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: Immuno / histochemistry and electron microscopy were carried out on the offspring cerebellum , and levels of malondialdehyde and superoxide dismutase were determined .
### Output Text:
Immuno / histochemistry and electron microscopy were carried out on the offspring cerebellum , and levels of <span class="chemical">malondialdehyde</span> and <span class="chemical">superoxide</span> dismutase were determined . 