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: We have studied the role of NO and its association with apoptosis in an experimental model of nephrotic syndrome induced by a single injection of adriamycin ( ADR ) .
### Output Text:
We have studied the role of <span class="chemical">NO</span> and its association with apoptosis in an experimental model of nephrotic syndrome induced by a single injection of <span class="chemical">adriamycin</span> ( <span class="chemical">ADR</span> ) . 