Gauthier G F
J Cell Biol. 1979 Aug;82(2):391-400. doi: 10.1083/jcb.82.2.391.
In a fast-twitch muscle, three types of fibers (red, intermediate, and white) can be distinguished on the basis of mitochondrial content. Red fibers, identified by abundant mitochondria, can be further differentiated on the basis of a positive or negative response to antibodies specific for white ("fast") myosin. Because there is also a difference in Z-line width among fibers of the same muscle, the possibility existed that the two red fibers, which differ in type of myosin, might also differ in dimensions of the Z line. We therefore examined, with the electron microscope, fibers which had been exposed to antibody against white myosin. In those fibers which react with the antibody, an electron-opaque band is evident in the H-band region, thereby distinguishing reactive from unreactive fibers. The red fiber can now be subdivided on the basis of a positive or negative response to anti-white myosin visualized directly with the electron microscope. Both categories of red fibers ("fast" and "slow") have wide Z lines, and thus are distinguished from white and intermediate fibers, which react with the antibody but which have narrow Z lines. On the basis of combined immunocytochemical and ultrastructural characteristics, four types of fibers can be recognized in a single muscle. Moreover, it is demonstrated here that a wide Z line does not necessarily imply a slow speed of contraction.
在快肌中，可根据线粒体含量区分出三种类型的纤维（红色、中间型和白色）。红色纤维因含有丰富的线粒体而得以识别，还可根据其对白色（“快”）肌球蛋白特异性抗体的阳性或阴性反应进一步区分。由于同一块肌肉中的纤维在Z线宽度上也存在差异，因此存在这样一种可能性，即两种肌球蛋白类型不同的红色纤维在Z线尺寸上也可能不同。因此，我们用电子显微镜检查了暴露于抗白色肌球蛋白抗体的纤维。在那些与抗体发生反应的纤维中，H带区域会出现一条电子致密带，从而区分出反应性纤维和非反应性纤维。现在，红色纤维可根据其对用电子显微镜直接观察到的抗白色肌球蛋白的阳性或阴性反应进行细分。两类红色纤维（“快”和“慢”）都有较宽的Z线，因此与白色和中间型纤维不同，后两者与抗体发生反应但Z线较窄。根据免疫细胞化学和超微结构特征的综合结果，在一块肌肉中可识别出四种类型的纤维。此外，本文还证明，较宽的Z线不一定意味着收缩速度慢。
