Assaf Y, Cohen Y
School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
NMR Biomed. 1999 Oct;12(6):335-44. doi: 10.1002/(sici)1099-1492(199910)12:6<335::aid-nbm581>3.0.co;2-a.
1H NMR diffusion experiments performed on the signal of the metabolites in bovine optic nerve showed that the signal decay due to diffusion is bi-exponential with a slow and a fast diffusing component. Diffusion was measured as a function of the diffusion time, and the data were analyzed as a function of b and q values. Bi-exponential fit was used to analyze the data, and the results were compared with the displacement distribution profiles obtained from the q-space analysis of the data. This q-space analysis showed that the fast diffusing component has a broad displacement distribution and appears not to be restricted. On the other hand, the slow diffusing component appears to be highly restricted to milieu in the order of 1-2 microm. The orientation of the sample with respect to the axis for which diffusion was measured affected mainly the relative sizes of the populations of each component, but had only a small effect on the extracted apparent diffusion coefficients. These results from both the b and the q value analyses suggest that the slow diffusing component is related to restricted diffusion of these metabolites in the axonal fibers, while the fast diffusing component represents diffusion of metabolites in cells and along the long axis of the nerve fibers. It is concluded that q-space analysis of metabolite diffusion enables extraction of structural information about the sample, and that the diffusion of the metabolites in optic nerve is dictated mainly by the cellular medium and microstructure of the tissue.
对牛视神经中代谢物信号进行的1H NMR扩散实验表明，由于扩散导致的信号衰减呈双指数形式，具有慢扩散成分和快扩散成分。测量扩散随扩散时间的变化，并将数据作为b值和q值的函数进行分析。使用双指数拟合分析数据，并将结果与从数据的q空间分析获得的位移分布轮廓进行比较。这种q空间分析表明，快扩散成分具有较宽的位移分布，似乎不受限制。另一方面，慢扩散成分似乎高度局限于1-2微米量级的环境中。样品相对于测量扩散的轴的取向主要影响每个成分群体的相对大小，但对提取的表观扩散系数影响较小。来自b值和q值分析的这些结果表明，慢扩散成分与这些代谢物在轴突纤维中的受限扩散有关，而快扩散成分代表代谢物在细胞中以及沿神经纤维长轴的扩散。得出的结论是，代谢物扩散的q空间分析能够提取有关样品的结构信息，并且视神经中代谢物的扩散主要由组织的细胞介质和微观结构决定。
