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: CONCLUSIONS : Among markers of ischemic injury after DOX in rats , cTnT showed the greatest ability to detect myocardial damage assessed by echocardiographic detection and histological changes .
### Output Text:
CONCLUSIONS : Among markers of ischemic injury after <span class="chemical">DOX</span> in rats , cTnT showed the greatest ability to detect myocardial damage assessed by echocardiographic detection and histological changes . 