Action of levorin on glucose transport in the rat small intestine

The technique of accumulating preparation of the mucosa and "turned out sac" was used to show that levorin, a polyenic antibiotic in a concentration of 10(-6) M, lowered the transport rate and accumulation of glucose by the epithelial cells of the rat thin intestine under conditions of oxygenation. Suppression of the glucose transport in the first stages resulted in partial inhibition of the transmembrane transfer. It is suggested that levorin suppression of the glucose transport through the erythrocyte apical membrane in the thin intestine is associated with a decrease in the electrochemical gradient of Na+.     

Variants of fractionation of irradiation in intracavitary gamma-therapy

Under study was the efficacy of three schedules of dose fractionation in intracavitary gamma-therapy in cervical cancer patients treated on the machine "AGAT-B". Single doses were 1000, 700 and 500 rad, while total dosage at point A depending on the stage of the disease was within the range of 4000-5000 rad. The survival during the first, second and third years following termination of the radiotherapy was found to be identical for patients of all the groups under examination. No differences were noted in them also in the character of early radiation reactions on the part of the adjacent organs. The frequency and severity of late radiation injuries of the urinary bladder, rectum and vagina were related to the dose fractionation regimen.     

Peculiarities of primary and secondary structure of phage FI-1 DNA

The composition of nitrous bases of phage FI-1 DNA was studied. As is evidenced from the values of buoyant density in CsCl (p=1,7093 g/cm(3)), melting temperature (T degrees m=86,05 degrees), spectral parameters and direct chromatographic determination, the DNA analysed contains 41,5 mole% pairs of guanine-cystosine. 5-hydroxymethylcytosine and other anomalous bases were not found. Chemical identification and jaxtposition of data of buoyant density in CsCl and Cs2SO4 (p=1,4466 g/cm(3)) and T degrees m. showed the presence of the extra-sugar component in DNA, most likely in the form of hentibiose. Spectral character of thermal denaturation of DNA in different solvents is indicative of the double helixity of its structure. DNA is characterized by enthalpies of conformational transitions "helix coil" (deltaH=12,3 kcal/g) and (deltaH=10 kcal/g) for the solvents, 1 x SSC, and 0,1 x SSC, correspondingly. The presence of extra-sugar in DNA with standard set of nitrous bases is discussed.     

对旋风机级间流场涡量和噪声分布规律的分析

利用LES（大涡模拟）方法对一台对旋风机进行全流场非定常的模拟计算,获得风机内部流场的数值模拟数据。在对旋风机级间流场设置若干监测面,并在监测面的轮毂、流道和机壳位置分别设置监测点,并将对旋风机两级叶轮中间区域的涡量分布情况进行分析,研究对旋风机两级叶轮中间流场涡量分布的特点;利用FW-H噪声模型对对旋风机气动噪声分布情况进行模拟;研究涡量分布与风机噪声特性之间的关系。研究结果可为对旋风机气动噪声分析提供参考。     

自动指纹识别系统中指纹图像分割方法的研究

在研究和分析传统的指纹分割方法：方差法和方向图法的基础上,介绍了一种基于最大类间方差的指纹图像分割方法,并将它和方向图法合理结合,然后提出了一种新的基于方向图和最大类间方差的复合分割方法。该复合分割方法的优点是不仅具有良好的分割效果,而且该方法在运算速度上比传统方法更快,更适合于实时处理。     

塑封电子器件负极端变色原因分析

利用X—RAY光电子能谱仪对125°下,通电15kV,96h后负极一端出现白色物质的塑封电容器进行分析。对比分析性氧化铝结发现,负极一端白色物质为氧化铝富集所致。造成该现象的原因是,环氧塑封料中含有活性氧化铝,由于固化不完全或吸潮导致环氧塑封料中残留水分,残留的水分与活合,在电应力的作用下,有向电源负极迁移的趋势;同时,由于温度效应的存在,塑封树脂软化,加速了水分与活性氧化铝向电源负极迁移的速度,形成了氧化铝在负极端富聚现象,使电容器负极端呈现白色。     

氨气预氮化制备超薄氮化硅薄膜及电学性能

为寻求制备性能良好的纳米厚度氮化硅(SiN_x)薄膜的方法,采用NH_3等离子体氮化、SiH_4/NH_3等离子增强化学淀积法及先氮化后淀积的方法制备了三种SiN_x薄膜,研究比较了三种薄膜的性质。用X射线光电子谱检测了NH_3等离子体氮化Si片得到的SiN_x薄膜的组分,利用椭圆偏振光谱仪测量薄膜厚度,估算了氮化速率。用NH_3和SiH_4作为反应气,分别在原始硅片和经过NH_3预氮化后的硅片上淀积厚度为5 nm、10 nm和50 nm的SiN_x薄膜。用电容-电压法研究了薄膜样品的电学性质,发现单纯用NH_3等离子体氮化的薄膜不适合做介质膜,而先用NH_3氮化再淀积SiN_x的样品比直接淀积SiN_x的样品界面性能明显改善,界面态密度降低到1～2×10~(11)eV~(-1) cm~(-2)。     

Expression of genes encoding the E2 and E3 components of the Bacillus stearothermophilus pyruvate dehydrogenase complex and the stoichiometry of subunit interaction in assembly in vitro

Genes encoding the dihydrolipoyl acetyltransferase (E2) and dihydrolipoyl dehydrogenase (E3) components of the pyruvate dehydrogenase (PDH) multienzyme complex from Bacillus stearothermophilus were overexpressed in Escherichia coli. The E2 component was purified as a large soluble aggregate (molecular mass > 1 x 10(6) Da) with the characteristic 532 symmetry of an icosahedral (60-mer) structure, and the E3 as a homodimer with a molecular mass of 110 kDa. The recombinant E2 component in vitro was capable of binding either 60 E3(alpha2) dimers or 60 heterotetramers (alpha2beta2) of the pyruvate decarboxylase (E1) component (also the product of B. stearothermophilus genes overexpressed in E. coli). Assembling the E2 polypeptide chain into the icosahedral E2 core did not impose any restriction on the binding of E1 or E3 to the peripheral subunit-binding domain in each E2 chain. This has important consequences for the stoichiometry of the assembled complex in vivo. The lipoyl domain of the recombinant E2 protein was found to be unlipoylated, but it could be correctly post-translationally modified in vitro using a recombinant lipoate protein ligase from E. coli. The lipoylated E2 component was able to bind recombinant E1 and E3 components in vitro to generate a PDH complex with a catalytic activity comparable with that of the wild-type enzyme. Reversible unfolding of the recombinant E2 and E3 components in 6 M guanidine hydrochloride was possible in the absence of chaperonins, with recoveries of enzymic activities of 95% and 85%, respectively. However, only 26% of the E1 enzyme activity was recovered under the same conditions as a result of irreversible denaturation of both E1alpha and E1beta. This represents the first complete post-translational modification and assembly of a fully active PDH complex from recombinant proteins in vitro.     

Evidence for retarded kidney growth in sudden infant death syndrome

The aim of the study was to compare the growth rate of the kidneys of infants who died of sudden infant death syndrome (SIDS) and control babies under 1 year; 227 infants who died in St. Petersburg from 1983 to 1990 and who met the criteria for SIDS were included in the study; 138 infants who died suddenly of respiratory infections within the same period constituted a control group. The infants did not have signs of dehydration, malformations, tumours or intrauterine infections. Morphologically the kidneys were intact. Factors which might influence the weight of the kidneys at the time of death were: the cause of death (whether SIDS or not), gender, gestational age, weight, length and ponderal index at birth, age, weight and length at death. Stepwise (forward) linear regression analysis identified three variables which in combination most accurately and independently influenced the predicted weight of the kidneys. These were the cause of death, gender and weight at the time of death. The weight of the kidneys increased by 6.0 g for each increase in total body weight of 1,000 g [95% confidence interval (CI) 5.0-7.0 g], in boys the kidney weight was 3.3 g (95% CI 1.6-5.0 g) higher than in girls and in the SIDS babies kidney weight was 2.5 g (95% CI 0.8-4.2 g) less than controls. Delayed kidney growth may be an indicator of increased risk of SIDS in infants under 1 year and may contribute in some cases.