HAIR CURVATURE IN JAPANESE WOMEN 327 Figure 8. TEM images of the transverse section of a typical curved Japanese hair at the outer and inner regions of the curved shape. The hair sample was stained with erythrosine Bas described in the Experimental section to visualize macrofibrils in the hair fiber. In these images, macrofibrils and exocuticles are observed to be darker, but the darkest circular particles are melanin granules and the dark lines are wrinkles of the specimen. (a) A typical TEM image of the outer region of the curved shape. (b) A typical TEM image of the inner region of the curved shape. respectively. The macrofibril boundaries are not clear in the paracortical cells, whereas they are discrete in the orthocortical cells. The morphological difference in intermediate filaments (IFs) between ortho- and para­ cortical cells has been well investigated (6,7). IFs in paracortical cells are loosely aligned and approximately parallel to the fiber axis, while those in orrhocortical cells are ar­ ranged helically in each macrofibril. It has been proposed that this difference in IF alignment is one of the possible reasons for the curved fiber shape ( 13 ). An investigation of IF arrangements in the inner and outer regions of curved Japanese hair was, therefore, performed. Previously, Kajiura et al. (3) had tried to analyze the IF alignments of curved human hair fibers with a small-angle X-ray scattering (SAXS) method using a synchrotron mi­ crobeam X-ray at a synchrotron radiation facility, SPring-8, in Japan. The results of the microbeam SAXS suggested that the IFs were aligned relatively parallel to the fiber axis in the inner half of the curved human hair, while the IF arrangement was disordered in the outer half. In the SAXS method, it was not possible to determine whether the disordered IF structure was spiral, helical, or of another structural arrangement. We attempted to observe the IF arrangements by TEM technique in typical highly curved hair fibers (curl radius: ca. 0.6 cm) of Japanese women, stained with silver nitrate. Typical TEM images of the transverse and longitudinal sections of the outer and inner regions of the curved hair are shown in Figure 9. The white arrow in each longitudinal image indicates the approximate direction of the fiber axis (Figure 9c,d). The transverse section of the outer region (Figure 9a) shows concentric fingerprint-like patterns of IF alignment in each macrofibril, while that of the inner region (Figure 96) shows the ends of individual IFs as many dotted points with unclear macrofibril boundaries. The lon­ gitudinal section of a region from the outer half (Figure 9c) shows the IFs arranged in crossover patterns, while that of the inner half (Figure 9d) shows an IF arrangement pattern parallel to the fiber axis. These results strongly suggest either a spiral, helical, or twisted IF arrangement in the outer-fiber half, contrasting with parallel IF alignments in the inner-fiber region. In these two-dimensional TEM observations, however, it was

328 JOURNAL OF COSMETIC SCIENCE Figure 9. TEM images of the transverse anl longitudinal sections of a typical curved Japanese hair at the outer anl inner regions of the curved shape. The thin section of the hair sample was stained with silver nitrate (see Experimental). In these images, the matrix region between intermediate filaments (IFs) in macrofibrils is observed to be darker than the IFs and surrounding cell components. (a) A typical TEM image of the transverse section in the oLJter region of the curved hair. (b) A typical TEM image of the transverse section in the inner region of the curved hair. (c) A typical TEM image of the longitudinal section in the outer region of the curved hair. (d) A typical TEM image of the longitudinal section in the inner region of the curved hair. White arrows in the longiruclinal images indicate the approximate direction of the fiber axis. not possible to confirm clearly the three-dimensional IF structural arrangement. Three­ dimensional modeling of IF arrangement obtainable by electron tomography with in­ termediate voltage TEM would provide the necessary experimental evidence to confirm conclusively the three-dimensional IF structure, as has been shown for the IF structure of wool (6,7). The above-mentioned results of the IF structure in highly curved human hair fibers are consistent with the results of ortho- and paracortical cells in wool fiber and strongly