SKIN MORPHOLOGY AND WRINKLE FORMATION 301 Figure 3. Measurement of wrinkles on skin impressions of the backs of hairless mice by image analysis. (A) Representative shadow image and (B) binary image obtained by extracting shadowed areas at a fixed gray level. 3 0 2. .c_ .=_ 1 o 0 2 2 4 6 8 10 Weeks of UVB Irradiation Figure 4. Effects of temporary artificial groove on wrinkle formation (original direction: at right angle to the midline) using the back skin of hairless mice. Closed circles: UV irradiation after production of temporary wrinkle. Open circles: UV-B irradiation only. Closed triangles: production of temporary wrinkle after UV-B irradiation. Open squares: production of temporary wrinkle without UV-B irradiation. Closed squares: no treatment. Error bars represent one standard deviation about the mean. permanent wrinkles. The differences are further illustrated in Figures 6 and 7, in which the ten-weeks macro-photographs of animals and skin impressions of all groups are compared. As shown, artificial skin wrinkling parallel to the midline was only induced by UV-B irradiation immediately after production of an artificial temporary groove. The degree ratios of wrinkling calculated by image analysis are shown in Table I. In the groups treated by UV-B irradiation after production of the temporary groove, by pro- duction of the temporary groove after UV-B irradiation, and by UV-B irradiation only, original wrinkling was significantly increased compared with age-matched controls and the group in which only the temporary groove was produced. In the groups treated by U¾-B irradiation after production of the temporary groove and in those in which the

302 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS •' 3 E o 2 2 4 6 8 10 Weeks of UVB Irradiation Figure 5. Effects of temporary artificial groove production on wrinkle formation (artificial direction: parallel to the midline) using the back skin of hairless mice. Closed circles: UV-B irradiation after pro- duction of temporary wrinkles. Open circles: UV-B irradiation only. Closed triangles: production of tem- porary wrinkles after UV-B irradiation. Open squares: production of temporary wrinkles without UV-B irradiation. Closed squares: no treatment. Error bars represent one standard deviation about the mean. :. A' B :" C ' Figure 6. Photographs of mouse skin after ten weeks. (A) UV-B irradiation immediately after production of the artificial groove parallel to the midline. (B) Production of the artificial groove parallel to the midline immediately after UV-B irradiation. (C) Only the artificial groove was produced without UV-B irradiation. temporary groove was produced after UV-B irradiation, original wrinkling was slightly but significantly decreased compared with the UV-B irradiation-only group. There were no differences in original wrinkling in the group treated only by production of the temporary groove compared with age-matched controls. In the groups treated by UV-B irradiation after production of the temporary groove, artificial wrinkling was signifi-