EFFECT OF HYPOXIA ON TISSUE METABOLISM. ^1H-NMR STUDY OF LACTATE METABOLISM AND CHANGES IN ^1H-NMR RELAXATION TIMES OF SKELETAL MUSCLE

1.研究了核磁共振弛豫时间与肌纤维类型的关系。该研究涉及不同类型的ICR小鼠肌肉，比目鱼肌是缓慢收缩的红色（I型）肌肉，胫骨前肌是快速收缩的白色（II型）肌肉。在90-MHz傅里叶变换NMR光谱仪（Fx 90 A，JEOL）上进行NMR测量。T_1用反转恢复法测定。采用Hahn自旋回波法测定T_2。I型和II型纤维的平均T_1值分别为1.03 * 0.03秒和1.04 * 0.02秒。两者之间无显著性差异。通过对横向磁化衰减曲线的拟合，将T_2分为快（T_<2f>）和显（T_<2s>）两个分量。Ⅱ<2f><2s>型肌纤维的T_（1/2）和T_（2/3）值均显著长于Ⅰ型肌纤维（T_<2f>（1/2）：Ⅰ型33.2 * 1.4msec，Ⅱ型34.4 * 0.9msec，p&lt;0.05; T_<2s>（1/2）：Ⅰ型67.9 * 5.3msec，Ⅱ型75.1 * 0.9msec，p&lt;0.01）。由于T_（10）与T_（10）无显著性差异， ...更多信息 T_1与组织含水量有关，不同类型肌纤维间T_2的差异可能是肌纤维大分子构象变化所致.为了测量活体肌肉的T_2，我们在自旋回波法的基础上增加了改进的深度脉冲序列。将2.0特斯拉、31厘米内径的超导磁体（BEM 250/80，大冢电子公司（Otsuka Electronics Co.））并使用2cm表面线圈。通过改变翻转角（rheta）实现光谱定位。用Fx 90 A型90 MHz傅立叶变换核磁共振仪测量了含白蛋白溶液的五层体模的T_2值，每层T_2值与测量值一致。与自旋回波法相比，我们改进的深度脉冲序列在体模第3层（10.5mm深度）获得了合适的白蛋白溶液T_2值。本文用改进的深度脉冲法在体测定了人前臂肌的T_2。T_2值较体外测量值偏短，可能造成生物组织的不均匀性.测定了乳酸盐溶液的~ 1H-NMR谱。A2.0特斯拉，31厘米口径超导磁体（BEM 250/80，大冢电子公司）并使用2cm表面的线圈。虽然应用了1，3，3，1脉冲序列来实现水抑制，但没有获得完全抑制。检测到乳酸盐光谱超过0.01 M溶液。然而，乳酸的信号强度与它们的浓度小于0.01M没有相关性。少

1. Relationship between NMR relaxation times and muscle fiber type was investigated. The study concerns different types of ICR mouse muscles, the soleus which is a slow twitch red (type I) muscle and the anterior tibialis muscle, a fast twitch white (type II) muscle. NMR measurements were performed on a 90-MHz Fourier transform NMR spectrometer (Fx90A, JEOL). T_1 was measured by the inversion recovery method. T_2 was measured by the Hahn spin-echo method. Mean T_1 values of type I and type II fiber were 1.03 * 0.03 sec and 1.04 * 0.02 sec, respectively. There was no significant difference between them. T_2 is divided into fast (T_<2f>) and show (T_<2s>) components by fitting the transverse magnetization decay curve. The T_<2f> and T_<2s> values of type II fiber were significantly longer that those of type I fiber (T_<2f>:type I 33.2 * 1.4 msec, type II 34.4 * 0.9 msec,p<0.05, T_<2s>:type I 67.9 * 5.3msec, type II 75.1 * 0.9 msec, p<0.01). Since there was no significant difference in T_ … More 1, which correlates with water content of tissues, between different types of muscle fiber, difference in T_2 may be attributed to conformational changes in macromolecules in muscle fiber.2. To measure a T_2 of muscles in vivo, we developed modified depth-pulse sequence added to spin-echo meth-od. A 2.0-Tesla, 31-cm-bore superconducting magnet (BEM 250/80,Otsuka Electronics Co.) and a 2-cm surface coil was used. Spectral localization was achieved by changing a flip angle (rheta). T_2 values obtained from each layer of five-layered phantom containing albumin solution were the same value as measured with a 90MHz Fourier trans-form NMR spectrometer (Fx90A,JEOL). Compared with spin-echo method, our modified depth-pulse sequences obtained proper T_2 values of albumin solution in 3rd layer (10.5mm-depth) of phantom. T_2 of human forearm muscle was determined with the modified depth-pulse method in vivo. The T_2 values were shorter than that of in vitro measurements, which may cause inhomogeneity of biological tissues.3. We measured ^1H-NMR spectrum of lactate solution. A2.0-Tesla, 31-cm-bore superconducting magnet (BEM250/80, Otsuka Electronics Co.) and a 2cm-surface coil was used. Although 1,3,3,1 pulse sequence was applied to achieve water suppression, complete suppression was not obtained. Lactate spectra was detected more than 0.01M solution. However, signal intensity of lactate did not correlate with their concentrations less than 0.01M. Less