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: This shift in balance may contribute to increased bladder dysfunction in VIP ( - / - ) mice with bladder inflammation and altered neurochemical expression in micturition pathways .
### Output Text:
This shift in balance may contribute to increased bladder dysfunction in VIP ( - / - ) mice with bladder inflammation and altered neurochemical expression in micturition pathways . 