21.   The research looked at tissue plasminogen activator, TPA, an enzyme that dissolves clots.

22.   TPA dissolves clots, while ancrod lowers blood levels of fibrinogen, a substance that can help form clots.

23.   TPA is a naturally occurring protein that dissolves clots.

24.   Twigg said it could take up to a year to dissolve the clot but that Quayle would have no restrictions on his activity during that time.

25.   The paper said that one example is the lack of information in medical textbooks about new available drugs to dissolve clots.