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: Although evidences of mitochondrial abnormalities were found in previously published studies , our results do not suggest that the FRs , generated during the acute phase , determined important abnormalities in mtDNA , in expression of CCO - I , and in CCO activity .
### Output Text:
Although evidences of mitochondrial abnormalities were found in previously published studies , our results do not suggest that the FRs , generated during the acute phase , determined important abnormalities in mtDNA , in expression of CCO - I , and in CCO activity . 