[Show abstract][Hide abstract] ABSTRACT: The epidermal permeability barrier forms late in gestation, coincident with decreased lipid synthesis, increased lipid processing, and development of a mature, multi-layered stratum corneum. Prior studies have shown that changes in the epidermal Ca++ gradient in vivo regulate lamellar body secretion and lipid synthesis, and modulations in extracellular Ca++ in vitro also regulate keratinocyte differentiation. We asked here whether a Ca++ gradient forms in fetal epidermis in utero, and whether its emergence correlates with key developmental milestones of barrier formation and stratum corneum development. Using either ion precipitation or proton induced X-ray emission analysis of fetal mouse and rat skin, we showed that a Ca++ gradient is not present at gestational days 16-18, prior to barrier formation, and that a gradient forms coincident with the emergence of barrier competence (day 19, mouse; day 20, rat) prior to birth. These results are consistent with a role for Ca++ in the regulation of key metabolic events leading to barrier formation. Whether the calcium gradient is formed actively or passively remains to be determined.
[Show abstract][Hide abstract] ABSTRACT: Standard methods for the ultrastructural detection of lipase and sphingomyelinase activities in the skin result in considerable loss of structural preservation, often interfering with accurate delineation of enzyme localization in association with specific organelles. Moreover, poor preservation occurs, even after extensive aldehyde prefixation, owing to the prolonged incubation times needed to detect residual enzyme activity, which often require non-physiological conditions. A modified incubation protocol is described here, which uses microwave irradiation in conjunction with drastically shortened incubation times, resulting in both superior ultrastructural preservation and excellent localization in mammalian epidermis. This method should be useful generally not only for the study of lipase localization in skin, but also in conjunction with the cytochemical detection of a variety of enzymes in various types of tissue.
The Histochemical Journal 06/1997; 29(5):387-92. DOI:10.1023/A:1026438917856