Alibardi Lorenzo
Dipartimento di Biologia evoluzionistica sperimentale, Università di Bologna, Bologna 40126, Italy.
J Morphol. 2005 Jul;265(1):52-69. doi: 10.1002/jmor.10337.
The proliferation of the epidermis in soft skin, claws, and scutes of the carapace and plastron in the tortoise (Testudo hermanni) and the turtle (Chrysemys picta) were studied using autoradiographic and immunocytochemical methods. During the growing season, a basal keratinocyte in the epidermis of soft skin and claws takes 5-9 days to migrate into the corneous layer. In the tortoise, during fall/winter (resting season) a few alpha-keratin cells are produced in soft epidermis and hinge regions among scutes and occasional beta-keratin cells in the outer scute surface. When growth is resumed in spring (growing season), cell proliferation is intense, mainly around hinge regions and tips of marginal scutes. No scute shedding occurs and numerous beta-keratin cells are produced around the hinge regions, while alpha-keratin cells disappear. Beta-cells form a new thick corneous layer around the hinge regions, which constitute the growing rings of scutes. Beta-keratin cells produced in more central parts of scutes maintain a homogeneous thickness of the corneous layer along the whole scute surface. In the turtle, a more complicated process of scute growth occurs than in the tortoise. At the end of the growing season (late fall) the last keratinocytes formed beneath the old stratum corneum of the outer scale surface and hinge regions produce more alpha- than beta-keratin. These thin alpha-keratin cells form a scission layer below the old stratum corneum, which extends from the hinge regions toward the center of scutes and the tip of marginal scutes. In the resting season (fall/winter) most cells remain within the germinative layer of the carapace and plastron and a few alpha-cells move in 7-9 days into the corneous layer above hinge regions. In the following spring/summer (growing season) a new generation of beta-keratin cells is produced beneath the scission layer from the hinge region and more central part of the scutes. The epidermis of the inner surface of scutes and hinge regions contains most of the cells incorporating thymidine and histidine, while the remaining outer scute surface is less active. It takes 5-9 days for a newly produced beta-cell to migrate into the corneous layer. These cells form a new corneous layer that extends the whole scute surface underneath the maturing scission layer. The latter contains lipids and eventually flakes off, determining shedding of the above outer corneous layer in late spring or summer.
采用放射自显影和免疫细胞化学方法，研究了陆龟（赫尔曼陆龟）和水龟（彩龟）柔软皮肤、爪子以及背甲和腹甲盾片的表皮增殖情况。在生长季节，柔软皮肤和爪子表皮中的基底角质形成细胞需要5至9天迁移至角质层。在陆龟中，秋冬（休眠季节）时，柔软表皮和盾片间的铰链区域会产生少量α - 角蛋白细胞，盾片外表面偶尔会出现β - 角蛋白细胞。当春季（生长季节）恢复生长时，细胞增殖旺盛，主要集中在铰链区域和边缘盾片的尖端周围。盾片不会脱落，铰链区域周围会产生大量β - 角蛋白细胞，而α - 角蛋白细胞消失。β细胞在铰链区域周围形成新的厚角质层，构成盾片的生长环。盾片更中央部分产生的β - 角蛋白细胞使角质层在整个盾片表面保持均匀厚度。在水龟中，盾片生长过程比陆龟更为复杂。在生长季节末期（深秋），在外鳞片表面和铰链区域的旧角质层下方形成的最后一批角质形成细胞产生的α - 角蛋白比β - 角蛋白更多。这些薄的α - 角蛋白细胞在旧角质层下方形成一个分裂层，该层从铰链区域向盾片中心和边缘盾片尖端延伸。在休眠季节（秋冬），大多数细胞保留在背甲和腹甲的生发层内，少数α细胞在7至9天内迁移至铰链区域上方的角质层。在接下来的春夏（生长季节），新一代β - 角蛋白细胞在分裂层下方从铰链区域和盾片更中央部分产生。盾片内表面和铰链区域的表皮含有大多数掺入胸腺嘧啶核苷和组氨酸的细胞，而其余的盾片外表面活性较低。新产生的β细胞需要5至9天迁移至角质层。这些细胞形成一个新的角质层，在成熟的分裂层下方延伸至整个盾片表面。后者含有脂质，最终会剥落，导致上述外角质层在春末或夏末脱落。
