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: After the treatments and behavioral observation , glutamate uptake by segments of the brain was analyzed .
### Output Text:
After the treatments and behavioral observation , <span class="chemical">glutamate</span> uptake by segments of the brain was analyzed . 