脂质体与腺病毒转染EDRz抑制自体移植静脉内膜增生的比较研究

目的探讨以脂质体和腺病毒为载体,早期生长反应基因-1 DNA酶(Egr-1 DNA enzyme,EDRz)局部外用对自体移植静脉血管平滑肌(VSMC)增殖和内膜增生的抑制作用。方法大鼠建立自体静脉移植模型后随机分为脂质体组、腺病毒组和对照组,两实验组分别用脂质体-EDRz和腺病毒-EDRz涂抹移植静脉行在体转染。于术后1,2,6,24 h及3,7,14,28 d取材,荧光显微镜检测移植静脉的转染情况;采用原位杂交方法检测Egr-1 mRNA的表达;用免疫组织化学方法检测Egr-1蛋白表达,同时进行组织形态学观察。结果术后1 h,EDRz主要位于移植静脉的外膜、中膜和部分内皮细胞。脂质体组荧光灰度值为70.3±13.5,腺病毒组荧光灰度值为60.5±11.2。术后2～24 h,EDRz主要位于移植静脉的中膜;移植7 d,EDRz主要位于移植静脉的内膜。移植早期Egr-1蛋白表达主要位于中膜的血管平滑肌细胞(VSMC)和部分单核细胞、内皮细胞;移植后期未检测到Egr-1 DNA酶的表达。移植后期在中膜和新生内膜的VSMC均未检测到Egr-1蛋白的表达。移植2 h阳性表达率,脂质体组为(15.3±4.2)%,腺病...     

反义寡核苷酸抑制早期生长反应基因1表达对移植静脉内膜增生的影响

目的 研究反义寡脱氧核苷酸(antisense oligodeoxynucleotides,ASODN)抑制早期生长反应基因1(early growth response gene-1,Egr-1)表达对移植静脉血管平滑肌细胞增殖和内膜增生的影响.方法构建Egr-1 ASODN,建立自体静脉移植模型,Egr-1 ASODN转染移植静脉,术后随机分为1、2、6、24 h,3、7、14、28、42 d组,以未应用Egr-1 ASODN的大鼠为对照组.荧光显微镜检测Egr-1 ASODN转染移植静脉情况;应用原位杂交和RT-PCR方法检测Egr-1 mRNA的表达;联合应用免疫组织化学方法和Western blot检测Egr-1蛋白表达情况.结果 实验组移植1 h,Egr-1 ASODN主要位于移植静脉的外膜、中膜和部分内皮细胞(荧光灰度值为67±11),移植2 h至24 h,Egr-1 ASODN则主要位于移植静脉的中膜,移植7 d,Egr-1 ASODN主要位于移植静脉的内膜.移植后期未检测到Egr-1 ASODN的表达.Egr-1 mRNA的表达只呈现一个高峰(基因表达值1.8±0.5).移植早期Egr-1蛋白表达主要位于中膜的VSMC、部分单核细胞和内皮细胞,而移植后期在中膜和新生内膜的VSMC都未检测到Egr-1蛋白的表达.与对照组相比VSMC的增殖程度和内膜厚度均明显减轻(P＜0.01).结论 Egr-1 ASODN可显著抑制移植静脉的内膜增生,其作用可能是通过抑制Egr-1基因及其蛋白产物表达,从而抑制VSMC增殖、促进其凋亡而实现的.     

早期生长反应基因-1在自体移植静脉中的表达研究

目的研究自体静脉移植后早期生长反应基因-1(Egr-1)表达的动态变化,探讨其在内膜增生(IH)中的作用。方法 Wistar大鼠90只,建立自体静脉移植模型。术后分为1、2、6、24 h,3、 7、14、28、42 d组,取正常静脉作为对照。应用原位杂交和RT-PCR方法检测Egr-1 mRNA的表达,联合应用Western blot蛋白印迹和免疫组织化学方法检测Egr-1的蛋白表达。结果自体静脉移植后, Egr-1 mRNA和Egr-1蛋白的表达具有双相变化。移植后1 h,Egr-1 mRNA基因表达值为2．21±0．85。 6-24 h时下降,7 d时重新升高,28 d达高峰为3．16±1．14。移植早期2 h:Egr-1蛋白的表达阳性率为 31％±6％,24 h至3 d下降,28 d达高峰为41％±8％。免疫组化显示:移植早期Egr-1蛋白阳性表达主要位于中膜血管平滑肌细胞(VSMCs)和单核细胞／巨噬细胞;移植后期Egr-1蛋白阳性表达主要位于新生内膜和中膜的VSMCs,同时部分内皮细胞也有表达。结论移植静脉内膜增生与Egr-1的激活及表达关系密切,因而与移植静脉内膜增生及狭窄有关。     

Egr 1,PDGF B,TGF β1在自体移植静脉中的实验研究

目的研究移植静脉中早期生长反应基因(Egr)-1、血小板源性生长因子(PDGF)-B、转化生长因子(TGF)-β1的表达,探讨它们之间的关系及其在内膜增生(IH)中的作用.方法Wistar大鼠90只,建立自体静脉移植模型.术后随机分为1,2,6,24h,3,7,14,28,42d组,分别在相应时点取材,并设正常对照组.应用原位杂交和RT-PCR方法检测Egr-1、PDGF-B、TGF-β1的mRNA表达,联合应用Western蛋白印迹和免疫组织化学方法检测两组静脉中Egr-1,PDGF-B,TGF-β1蛋白表达情况,同时进行组织形态学研究.结果正常静脉中未检测到Egr-1,PDGF-B,TGF-β1 mRNA和蛋白的表达.移植静脉组Egr-1 mRNA在移植28d达高峰(45%±6%);PDGF-B mRNA在14d达高峰(48%±6%);TGF-β1 mRNA在7d达高峰(46%±9%).Egr-1蛋白表达在移植28d达高峰(40%±9%);PDGF-B蛋白在28d达高峰(45%±4%);TGF-β1蛋白在14d达高峰(41%±7%).结论移植静脉内膜增生与Egr-1,PDGF-B,TGF-β 1的表达关系密切;PDGF-B和TGF-β1的激活及表达可能受Egr-1的调节,同时也可能通过反馈机制促进Egr-1的高表达.     

Egr-1在自体移植静脉中的表达及意义

目的研究自体静脉移植后早期生长反应基因-1(Egr-1)表达的动态变化,探讨其在内膜增生中的作用。方法Wistar大鼠90只,将大鼠右颈总静脉端-端吻合于肾下腹主动脉建立自体静脉移植模型。术后随机分别于1、2、6和24h,3、7、14、28及42d相应时间处死动物取移植静脉,同时取正常静脉作对照。应用原位杂交和RT-PCR方法检测Egr-1mRNA的表达,联合应用Western蛋白印迹和免疫组织化学方法检测Egr-1蛋白表达情况,同时进行组织形态学观察。结果自体静脉移植后,Egr-1mRNA和Egr-1蛋白的表达呈双相变化,即移植后1h,Egr-1mRNA表达迅速升高,阳性率为(35±7)%,6h、24h及3d时下降到较低水平,阳性率分别为(8±2)%、(8±6)%和(8±4)%,7d时又再升高,28d时达高峰,阳性率为(45±6)%,此与其余各时点比较差异均有统计学意义(P<0.01),42d时,Egr-1mRNA的表达再次下降;移植早期(2h)即有Egr-1蛋白的表达,阳性率为(30±5)%,并持续至6h,24h~3d表达下降到较低水平,阳性率分别为(7±3)%和(7±8)%,7d时又再升高,至移植后28d,Egr-1蛋白的表达阳性率达到高峰,为(40±9)%,此与其余各时点比较差异有统计学意义(P<0.01)。移植后7d,免疫组化结果显示,Egr-1蛋白表达主要位于中膜血管平滑肌细胞(VSMCs)和单核细胞/巨噬细胞,移植后期28d,Egr-1蛋白表达主要位于新生内膜和中膜的VSMCs,同时部分内皮细胞也有Egr-1蛋白的表达。结论移植静脉内膜增生与Egr-1的激活及表达关系密切,Egr-1可能成为防治移植静脉内膜增生、狭窄及闭塞的一个新的干预靶点。     

p38 MAPK在自体移植静脉中的表达及其意义

目的　研究丝裂原活化蛋白激酶p3 8MAPK信号传导通路在自体移植静脉中的表达。方法　Wistar大鼠 80只 ,建立自体移植静脉模型。术后随机分为 6,2 4h ,3 ,7d和 2 ,4,6,8周等 8组 ,于相应时点取材 ,半定量逆转录PCR检测移植血管中p3 8MAPK的mRNA表达 ,Western蛋白印迹定量检测 p3 8的蛋白产物及磷酸化蛋白产物表达 ,原位杂交和免疫组化方法定位p3 8mRNA及蛋白表达。结果　移植静脉术后 6hp3 8的mRNA表达即较正常静脉明显增强 (P <0 .0 1) ,并于术后 2周达高峰 ,表达值为 (59± 2 6) % ,与 4,6,8周比较差异极显著 (P <0 .0 1)。Western蛋白印迹提示 p3 8在移植 2～ 4周达高峰 ,之后开始减少 ,8周时仍维持一定表达量 (1/4～ 1/2 )。原位杂交及免疫组化提示阳性表达多定位于移植血管中层或增生内膜中的血管平滑肌细胞 (VSMCs)。结论　p3 8MAPK通路的激活参与了移植静脉的内膜增生以及血管重塑 ,可望成为防治移植静脉狭窄闭塞的治疗靶点     

JNK、p38 MAPK在移植静脉血管重塑过程中的表达研究

目的　研究c Jun氨基末端激酶 (JNK)和p38蛋白激酶 (MAPK)在移植静脉血管重塑过程中的表达。方法　Wistar大鼠 80只 ,建立自体移植静脉模型 ,术后随机分为 6h ,1、3、7,1 4、2 8、4 2、5 6d等 8组 ,于相应时点取材 ,逆转录聚合酶链反应 (RT PCR)检测JNK和p38MAPK的mRNA表达 ,Western蛋白印迹检测JNK和p38的蛋白产物及磷酸化蛋白产物表达 ,原位杂交和免疫组化方法定位mRNA及蛋白产物表达 ,脱氧核苷酸转移酶末端标记法 (TUNEL)检测血管平滑肌细胞 (VSMC)凋亡的变化。结果　移植静脉术后 6h ,JNK和p38的mRNA表达增强 ,在术后 1 4d达到高峰 ,表达值分别为(2 6± 1 0 ) %和 (5 9± 2 6 ) %,与各时点比较差异有统计学意义 (P <0. 0 1 )。JNK、p38的蛋白产物表达在1 4～ 2 8d达高峰 ,在 5 6d时仍维持一定表达量 (1 .4～ 1 . 2 )。原位杂交及免疫组化提示阳性表达多位于移植血管中层或增生内膜中的血管平滑肌细胞 (VSMC) ,p38与凋亡呈正相关 (r =0 . 892 2 ,P <0. 0 1 )。结论　JNK和p38MAPK通路的激活是移植静脉内膜增生以及血管重塑的关键环节 ,可能成为新的治疗靶点。     

细胞外信号调节激酶在自体移植静脉中的表达

目的 探讨细胞外信号调节激酶(ERKs)在自体移植静脉中表达的变化规律。方法Wistar大鼠 80只,建立自体静脉移植模型,术后随机分为 6、24 h,3、7 d,2、4、6、8周等 8组,半定量逆转录-聚合酶链反应(RT-PCR)检测移植血管中 ERK1 mRNA表达,Western蛋白印迹定量ERK1/2的蛋白产物以及磷酸化蛋白产物的表达,原位杂交定位 ERK1 mRNA、免疫组织化学方法检测 ERK和增殖细胞核抗原(PCNA)的蛋白产物表达。结果 静脉移植后 6 h,ERK1 mRNA表达明显增强,与正常静脉比较差异有显著性(P<0.01),在移植7 d表达达高峰(33.2±14.2)％,与其余时点比较差异有显著性(P<0.01),4周后恢复至正常水平。Western蛋白印迹提示 ERK1/2在术后1～2周达高峰。阳性表达多定位于血管平滑肌细胞(VSMCs),ERK1与PCNA表达呈正相关(r=0.759 6,P<0.01)。结论 ERKs信号转导通路的激活可能是内膜增生的关键环节,可能成为防治移植血管狭窄、闭塞新的靶点。     

金属蛋白酶1组织抑制因子在大鼠自体移植静脉中的表达研究

目的 研究金属蛋白酶1组织抑制因子(tissue inhibitor of metalloproteinase-1,TIMP-1)在大鼠自体移植静脉血管平滑肌细胞中的表达和动态变化的意义.方法 建立大鼠自体血管移植模型,移植后不同时间分别切取移植静脉,应用HE染色、免疫组织化学和原位杂交方法动态观察TIMP-1的表达和变化情况.结果 移植血管组织病理学改变:血管移植后1周可见内膜增生(intimal hyperplasia:IH),2～4周达到高峰.原位杂交结果:TIMP-1mRNA在移植后24 h出现细胞阳性表达,72 h阳性表达明显增多,1-2周时表达达到高峰,与移植后1 d相比,差异有统计学意义(P<0.01).免疫组织化学染色:静脉移植后72 h出现TIMP-1的表达,1周时增加明显,2周时表达最强,与移植后1 d相比,差异有统计学意义(P<0.01).结论 在自体移植静脉中存在TIMP-1的激活.自体静脉移植于动脉后,内源性TIMP-1的分泌增加不足以抑制内膜增生.     

纳米粒子介导反义mTOR基因转染抑制移植静脉内膜增生

目的:观察以纳米粒子为载体的外源性反义雷帕霉素靶蛋白(mTOR)基因局部转染对移植静脉内膜增生的影响。方法:应用聚乳酸聚乙醇酸共聚物(PLGA)和聚乙烯醇(PVA)包载mTOR基因，制备纳米级粒子混合物。建立自体静脉移植模型72只，随机分成转基因组(转染以纳米粒子为载体的反义mTOR基因)，空载体组(单纯转染纳米粒子包载的空载体)和对照组(不予特殊处理)。分别于术后3，7，14，28d取材。检测mTOR基因的mRNA及蛋白产物表达，以及血管平滑肌细胞(VSMC)凋亡的动态变化。 结果:转基因组内膜中mTOR基因的mRNA及蛋白产物表达较其他两组明显减少(P<0.05)；转基因组内膜增生厚度于7，14，28d较其他组明显减少(P<0.01)；转基因组凋亡细胞较其他组明显增高(P<0.05)。结论:纳米粒子可以作为转基因载体。反义mTOR基因的表达能有效抑制自体移植静脉内膜的增生及促进VSMC凋亡。     

The effects of vasoactive agents on flow through saphenous vein grafts during lower-extremity peripheral vascular surgery

PURPOSE: The purpose of this study was to assess the effects of hemodynamic alterations on vein graft flow during peripheral vascular surgery. It was hypothesized that vasopressors can be administered without compromising flow through the vein grafts. SETTING: Tertiary care center, university medical center. Study DESIGN: Randomized placebo-controlled double-blinded study. METHODS: The effects of phenylephrine, epinephrine, milrinone, intravenous fluid, and placebo on newly constructed peripheral vein grafts were assessed in 60 patients (12 patients in each of 5 groups). Systemic and central hemodynamics were measured by using intra-arterial and pulmonary artery catheters. Vein graft flow was measured by using a transultrasonic flow probe (Transultrasonic Inc, Ithaca, NY). RESULTS: Phenylephrine increased systemic mean blood pressure (mBP) (68.2-94.0 mmHg, p < 0.01), systemic vascular resistance (SVR) (1,091-1,696 dynes x sec x cm(-5), p < 0.001), and vein graft flow (39.5-58.9 mL/min, p < 0.01), whereas cardiac output remained unchanged. Epinephrine resulted in increased cardiac output (4.4-6.9 L/min, p < 0.01) and mBP (72.7-89.1 mmHg, p < 0.01), whereas vein graft flow was reduced in 6 of 12 patients. Intravenous fluid administration resulted in a relatively smaller increase in graft flow (37.6-46.0 mL/min, p < 0.05), an increase in cardiac output, and an insignificant decrease in SVR. Other treatments had either little or no effect on vein graft flow. CONCLUSION: The study hypothesis was partly supported. Although both phenylephrine and epinephrine increased blood pressure, only the former increased vein graft flow in all patients. In conjunction with increases in graft flow after fluid administration, these data suggest that factors affecting vein graft flow are not just simply related to systemic hemodynamics.     

Effect of thromboxane synthetase inhibition on canine autogenous vein grafts

This study examined the effect of an orally active thromboxane (TXA2) synthetase inhibitor (TSI) on the patency, TXA2 production, and platelet accumulation of reversed autogenous vein grafts. Ten dogs received TSI (U-63557A) 10 mg/kg po q8 hr for 6 weeks, beginning 24 hr prior to surgery, while 15 control dogs were untreated. One jugular vein was harvested and stored in 37 degrees C saline for 1 hr to induce mild endothelial injury (stored). Normal and stored jugular vein grafts (8 cm) were then implanted in opposite femoral arteries while 3-cm segments of the same veins were implanted in the carotid arteries. Femoral graft flow was restricted with a 5 Fr distal arterial stenosis and patency determined by arteriography at 1, 2, 4, and 6 weeks. Vein graft endothelial surface TXB2 production was measured by RIA at graft implantation and in carotid grafts harvested at 1 week. 111In-labeled platelets were given iv 24 hr prior to carotid graft harvest to determine graft-platelet deposition. TSI treatment improved early (1 week) femoral vein graft patency from 63 to 89% (P less than 0.05), a trend that persisted for 6 weeks. Warm saline storage reduced 1-week graft patency from 83 to 63% (P less than 0.05), a difference that decreased with time. TSI treatment resulted in a marked decrease in TXB2 production, but was not associated with decreased 111In-labeled platelet deposition in carotid vein grafts. Warm saline storage increased graft-platelet deposition which was predominant at the arterial anastomoses. TSI treatment may improve early vein graft patency during the transient period of endothelial injury.     

Operative transluminal laser angioplasty as the sole treatment for late stenoses of femorodistal artery bypass graft: Experimental and clinical studies

To determine the role of Nd:YAG laser thermal angioplasty as the sole treatment for late stenoses of femorodistal artery bypass graft, the lasing effect of a larger size of hot-tip probe (3, 4, and 5 mm) was experimentally studied in vitro. For an adequate lasing effect, 30 watts of laser power output for 3 seconds was needed for the 3 mm probe, 40 watts for the 4 mm probe, and 50 watts for the 5 mm probe, respectively. Based on these results, we used Nd:YAG laser thermal angioplasty alone for 25 grafts, including 16 polytetrafluoroethylene (PTFE) grafts, eight saphenous vein grafts, and one externally supported (EXS) Dacron graft in which the stenotic lesions were detected by deterioration of the Doppler flow waveform pattern or a significant fall in the ankle/brachial pressure index (ABPI). Follow-up was from 3 to 24 months (average of 9 months) for PTFE grafts, from 5 to 21 months (average of 11 months) for saphenous vein grafts, and 13 months for the EXS Dacron graft following femorodistal artery reconstructions. Stenotic lesions were most common in the distal anastomotic sites: 11 PTFE grafts, three saphenous vein grafts, and one EXS Dacron graft. Among these, 13 grafts showed a type II flow waveform pattern at the time of surgery. Clinical success was achieved in 12 of the PTFE grafts (75%), in five of the vein grafts (62.5%), and in the single EXS Dacron graft. Four PTFE and three saphenous vein grafts failed subsequent to repeat intraoperative balloon angioplasty in three and graft extension in three and one graft interposition. Perforation occurred in only one vein graft. Continuing patency has now been maintained for up to 25 months after lasing. Nd:YAG laser thermal angioplasty using a 3 to 5 mm hot-tip probe is effective as the sole procedure for widening a stenotic lesion and improving patency after femorodistal artery reconstruction.     

经外膜缓释雷公藤内酯醇抑制自体移植静脉内膜增生

目的:探讨经外膜缓释雷公藤内酯醇（triptolide）对自体移植静脉内膜增生的抑制作用。方法:健康雄性新西兰大白兔24只，建立颈外静脉-颈总动脉移植模型。随机将动物等分为3组。空白组移植血管不给任何处理， F-127多聚凝胶对照组在移植血管外膜喷洒20 %F-127多聚凝胶0.5 mL，实验组在移植血管外膜喷洒携带雷公藤内酯醇300μg的F-127多聚凝胶0.5 mL。术后2周取标本。用组织形态学方法检测血管内膜增生程度，免疫组化检测标本中bcl-2和Fas的表达，TUNEL法检测标本中血管平滑肌细胞(VSMC)凋亡的水平。结果:静脉移植2周后，与空白组和F-127对照组比较，实验组血管内膜增生明显受抑制（P<0.05），bcl-2的表达［（18.2±8.4） %］显著减少，而Fas的表达［（21.4±8.9） %］显著增加，凋亡细胞［（28.4±7.6） %］也显著增加（P<0.05）。结论:经外膜缓释雷公藤内酯醇可有效抑制移植静脉内膜增生，这一作用可能系通过促进VSMC凋亡而实现的。     

The endothelin 1A receptor antagonist BSF 302146 is a potent inhibitor of neointimal and medial thickening in porcine saphenous vein-carotid artery interposition grafts

OBJECTIVE: Late saphenous vein graft failure after coronary artery bypass graft surgery is initiated by medial thickening and neointima formation, both of which are mediated by the proliferation of vascular smooth muscle cells. Because porcine vein grafts contain high levels of endothelin 1 receptor subtypes and endothelin 1 promotes the proliferation of vascular smooth muscle cells, the effect of administration of the endothelin 1(A) receptor antagonist BSF 302146 ([+]-[S]-2-[4,6-dimethyl-pyrimidin-2-yloxy]-3,3-diphenyl-butanoic acid) on porcine vein graft thickening was investigated. METHODS: Saphenous vein-carotid artery interposition grafting was performed in 4 groups of large white pigs (30-35 kg, n = 10 for each group). BSF 302146 was administered orally (3, 10, and 30 mg x kg(-1) x d(-1)) for 4 weeks to one group of pigs, and placebo was administered to the other group (control animals). Pigs were then anesthetized, and the grafts were removed and fixed at 100 mm Hg with 4% paraformaldehyde. Histologic sections were prepared, and graft morphometry was carried out by using computer-aided planimetry. RESULTS: In vein grafts from animals treated with BSF 302146 compared with grafts from control animals (untreated), there were significant dose-dependent reductions in the increase in medial thickness and neointimal thickness, an increase in luminal area, and a decrease in proliferating cell nuclear antigen-positive cells in the medial-intimal area. CONCLUSIONS: The administration of BSF 302146 reduces graft thickening and promotes positive remodeling through an endothelin 1(A)-mediated effect on vascular smooth muscle cell replication. The administration of this endothelin 1(A) receptor antagonist might therefore be therapeutically effective in preventing late vein graft failure in patients undergoing coronary artery bypass grafting.     

Prophylactic gamma radiation of unaffected vein grafts failed to prevent vein graft disease in a chronic hypercholesterolemic porcine model.

OBJECTIVE: The value of prophylactic brachytherapy on vein graft disease is unknown. METHODS AND RESULTS: Vein bypass grafts in 23 hypercholesterolemic pigs after ex vivo gamma irradiation of the vein grafts (10, 20, and 40Gy) and 16 control veins were analyzed regarding: (1) expression of platelet-derived growth factor (PDGF-AA and -BB, ELISA); (2) smooth muscle cell (SMC) proliferation/cell death (double-immunohistochemistry Mib-1/TUNEL/SMC alpha-actin); and (3) vessel wall dimensions. Planimetric data on vessel wall dimensions revealed no positive effect of gamma radiation on neointima formation and inner lumen diameter. On the contrary, vein grafts subjected to 40Gy were significantly more likely to be occluded and to have reduced inner lumen and increased neointima formation. Radiation therapy had no effect on PDGF expression and SMC proliferation/cell death. The mean inner lumen diameter decreased as PDGF-AA expression increased. CONCLUSIONS: Prophylactic gamma radiation of unaffected vein grafts failed to prevent vein graft disease in a hypercholesterolemic porcine model. High-dose radiation (40Gy) resulted in more frequent graft occlusion and vein sclerosis.     

Characterization of dopamine-mediated relaxation in experimental vein bypass grafts

BACKGROUND: Dopamine is an endogenous inotropic agent commonly used during coronary artery surgery and in the medical therapy of a revascularized patient. In this study the responses of intimal hyperplastic vein grafts to dopamine are examined. METHODS: The in vitro isometric tension responses to dopamine of common carotid jugular vein bypass grafts in New Zealand White rabbits were determined. The responses were compared to those obtained in the jugular vein and in the common carotid artery. Both endothelialized and denuded vessels were precontracted with prostaglandin F(2alpha) and the responses to dopamine were assessed. The contributions of nitric oxide and prostanoids to the response were also determined. RESULTS: Each vessel showed a biphasic dose response to dopamine with relaxation at low concentrations followed by contraction at high concentrations. Dopamine relaxation in the jugular vein was endothelial independent while in the carotid artery it was endothelial dependent and decreased. The sensitivity of both vessels was significantly greater than the vein graft (6.62 +/- 0.12; P < 0. 05); however, after endothelial denudation, the sensitivity of dopamine-mediated relaxation of the vein graft (8.91 +/- 0.09) was significantly enhanced. Preincubation with L-NMMA (to block NO synthesis) inhibited vein graft relaxation to dopamine and preincubation with indomethacin (to block cyclooxygenase activity) inhibited carotid artery relaxation to dopamine. Addition of phenoxybenzamine, a broad alpha-adrenergic antagonist, enhanced dopamine relaxation in the jugular vein and depressed the relaxation in the carotid artery. There was no effect on the dopamine response in the vein graft. Jugular vein and carotid artery responded to dopamine with cholera toxin-sensitive (Galpha(s)) responses. In contrast, dopamine relaxation in the vein graft was enhanced by inhibition of Galpha(s). CONCLUSION: Dopamine relaxation in vein grafts is mediated in part by NO but not by either prostanoids or alpha-adrenergic receptor activation. It is diminished compared to native vessels due to an endothelium-dependent, Galpha(s)-mediated pathway.     

The Effect of «Non-critical» (<50%) Stenosis on Vein Graft Longitudinal Resistance and Impedance

OBJECTIVE: vein graft stenoses <50% cause minimal flow impairment, velocity elevation, or symptomatology and are therefore usually assumed to be "non-critical". The purpose of this study was to assess the effect of <50% vein graft stenosis on vein graft longitudinal impedance, as elevated impedance has been found to correlate with clinical graft failure. METHODS: eight segments of non-reversed cryopreserved vein (mean length 23+/-1 cm; mean outer diameter 4.7+/-0.2 mm) were saline-perfused in vitro utilising a variable pulsatile perfusion pump, Windkessel, and clamp resistor simulating the haemodynamic conditions of arterial bypass. Proximal (Pprox) and distal (Pdist) pressure were continuously measured by fluid-filled catheter transduction, and flow (Q) by ultrasonic transit-time flowmetry. Waveforms were digitally recorded at 200 Hz at pulse rates ranging from 60-180 b.p.m. with mean flow (Q) of 154 ml/min and mean proximal pressure (Pprox) of 100 mmHg (max/min 120/90). Graded mid-graft stenoses of <50% were created using an inflatable vascular occluder and measured by the corresponding changes in mean pressure gradient (DeltaP=Pprox-Pdist) and Q (%stenosis=1-{DeltaPbaselineQstenosis/Delta PstenosisQbaseline}1/4). Vein graft longitudinal resistance (RL) was calculated as DeltaP/Q. After Fourier transformation, vein graft longitudinal impedance (ZL) was calculated as DeltaP/Q at each harmonic, with ZL determined by integration over 0-4 Hz. Results are reported as mean+/-S.E.M. RESULTS: the desired levels of pressure and flow were established in all vein segments. Graded inflation of the occluder resulted in vein graft stenosis of 23+/-3% and 39+/-3%. This was accompanied by a mild reduction in Q (12% and 30%) and considerable increases in both RL (180% and 710%) and ZL (140% and 430%). CONCLUSIONS: "non-critical" vein graft stenosis (<50%) causes minimal change in mean flow, but substantial elevations in longitudinal resistance and impedance. The contribution of "non-critical" stenosis to vein graft failure may be under-appreciated.     

The protective effect of vein cuffed anastomoses is not mechanical in origin

Purpose: Intimal hyperplasia (IH) is a proliferative process of vascular smooth muscle cells that occurs after an arterial injury, particularly at outflow anastomoses of prosthetic bypass grafts. IH causes stenosis that leads ultimately to graft flow reduction and thrombosis. We have demonstrated previously that vein cuff interposition between an expanded polytetrafluoroethylene (e-PTFE) graft and artery at distal anastomoses diminished IH formation in the arterial outflow as compared with noncuffed anastomoses. Improved long-term patency rates associated with the placement of an interposition vein cuff at the distal anastomosis of e-PTFE grafts to infrageniculate arteries have also been demonstrated clinically. This study examined the mechanical factors that may contribute to the protective effect of cuffed anastomoses. These factors include the expansibility of the vein cuff as compared with e-PTFE, as well as the angle of the cuffed anastomosis.Methods: Compatible animals were selected by use of platelet aggregation studies. Nine dogs, group A, received a 4 mm e-PTFE graft plus a 1 cm long interposition vein cuff at the distal anastomosis in the left carotid artery. The same procedure was done on the right side, and in addition the vein cuff was encircled by an e-PTFE jacket incorporated into the anastomosis to prevent the expansion of the vein cuff with arterial pulsation. To study the effect of distal anastomotic angle and geometry on the formation of IH, five dogs, group B, received a 4 mm e-PTFE graft in both sides. On the left, the distal anastomosis was performed between the graft and the artery at an acute angle as it is commonly done when a bypass graft is placed. On the right side a 1 cm long, 6 mm diameter e-PTFE segment was interposed between the artery and the graft at a perpendicular angle. This geometry mimicked the right angle of a vein cuff - to-artery anastomosis. After 10 weeks the grafts were harvested, and the thickness of IH was measured with an ocular micrometer under light microscopy.Results: In group A, one dog had bilateral graft thrombosis (12%), and these grafts were discarded. In the remaining eight dogs there was no statistically significant difference in the thickness of IH between the right (jacketed group) and the left side (nonjacketed/control group), showing that vein cuff expansibility did not play a role in protecting against the formation of IH. In group B, bilateral graft thrombosis occurred in four of five dogs (80%), suggesting that the perpendicular anastomotic angle was not protective.Conclusion: These results suggested that the protective effect of the vein cuff is not mechanical in origin. (J VASC SURG 1995;21:558-66.)