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: Male Sprague - Dawley rats , uninephrectomized three weeks before , received daily injections of subcutaneous AMNS ( 1 mg / 100 g body wt ) and intravenous PS ( 2 separated doses of 2 . 5 mg / 100 g body wt ) for four days .
### Output Text:
Male Sprague - Dawley rats , uninephrectomized three weeks before , received daily injections of subcutaneous <span class="chemical">AMNS</span> ( 1 mg / 100 g body wt ) and intravenous <span class="chemical">PS</span> ( 2 separated doses of 2 . 5 mg / 100 g body wt ) for four days . 