Linear gap and tight junctional assemblies between capillary endothelial cells in the eel rete mirabile

Background: Interendothelial tight junctions and gap junctions have been described in large blood vessels and in cultures of endothelium derived from large blood vessels. Transfer of microinjected smallmolecular weight tracers between adjacent endothelial cells also has been demonstrated indicating the presence of gap junctional interendothelial communication. Similar transfer of tracers is evident between microvessel endothelial cells in culture and in microvessels in situ. However, gap junctions have not been detectable by electron microscopy of intact capillary systems. This may be due to limited sampling available in diffuse capillary systems and a small area of overlap between adjacent endothelial membranes. Methods: Thin slices of the parallel, tightly packed capillary bed of the eel rete mirabile were cryofixed and prepared for conventional TEM by freeze substitution. Other samples were freeze-fractured and replicated for examination of endothelial junctional components. Results: A novel tight-gap junctional complex between rete capillary endothelial cells is described. In freeze-fracture replicas of the membrane P face, rows of gap junction subunits are flanked on either side by linear depressions representing grooves previously occupied by tight junctional strands that partition to the E face. In thin sections, the junctions appear in profile as short lengths of closely apposed membranes characteristic of gap junctions. Conclusions: The tight junctional components imply a barrier to paracellular transport across the capillary wall between the endothelial cells. The gap junctional component may provide a mechanism for communication between endothelial cells along the length of the vessel wall. © 1995 Wiley-Liss, Inc.     

肾上腺髓质素2对大鼠脑微血管内皮细胞增殖的影响

目的：研究肾上腺髓质素2（AM2）对大鼠脑微血管内皮细胞增殖的影响。 方法： 分离并培养SD大鼠脑微血管内皮细胞，经Ⅷ因子相关抗原的抗体鉴定和常规处理后，随机分为对照、AM2（10^-7 mol/L、10^-8 mol/L和10-9 mol/L）、ADM、ADM+AM2、10%胎牛血清和10％胎牛血清＋AM2 10-7 mol/L等8组，以［3H］-TdR掺入法测定MEC增殖反应。 结果： 10^-7-10^-9 mol/L各浓度AM2、ADM以及AM2和ADM合用对于静止状态的脑微血管内皮细胞［3H］-TdR掺入与对照组比较均无明显差异（均P>0.05）。10%胎牛血清刺激组脑微血管内皮细胞［3H］-TdR掺入比对照组高87.5%（P<0.05），10^-7mol/L AM2抑制胎牛血清诱导的脑微血管内皮细胞［3H］-TdR掺入增加（P<0.05）。 结论： AM2抑制血清诱导的脑微血管内皮细胞增殖。     

香烟尘粒对人脐静脉内皮EA.hy926细胞的损伤作用

目的:选用人脐静脉内皮EA.hy926细胞株作为研究对象,观察二甲基亚砜溶解的香烟尘粒(DSP)对人脐静脉内皮EA.hy926细胞生长的影响。方法:以(1、2、4、8)mL/L剂量DSP作量效实验,小剂量DSP(2mL/L)作时效实验,采用MTT比色法和96孔板细胞蛋白测定方法来评价DSP对该细胞株增殖和活性的影响。透射电镜(TEM)观察不同处理因素作用后细胞超微结构变化。结果:DSP能抑制人脐静脉内皮EA.hy926细胞增殖(P<0.05),且对该细胞株具有明显毒性,它能减少细胞蛋白合成(P<0.05)、增加细胞死亡(主要为坏死),作用呈剂量和时间依赖。结论:DSP能损伤血管内皮细胞(VEC)。     

Endothelial Regulation of Vascular Repair: Role of bFGF in Paracrine Pathways

Vascular repair following injury is mediated by both endothelial and smooth muscle cells often through paracrine pathways. Basic fibroblast growth factor (bFGF) is present at sites of vascular injury. The role of bFGF in regulating reendothelialization through an effect on centrosome redistribution in cell migration is discussed. The role of bFGF in neointimal formation, especially as it relates to smooth muscle cell proliferation, is reviewed. It is concluded that bFGF appears to be an important agent regulating the early responses of the artery wall to injury. Presented in part at the Molecular Endocrine Pathology Symposium at the International Academy of Pathology XXI International Congress, Budapest, Hungary, October 20–25, 1996.     

Ultrastructural localization of lectin receptors on cerebral endothelium

Summary Oligosaccharide residues on the endothelial luminal plasma membrane of rat cerebral cortical vessels were localized using biotinylated lectins. In addition, the effect of pretreatment of brain slices with neuraminidase prior to the binding of cationized ferritin (CF) and certain lectins was studied.Conjugates of biotinylated lectins and avidin-d horseradish peroxidase reaction product were evenly distributed on the endothelium of arterioles, capillaries, and venules. Lectin binding sites were observed on the plasma membrane of pinocytotic vesicles open onto the vascular lumen and at the luminal end of the interendothelial space only. The following sugar residues were localized: -d-mannosyl, -d-glucosyl, -N-acetylglucosaminyl, sialyl,d-galactosyl, -l-fucosyl, and -N-acetyl-d-galactosaminyl.Following pretreatment of brain slices with neuraminidase -d-gal-(1–3)-d-galN-acetyl groups were demonstrated on endothelium. In this respect, cerebral endothelium differs from noncerebral endothelium which is reported to have peanut agglutinin binding sites without neuraminidase pretreatment.Anionic groups on cerebral endothelium were demonstrated at the same locations as the lectin binding sites. Following neuraminidase pretreatment there was reduction, but not absence, of CF binding supporting the observation that surface charge is not wholly due to sialyl groups.The role of monosaccharide residues in states of altered cerebrovascular permeability remains to be determined.Supported by Ontario Heart Foundation grant no. 2-6     

Microangiopathy in human diabetic neuropathy

Summary Morphological change of endoneurial and perineurial vessels accompanied severe loss of myelinated axons in peripheral nerves of each of 17 patients with diabetic neuropathy. Vascular mural thickening averaged 18.9±9.9 m² in diabetic capillaries (n=11) vs. 6.9±4.1 m² in controls (n=7). Electron microscopy revealed vigorous endothelial proliferation as well as thickening and reduplication of basal lamina in each instance. Particular attention was paid to vessels which penetrate the perineurium en route to the endoneurial intertitium, since they provide a major portion of the endoneurial blood supply. Luminal narrowing and mural thickening of these vessels was compounded by basal laminar thickening of the perineurium. Fenestrated endoneurial capillary endothelium was noted in one case. Both demyelination and axonal degeneration were observed with intra-axonal glycogen accumulation in some axons. Morphometric analysis revealed extensive myelinated nerve fiber loss in diabetic nerves. These morphological findings emphasize the impact of diabetic microangiopathy on specialized endothelium and suggest that local anatomic factors in the perineurial sheath render the nerve vulnerable to chronic ischemia.Supported in part by the National Institute for Communicative Disorders and Stroke NS-14162 and by the Veterans Administration Research Service     

Effect of endothelium on basal and α-adrenoceptor stimulated calcium fluxes in rat aorta

Summary The rate of unstimulated influx of Ca²⁺ into rat aorta smooth muscle, measured as uptake of ⁴⁵Ca, was inhibited in the presence of endothelium as compared to influx in the absence of endothelium. Efflux of ⁴⁵Ca from unstimulated prelabelled tissues was also reduced in the presence of endothelium. In normal physiological solution the rate of influx and efflux of Ca²⁺ stimulated by B-HT 920 (1 and 10 M), but not that stimulated by phenylephrine (30 nM and 1 M), was also reduced in the presence of endothelium. In the presence of the calcium entry blocker flunarizine (3 M), phenylephrine (1 M) stimulated efflux of Ca²⁺ was inhibited by the presence of endothelium. A correlation between inhibition of Ca²⁺ influx and modulation of -adrenoceptor agonist-induced contractions by endothelium could not be demonstrated, and methylene blue, an antagonist of endothelium mediated inhibition of B-HT 920 contractions, did not affect Ca²⁺ influx stimulated by the agonist. The effects of endothelium on Ca²⁺ influx and efflux are unlikely to be due to alterations by endothelium of diffusion of ⁴⁵Ca or the agonists in the vessel. The results demonstrate that an endothelial derived factor or factors can reduce calcium influx into smooth muscle cells and also modulate the release of calcium from cells, perhaps by affecting intracellular calcium pumping mechanisms. A reduction of calcium influx cannot be the sole explanation for the modulatory effect of endothelium on -adrenoceptor agonist-induced contractions but an effect on intracellular calcium metabolism may be important.     

血清血管内皮生长因子测定在鼻咽癌检测中的意义

目的：探讨血清血管内皮生长因子能否作为鼻咽癌的肿瘤标志物,并作为鼻咽癌诊断与分期检测的指标。方法：对88例鼻咽癌患者和60例鼻咽颈部良性病变及73例正常人进行血清血管内皮生长因子的定量测定。结果：鼻咽癌患者与鼻咽颈部良性病变、正常人比较和鼻咽癌临床各期比较血清血管内皮生长因子含量有显著性的差异。结论：血清血管内皮生长因子含量测定可作为鼻咽癌的发现诊断和临床分期简便可靠的检测指标。     

角膜内皮细胞损伤后早期超微结构改变

目的：了解角膜内皮细胞损伤的超微结构特征及其临床意义。方法：对20只成年灰兔进行定量角膜内皮细胞损伤,伤后定期进行眼部裂隙灯检查、角膜厚度及眼压测定,预期取角膜材料进行透射电镜和扫描电镜检查。结果：角膜内皮细胞损伤后1天可见细胞膜破损,细胞肿胀,细胞器颗粒粗大;伤后3天内皮细胞崩解,胞质脱落,胞核裸露,伤后5天出现细胞缺损区,膜脂降解聚积而形成脂质球,附着于细胞缺损区,角膜上皮细胞音隙增宽;伤后7天角膜内皮细胞移行修复细胞缺损区;伤后9天后内皮细胞异形明显。上皮细胞出现变性。角膜混浊与角膜厚度呈正相关,眼压增高者角膜厚度增加,内皮细胞损伤加重。结论：超微结构结果提示,角膜内皮细胞受损后细胞崩解似科是必然的结局。动态测定角膜厚度可以判断角膜内皮细胞损伤的程度,控制眼压是预防内皮细胞损伤加重的重要措施之一。     

大鼠提睾肌神经损伤后Bcl-2、Bax和P_(53)在血管平滑肌细胞和内皮细胞的表达

目的　研究大鼠提睾肌神经损伤后血管平滑肌细胞和内皮细胞的Bcl -2、Bax及P53 表达和意义。方法以免疫组织化学SP法 ,对大鼠提睾肌神经损伤后的血管平滑肌细胞和内皮细胞的Bcl -2、Bax及P53 表达进行研究。结果　支配提睾肌的神经损伤后 ,Bcl-2、Bax和P53 均有表达。在平滑肌细胞中 ,Bcl -2的表达明显强于Bax和P53,而在内皮细胞Bax和P53 的表达强于Bcl-2。结论　大鼠提睾肌损伤后平滑肌细胞有增殖现象 ,而内皮细胞则可能出现过度凋亡 ,上述改变可能对微循环产生不利影响。