( This ( ( can ( occur ( ( ( when ( cells ( become ( overcrowded ( -LRB- ( ( density-dependent inhibition ) -RRB- ) ) ) ) ) ) or ) ( when ( they ( ( ( differentiate ( to ( ( carry out ) ( ( specific functions ) ( for ( the organism ) ) ) ) ) ) , ) ( as ( ( ( is ( ( the case ) ( for ( human ( heart ( muscle cells ) ) ) ) ) ) and ) neurons ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (MD can) (VP (VB occur) (SBAR (SBAR (WHADVP (WRB when)) (S (NP (NNS cells)) (VP (VBP become) (ADJP (ADJP (JJ overcrowded)) (PRN (-LRB- -LRB-) (NP (JJ density-dependent) (NN inhibition)) (-RRB- -RRB-)))))) (CC or) (SBAR (WHADVP (WRB when)) (S (NP (PRP they)) (VP (VB differentiate) (S (VP (TO to) (VP (VB carry) (PRT (RP out)) (NP (NP (JJ specific) (NNS functions)) (PP (IN for) (NP (DT the) (NN organism))))))) (, ,) (SBAR (IN as) (S (VP (VP (VBZ is) (NP (NP (DT the) (NN case)) (PP (IN for) (NP (JJ human) (NN heart) (NN muscle) (NNS cells))))) (CC and) (VP (VBZ neurons))))))))))) (. .)))
This can occur when cells become overcrowded (density-dependent inhibition) or when they differentiate to carry out specific functions for the organism, as is the case for human heart muscle cells and neurons.
(ROOT (S (PP (IN In) (NP (NNS humans))) (, ,) (NP (DT the) (NN heart)) (VP (VBZ is) (NP (DT the) (JJ first) (NN organ) (S (VP (TO to) (VP (VP (VB form)) (CC and) (VP (VB become) (ADJP (JJ functional)))))))) (. .)))