Alibardi L
Dipartimento di Biologia evoluzionistica e sperimentale, University of Bologna, Bologna, Italy.
J Morphol. 2001 Apr;248(1):64-79. doi: 10.1002/jmor.1021.
Epidermal sloughing in lizards is determined by the formation of an intraepithelial shedding complex in which keratohyalin-like granules are formed. The chemical nature of these granules is unknown, as is their role in keratinization. The goal of this study was to test whether they contain some amino acids similar to those found in mammalian keratohyalin. The embryonic and regenerating epidermis of lizards are useful systems to study the formation of these granules. Histochemically keratohyalin-like granules react to histidine and contain some sulfhydryl groups (cysteine). X-ray microanalysis shows that these granules contain sulfur and often phosphorus, two elements also present in the mature clear, oberhautchen, and beta layer. Instead the mesos, alpha, and lacunar layers contain only sulfur. Most sulfur is probably in a disulfide-bonded form, particularly in mature cells of the shedding complex, in large keratohyalin-like granules, and in the beta-keratin layer. Early differentiating beta-keratin cells have the maximal incorporation of tritiated proline, whereas tritiated arginine is slightly more concentrated in the basal layer of the epidermis. A high uptake of tritiated histidine is observed mainly in keratohyalin-like granules of the clear layer, but also in the oberhautchen layer and forming the alpha-lacunar layer. Immunogold electron microscopy shows that keratohyalin-like granules do not localize keratin but are embedded within a keratin network. These results suggest that keratohyalin-like granules of lizards, like mammalian keratohyalin, contain some sulfur-rich and histidine-rich proteins. These granules participate in the process of hardening of the clear layer that molds the spinulae of the deeper oberhautchen to form the superficial microornamentation.
蜥蜴的表皮脱落取决于上皮内脱落复合体的形成，在此复合体内会形成透明角质样颗粒。这些颗粒的化学性质及其在角质化过程中的作用尚不清楚。本研究的目的是测试它们是否含有一些与哺乳动物透明角质中发现的氨基酸相似的氨基酸。蜥蜴的胚胎和再生表皮是研究这些颗粒形成的有用系统。组织化学上，透明角质样颗粒对组氨酸有反应，并含有一些巯基（半胱氨酸）。X射线微分析表明，这些颗粒含有硫，且常常含有磷，这两种元素在成熟的透明层、表层和β层中也存在。相反，中层、α层和腔隙层仅含硫。大多数硫可能以二硫键结合的形式存在，特别是在脱落复合体的成熟细胞、大的透明角质样颗粒和β角蛋白层中。早期分化的β角蛋白细胞对氚化脯氨酸的掺入量最大，而氚化精氨酸在表皮基底层中的浓度略高。主要在透明层的透明角质样颗粒中观察到对氚化组氨酸的高摄取，在表层和形成α腔隙层的过程中也有观察到。免疫金电子显微镜显示，透明角质样颗粒并不定位角蛋白，而是嵌入角蛋白网络中。这些结果表明，蜥蜴的透明角质样颗粒与哺乳动物的透明角质一样，含有一些富含硫和组氨酸的蛋白质。这些颗粒参与透明层的硬化过程，该层塑造了较深表层的小刺，从而形成表面微纹饰。
