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: Taken together , the present study demonstrates that the central injection of U - II at doses of 1 - 10 , 000 ng / mouse induces anxiogenic - and depressant - like effects in mouse .
### Output Text:
Taken together , the present study demonstrates that the central injection of <span class="chemical">U - II</span> at doses of 1 - 10 , 000 ng / mouse induces anxiogenic - and depressant - like effects in mouse . 