In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The absence of induction of these genes as well as hepatomegaly in PPARalpha knockout [ PPARalpha - / - ] mice indicated that the effects of amiodarone were dependent upon the presence of a functional PPARalpha gene .
### Output Text:
The absence of induction of these genes as well as hepatomegaly in PPARalpha knockout [ PPARalpha - / - ] mice indicated that the effects of <span class="chemical">amiodarone</span> were dependent upon the presence of a functional PPARalpha gene . 