The surface morphology of normal and malignant rat liver epithelial cells in culture

Summary A direct comparison has been made between normal parenchymal cells cultured from rat liver and malignant cells from both a rat liver tumor and a spontaneously transformed line derived from the parent rat culture. In all nondividing cells there was a 3- to 5-fold increase in the population of surface microvilli on the malignant cells compared to the normal cells. Notable variations in overall morphology were also observed when cells were incubated in arginine-deficient medium. During the course of this work T. D. Allen and P. T. Iype were supported by grants from the Medical Research Council and Cancer Research Campaign, and M. J. Murphy, Jr. was supported by a Special Fellowship of the Leukemia Society of America, Inc. and the Jean Shaland Fund.     

Studies on the binary and ternary complexes formed by a neurospora glutamate dehydrogenase and its substrates

The NADP⁺ specific glutamate dehydrogenase from wild-type $\text{Neurospora crassa}$ forms a stable binary complex with NADPH. This can combine with L-glutamate, α-ketoglutarate or the substrate analogue D-glutamate to form ternary complexes which can be distinguished by their different fluorescence properties. The affinity of the enzyme for NADPH diminishes with increases in pH or ionic strength of the solution. Experimental data obtained using modified glutamate dehydrogenases from mutant strains of $\text{N. crassa}$ suggest that the reduced-coenzyme binding sites observed fluorimetrically are the same as those observed by enzyme kinetics.     

Antioxidant Activity of New Sulphur- and Selenium-Containing Analogues of Potassium Phenosan against H2O2-Induced Cytotoxicity in Tumour Cells

Among known phenolic antioxidants, the overwhelming majority of compounds have lipophilic properties and the number of known water-soluble compounds is very small. The list of hydrophilic phenolic antioxidants can be expanded via the synthesis of a structurally related series of polyfunctional compounds for further research on their biological activity in vitro. New sulphur- and selenium-containing analogues of antioxidant potassium phenosan were synthesised. In vitro cytotoxicity and cytostaticity as well as antioxidant activity against H₂O₂-induced cytotoxicity to human cell lines (HepG2, Hep-2 and MCF-7) were investigated by high-content analysis. A selenium-containing analogue showed higher biological activity than did a sulphur-containing one. As compared to the activity of potassium phenosan, the selenium-containing analogue had a cell line-dependent antioxidant effect against H₂O₂-induced cytotoxicity: comparable in HepG2 cells and greater in Hep-2 cells. The selenium-containing analogue significantly increased the death of MCF-7 cells at concentrations above 50 µM. The sulphur-containing analogue has lower biological activity as compared to potassium phenosan and the selenium-containing analogue.     

溶解性有机碳在红壤水稻土中的吸附及其影响因素

吸附作用是影响土壤中溶解性有机碳(DOC)迁移转化及生物有效性的重要反应过程,研究DOC在土壤中的吸附行为,对正确阐明土壤有机碳的循环和转化特征以及进行污染风险评估有重要意义.采用平衡法研究了红壤水稻土对DOC的吸附特征,并分析土壤有机质、粘粒含量及pH值与DOC吸附量之间的关系.结果表明,供试土壤对DOC的吸附等温线符合Freundlich和Linear方程.不同土壤对DOC的吸附能力有明显差异.在相同浓度下,DOC吸附量以第四纪红色粘土发育的低肥力水稻土最大,第三纪红砂岩风化物发育的低肥力水稻土次之,两种高肥力水稻土最小.土壤对DOC的吸附过程分为快、慢两个阶段,0-0.25 h内DOC的吸附速率最大,随着时间的推移,吸附速率渐小,2-4 h后基本达到吸附平衡.描述供试土壤对DOC吸附动力学过程的最优模型为一级扩散方程,其次为Elovich方程和抛物扩散方程.粘粒含量和有机质是影响土壤DOC吸附量的重要因素,随着粘粒含量的增加,有机质含量的降低,DOC的吸附量增大.     

Detention and mixing in free water wetlands

Mixing was studied in free water surface wetland receiving pumped river water, by measurement of the non-interacting tracer lithium. The flow pattern was found to be intermediate between plug flow and well-mixed. The nominal detention time, calculated from volume aand flow, was 50% larger than the mean tracer detention time. The peak time was found to be one-half the tracer detention time. Three models were constructed: plug flow with dispersion, tanks in series, and a series-parallel network of tanks. All proved capable of fitting the exit tracer concentration curves but the network model provided a better fit to internal measurements. Pumping frequency was high enough to allow use of an average flowrate. The degree of mixing, as characterized by the variance of the exit tracer response curve, was comparable to that found by other researchers for wetlands, ponds and rivers.     

High-resolution finite element models with tissue strength asymmetry accurately predict failure of trabecular bone

The ability to predict trabecular failure using microstructure-based computational models would greatly facilitate study of trabecular structure–function relations, multiaxial strength, and tissue remodeling. We hypothesized that high-resolution finite element models of trabecular bone that include cortical-like strength asymmetry at the tissue level, could predict apparent level failure of trabecular bone for multiple loading modes. A bilinear constitutive model with asymmetric tissue yield strains in tension and compression was applied to simulate failure in high-resolution finite element models of seven bovine tibial specimens. Tissue modulus was reduced by 95% when tissue principal strains exceeded the tissue yield strains. Linear models were first calibrated for effective tissue modulus against specimen-specific experimental measures of apparent modulus, producing effective tissue moduli of (mean±S.D.) 18.7±3.4 GPa. Next, a parameter study was performed on a single specimen to estimate the tissue level tensile and compressive yield strains. These values, 0.60% strain in tension and 1.01% strain in compression, were then used in non-linear analyses of all seven specimens to predict failure for apparent tensile, compressive, and shear loading. When compared to apparent yield properties previously measured for the same type of bone, the model predictions of both the stresses and strains at failure were not statistically different for any loading case (p>0.15). Use of symmetric tissue strengths could not match the experimental data. These findings establish that, once effective tissue modulus is calibrated and uniform but asymmetric tissue failure strains are used, the resulting models can capture the apparent strength behavior to an outstanding level of accuracy. As such, these computational models have reached a level of fidelity that qualifies them as surrogates for destructive mechanical testing of real specimens.     

综述与专论: 针对严重急性呼吸综合征冠状病毒2变异株Omicron的疫苗研究进展

2021年底,严重急性呼吸综合征冠状病毒2 Omicron变异株迅速取代Delta突变株在世界范围内广泛流行,其S蛋白具有36个位点突变,导致致病力和传播力发生明显变化,并且具备了免疫逃逸的能力。疫苗接种是目前疫情防控最普适的手段,研究发现,现有疫苗针对Omicron突变株的保护效果明显下降。新的免疫策略或特异性疫苗/多价疫苗针对Omicron有效性的评估均需要动物模型的支撑。在实验室条件下,利用动物模型进行活病毒攻击实验,是在体内验证保护性中和抗体、疫苗有效性的关键技术手段,本文将从动物模型方向综述国内外针对Omicron变异株的疫苗研究进展。     

An application of the theoretical group methods to modeling of complex systems

The applicability of theoretical group methods to studying complex physical and biological systems with the potential of self-organization was demonstrated. The problem of calculating climate sensitivity parameters taking into account the cyclone-anticyclone structure of the atmosphere optically dense in the infrared region is considered as an example.     

Reconfiguration of a Multi-oscillator Network by Light in the Drosophila Circadian Clock

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Homology modeling threedimensional structure of AnxB1 and reducing its immunogenicity by sequence-deleted mutagenesis

AnxB1,a novel annexin previously isolated from Cysticercus cellulose,shows high thrombi affinity and anticoagulant activity in vivo.In order to investigate the relationship between structure and biological function,a predicted three-dimensional(3D)model of AnxB1 was generated by homology modeling.This model contains four homologous internal-domains and the Cα trace of domain Ⅰ,Ⅱ and IV shows high similarity.Based on the structure characterization,four sequence-deleted mutants were constructed and expressed as GST fusion proteins in E.coli.Two of the mutants,GST-M3 and GST-M4 reserved high anticoagulant activity(p＜0.01 vs.GST).Furthermore,compared with the wild type GST-AnxB1,the immunogenicity of GST-M3 and GST-M4 was reduced significantly(p＜0.01)and the molecular weight was lowered to 27 kD and 34 kD,respectively.These observations laid a solid foundation for further study on developing new thrombolytic agents with higher efficiency and lower side effect.