SUMMARY
Background/PurposeThe inorganic metal oxide sunscreens titanium dioxide and zinc oxide have been considered to protect against sunburning ultraviolet radiation by physically reflecting/scattering the incident photons and thus protecting the skin. Earlier publications suggested, however, that the primary action of UV protection by these sunscreen agents is through absorption and not by reflection. The purpose of this work was to quantitate the contributions of each of these modes of action to the protection provided by inorganic UV sunscreen filters.
Solar protection is an important public health issue because solar UV exposure can cause acute and chronic damage to the skin. Seeking shade is a convenient and commonly practiced sun avoidance measure. Shade works by physically shielding the skin from direct UV rays; however UV rays can also reach the skin from other angles. It is not clear how protective the widely-used shade structures like umbrellas and walls are under actual use conditions. In this study, a sky view model was applied to systematically assess the influence of different factors to umbrellas and walls, including the transmission of the shade materials, the reflectivity of the ground or the wall, diffused UV to total UV irradiance ratios, shade geometry, a person's positions and orientations in the shade. We measured the sunburn protection factor (SPF) with a calibrated UV meter at different positions in the shades of an umbrella at different times of the day and compared the measurement results with the modeling. We found that shade structures like umbrellas and walls are more effective when the ratios of diffused UV to total UV irradiance are smaller (mid-day). The effectiveness increases with more coverage, less surface reflectance, and more centralized positions in the shade. The SPF value for a typical umbrella is probably between 3 and 7 in real-life. The low sun protection level offered by a typical shade highlights the importance of educating the public about how to properly protect the skin from the sun and the importance of applying a combination of sun protection measures during extended sun exposures.
The regulation of the pH is an important element in various biological functions. The pH distribution of the stratum corneum (SC) is considered as the gradient decreasing along surface in general while precise SC pH distribution and its dynamic changes under different environmental conditions remain to be clarified. The purpose of this study is to produce a transgenic mouse as a tool to visualize the intact SC pH in vivo. We generated a ratiometric pH-biosensor with pH-sensitive fluorescent protein, Venus H148G fused with pH-insensitive protein, mCherry (Venus H148G-mCherry), expressed specifically in the uppermost layer of stratum granulosum (SG1) using knock-in construct of SASPase gene by modified CRISPR/Cas9 system. Noninvasive confocal microscopic analysis of SC pH in living Venus H148G-mCherry mouse ear skin observed with dry objective demonstrated that upper SC is neutral compared to middle SC. Immersion of water onto SC surface enabled highresolution deeper range SC pH imaging and revealed that the SC and SG1 layer are divided into three zones with distinct pH properties rather than gradual changes across the layers. Namely, the SG1 was neutral, the middle SC was acidic, and neutral pH was again observed in the upper SC. Analysis of the 3D pH distribution of whole SC showed that the upper neutral SC zone distributed unevenly by differentiated units, and the acidic middle SC was wellmaintained. When ear skin was exposed to phosphate buffers with various pH (pH5.4, 6.6 and 7.4) by topical application, the pH of upper SC dynamically changed according to the pH applied, while the middle SC maintained its acidic pH. These findings indicated that the SC is a highly organized tissue with tightly-regulated pH layers having the distinct functions, and that the 3D in vivo pH imaging mice will provide a valuable tool to dissect the homeostatic mechanisms of SC by pH regulation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.