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31.
Weisz Randy Heiniger Ron White Jeffrey G. Knox Ben Reed Lonnie 《Precision Agriculture》2003,4(3):311-330
Variable rate (VR) fertilizer application is a paradigm with potential to improve input efficiency and farm profitability. It is widely marketed by commercial applicators in the southeastern US. However, field studies comparing VR with traditional management have not demonstrated consistent, positive results. The objectives of this study were: (1) to determine the soil impact, crop response and economic potential of VR phosphorus (P) and lime application in a North Carolina Piedmont no-till field crop system using intensive soybean [Glycine max (L.) Merr.] production and (2) to economically evaluate alternatives to standard commercial grid soil sampling for directing VR P and lime. A 23-ha long-term no-till field in the SE Piedmont was divided into 0.4ha plots assigned to either VR or uniform P and lime application. Grid soil sampling and VR P and lime application were done prior to four crops over 3 years: full season soybean, wheat (Triticum aestivum L.)–double cropped soybean, and full season soybean. Soil test P, pH and crop yield response to VR P were inconsistent. Soil pH in areas with low pH initially did increase in response to VR lime, but it took two to three applications to bring all of these areas to the target pH. Once VR-liming raised initially low soil pH to levels close to target, yield of soybean, but not wheat, were up to 0.74Mgha–1 higher than with uniform lime. Even with significantly higher soybean yields associated with VR lime, 3 years of grid sampling and VR application were not profitable compared to uniform application. The results indicated that VR lime could be profitable if the initial grid sampling data were used either for 2 consecutive years, or if it was used to restrict future grid sampling to specific areas requiring further VR lime. 相似文献
32.
Smith DJ Lapedes AS de Jong JC Bestebroer TM Rimmelzwaan GF Osterhaus AD Fouchier RA 《Science (New York, N.Y.)》2004,305(5682):371-376
The antigenic evolution of influenza A (H3N2) virus was quantified and visualized from its introduction into humans in 1968 to 2003. Although there was remarkable correspondence between antigenic and genetic evolution, significant differences were observed: Antigenic evolution was more punctuated than genetic evolution, and genetic change sometimes had a disproportionately large antigenic effect. The method readily allows monitoring of antigenic differences among vaccine and circulating strains and thus estimation of the effects of vaccination. Further, this approach offers a route to predicting the relative success of emerging strains, which could be achieved by quantifying the combined effects of population level immune escape and viral fitness on strain evolution. 相似文献
33.
Arkin IT Xu H Jensen MØ Arbely E Bennett ER Bowers KJ Chow E Dror RO Eastwood MP Flitman-Tene R Gregersen BA Klepeis JL Kolossváry I Shan Y Shaw DE 《Science (New York, N.Y.)》2007,317(5839):799-803
Na+/H+ antiporters are central to cellular salt and pH homeostasis. The structure of Escherichia coli NhaA was recently determined, but its mechanisms of transport and pH regulation remain elusive. We performed molecular dynamics simulations of NhaA that, with existing experimental data, enabled us to propose an atomically detailed model of antiporter function. Three conserved aspartates are key to our proposed mechanism: Asp164 (D164) is the Na+-binding site, D163 controls the alternating accessibility of this binding site to the cytoplasm or periplasm, and D133 is crucial for pH regulation. Consistent with experimental stoichiometry, two protons are required to transport a single Na+ ion: D163 protonates to reveal the Na+-binding site to the periplasm, and subsequent protonation of D164 releases Na+. Additional mutagenesis experiments further validated the model. 相似文献
34.
Kuiken T Rimmelzwaan G van Riel D van Amerongen G Baars M Fouchier R Osterhaus A 《Science (New York, N.Y.)》2004,306(5694):241
During the 2003 to 2004 outbreak of avian influenza A (H5N1) virus in Asia, there were anecdotal reports of fatal infection in domestic cats, although this species is considered resistant to influenza. We experimentally inoculated cats with H5N1 virus intratracheally and by feeding them virus-infected chickens. The cats excreted virus, developed severe diffuse alveolar damage, and transmitted virus to sentinel cats. These results show that domestic cats are at risk of disease or death from H5N1 virus, can be infected by horizontal transmission, and may play a role in the epidemiology of this virus. 相似文献
35.
36.
Expression cDNA cloning of the KGF receptor by creation of a transforming autocrine loop. 总被引:72,自引:0,他引:72
T Miki T P Fleming D P Bottaro J S Rubin D Ron S A Aaronson 《Science (New York, N.Y.)》1991,251(4989):72-75
An expression cloning strategy was devised to isolate the keratinocyte growth factor (KGF) receptor complementary DNA. NIH/3T3 fibroblasts, which secrete this epithelial cell-specific mitogen, were transfected with a keratinocyte expression complementary DNA library. Among several transformed foci identified, one demonstrated the acquisition of specific high-affinity KGF binding sites. The pattern of binding competition by related fibroblast growth factors (FGFs) indicated that this receptor had high affinity for acidic FGF as well as KGF. The rescued 4.2-kilobase complementary DNA was shown to encode a predicted membrane-spanning tyrosine kinase related to but distinct from the basic FGF receptor. This expression cloning approach may be generally applicable to the isolation of genes that constitute limiting steps in mitogenic signaling pathways. 相似文献
37.
Zdobnov EM von Mering C Letunic I Torrents D Suyama M Copley RR Christophides GK Thomasova D Holt RA Subramanian GM Mueller HM Dimopoulos G Law JH Wells MA Birney E Charlab R Halpern AL Kokoza E Kraft CL Lai Z Lewis S Louis C Barillas-Mury C Nusskern D Rubin GM Salzberg SL Sutton GG Topalis P Wides R Wincker P Yandell M Collins FH Ribeiro J Gelbart WM Kafatos FC Bork P 《Science (New York, N.Y.)》2002,298(5591):149-159
Comparison of the genomes and proteomes of the two diptera Anopheles gambiae and Drosophila melanogaster, which diverged about 250 million years ago, reveals considerable similarities. However, numerous differences are also observed; some of these must reflect the selection and subsequent adaptation associated with different ecologies and life strategies. Almost half of the genes in both genomes are interpreted as orthologs and show an average sequence identity of about 56%, which is slightly lower than that observed between the orthologs of the pufferfish and human (diverged about 450 million years ago). This indicates that these two insects diverged considerably faster than vertebrates. Aligned sequences reveal that orthologous genes have retained only half of their intron/exon structure, indicating that intron gains or losses have occurred at a rate of about one per gene per 125 million years. Chromosomal arms exhibit significant remnants of homology between the two species, although only 34% of the genes colocalize in small "microsyntenic" clusters, and major interarm transfers as well as intra-arm shuffling of gene order are detected. 相似文献
38.
Tietel Z Lewinsohn E Fallik E Porat R 《Journal of agricultural and food chemistry》2011,59(21):11779-11785
To elucidate the roles of ethanol fermentation metabolism in causing off-flavors, 'Mor' mandarins were exposed to anaerobic atmospheres for 0, 2, 4, 7, and 10 days to gradually increase juice ethanol and acetaldehyde levels through enhanced fermentation. Exposure to anaerobic atmosphere caused progressive decline in fruit sensory quality, from nearly "good" to "very bad", because of decreased typical mandarin flavor and increased sensation of 'musty' and 'ethanol' off-flavors. GC-MS analysis revealed significant (p ≤ 0.05) increases in the contents of 12 aroma volatiles, including the ethanol fermentation metabolites ethanol and acetaldehyde, and several fatty acid and amino acid catabolism derivates, 7 of which were ethyl esters, which suggests that they were esterification products of ethanol and acyl-CoA's derived from fatty acid and amino acid catabolism. These de novo synthesized anaerobiosis-regulated ethyl esters impart 'pungent', 'ethereal', 'waxy', 'musty', and 'fruity' notes. Overall, these results suggest that besides the direct effects of ethanol and acetaldehyde, downstream ethanol esterification products may also be involved in causing off-flavor sensation in mandarins. 相似文献
39.
Maria Fernanda de M. Costa Adriana K. Carmona Marcio F. M. Alves Timothy M. Ryan Helen M. Davies Garry A. Anderson Ron F. Slocombe 《Journal of veterinary science (Suw?n-si, Korea)》2011,12(1):21-25
Angiotensin-I converting enzyme (ACE) is a key regulator of blood pressure, electrolytes and fluid homeostasis through conversion of angiotensin I into angiotensin II. Recently, a genetic polymorphism of the ACE gene, which accounts for 47% of the variation of ACE activity in blood, has been advocated as a biomarker of athletic aptitude. Different methods of analysis and determination of ACE activity in plasma have been used in human and equine research without a consensus of a "gold standard" method. Different methods have often been used interchangeably or cited as being comparable in the existing literature; however, the actual agreement between assays has not been investigated. Therefore, in this study, we evaluated the level of agreement between three different assays using equine plasma obtained from 29 horses. Two spectrophotometric assays using Furylacryloyl-phenylalanyl-glycyl-glycine as substrate and one fluorimetric assay utilizing o-aminobenzoic acid-FRK-(Dnp)P-OH were employed. The results revealed that the measurements from the different assays were not in agreement, indicating that the methods should not be used interchangeably for measurement of equine ACE activity. Rather, a single method of analysis should be adopted to achieve comparable results and critical appraisal of the literature is needed when attempting to compare results obtained from different assays. 相似文献
40.
Antonio M. De Ron María C. Menéndez-Sevillano Marta Santalla 《Genetic Resources and Crop Evolution》2005,51(8):883-894
The phenotypic variation found in four common bean (Phaseolus vulgaris L.) complex primitive landraces, among a group of accessions collected in Northwestern Argentina in several missions is described, with particular attention to the wide diversity found in some small areas. It is presented a hypothesis about the maintenance of such diversity in bean mixtures or complex primitive landraces that grow close to their wild relative. Wide diversity regarding to seed type and plant characteristics was displayed by the landraces MCM-SV (composed of 11 lines), MCM-292 (14 lines), MCM-298 (5 lines) and VAV-3716 (14 lines). Food uses of dry seed and fresh pod seemed to be more relevant than the aesthetic use although all of them were presumably considered by humans for centuries resulting in the current phenotypes of these complex primitive landraces. Additionally, some weedy types (intermediate between wild and domesticated types) were detected in the landracesMCM-292 and MCM-298. The four complex landraces described consisted of highly diverse mixtures and they could play a role in breeding to enlarge the genetic basis of domesticated bean varieties belonging to the Andean gene pool. 相似文献