在前缀和后缀之间提取字符串

I have these columns:

我有这些专栏:

                 text.NANA text.22 text.32
1    Female RNDM_MXN95.tif      No      NA
12     Male RNDM_QOS38.tif      No      NA
13  Female  RNDM_WQW90.tif      No      NA
14    Male  RNDM_BKD94.tif      No      NA
15    Male  RNDM_LGD67.tif      No      NA
16   Female RNDM_AFP45.tif      No      NA