高频高压发生器逆变电路的控制方法

高频高压发生器是X线设备的核心部件之一。根据西班牙SEDECAL、美国QUANTUM、日本SHIMADZU与加拿大CPI四大公司生产的高频高压发生器的高压主回路逆变电路,结合高频高压发生器主电路的结构,分析了串联谐振逆变电路的各种控制方式及特点。它将为该类设备的维修、维护提供相应的技术指导。     

一种阻断兔单侧肺动脉血流的方法

由于兔左右肺动脉肺外段的位置较深且受心脏跳动等因素的影响,常规开胸后对其进行手术操作具有一定难度。为建立兔单侧肺动脉缺血模型,我们在兔活体内先找到左右肺动脉的分支标志点,并利用左侧肺动脉的延伸与肺动脉主干的走向基本一致的特点,对左侧肺动脉进行了分离手术试验。同时直接用穿线套管结扎法进行了单侧肺血流阻断和恢复等操作。此外,对结扎或肺动脉１０小时后的肺组织进行的形态学观察表明,肺组织短期缺血不致造成明     

遗传标记和免疫学方法在实验动物质量控制中的应用

生命科学发展迅速,实验动物级别逐渐提高,在保证生物制品实验结果可靠性前提下,完善动物由低级别向高级别过渡显得十分必要,最终目的达到实验动物标准化和动物实验规范化。对实验动物质量控制中的遗传标记和免疫学方法进行了综述。     

一种较好的白鼠灌胃针头简易处理法

一种较好的白鼠灌胃针头简易处理法宋嘉渊（江苏省苏州铁道师范学院生物系,２１５００９）为研究一些药剂、营养物等在人体或动物体内所产生的生理生化反应,常先在白鼠身上作灌胃试验,这就需要用到灌胃针头,而常用的鼠灌胃针头的处理或是用焊锡法,或光把针头磨平、磨...     

Neurospora的一种新的、快速而有效的转化方法

叙述了一种新、快速、有效而可靠的转化Neurospora crassa的方法。本方法用醋酸锂处理萌发的分生孢子,再同DNA保温,然后用聚乙二醇(PEG)处理,然后短时间 热冲击,最后铺选择平板测定。报道了得到高转化率的最适条件。用环状和线状质粒DNA以及基因组DNA都可以得到转化。用相对不纯的DNA制备物如用快速微量制备方法得到的DNA也能进行转化,尽管转化率大大降低。这种转化方法简单而可靠,可大大节省时间和材料。     

一种简便的叶绿体色素纸层析的点样方法

“叶绿体色素的提取与分离”实验中 ,“点样”是用毛细管在滤纸上划滤液线的方法来完成的。现介绍一种用玻璃片“盖印”的点样法 ,优于毛细管点样方法。1　点样玻璃片制作挑选无缺损的载玻片 (75 mm× 2 5 mm× 1mm) ,用玻璃刀横向裁成 10 mm宽的小玻片 (2 5 mm× 10 mm×1mm ) ,此玻片即可用作点样。制成的点样玻片宽的一侧要保证平直无缺损 ,其宽度要小于滤纸条的宽度。因此 ,玻璃片的宽度为 10 mm,滤纸条的宽度可裁成 15 mm为宜。2　操作　　从小漏斗流出的滤液不要用试管收集 ,可直接滴1～ 2滴在 1块干净的载玻片上 ,用点样玻片宽的一侧…     

一种简便的蚤状溞观察方法

蚤状溞(Daphnia pulex)为节肢动物门(Arthropoda)鳃足亚纲(Branchiopoda)动物。分布广泛,常为湖泊池沼的优势种,是鱼类优良的天然饵料。同时,蚤状溞也是一种很好的实验材料。     

A Study of Unusual Pacemaker Infection by Mycobacterium Tuberculosis in Indian Patients

Background

The expanding clinical indications of cardiac rhythm management have led to an increased use of pacemaker implantation which is associated with increased incidence of pacemaker infections. Staphylococcus aureus and epidermidis account for the vast majority of pacemaker infections. Pacemaker infection due to Mycobacterium tuberculosis (M. tuberculosis) is very rare, only few cases having been reported till date.

Methods

We describe here a study of three patients of pacemaker pocket infection with M. tuberculosis.

Conclusion

The possibility of mycobacterial pacemaker infection should always be kept in mind in patients with delayed pacemaker infection.     

Controlling the feed rate of propanol to optimize erythromycin fermentation by on-line capacitance and oxygen uptake rate measurement

The aim of the present study was to optimize the feeding proportion of glucose and propanol for erythromycin biosynthesis by real-time monitoring and exploring its limited ratio by the on-line multi-frequency permittivity measurement. It was found that the capacitance values were sensitive to the variation of biomass concentration and microbial morphology as well as the true state of cell growth. It was most favorable to both cell growth and secondary metabolism to keep the ratio of glucose to propanol at 4.3 (g/g). The specific growth rate calculated by the capacitance measurement correctly and accurately reflected the cell physiological state. An appropriate feed rate of propanol was crucial for cell growth and secondary metabolism, as well as to improve the quality of erythromycin-A. In addition, the erythromycin production titer (10,950 U/mL) was further enhanced by 4 % when the propanol feed was regulated by step-down strategy based on both OUR (oxygen uptake rate) and the on-line monitoring capacitance.     

Pore-to-gate coupling of HCN channels revealed by a pore variant that contributes to gating but not permeation

Although ample evidence suggests the presence of an intracellular activation gate in HCN (pacemaker) channels, mutations in the outer pore can alter gating properties. Here we investigated the role of the outer pore residue A354 in HCN1 gating by systematically converting it to the equivalent residues (T, Y, and F) found in K(+)-channels. A354T negatively shifted steady-state activation (DeltaV(1/2) approximately -25 mV), decelerated gating kinetics (by up to 8-fold), and abolished the effects of external ions on gating. A354Y and A354F did not yield functional currents when expressed alone, although immunofluorescence microscopy indicated the presence of these channel proteins on the membrane surface. Currents recorded after co-expressing A354Y with WT HCN1 were reduced in amplitude (relative to WT alone) and had changes in gating similar to those of A354T. We conclude that the pore variant at position 354 contributes to gating but not permeation, and that the HCN outer pore may be involved in gating via a pore-to-gate coupling mechanism.     

Apical Ballooning Syndrome: A Complication of Dual Chamber Pacemaker Implantation

Apical ballooning is a cardiac syndrome (Takotsubo Cardiomyopathy) described as a typical form of acute transient left ventricular dysfunction. While its onset has often been associated with emotionally or physically stressful situations, it has an overall favorable prognosis. We describe here a case of transient apical ballooning following permanent pacemaker implantation.     

High-rate 3-methylcatechol production in Pseudomonas putida strains by means of a novel expression system

The bioconversion of toluene into 3-methylcatechol was studied as a model system for the production of valuable 3-substituted catechols in general. For this purpose, an improved microbial system for the production of 3-methylcatechol was obtained. Pseudomonas putida strains containing the todC1C2BAD genes involved in the conversion of toluene into 3-methylcatechol were used as hosts for introducing extra copies of these genes by means of a novel integrative expression system. A construct was made containing an expression cassette with the todC1C2BAD genes cloned under the control of the inducible regulatory control region for naphthalene and phenanthrene degradation, nagR. Introducing this construct into wild-type P. putida F1, which degrades toluene via 3-methylcatechol, or into mutant P. putida F107, which accumulates 3-methylcatechol, yielded biocatalysts carrying multiple copies of the expression cassette. As a result, up to 14 mM (1.74 g l(-1)) of 3-methylcatechol was accumulated and the specific production rate reached a level of 105 micromol min(-1) g(-1) cell dry weight, which is four times higher than other catechol production systems. It was shown that these properties were kept stable in the biocatalysts without the need for antibiotics in the production process. This is an important step for obtaining designer biocatalysts.     

A novel technique for ligation of the cephalic vein reduces hemorrhaging during a two-in-one insertion of dual cardiac device leads

The cutdown technique for the cephalic vein is a common access route for transvenous cardiac device leads (TVLs), and sometimes one cephalic vein can accomodate two TVLs. We examined a novel ligation technique to balance the hemostasis and lead maneuverability for this two-in-one insertion. A total of 22 patients scheduled for cardiac device implantations with two or more leads were enrolled. The ipsilateral cephalic vein was identified for inserting the TVLs with a cutdown. If two TVLs could be introduced into one cephalic vein, hemostasis was established by ligating the venous wall between the TVLs. We measured the amount of hemorrhaging per minute and the operators assessed the lead maneuverability before and after the ligation. We successfully implanted cardiac devices in 15 patients (68%) with this novel method, whereas only one TVL could be introduced via the cephalic vein in 7 patients. As for the successful patients, hemorrhaging from the gap was significantly reduced (5.6?±?7.3 to 0.41?±?0.36g/min, p?=?0.016) after the novel ligation. The lead maneuverability was well maintained so there was no difficulty placing the leads into the cardiac chambers in all cases. No major complications were observed. In the present study, the novel ligation method provided significant hemostasis as well as a preserved maneuverability. It could be an optional choice for insertion of multiple TVLs.     

High-rate continuous production of lactic acid by Lactobacillus rhamnosus in a two-stage membrane cell-recycle bioreactor

It is important to produce L(+)-lactic acid at the lowest cost possible for lactic acid to become a candidate monomer material for promising biodegradable polylactic acid. In an effort to develop a high-rate bioreactor that provides high productivity along with a high concentration of lactic acid, the performance of membrane cell-recycle bioreactor (MCRB) was investigated via experimental studies and simulation optimization. Due to greatly increased cell density, high lactic acid productivity, 21.6 g L(-1) h(-1), was obtained in the reactor. The lactic acid concentration, however, could not be increased higher than 83 g/L. When an additional continuous stirred tank reactor (CSTR) was attached next to the MCRB a higher lactic acid concentration of 87 g/L was produced at significant productivity expense. When the two MCRBs were connected in series, 92 g/L lactic acid could be produced with a productivity of 57 g L(-1) h(-1), the highest productivity among the reports of L(+)-lactic acid that obtained lactic acid concentration higher than 85 g/L using glucose substrate. Additionally, the investigation of lactic acid fermentation kinetics resulted in a successful model that represents the characteristics of lactic acid fermentation by Lactobacillus rhamnosus. The model was found to be applicable to most of the existing data with MCRBs and was in good agreement with Levenspiel's product-inhibition model, and the Luedeking-Piret equation for product-formation kinetics appeared to be effective in representing the fermentation kinetics. There was a distinctive difference in the production potential of cells (cell-density-related parameter in Luedeking-Piret equation) as lactic acid concentration increases over 55 g/L, and this finding led to a more precise estimation of bioreactor performance.