Cartilage and mineralized bone in a developing mouse legs at various stages in development. Mice lacking acetylcholinesterase (A-) or butryrylcholinesterase (B-) or both were compared to wild-type mice. Blue color indicates cartilage; red indicates mineralized bone. Figure 2 from Spieker et al., Endochondral Ossification Is Accelerated in Cholinesterase-Deficient Mice and in Avian Mesenchymal Micromass Cultures. PLoS ONE 12, e0170252 (2017).