Analysis of Blood Flow Dynamics in Cerebral Microvessels by a fiber-Optic Laser-Doppler Anemometer Microscope

光纤激光多普勒风速计显微镜分析脑微血管血流动力学

基本信息

批准号：
08671627
负责人：
SEKI Junji
金额：
$ 1.41万
依托单位：
National Cardiovascular Center Research Institute
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

This research projecto was aimed to analyze the blood flow dynamics undr the various pathological conditions using our developed fiber-optic laser-Doppler anemometer microscope (FLDAM). In particular, effects of incresed intracranial pressure on the pulse wave propagation along the pial arteriolar network and effects of nitric oxide on the velocity distributions in the pial microvessels were studied.To observe the brain pial microcirculation, a closed cranial window was created on the parietal region of the rats. The red cell velocity in single pial microvessels was measured by the FLDAM.The internal pressure of the window, which is equal to the intracranial pressure, was changed between 0 and 50 mmHg. The red cell velocity in arterioles showed regular pulsatile waveforms synchronous with the systemic arterial pressure measured in the femoral artery. The amplitude of velocity pulsation was defined as the half of the difference between the maximum and minimum of the ensemble average vel … More ocity using the systemic pressure as a timing signal. The amplitude of velocity pulsation in the pial arterioles was 24 (]SY.+-。[) 9%, 29 (]SY.+-。[) 9% and 40 (]SY.+-。[) 11% at ICP = 5,30 and 50 mmHg, respectively. It increased gradually with ICP on the average. In individual arterioles, however, the amplitude of velocity pulsation showed a sharp increase at a certain critical value of ICP.The critical ICP ranged between 25 and 40 mmHg, increased with increasing vessel diameter and decreased from upstream to downstream along arteriolar trees. Theoretical calculations wereconducted based on a model assuming that the elastic modulus of arteriolar wall is a step function of transmural pressure and the network architecture is approximated by a porous tapered elastic tube. They suggest that the critical ICP corresponds to the internal pressure of the arteriole.Constant shear stress hypothesis has been introduced to explain the cubic dependence of the volumetric flow in arterioles on vessel diameter. The mechanism of the hypothesis is based on the flow dependent vasodilation mediated by nitric oxide (NO). However, our measurements by the FLDAM revealed that the flow rate in the rat pial arterioles is proportional to the 3.46 (]SY.+-。[) 0.18<@D2-@>D2th power of the diameter, which is significantly different from 3. To investigate the effects of NO on the velocity distribution, the red cell velocity was measured in the pial arterioles with diameter between 20 and 60 mum under the infusion of sodium nitoprusside (SNP,a potent NO donor). Both diamete and mean velocity increased by 14% on the average. The distributions of mean velocity and wall shear rate did not show significant changes compared to the control condition. Less

该研究项目旨在使用我们开发的光纤激光多普勒风速计显微镜（FLDAM）分析各种病理条件下的血流动力学，特别是颅内压升高对沿软脑膜小动脉网络的脉搏波传播的影响。研究一氧化氮对软脑膜微血管速度分布的影响。为了观察脑软膜微循环，在软脑膜上创建一个封闭的颅窗。通过FLDAM测量大鼠顶叶区域的单个软脑膜微血管中的红细胞速度。窗口的内部压力(等于颅内压)在0至50mmHg之间变化，显示小动脉中的红细胞速度。与股动脉中测量的全身动脉压同步的规则脉动波形速度脉动的幅度被定义为系综的最大值和最小值之差的一半。使用全身压力作为定时信号的平均速度脉动幅度为 24 (]SY.+-。在 ICP = 5.30 和 50 mmHg 时，分别为 [) 9%、29 (]SY.+-.[) 9% 和 40 (]SY.+-.[) 11% 平均随着 ICP 逐渐增加。然而，在单个小动脉中，速度脉动的幅度在 ICP 的某个临界值处表现出急剧增加。临界 ICP 范围在 25 至 40 mmHg 之间，随着 ICP 的增加而增加。他们提出，基于假设小动脉壁的弹性模量是跨壁压力的阶跃函数并且网络结构由多孔锥形弹性管近似的模型进行了理论计算。临界ICP对应于小动脉的内部压力。引入恒定剪切应力假设来解释小动脉中的体积流量对血管直径的立方依赖性。该假设基于一氧化氮 (NO) 介导的流量依赖性血管舒张。然而，我们通过 FLDAM 进行的测量表明，大鼠软脑膜小动脉的流量与 3.46 (]SY.+- 成正比。 [) 0.18<@D2-@>直径的D2次方，与3显着不同。为了研究NO对速度分布的影响，测量了直径在20至60μm之间的软脑膜小动脉中的红细胞速度在注射硝普钠（SNP，一种有效的NO供体）的情况下，直径和平均速度平均增加了14%，但平均速度和壁剪切率的分布没有变化。与对照条件相比显示出显着变化。