Non-specific Alkaline Phosphatase Activity of Evaginating Epithelia

NON-SPECIFIC alkaline phosphatase activity has been demonstrated in the developing central nervous system, eye, lung and the allantois of the human embryo by Rossi et al. 1 , in the thyroid of the rat by McAlpine 2 , in the central nervous system, eye, ear and other sites in the chick embryo by Moog 3 and also in the pituitary and thyroid by Kaneko 4 . All the structures which show a high level of activity of this type develop by a process of evagination from an epithelium, and it has been suggested that alkaline phosphatase activity may be found in all epithelial evaginations during organogenesis 5 . No special examination of the association between phosphatase activity and evagination has been carried out, however. Forty-two chick embryos of known incubation time which formed a graded series from 30 h to 6 days were fixed in 70 per cent ethyl alcohol at 20° C. This method of fixation was found to be the most satisfactory and convenient. Whole embryos were embedded in paraffin wax and serial sections cut at 10µ. Alkaline phosphatase activity was demonstrated by means of an azo-dye method as described by Pearse 6 . The incubation period was 1 h.