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991.
Sobhani I Canedo S Alchepo B Vissuzaine C Chevalier C Buyse M Moizo L Laigneau JP Mignon M Lewin JM Bado A 《American journal of physiology. Gastrointestinal and liver physiology》2002,282(4):G727-G734
Helicobacter pylori may increase or inhibit gastric acid. We studied acid variations and plasma gastrin in cats harboring Helicobacter felis, harboring H. pylori, or free of gastric pathogens with reference to thioperamide (H(3) receptor antagonist) and SR-27417A (PAF receptor antagonist). In cats harboring H. felis, gastric mucosa were histologically normal. After H. felis eradication, pentagastrin-stimulated acid secretion was increased (40%) compared with the situation before eradication. Thioperamide abolished this inhibitory effect of H. felis, whereas SR-27417A did not. Basal and meal-stimulated plasma gastrin levels were not affected by eradication therapy. Acid secretion was inhibited (-80%) in week 3, increased from weeks 5 to 9, and remained constant for up to 42 weeks after H. pylori infection. SR-27417A had no effect on acid secretion before week 8 but inhibited it thereafter, and thioperamide increased it (20%) only before week 7 in those cats. Helicobacter inhibits gastric acid via an H(3) receptor pathway. Inflammatory mediators are thus involved in adaptation to the inhibitory effects of H. pylori on acid secretion. 相似文献
992.
Fritz JJ Lewin A Hauswirth W Agarwal A Grant M Shaw L 《Methods (San Diego, Calif.)》2002,28(2):276-285
Hammerhead ribozymes are catalytic RNAs that are being used to inhibit endogenous gene expression to study key components of basic biochemical pathways such as angiogenesis. In addition, these ribozymes have the potential to be used as components of gene therapy protocols for the treatment of disease states. We detail here a set of protocols for the design and testing of hammerhead ribozymes that will efficiently inhibit gene expression both in cell culture and in vivo. 相似文献
993.
994.
Ecology of the red-tide dinoflagellate Ceratium furca: distribution, mixotrophy, and grazing impact on ciliate populations of Chesapeake Bay 总被引:1,自引:0,他引:1
Ceratium furca is a primarily photosynthetic dinoflagellate also capable of ingesting other protists. During 1995 and 1996, we documented the abundance of C. furca in Chesapeake Bay and determined grazing rates on prey labeled with fluorescent microspheres. Abundance usually remained below 20 cells ml(-1), although the species was capable of localized late-summer blooms (< or = 478 cells ml(-1)) in the more saline lower to mid-Bay region. Feeding rates ranged from 0 to 0.11 prey dinoflagellate(-1) h(-1) or from 0 to 37 pg C dinoflagellate(-1) h(-1) and were highest at lower salinities. Clearance rates averaged 2.5 +/- 0.35 microl dinoflagellate(-1) h(-1). Impact of C. furca feeding on prey populations was higher in the lower Bay, averaging 67% of Strobilidium spp. removed d(-1). Ingestion rates were positively correlated with prey abundance and dissolved inorganic nitrogen, but negatively with salinity, depth, dissolved inorganic phosphorus, and inorganic P:N ratio. Daily consumption of prey biomass by C. furca averaged 4.6% of body carbon, 6.5% of body nitrogen, and 4.0% of body phosphorus. with maximal values of 36, 51, and 32%, respectively. Thus, the ability to exploit an organic nutrient source when inorganic nutrients are limiting may give C. furca a competitive advantage over purely photosynthetic species. 相似文献
995.
Regulation of virulence gene expression in Vibrio cholerae by quorum sensing: HapR functions at the aphA promoter 总被引:2,自引:0,他引:2
Quorum sensing negatively influences virulence gene expression in certain toxigenic Vibrio cholerae strains. At high cell densities, the response regulator LuxO fails to reduce the expression of HapR, which, in turn, represses the expression of the virulence cascade. A critical regulatory step in the cascade is activation of tcpPH expression by AphA and AphB. We show here that HapR influences the virulence cascade by directly repressing aphA expression. In strain C6706, aphA expression was increased in a delta hapR mutant and decreased in a delta luxO mutant, indicating a negative and positive influence, respectively, of these gene products on the promoter. Overexpression of HapR also reduced aphA expression in both C6706 and Escherichia coli. DNase I footprinting showed that purified HapR binds to the aphA promoter between -85 and -58. Although it appears that quorum sensing does not influence virulence gene expression in strain O395 solely because of a frameshift in hapR, overproduced HapR did not repress expression from the O395 aphA promoter in either Vibrio or E. coli, nor did the protein bind to the promoter. Two basepair differences from C6706 are present in the O395 HapR binding site at -85 and -77. Introducing the -77 change into C6706 prevented HapR binding and repression of aphA expression. This mutation also eliminated the repression of toxin-co-regulated pilus (TCP) and cholera toxin (CT) that occurs in a delta luxO mutant, indicating that HapR function at aphA is critical for density-dependent regulation of virulence genes. 相似文献
996.
997.
Penile corpus cavernosum smooth muscle relaxation can be induced by both cyclic AMP and cyclic GMP-elevating agents, but possible interactions between these two signalling pathways are still poorly understood. Using in vitro cultured rat penile corpus cavernosum smooth muscle (CCSM) cells, we have characterized the local expression and functional activities of receptors for the cAMP-elevating peptides, PACAP and VIP, and for the cGMP-elevating peptides, CNP and ANP. Stimulation of the cells with various concentrations of PACAP(-27/-38) or VIP resulted in rapid and dose-dependent increases in cyclic AMP levels. RT-PCR analyses revealed gene expression of PAC(1) and VPAC(2) but not of VPAC(1) receptors in the cells. The natriuretic peptide, CNP, and the nitric oxide donor, sodium nitroprusside, were capable of enhancing cyclic GMP formation, indicating the presence of membrane-associated in addition to soluble guanylate cyclase (sGC) activities in these cells. Findings that cyclic GMP formation was preferentially activated by CNP but not by the related peptide, ANP, were consistent with RT-PCR analyses, demonstrating gene expression of the CNP receptor, GC-B, but not of the ANP receptor, GC-A, in these cells. Prior exposure of the cells to 10(-8) M PACAP resulted in a marked down-regulation of GC-B activity, whereas sGC was not affected. These findings provide functional and molecular evidence for the presence of three receptors, PAC(1), VPAC(2) and GC-B, involved in cyclic nucleotide signalling in penile CCSM cells. The observed cross-talk of the PACAP/VIP receptors with GC-B but not with sGC may have implications for the therapy of erectile dysfunction. 相似文献
998.
Trejo-Tapia Gabriela Maldonado Amaya Uriel Salcedo Morales Guadalupe De Jesús Sánchez Antonia Martínez Bonfil Blanca Rodríguez-Monroy Mario Jiménez-Aparicio Antonio 《Plant Cell, Tissue and Organ Culture》2002,71(1):41-46
The effects of a cold pretreatment, the concentration of different auxins (2,4-D, NAA and IAA) and the type of carbon source (maltose and sucrose) on the induction of callus from anthers of three parental lines and four rice F1 hybrids (Japonica × Indica, Indica × Japonica) were studied. The results indicated that a cold pretreatment was essential for the induction of callus from anthers of the parental lines and the F1 hybrids. These effects were genotype dependent. Auxins were essential for the induction of callus, and the type and concentration of auxins also influenced this process, as well as the type of carbon source. The greatest induction of callus was by the hybrid Morelos A92 × Koshihikari after a cold pretreatment of 8 days using 10.74 M –napthaleneacetic acid and 30 g l–1 maltose. 相似文献
999.
Rubel C Fernández GC Rosa FA Gómez S Bompadre MB Coso OA Isturiz MA Palermo MS 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(7):3527-3535
The integrin family not only mediates the recruitment of polymorphonuclear leukocytes (PMN) to sites of inflammation but also regulates several effector functions by binding to specific ligands. We have recently demonstrated that soluble fibrinogen (sFbg) is able to trigger an activating signal in PMN through an integrin-dependent mechanism. This activation results in degranulation, phagocytosis enhancement, and apoptosis delay. The aim of the present work was to further elucidate the molecular events that follow sFbg interaction with CD11b in human PMN, and the participation of this signaling pathway in the regulation of neutrophil functionality. We demonstrate that sFbg triggers a cascade of intracellular signals that lead to focal adhesion kinase and extracellular signal-regulated kinase 1/2 tyrosine phosphorylation. The activation of this mitogen-activated protein kinase pathway plays a central role in the sFbg modulation of secondary granule degranulation, Ab-dependent phagocytosis, and apoptosis. However, fibrinogen-induced secretory vesicle degranulation occurs independently of the signaling transduction pathways investigated herein. In the context of an inflammatory process, the intracellular signal pathway activated by sFbg may be an early event influencing the functionality of PMN. 相似文献
1000.
Mwangi W Brown WC Lewin HA Howard CJ Hope JC Baszler TV Caplazi P Abbott J Palmer GH 《Journal of immunology (Baltimore, Md. : 1950)》2002,169(7):3837-3846
DNA-based immunization is a contemporary strategy for developing vaccines to prevent infectious diseases in animals and humans. Translating the efficacy of DNA immunization demonstrated in murine models to the animal species that represent the actual populations to be protected remains a significant challenge. We tested two hypotheses directed at enhancing DNA vaccine efficacy in outbred animals. The first hypothesis, that DNA-encoding fetal liver tyrosine kinase 3 ligand (Flt3L) and GM-CSF increases dendritic cell (DC) recruitment to the immunization site, was tested by intradermal inoculation of calves with plasmid DNA encoding Flt3L and GM-CSF followed by quantitation of CD1(+) DC. Peak DC recruitment was detected at 10-15 days postinoculation and was significantly greater (p < 0.05) in calves in the treatment group as compared with control calves inoculated identically, but without Flt3L and GM-CSF. The second hypothesis, that DNA encoding Flt3L and GM-CSF enhances immunity to a DNA vector-expressed Ag, was tested by analyzing the CD4(+) T lymphocyte response to Anaplasma marginale major surface protein 1a (MSP1a). Calves immunized with DNA-expressing MSP1a developed strong CD4(+) T cell responses against A. marginale, MSP1a, and specific MHC class II DR-restricted MSP1a epitopes. Administration of DNA-encoding Flt3L and GM-CSF before MSP1a DNA vaccination significantly increased the population of Ag-specific effector/memory cells in PBMC and significantly enhanced MSP1a-specific CD4(+) T cell proliferation and IFN-gamma secretion as compared with MHC class II DR-matched calves vaccinated identically but without Flt3L and GM-CSF. These results support use of these growth factors in DNA vaccination and specifically indicate their applicability for vaccine testing in outbred animals. 相似文献