The object of this proposal is to continue investigatng the effects of an electrical field on epiphyseal plate growth in order to determine the eventual feasibility of using electrical stimulation in the treatment of shortened extremities in children. The proposed investigation is designed (1) to determine the parameters of voltage and current required to produce maximum epiphyseal plate growth as measured by macrophotography, H3-thymidine uptake and metaphyseal tetracycline labeling in in vitro and in vivo models, (2) to determine the morphologic effects of electrical fields on chondroblasts in the various zones of the epiphyseal plate by quantitating changes in cytoplasmic components by means of point- counting analysis of electron micrographs, and (3) to determine some of the physiologic effects of electrical fields on epiphyseal plate chondroblasts by correlating mitochondrial calcium release wth oxygen tension and voltage gradient.