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: Monkeys with acute ( short - term ) MPTP exposure , rapid symptom onset and short symptom duration prior to initiation of levodopa therapy developed dyskinesia between 11 and 24 days of daily levodopa administration .
### Output Text:
Monkeys with acute ( short - term ) <span class="chemical">MPTP</span> exposure , rapid symptom onset and short symptom duration prior to initiation of <span class="chemical">levodopa</span> therapy developed dyskinesia between 11 and 24 days of daily <span class="chemical">levodopa</span> administration . 