Cytochemical localization of acid phosphatase in the hindbrain of dysraphic mice.

The cytochemical localization of acid phosphatase (AP) was studied at the ultrastructural level in the abnormal neuroepithelium of dysraphic loop-tail (Lp/Lp) embryos between 9 and 12 days of gestation. At 9-11 days, normal and abnormal embryos showed a positive AP reaction throughout the thickness of the neuroepithelium, i.e., in apical, intermediate, and basal zones, although many cells were unreactive. The reaction is sensitive to sodium fluoride and occurs in saccules and vesicles associated with the Golgi complex, as well as in vacuoles of varying size containing flocculent and particulate material. Gap-junctional vesicles, which are known to occur in increased numbers in abnormal brains, were AP-negative. By 12 days of gestation, the reaction in normal embryos was localized in the midventral marginal layer, where some cell processes were filled with reaction product; in abnormal embryos, these AP-positive processes were not observed. The results indicate that perturbations in lysosomal activity may not be fundamentally involved in the etiology of dysraphism in this mutant.