The impact of uptake, translocation and metabolism on the differential selectivity between blackgrass and wheat for the herbicide pyroxsulam     

DeBoer GJ  Thornburgh S  Gilbert J  Gast RE 《Pest management science》2011,67(3):279-286

BACKGROUND: Wheat shows selectivity to pyroxsulam, a new broad‐spectrum herbicide with high activity on blackgrass. Studies were performed to establish whether uptake, translocation or metabolism were responsible for the differential activity in wheat compared with blackgrass. In addition, the effect of the safener cloquintocet‐mexyl on metabolism was evaluated in wheat and blackgrass shoots. RESULTS: Root uptake of pyroxsulam in blackgrass was significantly higher than in wheat, suggesting a possible activity enhancement in blackgrass owing to root uptake. Translocation to foliage from root uptake as well as translocation out of treated foliage following foliar applications was low in wheat compared with blackgrass, likely owing to the rapid metabolism of pyroxsulam in wheat. Wheat metabolized pyroxsulam significantly faster than blackgrass to the less active O‐dealkylation product. Wheat shoots metabolized pyroxsulam faster when the safener cloquintocet‐mexyl was present, but cloquintocet‐mexyl did not increase the rate of metabolism in blackgrass. CONCLUSIONS: The selectivity of pyroxsulam to wheat relative to blackgrass was connected primarily with differences in the rate of metabolism and generation of an inactive metabolite. Metabolism in wheat restricted subsequent movement of radioactivity out of the treated leaf. The rapid metabolism in wheat was increased by the addition of cloquintocet‐mexyl. Copyright © 2010 Society of Chemical Industry  相似文献   

Theileria sergenti     

Uilenberg G 《Veterinary parasitology》2011,175(3-4):386

  相似文献   

Modeling shallow water table evaporation in irrigated regions     

Chuck Young  Wesley Wallender  Gerrit Schoups  Graham Fogg  Blaine Hanson  Thomas Harter  Jan Hopmans  Richard Howitt  Ted Hsiao  Sorab Panday  Ken Tanji  Susan Ustin  Kristen Ward 《Irrigation and Drainage Systems》2007,21(2):119-132

Groundwater discharge through evaporation due to a shallow water table can be an important component of a regional scale water balance. Modeling this phenomenon in irrigated regions where soil moisture varies on short time scales is most accurately accomplished using variably saturated modeling codes. However, the computational demands of these models limit their application to field scale problems. The MODFLOW groundwater modeling code is applicable to regional scale problems and it has an evapotranspiration package that can be used to estimate this form of discharge, however, the use of time-invariant parameters in this module result in evaporation rates that are a function of water table depth only. This paper presents a calibration and validation of the previously developed MOD-HMS model code using lysimeter data. The model is then used to illustrate the dependence of bare soil evaporation rates on water table depth and soil moisture conditions. Finally, an approach for estimating the time varying parameters for the MODFLOW evapotranspiration package using a 1-D variably saturated MOD-HMS model is presented.  相似文献   

Glycosylation of Conotoxins     

Gerrit J. Gerwig  Henry G. Hocking  Reto St?cklin  Johannis P. Kamerling  Rolf Boelens 《Marine drugs》2013,11(3):623-642

Conotoxins are small peptides present in the venom of cone snails. The snail uses this venom to paralyze and capture prey. The constituent conopeptides display a high level of chemical diversity and are of particular interest for scientists as tools employed in neurological studies and for drug development, because they target with exquisite specificity membrane receptors, transporters, and various ion channels in the nervous system. However, these peptides are known to contain a high frequency and variability of post-translational modifications—including sometimes O-glycosylation—which are of importance for biological activity. The potential application of specific conotoxins as neuropharmalogical agents and chemical probes requires a full characterization of the relevant peptides, including the structure of the carbohydrate part. In this review, the currently existing knowledge of O-glycosylation of conotoxins is described.  相似文献   

Low molecular weight melanoidins in coffee brew   总被引：1，自引：0，他引：1  

Bekedam EK  Roos E  Schols HA  Van Boekel MA  Smit G 《Journal of agricultural and food chemistry》2008,56(11):4060-4067

Analysis of low molecular weight (LMw) coffee brew melanoidins is challenging due to the presence of many non-melanoidin components that complicate analysis. This study focused on the isolation of LMw coffee brew melanoidins by separation of melanoidins from non-melanoidin components that are present in LMw coffee brew material. LMw coffee fractions differing in polarity were obtained by reversed-phase solid phase extraction and their melanoidin, sugar, nitrogen, caffeine, trigonelline, 5-caffeoylquinic acid, quinic acid, caffeic acid, and phenolic groups contents were determined. The sugar composition, the charge properties, and the absorbance at various wavelengths were investigated as well. The majority of the LMw melanoidins were found to have an apolar character, whereas most non-melanoidins have a polar character. The three isolated melanoidin-rich fractions represented 56% of the LMw coffee melanoidins and were free from non-melanoidin components. Spectroscopic analysis revealed that the melanoidins isolated showed similar features as high molecular weight coffee melanoidins. All three melanoidin fractions contained approximately 3% nitrogen, indicating the presence of incorporated amino acids or proteins. Surprisingly, glucose was the main sugar present in these melanoidins, and it was reasoned that sucrose is the most likely source for this glucose within the melanoidin structure. It was also found that LMw melanoidins exposed a negative charge, and this negative charge was inversely proportional to the apolar character of the melanoidins. Phenolic group levels as high as 47% were found, which could be explained by the incorporation of chlorogenic acids in these melanoidins.  相似文献   

Electron spin resonance (ESR) studies on the formation of roasting-induced antioxidative structures in coffee brews at different degrees of roast     

Bekedam EK  Schols HA  Cämmerer B  Kroh LW  van Boekel MA  Smit G 《Journal of agricultural and food chemistry》2008,56(12):4597-4604

The antioxidative properties of coffee brew fractions were studied using electron spin resonance spectroscopy using 2,2,6,6-tetramethyl-1-piperidin-1-oxyl (TEMPO) and Fremy's salt (nitrosodisulfonate) as stabilized radicals. TEMPO was scavenged by antioxidants formed during roasting and not by chlorogenic acid, whereas Fremy's salt was scavenged by all antioxidants tested including chlorogenic acid. The stabilized radical TEMPO allowed the exclusive measurement of roasting-induced antioxidants. The roasting-induced antioxidant activity of coffee brews increased with increasing degree of roast, and most of these antioxidants were formed during the initial roasting stage. The majority of these roasting-induced antioxidants were present in the high molecular weight fractions, indicating that the formation of these antioxidants preferably occurs at specific high molecular weight structures, likely being arabinogalactan and/or protein moieties which might be part of the melanoidin complex. It was found that chlorogenic acids most probably do not lose their antioxidant activity and phenolic characteristics upon incorporation in coffee melanoidins. The parameter fast reacting antioxidants (FRA) was introduced as an alternative for the antioxidative potential. FRA levels showed that coffee fractions rich in roasting-induced antioxidants exposed their antioxidant activity relatively slowly, which must be a consequence of its complex structure. Finally, the melanoidin content and the roasting-induced antioxidant activity showed a positive and linear correlation for the coffee brew fractions, showing that roasting-induced antioxidants are present within melanoidins. This is the first time that the formation of roasting-induced antioxidants could be directly correlated with the extent of Maillard reaction and melanoidin formation in a complex product such as coffee.  相似文献   

Urinary excretion of advanced glycation end products in dogs and cats     

Pornsucha Palaseweenun  Esther A. Hagen-Plantinga  J. Thomas Schonewille  Gerrit Koop  Claire Butre  Melliana Jonathan  Peter A. Wierenga  Wouter H. Hendriks 《Journal of animal physiology and animal nutrition》2021,105(1):149-156

The present study was conducted with privately owned dogs and cats to investigate whether a relationship exists between the dietary AGEs and the urinary excretion of AGEs, as indication of possible effective absorption of those compounds in the intestinal tract of pet carnivores. For this purpose, data were collected from both raw fed and dry processed food (DPF) fed to dogs and cats, through spot urine sampling and questionnaires. Raw pet food (RF, low in AGE diets) was fed as a primary food source to 29 dogs and DPF to 28 dogs. Cats were categorized into 3 groups, which were RF (n = 15), DPF (n = 14) and dry and wet processed pet food (DWF, n = 25). Urinary-free carboxymethyllysine (CML), carboxyethyllysine (CEL) and lysinoalanine (LAL) were analysed using ultrahigh-performance liquid chromatography (UHPLC)—mass spectrometry, and were standardized for variable urine concentration by expressing the AGE concentrations as a ratio to urine creatinine (Ucr) concentration (µg/µmol Ucr). Urinary excretion of CML, CEL and LAL in dogs fed with DPF was 2.03, 2.14 and 3 times higher compared to dogs fed with RF (p < .005). Similar to the dogs, a significant difference in CML:Ucr, CEL:Ucr and LAL:Ucr between the three diet groups was observed in cats (p-overall < 0.005, ANOVA), in which the RF fed group excreted less AGEs than the other groups. Linear regression coefficients and SE of CML:Ucr, CEL:Ucr and LAL:Ucr showed that body weight and neuter status were significantly correlated with CML and CEL excretion, but not to LAL excretion. Our results revealed a significant correlation between dietary AGEs and urinary excretion of free CML, CEL and LAL, and also showed that endogenous formation of these AGEs occurs in both dogs and cats under physiological conditions.  相似文献   

Application of the CSM-CERES-Maize model for planting date evaluation and yield forecasting for maize grown off-season in a subtropical environment   总被引：1，自引：0，他引：1  

Cecilia Manuela Tojo Soler  Paulo Csar Sentelhas  Gerrit Hoogenboom 《European Journal of Agronomy》2007,27(2-4):165-177

In recent years, maize has become one of the main alternative crops for the Autumn–Winter growing season (off-season) in several regions of Brazil. Water deficits, sub-optimum temperatures and low solar radiation levels are some of the more common problems that are experienced during this growing season. However, the impact of variable weather conditions on crop production can be analyzed with crop simulation models. The objectives of this study were to evaluate the Cropping System Model (CSM)-CERES-Maize for its ability to simulate growth, development, grain yield for four different maturity maize hybrids grown off-season in a subtropical region of Brazil, to study the impact of different planting dates on maize performance under rainfed and irrigated conditions, and for yield forecasting for the most common off-season production system. The CSM-CERES-Maize model was evaluated with experimental data collected during three field experiments conducted in Piracicaba, SP, Brazil. The experiments were completely randomized with three replications for the 2001 experiment and four replications for the 2002 experiments. For the yield forecasting application, daily weather data for 2002 were used until the forecast date, complemented with 25 years of historical daily weather data for the remainder of the growing season. Six planting dates were simulated, starting on February 1 and repeated every 15 days until April 15. The evaluation of the CSM-CERES-Maize showed that the model was able to simulate phenology and grain yield for the four hybrids accurately, with normalized RMSE (expressed in percentage) less than 15%. The planting date analysis showed that a delayed planting date from February 1 to April 15 caused a decrease in average yield of 55% for the rainfed and 21% for the irrigated conditions for all hybrids. The yield forecasting analysis demonstrated that an accurate yield forecast could be provided at approximately 45 days prior to the harvest date for all four maize hybrids. These results are promising for farmers and decision makers, as they could have access to accurate yield forecasts prior to final harvest. However, to be able to make practical decisions for stock management of maize grains, it is necessary to develop this methodology for different locations. Future model evaluations might also be needed due to the release of new cultivars by breeders.  相似文献   

DSSAT作物模型的统计和图形校验方法   总被引：2，自引：0，他引：2  

杨靖民  杨靖一 《植物营养与肥料学报》2012,18(5):1065-1074

本文以玉米, 大豆, 马铃薯和冬小麦试验为例, 详细讨论了DSSAT模型的统计校验和图形校验方法及其支持软件EasyGrapher的应用。结果指出: R2 不是理想的模型校验统计,因为它是测量线性回归y = + x + 的拟合度, 其随机误差建立在正态性、 相互独立和方差同质的假设之上。模型校验主要是检验残差di = yi-xi（y 为测量值, x为模拟值）,不是估计回归系数、 。RMSE、 E、 EF 和 d 都是比较好的校验模型残差的统计量, 它们不需要遵循回归模型的基本假设, 统计量的物理意义明确, 大样本容量下统计校验更为可靠。图形校验是模型校验必不可少的辅助工具,当有测量数据时,时间序列和残差校验图形是两种最基本的图形校验方法; 没有测量数据, 模拟图形仍然能够检验模型输出之间或与时间的动态关系, 辨析模拟误差或者错误。应用EasyGrapher 软件可以快速进行DSSAT模型的图形校验和统计校验。  相似文献   

Application of the CSM-CERES-Rice model for evaluation of plant density and irrigation management of transplanted rice for an irrigated semiarid environment     

Shakeel Ahmad  Ashfaq Ahmad  Hakoomat Ali  Abid Hussain  Axel Garcia y Garcia  Muhammad Azam Khan  Muhammad Zia-Ul-Haq  Mirza Hasanuzzaman  Gerrit Hoogenboom 《Irrigation Science》2013,31(3):491-506

The objectives of this study were to evaluate the performance of the Cropping System Model (CSM)-CERES (Crop-Environment Resource Synthesis)-Rice for simulating growth and yield of rice under irrigated conditions for a semiarid environment in Pakistan and to determine the impact of plant density and irrigation regime on grain yield and economic returns. The crop simulation model was evaluated with experimental data collected in 2000 and 2001 in Faisalabad, Punjab, Pakistan. The experiment utilized a randomized complete block design with three replications and included three plant densities (one seedling hill^?1, PD₁; two seedlings hill^?1, PD₂; and three seedlings hill^?1, PD₃) and five irrigation regimes (625 mm, I₁; 775 mm, I₂; 925 mm, I₃; 1075 mm, I₄; and 1225 mm, I₅). To determine the most appropriate combination of plant densities and irrigation regimes, four plant densities from one seedling hill^?1 to four seedlings hill^?1 and 17 irrigation regimes ranging from 0 to 1600 mm, for a total of 68 different scenarios, were simulated for 35 years of historical daily weather data. The evaluation of CSM-CERES-Rice showed that the model was able to accurately simulate growth and yield of rice for irrigated semiarid conditions, with an average error of 11% between simulated and observed grain yield. The results of the biophysical analysis showed that the combination of the two seedlings hill^?1 plant density and the 1,300 mm irrigation regime produced the highest yield compared to all other scenarios. Furthermore, the economic analysis through the Mean-Gini Dominance (MGD) also showed the superiority of this treatment compared to the other treatment combinations. The mean monetary return ranged from ?47 to 1,265 $ ha^?1 among all 68 scenarios. However, to be able to furnish the demand of rice grain for local consumption and to increase export, there is a need to expand this technology among the rice growers of other rice producing areas in Pakistan through extension workers.  相似文献