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: Elevated atherosclerotic parameters , such as serum calcium , total cholesterol and low - density lipoprotein concentration were obtained in atherosclerotic rats .
### Output Text:
Elevated atherosclerotic parameters , such as serum <span class="chemical">calcium</span> , total <span class="chemical">cholesterol</span> and low - density lipoprotein concentration were obtained in atherosclerotic rats . 