下肢动脉阻塞性病变多层螺旋CT 低剂量扫描成像初探

目的:探讨低剂量CT扫描在下肢动脉脉阻塞性病变诊断中的应用价值.方法:选择127段经DSA确诊的不同部位下肢动脉阻塞性病变行低剂量CT扫描,并采用MPR,VR,MIP等重建方法获得各下肢动脉CTA图像,将CTA图像与DSA图像的诊断结果利用统计学软件SAS8.1行加权Kappa一致性检验,检验水准为:Kaapa.系数大于0.75.结果:所得CTA图像与DSA图像诊断结果的一致性检验的kappa系数为0.8058,两种诊断结果的一致性为优.结论:采用低剂量扫描条件获得高质量的CTA图像在下肢动脉阻塞性病变的诊断上有肯定的价值.     

A molecular dynamics investigation of buckling behaviour of hydrogenated graphene

Molecular dynamics simulations have been performed to characterise the stability behaviour of graphene nanoribbons having different hydrogen coverage, subject to a uniaxial compressive load. The temperature is set at a very low value to circumvent the contribution of thermal agitations. The results show that hydrogen coverage promotes to a rapid drop in the strain of buckling onset due to the effects of easy rotation of newly unsupported sp³ bonds. Furthermore, we have also found a critical value of the hydrogen adsorption above which the declining trend in the stability behaviour of hydrogenated graphene nanoribbons is reversed.     

Pulsatile Flow Inside Moderately Elastic Arteries,Its Modelling and Effects of Elasticity

Pulsatile flow inside a moderately elastic circular conduit with a smooth expansion is studied as a model to understand the influence of wall elasticity in artery flow. The solution of the simultaneous fluid-wall evolution is evaluated by a perturbative method, where the zeroth order solution is represented by the flow in a rigid vessel; the first order correction gives the wall motion and induced flow modification without the need to solve the difficult coupled problem. Such an approach essentially assumes a locally infinite celerity, therefore it represent a good approximation for the fluid-wall interaction in sites of limited extent (branches, stenosis, aneurism, etc.), which include typical situations associated with vascular diseases. The problem is solved numerically in the axisymmetric approximation; the influence of wall elasticity on the flow and on the unsteady wall shear stress is studied in correspondence of parameters taken from realistic artery flow. Attention is posed to the role of phase difference between the incoming pressure and flow pulses.     

平板运动试验对冠心病的诊断意义

目的:探讨平板运动试验(TET)对诊断冠状动脉粥样硬化性心脏病(冠心病)的临床意义。方法:对比分析217例疑诊或临床诊断冠心病患者的平板运动试验和选择性冠状动脉造影(CAG)结果。结果:以选择性冠状动脉造影为标准,平板运动试验敏感性为68.4%,特异性为88.4%,阳性预测值为77.1%,阴性预测值为82.9%。结论:简便、易行及无创的平板运动试验是诊断冠心病的重要手段。     

The Arabidopsis trichome is an active mechanosensory switch

Trichomes (‘hair cells’) on Arabidopsis thaliana stem and leaf surfaces provide a range of benefits arising from their shape and disposition. These include tempting herbivores to sample constitutive toxins before they reach the bulk of the tissue. We asked whether, in addition, small mechanical disturbances such as an insect can make elicit signals that might help the plant respond to herbivory. We imaged, pressed and brushed trichomes in several ways, most notably with confocal microscopy of trichomes transgenically provided with apoplastic pH reporter apo‐pHusion and cytosolic Ca²⁺ reporter cameleon. In parallel, we modelled trichome wall mechanics with finite element analysis. The stimulated trichome focuses force on a pliant zone and the adjoining podium of the stalk. A buckling instability can further focus force on a skirt of cells surrounding the podium, eliciting oscillations of cytosolic Ca²⁺ and shifts in apoplastic pH. These observations represent active physiological response. Modelling establishes that the effectiveness of force focusing and buckling is due to the peculiar tapering wall structure of the trichome. Hypothetically, these active mechanosensing functions enhance toxin synthesis above constitutive levels, probably via a priming process, thus minimizing the costly accumulation of toxins in the absence of herbivore attack but assuring rapid build‐up when needed.     

Two-pore potassium channels in the cardiovascular system

Two-pore domain (K_2P) channels emerged about a decade ago and since then have been an expanding area of interest. This is because their biophysical and pharmacological properties make them good candidates to support background potassium currents and membrane potential in many cell types. There is clear evidence for TREK-1 and TASK-1 in the heart and these channels are likely to regulate cardiac action potential duration through their regulation by stretch, polyunsaturated fatty acids, pH, and neurotransmitters. TREK-1 may also have a critical role in mediating the vasodilator response of resistance arteries to polyunsaturated fatty acids, thus contributing to their protective effect on the cardiovascular system. TASK-1, on the other hand, is a strong candidate for a role in hypoxic vasoconstriction of pulmonary arteries. Many other members of the K_2P channel family have been identified in the cardiovascular system, although their functional roles are still to be demonstrated. This review provides an up to date summary of what is known about the involvement of members of the K_2P channel family in cells of the heart and arterial circulation. Our knowledge of their roles will improve with the rapidly increasing interest in them and as new selective pharmacological tools emerge. As their physiological roles emerge, the K_2P family of potassium channels may offer promising therapeutic solutions to target cardiovascular diseases. EBSA satellite meeting: ion channels, Leeds, July 2007.     

Computer aided diagnosis of Coronary Artery Disease,Myocardial Infarction and carotid atherosclerosis using ultrasound images: A review

The diagnosis of Coronary Artery Disease (CAD), Myocardial Infarction (MI) and carotid atherosclerosis is of paramount importance, as these cardiovascular diseases may cause medical complications and large number of death. Ultrasound (US) is a widely used imaging modality, as it captures moving images and image features correlate well with results obtained from other imaging methods. Furthermore, US does not use ionizing radiation and it is economical when compared to other imaging modalities. However, reading US images takes time and the relationship between image and tissue composition is complex. Therefore, the diagnostic accuracy depends on both time taken to read the images and experience of the screening practitioner. Computer support tools can reduce the inter-operator variability with lower subject specific expertise, when appropriate processing methods are used. In the current review, we analysed automatic detection methods for the diagnosis of CAD, MI and carotid atherosclerosis based on thoracic and Intravascular Ultrasound (IVUS). We found that IVUS is more often used than thoracic US for CAD. But for MI and carotid atherosclerosis IVUS is still in the experimental stage. Furthermore, thoracic US is more often used than IVUS for computer aided diagnosis systems.     

RANTES gene mRNA expression and its -403 G/A promoter polymorphism in coronary artery disease

Objective

Increased RANTES expression has been described to have a role in atherosclerosis plaque formation. Functional polymorphisms within RANTES promoter region have shown association with increased risk of coronary atherosclerosis (CAD). The aim of this study was to examine the RANTES mRNA expression in patients with CAD compared to patients without CAD and its association with RANTES − 403 G/A polymorphism in an Iranian population.

Methods

The study was performed on 319 patients who underwent coronary artery angiography and patients with > 50% stenosis in vessels considered as case groups (CAD+) N = 191 and normal vessels group as control (CAD−) N = 128. In each group 20 patients were examined for RANTES mRNA expression.RANTES mRNA expression was examined using quantitative real-time PCR. Genotyping of − 403 polymorphism was performed using PCR-RFLP technique.

Results

We found that RANTES mRNA expression was increased to 1.37 fold in CAD patients compared to the controls but the difference was not statistically significant. Also comparing the RANTES mRNA expression in patients with different RANTES − 403 G/A polymorphism showed that in patients carrying AA genotype RANTES mRNA expression was increased to 1.74 fold compared to patients carrying GG genotype and to 1.51 fold compared to patients carrying GA genotype. No significant difference for allele and genotype frequencies of RANTES − 403 polymorphism was found between cases and controls.

Conclusion

More studies on larger number of samples are required to further evaluate role of RANTES in pathogenesis of CAD.     

Effects of mechanical properties and atherosclerotic artery size on biomechanical plaque disruption – Mouse vs. human

Mouse models of atherosclerosis are extensively being used to study the mechanisms of atherosclerotic plaque development and the results are frequently extrapolated to humans. However, major differences have been described between murine and human atherosclerotic lesions and the determination of similarities and differences between these species has been largely addressed recently. This study takes over and extends previous studies performed by our group and related to the biomechanical characterization of both mouse and human atherosclerotic lesions. Its main objective was to determine the distribution and amplitude of mechanical stresses including peak cap stress (PCS) in aortic vessels from atherosclerotic apoE^-/- mice, in order to evaluate whether such biomechanical data would be in accordance with the previously suggested lack of plaque rupture in this model. Successful finite element analysis was performed from the zero-stress configuration of aortic arch sections and mainly indicated (1) the modest role of atherosclerotic lesions in the observed increase in residual parietal stresses in apoE^-/- mouse vessels and (2) the low amplitude of murine PCS as compared to humans. Overall, the results from the present study support the hypothesis that murine biomechanical properties and artery size confer less propensity to rupture for mouse lesions in comparison with those of humans.     

Modelling environmental variation in Young's modulus for Pinus radiata and implications for determination of critical buckling height

• Background and Aims Although density-specific stiffness,E/, (where E is Young's modulus and is wood density) is oftenassumed constant by the elastic similarity model, and in determinationof critical buckling height (H_crit), few studies have testedthis assumption within species. Here this assumption is testedfor Pinus radiata growing across an environmental gradient,and theory is combined with data to develop a model of Young'smodulus. • Methods Analyses use an extensive series of environmentalplots covering the range of climatic and edaphic conditionsover which P. radiata is grown in New Zealand. Reduced majoraxis regression was used to determine scaling exponents betweenlog–log plots of H_crit vs. groundline diameter (D), andE/ vs. D. Path analysis was used to identify significant directand indirect (through stem slenderness) edaphic and climaticinfluences on E. • Key Results Density-specific stiffness exhibited 3-foldvariation. As E/ scaled positively with D, the exponent of 0·95between H_crit and D exceeded the assumed value of 0·67under constant E/. The final path analysis model included meanair temperature in early autumn (T_aut) and slenderness as significant(P < 0·05) positive direct influences on E. Tree leafarea index and T_aut were indirectly associated with E throughtheir significant (P < 0·05) positive direct relationshipwith stem slenderness. Young's modulus was most sensitive toT_aut, followed by stem slenderness then leaf area index, andthe final model explained 76 % of the variance in E. • Conclusions The findings suggest that within speciesE/ variation may influence H_crit and the scaling exponent betweenD and H_crit so important in assumptions regarding allometricrelationships. The model presented may provide a useful meansof determining variation in E, E/ and H_crit across environmentalgradients.