Keratinization and ultrastructure of the epidermis of late embryonic stages in the alligator (Alligator mississippiensis)

被引:31
作者
Alibardi, L
Thompson, MB
机构
[1] Univ Bologna, Dipartimento Biol Evoluzionist Sperimentale, I-40216 Bologna, Italy
[2] Univ Sydney, Sch Biol Sci, Sydney, NSW 2006, Australia
[3] Univ Sydney, Wildlife Inst, Sydney, NSW 2006, Australia
关键词
alligator; alpha-keratin; beta-keratin; development; epidermis; immunocytochemistry; ultrastructure;
D O I
10.1046/j.1469-7580.2002.00075.x
中图分类号
R602 [外科病理学、解剖学]; R32 [人体形态学];
学科分类号
100101 ;
摘要
Using specific anti-beta keratin and general anti-alpha keratin antibodies, keratins were located in the epidermis of the alligator during the final developmental stages by ultrastructural and immunocytochemical methods. The maturation of the bilayered periderm (= embryonic epidermis) coincides with the disappearance of cell organelles, including the 25-35-nm-thick coarse filaments, and the coalescing of alpha-keratin filaments into a compact mass. The plasmalemma of peridermal cells forms a 15-25-nm-thick electron-dense corneous envelope. These changes start at stage 25, about 3 weeks before hatching, and continue until hatching when the embryonic epidermis is shed. immature beta-keratogenic cells beneath the embryonic epidermis accumulate immunolabelled beta-filaments which are packed into thin, electron-pale beta-keratogenic cells in the corneous layer. Together, electron-pale and electron-dense materials form a compact 3-4-nm filament pattern of beta-keratin. Melanosomes from epidermal melanocytes, incorporated into beta-cells, give rise to the banded skin pattern of hatchlings. beta-keratin production is much reduced in the hinge regions, where many alpha-filaments remain packed together with lipid droplets or mucous granules into thinner, more electron-dense, alpha-cells. The keratinaceous material of the alpha-cells is mostly concentrated along the cell membrane, while the lipid/mucous material remains centrally located, as in sebokeratinocytes of the apteric areas of avian skin. Some lipid and mucus is also incorporated into typical beta-cells of the outer scale surface, so that lipids are part of the fully keratinized hard keratin layer of the alligator. Lipids within beta-cells of outer scale surfaces and a-cells of the hinge region are probably responsible for limiting water loss and ion movements across the skin. Neither typical mammalian keratohyalin granules nor lepidosaurian keratohyalin-like granules were detected anywhere in alligator epidermis. The combination of anti-beta and anti-alpha keratin antibodies revealed different distributions of beta- and alpha-keratins. in late embryonic stages (25-26 to hatching), beta-keratin occurs only in the upper suprabasal cells, in prekeratinized and keratinized layers, whereas a-keratin bundles (tonofilaments) remain only in the lowest layers. The cross-reactivity of the beta-antibody, produced against a chick scale keratin, further shows that avian and crocodilian hard (beta) keratins share common antigenic sites, reflecting a phylogenetic affinity between these taxa.
引用
收藏
页码:71 / 84
页数:14
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