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: Nine months of hyperprolactinemia produced a 50 % increase in DA concentrations in the ME over the control group .
### Output Text:
Nine months of hyperprolactinemia produced a 50 % increase in <span class="chemical">DA</span> concentrations in the ME over the control group . 