电转化法制备高转化效率的E.coli感受态细胞研究

为了制备高转化效率的E.coli TG1和E.coli DH5α感受态细胞,采用电转化方法探索E.coli生长对数期的不同生长阶段、质粒DNA含量、电场强度对E.coli转化效率的影响.研究结果表明40 μL菌液中加1.0 ng pUC19 DNA,用间隙0.2 am电击杯时转化效率最高,E.coli TG1有1个电转化效率峰值,即A600为0.665时,转化效率达1.7×109cfu/μg pUC19 DNA;E.coli DH5α有2个转化效率峰值,即A600为0.443和0.810时,转化效率均为3.0×109cfu/μg pUC19DNA.研究结果表明,在相同情况下E.coli DH5α的转化效率高于E.coliTG1,利用本实验确定的参数可制备出高转化效率的电转化感受态细胞.     

高渗透压对细菌电转化率的影响

研究了革兰氏阴性细菌大肠杆菌JM109和革兰氏阳性细菌地衣芽孢杆菌0204在电转化过程中,高渗溶液如山梨醇、甘露醇、甘油、蔗糖和葡萄糖对其电转化率的影响.结果表明,高渗溶液能够有效保护细胞,提高转化率.在复苏培养基中,0.7mol/L甘露醇对地衣芽孢杆菌0204的保护效果最好,0.1mol/L蔗糖对大肠杆菌JM109的保护效果最好.由此得到质粒DNA对地衣芽孢杆菌0204的最高电转化率为9.8×102转化子/μg,质粒DNA对大肠杆菌JM109的最高电转化率为5.9×108转化子/μg.     

产甘油假丝酵母两种转化方法的比较

为了研究产甘油假丝酵母高产甘油和耐高渗的机制,以Zeocin作为选择标记,考察和比较了两种转化方法,即醋酸锂法和电转化法的转化效果,以建立简单有效的产甘油假丝酵母转化体系。结果表明,细胞生长时期是影响转化率的关键因素。在OD600约为1.3时制备感受态细胞,在电压为1.5 kV时进行电击,可获得较高转化率,为每微克DNA 139个转化子。在OD600约为1.0时制备感受态细胞,醋酸锂预处理细胞1 h,获得的转化率为每微克DNA 154个转化子。综合考虑,醋酸锂法更适合于产甘油假丝酵母的转化。     

毕赤酵母高效电转化方法的探讨

建立一种高效的毕赤酵母电转化方法 ,探讨影响转化效率的因素 ,采用该方法可明显提高转化效率 ,最高可达到 330 0个 / μg DNA,明显提高 TGF- β(转化生长因子 - β)的表达量 ,为研究创伤后的组织修复奠定基础。1　方法p PIC9K- C5 a R质粒按文献 [1]构建 ,毕赤酵母菌GS115 (His-Mut+ )和 KM71(arg4 His4 aox1∷ARG4 ,Invitrogen公司 ) ;按文献 [2 ]的方法制备感受态细胞 ,以每管 80μl分装于 - 80℃冻存备用 ;将p PIC9K- TGF-β质粒分别用 Xmn 和 Xba 酶切 ,取不同量的线性 DNA与冻存不同时间的感受态细胞(取不同生长状态…     

短芽孢杆菌耐碱性木聚糖酶（xylB）的分子生物学研究

根据已发表的环状芽孢杆菌(Bacillus circulan)和枯草芽孢杆菌(Bacillus subtilis)木聚糖酶基因序列设计引物,首次扩增出短芽孢杆菌(Bacillus brevis)中的β-1,4-内切木聚糖酶(以下简称木聚糖酶,E.C.3.2.1.8)基因片段.序列分析表明,该基因与已登录的木聚糖酶基因AF490979.1和AF490980.1分别有97%和96%的同源性,与其它芽孢杆菌属的同源性也较高.将此基因片段插入表达载体pET-30a(+)构建重组质粒,转化大肠杆菌E.coli BL21(DE3).重组基因工程菌破碎后进行SDS-PAGE电泳检测,结果表明,IPTG诱导后,木聚糖酶基因在大肠杆菌的胞内获得高效表达,且酶活力最高可达26.14 U/mL.重组木聚糖酶最适温度为50℃,最适pH为9.0.     

影响根癌农杆菌的电击转化条件

采用电击转化方法将双元载体质粒pCAM3300导入根癌农杆菌LBA4404,研究了不同实验条件对转化率的影响.结果表明:当电场强度为11 kV/cm时,转化率最高,每微克DNA得到9.8×103CFU;在细胞OD600为1.0时进行电转化,转化率最高,每微克DNA得到9.54×103CFU;在一定的细胞浓度范围内,电击转化率与细菌浓度密切相关,转化率随着细菌浓度的上升而上升;质粒大小与电击转化率之间没有明确的关系.将含pCAMBIA3300的根癌农杆菌与粗糙脉胞菌共培养转化,在含有膦化麦黄桐(PPT)(405 mg/L)的平板上筛选到转化子.PCR扩增转化子的染色体,初步证明Bar基因整合进粗糙脉胞菌的染色体中.     

L4～L5坚固芽孢杆菌感染1例报道

芽孢杆菌广泛地存在于自然界当中，与自然界的物质转化密切相关，但芽孢杆菌感染在脊柱感染中甚为罕见。我院2006年3月收治1例L4-L5椎体坚固芽孢杆菌感染患者，总结报告如下。     

蛋白酶产生菌种间原生质体的转化

以地衣形芽抱杆菌(Bacillus licheniformis)AS 1.807—9—9(Thr~-Ade—Str~rRif~5)的原土质体为受体,枯草芽抱杆菌(B.subtilis)ASl.398—28—6(Arg~-Leu~-Rif~rStr~s)*为供体菌,添加聚乙二醇(分子量6000)至终浓度为30%,经过一定时间的保温处理,成功地获得了芽孢杆菌的种间转化子。转化子有的是原养型,有的在含利福平(10单位/亳升)和链霉素(200单位/亳升)的培养基上能生长,也有的兼而有之。上述标记的转化频率在10~(-2)～10~(-5)之间。转化子的产芽孢性能和在含葡萄糖的完全培养基上分泌红色色素的性能亦各有差异,而受体菌是典型产芽孢和分泌红色色素的,供体菌是寡芽孢产株,亦不分泌红色色素。溶菌酶处理时间不同致使原生质体再生率有改变或供体DNA添加量不同都会影响转化频率。转化子的次代回变率约大于60%。原生质体转化可以是转化育种的一种新途径,原生质体也可能是经体外重组DNA的植入受体。     

细菌芽孢形成机制在微生态制剂生产中的应用

益生菌的生存能力和稳定性是生产者在技术和市场方面临的两大挑战。由于芽孢对多种不利环境有极大的抗性而成为近年来益生菌剂中一个研究热点。芽孢的抗性与多种因素有关,并通过芽孢这种独特结构来实现。Spo0A和σ是芽孢形成过程中基因表达的关键调节因子。杆菌和梭菌在芽孢形成中的主要差别是梭菌形成感受态细胞和淀粉粒的积累。为了得到最高的菌体浓度和芽孢形成率,需要优化培养条件。其中,遗传性、接种量、培养温度、pH值、无机盐、淀粉、菌体浓度、营养因子的限量添加都与芽孢的形成有重要关系。     

丁酸菌的分离、鉴定及筛选

从32位健康人的粪便中分离到4株丁酸梭状芽孢杆菌,其中丁酸梭状芽孢杆菌Z 10产酸和细胞生长速度最快.对其安全性评价为基本无毒,并进行了鉴定.     

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.     

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.