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921.
Zhang X Chen W Zhang Y Jiang L Chen Z Wen Y Li J 《Journal of industrial microbiology & biotechnology》2012,39(6):917-925
Streptomyces avermitilis is an industrially important soil bacterium known for production of avermectins, which are antiparasitic agents useful in animal health care, agriculture, and treatment of human infections. ku genes play a key role in the non-homologous end-joining pathway for repair of DNA double strand breaks. We identified homologs of eukaryotic ku70 and ku80 genes, termed ku1 and ku2, in S. avermitilis. Mutants with deletion of ku1, ku2, and both genes were constructed and their phenotypic changes were characterized. Deletion of ku genes had no apparent adverse effects on growth, spore formation, or avermectin production. The ku mutants, in comparison to wild-type strain, were slightly more sensitive to the DNA-damaging agent ethyl methanesulfonate, but not to UV exposure or to bleomycin. Gene targeting frequencies by homologous recombination were higher in the ku mutants than in wild-type strain. We conclude that ku-deleted strains will be useful hosts for efficient gene targeting and will facilitate functional analysis of genes in S. avermitilis and other industrially important bacterial strains. 相似文献
922.
Ge H Tollner TL Hu Z Dai M Li X Guan H Shan D Zhang X Lv J Huang C Dong Q 《Molecular reproduction and development》2012,79(6):392-401
Mitochondrial metabolic capacity and DNA replication have both been shown to affect oocyte quality, but it is unclear which one is more critical. In this study, immature oocytes were treated with FCCP or ddC to independently inhibit the respective mitochondrial metabolic capacity or DNA replication of oocytes during in vitro maturation. To differentiate their roles, we evaluated various parameters related to oocyte maturation (germinal vesicle break down and nuclear maturation), quality (spindle formation, chromosome alignment, and mitochondrial distribution pattern), fertilization capability, and subsequent embryo developmental competence (blastocyst formation and cell number of blastocyst). Inhibition of mitochondrial metabolic capacity with FCCP resulted in a reduced percent of oocytes with nuclear maturation; normal spindle formation and chromosome alignment; evenly distributed mitochondria; and an ability to form blastocysts. Inhibition of mtDNA replication with ddC has no detectable effect on oocyte maturation and mitochondrial distribution, although high-dose ddC increased the percent of oocytes showing abnormal spindle formation and chromosome alignment. ddC did, however, reduce blastocyst formation significantly. Neither FCCP nor ddC exposure had an effect on the rate of fertilization. These findings suggest that the effects associated with lower mitochondrial DNA copy number do not coincide with the effects seen with reduced mitochondrial metabolic activity in oocytes. Inhibiting mitochondrial metabolic activity during oocyte maturation has a negative impact on oocyte maturation and subsequent embryo developmental competence. A reduction in mitochondrial DNA copy number, on the other hand, mainly affects embryonic development potential, but has little effect on oocyte maturation and in vitro fertilization. 相似文献
923.
A 1,474-bp stress-inducible CdDREBa promoter was identified from Chrysanthemum dichrum, revealing several candidate stress-related cis-acting elements (MYC-box, MYB site, GT-1, and W-box) within it. In Arabidopsis leaf tissues transformed with a CdDREBa promoter-β-glucuronidase (GUS) gene fusion, serially 5'-deleted CdDREBa promoters were differentially activated by cold and salinity. Histochemical and quantitative assays of GUS expression allowed us to localize a critical part of the promoter located between upstream 430 and 351 nt. This 80-bp fragment enhanced GUS expression under salinity stress when fused to -90/+8 CaMV 35S minimal promoter. Further promoter internal-deletion assays indicated that a low temperature-responsive element was located between positions -430 and -390, and a salinity inducible one between -385 and -351. Our results showed that there was a novel stress-related critical region except for the known cis-acting element (MYC-box, GT-1) in CdDREBa promoter. 相似文献
924.
Hao-Qi Wang Zhong Yao Zhi Zhou Yun Sun Ping Wei Pingkai Ouyang 《Biotechnology and Bioprocess Engineering》2012,17(6):1135-1139
Theanine, a unique amino acid found in tea plants, has many important physiological functions. Theanine can be enzymatically synthesized via the γ-glutamyltranspeptidation reaction. In this study, we described a new method of theanine synthesis using the L-glutamine-Zn(II) (Zn(Gln)2) complex instead of glutamine as the donor, which successfully reduced the side autotranspeptidation reaction and led to higher yield of theanine. We prepared the Zn(Gln)2 complexes and showed that they are stable in liquid bulk under 9.0 pH. After using the Zn(Gln)2 in the γ-glutamyltranspeptidation reaction, we utilized HPLC and Mass spectrometry analysis to demonstrated that Zn(Gln)2 was an more effective γ-glutamyl donor than glutamine. The autotranspeptidation reaction was restrained effectively. As a result, the theanine yield and the conversion rate for glutamine were vastly improved. In a reaction mixture containing 48 mM of Zn(Gln)2, 1.6 M ethylamine, and 0.5 U/mL GGT, the final concentration of theanine obtained was 61.3 mM after incubation at 37°C for three hours. The conversion rate for glutamine was 63.8%, which showed a 16.9% increase as compared to when using glutamine alone as the donor substrate. 相似文献
925.
Hai-Yan Chen Yue-Feng Guan Xue-Yong Huang Yu-Ting Wu Fen-Fei Wang Ju-Fang Gao Que Zhou Zhong-Nan Yang Jia-Yao Liu Hong-Xia Zhang 《Journal of Plant Biology》2012,55(3):209-217
We have characterized a new male-sterile mutant in Arabidopsis that exhibits conditional sterility but has restored fertility when drought-stressed. This mutant, multiple impairments in male reproduction 1 (mimr1), shows pleiotropic defects in both vegetative and reproductive development. Examination with dissecting and scanning electron
microscopes revealed that its pollen grains are not effectively released from the anther locule after dehiscence, and anther
differentiation is defective. Growth of the style and stamen filaments are also abnormal. Histological analysis demonstrated
that these phenomena are due not only to a noticeably reduced extension of the stamen but also greater elongation of the pistil.
Genetic analysis indicated that mimr1 is a single locus recessive nuclear mutant. The mutation can be mapped to a locus strongly linked to a 1200-kb region on
Chromosome 3. Meta-analysis of expression patterning presented several candidate genes in that region. No mutants with similar
phenotypes have previously been reported, suggesting that mimr1 is a novel male-sterile locus. Characterization of MIMR1 will provide further insights into the molecular basis for the development of plant reproductive organs. 相似文献
926.
The following study provides new insight into how surface topography dictates directed collective epithelial cell sheet growth through the guidance of individual cell movement. Collective cell behavior of migrating human corneal limbal-epithelial cell sheets were studied on highly biocompatible flat and micro-patterned silk film surfaces. The silk film edge topography guided the migratory direction of individual cells making up the collective epithelial sheet, which resulted in a 75% increase in total culture elongation. This was due to a 3-fold decrease in cell sheet migration rate efficiency for movement perpendicular to the topography edge. Individual cell migration direction is preferred in the parallel approach to the edge topography where localization of cytoskeletal proteins to the topography’s edge region is reduced, which results in the directed growth of the collective epithelial sheet. Findings indicate customized biomaterial surfaces may be created to direct both the migration rate and direction of tissue epithelialization. 相似文献
927.
Zhiwei Wang Lijuan Zhang Zhi Guo Lei Liu Jun Ji Jianian Zhang Xuehua Chen Bingya Liu Jun Zhang Qiulan Ding Xuefeng Wang Wei Zhao Zhenggang Zhu Yingyan Yu 《PloS one》2012,7(11)
Iron deficiency anemia is an extra-stomach disease experienced in H. pylori carriers. Individuals with type A blood are more prone to suffering from H. pylori infection than other individuals. To clarify the molecular mechanisms underlying H. pylori-associated anemia, we collected erythrocytes from A, B, O, and AB blood donors and analyzed morphology, the number of erythrocytes with H. pylori colonies attached to them, and iron contents in erythrocytes and H. pylori (NCTC11637 and SS1 strains) by means of optical microscopy, scanning electron microscopy, and synchrotron radiation soft X-ray imaging. The number of type A erythrocytes with H. pylori attached to them was significantly higher than that of other erythrocytes (P<0.05). Far more iron distribution was observed in H. pylori bacteria using dual energy analysis near the iron L2, 3 edges by soft X-ray imaging. Iron content was significantly reduced in host erythrocytes after 4 hours of exposure to H. pylori. H. pylori are able to adhere more strongly to type A erythrocytes, and this is related to iron shift from the host to the bacteria. This may explain the reasons for refractory iron deficiency anemia and elevated susceptibility to H. pylori infection in individuals with type A blood. 相似文献
928.
Standardization on Shear wave ultrasound elastography (SWUE) technical settings will not only ensure that the results are accurate, but also detect any differences over time that may be attributed to true physiological changes. The present study evaluated the variations of elastic modulus of muscle and tendon using SWUE when different technical aspects were altered. The results of this study indicated that variations of elastic modulus of muscle and tendon were found when different transducer's pressure and region of interest (ROI)'s size were applied. No significant differences in elastic modulus of the rectus femoris muscle and patellar tendon were found with different acquisition times of the SWUE sonogram. The SWUE on the muscle and tendon should be performed with the lightest transducer's pressure, a shorter acquisition time for the SWUE sonogram, while measuring the mean elastic modulus regardless the ROI's size. 相似文献
929.
930.
Ou Wang Chunyan Wang Min Nie Quancai Cui Heng Guan Yan Jiang Mei Li Weibo Xia Xunwu Meng Xiaoping Xing 《PloS one》2012,7(9)