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: An experimental model of focal segmental glomerular sclerosis ( FSGS ) was developed in rats by the combined administration of puromycin - aminonucleoside ( AMNS ) and protamine sulfate ( PS ) .
### Output Text:
An experimental model of focal segmental glomerular sclerosis ( FSGS ) was developed in rats by the combined administration of <span class="chemical">puromycin - aminonucleoside</span> ( <span class="chemical">AMNS</span> ) and <span class="chemical">protamine sulfate</span> ( <span class="chemical">PS</span> ) . 