Recent advances in X-ray microanalysis in dermatology.

Electron microprobe and proton microprobe X-ray analysis can be used in several areas of dermatological research. With a proton probe, the distribution of trace elements in human hair can be determined. In contrast to sulfur, which is homogeneously distributed, calcium, iron, and zinc appear to be non-homogeneously distributed over the hair cross-section. Electron microprobe analysis on freeze-dried cryosections of guinea-pig and human epidermis shows a marked gradient of Na, P and K over the stratum granulosum. In sections of freeze-substituted human skin this gradient is less steep. This difference is likely to be due to a decrease in water content of the epidermis towards the stratum corneum. Electron microprobe analysis of the epidermis can, for analysis of trace elements, be complemented by the proton microprobe. Quantitative agreement between the two techniques can be obtained by the use of a standard. Proton microprobe analysis was used to determine the distribution of Ni or Cr in human epidermis exposed to nickel or chromate ions. Possible differences in water content between the stratum corneum of patients with atopic eczema and normal stratum corneum was investigated in skin freeze-substituted with Br-doped resin. No significant differences were observed. Proliferative reactions in the epidermis appear to be associated with increased levels of the elements P and K. Such changes were found in guinea-pig skin after exposure to sodium lauryl sulfate, and in plaques of skin from patients with psoriasis.