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: Western blot analysis showed that isoproterenol - induced phosphorylation of STAT3 was maintained or further enhanced by betaine treatment in myocardium .
### Output Text:
Western blot analysis showed that <span class="chemical">isoproterenol</span> - induced phosphorylation of STAT3 was maintained or further enhanced by <span class="chemical">betaine</span> treatment in myocardium . 