The Keratinization of Epidermis and Its Derivatives, Especially the Hair, as Shown by X‐ray Diffraction and Histochemical Studies

Giroud, A.; Leblond, C. P.

doi:10.1111/j.1749-6632.1951.tb31963.x

Cited by 129 publications

(31 citation statements)

References 37 publications

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“…Bear (25) reviews the available data concerning the histochemical and chemical properties of the finer argyrophilic fibers (commonly called reticulin) and concludes that they are basically collagen but have a particular affinity for polysaccharide, either adsorbed on or occluded within them. Since no particular band of amorphous material has been observed by the electron microscope associated with these filaments or the dermal membrane, the glycoprotein which can be demonstrated by histochemical techniques (11)(12)(13)26) between the connective tissue and basal cells may well be simply a result of the concentration of reticular fibers in this region. The alternative localization for the polysaccharide would be in the dermal membrane itself or between it and the basal cell membrane (13).…”

Section: Discussionmentioning

confidence: 99%

An Electron Microscope Study of the Epidermis of Mammalian Skin in Thin Sections

Selby

1955

The Journal of Cell Biology

237

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1. Basal epidermal cells and their junction with the dermis, as revealed in thin sections of osmium-fixed human and rodent skin, were studied with the electron microscope. Phosphotungstic acid staining was occasionally used to increase the electron density of membranous and filamentous structures. 2. Along the dermo-epidermal junction in all skin specimens there is a sub-microscopic (∼350 A thick) membrane following the basal contours of the epidermal cells, but separated from them by an ∼300 A space. No epidermal or dermal filaments can be seen to cross it and except in embryonic skin it has no associated band of amorphous material. It is called the "dermal membrane" to distinguish it from the thicker membrane and associated material commonly called the "basement membrane." 3. In adult human skin the basal cell membrane facing the dermal membrane is continuous with, or adjacent to regularly spaced groups of small dense rodlets at which tonofilaments are attached and appear to terminate. Less dense spherical granules are also found in the cellular ectoplasm and are unattached to filaments. 4. The connective tissue fibers in the upper dermis were narrower (≧300 A) than, but displayed the same period (≧350 A) as the collagen fibers in the deeper dermis. The related fibers in embryonic human skin were even narrower (150 to 250 A). In accordance with the views of others that these are "young" collagen with great affinity for polysaccharide, they are called collagen fibers. 5. The same cytoplasmic components are found in all basal epidermal cells: mitochondria, many filaments, many submicroscopic particulates, and only very occasional vesicles of the endoplasmic reticulum. Adult human cells possess pigment granules and intercellular bridges, in addition. Before keratinization is evident, no intercellular bridges and little or no cytoplasmic filaments are visible. The scarcity of vesicles of the endoplasmic reticulum and the prevalence of submicroscopic particulates (80 to 150 A) distributed at random through the cytoplasm, support the view (19) that basophilia and cytoplasmic nucleoprotein are associated with the particulates. 6. Cytoplasmic filaments are <100 A wide and are directed toward the dermo-epidermal junction and to intercellular bridges (when they occur). Because of their obvious identity as the submicroscopic constituents of tonofibrils, they were called "tonofilaments" and believed to represent the keratin-like fibrous protein "epidermin" (29). Bundles of them appear identical with Herxheimer fibers when, particularly in thick skin, they extend from the outer nuclear membrane to the granules spaced along the dermo-epidermal junction. 7. In human skin, adjacent basal cells are separated by simple cell membranes and connected by intercellular bridges. The filaments of one cell are attached to dense elongate granules in these bridges which are separated by a narrow less electron-dense space from a matching granule to which the filaments of the neighboring cell are attached. No filaments have been observed to cross the space in these bridges. In between the bridges adjacent cell membranes may separate from each other leaving an intercellular space. Although occasional basal cells possess a large perinuclear area devoid of cytoplasmic filaments, none following the classical histological description of "clear" cells were noted. 8. Pigment granules are extremely electron-dense with irregular angular outline. Their smallest diameter was significantly greater in Negro than in white skin while the lengths also appeared greater in the former skin type.

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Section: Discussionmentioning

confidence: 99%

An Electron Microscope Study of the Epidermis of Mammalian Skin in Thin Sections

Selby

1955

The Journal of Cell Biology

237

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“…1.1) referred to as the zone of keratinisation (6,14). Here both the large fibrils and their component fine filaments become more clearly defined ( Fig.…”

Section: The Formation Of the Cortex And The Structure Of Keratinmentioning

confidence: 99%

The Electron Microscopy of the Human Hair Follicle

Birbeck

Mercer

1957

The Journal of Cell Biology

247

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1. The presumptive cortical cells of hair in the undifferentiated matrix of the bulb contain mitochondria, agranular vesicles, and many small dense R.N.P. particles, but no keratin, pigment granules, or endoplasmic reticulum. 2. In the mid-bulb region intercellular adhesion is limited to small localised areas. Intercellular gaps are common and the cell surfaces are irregularly convoluted. The melanocyte processes penetrate the cell gaps. The relation between their pigment-bearing tips and the involutions of the cell membranes suggests an active phagocytosis of the tips. 3. Fibrous keratin first appears in loose parallel strands of fine filaments (ca. 60 A diameter) in the mid-bulb. The filaments, the long mitochondria, and elongated nucleus are all parallel to the long axis of the cell and the axis of the follicle. 4. At the level of the constriction of the bulb and above, a dense amorphous substance appears between the fine filaments and apparently acts as adhesive cement. The bundles of filaments now form well defined fibrils. The packing of the filaments within the fibrils is in places hexagonal and elsewhere in the form of "whorls." 5. At higher levels further filaments and interfilamentous cement are added together and the whole cytoplasmic space becomes packed with fibrils which finally condense to massive blocks of keratin. The residual cellular material occupies the interstices. 6. The addition of the interfilamentous substance is regarded as an essential factor in keratinisation. Keratin is considered to be a complex made of fine filaments (α-filaments) embedded in an amorphous substance (γ-keratin) which has the higher cystine content. 7. The wide-angle fibre-type x-ray pattern is thought to be due to scattering by the fine α-filaments and some low angle lateral spacings to the filament-plus-cement structure.

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“…In terms of modes of biosynthesis [32] and the amount of sulfur cross links [15], keratins can be classified as soft keratins (e.g. stratum corneum) usually weakly consolidated and with a lower amount of sulfur and lipids, and hard keratins found in hair, nails, claws, beaks, quills, which have a more coherent structure and a higher amount of sulfur [16].…”

Section: Classification Of Keratinmentioning

confidence: 99%

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Wang

Yang

McKittrick

et al. 2016

Progress in Materials Science

660

474

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a b s t r a c tA ubiquitous biological material, keratin represents a group of insoluble, usually high-sulfur content and filament-forming proteins, constituting the bulk of epidermal appendages such as hair, nails, claws, turtle scutes, horns, whale baleen, beaks, and feathers. These keratinous materials are formed by cells filled with keratin and are considered 'dead tissues'. Nevertheless, they are among the toughest biological materials, serving as a wide variety of interesting functions, e.g. scales to armor body, horns to combat aggressors, hagfish slime as defense against predators, nails and claws to increase prehension, hair and fur to protect against the environment. The vivid inspiring examples can offer useful solutions to design new structural and functional materials.Keratins can be classified as a-and b-types. Both show a characteristic filament-matrix structure: 7 nm diameter intermediate filaments for a-keratin, and 3 nm diameter filaments for b-keratin.Both are embedded in an amorphous keratin matrix. The molecular unit of intermediate filaments is a coiled-coil heterodimer and that of b-keratin filament is a pleated sheet. The mechanical response of a-keratin has been extensively studied and shows linear Hookean, yield and post-yield regions, and in some cases, a high reversible elastic deformation. Thus, they can be also be considered 'biopolymers'. On the other hand, b-keratin has not been investigated as comprehensively. Keratinous materials are strain-rate sensitive, and the effect of hydration is significant.Keratinous materials exhibit a complex hierarchical structure: polypeptide chains and filament-matrix structures at the nanoscale, Progress in Materials Science 76 (2016) 229-318 Contents lists available at ScienceDirect Progress in Materials Sciencej o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p m a t s c i organization of keratinized cells into lamellar, tubular-intertubular, fiber or layered structures at the microscale, and solid, compact sheaths over porous core, sandwich or threads at the macroscale. These produce a wide range of mechanical properties: the Young's modulus ranges from 10 MPa in stratum corneum to about 2.5 GPa in feathers, and the tensile strength varies from 2 MPa in stratum corneum to 530 MPa in dry hagfish slime threads. Therefore, they are able to serve various functions including diffusion barrier, buffering external attack, energy-absorption, impact-resistance, piercing opponents, withstanding repeated stress and aerodynamic forces, and resisting buckling and penetration.A fascinating part of the new frontier of materials study is the development of bioinspired materials and designs. A comprehensive understanding of the biochemistry, structure and mechanical properties of keratins and keratinous materials is of great importance for keratin-based bioinspired materials and designs. Current bioinspired efforts including the manufacturing of quill-inspired aluminum composites, animal horn-inspired SiC composites, and feather-i...

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The Keratinization of Epidermis and Its Derivatives, Especially the Hair, as Shown by X‐ray Diffraction and Histochemical Studies

Cited by 129 publications

References 37 publications

An Electron Microscope Study of the Epidermis of Mammalian Skin in Thin Sections

An Electron Microscope Study of the Epidermis of Mammalian Skin in Thin Sections

The Electron Microscopy of the Human Hair Follicle

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

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