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991.
HPLC法同时测定千斤拔属植物7种黄酮的含量 总被引:1,自引:0,他引:1
目的:测定千斤拔属7种植物中的7种黄酮类的含量,为千斤拔类药材质量控制提供依据。方法:色谱条件为Hedera C18色谱柱(250 mm×4.6 mm,5.0μm):流速1.2 mL/min,流动相为0.5%HAc水和乙腈梯度洗脱,柱温35℃,检测波长263 nm。结果:七种黄酮类成分在90 min内达到现行分离,线性关系良好(,R2>0.9995),日内、日间精密度、稳定性和重复性的RSD≤3.0%。该法成功的应用于千斤拔药材7种黄酮的评均回收率分别为96.94%~105.29%(RSD≤2.98%)结论:本方法准确、快速、重现性好,不同品种的千斤拔药材质量存在差异,可以为研究千斤拔药材的质量标准提供依据。 相似文献
992.
993.
994.
Hongping Kou Dan Wang Xiuyun Lin Ying Wu Chunming Xu Shaochen Xing Bao Liu 《植物学报(英文版)》2011,53(10):814-823
Pib is a well‐characterized rice blast‐resistance gene belonging to the nucleotide binding site (NBS) and leucine‐rich repeat (LRR) superfamily. Expression of Pib was low under non‐challenged conditions, but strongly induced by the blast‐causing fungal pathogen Magnaporthe grisea, thereby conferring resistance to the pathogen. It is generally established that cytosine methylation of the promoter‐region often plays a repressive role in modulating expression of the gene in question. We report here that two critical regions of the Pib promoter were heavily CG cytosine‐methylated in both cultivars studied. Surprisingly, induced expression of Pib by M. grisea infection did not entail its promoter demethylation, and partial demethylation by 5‐azacytidine‐treatment actually reduced Pib expression relative to wild‐type plants. Accordingly, the blast disease‐resistance was compromised in the 5′‐azaC‐treated plants relative to wild‐type. In contrast, the disease susceptibility was not affected by the 5′‐azaC treatment in another two rice cultivars that did not contain the Pib gene, ruling out effects of other R genes and non‐specific genotoxic effects by the drug‐treatment as a cause for the compromised Pib‐conditioned blast‐resistance. Taken together, our results suggest that promoter DNA methylation plays a novel enhancing role in conditioning high‐level of induced expression of the Pib gene in times of M. grisea infection, and its conferred resistance to the pathogen. 相似文献
995.
Background
Limited information is available on the relationship between nevirapine plasma concentrations and virologic response or liver toxicity in Chinese patients with HIV infection. The objective of this prospective study was to test this relationship and to determine the minimal therapeutic trough concentration of nevirapine for Chinese patients.Methods
A total of 227 HIV-infected, treatment naïve patients were enrolled into this study. Blood samples were taken at Ctrough (12 hr postdose) and C2 (2 hr postdose) for measurement of nevirapine concentrations 6 months after treatment initiation. Therapeutic outcomes, viral load and CD4 cell count, were assessed at 3 and 6 months after starting therapy, while the evaluation of hepatotoxicity was undertaken 12 months after nevirapine treatment.Results
A significant correlation between nevirapine trough concentrations and viral load was noticed after 6 months of treatment, particularly in patients with partial response and viral failure (p<0.01). The therapeutic Ctrough of nevirapine for Chinese patients was determined to be 3.9 µg/ml using the receiver operating characteristic curve. Virologic failure was observed in 21% (6/29) of patients with low nevirapine concentrations (<3.9 µg/ml) versus 5% (4/87) in patients with concentrations higher than 3.9 µg/ml (p = 0.015). Hepatotoxicity was significantly associated with the median nevirapine trough concentrations among male patients (8.20 vs. 5.48 µg/ml, p = 0.015) and hepatitis C virus co-infection (p = 0.039).Conclusions
Among Chinese patients with HIV infection, the therapeutic Ctrough of nevirapine was 3.9 µg/ml, higher than the recommended 3.0 µg/ml. The correlation between nevirapine concentrations, efficacy and hepatotoxicity suggests the benefit of dosage adjustment based on therapeutic drug monitoring among Chinese HIV-infected patients to optimize nevirapine containing antiretroviral therapy. 相似文献996.
Ruqin Kou Juliano Sartoretto Thomas Michel 《The Journal of biological chemistry》2009,284(22):14734-14743
These studies explore the connections between simvastatin, Rac1, and
AMP-activated protein kinase (AMPK) pathways in cultured vascular endothelial
cells and in arterial preparations isolated from statin-treated mice. In
addition to their prominent effects on lipoprotein metabolism, statins can
regulate the small GTPase Rac1, and may also affect the phosphorylation of the
ubiquitous AMPK. We explored pathways of statin-modulated Rac1 and AMPK
activation both in arterial preparations from statin-treated mice as well as
in cultured endothelial cells. We treated adult mice with simvastatin daily
for 2 weeks and then harvested and analyzed arterial preparations. Simvastatin
treatment of mice led to a significant increase in AMPK and LKB1
phosphorylation and to a decrease in protein kinase A activity relative to
control animals, associated with a marked increase in Rac1 activation.
Exposure of bovine aortic endothelial cells to simvastatin for 24 h strikingly
increased GTP-bound Rac1 and led to increased phosphorylation of AMPK as well
as the AMPK kinase LKB1. These responses to simvastatin were blocked by
mevalonate or geranylgeranyl pyrophosphate but not by farnesyl pyrophosphate.
Small interfering RNA (siRNA)-mediated knockdown of AMPK abrogated
simvastatin-induced Rac1 activation and LKB1 phosphorylation. Importantly,
siRNA-mediated knockdown of the key AMPK kinase, calcium/calmodulin-dependent
protein kinase kinase β, completely blocked simvastatin-induced
endothelial cell migration and also abrogated statin-promoted phosphorylation
of AMPK and LKB1, as did pharmacological inhibition with the specific
calcium/calmodulin-dependent protein kinase β inhibitor STO-609.
Moreover, siRNA-mediated knockdown of Rac1 completely blocked
simvastatin-induced LKB1 phosphorylation, but without affecting
simvastatin-induced AMPK phosphorylation. These findings establish a key role
for simvastatin in activation of a novel Rac1-dependent signaling pathway in
the vascular wall.HMG-CoA2 reductase
inhibitors, commonly known as statins, are widely prescribed for the
prevention and treatment of hypercholesterolemia and cardiovascular diseases
(1,
2). The salutary clinical
effects of these drugs derive in part from their effects on the levels of
serum lipoproteins, yet other statin responses appear to be mediated by
alterations in vascular function involving the endothelial isoform of
nitric-oxide synthase (3) and
related signaling pathways. Inhibition of HMG-CoA reductase suppresses the
cellular levels of its enzymatic product mevalonate, thereby attenuating
formation both of cholesterol as well as the synthesis of distinct isoprenoid
compounds such as farnesyl pyrophosphate (Fpp) and geranylgeranyl
pyrophosphate (GGpp). Many key signaling proteins are covalently modified by
these isoprenoids, which are the products of a metabolic pathway that diverges
from the pathway that leads to cholesterol synthesis downstream of HMG-CoA
reductase. These isoprenoid compounds can provide lipophilic anchors that
facilitate membrane targeting and modulate protein-protein interactions of
many key signaling proteins. One such iso-prenylated signaling protein is the
GTP-binding cytoskeletonassociated protein Rac1, a member of the Rho GTPase
small G protein family that undergoes geranylgeranylation at its C terminus.
Statins also affect post-translational modification of another small GTPase,
RhoA, that, like Rac1, is a geranylgeranylated protein that is an important
determinant of vascular signaling
(4–8).
Rac1 has particularly important roles in vascular endothelial cells, where
this cytoskeleton regulatory protein modulates activity of the endothelial
isoform of nitric-oxide synthase (eNOS), a key determinant of vascular
homeostasis (9). Rac1
activation in endothelial cells is influenced by the AMP-activated protein
kinase (AMPK) (6), which itself
is phosphorylated by the protein kinase LKB1 and by the
calcium-calmodulin-dependent protein kinase β (CaMKKβ) (see review
(10)). In recent years,
numerous reports have described effects of statins on variety of these
signaling proteins in different experimental systems
(11–14).Statins have been shown to promote the phosphorylation of AMPK
(13), a heterotrimeric enzyme
involved in the modulation of cellular energy pathways that has also been
implicated in eNOS regulation
(3,
15–17).
AMPK was originally discovered and characterized as a cellular “energy
sensor” that can be activated by increases in the intracellular AMP:ATP
ratio (18). However, in recent
years, it has become clear that AMPK is also regulated through AMP-independent
pathways involving enzyme phosphorylation on threonine 172 of the enzyme''s
α subunit, leading to marked enzyme activation
(19). Protein kinases that
phosphorylate AMPK include the tumor suppressor LKB1 and the
calcium/calmodulin-dependent kinase CaMKKβ. LKB1 itself is a
phosphoprotein. The pathways that regulate LKB1 are incompletely understood,
and a variety of upstream protein kinases have been implicated in LKB1
regulation (see review (20)).
CaMKKβ is principally regulated by calcium binding, but this kinase may
also be phosphorylated by the cAMP-dependent protein kinase PKA
(21,
22). Another substrate for PKA
in vascular cells is the actin-binding phosphoprotein VASP
(23,
24); the phosphorylation state
of VASP at its PKA site can serve as a surrogate marker for the activity of
cAMP-dependent signaling pathways in the vascular wall
(25). CaMKKβ has been
shown to be involved in AMPK regulation in endothelial cells in response to
receptor tyrosine kinase activation and via G protein-coupled receptor
pathways (6). Activated AMPK
directly phosphorylates eNOS, and this kinase thereby appears be an important
determinant of NO-dependent signaling in endothelial cells. However, much
remains to be learned about the molecular mechanisms whereby statins enhance
AMPK activation.In cultured cells, statins have been shown to inhibit the
geranylgeranylation of Rac1, associated with an increase in Rac1 GTP binding
and activation (26). The
activation of Rac1 is a key step in eNOS activation: siRNA-mediated Rac1
“knockdown” in endothelial cells markedly suppresses receptor
signaling to eNOS (5,
7). siRNA-mediated AMPK
knockdown suppresses Rac1 activation, again leading to the attenuation of
receptor-dependent activation of eNOS
(6). The relationships among
these various statin-modulated signaling pathways are incompletely
characterized. The present studies identify CaMKKβ and LKB1 as critical
determinants of simvastatin-dependent activation of AMPK- and Rac1-modulated
signaling and reveal that Rac1 in turn regulates LKB1 phosphorylation. 相似文献
997.
Shen B Zhang Z Wang Y Wang G Chen Y Lin P Wang S Zou Z 《Molecular biology reports》2009,36(5):1149-1157
In order to identify genes involved in oogenesis and spermatogenesis in penaeid shrimp Marsupenaeus japonicus, a modified annealing control primer (ACP) system was adapted to identify genes differentially expressed in ovary and testis at different developmental stages.
By using 20 pairs of ACP primers, 8 differentially expressed genes were obtained. One of these genes is ubiquitin-conjugating
enzyme E2r (UBE2r). Bioinformatics analyses show that this gene encodes a protein of 241 amino acids with a predicted molecular mass of 27.4 kDa.
Real time PCR analyses demonstrated that the expression level changed significantly in the developing testis and ovary. In
the stage 2 of testis, it reached its highest expression level, the lowest expression level present in the stage 1 of ovary.
The significantly different expression levels in developing testis and ovary suggest that UBE2r has an important role in oogenesis and spermatogenesis. This article is the first report of UBE2r in crustaceans and also is the first report showing that UBE2r is differentially expressed at different stages of the developing ovary and testis in an animal. 相似文献
998.
999.
Zhihua Jia Xiaoli Zhang Yaling Zhao Xuejun Cao 《World journal of microbiology & biotechnology》2009,25(7):1235-1241
Effects of six divalent metal cations: Fe2+, Ca2+, Zn2+, Mg2+, Cu2+and Mn2+ on fungal cell growth and lovastatin biosynthesis were investigated by submerged cultivation of Aspergillus terreus in a modified chemically defined medium. The influences of different initial concentrations of the above six metal cations
were also examined at 1, 2, and 5 mM, respectively. Cu2+ apparently inhibited the cell growth, but had no influence on biosynthesis of lovastatin. All of Fe2+, Ca2+, Zn2+, Mg2+ and Mn2+ promoted the cell growth and lovastatin biosynthesis in different extents. The highest biomass of 13.8 ± 0.5 g l−1 and specific lovastatin titres of 49.2 ± 1.4 mg gDCW−1 were obtained at the level of 2 and 5 mM in the presence of Zn2+, respectively. The values were improved double and 14.4-fold. Excess Zn2+ inhibited the cell growth, but enhanced lovastatin biosynthesis with an increment of 17.6 mg l−1 per mM. The interactions of all metal cations slightly inhibited the lovastatin production comparing with the existence of
Zn2+, Fe2+ and Mg2+ solely, yet remarkably improved the cell growth. These results suggest that the divalent metal ions Zn2+ or Fe2+ influence the production by regulating the action of key enzymes such as LovD or LovF in lovastatin biosynthesis. 相似文献
1000.
Jian Shen Shiyang Liu Huaiwu Zhang S. T. Chui Zhifang Lin Xin Fan Xiaoming Kou Qi Lu John Q. Xiao 《Plasmonics (Norwell, Mass.)》2012,7(2):287-291
We have demonstrated experimentally a one-way magnetic surface plasmon (MSP) electromagnetic (EM) waveguide in the microwave range based on the magnetic photonic crystals (MPCs). The waveguide exhibits asymmetric transmission of EM waves in the frequency range near the MSP resonance for an MPC, such that a significant one-way propagation can be observed in the channel between the two MPC slabs, each in an external static magnetic field (ESMF) of opposite directions. The one-way waveguide is not only immune to interstitial metal defects but also robust against the disorder of rod position. Furthermore, its working frequency can be flexibly tuned by an ESMF, which makes it more favorable for the design of EM devices. The physics is related to the broken time-reversal symmetry of the MSP band states and the excitation of a giant circulation of the energy flow, similar to the case in the quantized Hall effect. 相似文献