Canham P B, Whittaker P, Barwick S E, Schwab M E
Department of Medical Biophysics, Health Sciences Centre, University of Western Ontario, London, Canada.
Can J Physiol Pharmacol. 1992 Feb;70(2):296-305. doi: 10.1139/y92-037.
A key factor in the contribution of collagen fibres to tissue mechanics is the alignment of the fibres, which we studied in brain arteries, focussing on alignment changes with distending pressure. Arteries from autopsy were cannulated and fixed at different distending pressures from 0 to 200 mmHg (1 mmHg = 133.32 Pa), alcohol dehydrated, paraffin embedded, sectioned, and stained for birefringent enhancement. The polarized light microscope was set for extinction and fibre orientations were precisely determined at the rotational position of extinction for 200 positions around the artery wall. Results from 22 arterial cross sections revealed, with fixation pressure, a significant but incomplete straightening of collagen (even at 200 mmHg). The mean angular deviation of alignment of fibres was +/- 30 degrees for arteries fixed at zero transmural pressure, which in contrast was +/- 7 degrees for the inner and +/- 13 degrees for the mid-adventitia for arteries fixed at 200 mmHg transmural pressure. We verified on vessels fixed at low pressure, by using a full wave plate in conjunction with the specificity of the interference colours, that the measurements were correct and not confused with angles at 90 degrees to the morphological axis. Alternative tissue processing was done with two arteries fixed at 120 mmHg and processed for frozen sections; the results showed diminished variability in alignment but within the range of measurements for wax embedded tissue. We concluded that the collagen fabric could contribute to the mechanics of brain arteries but that it would be with sinusoidal rather than straightened fibres of collagen.
胶原纤维对组织力学产生作用的一个关键因素是纤维的排列，我们在脑动脉中对此进行了研究，重点关注纤维排列随扩张压力的变化。取自尸检的动脉被插管，并在0至200 mmHg（1 mmHg = 133.32 Pa）的不同扩张压力下固定，经酒精脱水、石蜡包埋、切片，并进行双折射增强染色。将偏光显微镜设置为消光状态，并在动脉壁周围200个位置的消光旋转位置精确确定纤维方向。22个动脉横截面的结果显示，随着固定压力的增加，胶原纤维有显著但不完全的伸直（即使在200 mmHg时）。对于在零跨壁压力下固定的动脉，纤维排列的平均角度偏差为±30度，相比之下，对于在200 mmHg跨壁压力下固定的动脉，内膜的平均角度偏差为±7度，中膜外层为±13度。我们在低压固定的血管上进行了验证，通过结合全波片和干涉色的特异性，证实测量是正确的，且不会与形态轴成90度角的角度混淆。对两条在120 mmHg下固定并制成冰冻切片的动脉进行了替代组织处理；结果显示排列变异性降低，但仍在石蜡包埋组织的测量范围内。我们得出结论，胶原纤维结构可能对脑动脉的力学性能有贡献，但其中的胶原纤维是呈正弦曲线状而非伸直的。
