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: PILO - injected animals exhibited NPY immunoreactivity in the region of the mossy fibre terminals , in the dentate gyrus inner molecular layer and , in a few cases , within presumed granule cells .
### Output Text:
<span class="chemical">PILO</span> - injected animals exhibited NPY immunoreactivity in the region of the mossy fibre terminals , in the dentate gyrus inner molecular layer and , in a few cases , within presumed granule cells . 