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: It could be inferred that gum Arabic treatment has induced a modest amelioration of some of the histological and biochemical indices of GM nephrotoxicity .
### Output Text:
It could be inferred that <span class="chemical">gum Arabic</span> treatment has induced a modest amelioration of some of the histological and biochemical indices of <span class="chemical">GM</span> nephrotoxicity . 