催产素及其受体调节骨代谢研究

催产素（oxytocin, OT）除具有调节分娩和母乳分泌的作用外，外周性OT和催产素受体（oxytocin receptor, OTR），非中枢性，对骨骼也有直接的调节作用。骨髓间充质干细胞、成骨细胞（osteoblast，OB）、破骨细胞（osteoclast，OC）、骨细胞、软骨细胞、脂肪细胞均表达OT及OTR。OB在雌激素的刺激下，合成OT，并成为骨形成的旁分泌-自分泌调节剂。在雌激素的介导之下，OT/OTR与OB形成前馈环路。骨保护素(osteoclastogenesis inhibitory factor, OPG)/核因子κB受体活化因子配体（receptor activator of nuclear factor-κB ligand, RANKL）信号通路是OT及OTR发挥抗骨质疏松（osteoporosis, OP）作用的关键通路。OT通过上调骨形成蛋白，下调骨吸收标志物水平，进而提高骨髓间充质干细胞活性，促进其向OB方向而非脂肪细胞方向分化。OT通过促进OTR易位到OB的细胞核中，诱导OB的矿化。OT通过触发胞浆内Ca2+释放和一氧化氮的合成，调节OB中OPG/RANKL的比例，对破骨细胞具有双向的调节作用。此外，OT同样能够提高骨细胞和软骨细胞的活性，并在提高骨量，改善骨显微结构方面具有重要的作用。基于OT和OTR具有抗OP的良好作用，本文对近年来OT及OTR调节骨代谢的研究进行综述，以期为其临床应用与研究提供参考。     

TLR4/NF-κB通路与骨质疏松症关系的研究进展

骨质疏松症(osteoporosis, OP)是一种普遍存在的与年龄相关的骨骼疾病，雌激素缺乏和衰老是主要病因，近年来越来越多的研究表明炎症反应在OP的发生发展过程中发挥重要作用。Toll样受体4(toll like receptor 4,TLR4)是Toll样受体家族的主要成员，是内毒素最重要的模式识别受体。TLR4是经典的炎症信号转导通路，当TLR4信号通路激活，与核因子κB (nuclear factorκB,NF-κB)转移到细胞核并释放炎性细胞因子(TNF-α、IL-1β、IL-6等),并抑制骨髓间充质干细胞成骨分化及钙盐沉积，促进破骨细胞成熟，最终导致OP。对TLR4信号通路与OP关系的研究不仅可以从炎症角度深入揭示OP的发病机制，还可以为OP的防治提供新的思路。     

RANK信号调控破骨细胞分化与成熟的研究进展

破骨细胞来源于微环境造血前体细胞,它的生存、增殖、分化和激活需要巨噬细胞集落刺激因子(M-CSF)和核因子κB受体活化因子配体(RANKL)参与。RANKL与相应的RANK受体结合,从而刺激破骨前体细胞分化成为破骨细胞。这一过程由不同的调节蛋白和激酶来调控,并且依赖于RANKL-RANK信号。本文中,笔者总结了目前已知的在破骨细胞发生过程中调节RANK信号的机制。在早期阶段,RANK信号的调节通过募集调节蛋白如肿瘤坏死因子受体相关因子6(tumor necrosis factor receptor-associated factor 6, TRAF6),引起丝裂原活化蛋白激酶(mitogen-activated protein kinases, MAPKs)以及转录因子核因子κB(nuclear factor-κB, NF-κB)和激活蛋白-1(activator protein-1, AP-1)的活化。活化的NF-κB进一步激活调节破骨细胞生成的重要因子-T细胞核因子1(nuclear factor of activated T-cells cytoplasmic 1, NFATc1)。在信号传递的中间阶段,共刺激信号通过激活磷脂酶Cγ2(phospholipase Cγ2, PLCγ2)连同c-Fos/AP-1引起钙离子(Ca~(2+))振荡,同时Ca~(2+)信号促进NFATc1的产生。在破骨细胞生成的晚期阶段,NFATc1入核诱导大量的破骨细胞特异性靶基因的表达,从而使细胞融合并发挥其功能。     

脉冲电磁场对骨代谢的分子细胞学作用机制研究进展

脉冲电磁场(pulsed electromagnetic fields,PEMFs)作为一种无创、安全、有效的物理治疗手段,在临床上常用于促进骨折愈合和治疗骨质疏松症(osteoporosis,OP).虽然PEMFs能刺激成骨细胞(osteoblast,OB)生成、抑制破骨细胞(osteoclast,OC)生成并影响骨...     

血液透析患者骨密度与骨保护素和核因子κB受体 活化因子配体的关系

核因子κB受体活化因子配体(RANKL)是近年来在肿瘤坏死因子配体超家族中发现的一种具有调控破骨细胞产生和活化作用的细胞因子[1].它与骨保护素(OPG)、核因子κB受体活化因子(RANK)的相互作用,能调节破骨细胞的活化和增殖,维持正常骨重建过程.     

破骨细胞介导炎症性骨丢失的研究进展

破骨细胞起源于骨髓的多潜能干细胞,破骨细胞的数量和功能决定了关节破坏与骨丢失的严重程度,而炎症本身并不介导关节破坏和骨丢失。炎症性关节的滑膜成纤维细胞产生大量的炎症因子,如肿瘤坏死因子-α(TNF-α)和白介素-1(IL-1)。这些炎症因子不仅诱发炎症反应,而且通过促进核因子κB受体激活子配体,间接或直接增加破骨细胞的生成,并促进其功能,从而将炎症反应与局部骨丢失及损坏联系在一起。本文综述了近年来关于TNF-α、IL-1及破骨细胞靶疗法在破骨细胞介导的炎症性骨丢失过程中的研究进展。TNF-α通过促进外周血破骨细胞前体细胞的分化直接影响关节局部成熟破骨细胞的最终数目,而IL-1主要通过延长成骨细胞的寿命及调控破骨细胞骨架的重组来增加其骨吸收能力。抑制破骨细胞生长及功能的破骨细胞靶疗法在治疗炎症性骨丢失和关节损伤等方面日益得到重视。     

破骨细胞分化机制的研究进展

破骨细胞为人体主要的骨吸收细胞,对骨骼的发育及维持具有重要作用,同时破骨细胞的异常活化对多种溶骨性疾病的发展具有重要作用;明确破骨细胞的分化机制,可为多种骨代谢性疾病提供新的治疗策略及药物靶点。大量的实验对破骨细胞的分化机制进行了研究,并确认有一些基因为破骨细胞分化形成所必需,这些基因的缺失或突变将导致破骨细胞形成障碍,进而引起骨质硬化;并且由巨睡细胞集落刺激因子（macrophage colony stimulating factor,M-CSF)、核因子k B受体活化因子 配体（receptor Activator for Nuclear Factor-k B Ligand, RANKL)及免疫受体酪氨酸激活基序（immunoreceptor tyrosine-based activation motif,ITAM)介导的3条重要的信号通路参与其分化过程,3条信号通路相互作用,共同促进破骨细胞的分化形成,但RANKL如何激活ITAM信号通路,有待进一步研究,本文就破骨细胞分化机制的研究进展作一综述。     

纯化前后C57BL/6小鼠骨髓细胞诱导破骨细胞的方法研究

目的研究纯化前后C57BL/6小鼠骨髓细胞向破骨细胞体外诱导条件,总结利用原代细胞诱导破骨细胞技巧。方法将纯化前后的原代细胞按不同密度接种(ρ=5×10~5 cells/cm~2及ρ=2.5×10~5 cells/cm~2),并在不同时机加入诱导因子,观察各组中抗酒石酸酸性磷酸酶(tartrate-resistant acid phosphatase,TRAP)染色阳性细胞数以及破骨细胞标志性基因的表达水平。结果未纯化原代骨髓细胞用低密度接种(2.5×10~5 cells/cm~2)时,无法诱导出破骨细胞;加大接种密度(5×10~5 cells/cm~2)后,利用巨噬细胞集落刺激因子(macrophage colony-stimulating factor,M-CSF)与NF-κB受体激活蛋白配体(receptor activator of NF-κB ligand,RANKL)共刺激可诱导出破骨细胞。纯化后原代细胞用低密度(2.5×10~5 cells/cm~2)接种,利用M-CSF预处理或与RANKL共刺激这两种诱导方法均能诱导出破骨细胞,且预处理法诱导效果更佳。结论利用原代骨髓细胞诱导破骨细胞,当其中单核细胞比例较低时,应优先考虑加大细胞接种密度,并尽早加入RANKL,促进单核细胞向破骨细胞分化。     

骨保护蛋白及配体与破骨细胞

破骨细胞对骨量的维持起重要作用,它的发育、成熟信号是由成骨细胞传递的。当受到骨吸收因子作用时,成骨细胞表达骨保护蛋白配体分子,与破骨前体细胞膜上的核因子κB受体激活子结合,使之分化、成熟为破骨细胞。而成骨细胞旁分泌的骨保护蛋白分子,则作为伪受体与核因子κB受体激活子竞争结合骨保护蛋白配体,从而抑制破骨细胞的生成。骨保护蛋白配体-核因子κB受体激活子-骨保护蛋白组成了破骨细胞分化的信号传导通路,对它的认识有助于临床治疗代谢性骨病。     

肿瘤坏死因子-α调控骨质疏松症作用机制研究

成骨细胞(osteoblast, OB)与破骨细胞(osteoclast, OC)动态平衡调控着骨重塑稳态,其平衡被打破将介导系列骨疾病发生与发展,如骨质疏松症(osteoporosis, OP)、类风湿关节炎(RA)和骨硬化症等。肿瘤坏死因子-α(tumor necrosis factor α,TNF-α)是一种由活化的巨噬细胞/单核细胞产生的炎性细胞因子,是骨吸收增强剂和骨形成抑制剂,可调控骨髓间充质干细胞(bone mesenchymal stemcells, BMSCs)、OB和OC相关信号通路、蛋白及基因表达而减弱BMSCs成骨分化、抑制OB矿化和促进OC活化、增殖与成熟,导致骨形成和吸收之间动态失衡扰乱骨重建而促进OP的进展。因此,笔者通过查阅国内外相关文献资料总结TNF-α在OP中的相关作用机制以期为进一步临床研究提供一定理论依据。     

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.     

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.     

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.     

Dilemma of Membrane Biocompatibility and Reuse

Abstract: Numerous articles have been published on the multiple use of dialyzers and on the effect of different reprocessing chemicals and techniques on the dialyzer biocompatibility and performance. The results often appear contradictory, especially those comparing standard biocompatibility parameters. Despite this confusion, a discerning review of the published works allows certain limited conclusions to be drawn. Reprocessing of used hemodialyzers changes the biocompatibility profile of a dialyzer as defined by the parameters complement activation. leukopenia, and cytokine release. The effect of reprocessing depends on the chemicals and reprocessing technique applied and also on the type of membrane polymer being subjected to the reprocessing procedure. Reports of pyrogenic reactions indicate that the flux of the membrane also influences how suitable it is for safe reuse. An increased risk of allergic and pyrogenic reactions appears to be associated with dialyzer reuse. Furthermore, there has been a lack of investigations into the immunologic effect of the layer of adsorbed and chemically altered proteins that remains on the inner surface of reprocessed dialyzers. We conclude that the clinical benefit of dialyzer reuse cannot be generally accepted from a biocompatibility point of view.