[Figure 22] shows how animals differ in their retention of orally administered zinc-65, as revealed by a whole body counter. It is apparent that counters can be used to determine the differences in the metabolism of different animal species used for research. Standard data developed in this way can serve to reduce error that may occur if results from one species are used for interpretation of data for another species, such as man.
A University of Illinois project to breed meat animals with a high lean-to-fat ratio has been aided by whole body counters. The tendency to deposit fat seems to be inherited, and breeding stock with low fat content can be selected, using “muscle-seeking” potassium-40 to show the proportion of muscle in each potential parent. The Illinois counter is unique in being large enough to examine an adult steer ([Figure 23]). A similar counter at Cornell University has been used to study animals infested with internal parasites, comparing them with parasite-free animals. The counter revealed that a positive relationship exists between the level of parasite infestation and loss of iron-59-labeled blood from the digestive tract. The possibility of using this method to evaluate parasite-killing drugs is being considered. The Cornell counter is kept clean by covering the animals with plastic sheeting. The same counter also can serve human patients, who are positioned in a wheeled hospital stretcher. (See [Figure 1D].)
CONCLUSION
This booklet has presented a sample of the ways whole body counters add to man’s knowledge and increase his ability to manage conditions and processes important to his health and well-being. Radioactive substances occur naturally within our own bodies and all other materials. Whole body counters measure this radioactivity, or any which may have been added from artificial sources.
We have seen how these sensitive instruments help to prove hypotheses difficult to verify otherwise and how they thereby may stimulate new and fruitful scientific experimentation. We have learned how whole body counters add to our knowledge of normal processes in healthy bodies and detect disease or abnormalities resulting from dangerous conditions.
Figure 23 A University of Illinois counter large enough to examine an adult steer, above. A Cornell University counter used for animal-parasite studies, below.
Figure 24 A trailer-mounted whole body counter used for research. School children were examined in a project to determine possible pathways by which radioactivity may enter the human body.