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: In the present work we assessed the effect of treatment of rats with gum Arabic on acute renal failure induced by gentamicin ( GM ) nephrotoxicity .
### Output Text:
In the present work we assessed the effect of treatment of rats with <span class="chemical">gum Arabic</span> on acute renal failure induced by <span class="chemical">gentamicin</span> ( <span class="chemical">GM</span> ) nephrotoxicity . 