Markwald R R, Fitzharris T P, Manasek F J
Am J Anat. 1977 Jan;148(1):85-119. doi: 10.1002/aja.1001480108.
Development of chick and rat endocardial cushions (cardiac mesenchyme) was studied histologically (using Nomarski differential interference optics on living and unfixed tissue), ultrastructurally (scanning and transmission electron microscopy), cytochemically (using acidified dialyzed iron as a visual probe for polyanionic material) and autoradiographically (using 35S) to elucidate the origin of the mesenchyme, the morphologic sequences leading to cushion formation and secretion of sulfated glycosaminoglycans, if any, by migrating mesenchymal cells. Cushion formation was similar for both species. Mesenchymal cells appeared initially, in 16- to 18-somite embryos, beneath the endothelium (which lacked a basal lamina) of the future atrioventricular canal and outflow tract. The cytoplasm of cushion mesenchymal cells was structurally similar to the ensothelium; probably these cells arose by proliferation of the endothelium. Mitotic figures among the "seeded" cells were also numerous. Cushion cells were initially attached to the endothelium by desmosomes but acquired motile apparatus (pseudopodia and filopodia containing microtubules and microfilamentous bundles). Serial sectioning of successively-aged embryos (20-44 somites) indicated a centrifugal migratory direction. Interaction of the cell processes with extracellular matrix suggested that the latter was used as a migratory substrate. Contact of the advancing wedge of cushion cells with the myocardium produced no alteration in cell structure or mitotic activity. Localization of hyaluronidase-sensitive, dialyzed iron (DI) precipitates in 250-nm Golgi vacuoles and hyaluronidase-sensitive 35S-endangendered silver grains over cushion cells indicated that this tissue contributed sulfated macromolecules to the matrix. Localization of hyaluronidase-labile, DI material in coated, endocytic-like vesicles and caveolae also suggested potential modification or conditioning of the matrix by migrating mesenchymal cells. Altogether, the study established loci in developing cushions where disruption where disruption of the developmental sequence could engender valvular or septal defects.
利用组织学方法（对活的未固定组织使用诺马斯基微分干涉光学显微镜）、超微结构方法（扫描电子显微镜和透射电子显微镜）、细胞化学方法（使用酸化透析铁作为聚阴离子物质的可视化探针）以及放射自显影方法（使用³⁵S），研究鸡和大鼠的心内膜垫（心脏间充质），以阐明间充质的起源、导致垫形成的形态学序列以及迁移的间充质细胞是否分泌硫酸化糖胺聚糖。两种物种的垫形成过程相似。间充质细胞最初出现在16至18体节胚胎中，位于未来房室管和流出道的内皮（缺乏基膜）下方。垫间充质细胞的细胞质在结构上与内皮相似；这些细胞可能起源于内皮的增殖。“播种”细胞中的有丝分裂图也很多。垫细胞最初通过桥粒附着在内皮上，但获得了运动装置（含有微管和微丝束的伪足和丝状伪足）。对不同发育阶段（20至44体节）的胚胎进行连续切片显示出离心迁移方向。细胞突起与细胞外基质的相互作用表明后者被用作迁移底物。垫细胞的楔形前缘与心肌接触并未导致细胞结构或有丝分裂活性的改变。透明质酸酶敏感的透析铁（DI）沉淀物在250纳米高尔基体泡中的定位以及垫细胞上透明质酸酶敏感的³⁵S产生的银颗粒表明该组织向基质贡献了硫酸化大分子。透明质酸酶不稳定的DI物质在有被的、内吞样小泡和小窝中的定位也表明迁移的间充质细胞可能对基质进行修饰或预处理。总之，该研究确定了发育中的垫中的位点，在这些位点发育序列的破坏可能导致瓣膜或间隔缺损。
