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: Heparan sulphate - associated anionic sites in the glomerular basement membrane were studied in rats 8 months after induction of diabetes by streptozotocin and in age - adn sex - matched control rats , employing the cationic dye cuprolinic blue .
### Output Text:
<span class="chemical">Heparan sulphate</span> - associated anionic sites in the glomerular basement membrane were studied in rats 8 months after induction of diabetes by <span class="chemical">streptozotocin</span> and in age - adn sex - matched control rats , employing the cationic dye <span class="chemical">cuprolinic blue</span> . 