188 JOURNAL OF COSMETIC SCIENCE SIRTl ei:pression in human fibroblasts e:iposed to caloric restriction Control cells (A), cells culllued in medlll ctJnulining ollly 5tr-' of tlu glMc:ou of tlle control, for 14 II (a), � a,tu,red in IIUIIJa whll""t glMcou,for 14 II (CJ Studies of SIR T expression in different human and animal tissues (but not the skin) have shown that SIRTI expression is nuclear. Our studies on ex vivo skin involved comparative studies between frozen and fresh skin samples, and between skin samples at different ages. These studies showed that in fresh ex vivo skin samples, SIRTI exhibited a predominant nuclear staining throughout the epidennis. Some cytoplasmic staining was also seen. SIRTI expression in fresh human a vivo skin Comparative studies of skin samples from donors of different ages (30 to 55) did not reveal a significant age-related difference in SIRTI expression under a stress-free condition. SIRTI expression in ski donor irradia 1 Interestingly, when skin samples were irradiated with UVB (50-200 mJ/cm2), fresh skin samples exhibited a clear dose-dependent increase in SIR Tl nuclear expression, up to 100 mJ/cm2, which correlated with low tissue damage and low p53 expression, whereas high UVB doses yielded strong p53 expression. Amazingly, these results appeared more evident in young skin. No UVB (A) JOO mJ/cm (B) Conclusion These studies demonstrate that SIRTI is expressed in human skin and in cultured human keratinoctes, and fibroblasts. These studies also confirm the close relationship ofSIRTI with p53, stress, and cell aging they show that SIRTI expression correlates with its ability to protect human skin and is related to UV stress dosage. I Shore D, Squire M, Nasmyth KA, EMBOJ., 3(12), 2817-23, (1984) 2 Rine J, Strathem JN, Hicks JB, Herskowitz I, Genetics., 93(4), 877-901, (1979) 3 Gotta M, Strahl-Bolsinger S, Renauld H, Laroche T, Kennedy BK, Grunstein M, Gasser SM, EMBO J., 16(11), 3243-55, (1997) 4 Tissenbaum HA, Guarente L, Nature., 410(6815), 227-30, (2001) 5 Brachmann CB, Sherman JM, Devine SE, Cameron EE, Pillus L, Boeke ID, Genes Dev., 9(13), 2888- 902, (1995) 6 Dryden SC, Nahhas FA, Nowak JE, Goustin AS, Tainsky MA, Mo/ Cell Biol., 23(9), 3173-85, (2003) 7 Kaeberlein M, Andalis AA, Fink GR, Guarente L, Mo/ Cell Biol., 21(22) , 8056-66, (2002) 8 Masoro EJ, Mech Ageing Dev., 125(9), 591-4, (2004) 9 Cohen HY, Miller C, Bitterman KJ, Wall NR, Hekking B, Kessler B, Howitz KT, Gorospe M, de Cabo R, Science., 305(5682), 390-2, (2004) IO Wood JG, Rogina B, Lavu S, Howitz K, Helfand SL, Tatar M, Sinclaire D, Nature., 430(7000), 686-9, (2004)

2005 ANNUAL SCIENTIFIC MEETING 189 ABSORPTION AND EVAPORATION OF VOLATILE AND POTENTIALLY HAZARDOUS CHEMICALS FROM HUMAN SKIN Varsha D. Bhatt College of Pharmacy, University of Cincinnati, Cincinnati, OH Objective: To test an existing kinetic model for disposition of volatile compounds applied to human skin and to develop a predictive mathematical model based on diffusion theory that improves significantly on current predictions and extends the range of validity to pesticides and non-corrosive industrial solvents. Introduction: Estimation of penetration rates and systemic absorption of compounds following accidental or intentiooal application to the skin is an important aspect of risk assessment for cosmetic and personal care products, occupational exposures, environmental exposures, and chemical warfare agents. Previous work in our laboratory has shown that disposition of DEET and benzyl alcohol from human skin ex vivo is adequately described by first-order one and two comparbnent models. A simple diffusion model with a headspace compartment has also been developed. r.2 Presented below is an analysis of absorption and evaporation rates of the mosquito repellent DEET based on this model. Theory: A one-dimensional diffusion model is depicted in Figure 1. 1•2 Figure 1: Diffusion model for absorption and evaporation of DEET from human skin Diffusivity D SC 0 h/10 h J[ V h = headspace volume, M,.t = saturation dose (Cw•h/10) kevap = Evaporation mass transfer coefficient h2/D = diffusive time constant in SC, C = concentration in the SC, SC = stratum comeum Methods: Split thickness human cadaver skin was mounted on modified Franz diffusion cells connected to a customized volatiles trap using Tenaxill cartridges. Diffusion cells, filled with phosphate buffered saline (pH 7.4 with 0.02% sodium azide) were maintained at 37 ± 2 °C. Tissue integrity was ascertained using tritiated water. A 1 o/ow/w solution of 1 4 C-N, N-diethyl-3-methylbenzamide ( 14 C-DEET) was applied to the skin. An air pump attached to the system allowed air to be passed over the skin at a predetermined rate. Vapor was collected by means of a Tenax®absorbentcartridgeattached to the evaporation chamber. Samples were collected at 0.25, 0.75, 2, 4, 8, 12 and 24 hours post-dose. Evaporation and absorption of 14 C- DEET were measured at varying airflows (v =1 0-100 mllmin, n = 2-6 per airflow). Receptor solutions were analyzed by liquid scintillation counting (LSC). Tenax• cartridges were thermally desorbed and analyzed similarly. At the end of24 hours, the tissue was dissolved in Soluene-350R* and analyzed by LSC.