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41.
Sharat J. Vayttaden Jacqueline Friedman Tuan M. Tran Thomas C. Rich Carmen W. Dessauer Richard B. Clark 《PLoS computational biology》2010,6(1)
We developed a unified model of the GRK-mediated β2 adrenergic receptor (β2AR) regulation that simultaneously accounts for six different biochemical measurements of the system obtained over a wide range of agonist concentrations. Using a single deterministic model we accounted for (1) GRK phosphorylation in response to various full and partial agonists; (2) dephosphorylation of the GRK site on the β2AR; (3) β2AR internalization; (4) recycling of the β2AR post isoproterenol treatment; (5) β2AR desensitization; and (6) β2AR resensitization. Simulations of our model show that plasma membrane dephosphorylation and recycling of the phosphorylated receptor are necessary to adequately account for the measured dephosphorylation kinetics. We further used the model to predict the consequences of (1) modifying rates such as GRK phosphorylation of the receptor, arrestin binding and dissociation from the receptor, and receptor dephosphorylation that should reflect effects of knockdowns and overexpressions of these components; and (2) varying concentration and frequency of agonist stimulation “seen” by the β2AR to better mimic hormonal, neurophysiological and pharmacological stimulations of the β2AR. Exploring the consequences of rapid pulsatile agonist stimulation, we found that although resensitization was rapid, the β2AR system retained the memory of the previous stimuli and desensitized faster and much more strongly in response to subsequent stimuli. The latent memory that we predict is due to slower membrane dephosphorylation, which allows for progressive accumulation of phosphorylated receptor on the surface. This primes the receptor for faster arrestin binding on subsequent agonist activation leading to a greater extent of desensitization. In summary, the model is unique in accounting for the behavior of the β2AR system across multiple types of biochemical measurements using a single set of experimentally constrained parameters. It also provides insight into how the signaling machinery can retain memory of prior stimulation long after near complete resensitization has been achieved. 相似文献
42.
Carry-over of deoxynivalenol (DON) into eggs was investigated within the scope of a 16-week experiment with laying hens, in
which the birds were fed a maize-based diet containing DON at 11.9 mg/kg dry matter. Eggs were collected during weeks 2, 4,
8, and 16. DON and its metabolite deepoxy-DON were analysed separately in freeze-dried yolk and albumen. Yolk was extracted
with water and the extract was purified using an immunoaffinity column (IAC). Albumen was extracted with acetonitrile-water
and the extract was pre-cleaned before applying an IAC. All albumen and some yolk samples were incubated with β-glucuronidase
prior to extraction. DON and de-epoxy-DON were determined by high performance liquid chromatography (HPLC) with diode array
detection (DAD). The detection limits of both toxins were 20 ng/g and 15 ng/g in freezedried yolk and albumen, respectively,
corresponding to approximately 10 ng/g and 2 ng/g in fresh samples. The recovery of DON/de-epoxy-DON in spiked samples (50–200
ng/g) was 87/83% (yolk) and 87/77% (albumen) with coefficients of variation of 4–15%. Neither DON nor de-epoxy-DON were detected
in any of the samples. In order to achieve lower detection limits, the methods are currently optimized. However, these preliminary
results indicate that eggs do not contribute significantly to the dietary DON intake of the consumer.
Presented at the 26th Mykotoxin-Workshop in Herrsching, Germany, May 17–19, 2004 相似文献
43.
Nimra Khan Dylan Pelletier Thomas S. McAlear Nathalie Croteau Simon Veyron Andrew N. Bayne Corbin Black Muneyoshi Ichikawa Ahmad Abdelzaher Zaki Khalifa Sami Chaaban Igor Kurinov Gary Brouhard Susanne Bechstedt Khanh Huy Bui Jean-François Trempe 《Structure (London, England : 1993)》2021,29(6):572-586.e6
44.
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46.
Lee D. Thomas 《Behavioural processes》2009,81(2):264-269
Four pigeons responded under a progressive-delay procedure. In a signaled-delay condition, a chained variable interval (VI) 30-s progressive time (PT) 4-s schedule was arranged; in an unsignaled-delay condition, a tandem VI 30-s PT 4-s schedule was arranged. Two pigeons experienced a signaled-unsignaled-signaled sequence; whereas, two pigeons experienced an unsignaled-signaled-unsignaled sequence. Effects of saline and d-amphetamine were determined under each condition. At intermediate doses (1.0 and 1.78 m/kg) delay functions were shallower, area under the curve was increased, and, when possible, break points were increased compared to saline; these effects were not systematically related to signaling conditions. These effects on control by delay often were accompanied by decreased response rates at 0 s. These results suggest that stimulus conditions associated with the delay may not play a crucial role in effects of d-amphetamine and other stimulants on behavior controlled by reinforcement delay. 相似文献
47.
We present a fast, reliable and inexpensive restriction-free cloning method for seamless DNA insertion into any plasmid without sequence limitation. Exponential megapriming PCR (EMP) cloning requires two consecutive PCR steps and can be carried out in one day. We show that EMP cloning has a higher efficiency than restriction-free (RF) cloning, especially for long inserts above 2.5 kb. EMP further enables simultaneous cloning of multiple inserts. 相似文献
48.
49.
DNA was efficiently and quantitatively isolated from extremely small quantities of mycelia (0.1–10 mg) of different phytopathogenic
moulds by grinding freeze-dried mycelia with glass beads and then using a commercial DNA extraction kit. The efficiency of
disruption of the mycelia and the quantitative DNA extraction was proved by microscopy and the quantification of isolated
DNA by real time PCR.
Presented at the 27th Mykotoxin-Workshop, Dortmund, Germany, June 13–15, 2005
Financial support: German Research Foundation (DFG grant Pr 708/2). J.M. thanks the Cusanuswerk for a doctoral scholarship 相似文献
50.