HIGH-SPF SUNSCREENS 295 ACKNOWLEDGMENTS This study was funded by the Department of Health. The views expressed are those of the authors and not necessarily those of the Department of Health. REFERENCES (1) COLIPA Sun Protection Factor Method, European Cosmetic Toiletry and Perfumery Association (COLIPA), Brussels, Belgium, October 1994. (2) Department of Health and Human Services, FDA, USA, Sunscreen drug products for over the counter use: Tentative final monograph: proposed rule. Federal Register, 58(90), 28194-28302 (1993). (3) J. Ferguson, "European Guidelines (COLIPA) for Evaluation of Sun Protection Factors," in Sunscreens: Development, Evaluation, and Regulatory Aspects, 2nd ed., N.J. Lowe, N. A. Shaath, and M. A. Pathak, Eds. (Marcel Dekker, New York, 1997), pp. 513-525. (4) B. L. Diffey, "Indices of Protection From In Vitro Assay of Sunscreens," in Sunscreens: Development, Evaluation, and Regulatory Aspects, 2nd ed., N.J. Lowe, N. A. Shaath, and M. A. Pathak, Eds. (Marcel Dekker, New York, 1997), pp. 589-600. (5) B. L. Diffey and J. Robson, A new substrate to measure sunscreen protection factors throughout the ultraviolet spectrum, J. Soc. Cosmet. Chem., 40, 127-133 (1989). (6) H. Schaefer and T. E. Redelmeier, Skin Barrier: Principles of Percutaneous Absorption (Karger, Basel, 1996), p. 133. (7) A. F. McKinlay and B. L. Diffey, "A Reference Action Spectrum for Ultraviolet-Induced Erythema in Human Skin," in Human Exposure to Ultraviolet Radiation: Risks and Regulations, W. F. Passchief and B. F. M. Bosnjakovic, Eds. (Elsevier, Amsterdam, 1987), pp. 83-87. (8) J. L. Robb, L. A. Simpson, and D. F. Tunstall, Scattering and absorption of UV radiation by sunscreens containing fine particles and pigmentary titanium dioxide. D.C.I. Mag., 32-40 (March 1994). (9) M. W. Anderson, J.P. Hewitt, and S. R. Spruce, "Broad-Spectrum Physical Sunscreens: Titanium Dioxide and Zinc Oxide," in Sunscreens: Development, Evaluation, and Regulatory Aspects, 2nd ed., N.J. Lowe, N. A. Shaath, and M. A. Pathak, Eds. (Marcel Dekker, New York, 1997), pp. 353-397. (10) M.A. Pathak, "Photoprotection Against Harmful Effects of Solar UVB and UVA Radiation: An Update," in Sunscreens: Development, Evaluation, and Regulatory Aspects, 2nd ed., N.J. Lowe, N.A. Shaath, and M. A. Pathak, Eds. (Marcel Dekker, New York, 1997), pp. 59-79. (11) R. M. Sayre and P. P. Agin, A method for the determination of UVA protection for normal skin. J. Am. Acad. Dermatol., 23, 429-440 (1990).

j. Soc. Cosmet. Chem., 48, 297-306 (November/December 1997) Skin morpholoDy at the time of UV irradiation is important for wrinkle formation YOSHINORI TAKEMA, AYUMI NISHIJIMA, HIROYUKI OHSU, TSUTOMU FUJIMURA, and MICHIHIRO HATTORI, Biological Science Laboratories, Kao Corporation, Tochigi 321-34, Japan. Accepted for publication December 1, 1997, Synopsis Hairless mice (HR/ICR) were irradiated chronically with suberythemal doses of UV-B radiation (ultraviolet radiation in wavelength 290-320 nm) immediately before and after production, with cyanoacrylate resin, of an artificial temporary groove parallel to the midline, which is an unusual direction for wrinkle formation. Data for UV radiation-exposed skin beibre or after production of an artificial groove and in chronological age-matched control mice or mice treated only by production of an artificial temporary groove were compared. Visible signs of artificial wrinkling were present after approximately six weeks of UV-B irra- diation and were very apparent after ten weeks of irradiation. From image analysis of skin impressions after ten weeks, artificial wrinkling in skin treated by UV-B irradiation after production of an artificial groove was significantly increased compared with skin in which an artificial groove was produced after UV-B irradiation. These results indicated that both an artificial temporary groove in the skin and UV-B irradiation immediately after production of the temporary groove are necessary for wrinkle formation in this mouse model, and suggested that the skin morphology at the time of UV-B irradiation is important for wrinkle formation. INTRODUCTION Wrinkles are the most common of all the signs of aging. There have been many histological studies of wrinkles in the skin of aged human subjects (1-3). Wrinkles of facial expression occurring on the facial skin are the most well developed and become permanent with chronological aging (4-7). The facial skin responds to every movement of the underlying muscles in smiling, frowning, and physical movement, and such movement produces temporary but repeated wrinkling of the same portion of the face. This repeated temporary wrinkling has been suggested to play an important role in the formation of permanent wrinkles. Hairless mice have been used extensively in studies of the formation of wrinkles after chronic UV-B irradiation (ultraviolet radiation in wave- length range 290-320 nm) (8-12). Kiss et aL (11) reported that there are other factors in addition to total cumulative UV-B dose that are important for the appearance of wrinkling in this model. Despite the suggestion that repeated temporary wrinkling 297