Mizuhira Vinci
Tokyo Medical and Dental University, Medical Research Institute, Department of Anatomy, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
J Electron Microsc (Tokyo). 2004;53(1):63-78. doi: 10.1093/jmicro/53.1.63.
The digital pads of rhacophorid tree-frogs were studied by light and electron microscopy using a tannic acid-containing fixative. The digital pads are concave mucous epithelial structures surrounded by a soft raised epithelial border. The cells in the first epithelial layer are separated by deep intercellular fissures and the epithelial cell surface is densely covered with thousands of setaceous keratinized microvilli. These are estimated to be 0.1-0.5 microm in width and have flattened tips. A longitudinal section view of the pad's first epithelial cell layer shows a rugose pattern. Deep intercellular fissures in between the cells are formed by the enzymatic activity of invading mononuclear leukocytes in the interepithelial cell junctions. The 'rugose' surface epithelial cell layer is peeled off from the underlying second epithelial layer by the epithelial metabolism that occurs when the leukocytes invade the second interepithelial cell spaces. Thus, the second epithelial cell layer becomes the new 'rugose' epithelial cell layer. The ultrastructures of the frog digital pads are compared with those of other biological suction cups, such as those of octopuses and geckos. Further discussed are their interatomic or intermolecular mechanofunctional aspects, such as hanging upside down and moving easily over smooth surfaces with the aid of interatomic or intermolecular forces, the so-called 'van der Waals forces', without any energy expenditure.
利用含鞣酸的固定剂，通过光学显微镜和电子显微镜对树蛙科树蛙的指垫进行了研究。指垫是凹陷的黏液上皮结构，周围环绕着柔软凸起的上皮边缘。第一层上皮细胞被深深的细胞间裂隙分隔开，上皮细胞表面密布着数千根刚毛状角质化微绒毛。这些微绒毛宽度估计为0.1 - 0.5微米，顶端扁平。指垫第一层上皮细胞层的纵切面呈现出皱襞状图案。细胞间的深裂隙是由侵入上皮细胞连接处的单核白细胞的酶活性形成的。当白细胞侵入第二层上皮细胞间隙时，上皮细胞发生代谢，“皱襞状”表面上皮细胞层从下面的第二层上皮层剥离。于是，第二层上皮细胞层变成了新的“皱襞状”上皮细胞层。将蛙指垫的超微结构与其他生物吸盘（如章鱼和壁虎的吸盘）的超微结构进行了比较。还进一步讨论了它们的原子间或分子间机械功能方面，例如借助原子间或分子间力（即所谓的“范德华力”）倒挂并在光滑表面轻松移动，且无需任何能量消耗。
