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151.
Ian Close Gareth Shackleton Peter S. Goldfarb G. Gordon Gibson Raj Sharma Doug Howes 《Journal of biochemical and molecular toxicology》1992,7(3):193-198
The influence of both single and concurrent administration of phenobarbital and clofibrate on hepatomegaly, cytochrome P450-depen-dent mixed function oxidase activities, and peroxisome proliferation in male rat liver have been studied. Both xenobiotics separately increase the liver :body weight ratio and their combined administration results in greater hepatomegaly than either compound alone. Both compounds induce NADPH-cytochrome c(P450) reductase activity and laurate ω- and ω-1-hydroxylase activities, but only phenobarbital induces pentoxyresorufin-O-de-alkylase. None of the drug treatments induced microsomal cytochrome b5. Phenobarbital did not cause peroxisome proliferation and inhibited the corresponding clofibrate-dependent proliferation. Taken collectively, our studies have demonstrated that concomitant treatment with phenobarbital and clofibrate are largely permissive with respect to the hepatic mixed function oxidase system but have opposing effects on the phenomenon of peroxisome proliferation in the same tissue. 相似文献
152.
Mechanisms of resistance in the rice cultivar Manikpukha to the rice stem nematode Ditylenchus angustus 下载免费PDF全文
Shakhina Khanam Lander Bauters Richard Raj Singh Ruben Verbeek Ashley Haeck Saeed M. D. Sultan Kristof Demeestere Tina Kyndt Godelieve Gheysen 《Molecular Plant Pathology》2018,19(6):1391-1402
The incompatible interaction between the rice cultivar Manikpukha and the rice stem nematode Ditylenchus angustus has been reported recently. This research focuses on the underlying mechanisms of resistance in Manikpukha. Invasion, post‐infection development and reproduction of D. angustus were compared in compatible and incompatible interactions to identify the stage in which resistance occurs. The results indicate that resistance in Manikpukha is associated with reduced development and reproduction, implying that resistance acts post‐invasion. We studied the possible involvement of three classical defence hormones, salicylic acid (SA), jasmonic acid (JA) and ethylene (ET), in response to infection in a compatible interaction using biosynthesis/signalling‐deficient transgenic rice lines. All three hormones appear to have an influence on the basal defence of Nipponbare against the stem nematode. Although hormone application increases basal defences, expression studies and hormone analyses after nematode infection in Manikpukha did not show a clear involvement of the hormone defense pathways for SA, ET and JA. However, it seems that OsPAL1 plays a pivotal role in resistance, indicating that the phenylpropanoid pathway and its products might be key players in the incompatible interaction. Lignin measurement showed that, although basal levels are similar, Manikpukha had a significantly higher lignin content on nematode infection, whereas it was decreased in the susceptible cultivar. The results presented here show that SA, ET and JA are involved in basal defences, but the resistance of Manikpukha against D. angustus probably relies on products of the phenylpropanoid pathway. 相似文献
153.
Morgado L Bruix M Londer YY Pokkuluri PR Schiffer M Salgueiro CA 《Biochemical and biophysical research communications》2007,360(1):194-198
Multiheme c-type cytochromes from members of the Desulfovibrionacea and Geobactereacea families play crucial roles in the bioenergetics of these microorganisms. Thermodynamic studies using NMR and visible spectroscopic techniques on tetraheme cytochromes c(3) isolated from Desulfovibrio spp. and more recently on a triheme cytochrome from Geobacter sulfurreducens showed that the properties of each redox centre are modulated by the neighbouring redox centres enabling these proteins to perform energy transduction and thus contributing to cellular energy conservation. Electron/proton transfer coupling relies on redox-linked conformational changes that were addressed for some multiheme cytochromes from the comparison of protein structure of fully reduced and fully oxidised forms. In this work, we identify for the first time in a multiheme cytochrome the simultaneous presence of two different conformations in solution. This was achieved by probing the different oxidation stages of a triheme cytochrome isolated from G. sulfurreducens using 2D-NMR techniques. The results presented here will be the foundations to evaluate the modulation of the redox centres properties by conformational changes that occur during the reoxidation of a multiheme protein. 相似文献
154.
Han J Farnsworth RL Tiwari JL Tian J Lee H Ikonomi P Byrnes AP Goodman JL Puri RK 《Genomics》2006,87(4):552-559
Changes in cell culture conditions influence the metabolism of cells, which consequently affects the quality of the products that they produce, such as viral vectors, recombinant proteins, or vaccines. Currently there is no effective technique available to monitor global quality of cells in cell culture. Here we describe a new method using gene expression profiling by microarray to predict the quality of cell substrates. Human embryonic kidney 293 cells are a commonly used cell substrate in the production of biological products. We demonstrate that the yield of adenoviral vectors was lower in over-confluent 293 cells, compared to 40 or 90% confluent cells. Total RNA derived from these cells of different confluence states was reverse transcribed, labeled, and used to hybridize 10K cDNA arrays to determine biomarkers for confluence states. Phenotype scatter-plot analysis and cluster analysis were used for class discovery. Based on this approach, we identified genes that were either up-regulated or down-modulated in response to different cell confluence states. By multivariate predictive models we identified a set of 37 genes that were either down-regulated or up-regulated compared to 90% confluent cells as a predictor of cell confluence and quality of 293 cell cultures. The predictive accuracy of these models was assessed by the leave-one-out cross-validation method. The expression of selected gene predictors was validated by quantitative PCR analysis. Our results demonstrate that gene expression profiling can assess the quality of cell substrates prior to large-scale production of a biological product. 相似文献
155.
Hitesh Jagani Josyula Venkata Rao Vasanth Raj Palanimuthu Raghu Chandrashekar Hariharapura Sagar Gang 《Cellular & molecular biology letters》2013,18(1):120-136
Overexpression of anti-apoptotic Bcl-2 is often observed in a wide variety of human cancers. It prevents the induction of apoptosis in neoplastic cells and contributes to resistance to chemotherapy. RNA interference has emerged as an efficient and selective technique for gene silencing. The potential to use small interfering RNA (siRNA) as a therapeutic agent for the treatment of cancer has elicited a great deal of interest. However, insufficient cellular uptake and poor stability have limited its therapeutic applications. The purpose of this study was to prepare chitosan nanoparticles via ionic gelation of chitosan by tripolyphosphate for effective delivery of siRNA to silence the anti-apoptotic Bcl-2 gene in neoplastic cells. Chitosan nanoparticles loaded with siRNA were in the size range 190 to 340 nm with a polydispersive index ranging from 0.04 to 0.2. They were able to completely bind with siRNA, provide protection against nuclease degradation, and enhance the transfection. Cell culture studies revealed that nanoparticles with entrapped siRNA could efficiently silence the antiapoptotic Bcl-2 gene. Studies on Swiss albino mice showed that siRNA could be effectively delivered through nanoparticles. There was significant decrease in the tumor volume. Blocking the expression of anti-apoptotic Bcl-2 can enhance the sensitivity of cancerous cells to anti-cancer drugs and the apoptosis rate. Therefore, nanoformulations with siRNA can be promoted as an adjuvant therapy in combination with anti-cancer drugs. 相似文献
156.
Subramanian Mohan Raj Chelladurai Rathnasingh Woo-Chel Jung Edwardraja Selvakumar Sunghoon Park 《Biotechnology and Bioprocess Engineering》2010,15(1):131-138
3-Hydroxypropionic acid (3-HP), a versatile and valuable platform chemical, has diverse industrial applications; but its biological
production from glycerol is often limited by the capability of the enzyme aldehyde dehydrogenase (ALDH) to convert an intermediary
compound, 3-hydroxypropionaldehyde (3-HPA), to 3-HP. In this study, we report a new ALDH, PuuC, from Klebsiella pneumoniae DSM 2026, that efficiently converts 3-HPA to 3-HP. The identified gene puuC was cloned, expressed in Escherichia coli, purified, and characterized for its properties. The recombinant enzyme with a molecular weight of 53.8 kDa exhibited broad
substrate specificity for various aliphatic aldehydes, especially C2–C5 aldehydes. NAD+ was the preferred coenzyme for the oxidation of most aliphatic and aromatic aldehydes tested. The optimum pH and temperature
for PuuC activity were pH 8.0 and 45°C. The K
m values for 3-HPA and NAD+ were 0.48 and 0.09 mM, respectively. The activity of PuuC was enhanced in the presence of reducing agents such as 2-mercaptoethanol
or dithiothreitol, while several metal ions, particularly Hg2+, Ag+, and Cu2+ inhibited its activity. The predicted structure of PuuC indicated the presence of K191 and E194 in close proximity to the
glycine motif, suggesting that PuuC belongs to class 2 ALDHs. 相似文献
157.
Subramanian Mohan Raj Chelladurai Rathnasingh Woo-Chel Jung Sunghoon Park 《Applied microbiology and biotechnology》2009,84(4):649-657
The stability and specific activity of endo-β-1,4-glucanase III from Trichoderma reesei QM9414 was enhanced, and the expression efficiency of its encoding gene, egl3, was optimized by directed evolution using error-prone PCR and activity screening in Escherichia coli RosettaBlue (DE3) pLacI as a host. Relationship between increase in yield of active enzyme in the clones and improvement
in its stability was observed among the mutants obtained in the present study. The clone harboring the best mutant 2R4 (G41E/T110P/K173M/Y195F/P201S/N218I)
selected in via second-round mutagenesis after optimal recombinating of first-round mutations produced 130-fold higher amount
of mutant enzyme than the transformant with wild-type EG III. Mutant 2R4 produced by the clone showed broad pH stability (4.4–8.8)
and thermotolerance (entirely active at 55°C for 30 min) compared with those of the wild-type EG III (pH stability, 4.4–5.2;
thermostability, inactive at 55°C for 30 min). k
cat of 2R4 against carboxymethyl-cellulose was about 1.4-fold higher than that of the wild type, though the K
m became twice of that of the wild type. 相似文献
158.
159.
Synthesis, microbicidal activity, and solution structure of the dodecapeptide from bovine neutrophils 总被引:1,自引:0,他引:1
The dodecapepetide sequence R-L-C-R-I-V-V-I-R-V-C-R with a disulfide bridge between the cysteine residues found in bovine neutrophils was synthesized by solid-phase procedures. Its antimicrobial activity against oral microorganisms such as Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Streptococcus mutans, and Streptococcus gordonii was examined, and its structural features were examined by CD and determined by two-dimensional (2D) nmr. The strains P. gingivalis (W50 and 381), A. actinomycetemcomitans (Y4 and 67), S. gordonii (DL1), and S. mutans (GS5) are found to be highly sensitive to this peptide at 2-2.5 microM concentrations, suggesting that the dodecapeptide is a potent antibiotic for oral pathogens. The weak negative n-sigma* band observed at approximately 265-270 nm in the CD spectra of this peptide provides evidence for the presence of a disulfide bridge. The negative n-pi* band at approximately 200 nm and the positive pi-pi* band at 185 nm suggest a folded structure for this peptide. The negative n-pi* shifts from 200 to 206 nm with an increase in intensity in dipalmitoylphosphotidylcholine vesicles, suggesting that the peptide might associate to form higher order aggregates in lipid medium. The assignment of backbone and side-chain proton resonances has been accomplished by the combined analysis of 2D total correlated and nuclear Overhauser effect spectroscopy. The temperature dependence of amide NH chemical shifts and (1)H-(2)H exchange effect on amide NH resonances indicate the involvement of amide NH groups of Cys3, Ile5, Ile8, Val10, and Arg12 in intramolecular hydrogen bonding. The coupling constant (J(NH-C(alpha)H)) values, the set of medium-, short-, and long-range nuclear Overhauser effects, and the results of restrained structure calculation using the distance geometry algorithm for nmr applications provide evidence for a folded, loop-like structure with a type I (III) beta-turn involving Ile5, Val6, Val7, and Ile8, and two antiparallel beta-strands involving the N-terminal Arg1, Leu2, Cys3, and Val4 and the C-terminal Arg9, Val10, Cys11, and Arg12 residues. The structure of the dodecapeptide mimics the amphiphilic structure of large 30-35 residue defensins and the peptide appears to exhibit similar antimicrobial potency. 相似文献
160.