外科动物实验中猪的麻醉问题

猪作为重要的实验动物,在外科实验中运用传统的麻醉方法时易引起呼吸道阻塞而死亡,我们使用全麻插管技术,并辅以术前术后各种对症处理,成功地解决了手术中猪因呼吸道阻塞而死亡的问题。     

荧光素浓度对于用荧光素酶测定ATP含量的影响

在粗荧光素酶液中加合成的荧光素和不加荧光素,观察其发光反应动力学,反应系统中外加荧光素后,发光强度明显增加,以适当低浓度的荧光素酶液的发光强度增加最大。在室温(20℃)下,不同贮放时间的荧光素酶液,其反应活性随贮放时间的延长而下降。外加荧光素后,反应活性可以恢复并达到最大后保持恒定。在-15℃贮放一年后的荧光素酶粉剂,反应活性下降,外加荧光素后,反应活性可以提高到原来的水平。     

有关植物体内"渗透作用"教学的几点改进

在植物生理教学中 ,渗透作用是一个重点问题 ,为使学生透彻理解、灵活运用相关知识 ,我们在教学过程中利用改进的图例 ,对渗透作用的讲解进行了一些改进。　　　　　　　图 1　渗透现象　　　　　　　　　　　　图 2　　　 1.实验开始时　 2 .经过一段时间　　首先讲解教材中的渗透作用实验图 (图 1) :绑有半透膜 (蚕豆种皮或猪膀胱 )的漏斗中装入蔗糖溶液 ,放在盛有清水的烧杯之中 ,半透膜两侧的水势差推动水分从高水势的烧杯流向低水势的漏斗中 ,致使漏斗中液面升高。在液面逐渐上升的过程中 ,由这段液柱造成的液体压强也逐渐增大 ,漏斗中…     

正交实验法优化超临界二氧化碳萃取桑叶总黄酮

探索采用超临界CO_2法萃取桑叶中总黄酮提取的最佳方案。利用超临界二氧化碳萃取技术,依次用正交实验方法考查萃取压强、萃取温度、萃取时间以及夹带剂流速对于桑叶中总黄酮得率的影响,优选提取桑叶黄酮类化合物提取的最佳工艺条件。结果显示,正交实验的最佳萃取条件为:萃取压强为25 MPa,萃取温度为40℃,萃取时间为3 h,夹带剂无水乙醇流速为2.5 mL/min,该条件下,总黄酮得率为6.19%±0.26%,可重复性良好。采用超临界二氧化碳萃取桑叶中黄酮类物质的总黄酮提取率较高,为进一步开发桑叶实验提供了理论和实验依据。     

凝胶过滤层析参数对家蝇蛋白粗提液分离效果的影响

考察了凝胶过滤介质、层析柱直径、柱床高度和洗脱流速对家蝇Muscadomestica蛋白粗提液分离效果的影响,结果表明：凝胶过滤介质种类、层析柱直径、柱床高度、洗脱流速均能不同程度地影响家蝇蛋白粗提液的分离效果。在实验范围内,选择1.3 cm直径、40 cm柱床高度的Sephadex G-75,以0.4 mL/min的流速洗脱时,对家蝇蛋白粗提液的分离效果比较理想。     

SPF和正常鼠下呼吸道菌群多样性研究

目的 探讨SPF和正常鼠下呼吸道菌群多样性区别,为研究洁净环境下呼吸道菌群对免疫耐受形成的影响提供简便的动物模型.方法 采用飞行质谱和DGGE的方法检测正常和SPF BALB/c小鼠及Wistar大鼠呼吸道支气管肺泡灌洗液中菌群多样性的区别.结果 SPF BALB/c小鼠下呼吸道菌群丰度小于普通小鼠,下呼吸道菌群丰度小于消化道.SPF Wistar大鼠下呼吸道菌群丰度小于普通大鼠.结论 SPF环境造成鼠下呼吸道菌群丰度减小.     

YlyA和RNA聚合酶的反应性鉴定

目的：用亲和层析法鉴定YlyA与RNA聚合酶（RNAP）的结合性能。方法：将YlyA分别上样于以Affigel 15为亲和介质制备的空白柱、牛血清白蛋白（BSA）柱和RNAP柱;以GreA和绿色荧光蛋白（GFP）为阳性和阴性对照蛋白分别上样于同一RNAP柱,洗涤和洗脱缓冲液（pH均为7．9）的盐离子浓度分别为30mmol／L和400mmol／L;用免疫印迹法对洗涤和洗脱流出液中的YlyA进行检测。结果：在空白柱和BSA柱的洗脱收集液中,没有检测到YlyA,大量的YlyA出现在了洗涤收集液中;而在RNAP柱的洗脱收集液中,检测到了YlyA和GreA,没有检测到GFP。结论：YlyA与RNAP之间具有特异性结合能力,为YlyA极有可能是一种转录因子的生物信息学分析结果提供了实验证据。     

抗胰岛素样生长因子1受体单链抗体复性研究

[目的]建立抗人胰岛素样生长因子1受体单链抗体包涵体复性方法。[方法]首先,在96孔板上进行稀释复性,从72种复性液中筛选最佳条件。每孔复性液2 m L,滴入起始浓度1. 5 mg/m L的包涵体溶解液100μL过夜复性。然后,选择最佳复性液与变性液混合在Superdex 75柱上形成1 cm柱长下降5%的变性液梯度,样品按5%柱体积上样进行柱上复性。[结果]最适稀释复性液为C8(50 mmol/L Tris-Cl,GSH/GSSG=5/0. 5 mmol/L,0. 4 mol/L精氨酸,p H 9.0),对应复性率约为78%;以该复性液为基础通过柱上复性,目标蛋白复性率提高到95%,复性样品抗原结合活性良好。[结论]建立了目标蛋白包涵体柱上复性方法,复性率达到95%,产量达到384 mg/L。     

葡萄糖和氢对Gunnera／Nostoc固氮共生体固氮活力的影响

Ｇｕｎｎｅｒａ／Ｎｏｓｔｏｃ固氮共生体固氮相对效率（ＲＥ）可在０．２６～０．８０之间变动,而不是一个常数。外加１．５％葡萄糖液可使其固氮活力提高约１００％,同时也使组织的呼吸速率提高了近１６０％。加外源Ｈ２可使其固氮活力提高近１００％,但却使组织的呼吸速率降低了近５０％。正常生长条件下的组织净放Ｈ２量较低．而外源２％葡萄糖液可使组织净放Ｈ２量提高近２倍。外加５ｍｍｏｌ／Ｌ的ＮＨ１Ｃｌ溶液可使其固氮活力下降约７０％。故认为Ｇｕｎｎｅｒａ／Ｎｏｓｔｏｃ共生体固氮活力受碳水化合物供应状况及比代谢两者构成的“还原力库”或“电子库”的调节,在此“还原力库”中,Ｈ２代谢起到了一个“中间调节者”的作用。     

成人下呼吸感染病例合胞病毒(RSV)RNA的检测分析

呼吸道合胞病毒（ＲＳＶ）被公认为婴幼儿呼吸道感染最常见的病毒性病原体,有关ＲＳＶ在成人急性下呼吸道感染中病原作用的研究,受检测技术制约,国内外很少报导［１］,近年来ＲＳＶ致成人下呼吸道感染病例有增加趋势,且引起的成人急性下呼吸道感染症状与其他呼吸道病...     

Mechanisms of surface-tension-induced epithelial cell damage in a model of pulmonary airway reopening.

Airway collapse and reopening due to mechanical ventilation exerts mechanical stress on airway walls and injures surfactant-compromised lungs. The reopening of a collapsed airway was modeled experimentally and computationally by the progression of a semi-infinite bubble in a narrow fluid-occluded channel. The extent of injury caused by bubble progression to pulmonary epithelial cells lining the channel was evaluated. Counterintuitively, cell damage increased with decreasing opening velocity. The presence of pulmonary surfactant, Infasurf, completely abated the injury. These results support the hypotheses that mechanical stresses associated with airway reopening injure pulmonary epithelial cells and that pulmonary surfactant protects the epithelium from this injury. Computational simulations identified the magnitudes of components of the stress cycle associated with airway reopening (shear stress, pressure, shear stress gradient, or pressure gradient) that may be injurious to the epithelial cells. By comparing these magnitudes to the observed damage, we conclude that the steep pressure gradient near the bubble front was the most likely cause of the observed cellular damage.     

Effects of pharyngeal lubrication on the opening of obstructed upper airway.

We examined the effect of electrical stimulation of the hypoglossal nerve and pharyngeal lubrication with artificial surfactant (Surfactant T-A) on the opening of obstructed upper airway in nine anesthetized supine dogs. The upper airway was isolated from the lower airway by transecting the cervical trachea. Upper airway obstruction was induced by applying constant negative pressures (5, 10, 20, and 30 cmH2O) on the rostral cut end of the trachea. Peripheral cut ends of the hypoglossal nerves were electrically stimulated by square-wave pulses at various frequencies from 10 to 30 Hz (0.2-ms duration, 5-7 V), and the critical stimulating frequency necessary for opening the obstructed upper airway was measured at each driving pressure before and after pharyngeal lubrication with artificial surfactant. The critical stimulation frequency for upper airway opening significantly increased as upper airway pressure became more negative and significantly decreased with lubrication of the upper airway. These findings suggest that greater muscle tone of the genioglossus is needed to open the occluded upper airway with larger negative intraluminal pressure and that lubrication of the pharyngeal mucosa with artificial surfactant facilitates reopening of the upper airway.     

Aerosol deposition in the airway model with excessive mucus secretions

Aerosol deposition in the airways with excessive mucus secretions was investigated utilizing an in vitro airway model lined with various mucus simulants of differing rheological properties. The airway model was made with a straight glass tube (1.0 cm ID and 20 cm in length) and positioned vertically. The mucus simulants were supplied into the tube at a constant rate and made to move upward through the tube as a thin layer (0.6-1.7 mm) undergoing a random wave motion by means of upward airflow. Aerosols (3.0 and 5.0-micron diam) were passed through the mucus-lined tube at flow rates of 0.33-1.17 l/s, and the deposition of the aerosols in the tube was determined by sampling the aerosols at the inlet and the outlet of the tube on filters. During the sampling, pressure drop across the tube model was also measured. Deposition efficiency in the 20-cm-long mucus-lined tube ranged from 13 to 92% with 3.0-micron-diam particles and from 66 to 98% with 5.0-micron-diam particles. This deposition was 25-300 times higher than that in the dry tube. The deposition was higher with increasing viscosity of mucus but was lower with increasing elasticity of mucus. Pressure drop across the mucus-lined tube was much higher than that in the dry tube, and the increase was more prominent with mucous layers with higher viscosity but lower elasticity values. Therefore, aerosol deposition showed a good positive relationship with pressure drop. However, percent increase of aerosol deposition in the mucus-lined tube was 2-5 times higher than that of pressure drop.(ABSTRACT TRUNCATED AT 250 WORDS)     

Airway closure: occluding liquid bridges in strongly buckled elastic tubes.

This paper is concerned with the airway closure problem and investigates the quasi-steady deformation characteristics of strongly collapsed (buckled) airways occluded by liquid bridges of high surface tension. The airway wall is modeled as a thin-walled elastic shell, which deforms in response to an external pressure and to the compression due to the surface tension of the liquid bridge. The governing equations are solved numerically using physiological parameter values. It is shown that axisymmetric configurations are statically unstable, as are buckled tubes whose opposite walls are not in contact. The quasi-steady deformation characteristics of strongly collapsed airways whose walls are in opposite wall contact show a pronounced hysteresis during the collapse/reopening cycle. Buckling is shown to occur over a short axial length with moderate circumferential wavenumbers. Finally, further implications of the results for the airway collapse/reopening problem are discussed.     

Effects of surface tension and viscosity on airway reopening

We studied airway opening in a benchtop model intended to mimic bronchial walls held in apposition by airway lining fluid. We measured the relationship between the airway opening velocity (U) and the applied airway opening pressure in thin-walled polyethylene tubes of different radii (R) using lining fluids of different surface tensions (gamma) and viscosities (mu). Axial wall tension (T) was applied to modify the apparent wall compliance characteristics, and the lining film thickness (H) was varied. Increasing mu or gamma or decreasing R or T led to an increase in the airway opening pressures. The effect of H depended on T: when T was small, opening pressures increased slightly as H was decreased; when T was large, opening pressure was independent of H. Using dimensional analysis, we found that the relative importance of viscous and surface tension forces depends on the capillary number (Ca = microU/gamma). When Ca is small, the opening pressure is approximately 8 gamma/R and acts as an apparent "yield pressure" that must be exceeded before airway opening can begin. When Ca is large (Ca greater than 0.5), viscous forces add appreciably to the overall opening pressures. Based on these results, predictions of airway opening times suggest that airway closure can persist through a considerable portion of inspiration when lining fluid viscosity or surface tension are elevated.     

Influence of airway diameter and cell confluence on epithelial cell injury in an in vitro model of airway reopening.

Recent advances in the ventilation of patients with acute respiratory distress syndrome (ARDS), including ventilation at low lung volumes, have resulted in a decreased mortality rate. However, even low-lung volume ventilation may exacerbate lung injury due to the cyclic opening and closing of fluid-occluded airways. Specifically, the hydrodynamic stresses generated during airway reopening may result in epithelial cell (EpC) injury. We utilized an in vitro cell culture model of airway reopening to investigate the effect of reopening velocity, airway diameter, cell confluence, and cyclic closure/reopening on cellular injury. Reopening dynamics were simulated by propagating a constant-velocity air bubble in an adjustable-height parallel-plate flow chamber. This chamber was occluded with different types of fluids and contained either a confluent or a subconfluent monolayer of EpC. Fluorescence microscopy was used to quantify morphological properties and percentage of dead cells under different experimental conditions. Decreasing channel height and reopening velocity resulted in a larger percentage of dead cells due to an increase in the spatial pressure gradient applied to the EpC. These results indicate that distal regions of the lung are more prone to injury and that rapid inflation may be cytoprotective. Repeated reopening events and subconfluent conditions resulted in significant cellular detachment. In addition, we observed a larger percentage of dead cells under subconfluent conditions. Analysis of this data suggests that in addition to the magnitude of the hydrodynamic stresses generated during reopening, EpC morphological, biomechanical, and microstructural properties may also be important determinants of cell injury.     

Lungs under cyclic compression and expansion

The pressure-volume relationship of lungs subjected to repeated compression and expansion is studied in detail. The investigation was motivated by an attempt to understand why lungs are frequently injured by compression waves; hence the lung was compressed to a degree greater than normally encountered in physiological conditions. Attention was focused on the collapse of the lung at a critical strain and the reopening of the trap at a critical stress. We found that when a rabbit lung is compressed, about one-half to one-quarter of its gas may be trapped in the alveoli because of the closure of airways. Reopening of the trap occurs at a pressure higher than the critical pressure for collapsing. The difference of the critical pressures of collapsing and reopening is influenced by the rate of strain and the strain history, especially by the maximum compressive stress imposed on the lung. The stress-strain relationship of the lung tissue, which resembles the PV curves, depends strongly on the strain history.     

Small airway pressure-diameter relationships during nonhomogeneous lung lobe inflation

The pressure-diameter behavior of airways within a collaterally ventilating segment of lung was evaluated radiographically in 12 excised dog lung lobes. The results were compared with the pressure-diameter behavior of airways in a lung region adjacent to the collaterally ventilating segment. Airways in each lung region were dusted with powdered tantalum, and airway diameters were measured during homogeneous and nonhomogeneous lobe inflation. Intrasegmental and extrasegmental airways behaved similarly during homogeneous lobe inflation; airway diameter increased as alveolar pressure increased. The lobe was inflated nonhomogeneously by raising pressure in the collaterally ventilating segment (Ps) while maintaining pressure at the lobar bronchus (Pao) constant at 5, 10, or 15 cmH2O. Increasing Ps at constant Pao reciprocally affected intrasegmental and extrasegmental airways. When Pao was low, intrasegmental airways were expanded, and extrasegmental airways were compressed when Ps was raised. When Pao was high, airway diameter was unaffected by increasing Ps presumably because the airways were already maximally expanded. A comparison of diameters during homogenous and nonhomogenous lobe inflation suggests a very small interdependence effect from the parenchyma surrounding the collaterally ventilating segment. These results demonstrate the combined effects of parenchymal properties and airway pressure-diameter relationships in determining the effect of local lung distortion on airway function.     

Capillary-elastic instabilities of liquid-lined lung airways

To model the competition between capillary and elastic forces in controlling the shape of a small lung airway and its interior liquid lining, we compute the equilibrium configurations of a liquid-lined, externally pressurized, buckled elastic tube. We impose axial uniformity and assume that the liquid wets the tube wall with zero contact angle. Non-zero surface tension has a profound effect on the tube's quasi-steady inflation-deflation characteristics. At low liquid volumes, hysteresis arises through two distinct mechanisms, depending on the buckling wavenumber. Sufficient compression always leads to abrupt and irreversible collapse and flooding of the tube; flooding is promoted by increasing liquid volumes or surface tension. The model captures mechanisms whereby capillary-elastic instabilities can lead to airway closure.