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Despite these technologic advances , it is still not clear whether excessive narrowing in asthma is driven by ASM abnormalities , by other alterations in non - muscle factors or simply because of the overexpression of spasmogens .
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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