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: Nephrosis was induced by injection of PAN ( 15mg / 100g body weight ) in male Sprague - Dawley ( SD ) rats .
### Output Text:
Nephrosis was induced by injection of <span class="chemical">PAN</span> ( 15mg / 100g body weight ) in male Sprague - Dawley ( SD ) rats . 