996 resultados para Rice sites


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With current gene-transfer techniques in fish, insertion of DNA into the genome occurs randomly and in many instances at multiple sites. Associated position effects, copy number differences, and multiple gene interactions make gene expression experiments difficult to interpret and fish phenotype less predictable. To meet different fish engineering needs, we describe here a gene targeting model in zebrafish. At first, four target zebrafish lines, each harboring a single genomic lox71 target site, were generated by zebrafish transgenesis. The zygotes of transgenic zebrafish lines were coinjected with capped Cre mRNA and a knockin vector pZklox66RFP. Site-specific integration event happened from one target zebrafish line. In this line two integrant zebrafish were obtained from more than 80,000 targeted embryos (integrating efficiency about 10(-4) to 10(-5)) and confirmed to have a sole copy of the integrating DNA at the target genome site. Genomic polymerase chain reaction analysis and DNA sequencing verified the correct gene target events where lox71 and lox66 have accurately recombined into double mutant lox72 and wild-type loxP. Each integrant zebrafish chosen for analysis harbored the transgene rfp at the designated egfp concatenates. Although the Cre-mediated recombination is site specific, it is dependent on a randomly placed target site. That is, a genomic target cannot be preselected for integration based solely on its sequence. Conclusively, an rfp reporter gene was successfully inserted into the egfp target locus of zebrafish genome by Cre-lox-mediated recombination. This site-directed knockin system using the lox71/lox66 combination should be a promising gene-targeting platform serving various purposes in fish genetic engineering.

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The rice field eel (Monopterus albus) is a fish of economic importance in China and some Asian countries. From a (GT)(n)-enriched genomic library, 30 microsatellites were developed by employing the fast isolation by AFLP of sequences containing repeats (FIASCO) protocol. Thirteen loci exhibited polymorphism with two to 13 alleles (mean 7.9 alleles/locus) in a test population and observed heterozygosity ranged from 0.3125 to 0.9688 (mean 0.7140). These loci should provide sufficient level of genetic variation to study the fine-scale population structure and reproductive ecology of the species.

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The objective of this study was to determine the effect of dietary vitamins A, D-3, E, and C on the gonad development, lipid peroxidation, and immune response of yearling rice field eel, Monopterus albus. A 6-wk feeding trial was designed according to an L-16(4(5)) orthogonal design, in which four vitamins, each at four supplementation levels, were arranged. Sixteen diets were mixed with the different vitamin levels and randomly assigned to 16 groups of fish. Increasing dietary vitamin E supplementation level significantly (P <= 0.05) increased the gonadosomatic index and lowered the serum content of malondialdehyde of rice field eel. Increasing dietary vitamin A and C levels also showed similar effect, but the differences were not statistically significant. Serum immunoglobulin M content increased significantly (P <= 0.01) as dietary vitamin C supplementation levels increased. The concentrations of calcium in bones showed significant (P <= 0.05) trend with vitamin D-3 and A supplementation levels, but the bone phosphorus content was not affected by the dietary vitamin levels.

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Microcystins are naturally occurring hepatotoxic cyclic heptapeptides produced by some toxic freshwater cyanobacterial species. In this study, crude extract of toxic cyanobacterial blooms from Dianchi Lake in southwestern China was used to determine the effects of microcystins on rape (Brassica napus L.) and rice (Oryza sativa L.). Experiments were carried out on a range of doses of the extract (equivalent to 0, 0.024, 0.12, 0.6 and 3 mug MC-LR/ml). Investigations showed that exposure to microcystins inhibited the growth and development of both rice and rape seedlings, however, microcystins had more powerful inhibition effect on rape than rice in germination percentage of seeds and seedling height. Microcystins significantly inhibited the elongation of primary roots of rape and rice seedlings. Determination of the activities of peroxidase and superoxide dismutase demonstrated that microcystin stress was manifested as an oxidative stress. Using ELISA, microcystins were examined from the extract of exposed rape and rice seedlings, indicating that consumption of edible plants exposed to microcystins via irrigation route may have health risks. Significantly different levels of recovered microcystins between exposed rice and rape seedlings Suggested that there might be different tolerant mechanisms toward microcystins. (C) 2004 Elsevier Ltd. All rights reserved.

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The contamination and distribution of polychlorinated dibeinizo-p-dioxins and dibenzofurans (PCDD/Fs) from two agricultural fields of a heavily polluted lake area in China (Ya-Er Lake) are presented. The vertical distribution pattern of total PCDD/Fs in soil cores reveals that the maximum concentration was in the layer of 20-30 cm. The concentrations in the top layer of soil at the two sites were similar (17.48 ng/kg at Site 1 and 18.10 ng/kg at Site 2), but the maximum concentration of Site 1 (120.8 ng/kg) was two times higher than that of Site 2 (64.39 ng/kg). The maximum concentration of PCDD/Fs in mud cores in rice fields (0-50 cm) at Sites 1 and 2 was in the layer of 0-10 cm. The maximum PCDD/F concentration in the top layer in mud at Site 1 (203.1 ng/kg) was higher than that at Site 2: (143.3 ng/kg). Significant correlations were found between the mind PCDD/Fs and the organic carbon content (R = 0.9743, P< 0,05 at Site 1; R = 0.9821, P< 0.05 at Site 2), the two variables being highly correlated (R = 0.9049, P< 0.05, at Site 1; R = 0.9916, P< 0.05 at Site 2). All correlation coefficients were significant at the 95% level. Concentrations were highly correlated with organic carbon, indicating that sorption to organic carbon was the dominant mechanism. Using principal component analysis, the homologue profiles of soil, mud, and plants (rice and radish) were compared. The PCDD/F patterns in plants were found not to be correlated to those in soil and mud. This suggests that atmospheric deposition may be the main source of PCDD/Fs in rice grain. However, mixed exposure involving uptake mechanisms and atmospheric deposition is considered main the source of PCDD/F pollution in radishes. (C) 2002 Elsevier Science (USA).

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After isolation from rice mitochondria still have activity and can live for a long time by using its stored nutrients. The thermogenesis curves of energy release of the mitochondria isolated from variant strains of rice have been determined by using an LKB2277 bioactivity monitor. The differences in shape of the curves and the thermodynamic and kinetic characteristics of the thermogenesis of the mitochondria have been compared. The thermodynamic and kinetic parameters of energy release of the mitochondria in the thermogenesis increasing stage have been calculated, and the experimental thermokinetic equations of the thermogenesis have been established. (C) 2001 Elsevier Science B.V. All rights reserved.

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The thermodynamic and kinetic behaviors of energy release of mitochondria isolated from rice (Oryza sative L.) were studied by using a LKB 2277 Bioactivity Monitor under different conditions. The thermogenesis curves of energy release of the rice mitochondria (which had been kept at 0-3 degreesC for 15 h and 40 day before the determination) were determined respectively at 25 and 30 degreesC, and the difference in shape of the thermogenesis curves and thermodynamic and kinetic characteristics were compared. The thermodynamic and kinetic parameters of energy release of the mitochondria in the thermogenesis increasing stage have been calculated, and the experimental thermokinetic equations of the thermogenesis have been established. The results indicated that the lower the temperature, the slower the energy release of the rice mitochondria. Both the thermogenesis and the energy release late of the rice mitochondria increased after the mitochondria was kept at lower temperature for 40 days. One can use the methods to characterize the ability of the rice mitochondria to release energy under different conditions. (C) 2001 Published by Elsevier Science B.V.

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As-grown Fe-doped semi-insulating InP single crystal has been converted into n-type low-resistance material after high temperature annealing. Defects in the InP materials have been studied by conventional Hall effect measurement, thermally stimulated current spectroscopy, deep level transient spectroscopy and X-ray diffraction respectively. The results indicate that Fe atoms in the InP material change from the substitutional to the interstitial sites under thermal activation. Consequently, the InP material loses its deep compensation centers which results in the change in types of conduction. The mechanism and cause of the phenomena have been analyzed through comparison of the sites of Fe atom occupation and activation in doping, diffusion and ion implantation processes of InP.

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A phenomenological model is proposed to explain quantitatively the interesting compositional dependence on the Ge incorporation rate during low-temperature growth of Si1-xGex by disilane and solid-Ge molecular beam epitaxy, based on enhanced hydrogen desorption from Si sites due to the presence of Ge atoms. The hydrogen desorption rate constant for disilane on Si sites is fitted to an exponential function of Ge incorporation rate and a possible physical explanation is discussed. Simulated results are in excellent agreement with experimental data. (C) 1999 American Institute of Physics. [S0021-8979(99)02109-X].

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