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: The effects on isoproterenol tachycardia were determined before and after atropine ( 0 . 04 mg / kg IV ) .
### Output Text:
The effects on <span class="chemical">isoproterenol</span> tachycardia were determined before and after <span class="chemical">atropine</span> ( 0 . 04 mg / kg IV ) . 