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排序方式: 共有1733条查询结果,搜索用时 19 毫秒
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93.
AH Wu 《Canadian Metallurgical Quarterly》1998,272(1):11-21
We tested the hypothesis that preventing cyclic GMP degradation with zaprinast, (a selective cyclic GMP-phosphodiesterase inhibitor) would produce a blunted reduction in myocardial O2 consumption in renal hypertension (One Kidney-One Clip, 1K1C)-induced cardiac hypertrophy. Four groups of anesthetized open-chest New Zealand white rabbits (n = 26) were utilized. Either vehicle or zaprinast (3 x 10(-3) M) was applied topically to the left ventricular surface of control or 1K1C rabbits. Coronary blood flow (radioactive microspheres) and O2 extraction (microspectrophotometry) were used to determine O2 consumption. Myocardial cyclic GMP levels were determined by radioimmunoassay. The 1K1C rabbits had a greater heart weight-to-body weight ratio (2.94 +/- 0.08 g/kg) than controls (2.58 +/- 0.17). Systolic blood pressure was higher in 1K1C (102 +/- 9 mm Hg) than in controls (86 +/- 3). Zaprinast significantly and similarly increased cyclic GMP in both control (3.90 +/- 0.47 to 4.66 +/- 0.89 pmol/g) subepicardium (EPI) and (5.08 +/- 0.69 to 7.06 +/- 1.36) subendocardium (ENDO) and 1K1C hearts (5.53 +/- 0.61 to 7.48 +/- 1.51 EPI and 6.48 +/- 0.42 to 8.88 +/- 1.08 ENDO). Myocardial O2 consumption (ml O2/min/ 100 g) was significantly lower in controls treated with zaprinast (EPI: 8.8 +/- 0.1; ENDO: 9.5 +/- 1.9) than in controls treated with vehicle (EPI: 13.6 +/- 1.3; ENDO: 16.2 +/- 2.9). This effect was diminished in 1K1C rabbits treated with zaprinast (EPI: 10.3 +/- 2.4; ENDO: 11.2 +/- 2.6) compared with the vehicle-treated 1K1C group (EPI: 13.3 +/- 1.2; ENDO: 14.5 +/- 2.4). There was a similar increase in myocardial cyclic GMP after treatment with zaprinast, but a greater depression of myocardial O2 consumption in control animals than in 1K1C after treatment with zaprinast. This suggested that the reduction in myocardial O2 consumption, related to increases in cyclic GMP caused by cyclic GMP-phosphodiesterase blockade, was less in 1K1C cardiac hypertrophy. 相似文献
94.
LaBO3 (B = Ni, Co, Fe and Mn) were prepared by microwave-assisted citrate method. The electrocatalytic activity toward hydrogen evolution reaction (HER) was investigated. XRD characterization showed that pure perovskite crystals were indeed formed. SEM images showed that changing the type of the B-site metal ion affected the morphology of the prepared perovskites. The influence of the type of B-cation on the catalytic activity toward hydrogen evolution was studied and the order of the electrocatalytic activity was LaFeO3 > LaCoO3 > LaNiO3 > LaMnO3, that was related to the calculated values of the activation energy 51.61, 45.37, 41.15 and 55.05 kJ mol−1 for LaBO3 (B = Ni, Co, Fe and Mn), respectively. The reaction order and the reaction mechanism for all the prepared perovskites were identified. In addition, the effect of the partial substitution at the B-site in LaNi1 − xCoxO3 was also studied. It was found that among ternary perovskites, the catalytic activity of LaNiO3 decreased by increasing the fraction of doped-Co. 相似文献
95.
Sardar Muhammad Bilal Atta ur Rehman Khan Samee Ullah Khan Sajjad A. Madani Babar Nazir Mazliza Othman 《Wireless Personal Communications》2014,77(4):2497-2515
Over the last few years, vehicular ad hoc networks (VANETs) have gained popularity for their interesting applications. To make efficient routing decisions, VANET routing protocols require road traffic density information for which they use density estimation schemes. This paper presents a distributed mechanism for road vehicular density estimation that considers multiple road factors, such as road length and junctions. Extensive simulations are carried out to analyze the effectiveness of the proposed technique. Simulation results suggested that, the proposed technique is more accurate compared to the existing technique. Moreover, it facilitate VANET routing protocols to increase packet delivery ratio and reduce end-to-end delay. 相似文献
96.
Granules containing indomethacin crystals are coated with Eudragit solutions of different RL/RS ratios using a pan coating technique. The process is reproducible with regard to drug content, inexpensive and the formed granules were directly compressed into tablets. In vitro release of indomethacin from coated granules, tablets and capsules was studied as a function of different ratios of Eudragit RL/RS in the coating solution. The release of the drug was significantly reduced by the coating process in comparison with a formulation made from uncoated granules, prepared using 10 per cent gelatin solution as a binder. Release data were found to follow a diffusion-controlled model. 相似文献
97.
Background
Rye products have been demonstrated to lower the acute insulin demand, induce a low and prolonged blood glucose response (high Glycemic Profile, GP) and reduce subclinical inflammation. These products may therefore contribute to a lowered risk of obesity, type 2 diabetes and cardio vascular disease. The objective of the present paper was to evaluate the mechanism for a reduced postprandial insulin demand with rye products, and to explore possible appetite regulating properties. 相似文献98.
Magda A Akl Ayman M Atta Abd El-Fatah M Yousef Mohamed I Alaa 《Polymer International》2013,62(12):1667-1677
Stabilized and dispersed superparamagnetic porous nanogels based on sodium acrylate (AA‐Na) and acrylamide (AM) in a surfactant‐free aqueous system were synthesized via solution polymerization at room temperature. The formation of magnetite nanoparticles was confirmed and their properties characterized using Fourier transform infrared spectroscopy. Extensive characterization of the magnetic polymer particles using transmission electron microscopy (TEM), dynamic light scattering and zeta potential measurements revealed that Fe3O4 nanoparticles were incorporated into the shells of poly(AM/AA‐Na). The average particle size was 5–8 nm as determined from TEM. AM/AA‐Na nanoparticles with a diameter of about 11 nm were effectively assembled onto the negatively charged surface of the as‐synthesized Fe3O4 nanoparticles via electrostatic interaction. Crosslinked magnetite nanocomposites were prepared by in situ development of surface‐modified magnetite nanoparticles in an AM/AA‐Na hydrogel. Scanning electron microscopy was used to study the surface morphology of the prepared composites. The morphology, phase composition and crystallinity of the prepared nanocomposites were characterized. Atomic force microscopy and argon adsorption–desorption measurements of Fe3O4.AM/AA indicated that the architecture of the polymer network can be a hollow porous sphere or a solid phase, depending on the AA‐Na content. © 2013 Society of Chemical Industry 相似文献
99.
Porins are trimeric channel-forming proteins of the outer membrane ofEscherichia coli. Each subunit contains 16 beta-strands forming atransmembrane beta-barrel whose pore is constricted by the thirdextracellular loop (L3). We investigated the effects of site-directedmutations at two critical regions of the OmpC porin: (i) the D315A mutationtargets a key component of a putative hydrogen bond network linking the L3loop to the adjacent barrel wall and (ii) the D118Q, R174Q and R92Qmutations target putative salt bridges at the root of the L3 loop. Wepurified the outer membrane fractions obtained from each mutant andreconstituted them in liposomes suitable for electrophysiology. Patch clampexperiments showed that the frequency of spontaneous transitions betweenopen and closed states is increased in the D315A, D118Q and R92Q mutantsbut unchanged in the R174Q mutant. These transitions are not driven bytransmembrane voltage changes and represent the thermal oscillationsbetween functionally distinct conformations. The asymmetricvoltage-dependent inactivation of the channels is not affected by themutations, however, suggesting different molecular mechanisms for thespontaneous and voltage- dependent gating processes. We propose that thepositioning or flexibility of the L3 loop across the pore, as governed bythe putative hydrogen-bond network and a salt bridge, play a role indetermining the frequency of spontaneous channel gating. 相似文献
100.
W Roolker MM Tiel-van Buul AH Broekhuizen AK Eikelenboom EA van Royen 《Canadian Metallurgical Quarterly》1997,38(10):1600-1603
The diagnosis of scaphoid fracture is often difficult and of interest in traumatology. Because of the low sensitivity of repeated scaphoid radiographs, a bone scintigram is advocated and considered the gold standard. In this study, we tried to simplify the interpretation of the bone scintigram of hand and wrist in localizing the hot spot by the digital overlay of the radiograph and the bone scintigram, using a simple device, in patients after wrist trauma. METHODS: Twenty-one consecutive patients (22 wrists) with clinically-suspected scaphoid fracture and negative initial radiographs were included. The PA view of the wrist was obtained with the hand of the patient placed in an acrylic device with three lead markers. For the bone scan, a similar device was used with 57Co markers at the same positions. We called this device the "hand-fix." The PA radiograph was digitized with a videocamera and overlaid on the bone scan. Each bone scan was interpreted twice by each of three observers, one nuclear physician and two residents in nuclear medicine. The first interpretation was made without the digital overlay, and the second was made with the digital overlay. RESULTS: The bone scintigrams were positive in the scaphoid, distal radius and in other carpal bones. Out of the 22 bone scans, Observer 1 judged 19 correctly, Observer 2 judged 16 correctly and Observer 3 judged 10 correctly without the digital overlay images. All three observers gave a correct localization in the 22 wrists using the digital overlay images. CONCLUSION: The digital overlay of a radiograph and a bone scintigram, using the hand-fix, simplifies and improves interpreting and localizing the hot spot on bone scintigrams in patients with wrist injuries. 相似文献