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: In isolated hearts , Iso induced a significantly greater increase in left ventricular ( LV ) pressure and maximal contraction ( + dP / dt ( max ) ) in the TGR than in the Sprague - Dawley ( SD ) rats .
### Output Text:
In isolated hearts , <span class="chemical">Iso</span> induced a significantly greater increase in left ventricular ( LV ) pressure and maximal contraction ( + dP / dt ( max ) ) in the TGR than in the Sprague - Dawley ( SD ) rats . 