Tokuyasu K T
Department of Biology, University of California at San Diego, La Jolla 92093.
J Cell Biol. 1989 Jan;108(1):43-53. doi: 10.1083/jcb.108.1.43.
To study whether the first myofibrils are separate from or firmly bound to the myocytic cell membranes, whole mount preparations of 6-12-somite-stage chick embryonic hearts were examined by fluorescence microscopy after double labeling with antibodies to vinculin (fluorescein-conjugated) and rhodamine-phalloidin, or with antibodies to titin (rhodamine-conjugated) and nitrobenz-oxadiazole-phallacidin. When a small number of myofibrils appeared for the first time at the nine somite stage, most of them were already bound to the cell membranes through zonulae adherentes, fasciae adherentes, or costameres. In the outer of the two myocardial cell layers, in which the myocytes were closely in contact with each other along polygonal boundaries, fasciae adherentes and costameres developed at the boundaries, apparently by conversion of preexisting zonulae adherentes. On the other hand, in the inner cell layer, in which myocytes were more loosely associated with each other, both costameres and fasciae adherentes appeared to develop de novo, the former in association with the inner surface of the myocardial wall and the latter at the intercellular boundaries. The myofibrillar tracks in the inner layer followed long and smooth courses and were as a whole aligned in the circumferential direction of the tubular heart wall from the earliest stage of myofibril formation. Those in the outer layer were arranged in a pattern of two- or three-dimensional networks in the 9-10 somite stage, although many myofibrils were also circumferentially directed. The fact that the majority of the first myofibrils were already bound to the cell membranes in a directed manner suggests that myocytes at the earliest stage of myofibril formation are endowed with spatial information that directs the organization of nascent myofibrils. It is proposed that the myocyte cell membranes perform an essential role in cardiac myofibrillogenesis.
为了研究最初的肌原纤维是与心肌细胞膜分离还是紧密相连，我们用抗纽蛋白（荧光素偶联）抗体和罗丹明 - 鬼笔环肽，或用抗肌联蛋白（罗丹明偶联）抗体和N - 羟基琥珀酰亚胺 - 鬼笔环肽对6至12体节期鸡胚心脏的整装标本进行双重标记后，通过荧光显微镜检查。当在九体节期首次出现少量肌原纤维时，它们中的大多数已经通过黏着小带、黏着斑或肌小节附着于细胞膜。在两层心肌细胞的外层，心肌细胞沿多边形边界彼此紧密接触，黏着斑和肌小节在边界处形成，显然是由先前存在的黏着小带转变而来。另一方面，在细胞内层，心肌细胞彼此联系较为松散，肌小节和黏着斑似乎都是重新形成的，前者与心肌壁的内表面相关，后者在细胞间边界处形成。内层的肌原纤维轨迹长且平滑，从肌原纤维形成的最早阶段起就整体沿管状心脏壁的圆周方向排列。在9至10体节期，外层的肌原纤维呈二维或三维网络模式排列，尽管许多肌原纤维也是沿圆周方向排列的。大多数最初的肌原纤维已经以定向方式与细胞膜相连，这一事实表明，在肌原纤维形成的最早阶段，心肌细胞就具备指导新生肌原纤维组织形成的空间信息。有人提出，心肌细胞膜在心肌肌原纤维生成中起着至关重要的作用。
