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 mechanism of isoproterenol - induced myocardial damage is unknown , but a mismatch of oxygen supply vs . demand following coronary hypotension and myocardial hyperactivity is the best explanation for the complex morphological alterations observed .
### Output Text:
The mechanism of <span class="chemical">isoproterenol</span> - induced myocardial damage is unknown , but a mismatch of <span class="chemical">oxygen</span> supply vs . demand following coronary hypotension and myocardial hyperactivity is the best explanation for the complex morphological alterations observed . 