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

在基础研究的基础上，从微循环水平全面研究了血液流量和血液流变学因素对氧向脑转运和脑活动的影响。(1)微血管中的红细胞流量与主动脉的流量成正比。血液的氧合状态与血液流动状况密切相关。(2)红细胞的流变学性质对O_2释放的影响与O_2在红细胞及周围环境中的扩散距离有关。(3)血液的氧合-去氧过程通过依赖于pH/CO_2的红细胞形态变化来影响红细胞聚集，并在低pH和高CO_2条件下促进O_2的释放。(4)高脂膳食，甚至是暂时的，通过增加血浆中甘油三酯的浓度来促进红细胞聚集。这一现象提示了微循环障碍和动脉硬化的风险。(5)除了单个微血管的横断面图像外，还成功地构建了微血管网络中红细胞流动和氧合状态的二维图像。(6)与人工窄管中的行为相比，红细胞在微血管中的流动行为受到血管和血液流变性因素的更显著的改变。这种现象主要是由于血流通道的弹性，如血管的动脉粥样硬化改变所致。(7)通过感觉区诱发电位评价，氧通过血流向组织传递对脑内神经活动有显著影响。(8)神经元和小胶质功能之间存在体液因素的相互调控机制。

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.