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: Methamphetamine ( METH ) damages dopamine ( DA ) nerve endings by a process that has been linked to microglial activation but the signaling pathways that mediate this response have not yet been delineated .
### Output Text:
<span class="chemical">Methamphetamine</span> ( <span class="chemical">METH</span> ) damages <span class="chemical">dopamine</span> ( <span class="chemical">DA</span> ) nerve endings by a process that has been linked to microglial activation but the signaling pathways that mediate this response have not yet been delineated . 