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: Conventional SD rats fed diet L - 485 and treated with testosterone developed only prostatitis .
### Output Text:
Conventional SD rats fed diet L - 485 and treated with <span class="chemical">testosterone</span> developed only prostatitis . 