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: Blockade of endothelial - mesenchymal transition by a Smad3 inhibitor delays the early development of streptozotocin - induced diabetic nephropathy .
### Output Text:
Blockade of endothelial - mesenchymal transition by a Smad3 inhibitor delays the early development of <span class="chemical">streptozotocin</span> - induced diabetic nephropathy . 