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991.
Seventeen additional minor ecdysteroid compounds were isolated and identified from the roots of Leuzea carthamoides (Wild.) DC. Eight of them are new phytoecdysteroids: carthamoleusterone (13) is a new side-chain cyclo-ether with five-membered ring; 14-epi-ponasterone A 22-glucoside (12) is a rare and unusual natural 14 beta-OH epimer; 15-hydroxyponasterone A (11) is also new and rare with its C-15 substituted position, as well as 22-deoxy-28-hydroxymakisterone C (18) possessing secondary hydroxyl in position C-28 and 26-hydroxymakisterone C (20) with hydroxy groups in positions 25 and 26. New are also 1 beta-hydroxymakisterone C (21) and 20,22-acetonides of inokosterone (8) and integristerone A (10). Series of already known ecdysteroids: ecdysone (1), 20-hydroxyecdysone 2- and 3-acetates (3 and 4), turkesterone (6), inokosterone (7), 24-epi-makisterone A (14), and amarasterone A (22) are reported here as new constituents of L. carthamoides. Seven earlier reported Leuzea ecdysteroids: 20-hydroxyecdysone (2), ajugasterone C (5), integristerone A (9), 24(28)-dehydromakisterone A (15), 24(28)-dehydroamarasterone B (16), (24Z)-29-hydroxy-24(28)-dehydromakisterone C (17) and makisterone C (19) are also included because they are now better characterized. 相似文献
992.
Allioux-Guérin M Icard-Arcizet D Durieux C Hénon S Gallet F Mevel JC Masse MJ Tramier M Coppey-Moisan M 《Biophysical journal》2009,96(1):238-247
We investigate the dynamic response of single cells to weak and local rigidities, applied at controlled adhesion sites. Using multiple latex beads functionalized with fibronectin, and each trapped in its own optical trap, we study the reaction in real time of single 3T3 fibroblast cells to asymmetrical tensions in the tens of pN · μm−1 range. We show that the cell feels a rigidity gradient even at this low range of tension, and over time develops an adapted change in the force exerted on each adhesion site. The rate at which force increases is proportional to trap stiffness. Actomyosin recruitment is regulated in space and time along the rigidity gradient, resulting in a linear relationship between the amount of recruited actin and the force developed independently in trap stiffness. This time-regulated actomyosin behavior sustains a constant and rigidity-independent velocity of beads inside the traps. Our results show that the strengthening of extracellular matrix-cytoskeleton linkages along a rigidity gradient is regulated by controlling adhesion area and actomyosin recruitment, to maintain a constant deformation of the extracellular matrix. 相似文献
993.
994.
995.
Rui-Cin Lyu Hui-Yu Hu Lih-Ying Kuo Huei-Fen Lo Ping-Lin Ong Hui-Ping Chang Long-Liu Lin 《Current microbiology》2009,59(2):101-106
Role of the conserved Thr399 and Thr417 residues of Bacillus licheniformis γ-glutamyltranspeptidase (BlGGT) was investigated by site-directed mutagenesis. Substitutions of Thr399 and Thr417 of BlGGT with Ser resulted in a dramatic reduction in enzymatic activity. A complete loss of the GGT activity was observed in T399A,
T399C, T417A, and T417K mutant enzymes. Furthermore, mutations on these two residues impaired the capability of autocatalytic
processing of the enzyme. In vitro maturation experiments showed that BlGGT mutant precursors, pro-T399S, pro-T417S, and pro-T417A, could precede a time-dependent autocatalytic process to generate
the 44.9- and 21.7-kDa subunits; however, the processed T417A had no enzymatic activity. Measurement of intrinsic tryptophan
fluorescence revealed alteration of the microenvironment of aromatic amino acid residues, while Far-UV circular dichroism
spectra were nearly identical for wild-type and mutant enzymes. These results suggest that residues Thr399 and Thr417 are
important for BlGGT in the enzymatic maturation and reaction.
An erratum to this article can be found at 相似文献
996.
Hsu-Feng Lu Jai-Sing Yang Kuang-Chi Lai Shu-Chun Hsu Shu-Ching Hsueh Yuan-Liang Chen Jo-Hua Chiang Chi-Cheng Lu Chyi Lo Mei-Due Yang Jing-Gung Chung 《Neurochemical research》2009,34(8):1491-1497
Curcumin is reported to be a potent inhibitor of the initiation and promotion of many cancer cells. We investigated to examine
whether or not curcumin induce DNA damage in mouse–rat hybrid retina ganglion cell line N18 cells. The Comet assay showed
that incubation of N18 cells with 10, 25 and 30 μM of curcumin led to a longer DNA migration smear (Comet tail). The DNA gel
electrophoresis showed that 20 μM of curcumin for 24 and 48 h treatment induced DNA damage and fragments in N18 cells. The
real time PCR analysis showed that 20 μM of curcumin for 48 h treatment decreased ATM, ATR, BRCA1, 14-3-3σ, DNA-PK and MGMT
mRNA, and ATM and MGMT mRNA expression were inhibited in a time-dependent manner. Our results indicate that curcumin caused
DNA damage and inhibited DNA repair genes which may be the factors for curcumin-inhibited cell growth.
H.-F. Lu and J.-S. Yang are contributed equally to this study. 相似文献
997.
998.
Lai Hong Fu Yansong Miao Sze Wan Lo Tai Chi Seto Samuel S.M. Sun Zeng-Fu Xu Sabine Clemens Lorne A. Clarke Allison R. Kermode Liwen Jiang 《Plant science》2009,177(6):668-675
Lysosomal storage diseases (LSDs), that collectively represent over 50 disorders, are amenable to enzyme replacement therapies. However, the current methods used to commercially produce recombinant lysosomal enzymes for this purpose, most commonly Chinese Hamster Ovary cells and human fibroblasts, are prohibitively costly. Plant bioreactors hold great promise for economic production of functional human α-l-iduronidase (hIDUA; glycosaminoglycan α-l-iduronohydrolase; EC 3.2.1.76), the enzyme deficient in the human LSD, Mucopolysaccharidosis I. We have developed and tested an expression system using transgenic tobacco BY-2 cells to produce high amounts of active hIDUA. A plant signal peptide was essential for proper expression and secretion of the 78 kDa glycosylated hIDUA into the cultured media of transgenic BY-2 cells. The yield and activity of the secreted hIDUA from long-term cultures of transgenic BY-2 cell lines were as high as 10 μg/mL media and 53,000 pmol/min/mg proteins, respectively. Thus, this transgenic BY-2 cell line presents an attractive platform for economic production and easy downstream purification of hIDUA for enzyme replacement therapy. Furthermore, this system can be used for the production and purification of other human lysosomal enzymes or pharmaceuticals. 相似文献
999.
Stefano Caffarri Roman Kouřil Sami Kereïche Egbert J Boekema Roberta Croce 《The EMBO journal》2009,28(19):3052-3063
Photosystem II (PSII) is a large multiprotein complex, which catalyses water splitting and plastoquinone reduction necessary to transform sunlight into chemical energy. Detailed functional and structural studies of the complex from higher plants have been hampered by the impossibility to purify it to homogeneity. In this work, homogeneous preparations ranging from a newly identified particle composed by a monomeric core and antenna proteins to the largest C2S2M2 supercomplex were isolated. Characterization by biochemical methods and single particle electron microscopy allowed to relate for the first time the supramolecular organization to the protein content. A projection map of C2S2M2 at 12 Å resolution was obtained, which allowed determining the location and the orientation of the antenna proteins. Comparison of the supercomplexes obtained from WT and Lhcb‐deficient plants reveals the importance of the individual subunits for the supramolecular organization. The functional implications of these findings are discussed and allow redefining previous suggestions on PSII energy transfer, assembly, photoinhibition, state transition and non‐photochemical quenching. 相似文献
1000.
Involvement of Cd Bioaccumulation in Spinal Deformities Occurrence in Natural Populations of Mediterranean Killifish 总被引:1,自引:0,他引:1
The aim of this study was to investigate the possible influence of environmental exposure to cadmium (Cd) on the spinal deformities
occurrence in the Mediterranean killifish, Aphanius fasciatus (Pisces: Cyprinodontidae). For this purpose, some indicators of skeletal bone mineralization, Cd, and calcium (Ca) concentrations
in spinal column as well as bioaccumulation of Cd from the water and the sediment have been compared in normal and deformed
fish collected from polluted (S1) and nonpolluted (S2) areas in the Gulf of Gabès in Tunisia. When compared to the normal
fish, the deformed fish showed signs of spinal column demineralization such as significant decrease in the ash weight/dry
weight ratio, percentage of nonorganic components content, and Ca concentration. Cd concentrations in spinal column and liver
were significantly higher in deformed fish than in normal fish. A highly significant negative correlation (r = −0.915, p < 0.01) between Cd and Ca concentrations was noted in spinal column of deformed fish. Bioaccumulation factors of Cd in the
liver from the water and the sediment in deformed fish were also significantly higher (p < 0.0001) than in normal fish from S1 and S2. These findings suggest that the ability to accumulate large amount of Cd may
represent a potential risk to induce spinal deformities in natural populations of Mediterranean killifish. 相似文献