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: L - NAME reduced gentamicin - induced hearing loss in the high - frequency range , but gave no protection in the middle or low frequencies .
### Output Text:
<span class="chemical">L - NAME</span> reduced <span class="chemical">gentamicin</span> - induced hearing loss in the high - frequency range , but gave no protection in the middle or low frequencies . 