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161.
162.
Our earlier studies with outer membrane permeability in E. coli showed that an insertion mutation in lpp gene (encoding Braun's lipoprotein) drastically changed the outer membrane permeability, resulting in significant acceleration of whole-cell catalyzed reactions. In order to gain a mechanistic understanding of the nature of permeability change, the lpp region was sequenced. The results revealed that Lpp was not expressed in the insertion mutant, suggesting that the absence, rather than the alteration, of Lpp is responsible for the observed permeability change. This surprising result prompts us to investigate the possibility of establishing lpp deletion as a general permeabilization method. Two lpp deletion mutants were generated from strains with different genetic background and the effect of lpp deletion on cell physiology was investigated. While lpp deletion had no significant effect on cell growth, carbon metabolism, and fatty acid compositions, it enhanced permeability of various small molecules, consistent with the results with the insertion mutant. This phenotype is useful in a wide range of biotechnological applications. We illustrate here the use of the mutant with organophosphate hydrolysis and L-carnitine synthesis, where permeability is known to be a limiting factor. Both processes were significantly improved with the mutant because of enhanced permeability through the outer membrane. Therefore, this study has established an easy yet generally applicable method for permeabilizing E. coli cells without significant adverse effects. Further, as lpp homolog is known to exist in gram-negative bacteria, we expect that this method will be applicable to other gram-negative bacteria. 相似文献
163.
Differential effects of endoplasmic reticulum stress-induced autophagy on cell survival 总被引:1,自引:0,他引:1
Ding WX Ni HM Gao W Hou YF Melan MA Chen X Stolz DB Shao ZM Yin XM 《The Journal of biological chemistry》2007,282(7):4702-4710
Autophagy is a cellular response to adverse environment and stress, but its significance in cell survival is not always clear. Here we show that autophagy could be induced in the mammalian cells by chemicals, such as A23187, tunicamycin, thapsigargin, and brefeldin A, that cause endoplasmic reticulum stress. Endoplasmic reticulum stress-induced autophagy is important for clearing polyubiquitinated protein aggregates and for reducing cellular vacuolization in HCT116 colon cancer cells and DU145 prostate cancer cells, thus mitigating endoplasmic reticulum stress and protecting against cell death. In contrast, autophagy induced by the same chemicals does not confer protection in a normal human colon cell line and in the non-transformed murine embryonic fibroblasts but rather contributes to cell death. Thus the impact of autophagy on cell survival during endoplasmic reticulum stress is likely contingent on the status of cells, which could be explored for tumor-specific therapy. 相似文献
164.
165.
Ca2+ fluxes through ionotropic glutamate receptors regulate a variety of developmental processes, including neurite outgrowth and naturally occurring cell death. In the CNS, NMDA receptors were originally thought to be the sole source of Ca2+ influx through glutamate receptors; however, AMPA receptors also allow a significant influx of Ca2+ ions. The Ca2+ permeability of AMPA receptors is regulated by the insertion of one or more edited GluR2 subunits. In this study, we tested the possibility that changes in GluR2 expression regulate the Ca2+ permeability of AMPA receptors during a critical period of neuronal development in chick lumbar motoneurons. GluR2 expression is absent between embryonic day (E) 5 and E7, but increases significantly by E8 in the chick ventral spinal cord. Increased GluR2 protein expression is correlated with parallel changes in GluR2 mRNA in the motoneuron pool. Electrophysiological recordings of kainate-evoked currents indicate a significant reduction in the Ca2(+)-permeability of AMPA receptors between E6 and E11. Kainate-evoked currents were sensitive to the AMPA receptor blocker GYKI 52466. Application of AMPA or kainate generates a significant increase in the intracellular Ca2+ concentration in E6 spinal motoneurons, but generates a small response in older neurons. Changes in the Ca(2+)-permeability of AMPA receptors are not mediated by age-dependent changes in the editing pattern of GluR2 subunits. These findings raise the possibility that Ca2+ influx through Ca(2+)-permeable AMPA receptors plays an important role during early embryonic development in chick spinal motoneurons. 相似文献
166.
Wang Juan Ni Hong Chen Li Chen Chengbin Song Wenqin 《Frontiers of Biology in China》2007,2(3):272-275
Cancer-related genes harbored in the loss regions containing a high frequency of hepatocellular carcinoma (HCC) were selected.
Related information was gathered and the coding single nucleotide polymorphism (cSNP) sequences were obtained from the single
nucleotide polymorphism (SNP) database. The appropriate primers and oligonucleotide probes were then designed in accordance
with the SNP sites, and subsequently, the gene chips for detecting SNPs were constructed. Genomic DNA was extracted from blood
samples of healthy controls and from patients with HBV infection. The sequences, including the SNPs, were amplified via polymerase
chain reaction (PCR) and labeled using digoxigenin deoxyuridine tri-phosphate (Dig-dUTP). The labeled products were then hybridized
with the SNP chips. Results confirmed that the differences in allele frequencies of three SNPs EGFL3 (rs947345), Caspase9
(rs2308950), and E2F2 (rs3218171) were distinct between HBV-infected patients and controls, suggesting that these SNPs ocuring
in high frequency in HBV-infected individuals may be associated with susceptibility to HCC.
Translated from Acta Scientiarum Naturalium Universitatis Nankaiensis, 2006, 39(3): 1–5 [译自: 南开大学学报(自然科学版)] 相似文献
167.
Oleanolic Acid Induces Apoptosis in Human Leukemia Cells through Caspase Activation and Poly(ADP-ribose) Polymerase Cleavage 总被引:3,自引:0,他引:3
It has been shown that Fructus Ligustri Lucidi (FLL), a promising traditional Chinese medicine, can inhibit the growth of tumors. However, the effective component and molecular mechanism of FLL act to inhibit tumor proliferation are unclear. In this study, we demonstrated that oleanolic acid (OA), a principal chemical component of FLL, inhibited the proliferation of human leukemia HL60 cells in culture. MTT assay showed that treatment of HL60 cells with FLL crude extracts or OA dramatically blocked the growth of target tumor cell in a time- and dose-dependent manner. Morphological changes of the nuclei and DNA fragmentation showed that apoptotic cell death occurred in the HL60 cells after treating with FLL extracts (20 mg/ml) or OA (3.65×10^-2 mg/ml). Furthermore, flow cytometry assay showed that treatment of HL60 cells with FLL or OA caused an increased accumulation of G1 and sub-G1 subpopulations. Western blot analysis showed that caspase-9 and caspase-3 were activated, accompanied by the cleavage of poly (ADP-ribose) polymerase (PARP) in the target cells during FLL- or OA-induced apoptosis, These results suggest that OA acts as the effective component of FLL by exerting its cytotoxicity towards target tumor cells through activation of caspases and cleavage of PARP. 相似文献
168.
Development and validation of a LC-MS/MS method for the determination of viaminate in human plasma 总被引:1,自引:0,他引:1
Yin J Ni KY Shen Y Ma PC Cao L Wang WP Wang Y 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2007,856(1-2):376-380
A sensitive and specific method for determination of viaminate in human plasma by using high-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC-MS/MS) was developed in this study. The plasma samples were simply deproteinated, extracted, evaporated, and then reconstituted in 200 microl of methanol prior to analysis. Chromatographic separation was carried out on a Shimadzu VP-ODS column (250 mm x 2.0 mm, 5 microm) with a mobile phase of methanol-water (95:5, v/v) at a flow rate of 0.2 ml/min. Quantification was performed in the negative-ion electrospray ionization mode by selected ion monitoring of the product ions at m/z 164 for viaminate and m/z 109 for testosterone propionate which was used as the internal standard. The corresponding parent ions were m/z 446 and m/z 345. A linear calibration curve was observed within the concentration range of 0.10-200 ng/ml. The lowest limit of quantitation (LLOQ) was 0.1 ng/ml. The extraction-efficiency at three concentrations was 100.7, 93.6, and 99.7%. Practical utility of this new LC-MS/MS method was confirmed in pilot pharmacokinetic studies in humans following oral administration. 相似文献
169.
170.
Perini Fernando A. Macrini Thomas E. Flynn John J. Bamba Kanvaly Ni Xijun Croft Darin A. Wyss André R. 《Journal of Mammalian Evolution》2022,29(2):369-394
Journal of Mammalian Evolution - Cranial endocasts are one of the most direct tools available to obtain information about the endocranial cavity of fossil mammals, but few anatomical comparisons... 相似文献