( ( a ( positive reaction ) ) ( ( was ( ( observed , ) ( negative ( in controls ) ) ) ) . ) )
(ROOT (S (NP (DT a) (JJ positive) (NN reaction)) (VP (VBD was) (ADJP (ADJP (JJ observed)) (, ,) (ADJP (JJ negative) (PP (IN in) (NP (NNS controls)))))) (. .)))
a positive reaction was observed, negative in controls.
(ROOT (S (S (VP (VBZ Is) (NP (NP (DT the) (NN heat)) (PP (IN of) (NP (NP (NN reaction)) (PP (IN for) (NP (DT an) (JJ endothermic) (NN reaction)))))))) (VP (VBZ is) (ADJP (JJ positive))) (. .)))