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Activator System (activator + system)
Kinds of Activator System Selected AbstractsThe Effects of Cyclooxygenase2,ProstaglandinE2 Pathway on Helicobacter pylori -Induced Urokinase-Type Plasminogen Activator System in the Gastric Cancer CellsHELICOBACTER, Issue 3 2008Junichi Iwamoto Abstract Background:, Urokinase-type plasminogen activator (uPA) and its receptor (uPAR) play an important role in the destruction of the extracellular matrix and basement membrane. The induction of uPA and uPAR in the gastric cancer cells with H. pylori has been demonstrated previously. The involvement of COX-2-PGE2 pathway in the uPA system (uPA and uPAR) expression is unclear. Methods:, Gastric cancer cells (MKN45) were co-cultured with H. pylori standard strain (NCTC11637). The specific inductions of uPA and uPAR mRNA were examined by reverse transcription-polymerase chain reaction amplification. The secreted uPA antigen was measured by ELISA. To evaluate the involvement of COX-2 and PGE2 pathway in H. pylori -induced uPA and uPAR expressions, we examined the effects of COX-2 inhibitor and PGE2 receptor antagonist on H. pylori -induced uPA and uPAR expression in the gastric cancer cells. Results:, The expressions of both uPA and uPAR mRNAs in the gastric cancer cells increased obviously (12-fold and 3-fold, respectively) with H. pylori stimulation. The amount of uPA antigen into the culture medium increased dramatically with H. pylori stimulation. The COX-2 expression level in the gastric cancer cells increased remarkably with H. pylori stimulation. H. pylori -induced uPA and uPAR expression levels were suppressed with COX2 inhibitor treatment. The amount of PGE2 antigen into the culture medium increased dramatically 24 hours after H. pylori stimulation. The gastric cancer cells expressed EP2 and EP4 subtypes. EP2 receptor antagonist suppressed the H. pylori -induced uPA and uPAR expressions in the gastric cancer cells. Conclusions:, Our results indicated that COX2-PGE2 pathway may be involved in H. pylori- associated uPA and uPAR induction, and that COX-2 inhibitor or EP2 receptor antagonist may inhibit angiogenesis and tumor invasion via suppression of the uPA system. [source] Comparison of two in vivo models for prostate cancer: Orthotopic and intratesticular inoculation of LNCaP or PC-3 cellsINTERNATIONAL JOURNAL OF UROLOGY, Issue 12 2004KIYOSHI KOSHIDA Abstract, Background:, The critical events in the clinical course of prostate cancer are the occurrence of metastasis and the induction of the hormone-refractory status of the disease. In order to investigate the factors responsible for these events, we need appropriate in vivo models. Materials and methods:, Orthotopic and intratesticular models were created by the injection of LNCaP cells or PC-3 cells into the prostate or testis of severe combined immunodeficient mice. Results:, LNCaP cells in the intratesticular model showed a higher incidence of tumor formation and lymph node metastasis when compared with those in the orthotopic model, while PC-3 cells were highly tumorigenic and metastastic in both models. A high concentration of androgens might play a role in tumor aggressiveness of LNCaP cells, given that enhanced mRNA expressions of integrin ,V and vascular endothelial growth factor was induced by dehydrotestosterone administration in vitro. The high expression of metastasis-related genes, including the urokinase plasminogen activator system, metalloproteinases and vascular endothelial growth factor-C, might be attributed to the high metastatic potential in both models. Interestingly, testicular xenografts of LNCaP cells were able to survive on the subcutis back of castrated male mice as well female mice. Conclusions:, Intratesticular models of prostate cancer appear to be suitable for studying the mechanisms of metastasis and for evaluating various treatment strategies. [source] Post-transcriptional regulation of plasminogen activator inhibitor-1 by intracellular iron in cultured human lung fibroblasts,interaction of an 81-kDa nuclear protein with the 3,-UTRJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 5 2005K. S. RADHA Summary., The proteinase inhibitor, type-1 plasminogen activator inhibitor (PAI-1), is a major regulator of the plasminogen activator system involved in plasmin formation and fibrinolysis. The present study explores the effects of intracellular iron on the expression of PAI-1 and associated cell-surface plasmin activity in human lung fibroblasts; and reports the presence of a novel iron-responsive protein. ELISA revealed a dose-dependent increase in PAI-1 antigen levels expressed in the conditioned medium of cells treated with deferoxamine, in the three cell lines studied. A concomitant increase in mRNA levels was also observed by Northern analyses. Presaturation with ferric citrate quenched the effect of deferoxamine. Experiments with transcription and translation inhibitors on TIG 3-20 cells demonstrated that intracellular iron modulated PAI-1 expression at the post-transcriptional level with the requirement of de-novo protein synthesis. Electrophoretic mobility shift assay and UV crosslinking assays revealed the presence of an ,,81-kDa nuclear protein that interacted with the 3,-UTR of PAI-1 mRNA in an iron-sensitive manner. Finally, we demonstrated that the increased PAI-1 is functional in suppressing cell-surface plasmin activity, a process that can affect wound healing and tissue remodeling. [source] Zirconocene-catalysed propene polymerisation: kinetics, mechanism, and the role of the anionMACROMOLECULAR SYMPOSIA, Issue 1 2004Fuquan Song Abstract The olefin polymerisation activity of metallocene catalysts strongly depends on the counteranion provided by the activator system. The relative activities of a number of new diborate anions [Z(BAr3)2], have been quantified (Z = CN, NH2, N(CN)2; Ar = C6F5 or o -C6F4C6F5). The kinetic parameters for the initiation, propagation and termination steps of propene polymerisations catalysed by (SBI)ZrCl2 have been determined using quenched-flow kinetic and batch techniques [SBI = rac -Me2Si(1-Ind)2]. Comparison of two activator systems, (i) CPh3[B(C6F5)4] / triisobutylaluminium (TIBA) and (ii) methylaluminoxane (MAO) shows, surprisingly, that the concentration of species actively involved in chain growth at any one time is comparable for both systems, although the MAO-activated catalyst is about 20 times less active than the borate system. It is concluded that the counteranion remains sufficiently strongly bound to the metal centre throughout the chain growth sequence to modulate the energetics of monomer insertion. A model suggesting that the monomer binding follows an associative interchange (Ia) mechanism is proposed. [source] Gingival status, crevicular fluid tissue-type plasminogen activator, plasminogen activator inhibitor-2 levels in pregnancy versus post-partumAUSTRALIAN DENTAL JOURNAL, Issue 3 2010N Buduneli Abstract Background:, This study was conducted to evaluate a possible link between periodontal status of pregnant women and the plasminogen activator system in gingival crevicular fluid (GCF). Methods:, GCF samples were obtained from four interproximal sites of anterior teeth in 43 women during the second trimester and also after delivery. Full mouth dental plaque, bleeding on probing (BOP) and probing depth (PD) values were recorded at six sites/tooth in each subject. GCF levels of tissue type plasminogen activator (t-PA) and its inhibitor, plasminogen activator-inhibitor-2 (PAI-2) were determined by ELISA. Data comparisons between pregnancy and post-partum were made by Wilcoxon signed rank test. Results:, The number of pockets with a PD >4 mm and total volume of GCF sampled were reduced significantly after delivery (p = 0.000 and p = 0.013, respectively). No significant differences were detected in GCF concentrations of t-PA or PAI-2 between pregnancy and post-partum. Conclusions:, Our results suggest that GCF t-PA and PAI-2 concentrations are not affected by pregnancy. Reductions in PD values and GCF volume following delivery indicate a resolution of oedema in gingival tissues, possibly related to hormonal changes due to the ending of pregnancy. [source] Synthesis, Characterization, and Reactivity of Lanthanide Complexes with Bulky Silylallyl LigandsISRAEL JOURNAL OF CHEMISTRY, Issue 4 2002Timothy J. Woodman The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH2CHCHSiMe3) (1) reacts with YCl3 in tetrahydrofuran to give the tris -allyl complex Y(CH2CHCHSiMe3)3 (2), while K(CH2CHCHSiMe2tBu) (3) affords Y(CH2CHCHSiMe2tBu)3(THF)1.5 (4). Slow re-crystallization of 4 from light petroleum in the presence of tert -butylcyanide led to multiple insertion to give the sec -amido complex Y{NHC(tBu)(CH)3SiMe2tBu}2{,2 -NHC(tBu)CH=CHCH2SiMe2tBu)CH(CHCHSiMe2tBu)CtBuNH}(THF)·(CH3CH(Me)(CH2)2CH3) (5), which was crystallographically characterized. The reaction of ScCl3(THF)3 with two equivalents of Li{1,3-C3H3(SiMe3)2} in tetrahydrofuran gives the bis -allyl complex {1,3-C3H3(SiMe3)2}2Sc(,-Cl)2Li(THF)2 (6), while the analogous reaction of K{1,3-C3H3(SiMe3)2} (7) with either LaCl3 or YCl3 in tetrahydrofuran affords the bis -allyl complexes MCl{1,3-C3H3(SiMe3)2}2(THF)x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono -allyl complex NdI2{1,3-C3H3(SiMe3)2}(THF)1.25 (10). The reactions of 8 and 9 with triisobutyl aluminum in benzene- d6 show allyl exchange between lanthanide and aluminum. Complexes 8, 9, and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene. [source] Zirconocene-catalysed propene polymerisation: kinetics, mechanism, and the role of the anionMACROMOLECULAR SYMPOSIA, Issue 1 2004Fuquan Song Abstract The olefin polymerisation activity of metallocene catalysts strongly depends on the counteranion provided by the activator system. The relative activities of a number of new diborate anions [Z(BAr3)2], have been quantified (Z = CN, NH2, N(CN)2; Ar = C6F5 or o -C6F4C6F5). The kinetic parameters for the initiation, propagation and termination steps of propene polymerisations catalysed by (SBI)ZrCl2 have been determined using quenched-flow kinetic and batch techniques [SBI = rac -Me2Si(1-Ind)2]. Comparison of two activator systems, (i) CPh3[B(C6F5)4] / triisobutylaluminium (TIBA) and (ii) methylaluminoxane (MAO) shows, surprisingly, that the concentration of species actively involved in chain growth at any one time is comparable for both systems, although the MAO-activated catalyst is about 20 times less active than the borate system. It is concluded that the counteranion remains sufficiently strongly bound to the metal centre throughout the chain growth sequence to modulate the energetics of monomer insertion. A model suggesting that the monomer binding follows an associative interchange (Ia) mechanism is proposed. [source] Polymerization of itaconic acid initiated by a potassium persulfate/N,N -dimethylethanolamine systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008S. J. Veli Abstract The synthesis and characterization of poly(itaconic acid) (PIA) with a novel initiator/activator system is presented. The initiator in this system was potassium persulfate, whereas the activator was N,N -dimethylethanolamine (DMEA). PIA was synthesized in distilled water and in 0.1M HCl at 40°C with reaction times of 72 and 96 h. PIA was investigated with differential scanning calorimetry, gel permeation chromatography, and pulse gradient spin echo-NMR and compared to the same polymer synthesized in dioxane with 2,2,-azobisisobutyronitrile as the initiator. It was shown that, despite the fact that some residual DMEA remained in the system, the properties of the PIA polymerized in the aqueous phase were very similar to the dioxane-synthesized polymer, which will enable a faster, cheaper, and environmentally more acceptable polymerization of itaconic acid. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] | |||||||||||||