illumination (C-12). The yields were 



