Pulmonary artery remodeling and pulmonary hypertension after exposure to hyperoxia for 7 days. A morphometric and hemodynamic study.

This study shows by morphometric and hemodynamic techniques that exposure to hyperoxia at normobaric pressure causes rapid structural remodeling of rat pulmonary arteries and pulmonary hypertension. After 7 days of 90% O2, pulmonary artery cross-sectional area is reduced by a striking loss of intraacinar arteries (control, 13 +/- 1 sq mm; exposed, 8 +/- 1 sq mm; P less than 0.001), the ratio of arteries to alveoli being 4:100 in control rats and 2.5:100 after hyperoxia. The lumen of preacinar and intraacinar arteries is narrowed by a reduction of vessel external diameter (ED) and an increased medial wall thickness (MT). There is a significant reduction in the percent medial thickness [( 2 X 100 X MT]/ED) in both regions. The proportion of muscular and partially muscular intraacinar arteries increases at the expense of nonmuscular ones (P [chi 2] less than 0.01), and fully muscular arteries appear in the alveolar wall where they are not normally found. Intimal thickening occurs in 19% of alveolar duct and 34% of alveolar wall nonmuscular arteries. Right ventricular hypertrophy occurs, the ratio of the left ventricle plus the septum to the right ventricle being significantly reduced (control, 4.07 +/- 0.26; exposed, 3.23 +/- 0.10; P less than 0.02). After 3 days of 87% O2, pulmonary artery pressure is still normal (17.0 +/- 0.9 mmHg) but after 7 days it is significantly increased (26.2 +/- 0.9 mmHg; P less than 0.01), as is pulmonary vascular resistance (control, 0.033 +/- 0.003; exposed, 0.065 +/- 0.015 U/kg; P less than 0.05). Return to air breathing (after 7 days at 87% O2) causes pulmonary vasoconstriction and a further rise of the pulmonary artery pressure (to 38.3 +/- 3.3 mmHg after 60 minutes).     

Flow dependence and time constant of the change in nitric oxide concentration measured in the vascular media

It has been considered that the concentration of endothelium-derived nitric oxide (NO) in the arterial vascular wall changes in response to flow-induced shear stress. In the present study, using an NO-sensitive electrode, the aim was to directly evaluate the relationship between perfusion rate and NO concentration in the arterial vascular wall. The NO microelectrode (diameter: 100 microns) was inserted into the vascular media of isolated canine femoral arteries, and the vessel was perfused with a Krebs-Henseleit buffer solution. A flow-related change in NO concentration in the vascular media was then evaluated by changing perfusion rate. NO concentration attained a peak value with a first-order time delay by a stepwise increase in perfusion rate, and the peak-level NO concentration was linearly correlated with perfusion rate in each vessel (10-154 pA at 2.1-72.3 ml min-1; n = 7, r2 = 0.89-0.99, p < 0.03). The average time constant for an increase in NO current with a stepwise increase in perfusion rate was 24 +/- 3 s (n = 5). NO production was increased by perfusing a solution containing 1 mmol l-1 L-arginine and was attenuated by 100 mumol l-1 NG-nitro-L-arginine, indicating the intactness of the endothelium, proper insertion of the NO electrode and selective detection of NO by the electrode. It is concluded that the NO microelectrode is applicable to NO measurement in the vascular media where NO controls vascular tone and that the concentration of NO in the arterial vascular media changes with perfusion rate in a rate-dependent manner as well as with a time constant of about 24 s for a stepwise increase in flow.     

Protective effect of hydrogen sulfide on balloon injury-induced neointima hyperplasia in rat carotid arteries

Endogenous hydrogen sulfide (H(2)S), generated from homocysteine metabolism mainly catalyzed by cystathionine gamma-lyase (CSE), possesses important functions in the cardiovascular system. In this study, we investigated the role of H(2)S during the pathogenesis of neointimal formation induced by balloon injury in rats. CSE mRNA levels were reduced by 86.5% at 1 week and 64.0% at 4 weeks after balloon injury compared with the uninjured controls. CSE activity was also correspondingly reduced. Endogenous production of H(2)S in the injured carotid artery was significantly inhibited at 1 week and 4 weeks after balloon injury. Treatment with NaHS (a donor of H(2)S) enhanced methacholine-induced vasorelaxation of balloon-injured artery. More importantly, treatment with NaHS significantly inhibited neointima formation (0.15 +/- 0.01 mm(2) versus 0.21 +/- 0.01 mm(2), P < 0.001) of the balloon-injured carotid arteries and reduced the intima/media ratio (1.05 +/- 0.07 versus 1.43 +/- 0.06, P < 0.001). A significant decrease in vascular smooth muscle cell proliferation was demonstrated by bromodeoxyuridine incorporation at day 7 after injury. In conclusion, CSE expression and H(2)S production are reduced during the development of balloon injury-induced neointimal hyperplasia, and treatment with NaHS significantly reduces neointimal lesion formation.     

瑞舒伐他汀对大鼠颈动脉球囊损伤后细胞凋亡的影响

目的观察瑞舒伐他汀对大鼠颈动脉球囊损伤后细胞凋亡的影响。方法36只雄性SD大鼠随机分为对照组、损伤组和治疗组,每组12只。损伤组和治疗组分别建立大鼠左侧颈动脉球囊损伤模型,右侧颈动脉未予球囊损伤。治疗组于损伤前3d始连续每天给予瑞舒伐他汀5mg／（kg·d）灌胃,对照组和损伤组予9g／L氯化钠溶液灌胃。术后14d取左侧颈总动脉,进行HE染色和末端脱氧核苷酸转移酶介导的生物素-dUTP缺口标记技术（Terminal deoxynucleotidyl transferase biotin—dUTP nick end labeling,TUNEL）的凋亡检测。结果共30只大鼠成功完成本次实验。①血管损伤14d,可见明显的新生内膜;损伤组和治疗组的内膜面积、内膜／中膜面积的比值较对照组增大（P〈0．05）;与损伤组比较,治疗组内膜／中膜面积的比值减少,管腔面积增加26％（P〈0．05）。②对照组血管偶可见单个散在的凋亡细胞;损伤组凋亡细胞阳性率为（12．3±1．8）％,与对照组比较,差异有统计学意义（P〈0．05）;治疗组凋亡细胞数目增多,凋亡细胞阳性率达（26．8±3．2）％,与损伤组比较,差异有统计学意义（P〈0．05）。凋亡细胞主要位于新生内膜。结论瑞舒伐他汀可抑制大鼠颈动脉球囊损伤后的内膜增生,可促进大鼠颈动脉球囊损伤后的细胞凋亡。瑞舒伐他汀促进细胞凋亡的作用可能与其抑制内膜增生有关。     

罗格列酮抑制大鼠颈动脉球囊损伤后新生内膜增生和基质金属蛋白酶-2的表达

目的探讨PPARγ配体罗格列酮对大鼠颈动脉球囊损伤后新生内膜增生及MMP-2和TIMP-2表达的影响。方法实验分为给药组(罗格列酮3 mg/kg.d)和对照组(0.9%氯化钠注射液),每组n=5。用球囊血管内膜剥脱法建立大鼠颈动脉再狭窄模型。HE染色检测血管内膜与中膜的厚度比和面积比。RT-PCR和Western blot法检测血管组织中MMP-2和TIMP-2的mRNA和蛋白质的表达。结果罗格列酮明显抑制球囊损伤后血管新生内膜增生,与对照组相比,术后所有时间点上内膜与中膜的厚度比及面积比均显著减少(P<0.001)。罗格列酮组与对照组比较显著抑制球囊损伤后各时间点血管中基质金属蛋白酶-2(MMP-2)的mRNA和蛋白的表达,术后1、7、14、28 d蛋白表达由对照组的0.605±0.007、1.000±0.002、0.890±0.014和0.290±0.028降至0.310±0.014、0.525±0.021、0.405±0.007和0.081±0.004(P<0.001)。但罗格列酮对MMP-2抑制剂TIMP-2的mRNA和蛋白表达无影响。结论罗格列酮抑制大鼠颈动脉球囊损伤后新生内膜增生,其机制可能与MMP-2的表达下调及MMP-2/TIMP-2表达失衡有关。     

Percutaneous catheter commissurotomy in rheumatic mitral stenosis

We attempted percutaneous transcatheter-balloon mitral commissurotomy in eight children and young adults (9 to 23 years of age) with rheumatic mitral stenosis. The atrial septum was traversed by needle puncture, and an 8-mm angioplasty balloon was advanced over a guide wire. The atrial septal perforation was then dilated to allow passage of the valvuloplasty balloon catheter (18 to 25 mm) across the mitral annulus. Inflation of the transmitral balloon decreased the end-diastolic transmitral gradient temporarily in all patients (from 21.2 +/- 4.0 mm Hg [mean +/- S.D.] to 10.1 +/- 5.5 mm Hg; P less than 0.001). The immediate decrease in the gradient was associated with increases in cardiac output (from 3.8 +/- 1.0 to 4.9 +/- 1.3 liters per minute per square meter of body-surface area; P less than 0.01) and in the calculated mitral-valve-area index (from 0.73 +/- 0.29 to 1.34 +/- 0.32 cm2 per square meter; P less than 0.001). Murmur intensity diminished immediately after commissurotomy in all patients. The greatest reduction in pressure gradient (76 to 95 per cent) occurred when the largest balloon (inflated diameter, 25 mm) was used in the smallest patients (0.9 to 1.2 m2). The balloon commissurotomy produced minimal mitral regurgitation in only one child. Follow-up catheterization (at two to eight weeks) demonstrated persistence of hemodynamic improvement with evidence of partial restenosis in one patient. These early results indicate that balloon mitral commissurotomy can be a safe and effective treatment for children and young adults with rheumatic mitral stenosis.     

Impairment of endothelium-dependent pulmonary-artery relaxation in chronic obstructive lung disease

BACKGROUND. Endothelial cells release endothelium-derived relaxing factor (EDRF) in a variety of vascular beds, including the pulmonary circulation. However, the role of EDRF-mediated pulmonary-artery relaxation in chronic hypoxic lung disease is unknown. METHODS. We studied endothelium-dependent relaxation mediated by EDRF in vitro in pulmonary arteries that had been obtained from 22 patients undergoing heart-lung transplantation for end-stage chronic obstructive lung disease. Control pulmonary arteries were obtained from 15 patients undergoing lobectomy for lung carcinoma who did not have evidence of other chronic lung disease. The responses of all vascular rings (external diameter, 1.2 to 3.4 mm) to the endothelium-dependent vasodilators acetylcholine and adenosine diphosphate were studied immediately after lung excision. RESULTS. Pulmonary arterial rings from the patients with chronic lung disease developed a greater tension (2.19 +/- 0.16 g) in response to phenylephrine (10(-6) M) than the rings from control patients (1.28 +/- 0.18 g, P less than 0.05). Inhibition of EDRF synthesis by treatment with NG-monomethyl-L-arginine (10(-4) M) eliminated this difference, increasing the tension in the rings from the controls (P less than 0.01) but not in those from the patients with chronic lung disease. Rings from control patients relaxed in response to cumulative doses (10(-10) to 10(-5) M) of acetylcholine (maximal relaxation, 81.3 +/- 3.9 percent) and adenosine diphosphate (maximal relaxation, 85.3 +/- 2.6 percent). By contrast, rings from patients with chronic obstructive lung disease achieved only 41.3 +/- 4.8 percent of maximal relaxation in response to acetylcholine (n = 32) and 49.4 +/- 5.5 percent in response to adenosine diphosphate (n = 24) (P less than 0.001, as compared with control rings). Rings from both the controls and the patients with chronic lung disease relaxed similarly in response to the endothelium-independent vasodilator sodium nitroprusside (10(-4) M). There was an inverse correlation between the degree of intimal thickening and the level of maximal relaxation of the rings from the patients with chronic lung disease (r = -0.60, P less than 0.001). Maximal relaxation was also related directly to the partial pressure of arterial oxygen before transplantation (r = 0.68, P less than 0.01) and inversely to the partial pressure of arterial carbon dioxide before transplantation (r = -0.55, P less than 0.01), but not to the forced expiratory volume in one second (r = 0.19, P not significant). CONCLUSIONS. Endothelium-dependent pulmonary-artery relaxation in vitro is impaired in arteries from patients with end-stage chronic obstructive lung disease. Such impairment may contribute to the development of pulmonary hypertension in chronic hypoxic lung disease.     

Non-invasive evaluation of the conduit function and the buffering function of large arteries in man.

The purpose of this study was to validate a two-dimensional (2D) echography coupled range-gated Doppler system for the non-invasive measurement of internal diameter, blood flow velocity, and pulse wave velocity of peripheral arteries, such as the common carotid artery (CCA), femoral artery (FA), and brachial artery (BA) in man. The array of the ultrasonic system and the Doppler probe were attached and formed a fixed angle (38 degrees 30'). The artery was firstly visualized using the echo-graphic array probe in order to position the Doppler beam. Then, the range-gated Doppler system was used to measure both internal diameter and blood flow velocity with the sample volume position covering the internal diameter. Using a hydraulic device, there was an obvious correlation between the calculated and the measured velocities (r = 0.98). Normal values of diameter, blood flow velocity and blood flow were measured in 18 healthy volunteers. The means (+/- 1 standard deviation) was as follows: diameter, CCA = 0.636 +/- 0.027 cm, FA = 0.843 +/- 0.074 cm, BA = 0.302 +/- 0.052 cm; flow velocity, CCA = 19.5 +/- 2.1 cm s-1, FA = 11.4 +/- 1.2 cm s-1, BA = 6.7 +/- 1.0 cm s-1. Blood flows were as follows: CCA, 370.6 +/- 42.5 ml mn-1, FA 387.0 +/- 75.0 ml mn-1 and BA (wrist occlusion) 29.8 +/- 12.5 ml mn-1. The intra-observer reproducibilities for CCA, FA and BA were respectively: for diameter, 4.9%, 4.12% and 14.8%; for velocity, 8.9%, 10.6% and 10.2%. The inter-observer reproducibilities were respectively: for diameter, 5.6%, 5.4% and 11.3% for velocity, 6.5%, 5.7% and 6.3%. Simultaneous determinations of pulse wave velocity from blood flow velocity recording allowed estimations of the distensibility of these arteries. Finally, the coupled echo and range-gated Doppler system permitted non-invasive evaluation of blood flow calculated as the product of the vessel cross-sectional area and measured blood velocity and also of arterial compliance as the ratio of the cross-sectional area and the square of pulse wave velocity. Such estimations of the conduit and buffering functions of peripheral large arteries in man were shown to be more accurate for the common carotid and the femoral arteries than for the brachial artery.     

Uterine artery function in pregnant rats fed a diet supplemented with animal lard

We hypothesised that maternal uterine artery vascular dysfunction could contribute to cardiovascular dysfunction in offspring of rats fed a diet rich in fat. Sprague-Dawley rats were fed for 10 days prior to pregnancy and throughout gestation either: (a) a control breeding diet, or (b) the same diet supplemented with 20 % w/w lard, vitamins, essential micronutrients and protein to control values. At 20 days gestation vascular function was assessed in uterine arteries and third-order mesenteric arteries. Vascular reactivity in response to application of potassium, noradrenaline, the thromboxane analogue U46619, acetylcholine and nitric oxide was assessed. Maternal plasma concentrations of factors likely to contribute to endothelial dysfunction were measured. Maximum acetylcholine-induced relaxation was impaired in the mesenteric arteries of the lard-fed dams (max % relaxation: lard-fed, 69.7 +/- 6.48; control, 85.37 +/- 2.69, P = 0.03). Uterine artery vascular function was similar in the two groups (max % acetylcholine-induced relaxation: lard-fed, 73.7 +/- 4.01; control, 77.5 +/- 4.72, P = 0.98). Concentrations of plasma lipids, 8-epi-PGF(2alpha) and leptin were normal, whereas insulin and corticosterone concentrations were raised in the lard-fed group (insulin (ng ml(-1)): lard-fed, 8.04 +/- 0.47; control, 1.35 +/- 0.37, P < 0.0001; corticosterone (ng ml(-1)): lard-fed, 1164.0 +/- 170.9; control, 541.9 +/- 96.3, P = 0.005). Fetal and placental weights were reduced in lard-fed dams (fetus (g): lard-fed, 4.27 +/- 0.38; control, 2.96 +/- 0.40, P = 0.025; placenta (g): lard-fed, 0.72 +/- 0.06; control, 0.57 +/- 0.04, P = 0.05). Cardiovascular dysfunction in offspring is not associated with reduced uterine artery endothelial function but is associated with activation of the hypothalamic-pituitary-adrenal axis, hyperinsulinaemia and fetoplacental growth retardation.     

Abnormal endothelium-dependent vascular relaxation in patients with essential hypertension

BACKGROUND. Endothelium regulates vascular tone by influencing the contractile activity of vascular smooth muscle. This regulatory effect of the endothelium on blood vessels has been shown to be impaired in atherosclerotic arteries in humans and animals and in animal models of hypertension. METHODS. To determine whether patients with essential hypertension have an endothelium-dependent abnormality in vascular relaxation, we studied the response of the forearm vasculature to acetylcholine (an endothelium-dependent vasodilator) and sodium nitroprusside (a direct dilator of smooth muscle) in 18 hypertensive patients (mean age [+/- SD], 50.7 +/- 10 years; 10 men and 8 women) two weeks after the withdrawal of antihypertensive medications and in 18 normal controls (mean age, 49.9 +/- 9; 9 men and 9 women). The drugs were infused at increasing concentrations into the brachial artery, and the response in forearm blood flow was measured by strain-gauge plethysmography. RESULTS. The basal forearm blood flow was similar in the patients and controls (mean +/- SD, 3.4 +/- 1.3 and 3.7 +/- 0.8 ml per minute per 100 ml of forearm tissue, respectively; P not significant). The responses of blood flow and vascular resistance to acetylcholine were significantly reduced in the hypertensive patients (P less than 0.0001); maximal forearm flow was 9.1 +/- 5 ml per minute per 100 ml in the patients and 20.0 +/- 8 ml per minute per 100 ml in the controls (P less than 0.0002). However, there were no significant differences between groups in the responses of blood flow and vascular resistance to sodium nitroprusside. Because the vasodilator effect of acetylcholine might also be due to presynaptic inhibition of the release of norepinephrine by adrenergic nerve terminals, the effect of acetylcholine was assessed during phentolamine-induced alpha-adrenergic blockade. Under these conditions, it was also evident that the responses to acetylcholine were significantly blunted in the hypertensive patients (P less than 0.03). CONCLUSIONS. Endothelium-mediated vasodilation is impaired in patients with essential hypertension. This defect may play an important part in the functional abnormalities of resistance vessels that are observed in hypertensive patients.     

Contribution of Na+/Ca2+ exchanger to the regulation of myogenic tone in isolated rat small arteries.

The contribution of the Na+/Ca2+ exchanger to the myogenic vascular tone was examined in rat isolated skeletal muscle small arteries (ASK) with pronounced myogenic tone and mesenteric small arteries (AMS) with little myogenic tone. Myogenic tone was assessed by the vascular inner diameter at transmural pressures of 40 and 100 mmHg. To depress the Na+/Ca2+ exchanger, the extracellular Na+ concentration ([Na+]o) was lowered from 143 to 1.2 mM by substituting choline-Cl for NaCl. The ASK developed significant myogenic tone and constricted further in low [Na+]o. Nifedipine (1 microM) reduced both myogenic tone and low [Na+]o-induced contraction. Because the membrane potential of ASK was not changed by low [Na+]o (-35 +/- 2 mV at 143 mM [Na+]o, -37 +/- 3 mV at 1.2 mM [Na+]o), depolarization-induced Ca2+ influx was not a cause of the low [Na+]o-induced contraction. The AMS did not develop significant myogenic tone. Although low [Na+]o also constricted AMS, the magnitude of constriction was significantly weaker than that in ASK (17 +/- 4 vs. 47 +/- 6%, P < 0.01, at 58 mM Na+). With Bay K 8644, AMS developed myogenic tone, and low [Na+]o-induced constriction was significantly increased. In conclusion, Na+/Ca2+ exchanger may play an important role in regulating myogenic tone, likely via mediating Ca2+-extrusion.     

Effect of estrogen therapy on cerebral arteries during stroke in female rats

OBJECTIVE: To investigate the effect of estrogen therapy on the structural and functional properties of the middle cerebral artery during ischemia and reperfusion. DESIGN: Ovariectomized (OVX; n = 8) and ovariectomized with estrogen therapy (OVX+EST; n = 8) female Sprague-Dawley rats were exposed to 1 hour of ischemia using a model of temporary focal ischemia of the middle cerebral artery with 24 hours of reperfusion and compared to sham controls (CTL; n = 8). After occlusion and reperfusion, right middle cerebral arteries were removed from the brain and mounted on glass cannulas in a chamber that allowed for control over transmural pressure and measurement of lumen diameter. Lumen diameter was measured in response to increased transmural pressure (myogenic tone) as well as response to nitro-L-arginine, serotonin, and nifedipine. Cerebrovascular reactivity was compared to other stroke outcome measures, including infarct volume (%) and neurologic deficit. RESULTS: Serum estrogen was increased in OVX+EST rats (60.5 +/- 18.2 pg/mL) compared to OVX (0.2 +/- 0.2 pg/mL P < 0.05 vs OVX+EST) and CTL animals (1.3 +/- 1.0 pg/mL P > 0.05 vs OVX). OVX showed significantly less myogenic tone at 75 mm Hg (13.8 +/- 3.6%, P < 0.05 vs CTL) than CTL (29.8 +/- 4.7%) that was partially restored by estrogen therapy (21.2 +/- 4.5; P > 0.05). At serotonin concentrations of 10(-7) M, 3 x 10(-7) M, and 10(-6) M, the vessels from ischemic OVX rats showed significantly greater constriction (20.9 +/- 2.1%, 35.0 +/- 3.9%, and 39.4 +/- 3.4%, respectively) compared to nonischemic CTL rats (6.3 +/- 1.1%, 11.3 +/- 1.8%, and 16.8 +/- 2.5%, respectively P < 0.05). Estrogen therapy resulted in intermediate responses (18.2 +/- 5.3%, 25.2 +/- 6.6%, and 28.2 +/- 6.5%, respectively) that were not significantly different from the other groups. In addition, ischemia resulted in significantly greater dilation in response to 0.01 microM nifedipine in vessels from OVX animals (51.1 +/- 8.0%) compared to nonischemic CTL (18.0 +/- 3.8%; P < 0.05) and estrogen therapy resulted in an intermediate response (38.0 +/- 10.6; P > 0.05). Both reactivity to nitro-L-arginine and passive distensibility were not different among groups. There were no differences in percent infarct or neurologic deficit between ischemic groups. CONCLUSIONS: The influence of ischemia and reperfusion on vessel function was more dominant than that of estrogen therapy. However, estrogen therapy seemed to partially restore vessel function to similar levels as nonischemic vessels.     

Feasibility study of a direct endo-aortic clamp balloon

We have developed a new end-aortic clamp balloon catheter intended to be inserted directly into, thereby occluding, the ascending aorta. We examined the performance of this catheter in a canine model. We evaluated the extent of migration tolerance of the catheter under cardiopulmonary bypass perfusion in 12 mongrel dogs, weighing 20 kg, under general anesthesia. After institution of cardiopulmonary bypass, this catheter was inserted into the ascending aorta, and the balloon was inflated to occlude the ascending aorta. After the canine heart was arrested following the administration of cardioplegic solution, balloon migration was examined over a period of 3 hours, with hourly increases in perfusion pressure from 50 mm Hg to 80 mm Hg and finally to 100 mm Hg. After the migration test, ascending aortic wall sections, where the balloon was inflated, were examined microscopically. At internal balloon pressure of 300 to 400 mm Hg, migration occurred at perfusion pressure of > or =90 to 100 mm Hg. No histological differences were observed with use of the balloon catheter, compared with an extra-aortic clamp forceps. Based on these results, this device is safe, feasible, and can adequately occlude the ascending aorta during cardiopulmonary bypass. We conclude that this device is effective in patients weighing 20 kg.     

Development of microporous covered stents: geometrical design of the luminal surface

To reduce in-stent restenosis rates we have developed newly designed covered stents, in which a stent strut is buried into a microporous elastomeric cover film to provide a physical barrier against tissue ingrowth and a pharmacological reservoir for drug-eluting. The covered stents were prepared by dip-coating balloon expandable stents mounted on a stainless steel rod in a segmented polyurethane (SPU) solution, and were subsequently subjected to laser-processed microporing (pore diameter, 100 microm; interpore distance, 200 microm). The covered stents, which possessed flat luminal surfaces and micropores that were homogeneously arranged on the whole surface of the covering film, were deployed into the bilateral common carotid arteries of normal New Zealand white rabbits. Angiography after one month of implantation showed all stents were patent with little thrombus formation. The mean thickness of the formed neointimal layers was 292 +/- 177 microm (n=8), which was close to the size in non-covered bare stent (231 +/- 58 microm, n=7), but markedly decreased (about 2/3) from that in the previously developed wrapping-type covered stents (415 +/- 173 microm, P<0.01, n=8).     

Am80抑制血管内皮细胞增殖和血管新生内膜形成的机制研究

目的:探讨维甲酸衍生物Am80抑制血管内皮细胞增殖和大鼠颈总动脉内皮剥脱术后新生内膜增生的机制。方法:用不同浓度Am80处理EA-hy926细胞24 h后,应用细胞计数和MTS细胞活力分析检测细胞的增殖情况;将Am80处理的细胞进行PI染色,用流式细胞术检测细胞周期的变化情况;通过real-time PCR方法分析Am80处理后EA-hy926细胞中cyclin B1、P21和基质金属蛋白酶(MMP)-2表达的变化;制备SD大鼠颈总动脉内皮球囊损伤模型,通过HE和免疫组化染色方法,观察Am80对球囊损伤后新生内膜形成的影响。结果:细胞计数和MTS细胞活力分析结果显示,Am80以浓度依赖性方式抑制EA-hy926血管内皮细胞增殖;流式细胞分析显示,Am80可使EA-hy926细胞周期停滞在G2/S期;real-time PCR结果表明,Am80处理后,EA-hy926细胞中P21表达上调,cyclin B1和MMP-2表达水平降低;内皮损伤动物模型结果显示,Am80处理后新生内膜的形成受到显著抑制。结论:Am80可通过促进P21而抑制cyclin B1表达,从而抑制血管内皮细胞增殖和血管新生内膜的形成。     

Advanced glycosylation end-products and NO-dependent vasodilation in renal afferent arterioles from diabetic rats

Systemic pressor responses to acetylcholine (ACh) are reduced in DM, an effect thought to be related to quenching of nitric oxide (NO) by advanced glycosylation end-products (AGE). We studied the effects of AGE in juxtamedullary (JM) afferent arterioles (AA) from rats with 40-50 days diabetes mellitus (DM) induced via streptozotocin. JM AA were perfused in vitro with solutions containing fresh RBCs suspended in either 6% bovine albumin or 6% AGE-albumin in euglycaemic Krebs-Ringer. Autoregulatory responses were evident in the DM vessels: AA constricted 31 +/- 2% (n=9) when perfusion pressure (PP) was raised from 60 to 140 mmHg. ACh (10 microM) caused a 43 +/- 15% dilation and Ca2+-channel blockade elicited a 95 +/- 14% dilation at 100 mmHg PP, indicating substantial basal vascular tone in DM AA. L-NAME (0.1 mM) constricted DM AA by 21 +/- 2% (n=9) at 100 mmHg PP, indicating significant basal NO production in DM vessels. Segments of renal resistance arteries from DM rats perfused in vitro responded to muscarinic stimulation and elevated glucose levels with significant increments in NO production, as measured with an NO-sensitive electrode. This observation shows that the renal endothelial NO system is intact in DM. While AGE in the perfusate dilated control AA, they had no effect on DM AA at all PP levels, although they blunted ACh-induced dilation. Hence, although AGE do appear to have vasoactive properties in the absence of hyperglycaemia, the results of this study are inconsistent with substantial NO quenching by AGE.     

AT2R基因在体转染抑制大鼠颈动脉新生内膜增生

目的: 探讨AngⅡ 2型受体（AT2R）基因在体转染对大鼠颈动脉球囊损伤后新生内膜增生的抑制作用。方法:大鼠颈动脉球囊损伤后，局部转染AT2R重组腺病毒载体（pAdCMV/AT2R）或空病毒载体（pAd-GFP），于术后7、14和21 d用RT-PCR、免疫组织化学及HE染色方法，进行AT2R、AngⅡ 1型受体(AT1R)、PCNA在颈动脉壁中表达的变化及定量组织形态学分析；免疫荧光双标染色和激光共聚焦技术检测血管中AT2R与PCNA表达的关系。结果: pAdCMV/AT2R转染后，大鼠颈动脉AT2R的表达水平显著高于未转染组和pAd-GFP组(P<0.01)，21 d时仍维持较强表达。在14 d时pAdCMV/AT2R组PCNA阳性表达率显著低于未转染组和pAd-GFP组［(27.29±5.81)% vs ( 72.25±4.47)%、(68.43±9.12)%，P<0.01］，在AT2R表达阳性的部位PCNA表达阴性。在21 d时，pAdCMV/AT2R组的内膜面积与中膜面积比显著低于未转染组和pAd-GFP组(0.78±0.06 vs 1.44±0.22、1.36±0.21, P<0.01)，pAd-GFP组和未转染组间无显著差异（P>0.05）；各组颈动脉AT1R表达水平无显著差异(P>0.05)。结论: AT2R基因在体转染可抑制球囊损伤后大鼠颈动脉平滑肌细胞增殖和新生内膜增生，AT2R基因转染后表达并发挥其生物学作用时，AT1R和AT2R之间不存在表达量上此起彼伏的关系，可能是建立在信号转导基础上的功能调节关系。     

Cholecystokinin B-type receptors mediate a G-protein-dependent depolarizing action of sulphated cholecystokinin ocatapeptide (CCK-8s) on rodent neonatal spinal ventral horn neurons

Reports of cholecystokinin (CCK) binding and expression of CCK receptors in neonatal rodent spinal cord suggest that CCK may influence neuronal excitability. In patch-clamp recordings from 19/21 ventral horn motoneurons in neonatal (PN 5-12 days) rat spinal cord slices, we noted a slowly rising and prolonged membrane depolarization induced by bath-applied sulfated CCK octapeptide (CCK-8s; 1 microM), blockable by the CCK B receptor antagonist L-365,260 (1 microM). Responses to nonsulfated CCK-8 or CCK-4 were significantly weaker. Under voltage clamp (V H -65 mV), 22/24 motoneurons displayed a CCK-8s-induced tetrodotoxin-resistant inward current [peak: -136 +/- 28 pA] with a similar time course, mediated via reduction in a potassium conductance. In 29/31 unidentified neurons, CCK-8s induced a significantly smaller inward current (peak: -42.8 +/- 5.6 pA), and I-V plots revealed either membrane conductance decrease with net inward current reversal at 101.3 +/- 4.4 mV (n = 16), membrane conductance increase with net current reversing at 36.1 +/- 3.8 mV (n = 4), or parallel shift (n = 9). Intracellular GTP-gamma-S significantly prolonged the effect of CCK-8s (n = 6), whereas GDP-beta-S significantly reduced the CCK-8s response (n = 6). Peak inward currents were significantly reduced after 5-min perfusion with N-ethylmaleimide. In isolated neonatal mouse spinal cord preparations, CCK-8s (30-300 nM) increased the amplitude and discharge of spontaneous depolarizations recorded from lumbosacral ventral roots. These observations imply functional postsynaptic G-protein-coupled CCK B receptors are prevalent in neonatal rodent spinal cord.     

Reactivity of intrarenal arteries to vasoconstrictor and vasorelaxant polypeptides in adult stroke-prone spontaneously hypertensive rats.

The reactivity of intrarenal arteries to vasoconstrictor and vasodilator polypeptides was examined in adult stroke-prone spontaneously hypertensive rats (SHRSP). The contraction response to endothelin-1 (ET-1) was greater in SHRSP than in age-matched Wistar-Kyoto rats (WKY), and so was the pD2 estimate (8.05+/-0.03 in SHRSP, and 7.73+/-0.06 in WKY; n=5, P < 0.05). The contraction response to, and the pD2 estimate of, vasopressin were comparable in SHRSP and WKY. Neuropeptide Y did not contract the intrarenal arteries. In norepinephrine-precontracted arteries with intact endothelium, substance P and neurokinin A did not relax the arteries of either SHRSP or WKY, while calcitonin gene-related peptide (CGRP) induced a profound relaxation response. Relaxation response to CGRP was significantly greater in SHRSP than in WKY. Atrial, brain, and C-type natriuretic peptides (ANP, BNP, CNP), vasoactive intestinal polypeptide (VIP), and peptide histidine isoleucine (PHI) all caused relaxation responses, with a greater extent of relaxation to ANP, BNP, and VIP and a less extent to CNP and PHI. However, there were no significant differences in these relaxation responses between SHRSP and WKY. The current results revealed the character of heterogeneity of rat intrarenal arteries in response to vasoconstrictor and vasodilator peptides, and showed an enhanced reactivity to ET-1 and to CGRP in SHRSP.