Eriko Kawai

Skin surface electric potential as an indicator of skin condition: a new, non‐invasive method to evaluate epidermal condition

Abstract:  We previously demonstrated that the skin surface electric potential, which has been long recognized as a parameter of emotional or physiological state, is generated by epidermal keratinocytes and is strongly associated with the ion concentration gradient in the epidermis. Thus, at temperatures below the threshold of sweating, the potential provides a measure of the epidermal ion concentration gradient, which in turn is related to epidermal homeostasis and pathology. In the present study, we established a new, non‐invasive method to measure skin surface electric potential. In healthy skin, calcium ion was localized in the uppermost epidermis and the gradation disappeared by tape stripping. Skin surface potential was also disappeared by tape stripping. Moreover, environmental humidity affected the potential, whereas temporary hydration of the stratum corneum did not affect it. These results suggest that the skin surface electric potential may be an indicator of the pathophysiology of the living layer of epidermis, and thus may be useful as a new parameter to evaluate skin condition.

Quantitative analysis of exocytosis visualized by a video-enhanced light/fluorescence microscope reveals two distinct components of exocytosis in RBL-2H3 cells

Rat basophilic leukemia (RBL‐2H3) cells, which exhibit Ca2+‐dependent secretion of granules when stimulated with antigen or the Ca2+‐ionophore A23187, were observed under a video‐enhanced light/fluorescence microscope. Exocytotic events of individual granules were visualized in individual cells stimulated with antigen or A23187. Exocytosis of granules stimulated with A23187 showed two peaks in the time course. The earlier one was inhibited by selective inhibitors of protein kinase C (Ro31–8425, Ro31–8220, and chelerythrine) and the other was inhibited by an inhibitor of phosphatidate hydrolase, propranolol. Exocytosis by antigen stimulation, however, showed only one peak, which was inhibited by the selective inhibitors of protein kinase C, but not by propranolol. These results indicate that at least two distinct components of exocytosis exist in RBL2H3 cells.

Video-microscopy for analysis of molecular dynamics in cells.

Real-time analysis of molecular dynamics in living cells was studied by developed video-microscopes. Two new detective methods were reported, one is for analysis of ciliary movement and the other is the qualitative analysis of exocytosis of insulin-containing granules with a video-enhanced light/fluorescent microscope. For analysis of ciliary movement, glass beads were migrated in the flow. The migration speed parallel to the flow produced by ciliary beating was used as an index of the beating activity. When tracheal epithelium isolated from mouse was incubated with ambroxol, and expectorant known to activate ciliary beat frequency, the floating speeds of glass beads were changed with 1 min of incubation. The results suggest that the present method is useful not only for screening of expectorants but also for the study of molecular mechanisms underlying ciliary beat of tracheal epithelium. Visualization of the moment of the release of contents from insulin-containing granules was achieved using video-enhanced fluorescent microscopy in MIN6 cells of mouse insulinoma cell line. A fluorescent amino acridine dye, quinacrine, was found to be incorporated into low-pH secretory granules, including insulin, in the cells. The granules which incorporated quinacrine emitted a slightly blue-green fluorescence. Upon stimulation with glucose, release of the quinacrine fluorescence from granules were observed. The present method would be useful for quantitative analysis of secretion of insulin from MIN6 cells as well as pancreatic beta-cells.

Quantitative analysis of superoxide anion generation in living cells by using chemiluminescence video microscopy

Superoxide anions (O2-) generated by rabbit neutrophils were detected and quantified by a video microscope equipped with a photon-counting camera. One count obtained by this system was equivalent to 59 amol of O2-. Maximum O2- production was observed at 6-8 min after stimulation and was estimated as 1.9 fmol/min per cell on the average.

Skin surface electrical potential as an indicator of skin condition: observation of surfactant‐induced dry skin and middle‐aged skin

Abstract:  We previously reported that skin surface electrical potential might be a good parameter of skin pathophysiology. To examine the potential availability of skin surface electrical potential measurement for diagnostic purposes, we measured the change of the potential in surfactant‐induced dry skin and we compared the values of the potential in volunteers of different age groups. We also measured trans‐epidermal water loss (TEWL) in the same groups. The skin surface electrical potential was significantly increased after sodium dodecyl sulphate treatment, and the alteration was much more marked than that of TEWL. Further, a significant difference in skin surface electrical potential was observed between young‐ and middle‐aged volunteers, although there was no significant difference in TEWL between the two groups. These results suggest that skin surface electrical potential may be a good indicator of the pathophysiological state of the living layer of epidermis.