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 results demonstrate that changes in NPY expression , including expression in the granule cells and mossy fibres and the loss of vulnerable NPY neurons , are present in the PILO model of TLE .
### Output Text:
The results demonstrate that changes in NPY expression , including expression in the granule cells and mossy fibres and the loss of vulnerable NPY neurons , are present in the <span class="chemical">PILO</span> model of TLE . 