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101.
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103.
Antiretroviral protease inhibitors are a class of important drugs that are used for the treatment of human immunodeficiency virus infections. Among those compounds, ritonavir is applied frequently in combination with other antiretroviral protease inhibitors, as it has been reported to boost their therapeutic efficiency. To test whether ritonavir affects the viability and the glutathione (GSH) metabolism of brain cells, we have exposed primary astrocyte cultures to this protease inhibitor. Application of ritonavir in low micromolar concentrations did not compromise cell viability, but caused a time- and concentration-dependent loss of GSH from the cells which was accompanied by a matching increase in the extracellular GSH content. Half-maximal effects were observed for ritonavir in a concentration of 3 μM. The ritonavir-induced stimulated GSH export from astrocytes was completely prevented by MK571, an inhibitor of the multidrug resistance protein 1. In addition, continuous presence of ritonavir was essential to maintain the stimulated GSH export, since removal of ritonavir terminated the stimulated GSH export. Ritonavir was more potent to stimulate GSH export from astrocytes than the antiretroviral protease inhibitors indinavir and nelfinavir, but combinations of ritonavir with indinavir or nelfinavir did not further stimulate astrocytic GSH export compared to a treatment with ritonavir alone. The strong effects of ritonavir and other antiretroviral protease inhibitors on the GSH metabolism of astrocytes suggest that a chronic treatment of patients with such compounds may affect their brain GSH metabolism. 相似文献
104.
Arsenate is known to be accumulated by cultured astrocytes and to stimulate astrocytic glutathione export, but the arsenate uptake into astrocytes has not been characterized so far. To address this topic, we have exposed primary rat astrocyte cultures to arsenate and determined the cellular arsenic content by atomic absorption spectroscopy. Viable astrocytes accumulated arsenate in a time- and concentration-dependent manner. Their cellular arsenic content increased almost proportional with time for up to 60 min after application of arsenate. Analysis of the concentration-dependent increase in the specific arsenic content of the cells after 30 min of arsenate exposure revealed that cultured astrocytes take up arsenate with saturable kinetics by a transport process that has apparent KM- and Vmax-values of 1.7 ± 0.2 mM and 28 ± 4 nmol/(mg protein × 30 min), respectively. Arsenate uptake in viable astrocytes was strongly inhibited by the presence of phosphate or by lowering the incubation temperature to 4 °C and was completely abolished in a sodium ion-free medium. These results strongly suggest that the saturable temperature-dependent arsenate uptake into astrocytes is mediated by a sodium-dependent phosphate cotransporter. 相似文献
105.
Kathleen B?rner Dominik Niopek Gabriella Cotugno Michaela Kaldenbach Teresa Pankert Joschka Willemsen Xian Zhang Nina Schürmann Stefan Mockenhaupt Andrius Serva Marie-Sophie Hiet Ellen Wiedtke Mirco Castoldi Vytaute Starkuviene Holger Erfle Daniel F. Gilbert Ralf Bartenschlager Michael Boutros Marco Binder Konrad Streetz Hans-Georg Kr?usslich Dirk Grimm 《Nucleic acids research》2013,41(21):e199
As the only mammalian Argonaute protein capable of directly cleaving mRNAs in a small RNA-guided manner, Argonaute-2 (Ago2) is a keyplayer in RNA interference (RNAi) silencing via small interfering (si) or short hairpin (sh) RNAs. It is also a rate-limiting factor whose saturation by si/shRNAs limits RNAi efficiency and causes numerous adverse side effects. Here, we report a set of versatile tools and widely applicable strategies for transient or stable Ago2 co-expression, which overcome these concerns. Specifically, we engineered plasmids and viral vectors to co-encode a codon-optimized human Ago2 cDNA along with custom shRNAs. Furthermore, we stably integrated this Ago2 cDNA into a panel of standard human cell lines via plasmid transfection or lentiviral transduction. Using various endo- or exogenous targets, we demonstrate the potential of all three strategies to boost mRNA silencing efficiencies in cell culture by up to 10-fold, and to facilitate combinatorial knockdowns. Importantly, these robust improvements were reflected by augmented RNAi phenotypes and accompanied by reduced off-targeting effects. We moreover show that Ago2/shRNA-co-encoding vectors can enhance and prolong transgene silencing in livers of adult mice, while concurrently alleviating hepatotoxicity. Our customizable reagents and avenues should broadly improve future in vitro and in vivo RNAi experiments in mammalian systems. 相似文献
106.
Meng-Han Lin Hao-Jen Hsu Ralf Bartenschlager 《Journal of biomolecular structure & dynamics》2013,31(10):1552-1562
Nonstructural protein 4A (NS4A) of Dengue virus (DENV) is a membrane protein involved in rearrangements of the endoplasmic reticulum membrane that are required for formation of replication vesicles. NS4A is composed most likely of three membrane domains. The N- and C-terminal domains are supposed to traverse the lipid membrane whereas the central one is thought to reside on the membrane surface, thus forming a u-shaped protein. All three membrane domains are proposed to be helical by secondary structure prediction programs. After performing multi nanosecond molecular dynamics (MD) simulations at various temperatures (300, 310, and 315.15?K) with each of the individual domains, they are used in a docking approach to define putative association motifs of the transmembrane domains (TMDs). Two structures of the u-shaped protein are generated by separating two assembled TMDs linking them with the membrane-attached domain. Lipid undulation is monitored with the structures embedded in a fully hydrated lipid bilayer applying multiple 200?ns MD simulations at 310?K. An intact structure of the protein supports membrane undulation. The strong unwinding of the helices in the domain-linking section of one of the structures lowers its capability to induce membrane curvature. Unwinding of the link region is due to interactions of two tryptophan residues, Trp-96 and 104. These results provide first insights into the membrane-altering properties of DENV NS4A. 相似文献
107.
Root growth in biopores—evaluation with in situ endoscopy 总被引:1,自引:0,他引:1
Background and aims
The significance of biopores for nutrient acquisition from the subsoil depends on root-soil contact, which in turn is influenced by root architecture. The aim of this study was to detect differences regarding the architecture and root-soil contact of homorhizous barley roots (Hordeum vulgare L.) and allorhizous oilseed rape roots (Brassica napus L.) growing in biopores.Methods
In situ endoscopy was used as a technique that allows non-destructive display of pore wall characteristics and root morphology inside large biopores under field conditions.Results
For both crops, about 85 % of all roots did establish contact to the pore wall. However, according to their different root architecture, the two crops varied in their strategy of resource acquisition: While barley was characterized by thin vertical or ingrowing roots, most of them in direct contact to the pore wall, oilseed rape established contact to the pore wall predominantly via lateral roots.Conclusions
Root morphological and pore wall assessment with in situ endoscopy in combination with detailed studies of soil biochemical and soil physical parameters of the pore wall is considered an essential prerequisite for more precise future modelling of nutrient acquisition and uptake. 相似文献108.
Erik J. Ragsdale Natsumi Kanzaki Waltraud Röseler Matthias Herrmann Ralf J. Sommer 《Zoological Journal of the Linnean Society》2013,168(4):671-698
Developmental plasticity is often correlated with diversity and has been proposed as a facilitator of phenotypic novelty. Yet how a dimorphism arises or how additional morphs are added is not understood, and few systems provide experimental insight into the evolution of polyphenisms. Because plasticity correlates with structural diversity in Pristionchus nematodes, studies in this group can test the role of plasticity in facilitating novelty. Here, we describe three new species, Pristionchus fukushimae sp. nov. , Pristionchus hoplostomus sp. nov. , and the hermaphroditic Pristionchus triformis sp. nov. , which are characterized by a novel polymorphism in their mouthparts. In addition to showing the canonical mouth dimorphism of diplogastrid nematodes, comprising a stenostomatous (‘narrow‐mouthed’) and a eurystomatous (‘wide‐mouthed’) form, the new species exhibit forms with six, 12, or intermediate numbers of cheilostomatal plates. Correlated with this polymorphism is another trait that varies among species: whereas divisions between plates are complete in P. triformis sp. nov. , which is biased towards a novel ‘megastomatous’ form comprising 12 complete plates, the homologous divisions in the other new species are partial and of variable length. In a reconstruction of character evolution, a phylogeny inferred from 26 ribosomal protein genes and a partial small subunit rRNA gene supported the megastomatous form of P. triformis sp. nov. as the derived end of a series of split‐plate forms. Although split‐plate forms were normally only observed in eurystomatous nematodes, a single 12‐plated stenostomatous individual of P. hoplostomus sp. nov. was also observed, suggesting independence of the two types of mouth plasticity. By introducing these new species to the Pristionchus model system, this study provides further insight into the evolution of polymorphisms and their evolutionary intermediates. © 2013 The Linnean Society of London 相似文献
109.
Formaldehyde is endogenously produced in the human body and brain levels of this compound are elevated in neurodegenerative conditions. Although the toxic potential of an excess of formaldehyde has been studied, little is known on the molecular mechanisms underlying its neurotoxicity as well as on the ability of neurons to metabolize formaldehyde. To address these topics, we have used cerebellar granule neuron cultures as model system. These cultures express mRNAs of various enzymes that are involved in formaldehyde metabolism and were remarkably resistant toward acute formaldehyde toxicity. Cerebellar granule neurons metabolized formaldehyde with a rate of around 200 nmol/(h × mg) which was accompanied by significant increases in the cellular and extracellular concentrations of formate. In addition, formaldehyde application significantly increased glucose consumption, almost doubled the rate of lactate release from viable neurons and strongly accelerated the export of the antioxidant glutathione. The latter process was completely prevented by inhibition of the known glutathione exporter multidrug resistance protein 1. These data indicate that cerebellar granule neurons are capable of metabolizing formaldehyde and that the neuronal glycolysis and glutathione export are severely affected by the presence of formaldehyde. 相似文献