Defects in a proteolytic step of light-harvesting complex II in an<Emphasis Type="Italic">Arabidopsis</Emphasis> stay-green mutant,<Emphasis Type="Italic">ore10</Emphasis>, during dark-induced leaf senescence

During dark-induced leaf senescence (DIS), the non-functional stay-green mutantore10 showed delayed chlorophyll (Chl) degradation and increased stability in its light-harvesting complex II (LHCII). These phenomena were closely related to the formation of aggregates that mainly consisted of terminal-truncated LHCII (Oh et al., 2003). Theore10 mutant apparently lacks the protease needed to degrade the truncated LHCII. In wild-type (WT) plants, protease was found in the thylakoid fraction, but not the soluble fraction. A similar experiment using dansylated LHCII revealed that the protease degraded both WT andore10 LHCII, indicating that its stability inore10 perhaps did not result from a defect in the LHCII polypeptides themselves. Although protease activity was not present in non-senesced WT leaves, it was induced during DIS. It also was possible to diminish the high level of protease present in the thylakoids through high-salt washing, suggesting that this enzyme is extrinsically bound to the outer surface of the stroma-exposed thylakoid regions.     

3,3',4,4',5-Pentachlorobiphenyl (PCB 126) impacts hepatic lipid peroxidation, membrane fluidity and beta-adrenoceptor kinetics in chick embryos

Polychlorinated biphenyls (PCB) and other aryl hydrocarbon receptor (AHR) agonists induce oxidative stress and alter membrane lipid peroxidation and fluidity. This study tested the hypothesis that PCB-induced changes in membrane properties impact membrane beta-adrenoceptor (beta-AR) affinity and capacity in chick embryo hepatocytes. Embryos were injected into the air cell with 1.6 microg 3,3',4,4',5-pentachlorobiphenyl (PCB 126)/kg egg at day 0, and incubated to day 19 when livers were removed. This dose resulted in hepatic PCB 126 levels of 0.67 ng/g liver or 10.2 ng/g liver lipid; levels in untreated embryos were non-detectable. Hepatic microsomal EROD activity was elevated by approximately 12-fold and embryo mortality was significantly increased compared with the untreated group. Hepatic lipid peroxidation increased and membrane order (steady-state fluorescence anisotropy values) decreased with in ovo PCB 126 exposure. Consistent with changes in membrane structure, hepatic beta-AR affinity for CGP 12177 significantly decreased (Kd increased) without changes in receptor numbers. This study demonstrates that in ovo exposure to PCB 126 in chick eggs significantly impacted embryo survival, and this was correlated with altered hepatic membrane structure and ultimately membrane function.     

Synthesis and biological evaluation of novel apio nucleosides with thiazole-4-carboxamide and 1,2,4-triazole-3-carboxamide

In view of biological activities of azole nucleosides and apio-dideoxynucleoside, novel apio nucleoside analogues (1 and 2) with thiazole and triazole base moiety were synthesized using 2,3-O-isopropylidene-apio-beta-D-furanose (3), which was prepared from D-mannose.     

Hydrophilic interaction liquid chromatography-tandem mass spectrometry for the determination of levosulpiride in human plasma

A rapid, sensitive and selective hydrophilic interaction liquid chromatography-tandem mass spectrometric (HILIC-MS/MS) method for the determination of levosulpiride in human plasma was developed. Levosulpiride and internal standard, tiapride were extracted from human plasma with ethyl acetate at pH 11 and analyzed on an Atlantis HILIC silica column with the mobile phase of acetonitrile-ammonium formate (190 mM, pH 3.0) (94:6, v/v). The analytes were detected using an electrospray ionization tandem mass spectrometry in the multiple-reaction-monitoring mode. The standard curve was linear (r = 0.999) over the concentration range of 1.00-200 ng/ml. The lower limit of quantification for levosulpiride was 1.00 ng/ml using 100 microl plasma sample. The coefficient of variation and relative error for intra- and inter-assay at three quality control (QC) levels were 3.8-9.1 and -2.9 to -0.1%, respectively. The recoveries of levosulpiride ranged from 80.5 to 87.4%, with that of tiapride (internal standard) being 84.6%. This method was successfully applied to the pharmacokinetic study of levosulpiride in humans.     

WNT and beta-catenin signalling: diseases and therapies

WNT signalling has been studied primarily in developing embryos, in which cells respond to WNTs in a context-dependent manner through changes in survival and proliferation, cell fate and movement. But WNTs also have important functions in adults, and aberrant signalling by WNT pathways is linked to a range of diseases, most notably cancer. What is the full range of diseases that involve WNT pathways? Can inhibition of WNT signalling form the basis of an effective therapy for some cancers? Could activation of WNT signalling provide new therapies for other clinical conditions? Finally, on the basis of recent experiments, might WNTs normally participate in self-renewal, proliferation or differentiation of stem cells? If so, altering WNT signalling might be beneficial to the use of stem cells for therapeutic means.     

Molecular mechanisms of heptaplatin effective against cisplatin-resistant cancer cell lines: less involvement of metallothionein

Background  

Heptaplatin is a new platinum derivative with anticancer activity against various cancer cell lines, including cisplatin-resistant cancer cell lines (Cancer Chemother Pharmacol 1995; 35: 441).     

Effect of quercetin and its conjugated metabolite on the hydrogen peroxide-induced intracellular production of reactive oxygen species in mouse fibroblasts

To clarify the antioxidative role of quercetin metabolites in cellular oxidative stress, we measured the inhibitory effects of the quercetin aglycon and quercetin 3-O-beta-D-glucuronide (Q3GA), which is one of the quercetin metabolites in the blood after an intake of quercetin-rich food, on the production of hydrogen peroxide (H2O2)-induced intracellular reactive oxygen species in mouse fibroblast 3T3 cultured cells. When the cells were exposed to H2O2 in the presence of quercetin or Q3GA, Q3GA was found to be less effective than quercetin. In the case of a pretreatment with quercetin or Q3GA before the exposure, Q3GA, but not the quercetin aglycon, exerted an inhibitory effect, although its cellular uptake was unlikely. The quercetin aglycon appeared to fail in its antioxidative effect due to metabolic conversion into isorhamnetin conjugates, with substantial oxidative degradation resulting from the pretreatment. It is, therefore, suggested that quercetin metabolites take part in the protection of intracellular oxidative stress induced by the extraneous attack of H2O2.     

Regulation of lymphocyte clustering by CD30-mediated ICAM-1 up-regulation

CD30 is expressed transiently on activated B and T lymphocytes and constitutively on several B- and T cell lymphomas. CD30 functions include participation in negative selection of thymocytes, costimulation of activated T cells, isotype switching of B cells, and regulation of the effector activity of cytotoxic lymphocytes. Although CD30 is not a marker for T helper 2 (TH2) cells, it may participate in the polarization of TH1 and TH2 cells. The pleiotropic functions of CD30 are initiated by interaction of CD30-expressing cells with other immune competent cells expressing CD30-L and providing the signals for modulation of effector cell activity. Here, we report that CD30 signals generated by anti-CD30 on activated, normal murine T cells strongly up-regulate the expression of intercellular adhesion molecule 1 (ICAM-1, CD54), and to a lesser extent, ICAM-2 (CD102). CD30 signals moreover delay the subsequent decline of ICAM expression. CD30 cross-linking did not alter the expression of CD11a/CD18 (LFA-1), the counter receptor for ICAM abundant on T cells. CD30-mediated ICAM-1 up-regulation is independent of cytokine secretion and appears to be transmitted directly through NF-kappaB activation. CD30-mediated up-regulation of ICAM-1 expression led to a significant increase in cluster formation of lymph node cells. Increased lymphocyte self-aggregation mediated by CD30 may set the stage for fraternal signaling to modulate lymphocyte function.