Final answer:
John Gurdon concluded that at least some nuclei of differentiated animal cells are totipotent.
Step-by-step explanation:
The nuclei that biologist John Gurdon isolated from a tadpole's intestinal epithelial cells developed into the tadpole stage, leading him to conclude that at least some nuclei of differentiated animal cells are totipotent. Totipotent stem cells have the potential to differentiate into any type of cell needed for an organism to grow and develop. In this case, the isolated nuclei were able to develop into a whole tadpole, indicating their totipotent nature.