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101.
S-adenosyl-L-homocysteine hydrolase is necessary for aldosterone-induced activity of epithelial Na(+) channels 总被引:1,自引:0,他引:1
Stockand JD Zeltwanger S Bao HF Becchetti A Worrell RT Eaton DC 《American journal of physiology. Cell physiology》2001,281(3):C773-C785
The A6 cell line was used to study the role ofS-adenosyl-L-homocysteine hydrolase (SAHHase) inthe aldosterone-induced activation of the epithelial Na+channel (ENaC). Because aldosterone increases methylation of severaldifferent molecules, and because this methylation is associated withincreased Na+ reabsorption, we tested the hypothesis thataldosterone increases the expression and activity of SAHHase protein.The rationale for this work is that general methylation may be promotedby activation of SAHHase, the only enzyme known to metabolize SAH, apotent end-product inhibitor of methylation. Although aldosteroneincreased SAHHase activity, steroid did not affect SAHHase expression.Antisense SAHHase oligonucleotide decreased SAHHaseexpression and activity. Moreover, this oligonucleotide, as well as apharmacological inhibitor of SAHHase, decreased aldosterone-inducedactivity of ENaC via a decrease in ENaC open probability. The kineticsof ENaC in cells treated with antisense plus aldosterone were similarto those reported previously for the channel in the absence of steroid. This is the first report showing that active SAHHase, in part, increases ENaC open probability by reducing the transition rate fromopen states in response to aldosterone. Thus aldosterone-induced SAHHase activity plays a critical role in shifting ENaC from a gatingmode with short open and closed times to one with longer open andclosed times. 相似文献
102.
Crane MS Hardy-Smith P Williams LM Hyatt AD Eaton LM Gould A Handlinger J Kattenbelt J Gudkovs N 《Diseases of aquatic organisms》2000,43(1):1-14
During routine sampling and testing, as part of a systematic surveillance program (the Tasmanian Salmonid Health Surveillance Program), an aquatic birnavirus was isolated from 'pin-head' (fish exhibiting deficient acclimatisation on transfer to saltwater) Atlantic salmon Salmo salar, approximately 18 mo old, farmed in net-pens located in Macquarie Harbour on the west coast of Tasmania, Australia. The isolate grows readily in a range of fish cell lines including CHSE-214, RTG-2 and BF-2 and is neutralised by a pan-specific rabbit antiserum raised against infectious pancreatic necrosis virus (IPNV) Ab strain and by a commercial pan-specific IPNV-neutralising monoclonal antibody. Presence of the virus was not associated with gross clinical signs. Histopathological examination revealed a range of lesions particularly in pancreatic tissue. The virus was localised in pancreas sections by immunoperoxidase staining using the polyclonal antiserum and by electron microscopy. Examination by electron microscopy demonstrated that the virus isolated in cell culture (1) belongs to the family Birnaviridae, genus Aquabirnaviridae; (2) was ultrastructurally and antigenically similar to virus identified in the index fish; (3) is related to IPNV. Western blot analysis using the polyclonal rabbit antiserum confirmed the cross-reactions between various aquatic birnavirus isolates. In addition, PCR analysis of isolated viral nucleic acid from the index case indicated that the virus is more closely related to IPNV fr21 and N1 isolates than to other birnavirus isolates available for comparison. Sampling of other fish species within Macquarie Harbour has demonstrated that the virus is present in several other species of fish including farmed rainbow trout Oncorhynchus mykiss, wild flounder Rhombosolea tapirina, cod Pseudophycis sp., spiked dogfish Squalus megalops and ling Genypterus blacodes. 相似文献
103.
Eaton RJ Baranovskiĭ DA Veselkov DA Osetrov SG Bolotin PA Dymant LN Pakhomov VI Davis DV Veselkov AN 《Biofizika》2000,45(4):586-599
The complex formation of the antibiotic daunomycin with deoxytetranucleotides of different base sequence in the chain, 5'-d(GpCpGpC), 5'-d(CpGpCpG), and 5'-d(TpGpCpA) in aqueous salt solution was studied by 1D and 2D (2M-TOCSY and 2M-NOESY) 1H-NMR spectroscopy. Concentration and temperature dependences of proton chemical shifts of molecules were measured. Based on these dependences, reaction equilibrium constants, relative content of various complexes depending on concentration and temperature, limiting values of chemical shifts of protons of daunomycin incorporated in various complexes, and the thermodynamic parameters delta H and delta S of complex formation were calculated. The analysis of the results enables the conclusion that the sites of predominant intercalation of daunomycin are triplet nucleotide sequences, the binding sites of the antibiotic with three consecutive GC pairs in the tetranucleotide duplex being more preferential. Daunomycin exhibits no sequence specificity upon binding to the single-stranded deoxynucleotide sequence. From the calculated values of induced chemical shifts of daunomycin protons and 2M-NOE data, the most probable spatial structures of complexes (1:2) of the antibiotic with deoxytetranucleotides were constructed. The binding of the second daunomycin molecule to both the single-stranded and duplex form of tetramers is of pronounced anticooperative mode, which is explained by the presence in the antibiotic of a positively charged amino sugar residue, which poses considerable steric constraints for the insertion of the second antibiotic molecule into the short tetranucleotide sequence. The results were compared with the data obtained under identical experimental conditions for typical intercalators proflavine and ethidium bromide. 相似文献
104.
Syntheses of two analogs of deoxyuridine with N,N-dialkylaniline chromophores are reported. 5-[3-(N-methylphenylamino)propanoyl]-2'-deoxyuridine (1) and 5-[2-(4-N,N-dimethylaminophenyl)ethyl)]-2'-deoxyuridine (2) are prepared by palladium-mediated coupling. Preparation of 2 was facilitated by in situ transient O4-trimethylsilyl protection during alkynylation which suppressed secondary cyclization of the coupling adduct. 相似文献
105.
The effect of rapamycin on single ENaC channel activity and phosphorylation in A6 cells 总被引:1,自引:0,他引:1
Yue G Edinger RS Bao HF Johnson JP Eaton DC 《American journal of physiology. Cell physiology》2000,279(1):C81-C88
Rapamycin and FK-506 are immunosuppressive drugs thatbind a ubiquitous immunophilin, FKBP12, but immunosuppressivemechanisms and side effects appear to be different. Rapamycin bindsrenal FKBP12 to change renal transport. We used cell-attached patch clamp to examine rapamycin's effect on Na+ channels in A6cells. Channel NPo was 0.5 ± 0.08 (n = 6)during the first 5 min but fell close to zero after 20 min. Application of 1 µM rapamycin reactivated Na+ channels(NPo = 0.47 ± 0.1; n=6), but 1 µMFK-506 did not. Also, GF-109203X, a protein kinase C (PKC) inhibitor,mimicked the rapamycin-induced reactivation in a nonadditive manner.However, rapamycin did not reactivate Na+ channels if cellswere exposed to 1 µM FK-506 before rapamycin. In PKC assays,rapamycin was as effective as the PKC inhibitor; however, epithelialNa+ channel (ENaC) phosphorylation was low under baselineconditions and was not altered by PKC inhibitors or activators. Theseresults suggest that rapamycin activates Na+ channels bybinding FKBP12 and inhibiting PKC, and, in renal cells, despite bindingthe same immunophilin, rapamycin and FK-506 activate differentintracellular signaling pathways. 相似文献
106.
Do submerged aquatic plants influence periphyton community composition for the benefit of invertebrate mutualists? 总被引:7,自引:0,他引:7
- 1 It has been suggested that submerged aquatic plants can influence the periphyton which grows on their surfaces, making it nutritionally beneficial to snails. In return, preferential feeding by snails clears the plants from a potential competitor, with both plants and grazers gaining from this mutualistic relationship.
- 2 A highly replicated experiment was conducted, in which the nature of the plant (isoetid and elodeid types compared with similar shaped inert substrata), the nutrient availability (10–200 µg L‐1 P, 0.2–4 mg L‐1 N) and the influence of periphyton grazers, Physa fontinalis, were controlled. The plants were cleaned of periphyton before use and an algal inoculum added to all treatments. At the end of the growth period, quantitative measures of the periphyton community composition were made and related to the treatments using both ordination and analysis of variance.
- 3 Grazing had the largest influence on community composition and algal numbers. A community of unicellular and adpressed filamentous forms developed in the presence of snails, and of erect filamentous forms in their absence. Three algal species, Cocconeis placentula, Chamaesiphon incrustans and Aphanochaete repens, increased in real numbers in the presence of snails, probably as a result of reduced competition whilst being able to withstand grazing.
- 4 The second largest effect was the influence of host plant. However, differences between the two artificial plants were as great as between the real plants and their artificial counterparts, indicating that physical structure was as important as any active contribution by the plants. Nutrients had a small but significant effect on community composition, but not all species responded in the same way to nutrient enrichment.
- 5 Although submerged aquatic plants exert an influence over the community composition of the periphyton which develops on their surfaces, it is unlikely that they manipulate it to make it more attractive to grazers such as snails.
107.
Guiang SF Merchant JR Eaton MA Fandel KB Georgieff MK 《Canadian journal of physiology and pharmacology》1998,76(9):930-936
Myocardial iron deficiency complicates chronic intrauterine hypoxemia during diabetic pregnancies. To understand the effect of both conditions during fetal life on intracardiac iron prioritization, we measured heart myoglobin, cytochrome c, and elemental iron concentrations in six iron-deficient, hypoxic, five iron-sufficient, hypoxic, six iron-deficient, normoxic, and six iron-sufficient, normoxic newborn guinea pigs. The iron-deficient, hypoxic group had lower heart iron (p = 0.03) but higher myoglobin concentration (p < 0.0001) when compared with the iron-sufficient, normoxic group. The percentage of iron incorporated into myoglobin was higher than control in the iron-deficient, hypoxic group (23.2+/-7.2% vs. 5.2+/-0.8%; p < 0.001) and increased as total heart iron decreased (r = 0.97; p < 0.001). In contrast, heart cytochrome c concentration was lower than control in the iron-deficient, hypoxic group (p = 0.01), with equal percentages of heart iron incorporated into cytochrome c. This intracellular prioritization of myocardial iron to myoglobin and away from cytochrome c following combined fetal hypoxemia and iron deficiency may represent an adaptive mechanism to preserve myocardial tissue oxygenation, although at the expense of oxidative phosphorylative capability. 相似文献
108.
Interest in the use of low-copy nuclear genes for phylogenetic analyses of
plants has grown rapidly, because highly repetitive genes such as those
commonly used are limited in number. Furthermore, because low- copy genes
are subject to different evolutionary processes than are plastid genes or
highly repetitive nuclear markers, they provide a valuable source of
independent phylogenetic evidence. The gene for granule-bound starch
synthase (GBSSI or waxy) exists in a single copy in nearly all plants
examined so far. Our study of GBSSI had three parts: (1) Amino acid
sequences were compared across a broad taxonomic range, including grasses,
four dicotyledons, and the microbial homologs of GBSSI. Inferred structural
information was used to aid in the alignment of these very divergent
sequences. The informed alignments highlight amino acids that are conserved
across all sequences, and demonstrate that structural motifs can be highly
conserved in spite of marked divergence in amino acid sequence. (2)
Maximum-likelihood (ML) analyses were used to examine exon sequence
evolution throughout grasses. Differences in probabilities among
substitution types and marked among-site rate variation contributed to the
observed pattern of variation. Of the parameters examined in our set of
likelihood models, the inclusion of among-site rate variation following a
gamma distribution caused the greatest improvement in likelihood score. (3)
We performed cladistic parsimony analyses of GBSSI sequences throughout
grasses, within tribes, and within genera to examine the phylogenetic
utility of the gene. Introns provide useful information among very closely
related species, but quickly become difficult to align among more divergent
taxa. Exons are variable enough to provide extensive resolution within the
family, but with low bootstrap support. The combined results of amino acid
sequence comparisons, maximum-likelihood analyses, and phylogenetic studies
underscore factors that might affect phylogenetic reconstruction. In this
case, accommodation of the variable rate of evolution among sites might be
the first step in maximizing the phylogenetic utility of GBSSI.
相似文献
109.
Viktória Jeney Edina Komódi Emőke Nagy Abolfazl Zarjou Gregory M. Vercellotti John W. Eaton György Balla József Balla 《Free radical biology & medicine》2009,46(5):616-623
Heme-mediated oxidative modification of low-density lipoprotein (LDL) plays a crucial role in early atherogenesis. It has been shown that hydrogen sulfide (H2S) produced by vascular smooth muscle cells is present in plasma at a concentration of about 50 µmol/L. H2S is a strong reductant which can react with reactive oxygen species like superoxide anion and hydrogen peroxide. The current study investigated the effect of H2S on hemin-mediated oxidation of LDL and oxidized LDL (oxLDL)-induced endothelial reactions. H2S dose dependently delayed the accumulation of lipid peroxidation products—conjugated dienes, lipid hydroperoxides (LOOH), and thiobarbituric acid reactive substances—during hemin-mediated oxidation. Moreover, H2S decreased the LOOH content of both oxidized LDL and lipid extracts derived from soft atherosclerotic plaque, which was accompanied by reduced cytotoxicity. OxLDL-mediated induction of the oxidative stress responsive gene, heme oxygenase-1, was also abolished by H2S. Finally we have shown that H2S can directly protect endothelium against hydrogen peroxide and oxLDL-mediated endothelial cytotoxicity. These results demonstrate novel functions of H2S in preventing hemin-mediated oxidative modification of LDL, and consequent deleterious effects, suggesting a possible antiatherogenic action of H2S. 相似文献
110.
Joshua?C.?Snyder Thomas?F.?Pack Lauren?K.?Rochelle Subhasish?K.?Chakraborty Ming?Zhang Andrew?W.?Eaton Yushi?Bai Lauren?A.?Ernst Larry?S.?Barak Alan?S.?Waggoner Marc?G.?CaronEmail author 《BMC biology》2015,13(1):107