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排序方式: 共有298条查询结果,搜索用时 31 毫秒
81.
Gstaiger M Luke B Hess D Oakeley EJ Wirbelauer C Blondel M Vigneron M Peter M Krek W 《Science (New York, N.Y.)》2003,302(5648):1208-1212
Prefoldins (PFDs) are members of a recently identified, small-molecular weight protein family able to assemble into molecular chaperone complexes. Here we describe an unusually large member of this family, termed URI, that forms complexes with other small-molecular weight PFDs and with RPB5, a shared subunit of all three RNA polymerases. Functional analysis of the yeast and human orthologs of URI revealed that both are targets of nutrient signaling and participate in gene expression controlled by the TOR kinase. Thus, URI is a component of a signaling pathway that coordinates nutrient availability with gene expression. 相似文献
82.
83.
Coding properties of 7-methylguanine 总被引:5,自引:0,他引:5
The abnormal base, 7-methylguanine, has been introduced into copolymers of uridylic and guanylic acids by methylation under controlled conditions. The resulting methylated copolymers have a markedly decreased template activity for polypeptide synthesis in vitro due to steric effects of the 7-methyl groups. Contrary to expectation, these polymers do not permit incorporation of amino acids whose codons contain the bases uracil and adenine. 相似文献
84.
85.
The objectives of the current studies included the characterization of the temporal changes in indices of folate status and amino acid concentrations during both folate depletion and repletion phases. In trial 1, a 6 week folate depletion protocol was employed, using 60 weanling rats assigned to receive an amino acid-defined diet with or without 1 mg/kg folic acid. A 4 week folate depletion period was judged to be optimal on the basis of the development of nadirs in both plasma and hepatic folate stores and elevated (>6-fold relative to folate-adequate controls) concentrations of plasma homocysteine and glycine. In trial 2, 54 weanling rats, previously maintained on a folate-devoid diet for 4 weeks, were assigned to receive 0.25 mg/kg folate as either crystalline folic acid or folate from a folate-enriched egg yolk powder. Both forms of folate supported similar rates of gain, increases in plasma and hepatic folate stores, and reductions in plasma glycine concentrations, whereas the folate in egg yolk powder lowered plasma homocysteine concentrations further than the crystalline folic acid (P < 0.05). These data support the use of both plasma glycine and homocysteine as sensitive response criteria for folate status in a rat bioassay of folate depletion and repletion and establish appropriate temporal end-points for such studies. 相似文献
86.
Improving current cultural practices often involves more precise timing of the management activity based on crop development. Using crop simulation models to predict crop development and phenology has several problems. First, most existing models do not simulate sufficient developmental and phenological detail required to optimize selected management practices. Second, crop models normally emphasize the cultivars and conditions for the region in which they were developed, and may not generate satisfactory results when applied in new regions. Lastly, when users apply these models to new regions they often lack the specific data and knowledge of the model to adequately determine the crop parameters. Our objective was to assess whether the simulation model SHOOTGRO 4.0, which had the necessary level of developmental and phenological detail required for use as a management decision aid, could be easily and adequately parameterized to simulate winter wheat phenology and grain yield in the Czech Republic. We found that only a few parameters from the generic winter wheat cultivar used for the Central Great Plains in the USA needed to be changed, and the information needed to determine these few parameters were readily obtainable. The result was that the dates of anthesis and physiological maturity and final grain yield were predicted well at sites within the three major crop production regions of the Czech Republic. Sensitivity analysis also showed that the most sensitive management practices and initial conditions in SHOOTGRO are relatively easy to determine (e.g. sowing date, N fertilizer rate and timing, daily temperature), while it is not overly sensitive to those variables more difficult to determine (e.g. initial soil water in the profile). Based on this study, farmers and scientists needing wheat development information to increase the efficacy of their management practices can use SHOOTGRO 4.0 as a tool. 相似文献
87.
优化灌溉与施肥对冬小麦冠层结构的影响研究 总被引:5,自引:0,他引:5
试验研究优化灌溉与施肥对冬小麦冠层结构的影响结果表明,与限量灌溉处理相比,优化灌溉和传统灌溉处理小麦最上部3个节间明显伸长,导致株高增高10cm,旗叶叶面积减小7%,但倒2叶和倒3叶叶面积分别增加7%和20%;优化灌溉处理小麦旗叶茎叶夹角明显减小。与未施N肥处理相比,施用N肥有增大小麦株高、叶面积和茎叶夹角的趋势,且传统施N比优化施N更加明显。优化水N管理麦田各层次透光率与传统处理差异较小,但它们均显著低于限量灌溉和未施N处理。 相似文献
88.
R. G. Wilhelm D. C. Martens D. L. Hallock E. R. Collins Jr. E. T. Kornegay 《Water, air, and soil pollution》1980,14(1):443-450
This investigation was conducted to determine the elemental composition of effluents from three anaerobic swine waste lagoons and one aerobic swine waste lagoon and to evaluate effects of effluent application on growth of corn (Zea mays L.) Wide variation occurred in the elemental composition of effluents among the four lagoons and among four sampling dates from each lagoon. Use of these effluents as irrigation water would lead to application of a wide range in amounts of nutrients to soil. Effluent application increased corn grain yield on a Woodstown loamy fine sand. This yield increase was attributed to alleviation of moisture stress and to correction of N deficiency. 相似文献
89.
Jürgen Harlizius Dr. Med. Vet. Christoph Kluczniok DVM Wilhelm Bollwahn Dr. Med. Vet. Prof. 《Veterinary radiology & ultrasound》1997,38(6):421-423
Middle and inner ear infections have been reported as a clinical entity in swine, other animal species and humans. In pigs, the anatomical-pathological and microbiological findings have been described. In this report, we describe radiographic findings in affected pigs. A total of 25 pigs with a head tilt and circling, as clinical signs of otitis media and interna, were examined. The majority were weaner-pigs with dyspnea or rhinitis. In radiographs, there was an increased opacity of the bulla tympanica, often accompanied by marginal destruction or thickening of the bulla wall. The radiographic findings confirmed the clinical diagnosis in each affected pig, but there were 5 false positive interpretations. 相似文献
90.
Influence of winter wheat grown continuously on grain yield, foot rot infection and nematodes compared with winter wheat in rotation
The field trial, started in 1968 at the experimental-station in Rauischholzhausen, was intended to give informations about winter wheat in continuous cultivation. The question was if intensification of growing culture enables monoculture wheat to yield as high as winter wheat in rotation (sugar-beet, winter wheat, spring barley). Influence of green manuring with additional nitrogen, straw manuring with additional nitrogen, straw burning and fungicid treatment against eyespot was investigated.
The following results have been obtained in the years 1969 to 1985:
1. In the 17 years average winter wheat in rotation yielded with 50.1 dt/ha a higher amount of grain dry weight than wheat in monoculture (43.6 dt/ha). Only in 3 years wheat in monoculture reaches the grain yield level of wheat in rotation.
2. The incidence of Pseudocercosporella herpotrichoides was in wheat after wheat about 10% higher than in wheat after sugar-beets.
3. The use of fungicides against culm base diseases caused in monoculture an increase in yield of about 2.7 dt/ha which was not higher than in rotation (+2.5 dt/ha).
4. The first 12 years indicated a decline-effect with continuously decreasing differences in the yield of wheat in monoculture compared with rotation. But until the 17th year of the trial grain yield differences were as high as in the beginning.
It is not possible either by means of intensification of fertilizing or chemical plant protection treatment to reach the grain yield level of winter wheat in rotation with winter wheat in monoculture. Even the use of modern agronomical methodes remains crop rotation as a central part of an effective plant culture. 相似文献
The field trial, started in 1968 at the experimental-station in Rauischholzhausen, was intended to give informations about winter wheat in continuous cultivation. The question was if intensification of growing culture enables monoculture wheat to yield as high as winter wheat in rotation (sugar-beet, winter wheat, spring barley). Influence of green manuring with additional nitrogen, straw manuring with additional nitrogen, straw burning and fungicid treatment against eyespot was investigated.
The following results have been obtained in the years 1969 to 1985:
1. In the 17 years average winter wheat in rotation yielded with 50.1 dt/ha a higher amount of grain dry weight than wheat in monoculture (43.6 dt/ha). Only in 3 years wheat in monoculture reaches the grain yield level of wheat in rotation.
2. The incidence of Pseudocercosporella herpotrichoides was in wheat after wheat about 10% higher than in wheat after sugar-beets.
3. The use of fungicides against culm base diseases caused in monoculture an increase in yield of about 2.7 dt/ha which was not higher than in rotation (+2.5 dt/ha).
4. The first 12 years indicated a decline-effect with continuously decreasing differences in the yield of wheat in monoculture compared with rotation. But until the 17th year of the trial grain yield differences were as high as in the beginning.
It is not possible either by means of intensification of fertilizing or chemical plant protection treatment to reach the grain yield level of winter wheat in rotation with winter wheat in monoculture. Even the use of modern agronomical methodes remains crop rotation as a central part of an effective plant culture. 相似文献