11.   No one has yet shown that a normal prion can be transformed into an abnormal prion and then cause disease.

12.   The normal prion is a healthy brain protein that may play a role in nerve signaling.

13.   They point especially to the fact that no one has been able to convert a normal human prion into a lethal one in a test tube.

14.   When a misfolded prion comes into contact with a healthy prion, he said, it can sometimes force the normal prion to change shape.

15.   When the abnormal protein gets into the brain of a healthy human or animal, it interacts with and converts normal prions into its own form.

16.   And when these rogue proteins encounter normal prions in the brain, they convert the normal forms to the disease-causing shape.

17.   In the mouse cell experiments, the two drugs were found to inhibit the conversion of normal prions into the disease-causing, abnormal form.

18.   But when a normal prion mutates, it destroys brain nerve systems and causes crippling diseases, including mad cow disease.

19.   Normal prions exist in the bodies of many creatures.