352 RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



slides with egg albumin, treated with xylol, and then placed in contact 

 with the film for exposure. After the photographic processing, the sec- 

 tions were stained with toluidine blue. Other studies of embryonic devel- 

 opment utihzing autoradiography include S'*^ in the rabbit fetus (48), P^' 

 in the chick (49, 50), V in the hamster (51), F^^ in the frog (52), and Cu«^ 

 in the chick (53). Radioiodine studies have been particularly helpful in 



Fui. 7-18. Effect of fluorine on l)one growth and Ca" deposition. .4, growth of distal 

 end of femur was 7.9 mm in control pig. B, comparative value was 5.0 mm in fluorine- 

 treated pig. C, line of subepiphyseal deposition in control. D, note absence of 

 original line of subepiphyseal lay-down in bone of fluorine-treated pig. [From C. L. 

 Comar, W. J. Visek, W. E. Lotz, and John H. Rust, Effects of Fluorine on Calcium 

 Metabolism and Bone Growth in Pigs, Am. J. Anat., 92: 361-389 (1953).] 



determination of the beginning of thyroid function in the frog, rat, and 

 mouse (7). 



Dysfunction. Figure 7-18 illustrates the use of Ca^^ bone autoradio- 

 grams to show the effects in pigs of high dietary fluorine, as reported by 

 Comar et al. (40). The two animals, about 135 days of age, were pair-fed 

 and thus consumed the same amount of feed except that the ration of the 

 treated pig contained about 1000 ppm fluorine. These animals were 

 sacrificed 45 days after intravenous administration of 0.5 mc Ca*^ per 

 100 lb body weight. The autoradiograms are of the femur and were made 

 by the method of Lotz et al. (23), as previously described. It may first 

 be noted that the new growth of the distal end in the 45-day period was 

 7.9 mm for the control as compared with 5.0 mm for the treated animal. 

 It is also noted that the original line of epiphyseal deposition is not present 

 in the bone of the treated pig. Numerous similar autoradiograms con- 



