氧浓度对人髓核间充质干细胞生物学特性的影响

目的 :分离培养髓核来源的间充质干细胞(MSCs),比较不同氧浓度下细胞的生物学特性,探讨氧浓度对椎间盘退变机制的影响。方法:用胶原酶消化法从手术摘除的4个腰椎间盘(椎间盘Pfirrmann分级为Ⅰ级或Ⅱ级)髓核组织中分离MSCs,体外培养、传代,观察记录细胞形态。取P3代细胞,用流式细胞仪对分离得到的细胞表面抗原CD90、CD73、CD105、CD44和CD31、CD34、CD45的表达情况进行检测;用成骨、成脂、成软骨培养液诱导培养细胞,分别在21d、28d、21d时用茜素红、油红O、甲苯胺蓝对细胞进行染色,观察其成骨、成脂、成软骨能力。在三气培养箱的低氧条件(2%O_2、5%CO_2、37℃)和常规细胞培养箱的常氧条件(20%O_2、5%CO_2、37℃)下分别培养P3代细胞。通过细胞计数统计培养1d、2d、3d、4d、5d、6d、7d、8d时的细胞数量,比较不同氧浓度下细胞的生长曲线;使用Architect c8000自动生化检测仪检测培养1d、2d、3d、4d、5d时培养基的pH值和渗透压。实时荧光定量(q RT-PCR)检测不同氧浓度培养下细胞的干性基因POU家族类别5同位序列1(POU5F1,OCT4)、NANOG同位序列(NANOG)、性别决定区Y盒2(SOX2)及扩增基因细胞周期蛋白D1(Cyclin D1,CCND1)、MYC(c-Myc)、低氧诱导基因低氧诱导因子2α(HIF2α,EPAS1)、能量基因三磷酸腺苷合成酶(ATP5A1)、线粒体相关基因细胞色素c氧化酶Ⅳ亚基1型同工酶(COX4I1)、线粒体转录因子A(TFAM)、线粒体编码细胞色素c氧化酶Ⅰ(MT-CO1)、MT-CO_2的mRNA表达情况。结果:分离培养的细胞呈典型的单层贴壁生长,纺锤样;P3代细胞免疫表型鉴定显示MSCs表面分子标记高表达CD90(80.4%)、CD73(99.9%)、CD105(99.8%)、CD44(95.9%),低表达CD31(5.3%)、CD34(4.4%)、CD45(6.8%);茜素红、油红O染色、甲苯胺蓝染色证实细胞可向骨细胞、脂肪细胞、软骨细胞分化。根据国际干细胞治疗协会(ISCT)有关MSCs的判定标准,分离培养的细胞为髓核MSCs(NPMSCs)。低氧环境下培养的细胞形态更小,更接近原始MSCs,细胞增殖更快,低氧时倍增期为31.22±1.98h,常氧时倍增期为39.56±2.02h,差异有统计学意义(P0.05)。不同氧浓度各时间点培养基的pH值、渗透压差异无统计学意义(P0.05),且皆在适合细胞生存的范围。低氧培养下POU5F1(OCT4)、NANOG、SOX2、CCND1、MYC(c-Myc)、EPAS1、ATP5A1较常氧培养时显著性升高(P0.05);COX4I1、TFAM、MT-CO1、MT-CO_2较常氧培养时显著性降低(P0.05)。结论 :低氧条件下培养有利于人NPMSCs的细胞形态、干性基因、增殖能力等生物学活性的维持。     

正常与退变髓核的髓核间充质干细胞代谢活性及干性基因表达的比较

【摘要】 目的：比较来源于正常与退变髓核的髓核间充质干细胞（NPMSCs）的细胞代谢活性及干性基因表达情况。方法：收集6例非退变患者髓核组织（正常组）与6例腰椎间盘突出症患者的退变髓核组织（退变组）,采用酶消化法分离细胞,应用标准间充质干细胞培养基（standard MSC culture medium）进行细胞培养并观察细胞形态。两组内各取1例分离得到的细胞进行流式细胞仪检测间充质干细胞表面蛋白分子标记CD90、CD105、CD73、CD45、CD34及人类白细胞抗原（HLA）-DR表达情况;并进行成骨、成脂及成软骨诱导分化,诱导28d后分别应用茜素红染色鉴定细胞成骨能力、油红O染色鉴定细胞成脂能力、甲苯胺蓝染色鉴定细胞成软骨分化能力,并按照国际干细胞治疗协会（ISCT）提出的间充质干细胞的判定标准,对分离得到的细胞进行综合评估鉴定。采用CCK-8检测两组P2代NPMSCs的代谢活力。提取两组每例P2代细胞总RNA,行RT-PCR检测P2代细胞“干性维持”相关基因Oct4及Nanog表达情况。结果：两组P0代细胞均贴壁生长,形态学方面两组并无明显差异。免疫表型鉴定显示正常组和退变组间充质干细胞表面分子标记CD90、CD105、CD73表达比例分别高达96％、98％、95%以上,两组均低表达造血细胞标志物CD45、CD34、HLA-DR（均低于4%）。茜素红染色、油红O染色及甲苯胺蓝染色分别证实正常组与退变组细胞均可向骨、脂肪及软骨细胞三系诱导分化。上述结果证实分离得到的细胞即NPMSCs。细胞代谢活性测定示P2代细胞在培养后5d、7d、9d、11d、13d正常组细胞活性均强于退变组,两组细胞活性有统计学差异（P<0.05）。正常组“干性维持”相关基因Oct4及Nanog表达量分别为退变组的4.63±1.17、7.36±1.19倍,正常组均明显高于退变组（P<0.05）。结论：正常与退变髓核组织内均存在NPMSCs,但正常椎间盘来源的NPMSCs具有较强的细胞代谢活性,较”强的“干性维持”基因表达。     

酸敏感离子通道1a偶联内质网应激在人髓核细胞退变中的作用机制初探

[目的]模拟人椎间盘髓核(nucleus pulposus,NP)酸性环境,探讨酸敏感离子通道1a(acid-sensing ion channel 1a,ASIC1a)的活化与内质网应激的关系。[方法]体外单层培养人正常髓核细胞(nucleus pulposus cells,NPCs)系,不同p H值培养不同时间,模拟椎间盘酸性微环境,建立酸诱导的退变髓核细胞模型。CCK-8检测细胞增殖能力。Western blot、q PCR检测内质网应激。Western blot检测ASIC1a的表达。Fura-2/AM荧光探针检测ASIC1a活化介导的Ca2+内流。流式细胞术检测ASIC1a活化后细胞凋亡率。Pc TX1(ASIC1a特异性阻断剂)阻断ASIC1a后,观察细胞凋亡及内质网应激指标变化情况。[结果]酸诱导髓核细胞凋亡,酸激活ASIC1a及内质网应激,Pc TX1能降低促凋亡的内质网应激通路和髓核细胞凋亡率(P0.05),而未折叠蛋白反应相关指标无明显变化(P0.05)。[结论]ASIC1a能够调控内质网应激中的促凋亡通路,阻断ASIC1能够保护酸诱导的髓核细胞凋亡。     

低浓度TNF-α对大鼠髓核间充质干细胞增殖及迁移的影响

[目的]探讨低浓度TNF-α对大鼠髓核间充质干细胞(nucleus pulposus derivedstem cells,NPSCs)增殖及迁移特性的影响。[方法]差速贴壁法从SD大鼠尾椎髓核组织中分离NPSCs,体外培养,镜下观察细胞形态和生长状况;取P3代细胞利用流式细胞仪鉴定干细胞表面抗原;使用诱导培养基进行三系诱导分化,3周后分别用茜素红、油红O、阿利辛蓝染色观察成脂、成骨、成软骨能力。用含不同浓度(0、0.1、1、10 ng/ml)TNF-α的血清培养液培养P3代细胞,0、1、3、5、7 d后CCK-8法检测细胞增殖活力(OD值),划痕实验及Transwell迁移实验比较各组细胞迁移能力。[结果]P0代细胞呈集落样生长,细胞形态呈纺锤状。P3代细胞免疫表型鉴定MSCs表面分子标记CD90、CD29、CD44表达比例分别高达96%、99%、97%以上,低表达CD45、CD34(低于5%和4%)。茜素红、油红O及阿利新蓝染色证实分离的细胞可向骨、脂肪及软骨分化。按照ISCT有关MSCs的判定标准,分离的细胞即NPSCs。用含TNF-α培养液培养髓核间充质干细胞1、3、5、7 d后,与对照组相比,低浓度的TNF-α均促进了NPSCs的增殖。Transwell及划痕实验表明随着TNF-α浓度的增加,NPSCs的迁移能力上升。[结论]低浓度的TNF-α(0.1~10 ng/ml)能促进NPSCs增殖及迁移能力。     

人骨髓间充质干细胞体外分离、培养及鉴定的实验研究

目的观察体外培养人骨髓间充质干细胞(MSCs)的形态和生长规律,以证实人MSCs是一种理想的种子细胞,以及为进一步深入研究提供基础理论依据。方法对人骨髓淋巴细胞分离液采用密度梯度离心法和差异贴壁法进行分离、提纯MSCs。观察原代、传代细胞的结构、生长情况,对第2代MSCs表面抗原进行测定。结果MSCs原代培养第14～16d时细胞融合成单层,传代细胞保持原代细胞的形态特征。超微结构显示:第2代MSCs细胞核形态不规则,部分核可见多个核仁,胞质内细胞器形态分化幼稚。细胞的生长曲线显示:传代第3d起呈对数生长,第5d达到高峰,10代后无明显克隆出现。P1代克隆形成率为25.83%±2.93%,P5代为14.67%±1.63%,P10代为4.67%±0.52%。MSCs的表型特征显示细胞均一性较好,MSCs表达CD29,CD44,但不表达CD34,CD45。结论用淋巴细胞分离液密度梯度离心和贴壁筛选法,可分离、纯化人MSCs,方法简单、经济,易应用;MSCs增殖能力强,可在体外大量扩增,能满足组织工程的要求,是理想的种子细胞之一。     

人髓核间充质干细胞的分离提纯方式及生物学活性鉴定

目的 :探索人髓核间充质干细胞(nucleus pulposus mesenchymal stem cells,NPMSCs)的提纯方法并鉴定其生物学活性。方法:收集3例腰椎间盘突出症患者的退变髓核组织(Pfirrmann分级均为Ⅳ级),利用酶消化法分离细胞。采用两种方法分离提纯NPMSCs,一组细胞采用贴壁法培养(贴壁组),另一组通过流式细胞分选技术利用NPMSCs表面阳性标志物CD73、CD90、CD105获得NPMSCs(流式组)。将两种方法获得的NPMSCs进行体外培养扩增,分别进行形态学观察,细胞计数试剂盒(Cell Counting Kit,CCK-8)检测增殖能力。贴壁组NPMSCs采用流式细胞分选仪在进行分选之前检测免疫表型,流式组NPMSCs在生长达80%~90%融合时进行免疫表型的检测。向成骨、成脂、成软骨诱导分化,诱导28d后分别进行茜素红染色观察其成骨能力、油红O染色观察其成脂能力、甲苯胺蓝染色观察其成软骨能力,利用Imag J软件计算染色区域所占的面积百分比。比较两组NPMSCs在形态学、免疫表型及增殖和分化能力的差异。结果:形态学观察发现,两组NPMSCs均呈漩涡状生长,贴壁组NPMSCs可见散在的单个细胞生长;流式组NPMSCs长梭形形态更长,排列更加紧密,少见散在的单个贴壁生长细胞。流式细胞分选后所得的NPMSCs占细胞总数的(89.67±2.52)%,可以进行体外培养扩增,细胞为典型的长梭形特征,漩涡状生长,在接种后12~15d达80%~90%融合,增殖能力在接种后5~13d明显高于贴壁组NPMSCs(P0.05)。流式组NPMSCs的CD73、CD90、CD105的表达率明显高于贴壁组NPMSCs(P0.05),并且低表达CD34、CD45及HLA-DR。两种方法获得的NPMSCs均能完成三系诱导分化,流式组成骨、成脂、成软骨染色区域百分比均明显高于贴壁组(P0.05)。结论:利用流式细胞分选技术从人退变髓核组织中可获得较高纯度的NPMSCs,并能进行后续培养扩增。与贴壁法获得的NPMSCs相比,流式细胞分选的NPMSCs具有更强的增殖与分化能力。     

兔髓核间充质干细胞与髓核细胞非接触式共培养的生物学效应

[目的]通过非接触式共培养探索兔髓核间充质干细胞(NPMSCs)与兔髓核细胞(NPCs)的间接生物学效应。[方法]将第3代兔来源NPMSCs与NPCs进行非接触共培养,分设三组:NPCs/NPCs自身共培养对照组,NPMSCs/NPMSCs自身共培养对照组,NPMSCs/NPCs共培养组。分别在共培养3、5、7 d后,比较两种细胞增殖情况,ELISA检测上清液中转化生长因子β1(TGF-β1)、胰岛素样生长因子(IGF)的含量;采用RT-PCR检测共培养7 d后NPMSCs与NPCs的Col IIα1、AGG基因表达变化;免疫荧光染色检测NPMSCs中Col II的蛋白表达情况。[结果]在共培养第5 d和第7 d,共培养组NPCs的细胞数量均高于自身对照组(P0.05),在第7d,共培养组NPMSCs的细胞数量均高于自身对照组;在共培养3、5、7 d后,共培养组上清液TGF-β1、IGF的含量均高于自身对照组(P0.05);在培养7 d后,共培养组NPMSCs中Col II免疫荧光强度高于自身对照组,NPCs与NPMSCs的Col IIα1、AGG基因的表达较自身对照组显著升高(P0.05)。[结论] NPMSCs与NPCs非接触共培养可以促进细胞因子分泌、细胞增殖、基质合成与分泌。     

人碱性成纤维细胞生长因子基因转染大鼠骨髓间充质干细胞的研究

目的 观察人碱性成纤维细胞生长因子(bFGF)基因体外转染对大鼠骨髓间充质干细胞(MSCs)bFGF表达的影响.方法 密度梯度离心、贴壁法培养分离SD雄性大鼠MSCs,体外扩增,流式细胞仪检测MSCs表面抗原表达.利用慢病毒载体系统介导将具有人源性bFGF基因转染至第2代MSCs,在倒置荧光显微镜下观察转染后细胞形态和生长的变化,应用逆转录-聚合酶链反应(RT-PCR)、Western blot法鉴定bFGF在MSCs中的表达.结果 密度梯度离心、贴壁法培养分离可获得MSCs,P3代大鼠细胞利用流式细胞仪检测CD11b/c阳性细胞表达率为(13.2±0.6)%,CD34阳性细胞表达率为(1.2±0.5)%,CD44阳性细胞表达率(97.8±0.9)%,CD90阳性细胞表达率(96.8±1.4)%.MSCs转染48 h后,绿色荧光蛋白的表达明显增强.RT-PCR证实转基因MSCs表达bFGF mRNA明显增强,Western blot检测证实转基因MSCs在49 KDr出现特异性条带,而空白和空载组的MSCs则未见阳性条带.结论 采用慢病毒介导的基因转染技术可以将bFGF基因转染至MSCs中,并有外源性bFGFmRNA和蛋白的有效表达,MSCs可作为bFGF基因治疗的载体.     

大鼠骨髓间充质干细胞的生物学特性和示踪标记

目的 建立大鼠骨髓间充质干细胞(MSCs)的分离和培养方法,观察绿色荧光蛋白(GFP)基因通过慢病毒载体感染MSCs的表达.方法 采用原代贴壁法获得骨髓MSCs,观察细胞形态和生长变化,流式细胞仪鉴定细胞表面标志,体外诱导MSCs向脂肪细胞和成骨细胞分化.采用含有增强型绿色荧光蛋白(EGFP)基因慢病毒载体感染培养的MSCs,比较细胞感染前后生物学特性.结果 原代贴壁筛选结合差异传代培养的MSCs表面标志阳性率分别为CD44 94.81%,CD90 99.53%,CD106 76.34%,MSCs在pH值稳定于7.2～7.4的环境可传20代.体外MSCs诱导分化后特异性染色显示脂质沉淀和骨结节,表达脂肪细胞和成骨细胞特异基因.慢病毒载体可有效感染大鼠MSCs,加入聚凝胺感染效率达到80%,EGFP在MSCs感染后1个月仍持续表达.结论 骨髓MSCs可长期培养,具有良好的多向分化能力.携带EGFP基因慢病毒载体能高效感染MSCs,EGFP可作为MSCs体内研究的示踪标记.     

Vasopressor hormone response following mesenteric traction during major abdominal surgery

Background : We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI₂) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia. Methods : In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGFlα (stabile metabolite of PGI₂), TXB₂ (stabile metabolite of thromboxane A₂) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection. Results : Following MT, arterial hypotension occurred along with a substantial PGI₂ release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF_1α (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P=0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB² (164 (87) vs. 58 (1) ng/L, P=0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P=0.001), AVP (41 ± (18) vs. 12 (7) ng/L, P=0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients. Conclusion : Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI₂ release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A₂, presumably contributing to hemodynamic stability within 30 min after MT.     

A Teaspoon Pump for Pumping Blood with High Hydraulic Efficiency and Low Hemolysis Potential

Abstract: Virtually all blood pumps contain some kind of rubbing, sliding, closely moving machinery surfaces that are exposed to the blood being pumped. These valves, internal bearings, magnetic bearing position sensors, and shaft seals cause most of the problems with blood pumps. The original teaspoon pump design prevented the rubbing, sliding machinery surfaces from contacting the blood. However, the hydraulic efficiency was low because the blood was able to "slip around" the rotating impeller so that the blood itself never rotated fast enough to develop adequate pressure. An improved teaspoon blood pump has been designed and tested and has shown acceptable hydraulic performance and low hemolysis potential. The new pump uses a nonrotating "swinging" hose as the pump impeller. The fluid enters the pump through the center of the swinging hose; therefore, there can be no fluid slip between the revolving blood and the revolving impeller. The new pump uses an impeller that is comparable to a flexible garden hose. If the free end of the hose were swung around in a circle like half of a jump rope, the fluid inside the hose would rotate and develop pressure even though the hose impeller itself did not "rotate"; therefore, no rotating shaft seal or internal bearings are required.     

Microspheres Based Detoxification System: A New Method in Convective Blood Purification

Abstract: A variety of protein-bound or hydrophobic substances, accumulating as a result of pathologic conditions such as exogenous or endogenous intoxications, are removed poorly by conventional detoxification methods because of low accessibility (hemodialysis), insufficient adsorption capabilities (hemosorption), low efficiency (peritoneal dialysis), or economic limitations (high-volume plasmapheresis). Combining advantages of existing methods with microspheric technology, a module-based system was designed. Major operating parameters of the latter can be modified to allow for adjustment to individual clinical situations. An extracorporeal blood circuit including a plasmafilter is combined with a secondary high-velocity plasma circuit driven by a centrifugal pump. Different microspheric adsorbers can be combined in one circuit or applied in sequence. Thus, a prolonged treatment can be tailored using specially designed selective adsorber materials. Comparing this system with existing methods (high-flux hemodialysis, molecular adsorbent recycling system), results from our in vitro studies and animal experiments demonstrate the superior efficiency of substance removal.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts

Background : Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far.
Methods : Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined.
Results : At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1±1.2% (mean±SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2±1.2%), sevoflurane (to 4.4±0.9%) or halothane (to 3.2±1.5%) (each P <0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics.
Conclusion : Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.     

Bariatric Surgery in Some "Central and East-European (former Eastern bloc)"Countries - Current Status and Prediction for the Next Millennium

Background: Obesity is increasing globallly, including in the formerly "Eastern Bloc" countries. Methods: A survey was made of obesity and bariatric surgery. Results: In the 8 East and Central European countries studied, with total population 300 million, roughly 43% of the population was overweight (BMI 25-30), 23% obese (BMI > 30), with about 15 million people morbidly obese (BMI > 40). From 0-10 morbidly obese individuals/100,000/year undergo bariatric surgery. Conclusion: Most countries were found to provide inadequate treatment for obesity.The majority of the morbidly obese are not treated effectively. However, health-care awareness of obesity and bariatric surgeons are slowly increasing.     

Is the recovery profile of mivacurium independent of the rate of decay of its plasma concentration in patients with normal plasma cholinesterase activity?

Background: The duration of action of muscle relaxants is poorly correlated to the rate of decay of their plasma concentration. The plasma concentration of mivacurium may rapidly decrease below its active concentration because of the extensive hydrolysis of mivacurium. By inflating a tourniquet on one upper limb for 3 min after the administration of atracurium, mivacurium or vecuronium, we studied the influence of the initial decline of their plasma concentration on their effect. Methods: In 50 patients anaesthetised with thiopental, isoflurane and fentanyl, the effect of bolus doses of 0.15 or 0.25 mg . kg^?1 mivacurium (MIV 15, MIV 25), 0.3 or 0.5 mg . kg^?1 atracurium (ATR 30, ATR 50) and 0.06 or 0.1 mg . kg^?1 vecuronium (VEC 06, VEC 10) were measured on both arms (evoked response of the adductor pollicis to train-of-four stimulation every 12 s), a tourniquet being applied on one arm just before and during 3 min after the muscle relaxant bolus. Results: Tourniquet inflation of 3 min almost abolished the neuromuscular effect of mivacurium. In the vecuronium groups and in the ATR 50 group, tourniquet inflation did not modify the maximum degree of depression of the twitch response. Also, the duration of action of vecuronium was unaffected by the tourniquet. In the ATR 30 group, times to return of the twitch response to 25% (duration 25%) and 75% (duration 75%) of control response were significantly shorter in the cuffed arm, 23 min vs 27 min, and 41 min vs 45 min, respectively. In the ATR 50 group, only duration 25% was significantly shorter in the cuffed arm (41 min vs 45 min). Conclusion: The results suggest that the rate of decline of the plasma concentration of mivacurium is so rapid, that a very low and almost clinically ineffective concentration is present as soon as 3 min after its administration. The results also indicate that the recovery from a mivacurium-induced neuromuscular blockade is not influenced by the rate of decay of its plasma concentration in patients with genotypically normal plasma cholinesterase.     

Membranes in Artificial Organs

Abstract: Membrane processes play a pivotal and enabling role in modern replacement therapy for acute and chronic organ failure and in the management of immunologic diseases. In fact, virtually all contemporary extracorporeal blood purification methods employ membrane devices, and the next generation of artificial organs and tissue engineering therapies are almost certain to be similarly grounded in membrane technology. In this short essay, we comment on the similarities and differences among synthetic membranes and their natural counterparts and also provide a critical overview of the demographics and technology of hemodialysis, hemofiltration, apheresis, oxygenation, and emerging membrane technologies and applications.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.     

Synergistic interaction between the effects of propofol and midazolam with fentanyl on phrenic nerve activity in rabbits

Background: It has been shown that the depressive effects of both propofol and midazolam on consciousness are synergistic with opioids, but the nature of their interactions on other physiological systems, e. g. respiration, has not been fully investigated. The present study examined the effect of propofol and midazolam alone and in combination with fentanyl on phrenic nerve activity (PNA) and whether such interactions are additive or synergistic. Methods: PNA was recorded in 27 anaesthetised and artificially ventilated rabbits. In three groups, propofol, fentanyl and midazolam were administered intravenously in incremental doses to construct dose-response curves for the depressant effects of each one on PNA. In another two groups, the effect of pretreatment with either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. on the effects of propofol and fentanyl respectively on PNA were studied. Results: Propofol and fentanyl caused a dose-dependent depression of PNA with complete abolition at the highest total doses of 16 mg · kg^?1 i. v. and 32 μg · kg^?1 i. v., respectively. In contrast, midazolam in incremental doses to a total of 0.8 mg · kg^?1 reduced mean PNA by 63%, but approximately 12% of PNA remained at a total dose as high as 6.4 mg · kg^?1. The mean ED₅₀s, calculated from dose-response curves, were 5.4 mg · kg^?1, 3.9 μg · kg^?1 and 0.4 mg · kg^?1 for propofol, fentanyl and midazolam, respectively. Initial doses of either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. acted synergistically with subsequent doses of either propofol or fentanyl to abolish PNA at total doses of 8 mg · kg^?1 and 8 μg · kg^?1, respectively. Conclusion: Fentanyl has a synergistic interaction with both propofol and midazolam on PNA and hence potentially on respiration.