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为进一步阐明短期失重下血管的适应性改变及其重力性对抗措施的机理,本文对3d模拟失重组(SUS)、对抗措施组(STD,每日恢复正常站立体位1h模拟-Gx重力)及对照组(CON)大鼠大脑中动脉和肠系膜第三级小动脉的被动和主动生物力学特性进行了分析。所研究的生物力学参数包括:被动血管的表观刚度(β)、被动和主动血管的周向应力(σθ)-应变(εθ)关系及其增量弹性模量(Einc,p),和平滑肌收缩活动所致的激活增量弹性模量(Einc,a)。主动血管生物力学特性分析结果显示,肌源性紧张度的调节对失重下血管的适应具有重要意义:(1)SUS组肠系膜第三级小动脉的主动σθ-εθ曲线与其被动态曲线基本一致,表明通过肌紧张度调节使σθ恢复正常的功能基本丧失;但每日1h的-Gx重力暴露则可完全防止此功能减退;(2)SUS组大脑中动脉的主动σθ-εθ曲线较其被动曲线明显左移,不同压力下εθ始终相对稳定,σθ也趋于正常;且每日短时-Gx重力不能防止这种功能亢进。另一方面,对被动血管生物力学特性的分析则提示,不同血管的间质成分可能有不同重塑(remodeling)变化,如失重暴露时间进一步延长,将可能观察到有显著意义的重要变化。总之,本文血管生物力学特性分析对阐明失重环境下血管适应机理及其重力性对抗措施具有重要意义。
In order to further elucidate the adaptive changes of blood vessels and the mechanism of their gravitational countermeasures under short-term weightlessness, this study investigated the effects of 3-D simulated weightlessness (SUS), countermeasures group (STD, 1h simulated daily normal standing position-Gx gravity) The passive and active biomechanical properties of the middle cerebral artery and the third grade mesenteric artery of rats in CON group were analyzed. The biomechanical parameters studied included the apparent stiffness of passive blood vessels (β), the relationship between the circumferential stress (σθ) and strain (εθ) of passive and active vessels and their elastic modulus of elasticity (Einc, p), and smooth muscle The contractile activity-induced increase in elastic modulus (Einc, a). The analysis of active biomechanical properties showed that the modulation of myogenic tone was important for the adaptation of blood vessels under weightlessness: (1) The active sigma-ε-εθ curve of the third grade arterioles in SUS group was basically the same as that of the dynamic curve, The results showed that the function of normalizing σθ was basically lost through the regulation of muscle tone; however, the daily exposure to -Gx at 1h could completely prevent the decline of this function. (2) The active σθ-εθ curve of middle cerebral artery in SUS group was less than that of passive curve Obviously left shift, εθ is always relatively stable under different pressures, and σθ also tends to be normal; and short daily-Gx gravity can not prevent this kind of hyperthyroidism. On the other hand, analysis of the biomechanical properties of passive blood vessels suggests that there may be different remodeling changes in the interstitial components of different blood vessels. Significant and significant changes may be observed if exposure to weightlessness is further prolonged. In conclusion, the analysis of biomechanical properties of blood vessels in this paper is of great significance for elucidating the mechanism of vascular adaptation under weightlessness and its gravitational countermeasures.