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: In rats with immune experimental glomerulonephritis , 5 / 6 rats given DX died within 7 days , in contrast to animals treated by DXNP , NP , or untreated , which all survived .
### Output Text:
In rats with immune experimental glomerulonephritis , 5 / 6 rats given <span class="chemical">DX</span> died within 7 days , in contrast to animals treated by DXNP , NP , or untreated , which all survived . 