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In the control Empty group , bladders were kept empty for 6 h , and in the Distension group , bladders were kept distended for 3 h after an artificial storing - voiding cycle for 3 h .
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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:
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