Hair Cuticle Research Articles

Degradation of Human Hair by Papain

Papain/bisulfite is shown to disintegrate the cuticle of human hair by dissolution of the endocuticle. Ethanol extraction removes cell membrane material, which is presumed to allow increased access of the enzyme and hence speed disintegration of the hair. In addition it has been shown that a thin layer of electron transparent material is also removed from the surface of the hair by hot ethanol extraction. It is suggested that this component of the fiber may be regarded as the epicuticle described previously. The origin and nature of this material is discussed.

The Use of Normal Incident Illumination in the Examination of Hair Cuticle

The Use of Normal Incident Illumination in the Examination of Hair Cuticle

A STUDY OF THE ULTRASTRUCTURAL LOCALIZATION OF HAIR KERATIN SYNTHESIS UTILIZING ELECTRON MICROSCOPIC AUTORADIOGRAPHY IN A MAGNETIC FIELD.

The sites of the incorporation of labeled cystine into keratinizing structures were studied in electron microscopic autoradiographs. The tracer used was cystine labeled with S(35) emitting long-range ionizing particles. During exposure for 1 to 2 months, according to our method of electron microscopic autoradiography, emulsion-coated specimens were exposed to a static magnetic field which appeared to result in a marked increase in the number of reacted silver grains. In young Swiss mice receiving intraperitoneal injections at 1, 3, and 6 hours before biopsy, conventional autoradiography demonstrated that S(35)-cystine was intensely localized in the keratogenous zone of anagen hair follicles, and that the radioactivity there increased in intensity progressively with time while the radioactivity in the hair bulb always remained very low. Our observations with electron microscopic autoradiography in a magnetic field appeared to indicate that at 3 and 6 hours after injection the S(35)-cystine was directly and specifically incorporated into tonofibrils in the hair cortex and into amorphous keratin granules of the hair cuticle layer, possibly without any particular concentration of this substance in the other cellular components. There seemed to be an appreciable concentration of cystine in tonofibrils of the cuticle of the inner root sheath. However, trichohyalin granules in the hair medulla and inner root sheath failed to show any evidence of cystine concentration. The improved sensitivity of the electron microscopic autoradiography with S(35)-cystine appeared to be partly due to the application of a static magnetic field. However, the reason for this could not be explained theoretically.

Electron microscope observations on hardening in the hair follicle

The early formation of prickles and tonofibrils is shown in the undifferentiated hair follicle cells. The indisputable presence of fibrillar material in cells of the inner root sheath prior to the appearance of trichohyalin makes doubtful Birbeck and Mercer's postulate of a fibrous transformation of the trichohyalin. Evidence is given that the fibrillar material of the cornified root sheath cells is tonofibrillar, the rest of the cornification substance being non-fibrillar and related in some way to trichohyalin, as the non-fibrillar material of the horny layer of skin seems to be related to keratohyalin. In the cortex the material is entirely fibrillar, and is again almost certainly tonofibrillar. Here little interfibrillar material occurs, and cortical development is probably a keratinization in the sense used by Astbury and Dickinson, and defined herein. The hardening of the hair cuticle takes place without the inclusion of electron microscopically observable fibrillar material, although such material, and prickles, are seen in the young cuticle cells. The persistence of prickles in the cuticles of the hair and the sheath shows that no slipping occurs between the cells despite the extreme positional changes they undergo during development.

The electron microscopy of the human hair follicle. III. The inner root sheath and trichohyaline.

1. The three cylinders of cells, each one cell thick, which together constitute the inner root sheath, arise from the peripheral portions of the undifferentiated matrix. These cells, like the hair cuticle, are stabilised by the spread of adhesive contacts between their plasma membranes which occurs in the mid-bulb and upper bulb of the hair follicle. 2. The characteristic intracellular product of all three cell layers is trichohyaline. This substance is formed in the first place as amorphous droplets which subsequently transform into a birefringent form. 3. This transformation, involving the formation of a birefringent product from an amorphous precursor, is in contrast to the formation in the cortex of keratin which originates in a fibrous form. 4. Trichohyaline appears first and transforms first in the cells of Henle which are nearest the outer sheath and the dermal supply vessels. This transformation occurs at the level of the neck of the follicle. Synthesis and transformation in the cells of Huxley and the sheath cuticle lag behind the similar events in the cells of Henle. The transformation does not begin until the lower prekeratinous zone in the Huxley and cuticle cells. 5. The amorpous-fibrous transformation occurs rapidly cell by cell and involves the conversion of all the trichohyaline droplets. In longitudinal sections the birefringent modification can be seen extending from the droplets in both directions parallel to the axis of the hair. In cross-sections the images of the transformed material are difficult to interpret. They may be seen as sections of corrugated sheets ( approximately 100 A thick) or condensed fibrils approximately 100 A in width. 6. At the same time that the trichohyaline transforms, the spacing between the cell membranes increases and a dark deposit appears centrally between them. This membrane complex, and the similar complex of the hair cuticle cells described in Part 2, may be specialised formations whose purpose is to hold the hardened cells together.

Age changes in head hair from birth to maturity. IV. Refractive indices and birefringence of the cuticle of hair of children.

Age changes in head hair from birth to maturity. IV. Refractive indices and birefringence of the cuticle of hair of children.

Resistant components of the cortex of animal hair.

THE possibility that there exists beneath the scaly layer or cuticle of animal hair another peripheral layer has been discussed both in these columns1,2 and elsewhere3,4. The supposed layer has been named variously subcutis, between-membrane, and cortical mantle. The most convenient way to show that there does exist a resistant non-keratinous residue beneath the cuticle was described by Alexander and Earland4. Hair or wool is oxidized with weak aqueous peracetic acid and then extracted with dilute ammonia solution. The oxidation destroys the disulphide cross-links which stabilize the keratin, rendering it soluble in alkali. The non-keratinous residue consists of (a) thin tubes each looking like a cast of the cuticle and consisting mainly of the thin membrane, the epicuticle, which envelops the scales externally, and (b) a cortical residue, which seen from the side looks like a rather tenuous tube of cortical cells2. This latter was thought to be the new morphological component, the subcutis4.

The cuticle of mammalian hair.

STUDIES in these laboratories have suggested that the arrangement of scales in the cuticles of mammalian hairs can be more accurately revealed by the examination of fibre sections, using ultra-violet light, than by the use of the electron microscope. This work has shown that the thickness of the cuticle of mammalian hair depends upon the arrangement of the component scales.

XVIII.—Histochemical Studies of Keratin Fibres

During a study of the micro-structure of keratin fibres (Stoves, 1944) it was found that certain members of the Mustelidæ,e.g.kolinsky (M. Sibirica), ermine (M. erminœ), and Jap mink (M. itatsi), possess primary hairs with well-developed cuticle, cortex, and medulla. In the case of rabbits and hares (Leporidæ), however, the corresponding fibres are composed almost entirely of medulla cells. The two types of fibres, therefore, provide suitable material for studying the chemical reactivity of the keratin constituting cuticle, cortex, and medulla of animal hair. Accordingly, the effect of various reagents upon transverse sections of fibres from the above-mentioned animals was examined, and a preliminary report of the results has already been made (Stoves, 1943a). A more detailed account of the work now appears.