高压力对血管平滑肌细胞的形态、α-肌动蛋白和增殖细胞核抗原表达的影响--一种新的颈总动脉在体受力模型研究

为了研究机械应力在动脉重建中的作用和机制 ,本文建立了以压力改变为启动因素导致动脉重建的大鼠颈总动脉在体受力模型 ,并观察了高压力对血管平滑肌细胞 ( VSMCs)形态、α-肌动蛋白 ( α- actin)和增殖细胞核抗原 ( PCNA)表达的影响。以高压力 ( 160 mm Hg)和正常压力 ( 80 m m Hg)灌流大鼠颈总动脉 6h,组织学和免疫组织化学方法观察 VSMCs的形态、α- actin和 PCNA表达的变化。结果表明 ,大鼠颈总动脉在体受力模型在压力、脉压差和频率方面有较好的可控制性及稳定性 ;高压力使 VSMCs核常染色质增加 ,α- actin染色较正常压力组浅淡 ,表明 α- actin含量减少 ;PCNA表达阳性。大鼠颈总动脉在体受力模型的成功建立 ,为研究机械应力对动脉重建的作用提供了一种新的手段。高压力可诱导 VSMCs向合成型转换 ,细胞趋于增殖     

高压力对血管平滑肌细胞的形态、α—肌动蛋白和增殖细胞核抗原表达的影响——一种新的颈动脉在体受力模型研究

为了研究机械应力在动脉重建中的作用和机制。本文建立了以压力改变为启动因子导致动脉重建的大鼠颈总动脉在体受力模型，并观察了高压力对血管平滑肌细胞（VSMCs）形态、α－肌动蛋白（α-actin）和增殖细胞核抗原（PCNA）表达的影响。以高压力（160mmgHg）和正常压力（80mmHg）灌流大鼠颈总动脉6h、组织学和免疫组织化学方法观察VSMCs的形态、α-actin和PCNA表达的变化。结果表明，大鼠颈总动脉在体受力模型在压力，脉压差和频率方面有较好的可控制性及稳定性；高压力使VSMCs核常染色质增加，α-actin染色较正常压力组浅谈，表明α-actin含量减少；PCNA表达阳性。大鼠颈总动脉在体受力模型的成功建立，为研究机械应力对动脉重建的作用提供了一种新的手段，高压力可诱导VSMCs向合成型转换，细胞趋于增殖。     

高糖诱导人内皮细胞凋亡及其JNK、AKT信号途径的作用机制

目的探讨高糖诱导人脐静脉内皮细胞(humanumbilicalveinendothelialcells,HUVECs)凋亡的JNK及AKT信号途径作用机制。方法HUVECs细胞分别在生理浓度葡萄糖(5mmol/L) (NG)、高葡萄糖(30mmol/L) (HG)、高糖加JNK特异性阻断剂SP6 00 12 5 (10 μmol/L) (HG +I)条件下培养72h。Hoechst332 5 8染色,荧光显微镜观察细胞凋亡的形态学改变;annexinV FITC试剂盒染色,流式细胞仪进行细胞凋亡定量;Westernblot方法测定细胞p JNK、p- c- JUN、p AKT水平。结果高葡萄糖培养72h ,内皮细胞凋亡率为13 .31% ,显著高于对照组5 . 6 9% (P <0 . 0 1)。高糖条件下内皮细胞p JNK、p c JUN水平较对照组显著增加(P <0 . 0 5 ) ,而p AKT显著降低(P <0 . 0 1)。SP6 0 0 12 5应用后,与高糖组比较p JNK无显著变化、p c JUN含量降低(P <0 .0 5 ) ,而p AKT升高(P <0 . 0 1) ,高糖诱导的内皮细胞凋亡被抑制(8. 38% ,P <0 . 0 1)。结论高糖可诱导内皮细胞凋亡,其机制可能是激活JNK及其下游c- JUN ,而抑制AKT的活化,而JNK活化程度对AKT信号通路可能存在调节作用。     

参脉注射液对缺血性大鼠下丘脑损伤的保护作用──c-fos免疫组化研究

缺血性脑损伤是一种常见病、多发病 ,研究其病因、发病机制、诊断和治疗手段具有重要意义 ;c- fos蛋白是 c- fos原癌基因在受刺激时快速、瞬间表达的一种 DNA结合蛋白 ,有研究提示 c- fos蛋白在缺血性脑损伤中具有一定作用。本文采用 c- fos蛋白免疫组织化学方法从分子水平探讨缺血性脑损伤的病理生理改变和参脉注射液的保护作用 ,为临床病理研究提供有关形态学依据。实验采用雄性 Wister大鼠 15只 (体重 2 0 0～ 2 5 0 g) ,随机分为对照组、缺血组和治疗组。缺血组和治疗组大鼠夹闭双侧颈总动脉 2 0分钟后再灌流 1小时 ,建立缺血性脑损伤…     

microRNA-181c-5p抑制Bcl2L11/Bim减轻压力超负荷诱导的小鼠心力衰竭

目的 探讨MicroRNA-181c-5p(miR-181c-5p)对压力超负荷诱导(TAC)的心力衰竭的作用机制.方法 30只雄性C57BL/6小鼠随机分成对照组、TAC组和TAC+miR-181c-5p组.采用主动脉弓缩窄诱导小鼠心力衰竭动物模型,造模过程中,对模型组小鼠心肌多点注射给予5× 106U/10μL过表...     

体外反搏对犬血流脉动性和血管阻力的影响

为了评价体外反搏是否具有扩张血管和增加血流脉动性的作用 ,制造了犬急性心肌梗塞模型 ,并使犬存活 6周。麻醉后 ,测定左侧颈总动脉血流量和右侧颈总动脉血压。计算反搏前和反搏中脉压差、血压脉动指数、血压的标准差、流量差、流量脉动指数、流量标准差和平均血管阻力。结果显示脉压差、血压脉动指数和血压标准差三个血压脉动性指标分别由反搏前的 30± 9mm Hg、1.2 6± 0 .0 5、8.7± 2 .5 mm Hg升高到反搏中的 4 3± 8mm Hg(P<0 .0 5 )、1.5 4± 0 .13、12 .4± 2 .0 mm Hg (P<0 .0 5 )。流量差、流量脉动指数和流量标准差三个血流脉动性指标分别由反搏前的 317± 4 8ml/ min、2 .85± 0 .2 1、96± 2 1ml/ min升高到反搏中的 4 4 7± 88m l/ min、4 .5 6± 0 .90、131±39m l/ m in,P值均于小 0 .0 5。平均血管阻力由反搏前的 5 78± 72 Wood单位降低到反搏中的 4 76± 85 Wood单位(P<0 .0 5 )。这表明体外反搏可使血管阻力下降 ,血压和血流脉动性增强。     

L-NAME诱导妊娠高血压大鼠动脉重建的特征

目的探讨妊娠高血压大鼠动脉重建的特征。方法采用亚硝基左旋精氨酸甲酯(L-nitro-arginine methylester,L-NAME)诱导,构建妊娠高血压大鼠模型,以正常孕鼠为对照,用无创鼠尾血压测量仪测量血压以确认模型构建成功。测量血液黏度、左侧颈总动脉平均血流量,检测胸主动脉和颈总动脉的管壁厚度、管腔内径、张开角,计算并比较颈总动脉平均切应力的变化。Western blotting检测胸主动脉血管成分胶原蛋白Ⅰ(collagenⅠ,ColⅠ)、胶原蛋白Ⅲ(collagenⅢ,ColⅢ)表达,分析动脉血管重建程度。结果妊娠高血压模型大鼠血黏度增加,平均血流量降低;颈总动脉和胸主动脉壁厚内径比明显增大;颈总动脉张开角减小,胸主动脉张开角增大;颈总动脉平均切应力降低(28.52±3.08)%;ColⅠ表达下降,ColⅢ表达增加,ColⅠ、Ⅲ比例显著减小。结论妊娠高血压大鼠平均切应力下降,胸主动脉和颈总动脉发生血管重建。研究结果可以为妊娠高血压发病机制的深入研究提供基础实验数据支撑。     

自发性高血压大鼠颈总动脉的平均壁面切应力和周向应力

目的确定自发性高血压大鼠(SHR)颈总动脉的平均壁面切应力(WSS)和周向应力(CS),并与同龄正常血压大鼠(WKY)相对比,观察SHR和WKY大鼠颈总动脉平均WSS和CS的特征。方法选取12周龄SHR作为动物模型,同龄WKY为对照组;通过在体测定颈总动脉的平均血流量与平均血压,离体测量颈总动脉的无载荷状态形态学数据,以及在体轴向伸长比条件下颈总动脉段的压力(p)-容积(V)关系,确定颈总动脉平均WSS和CS;同时比较SHR和WKY颈总动脉的平均血压和血流量、无载荷和载荷状态几何尺寸以及平均WSS和CS的特征。结果与正常血压的WKY组相比,SHR组颈总动脉血压明显增高、流量明显降低;无载荷和载荷状态下SHR组动脉的内外半径均增大,载荷状态下SHR组动脉壁厚减小;SHR颈总动脉平均WSS明显降低,而CS明显增高。结论高血压和低流量引起了SHR颈总动脉重建;低WSS和高CS是SHR颈总动脉血液动力学参数的重要特征;WSS和CS的协同作用可能是反映动脉重建的敏感指标之一。     

脉压在老年高血压患者中的作用

目的　探讨老年高血压患者脉压 (PP)与左心室重量指数 (L VMI)的关系。方法　用血压计、超声心动图检测 78例老年高血压患者和 3 0例血压正常 PP<60 mm Hg者的 PP和 L VMI。结果　高血压 PP≥ 60 mm Hg组年龄比 PP<60 mm Hg组高 (P<0 .0 5)。高血压 PP≥ 60 mm Hg与高血压 PP<60 m m Hg组和血压正常组比 L VMI最高 (P<0 .0 5)。结论　脉压增大促进老年高血压左心室肥厚     

高血压与低切应力对大鼠颈总动脉血管重建的影响

目的研究高血压与低切应力对血管重建的影响及其机制,这对于阐明血管疾病的发病机理以及提供诊断、治疗的一些基本原理都将有重要的理论和实际意义。方法通过腹主动脉缩窄,结扎左颈总动脉的部分分支建立高血压、左颈总动脉低切应力以及高血压伴有低切应力大鼠动物模型。几何形态学方法观测左颈总动脉的壁厚及壁厚/内径比的变化;金属蛋白酶谱法分析MMP-2活性;免疫印迹法检测信号通路分子p-Akt分子以及Rho GDIα的表达变化。结果高血压和低切应力均可诱导颈总动脉MMP-2活性和壁厚及壁厚/内径比显著增加;当高血压伴有低切应力时,两者的协同作用诱导颈总动脉MMP-2活性和壁厚及壁厚/内径比进一步增加,从而促进血管重建。低切应力可诱导颈总动脉p-Akt的表达水平,且与低切应力大小相关,切应力低,p-Akt的表达水平高。当高血压伴有低切应力时,两者的协同作用诱导p-Akt的表达水平进一步增加。高血压和低切应力可诱导颈总动脉RhoGDIα表达增加;当高血压伴有低切应力时,两者的协同作用诱导颈总动脉Rho GDIα表达进一步增加。结论高血压与切应力协同作用对血管重建的影响最为显著,Akt和Rho GDIα信号通路参与了高血压与低切应力诱导的血管重建过程。     

Mechanical and dimensional adaptation of rabbit carotid artery culturedin vitro

The effects of the mechanical environment on arterial walls were investigated in rabbit common carotid arteries, cultured for six days under three different intraluminal pressures (0, 80 and 160 mmHg) in a perfusion culture system. The mechanical responses following the culture were examined using a quasi-static pressure-diameter test. Specimen viability was determined by smooth muscle contraction induced with KCl. Eighteen out of 21 cultured segments showed a peak reduction in diameter of more than 10% and were used for the analysis. The arterial segments cultured at 0 mmHg had a significantly smaller diameter than those cultured at other pressures. The segments cultured at higher pressure had lower incremental elastic moduli at 20 and 80 mmHg and higher moduli at 160 mmHg. The walls of the cultured segments were thicker in groups with higher pressure. These results indicate that, even in culture, the mechanical environment is a major determinant for the mechanical property and dimensions of the arterial wall. Arterial walls may respond to their mechanical environment even if other factors, such as hormonal environment and nervous stimuli, are kept unchanged.     

Mechanical and dimensional adaptation of rabbit carotid artery culturedin vitro

The effects of the mechanical environment on arterial walls were investigated in rabbit common carotid arteries, cultured for six days under three different intraluminal pressures (0, 80 and 160 mmHg) in a perfusion culture system. The mechanical responses following the culture were examined using a quasi-static pressure-diameter test. Specimen viability was determined by smooth muscle contraction induced with KCl. Eighteen out of 21 cultured segments showed a peak reduction in diameter of more than 10% and were used for the analysis. The arterial segments cultured at 0 mmHg had a significantly smaller diameter than those cultured at other pressures. The segments cultured at higher pressure had lower incremental elastic moduli at 20 and 80 mmHg and higher moduli at 160 mmHg. The walls of the cultured segments were thicker in groups with higher pressure. These results indicate that, even in culture, the mechanical environment is a major determinant for the mechanical property and dimensions of the arterial wall. Arterial walls may respond to their mechanical environment even if other factors, such as hormonal environment and nervous stimuli, are kept unchanged.     

Angiographic evaluation of the rat carotid balloon injury model

Rationale

The rat carotid balloon-injury (BI) model is a widely used model of intimal hyperplasia (IH) and vascular remodeling. A variable degree of IH after BI has been previously reported, and we have encountered technical challenges and suboptimal results with the original method.

Objective

To evaluate the original rat carotid artery BI method with the use of micro-angiography. We tested the hypothesis that in order to obtain an optimal arterial response, BI should be limited to the common carotid artery with preservation of blood flow.

Methods and results

The left common carotid artery (CCA) was injured by one of three different methods. Carotid angiograms and pathology were examined 14 days after BI.A 2 F Fogarty balloon catheter inflated to 2 atm inside the aortic arch would not slide back into the common carotid artery until deflation to 0.5 to 0.7 atm. Four out of five (80%) vessels injured with this method developed excessive inflammation without discernible IH. Six out of nine (66%) arteries that underwent BI limited to the CCA at 2 atm developed the largest angiographic stenosis (p = 0.003) and IH (0.20 ± 0.03 mm², p = 0.028). Ten out of eleven (91%) arteries injured with a variable pressure of 1.5 to 2.2 atm, based on the operator's feedback, developed considerable IH (0.12 ± 0.02 mm²). All injured carotid arteries with preserved blood flow on angiography developed IH with intact histological boundaries.

Conclusions

Optimal IH with preservation of histological boundaries is achieved by graded BI limited to the CCA that preserves carotid blood flow.     

The influence of heart rate on baroreceptor fibre activity in the carotid sinus and aortic depressor nerves of the rabbit

The arterial baroreceptors and their afferent fibres provide the sensory arm of the reflex that regulates systemic arterial pressure. We have examined whether the relationship between mean baroreceptor discharge and mean arterial pressure is altered when heart rate changes. Experiments were performed on pentobarbitone-anaesthetized rabbits. We recorded the activity of single and multifibre preparations of the carotid sinus (CSN) and aortic depressor nerves (ADN). Data were collected under control conditions and while heart rate was increased by approximately 30-35% by right atrial pacing. Baroreceptor regions were exposed to ramps of pressure (from approximately 25 to 140 mmHg, at approximately 0.5-1 mmHg s(-1)), generated by inflation and deflation of cuffs placed around the inferior vena cava and descending thoracic aorta. Response curves relating baroreceptor discharge to mean pressure were constructed and fitted with third-order polynomial expressions. To provide a measure of an effect of an increase in heart rate on the response curve in the region of the normal operating pressure, we calculated the position of the test response curve relative to the position of the control curve at 90 mmHg (deltaBP(90)). For the ADN, the activity of single fibres (presumptive myelinated fibres) was unaffected by increasing heart rate (deltaBP(90) = +0.1 +/- 1.0 mmHg), while single fibres in the CSN showed a small increase in activity (deltaBP(90) = -1.5 +/- 0.3 mmHg). In multifibre preparations there was a small increase in activity that may be attributable to additional activity in unmyelinated fibres (ADN, deltaBP(90) = -3.4 +/- 1.2 mmHg; CSN, deltaBP(90) = -5.2 +/- 0.9 mmHg). We conclude that the mean discharge of arterial baroreceptors remains a reliable index of mean arterial pressure in the presence of substantial changes in heart rate.     

An In Vivo Rat Model of Artery Buckling for Studying Wall Remodeling

Theoretical modeling and in vitro experiments have demonstrated that arterial buckling is a possible mechanism for the development of artery tortuosity. However, there has been no report of whether artery buckling develops into tortuosity, partially due to the lack of in vivo models for long-term studies. The objective of this study was to establish an in vivo buckling model in rat carotid arteries for studying arterial wall remodeling after buckling. Rat left carotid arteries were transplanted to the right carotid arteries to generate buckling under in vivo pressure and were maintained for 1 week to examine wall remodeling and adaptation. Our results showed that a significant buckling was achieved in the carotid arterial grafts with altered wall stress. Cell proliferation and matrix metalloprotinease-2 (MMP-2) expression in the buckled arteries increased significantly compared with the controls. The tortuosity level of the grafts also slightly increased 1 week post-surgery, while there was no change in vessel dimensions, blood pressure, and blood flow velocity. The artery buckling model provides a useful tool for further study of the adaptation of arteries into tortuous shapes.     

Vascular resistance of intestine, muscle and skin during blood pressure oscillation.

After the blood supply to the head was surgically limited to one common carotid artery in rabbits, the artery was compressed by exertion of stepwise elevated side pressure on a segment of the artery. Systemic arterial pressure rose and began to oscillate when the side pressure was increased to 50 to 60 mmHg. The oscillations were regular and occurred at a rate of 3 to 4 per minute with a wave height of 15 to 45 mmHg. Concomitant with systemic pressure oscillations, and in near synchrony were undulations in the perfusion pressures recorded during constant flow from the vascularly isolated abdominal skin, skeletal muscle and small intestine. With the graded elevation of side pressure on the common carotid artery, mean systemic pressure and perfusion pressure showed a nearly exponential relation. The ratio between the two variables was slightly less than one below the systemic pressure of 120 mmHg and rapidly increased above this level. At ratios greater than one, the peripheral resistance undulations in the isolated areas gave a larger minimum and maximum, a sharper contour and, particularly in the skin, a phase lag in the period of the wave form when compared to the systemic pressure oscillations. These observations highlight the differences in response characteristics of peripheral resistance vessels and those of cardiac output and different consecutive parts of the systemic arteries during periods of intense sympathetic activation.     

Intermittent short-duration exposure to low wall shear stress induces intimal thickening in arteries exposed to chronic high shear stress

We sought to determine whether intermittent short-duration exposure to low wall shear stress could induce intimal thickening in arteries chronically exposed to high shear stress. An arteriovenous fistula (AVF) was created between the left common carotid artery and the corresponding external jugular vein in 20 Japanese white male rabbits. After 4 weeks, blood flow was increased 10-fold to 182 +/- 39 ml/min and shear stress was increased to 33.4 +/- 13 dyn/cm(2). The AVF was then occluded for 1 h by finger compression with an 85% reduction in carotid artery blood flow (27 +/- 7 ml/min) and a reduction in wall shear stress to 4.9 +/- 1.7 dyn/cm(2) (P < 0.0001). Release of finger compression restored flow to the AVF and high shear stress to the carotid artery. This procedure was repeated at weekly intervals with a cumulative total of 4 h of low shear stress exposure. Arteries exposed to intermittent low shear stress developed a layer of intimal thickening which consisted of 3-4 layers of smooth muscle cells lined with thin elastic fibers and medial hyperplasia. Control arteries exposed to 8 weeks of continuous high shear had no intimal thickening. Transient exposure to low shear stress upregulated TGF-beta1, MMP-2, -14, and TIMP-2 gene expression while MMP-9 expression was downregulated. We conclude that repeated, intermittent short-duration exposure to low shear stress in the setting of high flow and high shear stress can induce arterial intimal thickening. Short-duration alterations in hemodynamic forces can induce rapid vascular cell message expression, which may effect arterial remodeling. This experiment suggests that a threshold value of 5 dyn/cm(2) may be needed in order to initiate and sustain the intimal thickening response.     

Sustained vessel dilation induced by increased pulsatile perfusion of porcine carotid arteries in vitro.

Arterial pulse pressure (PP) increases with exertional stress and ageing, and can modify vessel diameter in smaller vessels. To test if PP must exceed a certain range to influence vessel diameter, and determine if such effects are endothelium-dependent or intrinsic to vascular viscoelasticity, eight fresh excised porcine carotid artery segments were perfused with modified Krebs-Henseleit by a servo-controlled system generating physiological arterial pressure waveforms. In a separate group of vessels (n = 10), the endothelium was mechanically removed. Vessel external diameter was measured by video edge-detection. Vessels partially preconstricted with noradrenaline were perfused at 9 mL min(-1) mean flow, at mean pressure of 90 or 120 mmHg, and zero PP. PP alone was then increased to 40, 70, or 120 mmHg at 1 Hz cycling rate for 5 min, then returned to zero and vessel diameter measured immediately thereafter. The protocol was repeated after 10-20 min stabilization. Mean vessel diameter rose proportionally with PP only once PP exceeded 40 mmHg, with maximal increases of 6-9% at a PP of 120 mmHg. Similar responses were obtained in vessels with and without a functional endothelium, at both mean pressures. Thus, when exposed to higher than normal resting PP, conduit arteries dilate owing to the stress-relaxation response of their viscoelastic wall. This mechanism of PP-mediated vascular dilatation may contribute to enhanced organ perfusion when small resistance arteries are already dilated.     

Effect of cervical sympathetic nerve stimulation on canine carotid sinus reflex.

In the chloralose-anesthetized dog the carotid sinus on one side of the neck was isolated vascularly. Pressure in the isolated sinus [carotid sinus pressure (CSP)], electrocardiogram, and systemic arterial pressure were recorded. Both vagosympathetic trunks were cut and the contralateral common carotid artery was occluded or the contralateral sinus nerve was cut to reduce reflex buffering of arterial pressure changes. By varying CSP from 50 to 250 mmHg the full range of the reflex response was examined. Electrical stimulation of the peripheral end of the cut ipsilateral cervical sympathetic nerve brought about a rapid decrease in mean arterial pressure (MAP) and heart rate (HR) at lower CSPs, no change in these variables at midrange CSPs, and a gradual increase at higher CSPs, such that the gain of the reflex was reduced (1.89 +/- 0.19 to 1.33 +/- 0.15 mmHg/mmHg). The decrease in MAP and HR at lower CSPs implies an increase in baroreceptor activity whereas the converse would appear to occur at higher CSPs. These responses attained a maximum value at low stimulus frequencies (less than 10 Hz).     

Sustained vessel dilation induced by increased pulsatile perfusion of porcine carotid arteries in vitro

Arterial pulse pressure (PP) increases with exertional stress and ageing, and can modify vessel diameter in smaller vessels. To test if PP must exceed a certain range to influence vessel diameter, and determine if such effects are endothelium-dependent or intrinsic to vascular viscoelasticity, eight fresh excised porcine carotid artery segments were perfused with modified Krebs–Henseleit by a servo-controlled system generating physiological arterial pressure waveforms. In a separate group of vessels (n = 10), the endothelium was mechanically removed. Vessel external diameter was measured by video edge-detection. Vessels partially preconstricted with noradrenaline were perfused at 9 mL min^–1 mean flow, at mean pressure of 90 or 120 mmHg, and zero PP. PP alone was then increased to 40, 70, or 120 mmHg at 1 Hz cycling rate for 5 min, then returned to zero and vessel diameter measured immediately thereafter. The protocol was repeated after 10–20 min stabilization. Mean vessel diameter rose proportionally with PP only once PP exceeded 40 mmHg, with maximal increases of 6–9% at a PP of 120 mmHg. Similar responses were obtained in vessels with and without a functional endothelium, at both mean pressures. Thus, when exposed to higher than normal resting PP, conduit arteries dilate owing to the stress-relaxation response of their viscoelastic wall. This mechanism of PP-mediated vascular dilatation may contribute to enhanced organ perfusion when small resistance arteries are already dilated.