. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Fig. 3. Electron micrograph showing fibrils of keratin appearing in a cortical cell in the upper bulb region (longitudinal section). Magnification Fig. 4. A cross-section at high magnification of a fibril showing the component keratin filaments (light) on a dark ground—the cystine-rich matrix. Magnification 150,000. without any evidence of a non-fibrous precursor. Filaments can be detected electron microscopically in the bulb cells at a level below which the bire- fringence is strong enough to be demonstr
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Fig. 3. Electron micrograph showing fibrils of keratin appearing in a cortical cell in the upper bulb region (longitudinal section). Magnification Fig. 4. A cross-section at high magnification of a fibril showing the component keratin filaments (light) on a dark ground—the cystine-rich matrix. Magnification 150,000. without any evidence of a non-fibrous precursor. Filaments can be detected electron microscopically in the bulb cells at a level below which the bire- fringence is strong enough to be demonstrated. Such filaments are oriented parallel to the fibre from their first appearance. These observations clearly show that the keratin is not synthesised as an amorphous precursor which is converted into a fibrous form by its passage through the narrow neck of the follicle. In the upper bulb, where the rise in birefringence takes place, the cells rapidly fill with filaments (fig. 3) and condense to form the rather definite structures recognisable in the light microscope as fibrils ( /< in diameter). At this level there is sufficient material present to enable an x-ray diffraction photo- graph to be made and a typical a-type pattern results (fig. 1). There is therefore little doubt that the long fine filaments are the structures responsible for this x-ray pattern which is of such interest to crystal- lographers (2). Cross-sections of the condensed fibrils (fig. 4), show that the filaments are embedded in a material which, after osmium fixation, has a greater electron scattering power than the filaments them- selves, the filament sections appear light on a dark ground. The most probable interpretation is that the osmium is here acting as a specific stain for cystine (cysteine) and that the S sites are concentrated in the interfilamentous regions. Since chemical an- alysis of dissolved hair (1) shows the presence of a fibrous component (a) with a low S content and
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