Comprehensive analyses of blood circulation, oxygen transport and neural activity in microcirculatory level of brain

在基础研究的基础上，从微循环水平上全面研究了血流量和血液流变学因素对脑氧转运和脑活动的影响。(1)微血管中的红细胞（RBC）流量与主动脉中的血流量成比例变化。血液氧合状态与血流状态密切相关。(2)用透氧细管法研究了红细胞流变学特性对氧释放的影响，并与红细胞及周围环境中氧的扩散距离有关。(3)血液充氧-去氧过程通过pH-/CO_2依赖的红细胞形态变化影响红细胞聚集，低pH和高CO_2条件下O_2释放增强。(4)高脂餐，即使是暂时的，通过增加血浆中甘油三酯浓度来增强RBC聚集。这种现象表明微循环障碍和动脉硬化的风险。(5)成功地构建了大脑皮层和肠系膜微血管网中红细胞流动和氧合状态的二维图像，以及单个微血管的横截面图像。(6)红细胞在微血管中的流动行为受血管和血液流变学因素的影响比其在人工细管中的流动行为更为显著。这种现象主要是由于流动通道的弹性，如血管的动脉粥样硬化变化。(7)感觉区诱发电位显示，O_2通过血流输送到脑组织，对脑神经活动有明显影响。(8)神经元和小胶质细胞的功能之间存在着体液因素的相互调控机制，提示脑功能受O_2传递的影响，而O_2传递不仅受血管因素的影响，还受血液流变学因素的影响。

Effects of blood flow and hemorheological factors on oxygen (O_2) transport to brain and cerebral activity were comprehensively studied in microcirculatory level, in addition to the fundamental studies.(1) Red blood cell (RBC) flow in microvessels varied in proportion to blood flow in main arteries. Close relationship between oxygenation state of blood and blood flow condition was observed.(2) Effects of theological properties of RBCs on O_2 release were demonstrated using an O_2-permeable narrow tube, in relating to O_2 diffusion distance in RBCs and the surroundings.(3) Oxygenation-deoxygenation process of blood affected RBC aggregation by pH-/CO_2-dependent shape changes of RBCs, and the enhancement of O_2 release was suggested at low pH and high CO_2 conditions.(4) High-fat meal, even temporarily, enhanced RBC aggregation by increased triglycerides concentration in blood plasma. The phenomenon suggested microcirculatory disturbances and a risk for arteriosclerosis.(5) Two-dimensional images of RBC flow and the oxygenation state in microvascular network, in addition to their cross-sectional images in single microvessels, were successfully constructed for brain cortex and mesentery.(6) Flow behavior of RBCs in microvessels was changed more strikingly by vascular and hemorheological factors, as compared to their behavior in artificial narrow tubes. The phenomena were mainly due to the elasticity of the flow channels, such as in atherosclerotic change of blood vessels.(7) Neural activity in brain was markedly influenced by O_2 transfer to the tissues through blood flow, as evaluated by evoked potential in sensory area.(8) Mutual control mechanisms by humoral factors were found between functions of neurons and microglia.In conclusion, this study strongly suggested that cerebral functions were influenced by O_2 transfer, which was modified not only by blood vessel factors, but also by hemorheological factors.