( ( ( ( ( Some isotopes ) , ) ( called radioisotopes ) ) , ) ( ( are ( ( ( unstable and ) emit ) radiation ) ) . ) )
(ROOT (S (NP (NP (DT Some) (NNS isotopes)) (, ,) (VP (VBN called) (NP (NNS radioisotopes))) (, ,)) (VP (VBP are) (NP (ADJP (JJ unstable) (CC and) (JJ emit)) (NN radiation))) (. .)))
Some isotopes, called radioisotopes, are unstable and emit radiation.
(ROOT (S (NP (DT A) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NNS radioisotopes)) (VP (VBZ is) (NP (NP (DT an) (NN isotope)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (ADJP (JJ radioactive))))))) (. .)))