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: Pituitary tumors were induced in F344 female rats by chronic treatment with diethylstilbestrol ( DES , 8 - 10 mg ) implanted subcutaneously in silastic capsules .
### Output Text:
Pituitary tumors were induced in F344 female rats by chronic treatment with <span class="chemical">diethylstilbestrol</span> ( <span class="chemical">DES</span> , 8 - 10 mg ) implanted subcutaneously in silastic capsules . 