47.    Extrinsic hair shaft damage and restoration: implications for integral hair lipid, hair soluble protein and hair water content. 
Won-Soo Lee(1), Soo Young Jeon(1), Younduk Kim(2), Long Quan Pi, Ki Mu Lee(2), In Shik Cho(2), 1. Department of Dermatology and Institute of Hair and Cosmetic Medicine, Yonsei University, Wonju College of Medicine, Wonju, Korea, 2. Central Research Laboratory, Aekyung Co., Ltd. Daejeon, Korea.

Human hair shaft is constantly subjected to repeated environmental assaults, commonly termed "weathering", which aggravated from sunlight and exogenous chemical damages such as hair dye or permanent wave. These factors cause extrinsic hair shaft damage in addition to natural intrinsic hair shaft aging. Hair shaft damaged from acute extrinsic assault can be restored to predamaged state after sustantial period of time. On the hair surface, cells are covered with a thin lipid layer covalently bonded to hair proteins. These integral hair lipid plays a key role in the maintenance of hair integrity including hydrophobicity and stiffness, serving as "hair barrier". The hair shafts were treated with various kinds of extrinsic assaults including cosmetic hair dyeing, bleaching, permanent waving, natural sunlight and artificial ultraviolet damage. Scanning and transmission electron microscopy was performed to observe the ultrastructure of hair shaft and integral hair lipid was observed with specialized electron microscopic fixative designed by us. In addition, we extract and concentrate the whole and partial hair soluble protein, then performed electophoresis and western blot analysis of the hair soluble protein which is released after hair damage. Also, we measured the water content of hair shaft. From the above experimental procedure, it was discovered that the integral hair lipid were mainly distributed within the intercellular layers of cuticle cells and partly affected by extrinsic hair damages. Also the general architecture of the hair shaft were partly changed by various extrinsic damages and restored to predamaged state. Changes of hair soluble protein and hair shaft water content were also noted.