Comparative aspects of the inner root sheath in adult and developing hairs of mammals in relation to the evolution of hairs

Journal of Anatomy
Lorenzo Alibardi

Abstract

The inner root sheath (IRS) allows the exit of hairs through the epidermal surface. The fine structure of monotreme and marsupial IRS and trichohyalin is not known. Using electron microscopy and immunocytochemistry, the localization of trichohyalin and transglutaminase have been studied in monotreme and marsupial hairs, and compared with trichohyalin localization in placental hairs. Trichohyalin in all mammalian species studied here is recognized by a polyclonal antibody against sheep trichohyalin. This generalized immunoreactivity suggests that common epitopes are present in trichohyalin across mammals. In differentiating IRS cells, trichohyalin granules of variable dimensions are composed of an immunolabelled amorphous matrix associated with a network of 10-12-nm-thick keratin filaments. Transglutaminase labelling is present among keratin bundles and trichohyalin granules, and in condensed nuclei of terminally differentiating cells of the inner root sheath. The IRS in monotreme hairs is multistratified but lacks a distinguishable Henle layer. Cornification of IRS determines the sculpturing of the fibre cuticle and later shedding from the follicle for the exit of the hair fibre on the epidermal surface. It is hypothesized that...Continue Reading

Citations

Jun 27, 2009·The International Journal of Developmental Biology·Cheng ChangCheng-Ming Chuong
Feb 1, 2013·International Journal of Cosmetic Science·Gillian E WestgateDesmond J Tobin
Mar 13, 2014·Biological Reviews of the Cambridge Philosophical Society·Joseph N Nissimov, Asit Baran Das Chaudhuri
Apr 4, 2017·Experimental Dermatology·Gillian E WestgateMartin R Green
Nov 5, 2014·The Anatomical Record : Advances in Integrative Anatomy and Evolutionary Biology·Lorenzo Alibardi, George Rogers
Sep 6, 2005·The Anatomical Record. Part A, Discoveries in Molecular, Cellular, and Evolutionary Biology·Lorenzo AlibardiLeopold Eckhart
Jun 20, 2012·Journal of Experimental Zoology. Part B, Molecular and Developmental Evolution·Lorenzo Alibardi
Jun 13, 2017·Experimental Dermatology·Danielle DhouaillyOlav Oftedal

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