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Oral supplementation with collagen hydrolysate (CH) has been shown to improve the condition of the skin in humans and experimental animals. Several hydroxyproline-containing oligo-peptides were previously detected in human peripheral blood after the ingestion of CH, and the two dipeptides, prolyl-hydroxyproline (PO) and hydroxyprolyl-glycine (OG), have been proposed to have beneficial effects on human health. When HR-1 hairless mice were fed a HR-AD diet, which lacked magnesium and zinc, transepidermal water loss (TEWL) increased and water content of stratum corneum decreased. In the present study, we investigated the effects of dietary PO and OG on skin barrier dysfunction in HR-1 hairless mice. Mice were fed a HR-AD diet with or without PO (0.15%) and OG (0.15%) for 35 consecutive days. The administration of PO and OG significantly decreased TEWL, and significantly increased water content of stratum corneum. A DNA microarray analysis of the dorsal skin revealed differences in gene expression between the group administered PO and OG and the control group. We also identified muscle-related Gene Ontology as a result of analyzing the up-regulated genes. These results suggested that the administration of PO and OG improved skin barrier dysfunction and altered muscle-related gene expression.

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A method has been developed for the determination of silicon by electrothermal atomic absorption spectrometry using platinum as a chemical modifier. The sensitivity for the determination was improved by a factor of 15 in the presence of platinum as compared with that in the absence of a chemical modifier. The calibration curve for silicon was linear over the range 0-0.8 ng, and the detection limit was calculated (as 3a of the blank absorbance) to be 8 pg. The concentration of silicon in the electrolyte solutions of fuel cells was determined using the platinum modifier and Zeeman-effect background correction, with 0.1 mol 1-' of lithium chloride present as a matrix matching reagent.

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