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: These changes , related to ischaemic injury , explain the severe alterations in the structural integrity of the sarcolemma of cardiomyocytes and hence severe and irreversible injury induced by isoproterenol .
### Output Text:
These changes , related to ischaemic injury , explain the severe alterations in the structural integrity of the sarcolemma of cardiomyocytes and hence severe and irreversible injury induced by <span class="chemical">isoproterenol</span> . 