The Keratinization of Epidermal Scales, Feathers and Hairs

Spearman, R. I. C.

doi:10.1111/j.1469-185x.1966.tb01538.x

Cited by 142 publications

(127 citation statements)

References 117 publications

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“…The present histochemical investigations reveal the nonkeratinized nature of the epidermis of H. fossilis and are in support of the general believe that the epidermis of most of the teleosts in general are nonkeratinized in nature (Burgess, 1956;Van Oosten, 1957;Spearman, 1966;Henrikson and Matoltsy, 1968;Whitear, 1970, 1971and Roberts et al (1971 . Keratinized nature of the epidermis of some teleosts has, however, been reported histochemically by Mittal and Banerjee (1974 a, b) ; and electron microscopically by Kawaguti (1966) and Yamada (1968).…”

Section: Discussionsupporting

confidence: 53%

Protein Histochemistry in the Skin of a Fresh-Water Catfish Heteropneustes Fossilis (Bloch) (Heteropneustidae, Pisces)

Mittal

1976

Acta Histochem. Cytochem

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Section: Discussionsupporting

confidence: 53%

Protein Histochemistry in the Skin of a Fresh-Water Catfish Heteropneustes Fossilis (Bloch) (Heteropneustidae, Pisces)

Mittal

1976

Acta Histochem. Cytochem

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“…Also, keratinization is likely associated with the speed at which the feather grows [34,38], potentially explaining previously reported associations between colour and growth bar width [22,28]. The rate of feather keratinization is strongly influenced by the initial amount and concentration of keratin monomers [67], which in turn is mostly limited by keratin gene transcription and mRNA abundance [68].…”

Section: Sexual Selection and The Evolution Of Iridescent Plumagementioning

confidence: 65%

“…This leads us to hypothesize that nanostructural arrangement occurs through self-assembly processes. In regenerating feathers, keratinization is a complex process involving at least two chronologically separated phases: the synthesis phase, where keratin molecules are synthesized by ribosomes from free amino acids, and the keratogenous (or transitional) phase, where other cellular constituents are broken down and large-scale polymerization follows a reduction in metabolism associated with cellular necrosis [34][35][36]. The developmental steps that form the outer melanin layer and the thin keratin cortex responsible for iridescent colour production are only observed at these very last stages of cellular differentiation (as also observed by [37]).…”

Section: Discussionmentioning

confidence: 99%

Nanostructural self-assembly of iridescent feather barbules through depletion attraction of melanosomes during keratinization

Maia

Macêdo

Shawkey

2011

J. R. Soc. Interface.

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Avian plumage colours are model traits in understanding the evolution of sexually selected ornamental traits. Paradoxically, iridescent structural colours, probably the most dazzling of these traits, remain the most poorly understood. Though some data suggest that expression of bright iridescent plumage colours produced by highly ordered arrays of melanosomes and keratin is condition-dependent, almost nothing is known of their ontogeny and thus of any developmental mechanisms that may be susceptible to perturbation. Here, we use light and electron microscopy to compare the ontogeny of iridescent male and non-iridescent female feathers in blue-black grassquits. Feather barbules of males contain a single layer of melanosomes bounded by a thin layer of keratin-producing blue iridescent colour, while those of females contain disorganized melanosomes and no outer layer. We found that nanostructural organization of male barbules occurs late in development, following death of the barbule cell, and is thus unlikely to be under direct cellular control, contrary to previous suggestions. Rather, organization appears to be caused by entropically driven self-assembly through depletion attraction forces that pin melanosomes to the edge of barbule cells and to one another. These forces are probably stronger in developing barbules of males than of females because their melanosomes are (i) larger, (ii) more densely packed, and (iii) more homogeneously distributed owing to the more consistent shape of barbules during keratinization. These data provide the first proposed developmental pathway for iridescent plumage colours, and suggest that any condition dependence of iridescent barbules is likely driven by factors other than direct metabolic cost.

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“…The distribution of chemical constituents in the pangolin scale is different from the reptilian type of scale [295]. Indeed, the development of scales in reptiles and pangolins are an example of convergent evolution.…”

Section: Pangolin Scalesmentioning

confidence: 99%

“…The pangolins have a large number of keratinous scales [21,295] covering their skin, the only known mammal with this adaptation [296]. The pangolins, also named scaly anteaters, are found naturally in tropical regions throughout Africa and Asia, and are famous for their distinctive protection mechanism: they curl up into a ball when threatened, with the sharp and plate-like overlapping scales projecting outwards, providing effective protection and extra defense (Fig.…”

Section: Pangolin Scalesmentioning

confidence: 99%

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

Wang

Yang

McKittrick

et al. 2016

Progress in Materials Science

658

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 Epidermal Scales, Feathers and Hairs

Cited by 142 publications

References 117 publications

Protein Histochemistry in the Skin of a Fresh-Water Catfish Heteropneustes Fossilis (Bloch) (Heteropneustidae, Pisces)

Protein Histochemistry in the Skin of a Fresh-Water Catfish Heteropneustes Fossilis (Bloch) (Heteropneustidae, Pisces)

Nanostructural self-assembly of iridescent feather barbules through depletion attraction of melanosomes during keratinization

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

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