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61.
62.
Tunaz H Bedick JC Miller JS Hoback WW Rana RL Stanley DW 《Journal of insect physiology》1999,45(10):923-931
Nodulation is the first and quantitatively most important cellular defense reaction to bacterial infections in insects. Treating adults of the 17-year periodical cicadas, Magicicada septendecim and M. cassini, with eicosanoid biosynthesis inhibitors immediately prior to intrahemocoelic injections of the bacterium, Serratia marcescens, sharply reduced the nodulation response to bacterial challenges. Separate treatments with specific inhibitors of phospholipase A(2), cyclooxygenase, and lipoxygenase reduced nodulation, supporting our view that nodule formation is a multi-step process in which individual steps are separately mediated by lipoxygenase and cyclooxygenase products. The inhibitory influence of dexamethasone was apparent by 2 h after injection, and nodulation was significantly reduced, relative to control insects, over the following 14 h. The dexamethasone effects were reversed by treating bacteria-challenged insects with the eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. Low levels of arachidonic acid were detected in fat body phospholipids. These findings in adults of an exopterygote insect species with an unusual life history pattern broaden our hypothesis that eicosanoids mediate cellular immune reactions to bacterial infections in most, if not all, insects. 相似文献
63.
Nodulation is the temporally and quantitatively most important cellular defense reaction to bacterial infections in insects. Inhibition of eicosanoid biosynthesis in adults of the cricket, Gryllus assimilis, immediately prior to intrahemocoelic injections of the bacterium, Serratia marcescens, sharply reduced the nodulation response. Separate treatments with specific inhibitors of phospholipase A(2), cyclooxygenase, and lipoxygenase reduced nodulation, supporting our view that nodule formation is a complex process involving lipoxygenase and cyclooxygenase products. The inhibitory influence of dexamethasone was apparent within 2h of injection, and nodulation was significantly reduced, relative to control crickets, over 22h. The dexamethasone effects were reversed by treating bacteria-injected insects with the eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. Low levels of arachidonic acid were detected in fat body phospholipids, and fat body preparations were shown to be competent to biosynthesize eicosanoids from exogenous radioactive arachidonic acid. These findings in a hemimetabolous insect broaden our hypothesis that eicosanoids mediate cellular immune reactions to bacterial infections in most, if not all, insects. 相似文献
64.
65.
Spady TJ Shayya R Thackray VG Ehrensberger L Bailey JS Mellon PL 《Molecular endocrinology (Baltimore, Md.)》2004,18(4):925-940
Little is known about the molecular mechanisms of androgen regulation of the FSHbeta gene; however, studies suggest that it consists of a complex feedback loop that involves multiple mechanisms acting at both the level of the hypothalamus and the pituitary. In the present study, we address androgen regulation of the FSHbeta gene in immortalized gonadotrope cells and investigate the roles of activin and GnRH in androgen action. Using transient transfection assays in the FSHbeta-expressing mouse gonadotrope cell line, LbetaT2, we demonstrate that androgens stimulate expression of an ovine FSHbeta reporter gene in a dose-dependent manner. Mutation of either of two conserved androgen response elements at -245/-231 and -153/-139 within the proximal region of the ovine FSHbeta gene promoter abolishes this stimulation, and androgen receptor binds directly to the -244 ARE in vitro. Androgen induction of the FSHbeta reporter gene is also dependent upon the activin autocrine loop present in the LbetaT2 cells, as well as an activin-response element at -138/-124 of the FSHbeta gene. However, activin regulation of other genes remains unaffected by androgens. In addition, androgens stimulate expression of a mouse GnRH receptor reporter gene, and thus may indirectly augment the response of the FSHbeta gene to GnRH. Taken together, these data demonstrate that, in mouse gonadotropes, androgens act directly on the ovine FSHbeta gene to stimulate expression by a mechanism that is dependent upon activin, as well as acting indirectly, potentially through a second mechanism that may be dependent upon induction of GnRH receptor. 相似文献
66.
The biochemical toxicity of arsenic trioxide (AsIII) in a freshwater edible fish Channa punctatus has been studied on exposures ranging from 7 to 90 d. The arsenic concentration increased exponentially in liver, kidney,
gills, and muscles of fish up to 60 d of exposure to arsenic. However, arsenic concentration in these tissues declined at
90 d of exposure. This relationship between period of exposure and concentration of arsenic in selected tissues suggests an
adaptive response of fish to arsenic. Furthermore, exposure to arsenic-induced lipid peroxidation in these organs increased
initially at 7 d of exposure; however, it decreased up to 60 d of exposure but increased again at 90 d of treatment. Values
of reduced glutathione (GSH) reflected the observations of lipid peroxidation. The role of GSH in this adaptive response has
been discussed. 相似文献
67.
Hermjakob H Montecchi-Palazzi L Bader G Wojcik J Salwinski L Ceol A Moore S Orchard S Sarkans U von Mering C Roechert B Poux S Jung E Mersch H Kersey P Lappe M Li Y Zeng R Rana D Nikolski M Husi H Brun C Shanker K Grant SG Sander C Bork P Zhu W Pandey A Brazma A Jacq B Vidal M Sherman D Legrain P Cesareni G Xenarios I Eisenberg D Steipe B Hogue C Apweiler R 《Nature biotechnology》2004,22(2):177-183
68.
Yueh-Hsin Ping Chia-ying Chu Hong Cao Jean-Marc Jacque Mario Stevenson Tariq M Rana 《Retrovirology》2004,1(1):1-13
Background
Dendritic cell (DC) transmission of human immunodeficiency virus (HIV) to CD4+ T cells occurs across a point of cell-cell contact referred to as the infectious synapse. The relationship between the infectious synapse and the classically defined immunological synapse is not currently understood. We have recently demonstrated that human B cells expressing exogenous DC-SIGN, DC-specific intercellular adhesion molecule-3 (ICAM-3)-grabbing nonintegrin, efficiently transmit captured HIV type 1 (HIV-1) to CD4+ T cells. K562, another human cell line of hematopoietic origin that has been extensively used in functional analyses of DC-SIGN and related molecules, lacks the principal molecules involved in the formation of immunological synaptic junctions, namely major histocompatibility complex (MHC) class II molecules and leukocyte function-associated antigen-1 (LFA-1). We thus examined whether K562 erythroleukemic cells could recapitulate efficient DC-SIGN-mediated HIV-1 transmission (DMHT).Results
Here we demonstrate that DMHT requires cell-cell contact. Despite similar expression of functional DC-SIGN, K562/DC-SIGN cells were inefficient in the transmission of HIV-1 to CD4+ T cells when compared with Raji/DC-SIGN cells. Expression of MHC class II molecules or LFA-1 on K562/DC-SIGN cells was insufficient to rescue HIV-1 transmission efficiency. Strikingly, we observed that co-culture of K562 cells with Raji/DC-SIGN cells impaired DMHT to CD4+ T cells. The K562 cell inhibition of transmission was not directly exerted on the CD4+ T cell targets and required contact between K562 and Raji/DC-SIGN cells.Conclusions
DMHT is cell type dependent and requires cell-cell contact. We also find that the cellular milieu can negatively regulate DC-SIGN transmission of HIV-1 in trans. 相似文献69.
The polyethylene glycol (PEG) treatment of ciprofloxacin-Indion 234 complex was aimed to retard rapid ion exchange drug release
at gastric pH. Ciprofloxacin loading on Indion 234 was performed in a batch process, and the amount of K+ in Indion 234 displaced by drug with time was studied as equilibrium constant KDM. Drug-resin complex (DRC) was treated with aqueous PEG solution (0.5%–2% wt/vol) of different molecular weights (MWs) for
2 to 30 minutes. The PEG-treated ciprofloxacin-Indion 234 complex was evaluated for particle size, water absorption time,
and drug release at gastric pH. During drug loading on Indion 234, the equilibrium constant (KDM) increased rapidly up to 20 minutes with efficient drug loading. Increased time of immersion of the drug resinate in PEG
solutions significantly retained higher size particles upon dehydration. The larger DRC particles showed longer water absorption
times owing to compromised hydrating power. The untreated DRC showed insignificant drug release in deionized water; while
at gastric pH, ciprofloxacin release was complete in 90 minutes. A trend of increased residual particle size, proportionate
increase in water absorption time, and hence the retardation of release with time of immersion was evident in PEG-treated
DRC. The time of immersion of DRC in PEG-treated DRC. The time of immersion of DRC in PEG solution had predominant release
retardant effect, while the effect of molecular weight of PEG was insignificant. Thus, PEG treatment of DRC successfully retards
ciprofloxacin ion exchange release in acidic pH. 相似文献
70.
A continuous coupled enzyme assay for bacterial malonyl-CoA:acyl carrier protein transacylase (FabD)
Bacterial malonyl-CoA:acyl carrier protein transacylase catalyzes the transfer of a malonyl moiety from malonyl-CoA to the free thiol group of the phosphopantetheine arm of acyl carrier protein. Malonyl-ACP, the product of this enzymatic reaction, is the key building block for de novo fatty acid biosynthesis. Here, we describe a continuous enzyme assay based on the coupling of the malonyl-CoA:acyl carrier protein transacylase reaction to alpha-ketoglutarate dehydrogenase (KDH). KDH-dependent consumption of the coenzyme A generated by malonyl-CoA:acyl carrier protein transacylase is accompanied by a reduction of nicotinamide adenine dinucleotide, oxidized (NAD(+)) to nicotinamide adenine dinucleotide, reduced. The rate of NAD(+) reduction is continuously monitored as a change in fluorescence using a microtiter plate reader. We show that this coupled enzyme assay is amenable to routine chemical compound screening. 相似文献