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 was also shown that both products of inducible NO synthase and neuronal NO synthase activation as well as bradykinin are involved in hyperalgesia produced by vincristine .
### Output Text:
It was also shown that both products of inducible <span class="chemical">NO</span> synthase and neuronal <span class="chemical">NO</span> synthase activation as well as <span class="chemical">bradykinin</span> are involved in hyperalgesia produced by <span class="chemical">vincristine</span> . 