Alibardi Lorenzo
Dipartimento di Biologia evoluzionistica sperimentale, University of Bologna, via Selmi 3, 40126, Italy.
Ann Anat. 2007;189(6):583-95. doi: 10.1016/j.aanat.2007.06.001.
The present ultrastructural and immunocytochemical study on developing and regenerating feathers in the chick, zebrafinch and quail describes the formation of alpha-keratin cells in the sheath and their transition into beta-keratin cells in the calamus. In the first stages of feather formation cells are produced in the lower part of the follicle, migrate upward and form the elongating sheath of the feather filaments that grows outside the follicle. Sheath cells initially (anagen) contain bundles of alpha-keratin filaments. By the end of anagen at the base of the feather inside the follicle cells in continuation with the sheath produce homogenous bundles with the aspect of beta-keratin filaments. These bundles are immunoreactive for beta-keratin antibodies suggesting that beta-keratin is added to the initial framework of alpha-keratin. The packing of dense and hard corneous material in these cells eventually forms the calamus. The Latter corneous tissue replaces at the base of feathers the softer sheath present in more apical regions of the feather filaments. The increase of feather (beta)-keratin in cells of the calamus determines the formation of long bundles of corneous material. The modality of cornification in feathers is compared to the process of hard cornification of reptilian scales and claws and mammalian hairs and nails.
目前对鸡、斑胸草雀和鹌鹑羽毛发育及再生过程进行的超微结构和免疫细胞化学研究，描述了鞘中α-角蛋白细胞的形成及其在羽根中向β-角蛋白细胞的转变。在羽毛形成的最初阶段，细胞在毛囊下部产生，向上迁移并形成在毛囊外生长的羽丝伸长的鞘。鞘细胞最初（生长期）含有α-角蛋白丝束。在生长期结束时，在毛囊内羽毛基部与鞘相连的细胞产生具有β-角蛋白丝外观的均匀束。这些束对β-角蛋白抗体具有免疫反应性，表明β-角蛋白被添加到α-角蛋白的初始框架中。这些细胞中致密坚硬的角质物质堆积最终形成羽根。后者的角质组织在羽毛基部取代了羽丝更顶端区域存在的较软的鞘。羽根细胞中羽毛（β）-角蛋白的增加决定了角质物质长束的形成。将羽毛的角质化方式与爬行动物鳞片和爪子以及哺乳动物毛发和指甲的硬角质化过程进行了比较。
