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: This study was undertaken to ascertain whether the alterations of plasma lipoproteins found in nephrotic syndrome induced by puromycin aminonucleoside were due to nephrotic syndrome per se , or , at least in part , to the aminonucleoside .
### Output Text:
This study was undertaken to ascertain whether the alterations of plasma lipoproteins found in nephrotic syndrome induced by <span class="chemical">puromycin aminonucleoside</span> were due to nephrotic syndrome per se , or , at least in part , to the <span class="chemical">aminonucleoside</span> . 