Mateu L, Luzzati V, Villegas G M, Borgo M, Vargas R
Centro de Biofísica y Bioquímica IVIC, Caracas, Venezuela.
J Mol Biol. 1992 Jul 20;226(2):535-48. doi: 10.1016/0022-2836(92)90965-m.
Sequences of 15 minute X-ray scattering spectra were recorded with rat sciatic and optic nerves, superfused with tetracaine-containing Ringer solutions. The spectra were analysed using the algorithm advocated in this series of papers. The main results, as a function of the time of exposure to tetracaine, were: the mean value of the repeat distance increases; its variance decreases; the average number of membrane pairs per coherent domain decreases; the fraction of isolated membrane pairs increases. Eventually, the spectra were observed to give way to the continuous intensity curve of a single, isolated membrane pair. At all stages of the experiment the continuous intensity curves were found to differ from one type of nerve to the other, and to be invariant, for each type of nerve, with respect to the tetracaine treatment. The X-ray scattering study clearly identified the nature of the structural differences between the two types of myelin sheaths: in that of native sciatic nerves, packing disorder preferentially affects the cytoplasmic space of the membrane pair, and tetracaine disrupts the packing in that space; in the myelin of optic nerves it is the external space that is preferentially affected by packing disorder and disrupted by tetracaine. The time-course of the structure parameters showed that, at any stage of the experiment, tetracaine acts preferentially on the more highly disordered regions of the structure and totally disrupts them. These results corroborate earlier conclusions reported in the previous papers of this series. An electron microscope study was also performed on tetracaine-treated nerves: the results, in close agreement with those of the X-ray scattering study, neatly confirm the conclusions given above. In a more general way, the remarkable agreement between the results of the analysis of the X-ray scattering spectra and the electron microscope observations strongly supports the validity of the physical model used in this series of papers and the correctness of the mathematical treatment that we advocate. Finally, the relations between this work and the work of others are discussed. It must be stressed that the present work bears on the toxic rather than on the anaesthetic effects of tetracaine.
用含丁卡因的林格氏液灌流大鼠坐骨神经和视神经，记录15分钟X射线散射光谱序列。使用本系列论文中提倡的算法对光谱进行分析。作为丁卡因暴露时间的函数，主要结果如下：重复距离的平均值增加；其方差减小；每个相干域中膜对的平均数量减少；孤立膜对的比例增加。最终，观察到光谱让位于单个孤立膜对的连续强度曲线。在实验的所有阶段，发现连续强度曲线因神经类型而异，并且对于每种神经类型，相对于丁卡因处理是不变的。X射线散射研究清楚地确定了两种髓鞘结构差异的性质：在天然坐骨神经中，堆积紊乱优先影响膜对的细胞质空间，丁卡因破坏该空间中的堆积；在视神经髓鞘中，优先受堆积紊乱影响并被丁卡因破坏的是外部空间。结构参数的时间进程表明，在实验的任何阶段，丁卡因优先作用于结构中更高度无序区域并使其完全破坏。这些结果证实了本系列前几篇论文中报道的早期结论。还对丁卡因处理的神经进行了电子显微镜研究：结果与X射线散射研究的结果密切一致，有力地证实了上述结论。更一般地说，X射线散射光谱分析结果与电子显微镜观察结果之间的显著一致性有力地支持了本系列论文中使用的物理模型的有效性以及我们提倡的数学处理的正确性。最后，讨论了这项工作与其他人工作的关系。必须强调的是，目前的工作涉及丁卡因的毒性而非麻醉作用。
