8500
Since DNA methylation is regulated by DNA methyltransferases and methyl cytosine - binding proteins , this study assessed the extent to which developmental Pb exposure might affect expression of these proteins in the hippocampus .
 Chemical: methyl cytosine; Chemical: Pb
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: methyl cytosine, Pb 
Answer:
 Chemical: methyl cytosine; Chemical: Pb