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: Reduction of heparan sulphate - associated anionic sites in the glomerular basement membrane of rats with streptozotocin - induced diabetic nephropathy .
### Output Text:
Reduction of <span class="chemical">heparan sulphate</span> - associated anionic sites in the glomerular basement membrane of rats with <span class="chemical">streptozotocin</span> - induced diabetic nephropathy . 