明胶/姜黄素纳米纤维电纺膜皮下环境构建组织工程软骨的可行性研究

目的探讨以明胶/姜黄素电纺材料为支架,在动物皮下构建组织工程化软骨的可行性。方法取兔耳软骨获取软骨细胞作为种子细胞,体外培养扩增,并以明胶电纺膜(对照组)和明胶/姜黄素电纺膜(实验组)为支架构建软骨。将支架材料植入BALB/c裸鼠背部皮下后行大体观察;对支架材料及细胞-支架复合物行电镜观察;对细胞-支架复合物进行细胞增殖率检测;另将体外培养1周的细胞-支架复合物植入BALB/c裸鼠背部皮下,3周、12周后行组织学检测,比较不同时间点的软骨形成情况。结果大体观察显示,相比对照组,实验组材料周围组织血管化受到明显抑制;SEM结果显示,两组材料中细胞均黏附良好;细胞增殖率检测结果显示,姜黄素对细胞增殖无显著影响;组织学观察显示,3周、12周时,两组细胞-支架复合物均有软骨陷窝形成;但相比对照组,实验组材料可见明显吸收,软骨基质形成较厚,均质性更佳。结论明胶/姜黄素材料可作为支架在裸鼠皮下构建组织工程化软骨,具有潜在的应用前景。     

壳聚糖/Ⅰ型胶原复合支架与滑膜成纤维样细胞构建颞下颌关节盘的研究

目的 探讨利用滑膜成纤维样细胞(SFBs)及壳聚糖/Ⅰ型胶原(CS/COL-Ⅰ)复合支架构建颞下颌关节盘软骨的可行性.方法 获取兔颞下颌关节滑膜组织进行SFBs培养,第3～5代SFBs三维培养于通过冷冻干燥法制备的CS/COL-Ⅰ支架材料中7 d,用噻唑蓝(MTT)比色法分别在1、3、5、7 d检测支架材料对细胞增殖的影响.细胞支架复合物在体外经过人重组转化生长因子β1(rhTGF,10μg/L)和碱性成纤维细胞生长因子(bFGF,50 μg/L)诱导后,植入裸鼠体内4、8周后获取标本,进行组织学检测细胞在支架材料上的生长状态及黏多糖(GAGs)形成,免疫组织化学和逆转录-聚合酶链反应(RT-PCR)半定量分析Ⅱ型胶原的表达.结果 支架材料表面及内部均呈多孔隙蜂窝状结构.SFBs在CS/COL-Ⅰ中的增殖要明显高于平板培养(P＜0.05).细胞支架复合物植入裸鼠体内4、8周后,组织学及免疫组织化学半定量分析显示在8周时GAGs(6.900±0.316)和Ⅱ型胶原(0.0952±0.0248)IA/μm2与4周时GAGs(3.600±0.699)和Ⅱ型胶原(0.0411±0.0127)IA/μm2差异有统计学意义(P＜0.05).结论 体外诱导后的SFBs/CS-COL-Ⅰ复合物具有应用于组织工程化颞下颌关节盘构建的可能.     

软骨细胞与成纤维细胞共培养体外构建软骨的初步研究

目的 软骨微环境对软骨形成具有重要作用.本实验探讨软骨细胞与成纤维细胞共培养体外构建软骨的可行性.方法 分别培养猪软骨细胞与人成纤维细胞,将两种细胞按3:7(软骨细胞:成纤维细胞)比例混匀,以5.0×107/ml终浓度接种于聚羟基乙酸支架(PGA,直径9mm,高2mm)作为共培养组,相同终浓度单纯软骨细胞和单纯成纤维细胞分别接种于相同支架作为阳性对照及阴性对照.每组各接种3例标本,每例接种细胞悬液200μl.全部标本均体外培养12周后取材,通过大体观察、组织学及免疫组化等检测对构建软骨进行评价.结果 各组细胞均与材料支架粘附良好.体外培养12周后,阳性对照组(软骨细胞组)及共培养组均形成成熟的软骨样组织,组织学及免疫组化显示有成熟的软骨陷窝样结构及Ⅱ型胶原表达.软骨细胞组在体外培养过程中能基本保持复合物初始的大小和形状,形成的软骨在组织学上也教为均匀一致.共培养组在培养过程中稍有缩小,在复合物的周边区域形成了均质的软骨样组织,但在近中心区域存在一定量的纤维性组织.阴性对照组(单纯成纤维细胞组)在体外培养过程中逐渐皱缩变形,未形成软骨样组织.结论 软骨微环境在体外软骨分化及软骨形成中具有重要作用,软骨细胞与成纤维细胞体外共培养能形成软骨样组织.     

软骨细胞接种小孔径聚乳酸-羟基乙酸共聚物支架的方法选择

目的 探讨软骨细胞接种小孔径聚乳酸-羟基乙酸共聚物(PLGA)支架的最佳接种方法. 方法 实验分3组(n=9):注射组、负压组、振荡组,取纤维蛋白原溶液混悬第2代软骨细胞,采用上述3种方法对孔隙率为92％、孔径为50 ～ 100 μm的PLGA支架进行细胞接种.48 h后,Hoechst33258法检测支架内DNA含量;接种并观察支架内含异硫氰酸荧光素的无细胞纤维蛋白原凝胶的分布;硬组织切片、4’,6-二脒基-2-苯基吲哚(DAPI)染色观察支架内细胞分布.7d后,扫描电镜观察支架表面及内部的细胞形态.各组部分支架(n=3)植入裸鼠皮下,以无细胞PLGA支架为空白对照组,术后8周取出支架行甲苯胺蓝、Ⅱ型胶原免疫组织化学染色,并计算累积吸光度(IOD)值. 结果 注射组、负压组、振荡组平均DNA含量分别为(755.79±80.50)、(657.32±89.68)、(650.18±106.33)ng/mg,各组比较差异均无统计学意义(F=1.214,P=0.361).无细胞纤维蛋白凝胶在各组中都均匀分布,DAPI染色显示注射组细胞分布较其他两组均匀.扫描电镜显示负压组和振荡组外周细胞较注射组多,而支架孔隙内仅注射组可见细胞黏附.注射组甲苯胺蓝、Ⅱ型胶原免疫组织化学染色的IOD值均优于其他3组,差异有统计学意义(P＜0.05). 结论 对于50 ～ 100 μm的小孑L径PLGA支架,注射法是一种快捷、高效的细胞接种方法.     

非降解聚氨酯弹性体支架材料体外构建残耳软骨用于修复耳廓组织的可行性

目的:探讨以非降解聚氨酯弹性体支架材料体外构建残耳软骨用于修复耳廓组织的可行性。方法:分离30例临床小儿畸形患者软骨细胞,经培养、扩增后制成细胞悬液滴加于圆盘状聚氨酯支架上,体外培养21d后接种于裸鼠体内培养42d,应用扫描电镜观察细胞-支架复合物生长情况,同时使用免疫组织化学法观察成软骨细胞冰冻切片情况。结果:软骨细胞体外培养3周后形成的细胞-支架复合物的形态学及组织学较正常耳廓软骨组织相差甚远,而在裸鼠体内培养6周的细胞-支架复合物外观光滑细腻,与正常耳廓软骨组织相近,经免疫组织化学法分析可见新生的软骨组织细胞间质中存在蓝黑色的丝网状弹力纤维。结论:聚氨酯材料能够成为组织工程耳廓软骨的支架材料,且体内培养较体外培养更利于软骨组织的生长。     

应用婴幼儿骨髓间充质干细胞体外构建组织工程化心肌

目的探讨以先天性心脏病(congenital heart disease,CHD)婴幼儿骨髓间充质干细胞(bone mesenchymal stem cells,BMSCs)作为种子细胞于体外构建组织工程化心肌组织的可行性。方法分离培养CHD婴幼儿胸骨BMSCs,经5-氮杂胞苷诱导分化为心肌细胞,种植到可降解的载体——聚乳酸/羟基乙酸的共聚物(polyactic acid/glycolic acid homoconjugate,PLGA)上,加入含有10%胎牛血清的LG-DMEM培养液,摇床培养1周后种植到裸鼠背部皮下,分别在种植后1、2、3周处死裸鼠。实验终止后通过光学显微镜、常规HE染色、蛋白质印记(Western Blotting)和透射电镜观察等对构建的组织工程化心肌组织进行评价。结果骨髓间充质干细胞经定向诱导分化后与PLGA构建的细胞-支架复合体培养1周后可见大部分细胞存活,有大量的细胞外基质分泌,植入裸鼠体内后3周取出标本大体观察可见组织样结构形成,Western blot检测结果表明构建的心肌组织有心房利钠肽(ANP)和心肌特异性肌球蛋白重链(MHC)的表达,透射电镜下可见体外构建的工程化心肌具有肌丝,缝隙连接和闰盘样结构形成。结论以CHD要幼儿BMSCs为种子细胞,PLGA为支架构建组织工程化心肌可行,构建的组织工程化心肌具有自体心肌的特性。     

组织工程骨软骨复合物的构建与形态学观察

目的探讨采用组织工程技术构建骨软骨复合物的可行性。方法将骨髓基质细胞(BMSCs)成诱导软骨后接种于快速成形的三维支架材料聚乳酸／聚羟乙酸共聚物(PLGA)构建组织工程软骨，经成骨诱导的BMSCs接种于聚乳酸／聚羟乙酸共聚物／磷酸三钙(PLGA／TCP)构建组织工程骨，在体外分别培养2周后，将两种工程化组织及两者以无损伤线缝合形成的组织工程骨软复合体分别植入自体股部肌袋，术后8周取材，行组织学观察。结果术后组织学观察表明。组织工程软骨在体内可形成软骨组织组织工程骨在体内可形成骨组织，两者的复合体在体内可形成骨软骨复合物。结论以骨髓基质细胞为种子细胞、以快速成形的生物降解材料为支架体外构建的组织工程骨软骨复合物，可在体内形成骨软骨组织，有望用于骨软骨缺损的修复。     

基于细胞外基质来源的组织工程椎间盘双相支架裸鼠皮下异位构建椎间盘

[目的]探讨椎间盘细胞和细胞外基质来源的一体化纤维环-髓核双相支架在裸鼠体内异位构建组织工程一体化椎间盘的可行性,并采用PKH26荧光标记和小动物活体荧光成像系统无创评估组织工程化细胞-支架复合体在体内生长情况。[方法]纤维环细胞和髓核细胞分别标记PKH26荧光,分别接种入细胞外基质来源的一体化支架不同相中,扫描电镜、Dead/Live荧光染色观察细胞粘附及活性,植入裸鼠背部皮下,6周后利用分子小动物活体荧光成像系统评价组织工程化组织在裸鼠体内生长情况,取材进行荧光显微镜下观察、组织学染色。[结果]扫描电镜观察细胞粘附在双相支架上且周围有基质分泌,Dead/Live染色示细胞在双相支架上活性良好;6周后,活体荧光成像显示椎间盘细胞在支架内生长良好,从髓核往纤维环荧光强度减弱,细胞支架复合体在裸鼠体内形成椎间盘样组织,HE、番红O染色、甲苯胺蓝染色阳性。[结论]天然骨基质明胶和软骨基质来源的一体化纤维环-髓核支架复合椎间盘细胞能够在裸鼠皮下异位构建椎间盘样组织。     

胶原凝胶包埋软骨细胞接种CPPf/PLLA支架体外构建组织工程软骨

目的:探讨软骨细胞均匀、高效种植于三维支架的细胞接种方法.方法:将胶原凝胶包埋的软骨细胞整合入CPPf/PLLA三维支架并进行体外培养,细胞计数检测细胞粘附情况,倒置显微镜观察细胞在支架内分布的均一性,组织形态学检测细胞-胶原凝胶-支架复合物形成软骨组织的情况.结果:超过90%的种植细胞能有效、均匀种植于CPPf/PLLA支架,体外培养3周的复合物能形成较成熟的工程化软骨组织.结论:胶原凝胶包埋软骨细胞三维接种能有效提高组织工程软骨的体外构建质量,同时结合了两种材料的优势.     

组织工程化椎间盘构建及其生物学评定

目的 探讨人骨髓间充质干细胞(BM-MSCs)经诱导转化为人髓核细胞(NPs)并构建组织工程椎间盘的价值.方法 体外培养胎儿NPs及BM-MSCs并种植在聚乳酸-聚羟基乙酸共聚物(PLGA)支架上,倒置显微镜及扫描电镜进行形态学观察.将载有BM-MSCs和NPs的PLGA支架及BM-MSCs和NPs的细胞悬液植入新西兰大白兔椎间盘中,12周后对椎间盘信号强度按Thompson分级进行评定.分光光度法检测蛋白聚糖并免疫组化检测Ⅱ型胶原的表达.结果 BM-MSCs在与NPs共培养后由梭形、多角形变为成纤维细胞样,且两种细胞在PLGA支架表面贴附,形态正常,生长良好;载有BM-MSCs和NPs的PLGA支架在椎间MRI信号维持、蛋白多糖[PLGA支架组含量为(3.93±0.31)mg/100 mg,对照组为(3.52±0.26)mg/100 mg]及Ⅱ型胶原表达上较对照组差异均有统计学意义(P＜0.05).结论 共培养可促使BM-MSCs向NPs转化,PLGA支架为细胞提供良好的生长环境,其力学性能维持和空间结构保障可以满足BM-MSCs与NPs构建组织工程椎间盘的需要,有效延缓了椎间盘的退变.

Abstract：

Objective To investigate the value of bone marrow-mesenchymal stem cells(BMMSCs)transformed by nucleus pulposus(NPs)for construction of tissue engineering disc.Methods BMMSCs and fetal NPs were cultured in vitro,planted on polylactic acid-polyglycolic acid copolymer(PLGA),and observed with inverted microscope and scanning electronic microscope.PLGA scaffolds with adherent BM-MSCs and NPs,as well as BM-MSCs and NPs suspension were implanted into intervertebral discs of New Zealand white rabbits,respectively.Intervertebral signal intensity was evaluated by Thompson grading 12 weeks later.Proteoglycan and type Ⅱ collagen were determined by spectrophotometric method and immunohistochemistry,respectively.Results Spindle or multi-angular BM-MSCs turned into fibro-like phenotype coculture of BM-MSCs and NPs,which grew well with normal morphology when they attached on PLGA scaffolds.There was statistical difference in intervertebral signal intensity,and the expression of proteoglycan and type Ⅱ collagen between PLGA scaffolds group and control group(P＜0.05),the content of proteoglycan was(3.93 ± 0.31)mg/100 mg in the PLGA scaffolds group whereas(3.52 ± 0.26)mg/100 mg in the control group.Conclusions BM-MSCs can be induced into NPs by cocultivation,and PLGA scaffolds can provide good growing conditions,and maintain high mechanical properties and spacial structure which meet the requirement of tissue engineering disc to prevent degeneration.     

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 comparison of the inhibitory effects of four volatile anaesthetics on the metabolism of chlorzoxazone, a substrate for CYP2E1, in rabbits

Background: Halothane inhibits in vitro and in vivo activity of cytochrome P-450 (CYP) 2E1. There are several fluorinated volatile anaesthetics besides halothane, and most of them are defluorinated by CYP2E1. It is unclear whether other fluorinated anaesthetics inhibit the in vivo activity of CYP2E1.
Methods: We compared the inhibitory effects of therapeutic concentrations of four inhalational anaesthetics, halothane, enflurane, isoflurane, and sevoflurane, on chlorzoxazone metabolism in rabbits receiving artificial ventilation.
Results: All four inhalational anaesthetics decreased arterial blood pressure and increased plasma chlorzoxazone concentration. However, no significant differences in the plasma chlorzoxazone concentration were found between the four anaesthetics. The estimated chlorzoxazone clearance increased after beginning inhalation with all four agents, but no significant difference in clearance was noted between agents.
Conclusions: At therapeutic concentrations, the in vivo inhibitory effect on chlorzoxazone metabolism was similar for all four inhalational anaesthetics examined, even though their chemical characteristics and extent of hepatic metabolism differ considerably.     

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.     

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.