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: Dexamethasone - ( Dex - ) induced hypertension is associated with enhanced oxidative stress .
### Output Text:
<span class="chemical">Dexamethasone</span> - ( <span class="chemical">Dex</span> - ) induced hypertension is associated with enhanced oxidative stress . 