气升式发酵罐发酵黄原胶的动力学

利用黄单孢菌研究了在50L气升式发酵罐发酵黄原胶的动力学,在logistic方程和Luedeking Piret方程的基础上,建立了两步发酵黄原胶的动力学模型,并对模型和实验数据进行了比较,进一步在200L相似结构的气升式发酵罐中的试验表明,该模型能较好的对发酵动力学进行描述.     

透明质酸分批发酵的动力学模型

透明质酸是一种具有特殊生理功能的高分子多糖 ,在医药和化妆品工业中有着广泛的用途 .以兽疫链球菌 (Streptococcuszooepidemicus)为生产菌株 ,葡萄糖为碳源 ,在 2 .5L小型发酵罐上对发酵过程的动力学进行了研究 ,利用功能单元理论建立了以碳源为限制性底物的动力学模型 .采用计算机对实验数据进行的计算 ,拟合出模型参数 ;对模型的适用性进行考察 ,证明了该模型有较宽的适用范围 .     

一株产高质量浓度酒精酵母的间歇发酵动力学初步研究

对一株产高质量浓度酒精的酿酒酵母的间歇发酵动力学进行了初步研究.分别对基质、产物和菌体对时间的变化,所得回归方程显示,3个状态参量与时间呈对数关系;而后采用比生长速率、某一时段的菌体浓度、某一时段的葡萄糖质量浓度、某一时段的酒精质量浓度来描述整个发酵过程中菌体、基质和产物之间的关系,通过二次曲面回归得到了间歇发酵动力学数学模型,与传统的Monod模型和Logistic模型相比,该模型对试验数据拟合和预测性能较好.最后,用Simplex优化方法对间歇发酵动力学进行动态模拟,得到很好的拟合结果.将得到的模型参数用于预测初糖质量浓度为24.7g/dL的间歇发酵,预测结果也较好.因此,该模型可用来预测高初糖质量浓度下间歇发酵过程.     

酰胺化桔皮果胶凝胶流变学性质研究及动力学分析(Ⅱ)

通过流变学方法对酰胺化桔皮果胶的凝胶过程进行动力学分析.探讨不同凝胶体系的凝胶形成速率的影响因素;后采用程序降温动力学模型对果胶溶液在冷却过程中弹性模量的变化进行动力学分析,得到了代表两个凝胶过程的不同温度范围,不同的范围内其凝胶活化能有很大差别.     

药动学-药效学模型与效应室目标控制输注

药动学-药效学模型是将药代动力学模型和药效动力学模型有机地结合起来,研究药物剂量与药物效应之间的 定量关系。其中效应室消除速率常数(ke0)是重要的模型参数.描述药物在中央室和效应室之间平衡的快慢,也是效应室目标 控制输注的重要参数。效应室目标控制输注比血药浓度目标控制输注的起效时间更短,而副作用并不明显增加。     

主动脉分支支架的血流动力学分析

目的 探讨主动脉分支支架内血流动力学的变化情况.方法 基于2020年12月中国科学技术大学第一附属医院收治的1例Stanford B型主动脉夹层患者的增强计算机断层扫描血管造影(CTA)影像数据进行图像分割和三维模型重建,构建不同深度的胸主动脉分支支架模型,采用数值模拟的方法模拟分支支架植入后,分析分支支架内血流动力学...     

肝硬变形成过程中自发门—体分流形成的研究

目的:研究在肝硬变逐渐形成过程中自发门-体分流的形成及其与血流动力学变化的关系.方法:采用γ标记微球法.对大鼠四氯化碳肝硬变模型的自发门-体分流及血流动力学变化进行研究.结果:在肝硬变形成过程中.门脉压.门脉阻力等血流动力学参数逐渐发生变化,肝硬变形成后变化更加显著.门脉阻力增加出现在门脉压尚未明显升高前.自发门-体分流在肝硬变形成后才建立,且个体间差异较大;未发现其与某单项血流动力学参数间有相关关系.结沦;自发门-体分流的建立可能需要足够高的门脉压.     

主动脉夹层的血流动力学数值仿真

目的建立基于CT的胸主动脉夹层有限元模型并进行血流动力学数值模拟,为分析胸主动脉夹层的血流动力学机理及其临床治疗提供理论依据。方法依据胸主动脉夹层患者CT数据,用MIMICS 13.0数字化影像处理软件,获取胸主动脉夹层的优化表面模型,随后导入ANSYS 11.0进行胸主动脉夹层模型的有限元体网格划分。最后在ANSYS CFX 11.0中完成胸主动脉夹层的血流动力学分析。结果成功建立了临床上适用于胸主动脉夹层患者血流动力学分析的有限元模型。获得了个性化胸主动脉夹层模型中血液流场的流线、速度矢量、血管壁面压力和血管壁面切应力的分布和变化。结论模型具有数字化、个性化特征,可用于胸主动脉夹层血液动力学计算和临床胸主动脉夹层患者的破裂机理的研究。     

仅吻合单根动脉指尖再植的血流动力学研究

目的 分析仅吻合单根动脉指尖再植存活的临床现象,探讨其血流动力学机制.方法 建立流体力学试验模型,确立仅吻合单根动脉指尖再植存活的血流动力学机制,并对36指仅吻合单根动脉存活的指尖再植进行总结.结果 实验证实该流体力学试验模型的成立.临床上36指指尖再植,存活34指,失败2指,成活率为94.5%.再植术后2周彩色超声检查证实:仅吻合单根动脉吻合口的近端侧支存在回流.结论 仅吻合单根动脉指尖再植存活机制主要是动脉吻合口近端的侧支回流.     

全麻下儿童丙泊酚的药代动力学特征

目的 研究全麻下儿童丙泊酚的药代动力学特征.方法 选择拟在全麻下行择期手术的患儿19例,ASA Ⅰ或Ⅱ级.丙泊酚3 mg/kg在上肢静脉约30 S左右注射完毕,注药后1、2、4、6、10、15、30、60、90、150、210、300、420 min从右颈内静脉抽取1.5 ml全血.血浆药物浓度的测定方法采用反相高效液相色谱技术,应用3p87软件包拟合总的药代动力学参数.结果 最终药代动力学参数：清除速率常数（k10）0.1616/min,1室向2室转运速率常数（k12）0.0640/min,2室向1室转运速率常数（k21）0.0062/min,分布半衰期（T1/2α）4.1176 min,清除半衰期（T1/2β）123.9559 min,清除率（CL）0.0745 L·min^-1·kg^-1,中央室分布容积（Vc）0.9505 L/kg,表观分布容积（Va）27.4100 L/kg.未发现体重等变量和各个药代动力学参数间有线性方程可建立.结论 丙泊酚在儿童的药代学模型呈二室模型,符合线性药代动力学特点.儿童丙泊酚的药代动力学特征明显不同于成人.     

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.