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: Regulation of signal transducer and activator of transcription 3 and apoptotic pathways by betaine attenuates isoproterenol - induced acute myocardial injury in rats .
### Output Text:
Regulation of signal transducer and activator of transcription 3 and apoptotic pathways by <span class="chemical">betaine</span> attenuates <span class="chemical">isoproterenol</span> - induced acute myocardial injury in rats . 