固定化脂肪酶催化大豆油制备生物柴油

研究了脂肪酶固定化及其催化大豆油制备生物柴油的工艺。采用溶胶-凝胶法对脂肪酶进行了固定化,考察了固定化酶催化大豆油转酯化的生产工艺中酶用量、醇油比、含水量、反应温度、反应时间、溶剂等参数对转酯过程的影响。实验结果表明,当大豆油4.5 g时,最佳的反应条件为：固定化酶646 mg,醇油摩尔比4∶1,含水质量分数为6%,40℃,甲酯的最终转化率为96.33%。     

微乳凝胶固定化酶催化长链脂肪酸酯的合成

研究了以AOT(二 (2 乙基已基 )琥珀酸酯磺酸钠 ) /正庚烷 /水 /明胶组成的反相微乳凝胶固定化脂肪酶 ,在有机溶剂中催化棕榈酸和十六醇的酯化反应 .反应在 2 5℃下进行 ,固定化脂肪酶重复使用 16次后 ,平衡转化率仍可达 90 % .反应既可用釜式反应器又适用柱式反应器 .产物通过冷却的反应液后沉淀析出 ,回收率可达 6 5% ,产品纯度高 .     

有机相酶促合成N-月桂酰-β-氨基丙腈

以月桂酸甲酯和β－氨基丙腈为原料，在有机相中经脂肪酶催化合成N－月桂酰-β-氨基丙腈（LAP）。在比较所用脂肪酶的催化活性的基础上，详细探讨了固定化脂肪酶Candida antarctica（南极洲假丝酵母）CAL－2催化该反应的影响因素。经筛选，适宜的反应条件为：70℃，n（β－氨基丙腈）：n（月桂酸甲酯）＝1：1，底物质量浓度为35g/L，加酶量为200U/g(以氨基丙腈的质量计），反应体系初始加水量为3％腈重。在此实验条件下反应24h后，β－氨基丙腈的最高转化率为96.8%。     

脂肪酶固定化工艺

研究了以纸纤维素为载体,对－β－硫酸酯乙砜基苯胺（ＳＥＳＡ）为活化剂共价偶联法固定化脂肪酶的最适条件及固定化酶的稳定性。结果表明：醚化反应最适ｐＨ为１０．０,偶联最适条件为ｐＨ８．０,酶量控制在８００μｍｏｌ／（ｍｉｎ·ｇ）,所获得固定化脂肪酶具有较高的酶活和酶回收率,且有较好的稳定性,其半衰期为３７５ｈ．     

非水相酶法合成葡萄糖月桂酸单酯

为制备葡萄糖月桂酸单酯,引入了苯基硼酸以增加葡剂中的溶解度并改善反应的专一性.通过考察各参数(溶剂类型、酸醇摩尔比、酶添加量、分子筛添加量及温度等)对转化率的影响,确定了最佳工艺条件:葡萄糖浓度50 mmol/L,葡萄糖和苯基硼酸摩尔比为1∶2,反应溶剂为叔丁醇,酸醇摩尔比为3∶1,脂肪酶添加量为20 g/L,分子筛添加量为100 g/L,反应温度为50℃,反应时间24 h,反应体积为10 mL,葡萄糖月桂酸单酯转化率为90.1%.     

离子交换树脂吸附法固定化脂肪酶的研究

以D311离子交换树脂为载体,通过离子交换吸附法对Lipolase100L脂肪酶进行了固定化。采用考马斯亮蓝法测定了酶蛋白在离子交换树脂上的吸附率,考察并得到了酶固定化的最佳条件：在pH10缓冲液下,加酶液量为每克预处理过的树脂加入1.5mL,吸附时间为10h,吸附温度为35℃。所得固定化酶用于催化合成月桂酸月桂醇酯,在反应物质的量比为1∶1时,水质量分数为8%,在50mL异辛烷有机溶剂中固定化酶用量为200mg,反应时间为210min,温度为55℃的最佳条件下,酯化率可达91.3%。     

PVA-SA-活性炭共聚物固定脂肪酶的研究

以聚乙烯醇(PVA)-海藻酸钠(SA)-活性炭共聚物为载体,对脂肪酶进行固定化.研究了活性炭浓度、酶初始浓度、缓冲液pH值、吸附时间及温度对固定化酶的活性及蛋白载量的影响.结果表明:在聚乙烯醇(PVA)-海藻酸钠凝胶中加入1 g/dL活性炭制成复合凝胶球,在25 ℃、pH值5.5的条件下对30 mg/mL的酶液吸附12 h,所得吸附固定化脂肪酶的活性较好.吸附固定的脂肪酶较游离酶的最适作用温度升高10 ℃,最适作用pH范围变宽,且向碱方向偏移0.2个单位.     

连续式酶反应器中脂肪酶催化合成麦芽糖月桂酸酯的研究

利用连续式酶反应器(CSTR)、固定化脂肪酶催化合成麦芽糖月桂酸酯。确定了连续生产工艺的最佳条件:在丙酮介质中,起始反应器中麦芽糖的浓度为50 mmol/L,月桂酸浓度为200mmol/L,加酶量为10 g,每天添加4 g麦芽糖,200 mmol/L的月桂酸丙酮溶液以0.15 mL/min进入反应器。本反应器的麦芽糖酯产量可以达到12.32 g/(L.d),麦芽糖的转化率为58%,高于间歇式生产,而且在生产中不需要添加分子筛。研究了产物的分离纯化方法,利用正己烷对产物进行3次洗涤、离心处理,得到的产物麦芽糖月桂酸酯纯度达到94.16%。     

固定化脂肪酶Lipozyme TL IM催化菜籽油醇解反应合成生物柴油的工艺条件

脂肪酶Lipozyme TL IM在有机相体系中能有效催化菜籽油醇解反应生成生物柴油。作者研究了酶量、底物比率、反应时间、反应温度、转速、水分质量分数、有机溶剂对产物得率的影响。最佳工艺条件为：在正己烷的反应介质中,酶量50%,醇油摩尔比3∶1,反应温度50℃,转速150r/min,添加质量分数5%的水分,反应12 h后产物脂肪酸甲酯得率可达92.3%。     

填充床反应器中固定化假单胞菌细胞连续制备L-瓜氨酸

对实验室筛选的产精氨酸脱亚胺酶的假单胞菌( Pseudomonas sp.)进行了固定化,以及对固定化细胞转化L-精氨酸生产L-瓜氨酸进行了研究.比较4种不同固定化方法,确定卡拉胶包埋结合戊二醛后处理为假单胞菌的细胞固定化方法.固定化反应的最适pH值为6.5,细胞固定化后细胞精氨酸脱亚胺酶的热稳定性增加.在50 mm×240 mm固定填充床反应器中,底物浓度为0.5 mol/L L-精氨酸盐酸盐,pH值6.5,温度37 ℃,稀释速率为0.147/h的条件下,连续运转54 d,固定化细胞对底物的摩尔转化率在95%以上,平均生产强度 0.010 8 g/(h*g)(每单位质量的固定化细胞每小时生产的瓜氨酸质量).转化液经732阳离子树脂吸附,氨水洗脱,及浓缩、结晶,得到纯度为99%的L-瓜氨酸晶体,提取总收率约为87%.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Systemic analgesia adapted to the children's condition

A concept of balanced analgesia using nonsteroidal anti-inflammatory drugs (NSAIDs), paracetamol (acetaminophen), opioids, and corticosteroids can also be used in patients with pre-existing illnesses. NSAIDs are the most effective treatment for acute pain of moderate intensity in children; however, these drugs should be avoided in patients at increased risk for serious side effects, e.g. patients with renal impairment, bleeding tendency, or extreme prematurity. NSAIDs can be given with minimal risks to the younger child with mild to moderate asthma, and, in these patients, the use of steroids can be encouraged; in addition to their antiemetic and analgesic action, a beneficial effect on asthma symptoms can be expected. In the non-intubated child with cerebral trauma, exaggerated sedation caused by opioids and increased bleeding tendency caused by NSAIDs must be avoided. In neonates and small infants, the oral administration of sucrose or glucose is helpful to minimize pain reaction during short uncomfortable interventions.