高田 定樹

Background/purpose Detailed information on the mechanism by which surfactants affect the skin barrier function is still scarce. We investigated the contribution of protein denaturation to the effect of surfactants on barrier function. Methods The Transmission Index method, which evaluates the actual effect of surfactants on barrier function, was combined with a microplate assay measuring protein denaturation activity. The correlation between the TI value and the reciprocal of the median effect concentration (1/EC50) was analyzed for 19 surfactants. The contribution of protein denaturation to the effect of surfactants was discussed based on the 1/EC50 per TI value. Results A few surfactants showed high TI value. Nonionic surfactants had no effect. The EC50 varied without certain trend. For amino acid-based surfactants, there was a gradual inverse correlation between the TI value and the 1/EC50. Conclusion The difference in the alkyl structure and the ion source affected the skin barrier function. Protein denaturing activity of the surfactant was not a critical factor. This suggests that the effect on intercellular lipids was the major factor. However, the magnitude of the contribution of protein denaturation activity varied depending on the surfactant, suggesting that each surfactant has a different mechanism of influence on skin barrier function.

Anionic surfactants are commonly used as detergents and emulsifiers. However, these compounds are potent skin irritants. In this study, we evaluated the effect of the alkyl structure of anionic surfactants on the skin barrier function using the transmission index (TI) method. The TI method is used to measure the skin penetration rate of drugs. Sodium soaps of C18 fatty acids with different structures were evaluated. Sodium laurate was used as the control. In addition, microscopic observations of the skin tissue treated with different soaps and controls were performed to study the mechanism of skin permeation. Results showed that unsaturated fatty acid soaps exerted the most potent effect on the skin barrier function and saturated fatty acid soaps exerted the least effect; saturated branched fatty acid soap had an intermediate effect. This could be attributed to the differences in the melting points of different fatty acids. In addition, unlike lauric acid soap, C18 fatty acid soap did not cause morphological changes in the skin tissue. Thus, differences in the alkyl structure of fatty acids resulted in differences in the effect of fatty acid soaps on the skin barrier function. The mechanism was presumed to be an effect on intercellular lipids.

Elderly people show a decline in the ability to decode facial expressions, but also experience age-related facial structure changes that may render their facial expressions harder to decode. However, to date there is no empirical evidence to support the latter mechanism. The objective of this study was to assess the effects of age on facial morphology at rest and during smiling, in younger (n = 100; age range, 18-32 years) and older (n = 30; age range, 55-65 years) Japanese women. Three-dimensional images of each subject's face at rest and during smiling were obtained and wire mesh fitting was performed on each image to quantify the facial surface morphology. The mean node coordinates in each facial posture were compared between the groups using t-tests. Further, the node coordinates of the fitted mesh were entered into a principal component analysis (PCA) and a multifactor analysis of variance (MANOVA) to examine the direct interactions of aging and facial postures on the 3D facial morphology. The results indicated that there were significant age-related 3D facial changes in facial expression generation and the transition from resting to smiling produced a smaller amount of soft tissue movement in the older group than in the younger group. Further, 185 surface configuration variables were extracted and the variables were used to create four discriminant functions: the age-group discrimination for each facial expression, and the facial expression discrimination for each age group. For facial expression discrimination, the older group showed 80% accuracy with 2 of 66 significant variables, whereas the younger group showed 99% accuracy with 15 of 144 significant variables. These results indicate that in both facial expressions, the facial morphology was distinctly different in the younger and older subjects, and that in the older group, the facial morphology during smiling could not be as easily discriminated from the morphology at rest as in the younger group. These results may help to explain one aspect of the communication dysfunction observed in older people.

Anionic surfactants are often used for cleaning and pharmaceutical purposes because of their strong surfactancy and foaming property. However, they are rarely ingested orally, the skin is a part of the human body most affected by surfactants. Barrier function of the skin is very strong, but the anionic surfactants can cause serious damages to it. Recently, amino acid-based surfactants have attracted attention as a safer option owing to their biocompatibility. Cytotoxicity examinations revealed that the amino acid-based surfactants are superior to sulfate-based surfactants. However, a systematical and comprehensive study related to the effect of these surfactants on skin barrier function has not yet been reported. In this work, skin permeation test using the skin of hairless mice and HPLC method is carried out. The material transmission speed through skin in a steady state was different between each surfactant treatment. We performed a comprehensive analysis of the effect of surfactants on skin barrier function and defined Transmission Index as an index for the degree of effect of surfactants. Glutamate series amino acid-based surfactant were effective to Transmission Index and we guessed the cause was due to adsorption. Based on the finding this study, we suggest using adsorptive property as a measure to the effect on the skin barrier function.

In most cases, a meal cannot be finished with a single bite and sip. During eating and drinking, consumers receive dynamic food perceptions from sensory attributes in foods. Thus, we performed multi-sip time-intensity (TI) evaluation of sensory attribute. In each of ten trials, the participant evaluated continuously the intensity of retronasal aroma for 60 s after swallowing oolong tea. We compared the TI parameters (I-max: maximum intensity, T-max: time point at which intensity reached the maximum value, AUC: area under the TI curve, D-plateau: duration between the first and last time points with values exceeding 90% of the maximum intensity, R-inc: rate of intensity increase between the first time points with values exceeding 5% and 90% of the maximum intensity, and R-dec: rate of intensity decrease between the last time points with values exceeding 5% and 90% of the maximum intensity) and TI curves among the ten trials, and approximated each TI curve with an exponential model. Some TI parameters (I-max, T-max, AUC, and R-inc) differed significantly between the first and subsequent trials. The TI curve was significantly lower in the first trial than in the subsequent trials, and TI curve during the time from starting the evaluation to reaching maximum intensity was significantly lower in the second trial than in the subsequent trials. The time constant of the fitted exponential function revealed that the decay of retronasal aroma intensity was slightly faster in the second through fourth trials than in the first and the fifth through tenth trials. These results indicate that olfaction might be more perceptive while consumers sip a cup of the beverage.