Noden D M
Department of Anatomy, NY State College of Veterinary Medicine, Cornell University, Ithaca 14853.
Development. 1991 Apr;111(4):867-76. doi: 10.1242/dev.111.4.867.
Outflow tract endocardium links the atrioventricular lining, which develops from cardiogenic plate mesoderm, with aortic arches, whose lining forms collectively from splanchnopleuric endothelial channels, local endothelial vesicles, and invasive angioblasts. At two discrete sites, outflow tract endocardial cells participate in morphogenetic events not within the repertoire of neighboring endocardium: they form mesenchymal precursors of endocardial cushions. The objectives of this research were to document the history of outflow tract endocardium in the avian embryo immediately prior to development of the heart, and to ascertain which, if any, aspects of this history are necessary to acquire cushion-forming potential. Paraxial and lateral mesodermal tissues from between somitomere 3 (midbrain level) and somite 5 were grafted from quail into chick embryos at 3-10 somite stages and, after 2-5 days incubation, survivors were fixed and sectioned. Tissues were stained with the Feulgen reaction to visualize the quail nuclear marker or with antibodies (monoclonal QH1 or polyclonals) that recognize quail but not chick cells. Many quail endothelial cells lose the characteristic nuclear heterochromatin marker, but they retain the species-specific epitope recognized by these antibodies. Precursors of outflow tract but not atrioventricular endocardium are present in cephalic paraxial and lateral mesoderm, with their greatest concentration at the level of the otic placode. Furthermore, the ventral movement of individual angiogenic cells is a normal antecedent to outflow tract formation. Cardiac myocytes were never derived from grafted head mesoderm. Thus, unlike the atrioventricular regions of the heart, outflow tract endocardial and myocardial precursors do not share a congruent embryonic history. The results of heterotopic transplantation, in which trunk paraxial or lateral mesoderm was grafted into the head, were identical, including the formation of cushion mesenchyme. This means that cushion positioning and inductive influences must operate locally within the developing heart tubes.
流出道内膜将起源于心源性板中胚层的房室内膜与主动脉弓连接起来，主动脉弓的内膜共同由脏壁内皮通道、局部内皮小泡和成血管细胞侵入形成。在两个离散的部位，流出道内膜细胞参与了相邻内膜所不具备的形态发生事件：它们形成了心内膜垫的间充质前体。本研究的目的是记录鸡胚心脏发育前流出道内膜的发育历程，并确定该历程中的哪些方面（如果有的话）对于获得形成心垫的潜能是必要的。在3 - 10体节期，将来自鹌鹑体节3（中脑水平）和体节5之间的轴旁和外侧中胚层组织移植到鸡胚中，孵育2 - 5天后，将存活的胚胎固定并切片。组织用福尔根反应染色以显示鹌鹑核标记，或用识别鹌鹑而非鸡细胞的抗体（单克隆QH1或多克隆抗体）染色。许多鹌鹑内皮细胞失去了特征性的核异染色质标记，但它们保留了这些抗体识别的物种特异性表位。流出道而非房室内膜的前体存在于头部轴旁和外侧中胚层，在耳板水平浓度最高。此外，单个血管生成细胞的腹侧运动是流出道形成的正常前期过程。心肌细胞从未来源于移植的头部中胚层。因此，与心脏的房室区域不同，流出道内膜和心肌前体没有共同一致的胚胎发育历程。将躯干轴旁或外侧中胚层移植到头部的异位移植结果相同，包括形成心垫间充质。这意味着心垫的定位和诱导影响必须在发育中的心脏管内局部起作用。
