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 treated with Dex alone , SBP was increased from 109 + / - 2 to 133 + / - 2 mmHg on Days 4 and Day 14 , respectively ( P < 0 . 001 ) .
### Output Text:
In rats treated with <span class="chemical">Dex</span> alone , SBP was increased from 109 + / - 2 to 133 + / - 2 mmHg on Days 4 and Day 14 , respectively ( P < 0 . 001 ) . 