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: On the other hand , the pressor effects of Abbott - 53693 were similar in both groups of SHR , but the accompanying bradycardia was greater in SHR with chronic prazosin treatment than without such treatment .
### Output Text:
On the other hand , the pressor effects of <span class="chemical">Abbott - 53693</span> were similar in both groups of SHR , but the accompanying bradycardia was greater in SHR with chronic <span class="chemical">prazosin</span> treatment than without such treatment . 