3915
Frog type I ( Ft I ) and frog type II ( Ft II ) slowly adapting ( SA ) units produced spikes only at the indentation phase , and the threshold response phase ( TRP ) , i . e . . the phase of the first spike was for ca .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 None