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: Interestingly , clentiazem , infused alone , resulted in decreased adrenergic receptor densities in the left ventricle .
### Output Text:
Interestingly , <span class="chemical">clentiazem</span> , infused alone , resulted in decreased adrenergic receptor densities in the left ventricle . 