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: Typical S - T / T changes occurred in the insulin - group but in none of the propranolol - insulin group .
### Output Text:
Typical S - T / T changes occurred in the insulin - group but in none of the <span class="chemical">propranolol</span> - insulin group . 