302 JOURNAL OF COSMETIC SCIENCE Figure 3. ASE-SEM images of transversely polished hair planes at no tilting angle (a) and at a tilting angle of 45 degrees (b) toward the primary electron beam. The arrow in each image shows the same region. Figure 4. A TEM image (a) of a transversely ultra-thin section of a hair fiber and an ASE-SEM image (b) of the adjacent hair plane. The arrows in each image show the same regions. suggests that CP and SP in ASE-SEM images correspond to melanin granules and the CMC, respectively (Figure 4). EFFECTS OF HAIR TREATMENTS ON ASE-SEM IMAGES The effects of various treatments of hair fibers on ASE-SEM images of the polished hair planes were then examined. When a hair fiber was treated with a mixture of CHC1 3 / CH 3 OH/water (v/v/v 18:9:1) for 24 hr at room temperature, SP but not CP disappeared in the ASE-SEM images (Figure Sb compare with the untreated control, Figure Sa). On

VISUALIZING HAIR LIPIDS BY ASE-SEM 303 Figure 5. ASE-SEM images of transversely polished hair planes following various treatments of the hair fibers. a: An untreated hair fiber (control). b: A hair fiber treated with CHCL/CH,OH/water 19:9:1 for 24 hr. c: A solvent-treated hair fiber incubated with a melting lipid mixture (squalene/oleyl olate/triolein/oleic acid {wt 10:30:10:50}) at 80°C for 24 hr (a solvent-treated hair corresponds to that treated with CHCI,/ CH,OH/water 19:9: 1 for 24 hr). d: A solvent-treated hair fiber incubated with melting triolein at 80°C for 24 hr. the other hand, when solvent-treated hair fibers were further incubated with a melting lipid mixture (squalene/oleyl olate!triolein/oleic acid [ wt 10:30: 10:50}, which is a model of hair lipids) for 24 hr at 80°C, SP reappeared while CP remained unchanged (Figure Sc). Images similar to that shown in Figure Sc were also obtained by incubation with other lipids that melt at 80°C, such as C 1 rC 18 fatty acids, myristyl myristate, oleyl oleate, and isopropyl palmitate (data not shown). In contrast, SP did not reappear following treatment with triolein (Figure Sd). The effects of chemical fixation of hair fibers on ASE-SEM images of the polished hair