Specifically, gene-encoded biological probes serve as stable and 
high-performance tools to visualize cellular fate in living animals. The rat, as 
with the mouse, has offered important animal models for biology and medical 
research, and has provided a wealth of physiological and pharmacological data. 
The larger-body animals, in comparison to the mouse have allowed the application 
of various physiological and surgical manipulations that may prove to have 
biological significance. We have further extended the techniques of genetic 
engineering to rats, rabbits, and pigs, and have created corresponding 
GFP-transgenic animals. The GFP-positive organs of these animals provide 
valuable sensors in preclinical settings for cell therapy and transplantation 
studies. In this chapter, we highlight expression profiles in these animal 
resources and describe examples of preclinical applications.