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Changes in Compliance of Femoral Vein after Simulated Weightlessness in Rabbits with Histomorphology Correlation

Author: YueYong
Tutor: ZhuQingSheng；SunXiQing
School: Fourth Military Medical University
Course: Surgery
Keywords: Weightlessness Simulated weightlessness Head down to -20 tilt Orthostatic intolerance Rabbits Femoral vein Microstructure Ultrastructure Compliance Stress - strain relations Pressure - volume relation Tensile test In vivo measurement
CLC: R85
Type: Master's thesis
Year: 2003
Downloads: 48
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Abstract

Post-flight orthostatic intolerance (the Orthostatic Intolerance OI) is a major manifestation of cardiovascular dysfunction in space weightlessness. Space weightlessness caused by orthostatic intolerance decline will affect the security in the process of completion and return of astronauts space mission, and with the development of space technology in the process of manned space flight, the astronauts will experience long-term weight loss after landing on other planets, overcome or reduce the decline due to orthostatic intolerance threat to the safety of the astronauts, all the more urgent and important, the research has also been national researchers' attention. Orthostatic poor endurance of the mechanism still do not quite understand, now known single factor is difficult to explain the decline of orthostatic intolerance, its occurrence involves changes in venous compliance, changes in cardiac function, blood volume / loss of body fluids changes in the endocrine system, and baroreflex reactivity and other factors. Generally believed: weight loss / lower extremity venous compliance increase after simulated weightlessness, there is more blood in the venous vascular compliance enables high retention to stay in the venous system, thy blood less, leading to the decline in cardiac output and arterial blood pressure, and promote legislation occurrence bit Stamina adverse. But at this stage weight loss / to simulated weightlessness the static mouth Military Medical University's degree, a pulse compliance impact findings are not consistent, most researchers believe that: weightlessness or simulated weightlessness, venous compliance is increased [2]. . Seen in this light, the venous compliance changes and influencing factors are still not clear. We believe that the reason for this difference comes from the venous compliance measurement methods are not uniform. In bedridden experiments and flight practice are used to measure lower limb volume changes to reflect changes in venous compliance, and lower limb volume change is determined by several factors, not only the venous system, as well as muscle and tissue fluid, etc., can not be a true reflection of the changes in venous compliance. In this study, head down to -20 \explore the reasons purebred New Zealand rabbits were divided into control group, 10 days of simulated weightlessness group that HDT10d) and simulated weightlessness ZI day group that HDTZI D) (n = 8). () in the body femoral vein pressure - volume relation (ie PN Relations) measurement technique to observe IIAlxTI cd P.V relations and HDTZld rabbit femoral vein curve to study the compliance changes simulated weightlessness duration venous compliance changes the relationship between: (2) on isolated rabbit body femoral vein axial and hoop stress strain relationships are measured to understand the trends of the femoral vein in the conditions of weightlessness stress - strain relationship, further study of simulated weightlessness on venous compliance the impact of (3) using light and electron microscopy to observe the ID3T10d, HDTZld rabbit femoral vein microscopic and ultrastructural changes, changes in biomechanical properties in order to study the femoral vein tissue morphological basis for the main results of this work as follows: l after simulated weightlessness rabbit femoral vein Bu-V relationship curve mobile, knife-day group compared with 10 days group changes more obvious. compared with the control group, P-V curve of the femoral vein to the volume change ratio after simulated weightlessness the direction of increasing mobile simulate weightlessness the ZI day group compared with 10 days group moved more obvious. loaded, unloaded, group 21 days of simulated weightlessness. turns - 3 - Fourth Army Kuang University Gu degree on the husband a BU V secondary parabolic equation coefficients; the value of S were significantly higher than control group and the simulated weightlessness O days group (P <0.01), simulated weightlessness 10-day group B; in value compared to the control group, there is an increasing trend. 2, the femoral vein in rabbits after simulated weightlessness stress - strain relationship changes under the same stress, the axis of the HDTZld, and HDT cd group ring to the loading and unloading deformation than the control group a significant increase in, and HDTZId group than the HDT 10 d group remained significant increased femoral vein axis, the hoop stress - strain curve move toward venous specimen elongation ratio of the number of 3, the simulated weightlessness can cause the rabbit femoral vein wall histological changes. the HDT10d group, part of endothelial cells was flat, arranged in irregular, loose binding cells, some endothelial cells off; organelles reduce visible phagolysosomes and vacuolar degeneration of mitochondria steep disappeared or was short rod; thinning of the internal elastic lamina and fracture; smooth muscle layer change thin. HDTZId group, endothelial cells were round or short columnar, irregular arrangement of cells binding looser, a large number of endothelial cells fall off, the decrease in cell nucleus was irregular, vacuolar degeneration and phagocytic vesicles increased significantly, mitochondria reduce, irregular shape, valley disappear. internal elastic lamina expansion and fracture; smooth muscle layer is thin, in part by the contraction transition secretory and smooth muscle cell degeneration; interstitial widening smooth muscle cells, increased collagen fibers, elastic fibers rare. Conclusions: The simulated weightlessness rabbit femoral vein structure, biomechanical properties and functions are changing, and simulate the weightlessness the longer, the more obvious the change, changes in organizational structure of the vein wall may be the nature and function of the venous biomechanics change the basis of its biomechanical properties and functional changes may be one of the reasons for the decline of orthostatic intolerance after weight loss / simulated weightlessness.

Changes in Compliance of Femoral Vein after Simulated Weightlessness in Rabbits with Histomorphology Correlation

Abstract

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