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: RESULTS : STZ administration and castration markedly decreased both STL1 ( the short memory ) and STL2 ( the long memory ) in passive avoidance tests .
### Output Text:
RESULTS : <span class="chemical">STZ</span> administration and castration markedly decreased both STL1 ( the short memory ) and STL2 ( the long memory ) in passive avoidance tests . 