162 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS solution has a significant influence on the adsorption properties. A comprehensive research program will be required to achieve a better understanding of the pH and other various forces that impact the substantivity. The analytical approach outlined in this paper has made it possible to measure the adsorption of N-lauroyl sarcosinate to live human skin without resorting to skin ex- tractions. This methodology is amenable to the study of a wide variety of compounds. ACKNOWLEDGMENTS The author thanks Dr. J. N. LePage for valuable discussions, reviews of the manuscript, and assistance with the experiments J. M. Beland for the synthesis of the perdeutero- lauroyl sarcosine K. E. Davis, Dr. J. Crudden, and M. T. DeGeorge for assistance with the experiments and R. R. Gaudette for the support of the project. REFERENCES (1) J. J. Crudden, B. J. Lambert, and R. W. Kohl, Applications of N-acyl sarcosine surfactants, Pro- ceedings--Ind•strial Applications of S•rfactants III, University of Salford, England, Sept. 16-18, 1991. (2) R. J. Hart, N-acyl sarcosinate surfactants, Cosmet. Toilerr., 94, 74-76 (1979). (3) M. F. Nelson, Jr. and D. Stewart, Jr., The adsorption of N-acyl sarcosines on various protein materials, J. Soc. Cosmet. Chem., 7, 122 (1956). (4) H. M. Klimisch and G. Chandra, Use of Fourier transform infrared spectroscopy with attenuated total reflectance for in vivo quantitation of polydimethylsiloxanes on human skin. J. Soc. Cosmet. Chem., 37, 73-87 (1986). (5) R. Samaritano, M. Hoshowski, and P. Walling, Substantivity of cosmetic ingredients on the skin by FTIR-ATR, Digilab FTS/IR Notes, No. 58 (1988). (6) Alperr, Keiser, and Szymanski, IR-Theory and Practice of lnfrared Spectroscopy (Plenum/Rosetta Edition, 1964, 1970).

j. Soc. Cosmet. Chem., 46, 163-173 (May/June 1995) The relationship between age-related changes in the physical properties and development of wrinkles in human facial skin YOSHINORI TAKEMA, YUKIKO YORIMOTO, and MICHIO KAWAI, Biological Science Laboratories, Tochigi (Y. T. ) and Cosmetic Science Laboratories, Kao Corporation, Tokyo (Y. Y., M.K. ), Japan. Received April 20, 1995. Synopsis We previously measured age-related changes in the elasticity of human skin and reported parameters of actinic and intrinsic aging [Y. Takema et al., Br. J. Dermatol., 131, 641-648 (1994)]. In this study, scoring of wrinkles was performed using photographs simultaneously with measurement of these parame- ters, and an association between these parameters and wrinkle formation was found. The wrinkle formation rate (slope of wrinkle scores vs chronological age) decreased in the following order: eye corner forehead cheek mouth corner. Calculated on a logarithmic basis, the relationship between the mean relative elasticity parameter Ur/Uf and the wrinkle formation rate was observed, but there was no such relationship with the absolute parameter Ue*. This finding suggested that the different susceptibilities of various facial regions to wrinkling was dependent on the parameter Ur/Uf. It is generally accepted that wrinkle formation is more marked in the face frequently exposed to the sun. However, in this study no relationship was confirmed between wrinkle formation rate and Ue*, a parameter reflecting the influence of exposure to the sun. Rather, a marked correlation was observed with Ur/Uf, a parameter reflecting intrinsic aging. These results suggest that another important UV-related factor is involved in addition to changes in physical properties in the progression of wrinkles. INTRODUCTION Morphological changes that accompany aging, such as wrinkles and skin laxity, are especially prominent in facial skin, and changes in the physical properties of skin play a major role in the development of these features. Wrinkles have been studied histo- logically (1-3) and clinically (4-6) by dermatologists, and quantitatively (7) by cosmetic scientists. There have been many studies of the physical properties of the skin (8-15). Recently, we reported age-related changes in the human face skin markedly exposed to sunlight using a commercially available in vivo instrument, and demonstrated that intrinsic aging and actinic aging can be monitored by assessing the relative parameter Ur/Uf and absolute parameter Ue*, respectively (16). Evaluation of changes in these properties is important to clarify the mechanisms of wrinkling. However, there have 163