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991.
992.
摘要:【目的】肺炎克雷伯菌(K.pn)与宿主细胞的粘附是致病的首要条件,粘附过程主要通过菌毛粘附素MrkD蛋白介导。为了进一步分析MrkD蛋白与宿主细胞间的粘附机制,进一步确定MrkD蛋白的粘附阻断作用。【方法】构建肺炎克雷伯菌菌毛粘附素融合蛋白原核表达质粒pGEX-4T-mrkD,转入大肠杆菌BL21,优化诱导表达条件,表达产物经亲和层析纯化、凝血酶切除融合蛋白GST标签后,进行SDS-PAGE和Western blot鉴定。激光共聚焦显微镜定位MrkD蛋白在宿主细胞上的结合部位;通过粘附活性试验与粘附动力学实验研究了MrkD蛋白的生物活性。【结果】实验得到了分子量为35 kDa的MrkD蛋白,定位了MrkD蛋白在宿主细胞上的结合部位,并证明了MrkD蛋白可以显著影响肺炎克雷伯菌对宿主细胞的粘附力。【结论】本试验首次证实了MrkD蛋白的粘附阻断作用并观察到了其与宿主细胞的作用位点,为研究肺炎克雷伯菌的致病机制,寻找粘附素功能表位奠定了基础。 相似文献
993.
Takashi Kitagawa Shingo Kimura Hideaki Nakata Harumi Yamada Akira Nitta Yoshikazu Sasai Hideharu Sasaki 《Environmental Biology of Fishes》2009,84(2):193-196
The habitat and movements of a Pacific bluefin tuna were investigated by reanalyzing archival tag data with sea surface temperature
data. During its trans-Pacific migration to the eastern Pacific, the fish took a direct path and primarily utilized waters,
in the Subarctic Frontal Zone (SFZ). Mean ambient temperature during the trans-Pacific migration was 14.5 ± 2.9 (°C ± SD),
which is significantly colder than the waters typically inhabited by bluefin tuna in their primary feeding grounds in the
western and eastern Pacific (17.6 ± 2.1). The fish moved rapidly through the colder water, and the heat produced during swimming
and the thermoconservation ability of bluefin tuna likely enabled it to migrate through the cold waters of the SFZ. 相似文献
994.
Toll-like receptor expression in normal ovary and ovarian tumors 总被引:1,自引:0,他引:1
Mingfu Zhou Molly M. McFarland-Mancini Holly M. Funk Nader Husseinzadeh Taofic Mounajjed Angela F. Drew 《Cancer immunology, immunotherapy : CII》2009,58(9):1375-1385
Recent studies have implicated inflammation in the initiation and progression of ovarian cancer, though the mechanisms underlying
this effect are still not clear. Toll-like receptors (TLRs) allow immune cells to recognize pathogens and to trigger inflammatory
responses. Tumor cell expression of TLRs can promote inflammation and cell survival in the tumor microenvironment. Here we
sought to characterize the expression of TLRs in normal human ovaries, benign and malignant ovarian tumors from patients,
and in established ovarian tumor cell lines. We report that TLR2, TLR3, TLR4, and TLR5 are strongly expressed on the surface
epithelium of normal ovaries. In contrast to previous studies of uterus and endocervix, we found no cyclic variation in TLR
expression occurred in murine ovaries. TLR2, TLR3, TLR4, and TLR5 are expressed in benign conditions, epithelial tumors, and
in ovarian cancer cell lines. Variable expression of TLR6 and TLR8 was seen in benign and malignant epithelium of some patients,
while expression of TLR1, TLR7, and TLR9 was weak. Normal and malignant ovarian stroma were negative for TLR expression. Vascular
endothelial cells, macrophages, and occasional fibroblasts in tumors were positive. Functional activity for TLRs was demonstrated
by stimulation of cell lines with specific ligands and subsequent activation and translocation of NFκB and release of the
proinflammatory cytokines interleukin-6 and CCL-2. These studies demonstrate expression of multiple TLRs in the epithelium
of normal ovaries and in ovarian tumor cells, and may indicate a mechanism by which epithelial tumors manipulate inflammatory
pathways to facilitate tumor progression. 相似文献
995.
Steffen Harzsch Carsten H. G. Müller Verena Rieger Yvan Perez Silvia Sintoni Christian Sardet Bill Hansson 《Zoomorphology》2009,128(1):53-73
The enigmatic arrow worms (Chaetognatha) are marine carnivores and among the most abundant planktonic organisms. Their phylogenetic
position has been heavily debated for a long time. Most recent molecular studies still provide a diverging picture and suggest
arrow worms to be some kind of basal protostomes. In an effort to understand the organization of the nervous system in this
clade for a broad comparison with other Metazoa we analysed the ultrastructure of the ventral nerve centre in Spadella cephaloptera by transmission electron microscopy. We were able to identify six different types of neurons in the bilateral somata clusters
by means of the cytoplasmic composition (regarding the structure of the neurite and soma including the shape and eu-/heterochromatin
ratio within the nucleus) as well as the size and position of these neurons. Furthermore, our study provides new insights
into the neuropil composition of the ventral nerve centre and several other fine structural features. Our second goal was
to examine if individually identifiable neurons are present in the ventral nerve centres of four chaetognath species, Sagitta setosa, Sagitta enflata, Pterosagitta draco, and Spadella cephaloptera. For that purpose, we processed whole mount specimens of these species for immunolocalization of RFamide-related neuropeptides
and analysed them with confocal laser-scanning microscopy. Our experiments provide evidence for the interspecific homology
of individual neurons in the ventral nerve centres of these four chaetognath species suggesting that the potential to generate
serially arranged neurons with individual identities is part of their ground pattern. 相似文献
996.
Chen-Xi Hu Hui Huang Li Zhang You Huang Zhu-Fang Shen Ke-Di Cheng Guan-Hua Du Ping Zhu 《Biotechnology letters》2009,31(7):979-984
Dipeptidyl peptidase (DPP) IV inhibitors provide a new strategy for the treatment of type 2 diabetes. Human DPP-IV gene was
cloned from differentiated Caco-2 cells and expressed in Pichia pastoris. The recombinant enzyme was used in a new system for screening of DPP-IV inhibitors. By high throughput screening, a novel
compound (W5188) was identified from 75,000 compounds with an IC50 of 6.5 μM. This method is highly reproducible and reliable for discovery of DPP-IV inhibitors as shown by Z′ value of 0.73
and S/N ratio of 6.89. 相似文献
997.
Microbial production of 2,3-butanediol from Jerusalem artichoke tubers by <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> 总被引:1,自引:0,他引:1
Li-Hui Sun Xu-Dong Wang Jian-Ying Dai Zhi-Long Xiu 《Applied microbiology and biotechnology》2009,82(5):847-852
2,3-Butanediol is one of the promising bulk chemicals with wide applications. Its fermentative production has attracted great
interest due to the high end concentration. However, large-scale production of 2,3-butanediol requires low-cost substrate
and efficient fermentation process. In the present study, 2,3-butanediol production by Klebsiella pneumoniae from Jerusalem artichoke tubers was successfully performed, and various technologies, including separate hydrolysis and fermentation
(SHF) and simultaneous saccharification and fermentation (SSF), were investigated. The concentration of target products reached
81.59 and 91.63 g/l, respectively after 40 h in batch and fed-batch SSF processes. Comparing with fed-batch SHF, the fed-batch
SSF provided 30.3% higher concentration and 83.2% higher productivity of target products. The results showed that Jerusalem
artichoke tuber is a favorable substrate for 2,3-butanediol production, and the application of fed-batch SSF for its conversion
can result in a more cost-effective process. 相似文献
998.
Raimondi S Roncaglia L De Lucia M Amaretti A Leonardi A Pagnoni UM Rossi M 《Applied microbiology and biotechnology》2009,81(5):943-950
Twenty-two strains of Bifidobacterium, representative of eight major species of human origin, were screened for their ability to transform the isoflavones daidzin
and daidzein. Most of the strains released the aglycone from daidzin and 12 gave yields higher than 90%. The kinetics of growth,
daidzin consumption, and daidzein production indicated that the hydrolytic activity occurred during the growth. The supernatant
of the majority of the strains did not release the aglycone from daidzin, suggesting that cell-associated β-glucosidases (β-Glu)
are mainly responsible for the metabolism of soybean glyco-conjugates. Cell-associated β-Glu was mainly intracellular and
significantly varied among the species and the strains. The lack of β-Glu was correlated with the inability to hydrolyze daidzin.
Although S-equol production by anaerobic intestinal bacteria has been established, information on S-equol-producing bifidobacteria
is contradictory. In this study, 22 bifidobacteria failed to transform daidzein into reduced metabolites under all the experimental
conditions, excluding any role in the reductive pathway of daidzein toward the production of S-equol. These results suggest
that selected probiotic strains of Bifidobacterium can be used to speed up the release of daidzein, improving its bioavailability for absorption by colonic mucosa and/or biotransformation
to S-equol by other intestinal microorganisms. 相似文献
999.
By Q. W. Wei B. Kynard D. G. Yang X. H. Chen H. Du L. Shen H. Zhang 《Zeitschrift fur angewandte Ichthyologie》2009,25(S2):100-106
A sampling system for capturing sturgeon eggs using a D-shaped bottom anchored drift net was used to capture early life stages (ELS) of Chinese sturgeon, Acipenser sinensis , and monitor annual spawning success at Yichang on the Yangtze River, 1996–2004, before and just after the Three Gorges Dam began operation. Captured were 96 875 ELS (early life stages: eggs, yolk-sac larvae = eleuthero embryos, and larvae); most were eggs and only 2477 were yolk-sac larvae. Most ELS were captured in the main river channel and inside the bend at the Yichang spawning reach. Yolk-sac larvae were captured for a maximum of 3 days after hatching began, indicating quick dispersal downstream. The back-calculated day of egg fertilization over the eight years indicated a maximum spawning window of 23 days (20 October–10 November). Spawning in all years was restricted temporally, occurred mostly at night and during one or two spawning periods, each lasting several days. The brief temporal spawning window may reduce egg predation by opportunistic predators by flooding the river bottom with millions of eggs. During 1996–2002, the percentage of fertilized eggs in an annual 20-egg sample was between 63.5 to 94.1%; however, in 2003 the percentage fertilized was only 23.8%. This sudden decline may be related to the altered environmental conditions at Yichang caused by operation of the Three Gorges Dam. Further studies are needed to monitor spawning and changes in egg fertilization in this threatened population. 相似文献
1000.
Ying Yang Zhenlong Wu Yue Chen Jian Qiao Mingyu Gao Jianmin Yuan Wei Nie Yuming Guo 《Biometals》2006,19(1):71-81
Magnesium deficiency and oxidative stress have been identified as correlative factors in many diseases. The origin of free
radicals correlated with oxidative damage resulting from Mg-deficiency is unclear at the cellular level. To investigate whether
hydrogen peroxide (H2O2) is associated in the oxidative stress induced by Mg-deficiency, the effect of Mg2+ deficiency (0, 0.4, 0.7 mM) on the metabolism of H2O2 was investigated in cultured chick embryo hepatocytes. After being cultured in the media with various concentrations of Mg2+ for 1, 2, 4, 6 and 10 days, parameters of H2O2 production, catalase activity, lipid peroxidation, intracellular total Mg and cell viability were analyzed. Results demonstrated
that long-term incubation of chick embryo hepatocyte in extracellular Mg2+-deprivative and Mg2+-deficient (0.4 mM) states significantly enhanced the production of H2O2 (approximately twofold, respectively) and lipid peroxidation in the cell cultures, while decreasing the cell viability. Additionally,
the reversing action of Mg2+ re-added to 1.0 mM and the partial reversing action of dimethylthiourea suggested that (i) [Mg2+]e deficiency induced the increase of H2O2 production, (ii) [Mg2+]e deficiency decreased catalase activity in chick embryo hepatocyte in vitro, subsequently causing oxidative stress and cell peroxidative damage. 相似文献