Johnson E A, Sommer J R
J Cell Biol. 1967 Apr;33(1):103-29. doi: 10.1083/jcb.33.1.103.
The structure of a small strand of rabbit heart muscle fibers (trabecula carnea), 30-80 micro in diameter, has been examined with light and electron microscopy. By establishing a correlation between the appearance of regions of close fiber contact in light and electron microscopy, the extent and distribution of regions of close apposition of fibers has been evaluated in approximately 200 micro length of a strand. The distribution of possible regions of resistive coupling between fibers has been approximated by a model system of cables. The theoretical linear electrical properties of such a system have been analyzed and the implications of the results of this analysis are discussed. Since this preparation is to be used for correlated studies of the electrical, mechanical, and cytochemical properties of cardiac muscle, a comprehensive study of the morphology of this preparation has been made. The muscle fibers in it are distinguished from those of the rabbit papillary muscle, in that they have no triads and have a kind of mitochondrion not found in papillary muscle. No evidence of a transverse tubular system was found, but junctions of cisternae of the sarcoplasmic reticulum and the sarcolemma, peripheral couplings, were present. The electrophysiological implications of the absence of transverse tubules are discussed. The cisternae of the couplings showed periodic tubular extensions toward the sarcolemma. A regularly spaced array of Z line-like material was observed, suggesting a possible mechanism for sarcomere growth.
对一小段直径为30 - 80微米的兔心肌纤维束（肉柱）结构进行了光学显微镜和电子显微镜检查。通过建立光学显微镜和电子显微镜下纤维紧密接触区域外观之间的相关性，在约200微米长的纤维束中评估了纤维紧密并列区域的范围和分布。纤维之间电阻耦合可能区域的分布已通过电缆模型系统进行了近似。分析了该系统的理论线性电学性质，并讨论了该分析结果的意义。由于该标本将用于心肌电、机械和细胞化学性质的相关研究，因此对该标本的形态进行了全面研究。其中的肌纤维与兔乳头肌的肌纤维不同，在于它们没有三联体，且有一种在乳头肌中未发现的线粒体。未发现横管系统的证据，但存在肌浆网池与肌膜的连接，即周边连接。讨论了缺乏横管所产生的电生理意义。连接池向肌膜呈现出周期性的管状延伸。观察到了规则排列的类似Z线的物质，提示了肌节生长的一种可能机制。
