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Scanning Electron Microscopy

Abstract

The basic function of provide a barrier which the epidermis is will separate the body compartment from the environment thus protecting the organism from excessive loss of water and to hinder the entrance of noxious agents. A continuous renewal of the actual barrier makes it possible to fulfill these requirements. Using particle probe analysis, electron microprobe (EMP) and proton microprobe (PMP) analysis we have demonstrated the feasibility of these techniques in the study of skin physiology. The results reported here have been obtained on quench frozen skin specimens inertly prepared by cryotechniques to produce freeze-dried sections presenting cross sections of the skin. The distribution of Na and K is compatible with the idea that the Na/K pump of the cell membranes is dysfunctional above the basal cell layer. The phosphorus distribution over the epidermal cross section coincides with a previously shown phospholipid distribution. S and mass distributions correspond to the results of the keratin synthesis of the epidermis. Calcium displays a profile over the epidermis which is compatible with recent data obtained on the calcium dependence of the differentiation of epidermal cells in culture. Also this distribution corresponds to recent data obtained by histochemical methods at transmission electron microscope resolution. Zn and Fe have been shown to reside mainly in the basal cell layer of the normal epidermis but are found in high amounts in the outer cell layers of the epidermis in hyperproliferative paralesional psoriasis. The penetration of Ni and Cr (Cr2O72-) through human epidermis was studied in vitro and it was found necessary to employ the PMP for the analysis of these substances due to the low amounts present ( < 100 ppm). It appears that chromate penetrates more readily than nickel at neutral pH.

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