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: We investigated the effects of moderate and large doses of prednisolone on muscle function and pharmacology , and their relationship to changes in muscle size and acetylcholine receptor ( AChR ) expression .
### Output Text:
We investigated the effects of moderate and large doses of <span class="chemical">prednisolone</span> on muscle function and pharmacology , and their relationship to changes in muscle size and <span class="chemical">acetylcholine</span> receptor ( AChR ) expression . 