STRUCTURE, COMPOSITION, AND ASSEMBLY OF BASEMENT-MEMBRANE
STRUCTURE, COMPOSITION, AND ASSEMBLY OF BASEMENT-MEMBRANE
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DOI：
10.1002/aja.1001850403
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发表时间：
1989-08-01
影响因子：
--
通讯作者：
INOUE, S
中科院分区：
文献类型：
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作者：
LEBLOND, CP;INOUE, S
基底膜是将实质细胞与结缔组织分开的薄层基质。它们的超微结构由称为“索”的不规则、模糊的股的三维网络组成;索厚度平均为3-4 nm。免疫染色显示，索由至少五种物质组成：IV型胶原、层粘连蛋白、硫酸乙酰肝素蛋白聚糖、巢蛋白和纤连蛋白。IV型胶原已被鉴定为在通过纤溶酶消化或盐提取除去其他组分后仍存在的可变厚度的细丝。硫酸乙酰肝素蛋白聚糖表现为两条平行线的集合，称为“双轨”，其在索的表面延伸。在索中检测到层粘连，作为弥散性物质，其中可以分辨出细波浪线。存在于索内的巢蛋白和纤连蛋白尚未被鉴定为可见结构。层粘连蛋白、硫酸乙酰肝素蛋白聚糖、纤连蛋白和巢蛋白与IV型胶原结合的能力已通过旋转阴影可视化和/或生物化学研究证实。将这些物质中的三种-胶原IV、层粘连蛋白（具有少量的巢蛋白污染）和蛋白聚糖-在35 ℃下孵育1小时，产生沉淀物，将其切片用于电子显微镜检查，并对三种孵育物质中的每一种进行金免疫标记。沉淀物中存在三种结构：1）仅由硫酸乙酰肝素蛋白聚糖组成的网状结构，呈两条平行线，类似于双轨; 2）半固体，不规则堆积物，由三种初始物质组成，分布在索状网络上;和3）旋绕片，其也由分布在绳状网络上的三种初始物质组成，此外，基底膜致密层外观均匀，厚度均匀。因此，这些片层与真实基底膜的主要成分非常相似。
Basement membranes are thin layers of matrix separating parenchymal cells from connective tissue. Their ultrastructure consists of a three-dimensional network of irregular, fuzzy strands referred to as "cords"; the cord thickness averages 3-4 nm. Immunostaining reveals that the cords are composed of at least five substances: collagen IV, laminin, heparan sulfate proteoglycan, entactin, and fibronectin. Collagen IV has been identified as a filament of variable thickness persisting after the other components have been removed by plasmin digestion or salt extraction. Heparan sulfate proteoglycan appears as sets of two parallel lines, referred to as "double tracks," which run at the surface of the cords. Lamin in is detected in the cords as diffuse material within which thin wavy lines may be distinguished. The entactin and fibronectin present within the cords have not been identified as visible structures. The ability of laminin, heparan sulfate proteoglycan, fibronectin, and entactin to bind to collagen IV has been demonstrated by visualization with rotary shadowing and/or biochemical studies. Incubation of three of these substances-collagen IV, laminin (with small entactin contamination), and proteoglycan-at 35.degree.C for 1 hr resulted in a precipitate that was sectioned for electron microscopic examination and processed for gold immunolabeling for each of the three incubated substances. Three structures are present in the precipitate: 1) a lacework, exclusively composed of heparan sulfate proteoglycan in the form of two parallel lines, similar to double tracks; 2) semisolid, irregular accumulations, composed of the three initial substances distributed on a cord network; and 3) convoluted sheets, which are also composed of the three initial substances distributed on a cord network but which, in addition, have the uniform appearance and thickness of the lamina densa of basement membrane. Hence these sheets are closely similar to the main component of authentic basement membranes.