剪切应力对毛细血管内皮细胞代谢的影响

建立的平行平板流动腔装置适用于研究血管内皮细胞代谢对剪切流场的响应。将培养的人胚肾小球血管单层内皮细胞置于剪应力分别为５×１０－５Ｎ／ｃｍ２,１×１０－４Ｎ／ｃｍ２和１．５×１０－４Ｎ／ｃｍ２的定常层流中剪切２５小时,样品中的内皮素分泌量用放射免疫法测定。结果表明,剪应力水平对内皮细胞内皮素的代谢活动有显著影响。与静态培养对照,低水平的剪应力（５×１０－５Ｎ／ｃｍ２、１×１０－４Ｎ／ｃｍ２）促进内皮素的分泌,而较高水平的剪应力（１．５×１０－４Ｎ／ｃｍ２）抑制内皮素的分泌;剪应力对内皮素累积含量的影响比之分泌速率更大     

内皮细胞代谢与剪切作用时间的相关性

应用平行平板流动腔装置研究毛细血管内皮细胞内皮素（ＥＴ）代谢与剪切作用时间的相关关系。将培养的人胚肾小球血管单层内皮细胞置于剪应力分别为０,５×１０＾－５,１×１０＾－４和１．５×１０＾－４Ｎ／ｃｍ＾２的定常层流中切作用２５小时,样品的ＥＴ分泌量用放射免疫法测定,结果表明,剪切作用时间与内皮细胞ＥＴ的代谢活动有密切相关,ＥＴ分泌量高低不仅限决于剪应力大小,而且还取决于剪切作用时间长短,ＥＴ分泌量随     

细胞内外钙离子浓度对鲎腹神经感光器光适应的影响

用细胞内记录的方法研究了由微弱持续光刺激（６×１０＾６￣９×１０＾６光子／ｃｍ＾２,１０ｓ引起鲎（Ｌｉｍｌｕｓ ｐｏｌｙｐｈｅｍｕｓ）腹神经光器膜电流的变化－－光碰击。结果表明,在生理盐水（１０ｍｍｏｌ／ＬＣａ＾２＋）中光碰击的平均面积为（３９．５±１．７６）ｐＣ,微弱光适应（记录前２．５ｓ加１次光闪,９×１０＾９光子／ｃｍ＾２）使得光碰击的面积下降至（１０．５±２．２９）ｐＣ（ｎ＝４）。在低钙溶     

低强度HeNe激光辐照人体外周血对淋巴细胞染色体影响的研究

本文通过低强度Ｈｅ－Ｎｅ激光以能量密度分别为１４．３１Ｊ／ｃｍ＾２（辐照５’）、２８．６２Ｊ／ｃｍ＾２（辐照１０）、５７．２４Ｊ／ｃｍ＾２（辐照２０）１１４．５２Ｊ／ｃｍ＾２（辐照４０）燠夫体外周血后,检测其淋染色畸变率（ＣＡ）,激光照射血样（能量密度由低到高）未照射血样ＣＡ分别平均为４．２９‰、３．９６‰、３．８１‰、３．５９０‰、４．１９‰、Ｘ＾检测无显著差异,说明低强度的Ｈｅ－Ｎｅ激光辐照人     

2.5次微分伏安法对生物品中丙二醛的测定

以０．１ｍｏｌ／ＬＮＨ４Ｃｌ溶液为介质,用２．５次微分伏安法测定了丙二醛,线性范围为１．０＊１０＾－６至１．０＊１０＾－３ｍｏｌ／Ｌ,检测限达１．０＊１０＾－７ｍｏｌ／Ｌ。并测定了细胞培养液介质中新生ＳＤ大鼠室肌细胞样品的丙二醛。     

510.6nm激光照射对兔血管平滑肌细胞增殖的影响

本文用５１０．６ｎｍ 波长激光以功率密度１、５、１０ ｍ Ｗ／ｃｍ ２ 和能量密度２、４、６Ｊ／ｃｍ ２ 照射体外培养的兔血管平滑肌细胞（ＳＭＣ）,通过３Ｈ－ ＴｄＲ掺入率和细胞生长曲线测定细胞增殖率。结果显示,上述激光照射量均能抑制细胞增殖率,其中以１０ｍ Ｗ／ｃｍ ２ 组的作用最为显著     

剪切流场中内皮细胞膜张应力累加效应的实验研究-离体血管段长度与其蛋白质代谢的相关性

用离体血管灌流试验验证冯元桢等关于血管内皮细胞的膜张应力逆血流方向轻加的理论分析。用０．１２Ｎ／ｍ＾２剪应力剪切人脐静脉段内皮细胞２０ｈ后,两种不同长度离体血管的内皮素平均分泌速率无显著差异,但在分泌速率的曲线形态,特征方程和最大分泌速率,最小分泌速率及分泌速率变异系数上差异较大;ＡＴⅡ的平均分泌速率差异彩显著,１１ｃｍ处理比２１ｃｍ处理高６８％。     

不同钙离子浓度对鲎腹神经光感受器二种光碰击的影响

在生理盐水中用持续的弱光（６＊１０＾６－９＊１０＾６个光子／ｃｍ＾２）刺激鲎的腹神经光感受器细胞可得到二种类型的碰击,一种称谓“标准光碰击”或“Ｃ２碰击”,它有对称的形状,信号衰退的指０数常数大于０．０１／毫秒。     

杜氏盐藻细胞质膜氧化还原系统

杜氏盐藻细胞质膜具的氧化ＮＡＤ（Ｐ）Ｈ,还原Ｆｅ（ＣＮ）＾３－６和Ｏ２的氧化还原系统。当Ｆｅ（ＣＮ）＾３－６浓度为０．６ｍｍｏｌ／Ｌ,氧化ＮＡＤＨ的Ｋｍ为９６μｍｏｌ／Ｌ,Ｖｍａｘ为１５９ｎｍｏｌ１０＾－８ｃｅｌｌｓｍｉｎ＾－１,最适ｐＨ为８．５。ＴｒｉｔｏｎＸ－１００可促进ＮＡＤＨ和Ｆｅ（ＣＮ）＾３－６的氧化还原活性。ＮＡＤＨ能促进藻细胞的氧吸收,最适ｐＨ为８．５。在无外源电子供体存在时,细胞质     

癫痫大鼠大脑皮质及海马神经元NOS的变化

给大白鼠侧脑室注射马桑内酯（Ｃｏｒｉａｒｉａ Ｌａｃｔｏｎｅ, ＣＬ）（１７５×１０－ ２ｍ ｏｌ／Ｌ２μｌ）后可诱发癫痫,用ＮＡＤＰＨｄ 组织化学方法观察大脑皮质及海马ＮＯＳ阳性神经元的变化, 结果： 大脑皮质ＮＯＳ阳性神经元数目逐渐增加, 至２ｈ 达高峰, 与生理盐水组相比差异具有非常显著性意义（Ｐ＜ ００１）, 随着ＣＬ作用时间延长ＮＯＳ反应由弱变强;海马区ＮＯＳ阳性神经元２ｈ 时才出现染色明显加深。对体外培养的大脑皮质及海马神经元用ＣＬ （２５×１０－ ５ｍ ｏｌ／Ｌ） 作用１／２ｈ、１ｈ、２ｈ、４ｈ 后ＮＯＳ阳性神经元均未见明显增加。     

血管内皮细胞内皮素代谢的数值分析

将培养的人胚肾小球血管单层内皮细胞置于剪应力分别为6．5dyn/cm^2和13．0dyn/cm^2的定常层流中剪切10小时,样品中的内皮素（ET）分泌量用放射免疫法测定。结果表明,剪切应力和剪切作用时间对内皮细胞内皮素的代谢均有显著的影响,其影响不是简单的线性增减,而呈较复杂的非线性特征,内皮素累积含量和分泌速率,随剪切时间的变化的关系可用Logistic方程来描述,获得了反映内皮素（ET）分泌规律的大量特征方程和特征数,为了解体内发生于血管壁的病理生理过程中内皮素分泌规律提供了实验数据。     

Secretory response of endothelin-1 in cultured human glomerular microvascular endothelial cells to shear stress

The shear-induced secretory response of endothelin-1 (ET-1) by human microvascular endothelial cells was studied using paired human glomerular microvascular endothelial cell (HGMEC) cultured monolayers exposed to steady-state laminar shear stress for up to 10 hours. The first cell monolayer was subjected to a shear stress of 0.65 N m-2 and the second, 1.3 N m-2. ET-1 secretion was determined by radioimmunoassay. Over 10 hours of shear, the total cumulative secretion of ET-1 was 237.4 pg/cm2 for the monolayer exposed to 1.3 N m-2 and 143.6 pg/cm2 for the monolayer exposed to 0.65 N m-2. The average ET-1 secretion rate was 20.90 +/- 2.15 and 12.45 +/- 1.05 pg/cm2.h at 0.65 N m-2 and 1.3 N m-2, respectively. The results showed that ET-1 secretion varied with the time of shear in a nonlinear fashion. Although the level of shear stress affected the absolute value of ET-1 cumulative secretion and secretion rate, the major secretion period for both monolayers occurred between 2.0 and 8.0 hours, with the peak secretion rate occurring at approximately 5 hours. Thus, the response of cultured human microvascular endothelial cells to shear stress differed from that of large vessel endothelial cell cultures in terms of ET-1 secretion. In addition to the level of shear stress, the time of shear was also an important determinant of ET-1 secretion. Consequently, the heterogeneity of vascular endothelial cells and the time of shear should both be considered in future research on the secretion of vascular endothelial cell cultures.     

牛肺动脉单层内皮细胞长度与其血管紧张素II代谢的相关性

用离体培养的牛肺动脉内皮细胞灌流实验研究内皮细胞单层长度与其血管紧张素II代谢的相关性。牛肺动脉单层内皮细胞暴露于剪应力为0.64N/m2 的剪切流中24h后 ,两种不同长度(10cm和6cm)单层内皮细胞的血管紧张素II的平均分泌率有比较显著差异 ,10cm处理的血管紧张素II平均分泌率 (8.61±0.28pg/cm2.h)比6cm处理 (6.14±0.12pg/cm2.h)高40 % ,10cm处理的最小分泌率 (7.55pg/cm2.h)较6cm处理 (5.75pg/cm2.h)高31 % ,10cm处理的最小分泌率出现的剪切时间点比6cm处理要早6个小时。表明牛肺动脉内皮细胞单层长度与其血管紧张素II代谢 (分泌率 )间有密切的相关关系 ,进而从细胞代谢角度间接证实血管内皮细胞膜张应力存在累积效应。     

Albumin permeability across endothelial monolayers under pulsatile shear stress

Recent studies suggest that the temporal gradient of shear stress that is generated by blood flow plays an important role in the pathology of arteriosclerosis. We focused on the temporal gradient of shear stress and measured the permeability of albumin under steady or pulsatile shear stress conditions. Porcine aortic endothelial cells were seeded on a membrane filter and subjected to steady or pulsatile shear stress (1 Hz) at 1 Pa for 48 h, and the permeability of albumin was measured over time. The permeability increased gradually under steady flow but increased acutely under pulsatile shear stress. In particular, the maximum permeability of albumin differed under these conditions. The value was 4.2 × 10^?5 cm/s at 18 h under pulsatile shear stress and 2.8 × 10^?5 cm/s at 48 h under steady shear stress. The permeable route of albumin was examined using isoproterenol, which decreases junctional permeability. The increase in albumin permeability with pulsatile shear stress was decreased by isoproterenol. These results suggest that the increased permeability of albumin with pulsatile shear stress was related to trafficking through paracellular junctions. Thus, pulsation may promote a mechanotransduction process that differs from that of steady shear stress, and these pulsation effects likely play an important role in the permeability of macromolecules.     

Shear stress induced stimulation of mammalian cell metabolism

A flow apparatus has been developed for the study of the metabolic response of anchorage-dependent cells to a wide range of steady and pulsatile shear stresses under well-controlled conditions. Human umbilical vein endothelial cell monolayers were subjected to steady shear stresses of up to 24 dynes/cm(2), and the production of prostacyclin was determined. The onset of flow led to a burst in prostacyclin production which decayed to a long term steady state rate (SSR). The SSR of cells exposed to flow was greater than the basal release level, and increased linearly with increasing shear stress. This study demonstrates that shear stress in certain ranges may not be detrimental to mammalian cell metabolism. In fact, throughout the range of shear stresses studied, metabolite production is maximized by maximizing shear stress.     

Oscillatory shear alters endothelial hydraulic conductivity and nitric oxide levels

This study addresses the role of nitric oxide (NO) and downstream signaling pathways in mediating the influences of oscillatory shear stress on the hydraulic conductivity (L(p)) of bovine aortic endothelial cell (BAEC) monolayers. Exposure of BAEC monolayers to 20 dyne/cm2 steady shear stress for 3 h induced a 3.3-fold increase in L(p). When an oscillatory shear amplitude of 10 dyne/cm2 was superimposed on a steady shear of 10 dyne/cm2 to produce a non-reversing oscillatory shear pattern (10+/-10 dyne/cm2), L(p) increased by 3.0-fold within 90 min. When the amplitude was increased to 15 dyne/cm2, resulting in a reversing oscillatory shear pattern (10+/-15 dyne/cm2), the increase in L(p) over 3 h was completely suppressed. Twenty and 10+/-10 dyne/cm2 induced 2.9- and 2.6-fold increases in NO production above non-sheared controls, respectively, whereas 10+/-15 dyne/cm2 stimulated a 14-fold increase in NO production. The inhibition of L(p) with reversing oscillatory shear may be associated with alterations in cyclic guanosine monophosphate (cGMP) production downstream of NO which is up-regulated by reversing oscillatory shear, but is unaffected by steady shear.     

Shear stress attenuates endothelin and endothelin-converting enzyme expression through oxidative stress

Shear stress is known to dilate blood vessels and exert an antiproliferative effect on vascular walls. These effects have partly been ascribed to shear stress-induced regulation of the secretion of endothelium-derived vasoactive substances. In this study, to elucidate the role of shear stress in endothelin production by endothelial cells, we examined the effect of physiological shear stress on the mRNA expression of endothelin-converting enzyme-1 (ECE-1) as well as endothelin-1 (ET-1) in cultured bovine carotid artery endothelial cells (BAECs) and human umbilical vein endothelial cells (HUVECs), using a parallel plate-type flow chamber. ECE-1 mRNA expression was significantly down-regulated by shear stress in an intensity- and time-dependent manner within the physiological range (1.5 to 15 dyn/cm(2)). ET-1 mRNA expression decreased together with ECE-1 mRNA expression. Shear stress at 15 dyn/cm(2) for 30 min induced a significant increase in the intracellular peroxide concentration, and the down-regulation of ECE-1 and ET-1 mRNA expression by shear stress was attenuated almost completely on treatment with N-acetyl cysteine (NAC), an antioxidant (20 mM). Furthermore, when H(2)O(2) (0.5 to 2 mM) was added to BAECs in static culture, the ECE-1 as well as ET-1 mRNA expression was attenuated in proportion to the concentration of H(2)O(2). It is suggested that endothelial cells sense shear stress as oxidative stress and transduce signal for the regulation of the gene expression of ECE as well as ET to attenuate vascular tone and inhibit the proliferation of vascular smooth muscle cells.     

Hemodynamic shear stress stimulates endothelin production by cultured endothelial cells

We have examined the effect of shear stress on the production of endothelin by cultured porcine endothelial cells. Low shear stress stimulated the expression of endothelin mRNA in polygonal endothelial cells with a peak time of 2 to 4 hours and also increased the release of immunoreactive endothelin into the culture medium. The expression of endothelin mRNA in the ellipsoidal endothelial cells under higher shear stress was not different from that of the control level. Our results suggest a possible role for hemodynamic shear stress in the regulation of endothelin production in vascular endothelial cells.     

Cytokine stimulated endothelin release from endothelial cells

Endothelin release from bovine endothelial cells of the aorta, pulmonary artery, and retinal microvessels was measured in response to various cytokines. Transforming growth factor beta (0.05-5 ng/ml) was found to be a potent stimulator (3-4 fold increase) of endothelin secretion in all three cell types. Tumour necrosis factor alpha (0.1-10 ng/ml) and interferon gamma (8-800 U/ml) had a small (1.5-2 fold increase) but significant effect on endothelin secretion from endothelial cells of large vessels but not the retinal microvessels. Interleukin-1 beta, Interleukin-6 and interleukin-8 at various doses did not affect endothelin secretion. These effects were observed at various time points from 6-24 hrs and indicate that of the cytokines tested, only transforming growth factor beta has a potent effect on endothelin release from endothelial cells of different organs.