Latour L L, Svoboda K, Mitra P P, Sotak C H
Department of Biomedical Engineering, Worcester Polytechnic Institute, MA 01609.
Proc Natl Acad Sci U S A. 1994 Feb 15;91(4):1229-33. doi: 10.1073/pnas.91.4.1229.
Packed erythrocytes are ideally suited as a model system for the study of water diffusion in biological tissue, because cell size, membrane permeability, and extracellular volume fraction can be varied independently. We used a pulsed-field-gradient spin echo NMR technique to measure the time-dependent diffusion coefficient D(t) in packed erythrocytes. The long-time diffusion constant, D(eff), depends sensitively on the extracellular volume fraction. This may explain the drop in D(eff) during the early stages of brain ischemia, where just minutes after an ischemic insult the extra-cellular volume in the affected region of the brain is significantly reduced. Using an effective medium formula, we estimate the erythrocyte membrane permeability, in good agreement with measurements on isolated cells. From the short-time behavior of D(t), we determine the surface-to-volume ratio of the cells, approximately (0.72 micron)-1.
浓缩红细胞是研究生物组织中水扩散的理想模型系统，因为细胞大小、膜通透性和细胞外体积分数可以独立变化。我们使用脉冲场梯度自旋回波核磁共振技术来测量浓缩红细胞中随时间变化的扩散系数D(t)。长时间扩散常数D(eff)对细胞外体积分数敏感。这可能解释了脑缺血早期D(eff)的下降，在缺血损伤后几分钟，脑受影响区域的细胞外体积显著减少。使用有效介质公式，我们估算了红细胞膜通透性，与对分离细胞的测量结果吻合良好。从D(t)的短时间行为，我们确定了细胞的表面积与体积比，约为(0.72微米)-1。
