1997
In contrast , silver ions increased NR uptake ( ca . 10 % ) in RBE4 cells after 1h , while a reduction in NR uptake was observed after 24h exposure at high concentrations ( 20 - 30 mu M ) .
 Chemical: silver
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: silver