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51.
52.
Kohlhaas CF Morrow VA Jhakra N Patil V Connell JM Petrie JR Salt IP 《Biochemical and biophysical research communications》2011,412(4):747-751
Insulin stimulates endothelial NO synthesis, at least in part mediated by phosphorylation and activation of endothelial NO synthase at Ser1177 and Ser615 by Akt. We have previously demonstrated that insulin-stimulated NO synthesis is inhibited under high culture glucose conditions, without altering Ca(2+)-stimulated NO synthesis or insulin-stimulated phosphorylation of eNOS. This indicates that stimulation of endothelial NO synthase phosphorylation may be required, yet not sufficient, for insulin-stimulated nitric oxide synthesis. In the current study we investigated the role of supply of the eNOS substrate, L-arginine as a candidate parallel mechanism underlying insulin-stimulated NO synthesis in cultured human aortic endothelial cells. Insulin rapidly stimulated L-arginine transport, an effect abrogated by incubation with inhibitors of phosphatidylinositol-3'-kinase or infection with adenoviruses expressing a dominant negative mutant Akt. Furthermore, supplementation of endothelial cells with extracellular L-arginine enhanced insulin-stimulated NO synthesis, an effect reversed by co-incubation with the L-arginine transport inhibitor, L-lysine. Basal L-arginine transport was significantly increased under high glucose culture conditions, yet insulin-stimulated L-arginine transport remained unaltered. The increase in L-arginine transport elicited by high glucose was independent of the expression of the cationic amino acid transporters, hCAT1 and hCAT2 and not associated with any changes in the activity of ERK1/2, Akt or protein kinase C (PKC). We propose that rapid stimulation of L-arginine transport contributes to insulin-stimulated NO synthesis in human endothelial cells, yet attenuation of this is unlikely to underlie the inhibition of insulin-stimulated NO synthesis under high glucose conditions. 相似文献
53.
Kubo A Stull R Takeuchi M Bonham K Gouon-Evans V Sho M Iwano M Saito Y Keller G Snodgrass R 《PloS one》2011,6(9):e24058
In order to define the molecular mechanisms regulating the specification and differentiation of pancreatic β-islet cells, we investigated the effect of upregulating Pdx1 and Ngn3 during the differentiation of the β-islet-like cells from murine embryonic stem (ES) cell-derived activin induced-endoderm. Induced overexpression of Pdx1 resulted in a significant upregulation of insulin (Ins1 and Ins2), and other pancreas-related genes. To enhance the developmental progression from the pancreatic bud to the formation of the endocrine lineages, we induced the overexpression express of Ngn3 together with Pdx1. This combination dramatically increased the level and timing of maximal Ins1 mRNA expression to approximately 100% of that found in the βTC6 insulinoma cell line. Insulin protein and C-peptide expression was confirmed by immunohistochemistry staining. These inductive effects were restricted to c-kit(+) endoderm enriched EB-derived populations suggesting that Pdx1/Ngn3 functions after the specification of pancreatic endoderm. Although insulin secretion was stimulated by various insulin secretagogues, these cells had only limited glucose response. Microarray analysis was used to evaluate the expression of a broad spectrum of pancreatic endocrine cell-related genes as well as genes associated with glucose responses. Taken together, these findings demonstrate the utility of manipulating Pdx1 and Ngn3 expression in a stage-specific manner as an important new strategy for the efficient generation of functionally immature insulin-producing β-islet cells from ES cells. 相似文献
54.
The inactivation of Bacteroides fragilis genes encoding putative RecQ helicases recQ1, recQ2 and recQ3 (ORFs BF638R_3282, BF638R_3781, BF638R_3932) was used to determine whether these proteins are involved in cell survival following metronidazole exposure. The effects of the mutations on growth, cellular morphology and DNA integrity were also evaluated. Mutations in the RecQ DNA helicases caused increased sensitivity to metronidazole, with recQ1, recQ2 and recQ3 mutants being 1.32-fold, 41.88-fold and 23.18-fold more sensitive than the wild type, respectively. There was no difference in cell growth between the recQ1 and recQ3 mutants and the wild type. However, the recQ2 mutant exhibited reduced cell growth, aberrant cell division and increased pleiomorphism, with an increase in filamentous forms and chains of cells being observed using light, fluorescence and electron microscopy. There was no spontaneous accumulation of DNA single- or double-strand breaks in the recQ mutants, as compared with the wild type, during normal cell growth in the absence of metronidazole. Bacteroides fragilis RecQ DNA helicases, therefore, enhance cell survival following metronidazole damage. The abnormal cellular phenotype and growth characteristics of recQ2 mutant cells suggest that this gene, or the downstream gene of the operon in which it occurs, may be involved in cell division. 相似文献
55.
David K. Clarke Farooq Nasar Siew Chong J. Erik Johnson John W. Coleman Margaret Lee Susan E. Witko Cheryl S. Kotash Rashed Abdullah Shakuntala Megati Amara Luckay Becky Nowak Andrew Lackner Roger E. Price Peter Little Narender Kalyan Valerie Randolf Ali Javadian Timothy J. Zamb Christopher L. Parks Michael A. Egan John Eldridge Michael Hendry Stephen A. Udem 《Journal of virology》2014,88(12):6690-6701
56.
Valerie J. Horn Paul A. Sheehy Miriam B. Goodman Indu S. Ambudkar 《Molecular and cellular biochemistry》1991,101(1):43-49
Intracellular Ca2+ mobilization events were assessed in mouse L cells, which contain native prostaglandin E1 receptors and transfected human 2 adrenergic receptors. Both Fura2 (single cell measurements) and Quin 2, (cuvette assays) were used to determine [Ca2+]i levels. Our results demonstrate that in the transfected cells there is a dose-dependent increase in [Ca2+]i in response to isoproterenol (0.1 nM–100 nM), which is inhibited by the -adrenergic antagonist, propranolol, and is a result of intracellular Ca2+ release. [Ca2+]1 in these cells was also increased by prostaglandin E1, 8 bromo cyclic AMP, and aluminum fluoride. Both 8 bromo cAMP and isoproterenol induced a rapid increase in the levels of IP1, IP2, and IP3. The data presented demonstrate that the elevation of intracellular cyclic AMP induces an increase in IP3 production which leads to an elevation in [Ca2+];. We propose that this cyclic AMP dependent activation of the IP3 generating system occurs at a post-receptor site.Abbreviations cAMP
Adenosine Cyclic 3-5-Monophosphate
- [Ca2+]i
intracellular [Ca2+]i
- 8 Br cAMP
8 Bromo Adenosine Cyclic 3-5-Monophosphate
- DAG
Diacylglycerol
- EGTA]
[Ethylene Bis (oxyethylenenitrilo)] Tetracetic acid
- BSA
Bovine Serum Albumin
- HBSS-H
Hanks' Balanced Salt Solution buffered with HEPES to pH 7.4
- HEPES
4-(2-Hydroxyethyl)-1-piperazineethanesulfonic acid
- PIP2
Phosphatidylinositol 4,5-bisphosphate
- IP2
Inositol 4 Phosphate
- IP2
Inositol 4,5 Bisphosphate
- IP3
Inositol Trisphosphate
- PGE1
Prostaglandin E1
- PBS
Phosphate Buffered Saline Solution 相似文献
57.
Mayer Alejandro M. S. Paul Valerie J. Fenical William Norris James N. de Carvalho M. S. Jacobs Robert S. 《Hydrobiologia》1993,260(1):521-529
Twelve out of twenty-nine compounds isolated from benthic marine algae from the phyla Chlorophyta, Phaeophyta and Rhodophyta have been found to be potent inhibitors of bee venom derived phospholipase A2 (PLA2) (> 50%) in the M range. The compounds investigated were from: Bryopsis pennata, Rhipocephalus phoenix, Caulerpa prolifera, C. racemosa, C. bikinensis, Cymopolia barbata, Laurencia cf. palisada, Laurencia sp., Ochtodes crockeri, Liagora farinosa, Sphaerococcus coronipifolius, Phacelocarpus labillardieri, Dictyota sp., B furcaria galapagensis, Stypopodium zonale, Dictyopteris undulata, Stoechospermum marginatum, Dictyopteris divaricata, Dilophus fasciola and Dilophus sp. This is the first report of bee venom PLA2 inhibition in vitro by pure compounds isolated from marine algae. 相似文献
58.
James Hansen Pushker Kharecha Makiko Sato Valerie Masson-Delmotte Frank Ackerman David J. Beerling Paul J. Hearty Ove Hoegh-Guldberg Shi-Ling Hsu Camille Parmesan Johan Rockstrom Eelco J. Rohling Jeffrey Sachs Pete Smith Konrad Steffen Lise Van Susteren Karina von Schuckmann James C. Zachos 《PloS one》2013,8(12)
We assess climate impacts of global warming using ongoing observations and paleoclimate data. We use Earth’s measured energy imbalance, paleoclimate data, and simple representations of the global carbon cycle and temperature to define emission reductions needed to stabilize climate and avoid potentially disastrous impacts on today’s young people, future generations, and nature. A cumulative industrial-era limit of ∼500 GtC fossil fuel emissions and 100 GtC storage in the biosphere and soil would keep climate close to the Holocene range to which humanity and other species are adapted. Cumulative emissions of ∼1000 GtC, sometimes associated with 2°C global warming, would spur “slow” feedbacks and eventual warming of 3–4°C with disastrous consequences. Rapid emissions reduction is required to restore Earth’s energy balance and avoid ocean heat uptake that would practically guarantee irreversible effects. Continuation of high fossil fuel emissions, given current knowledge of the consequences, would be an act of extraordinary witting intergenerational injustice. Responsible policymaking requires a rising price on carbon emissions that would preclude emissions from most remaining coal and unconventional fossil fuels and phase down emissions from conventional fossil fuels. 相似文献
59.
O'Sullivan VJ Barrette-Ng I Hommema E Hermanson GT Schofield M Wu SC Honetschlaeger C Ng KK Wong SL 《PloS one》2012,7(4):e35203
A novel form of tetrameric streptavidin has been engineered to have reversible biotin binding capability. In wild-type streptavidin, loop(3-4) functions as a lid for the entry and exit of biotin. When biotin is bound, interactions between biotin and key residues in loop(3-4) keep this lid in the closed state. In the engineered mutein, a second biotin exit door is created by changing the amino acid sequence of loop(7-8). This door is mobile even in the presence of the bound biotin and can facilitate the release of biotin from the mutein. Since loop(7-8) is involved in subunit interactions, alteration of this loop in the engineered mutein results in an 11° rotation between the two dimers in reference to wild-type streptavidin. The tetrameric state of the engineered mutein is stabilized by a H127C mutation, which leads to the formation of inter-subunit disulfide bonds. The biotin binding kinetic parameters (k(off) of 4.28×10(-4) s(-1) and K(d) of 1.9×10(-8) M) make this engineered mutein a superb affinity agent for the purification of biotinylated biomolecules. Affinity matrices can be regenerated using gentle procedures, and regenerated matrices can be reused at least ten times without any observable reduction in binding capacity. With the combination of both the engineered mutein and wild-type streptavidin, biotinylated biomolecules can easily be affinity purified to high purity and immobilized to desirable platforms without any leakage concerns. Other potential biotechnological applications, such as development of an automated high-throughput protein purification system, are feasible. 相似文献
60.
David Michael Drew Geoffrey M. Downes Valerie Grzeskowiak Thimagren Naidoo 《Trees - Structure and Function》2009,23(3):585-595
Understanding daily stem size variation is important as the net increment of a forest stand is ultimately determined by the
accumulation of daily increment events. In this study, measurements of stem size at high spatial and temporal resolution were
made using two commercial hybrid Eucalyptus clones [E. grandis × urophylla (GU) and E. grandis × camaldulensis (GC)] over a period of more than 3.5 years in order to better understand how daily stem growth is effected by variations
in environmental conditions. It was evident that GU had fewer days on which net growth occurred than GC. However, when growth
did occur, GU grew for longer each day and at a higher rate than GC. Thus, it still had an overall larger net stem increment
during the study period. The GU clone had a markedly intermittent pattern of growth, such that growth essentially ceased under
drought conditions, but responded rapidly when water became available. This confirms other findings that E. grandis × urophylla is more susceptible to drought stress than E. grandis × camaldulensis, but emphasizes that a strategy of “rapid response” when environmental conditions become temporarily non-limiting is a good
one in terms of net increment at sites such as in this study.
相似文献
David Michael DrewEmail: |