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: The effects of REM sleep deprivation ( REMD ) on apomorphine - induced aggressiveness and quipazine - induced head twitches in rats were determined .
### Output Text:
The effects of REM sleep deprivation ( REMD ) on <span class="chemical">apomorphine</span> - induced aggressiveness and <span class="chemical">quipazine</span> - induced head twitches in rats were determined . 