26018
To further delineate the mechanism of toxicity , endothelial cells were treated with NRTI of varying subclasses , and the level of reactive oxygen species ( ROS ) and mitochondrial function were assessed .
 Chemical: oxygen
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: oxygen