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排序方式: 共有45条查询结果,搜索用时 15 毫秒
1.
Fireblight disease, caused by Erwinia amylovora was first detected in Bulgaria on quince in the region of Plovdiv in 1989. The disease was initially localized in that area but, during 1995/1997, due to favourable climate conditions, it became epidemic. Infected trees were grubbed out and destroyed. The main hosts are quince and pear (over 40% of affected trees), then apple, medlar and Cotoneaster. Containment measures undertaken by the Bulgarian NPPO are laid down in the Plant Protection Law, in Phytosanitary Regulation no. 1 for phytosanitary control, and in Phytosanitary Regulation no. 5 of 1996 (amended 1997) for containment of fireblight. Phytosanitary control is mainly focused on fruit‐tree nurseries and on the distribution of healthy plants for planting. In 2003, 41 protected zones and 29 protected sectors within infested areas have been established. 相似文献
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Dmitri Andreev Thomas Rocheleau Thomas W. Phillips Richard W. Beeman Richard H. ûrench-Constant 《Pest management science》1994,41(4):345-349
A molecular diagnostic was used to examine the conservation of cyclodiene resistance associated mutations between different strains of Tribolium castaneum (Herbst.). An improved insecticide bioassay for discrimination between resistant genotypes was developed and seven resistant strains were established from five different continents. In order to develop a molecular diagnostic a partial cDNA of the cyclodiene insecticide resistance gene Rdl, a γ-aminobutyric-acid-gated chloride-ion channel, was cloned and sequenced. This cDNA spans exon 7, the region containing the resistance-associated mutation, and part of exon 8. An ‘allele-specific’ oligonucleotide primer, carrying the resistance-associated mutation at its 3′ end, was used in combination with a flanking ‘allele-independent’ primer in the polymerase chain reaction to selectively amplify a single resistance-associated mutation from all seven strains collected worldwide. The implications of these findings for the population genetics of insecticide resistance and its management in pest insects via quarantine are discussed. 相似文献
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DT Rodbell GO Seltzer DM Anderson MB Abbott DB Enfield JH Newman 《Science (New York, N.Y.)》1999,283(5401):516-520
Debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the Pacific Ocean, in Ecuador. These storm-induced events were dated by radiocarbon, and the age of laminae that are less than 200 years old matches the historic record of El Nino events. From about 15,000 to about 7000 calendar years before the present, the periodicity of clastic deposition is greater than or equal to 15 years; thereafter, there is a progressive increase in frequency to periodicities of 2 to 8.5 years. This is the modern El Nino periodicity, which was established about 5000 calendar years before the present. This may reflect the onset of a steeper zonal sea surface temperature gradient, which was driven by enhanced trade winds. 相似文献
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Tennessen JA Bigham AW O'Connor TD Fu W Kenny EE Gravel S McGee S Do R Liu X Jun G Kang HM Jordan D Leal SM Gabriel S Rieder MJ Abecasis G Altshuler D Nickerson DA Boerwinkle E Sunyaev S Bustamante CD Bamshad MJ Akey JM;Broad GO;Seattle GO;NHLBI Exome Sequencing Project 《Science (New York, N.Y.)》2012,337(6090):64-69
As a first step toward understanding how rare variants contribute to risk for complex diseases, we sequenced 15,585 human protein-coding genes to an average median depth of 111× in 2440 individuals of European (n = 1351) and African (n = 1088) ancestry. We identified over 500,000 single-nucleotide variants (SNVs), the majority of which were rare (86% with a minor allele frequency less than 0.5%), previously unknown (82%), and population-specific (82%). On average, 2.3% of the 13,595 SNVs each person carried were predicted to affect protein function of ~313 genes per genome, and ~95.7% of SNVs predicted to be functionally important were rare. This excess of rare functional variants is due to the combined effects of explosive, recent accelerated population growth and weak purifying selection. Furthermore, we show that large sample sizes will be required to associate rare variants with complex traits. 相似文献
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AIM: Our purpose was to induce MSCs differentiating into endothelial cells (EC) in vitro and to provide the seed cells for study of cardiovascular tissue-engineering. METHODS: MSCs were separated by gradient centrifugation on Percoll (density 1 073 g/L) from human bone marrow (HBM), and incubated for purification and amplification in DMEM (low glucose) with 10% fetal bovine serum (FBS). Then, the MSCs were incubated for orientation differentiated into EC in DMEM (high glucose) with 20% FBS, VEGF (10 μg/L), bFGF (5 μg/L), L-glutamine (2 mmol/L), penicillin (1×105U/L) and streptomycin (100 mg/L) for about 14-21 days and their phenotypic characteristics were analyzed by flow cytometry. Afterwards, the differentiating cells were evaluated by histology and immunohistochemistry. RESULTS: The quantity of MSCs was increased from 5.0×105 in the primary culture to 8.0×1012, or to increase to 1.6×107 times after 15 generations of incubation. The purity of MSCs was above 95% and 98% homogeneous at passages 2 and 3, respectively. About 80%-90% of the differentiating cells from MSCs after 14-21 days were positively stained for Ⅷ factor (vWF) related antigen by immunohistochemistry assay, and Weible-palade corpuscle was also observed by transmission electron microscopy in the cytoplasm. CONCLUSION: MSCs from HBM have the capability of differentiation into ECs in vitro, which may be a potential source of seed cells for fabrication of tissue-engineering heart valve, particularly in children with congenital heart disease. 相似文献