Three-dimensional network of cords: the main component of basement membranes.
Three-dimensional network of cords: the main component of basement membranes.
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三维索网：基底膜的主要成分。
DOI：
10.1002/aja.1001810403
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Leblond,CP
中科院分区：
文献类型：
--
作者：
Inoue,S;Leblond,CP
基底膜分为两种类型：（1）薄基底膜，如大鼠的表皮、气管、空肠、生精小管和输精管，小鼠的纤毛突和猴的生精小管；（2）厚的基底膜，如小鼠的晶状体囊和大鼠的赖克特膜。在戊二醛中随后进行后渗透或在高锰酸钾中固定后，使用高倍电子显微镜检查这两种类型。薄基底膜和厚基底膜的基本结构被发现是由不规则的模糊链（称为“绳索”）组成的三维网络；这些线的直径各不相同，但在所有检查的情况下平均为 4 nm。然而，分隔线的空间不同。在薄基底膜的致密层中，这些空间的直径平均约为 14 nm，而在透明层中，其直径可达 40 nm 以上。中间值记录在厚基底膜中。最后，第三层不稳定的薄基底膜层，即纤维网状部，由与致密层结合的不连续元素组成：即锚定原纤维、微原纤维或胶原原纤维。特别是，胶原原纤维通常被与致密层连续的突起包围，并且同样由典型的索网络组成。最后，在每个基底膜中都遇到两个特征：（1）一些索与1.4至3.2纳米粗的细丝连续或在其中显示出这样的细丝；用蛋白水解酶纤溶酶处理生精小管基底膜后，细丝变得众多，因为索状体厚度减少，可以减少为细丝，并且（2）在索状体表面，偶尔可以看到4.5 nm宽的两条平行线，称为“双轨”。根据证据表明，细丝是IV型胶原分子，双轨是聚合的硫酸乙酰肝素蛋白聚糖，因此提出：脐带由 IV 型胶原的轴向丝组成，其上有相关的糖蛋白成分（层粘连蛋白、内动蛋白、纤连蛋白）和蛋白聚糖的双轨。
Basement membranes were divided into two types: (1)thinbasement membranes, such as those of the epidermis, trachea, jejunum, seminiferous tubule, and vas deferens of the rat, the ciliary process of the mouse, and the seminiferous tubule of the monkey, and (2) thick basement membranes, such as the lens capsule of the mouse and Reichert's membrane of the rat. High‐magnification electron microscopy was used to examine both types after fixation either in glutaraldehyde followed by postosmication or in potassium permanganate.The basic structure of thin and thick basement membranes was found to be a three‐dimensional network of irregular, fuzzy strands referred to as “cords”; the diameter of these cords was variable, but averaged 4 nm in all cases examined. The spaces separating the cords differed, however. In the lamina densa of thin basement membranes, the diameter of these spaces averaged about 14 nm in every case, whereas in the lamina lucida it ranged up to more than 40 nm. Intermediate values were recorded in thick basement membranes. Finally, the third, inconstant layer of thin basement membranes, pars fibroreticularis, was composed of discontinuous elements bound to the lamina densa: i.e., anchoring fibrils, microfibrils, or collagen fibrils. In particular, collagen fibrils were often surrounded by processes continuous with the lamina densa and like‐wise composed of a typical cord network. Finally, two features were encountered in every basement membrane: (1) a few cords were in continuity with a 1.4‐ to 3.2‐nm thick filament or showed such a filament within them; the filaments became numerous after treatment of the seminiferous tubule basement membrane with the proteolytic enzyme, plasmin, since cords decreased in thickness and could be reduced to a filament, and (2) at the cord surface, it was occasionally possible to see 4.5‐nm‐wide sets of two parallel lines, referred to as “double tracks”.On the basis of evidence that the filaments are type IV collagen molecules and the double tracks are polymerized heparan sulfate proteoglycan, it is proposed that cords are composed of an axial filament of type IV collagen to which are associated glycoprotein components (laminin, entactin, fibronectin) and the double tracks of the proteoglycan.