Callahan D E, Deamond S F, Creasey D C, Trapane T L, Bruce S A, Ts'o P O, Kan L S
Department of Biochemistry, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205.
Magn Reson Med. 1991 Nov;22(1):68-80. doi: 10.1002/mrm.1910220108.
Responses specific to the spin-spin relaxation time (T2) have been observed in two time-dependent studies of the intracellular water in normal and transformed Syrian hamster fetal fibroblasts. At 300-MHz (7.0 T), the spin-lattice relaxation time (T1) was insensitive to several aspects of cellular physiology that produced changes in the T2 and the apparent self-diffusion coefficient (Dapp) of intracellular water. In normal cells stimulated with epidermal growth factor (EGF), T1 was insensitive to time-dependent changes detected by T2 and Dapp. In synchronized tumor cells, T1 was insensitive to cell-cycle-dependent changes detected by T2. The strongly coupled behavior of T2 and Dapp that was observed as a function of time in EGF-stimulated cells indicates that the diffusion of intracellular water through inhomogeneous local magnetic field gradients produced effects observable in T2. Conformational changes in large intracellular macromolecular assemblies such as chromatin or the cytoskeleton may alter the magnitude and inhomogeneity of local field gradients, producing responses in T2 and Dapp only.
在两项关于正常和转化的叙利亚仓鼠胎儿成纤维细胞内水的时间依赖性研究中，观察到了与自旋 - 自旋弛豫时间（T2）相关的特定响应。在300兆赫（7.0特斯拉）时，自旋 - 晶格弛豫时间（T1）对细胞生理学的几个方面不敏感，这些方面会导致细胞内水的T2和表观自扩散系数（Dapp）发生变化。在用表皮生长因子（EGF）刺激的正常细胞中，T1对通过T2和Dapp检测到的时间依赖性变化不敏感。在同步化的肿瘤细胞中，T1对通过T2检测到的细胞周期依赖性变化不敏感。在EGF刺激的细胞中观察到的T2和Dapp随时间变化的强耦合行为表明，细胞内水通过不均匀的局部磁场梯度扩散会产生在T2中可观察到的效应。细胞内大型大分子组装体（如染色质或细胞骨架）的构象变化可能会改变局部场梯度的大小和不均匀性，仅在T2和Dapp中产生响应。
