2254
In contrast , overexpression of mouse butyrylcholinesterase ( BChE ) , a proven stoichiometric bioscavenger of OP compounds , protected 5 out of 6 mice from DFP lethality and surviving mice showed no symptoms of DFP toxicity .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None