Lapi D, Marchiafava P L, Colantuoni A
Department of Physiology and Biochemistry, University of Pisa, Pisa, Italy.
J Vasc Res. 2008;45(1):69-77. doi: 10.1159/000109078. Epub 2007 Sep 27.
The aim of the study was to assess the geometric characteristics of rat pial microcirculation and describe the vessel bifurcation patterns by 'connectivity matrix'.
Male Wistar rats were used to visualize pial microcirculation by a fluorescent microscopy technique through an open cranial window, using fluorescein isothiocyanate bound to dextran (molecular weight 70 kDa). The arteriolar network was mapped by stop-frame images. Diameters and lengths of arterioles were measured with a computer-assisted method. Pial arterioles were classified according to a centripetal ordering scheme (Strahler method modified according to diameter) from the smallest order 1 to the largest order 5 arterioles in the preparation. A distinction between arteriolar segments and elements was used to express the series-parallel features of the pial arteriolar networks. A connectivity matrix was used to describe the connection of blood vessels from one order to another.
The arterioles were assigned 5 orders of branching by Strahler's ordering scheme, from order 1 (diameter: 16.0 +/- 2.5 microm) to order 5 (62 +/- 5.0 microm). Order 1 arterioles gave origin to capillaries, assigned order 0. The diameter, length and branching of the 5 arteriolar orders grew as a geometric sequence with the order number in accordance with Horton's law. The segments/elements ratio was the highest in order 4 and 3 arterioles, indicating the greatest asymmetry of ramifications. Finally, the branching vessels in the networks were described in details by the connectivity matrix. Fractal dimensions of arteriolar length and diameter were 1.75 and 1.78, respectively.
The geometric characteristics of rat pial microcirculation indicate that distribution of vessels is fractal. The connectivity matrix allowed us to describe the number of daughter vessels spreading from parent vessels. This ordering scheme may be useful to describe vessel function, according to diameter, length and branching.
本研究旨在评估大鼠软脑膜微循环的几何特征，并通过“连通性矩阵”描述血管分支模式。
选用雄性Wistar大鼠，通过开放颅骨窗口，采用荧光显微镜技术，使用与葡聚糖（分子量70 kDa）结合的异硫氰酸荧光素来观察软脑膜微循环。通过定格图像绘制小动脉网络。采用计算机辅助方法测量小动脉的直径和长度。根据向心排序方案（根据直径修改的斯特拉勒方法），将制备中的软脑膜小动脉从最小的1级到最大的5级进行分类。利用小动脉段和元件之间的区别来表达软脑膜小动脉网络的串并联特征。使用连通性矩阵描述从一个级别到另一个级别的血管连接。
根据斯特拉勒排序方案，小动脉被分为5个分支级别，从1级（直径：16.0±2.5微米）到5级（62±5.0微米）。1级小动脉发出毛细血管，归为0级。5个小动脉级别的直径、长度和分支按照霍顿定律以几何序列随级别数增长。段/元件比在4级和3级小动脉中最高，表明分支的不对称性最大。最后，通过连通性矩阵详细描述了网络中的分支血管。小动脉长度和直径的分形维数分别为1.75和1.78。
大鼠软脑膜微循环的几何特征表明血管分布是分形的。连通性矩阵使我们能够描述从母血管分出的子血管数量。根据直径、长度和分支，这种排序方案可能有助于描述血管功能。
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