The environment of calcified components in keratins

Abstract

Regions in the cortex of some keratin fibres are shown to contain a relatively high proportion of non-keratinous material. The microfibrillar orientation in these regions is shown to be biaxial in nature and, in addition, areas of amorphous material are reported. Calcium salts, in particular hydroxyapatite, have been located and identified using electron diffraction, which has also proved valuable in correlating the incidence of some non-keratinised cells in the inner part of the cortex with the histochemical properties of this region. A comparison is made between the environment of the sites of calcification in keratin with those in collagen and elastin.Key words: Calcification --Hydroxyapatite --Keratin --Hair --Electron diffraction.Certaines r6gions du cortex des fibres de k6ratine contiennent une proportion relativement 61ev6e de mat6riel non k6ratinis6. L'orientation microfibrillaire dans ces r6gions est biaxiale et on y trouve, en outre, des zones de mat6riel amorphe. Les sels calciques, et en particnlier l'hydroxyleapatite, sont 6tudi6s par diffraction 61ectronique qui permet de les localiser et de les identifier. En ontre, cette technique permet de d6terminer la fr6quence de cellules nonk6ratinis6es clans la partie interne du cortex et de les comparer avec les propri6t6s histochimiques de cette r6gion. Une comparison est effectu6e entre la calcification de ]a k6ratine et celle int6ressant le collag~ne et l%lastine.Es wird gezeigt, dab Bereiche im Cortex yon gewissen Keratinfasern einen relativ hohen Anteil an nichtkeratinSsem Material enthalten. Ferner konnte nachgewiesen werden, dab die Orientierung der Mikrofibrillen in diesen Bereichen biaxia]er Art ist, und dal3 Bezirke yon amorphem Material vorhanden sind. Die Caleiumsalze und insbesondere das Hydroxyapatit konnten mit Hilfe der Elektronendiffraktion lokalisiert und identifiziert werden. Diese Methode hat sich auch als wertvoll erwiesen, um die Wechselbeziehung zwischen dem Vorkommen von einigen nichtkeratinisierten Zellen im Cortexinnern und den histochemischen Eigenschaften dieser Regionen zu zeigen. Ein Vergleich wird gemacht zwischen der Umgebung der Verkalkungsstellen im Keratin mit derjenigen im Kollagen und im Elastin.

A perspective on the evidence for keratin protein preservation in fossils: An issue of replication versus validation

“…Calcified materials have also been reported to interfere in immunochemistry experiments (Sedivy and Battistutti, 2003), so any phosphatic ash resulting from thermally degraded feathers should also be considered as a potential explanation of their antibody results. The claim by Schweitzer et al (2018) that most keratins are not biomineralized requires supporting evidence since calcium phosphates have been detected and quantified in a wide variety of extant keratinous tissue types from phylogenetically diverse taxa (Earland et al, 1962;Blakey et al, 1963;Pautard, 1963Pautard, , 1964Pautard, , 1966Pautard, , 1970Blakey and Lockwood, 1968;Baggott et al, 1988;Hieronymus et al, 2006;Szewciw et al, 2010). For example, whale baleen contains relatively high amounts of calcium phosphate in vivo for mechanical reinforcement (Pautard 1963;Szewciw et al, 2010), and Miocene fossil whale baleen preserves as phosphate (Gioncada et al, 2016).…”

Preservation of feather fibers from the Late Cretaceous dinosaur Shuvuuia deserti raises concern about immunohistochemical analyses on fossils

“…A phosphatic preservational mode of fossil keratinous structures is unsurprising since many different keratinous tissues are hardened via calcium phosphate deposition in vivo to varying degrees. For example, calcium phosphate has been measured or detected in fresh/modern claw, horn, beak, and hoof sheaths, nails, baleen, hair, quills, whiskers, and feathers, especially feather calami (Blakey et al, 1963;Pautard, 1963Pautard, , 1964Pautard, , 1970Blakey and Lockwood 1968;Lucas and Stettenheim 1972;Szewciw et al, 2010). Calcification of keratinous structures appears to change their material properties of the integumentary structure, positively correlating with hardness and presumably related to the biological function of the structure (Baggott et al, 1988;Bonser, 1996;Szewciw et al, 2010).…”

Ultrastructure of odontogenic cells during enameloid matrix synthesis in tooth buds from an elasmobranch, Raja erinacae

“…Polyclonal antisera against mammalian tooth bud proteins also react with the keratinous teeth of the hagfish (Slavkin et al, 1983a). Keratin proteins, like skate enameloid matrix, can initiate the formation of apatite crystallites (Blakey and Lockwood, 1968).…”