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: These results indicate that early changes in glutamate transport may be related to the development of vacuous chewing movements in rats .
### Output Text:
These results indicate that early changes in <span class="chemical">glutamate</span> transport may be related to the development of vacuous chewing movements in rats . 