GRIMLEY P M, EDWARDS G A
J Biophys Biochem Cytol. 1960 Oct;8(2):305-18. doi: 10.1083/jcb.8.2.305.
The fine structure of desmosomes and intercalated discs in the toad heart is discussed. A definite relationship between the dense components of these structures and the dense region of the Z band is demonstrated. The dense region of the Z band characteristically widens at its approach to the plasma membrane, and often terminates beneath it in a distinct discoidal plaque. Cardiac desmosomes appear to be structures which result from the intimate apposition of plaques of Z band material. These desmosomes retain the Z band function as sites of attachment for myofilaments. The suggestion is made that rotation of a desmosome through 90 degrees and splitting of filaments from the adjacent sarcomere could result in the formation of a simple step-like intercalated disc. Intermediate stages in this process are illustrated. Complex discs present in the toad probably represent the alignment of groups of simple discs produced by contractile forces. Possible physiologic functions of the disc and desmosome are discussed. Other morphologic features of toad cardiac cells include a distinct amorphous outer coat to the sarcolemma, a prominent N band, and a granular sarcoplasm with poorly developed reticulum.
本文讨论了蟾蜍心脏中桥粒和闰盘的精细结构。这些结构的致密成分与Z带的致密区域之间存在明确的关系。Z带的致密区域在靠近质膜处通常会变宽，并常常在其下方终止于一个明显的盘状斑。心脏桥粒似乎是由Z带物质的斑块紧密并置而形成的结构。这些桥粒保留了Z带作为肌丝附着位点的功能。有人提出，桥粒旋转90度并从相邻肌节分裂出细丝可能导致形成简单的阶梯状闰盘。文中展示了这一过程的中间阶段。蟾蜍中存在的复杂闰盘可能代表了由收缩力产生的简单闰盘群的排列。文中还讨论了闰盘和桥粒可能的生理功能。蟾蜍心肌细胞的其他形态学特征包括肌膜有一层明显的无定形外层、一个突出的N带以及一个内质网发育不良的颗粒状肌浆。
