AIM:Systemic treatment with epidermal growth factor (EGF)leads to growth of all parts of the small intestine in normal functioning rats. In this study, we investigated the effect of this growth process on morphometric...AIM:Systemic treatment with epidermal growth factor (EGF)leads to growth of all parts of the small intestine in normal functioning rats. In this study, we investigated the effect of this growth process on morphometric and biomechanical parameters of ileum.METHODS: Rats were treated with EGF (150 μg@kg-1day-1)or placebo via osmotic minipumps for 2, 4, 7, and 14 days.A segment of ileum was removed. The morphology at noload state and zero-stress state was measured and passive biomechanical properties were assessed using a biaxial test machine (combined inflation and axial stretching).RESULTS: The ileum weight increased after EGF administration. After 4 days' EGF treatment, the wall thickness was increased. Significantly smaller inner perimeters were seen in 4 day and 7 day EGF treatment groups. The opening angle and residual strain began to increase after 7 days' EGF treatment. Wall stiffness, evaluated from the stress-strain curves, showed a continuous decrease in circumferential direction during the first 7 days' EGF treatment. The longitudinal stiffness increased during the first 7 days. The stress-strain curves for both circumferential and longitudinal direction tended to shift back to normal 14days after starting EGF administration.CONCLUSION: EGF can cause significant changes both in the morphology and in the passive mechanical properties of the rat ileum.展开更多
Objective To assess the influence of mimic cardiac rate on hydrodynamics of different mechanical prosthetic cardiac valves. Methods US-made CarboMedics bileaflet valve, China-made Jiuling bileaflet valve and C-L tilti...Objective To assess the influence of mimic cardiac rate on hydrodynamics of different mechanical prosthetic cardiac valves. Methods US-made CarboMedics bileaflet valve, China-made Jiuling bileaflet valve and C-L tilting disc valve were tested via a pulsatile flow simulator in the aortic position. Testing conditions were set at mimic cardiac rates of 55 bpm, 75 bpm, 100 bpm with a constant mimic cardiac output of 4 L/min. The mean pressure differences (ΔP), leakage volumes (LEV) and closing volumes (CLV) across each valve, and effective orifice areas (EOA) were analyzed. Results Within physiological range, ΔP, LEV, and CLV decreased as mimic cardiac rate increased, with a large extent of variance. EOA increased along with an increase in mimic cardiac rate. It was a different response in terms of cardiac rate alteration for different types of mechanical prosthetic cardiac valves. Conclusion Mimic cardiac rate change affects hydrodynamics of mechanical prosthetic cardiac valves. Within physiological range, the hydrodynamic of prosthetic bileaflet valve is better than that of tilting disc valve.展开更多
Objective:To assess the influe nce of mimic cardiac rate on hydrodynamics of the different mechanical prostheti c cardiac valves.Methods:US-made CarboMedics bile aflet valve and China-made Jiuling bileafle t valve and...Objective:To assess the influe nce of mimic cardiac rate on hydrodynamics of the different mechanical prostheti c cardiac valves.Methods:US-made CarboMedics bile aflet valve and China-made Jiuling bileafle t valve and C-L tilting disc valve have been tested in a pulsatile flow simulat or in the aortic position. The testing condition was set at the mimic cardiac r ate of 55 beats/min,75 beats/min,100beats/min and a constant mimic cardiac out put of 4L/min. The mean pressure differences(ΔP),leakage volumes (LEV) and closi ng volumes(CLV) across each valve,and the effective orifice areas(EOA) have bee n analyzed.Results:Within the range of physiology, the ΔP,LEV and CLV were falling as the increasing of mimic cardiac rate,and the extent of variance was larger. The EOA was increasing with the increase of the mimic cardiac rate. It is a differe nt response as the altering of the cardiac rate for the different type of the me chanical prosthetic cardiac valves.Conclusions:The change of the mimic cardiac rate can affect the hydrodynamics of the mechanical prosthetic cardiac valves. The hydrodynamics of the bileaflet valve prosthesis is better than the tilting disc valve.展开更多
基金Karen Elise Jensens Foundation and the Danish Technical Research Council
文摘AIM:Systemic treatment with epidermal growth factor (EGF)leads to growth of all parts of the small intestine in normal functioning rats. In this study, we investigated the effect of this growth process on morphometric and biomechanical parameters of ileum.METHODS: Rats were treated with EGF (150 μg@kg-1day-1)or placebo via osmotic minipumps for 2, 4, 7, and 14 days.A segment of ileum was removed. The morphology at noload state and zero-stress state was measured and passive biomechanical properties were assessed using a biaxial test machine (combined inflation and axial stretching).RESULTS: The ileum weight increased after EGF administration. After 4 days' EGF treatment, the wall thickness was increased. Significantly smaller inner perimeters were seen in 4 day and 7 day EGF treatment groups. The opening angle and residual strain began to increase after 7 days' EGF treatment. Wall stiffness, evaluated from the stress-strain curves, showed a continuous decrease in circumferential direction during the first 7 days' EGF treatment. The longitudinal stiffness increased during the first 7 days. The stress-strain curves for both circumferential and longitudinal direction tended to shift back to normal 14days after starting EGF administration.CONCLUSION: EGF can cause significant changes both in the morphology and in the passive mechanical properties of the rat ileum.
文摘Objective To assess the influence of mimic cardiac rate on hydrodynamics of different mechanical prosthetic cardiac valves. Methods US-made CarboMedics bileaflet valve, China-made Jiuling bileaflet valve and C-L tilting disc valve were tested via a pulsatile flow simulator in the aortic position. Testing conditions were set at mimic cardiac rates of 55 bpm, 75 bpm, 100 bpm with a constant mimic cardiac output of 4 L/min. The mean pressure differences (ΔP), leakage volumes (LEV) and closing volumes (CLV) across each valve, and effective orifice areas (EOA) were analyzed. Results Within physiological range, ΔP, LEV, and CLV decreased as mimic cardiac rate increased, with a large extent of variance. EOA increased along with an increase in mimic cardiac rate. It was a different response in terms of cardiac rate alteration for different types of mechanical prosthetic cardiac valves. Conclusion Mimic cardiac rate change affects hydrodynamics of mechanical prosthetic cardiac valves. Within physiological range, the hydrodynamic of prosthetic bileaflet valve is better than that of tilting disc valve.
文摘Objective:To assess the influe nce of mimic cardiac rate on hydrodynamics of the different mechanical prostheti c cardiac valves.Methods:US-made CarboMedics bile aflet valve and China-made Jiuling bileafle t valve and C-L tilting disc valve have been tested in a pulsatile flow simulat or in the aortic position. The testing condition was set at the mimic cardiac r ate of 55 beats/min,75 beats/min,100beats/min and a constant mimic cardiac out put of 4L/min. The mean pressure differences(ΔP),leakage volumes (LEV) and closi ng volumes(CLV) across each valve,and the effective orifice areas(EOA) have bee n analyzed.Results:Within the range of physiology, the ΔP,LEV and CLV were falling as the increasing of mimic cardiac rate,and the extent of variance was larger. The EOA was increasing with the increase of the mimic cardiac rate. It is a differe nt response as the altering of the cardiac rate for the different type of the me chanical prosthetic cardiac valves.Conclusions:The change of the mimic cardiac rate can affect the hydrodynamics of the mechanical prosthetic cardiac valves. The hydrodynamics of the bileaflet valve prosthesis is better than the tilting disc valve.
