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101.
Thompson HJ Heimendinger J Gillette C Sedlacek SM Haegele A O'neill C Wolfe P 《Journal of agricultural and food chemistry》2005,53(15):6126-6132
It is well established that vegetables and fruit (VF) contain antioxidant phytochemicals. Consequently, it is expected that individuals who consume diets with a high content of VF should be better protected against oxidative cellular damage than individuals who do not, but not all data support this assumption. The objective of this study was to identify possible explanations for this conundrum. The effects of two diets that differed in VF content on markers of oxidative damage were studied. Sixty-four women participated in a 14-day dietary intervention. Subjects consumed on average either 3.6 or 12.1 servings of VF per day. The primary end points assessed were 8-hydroxy-2-deoxyguanosine (8-oxo-dG) in peripheral lymphocyte DNA and 8-isoprostaglandin F-2alpha (8-iso-PGF2alpha) excreted in urine. Subjects consuming the high versus low VF diet had lower concentrations of 8-oxo-dG (p < 0.01) and of 8-iso-PGF2alpha (p < 0.01). However, the reduction in oxidative end points by high VF was not uniform. Rather, an antioxidant effect was observed primarily in individuals whose oxidative end points at baseline were above the median for the study population. Using change in plasma carotenoids (end point minus baseline measurements) as an index of phytochemical intake, the reduction in oxidative markers was inversely proportional to change in plasma carotenoids; this effect was stronger for lipid peroxidation (p < 0.01) than DNA oxidation (p < 0.05). These findings imply that increasing exogenous antioxidant exposure may primarily benefit individuals with elevated levels of oxidative stress. Null findings do not necessarily indicate that an antioxidant compound lacks in vivo activity. 相似文献
102.
D. J. Baumgartner E. P. Glenn T. L. Thompson B. A. Skeen 《Water, air, and soil pollution》2005,162(1-4):219-228
Arid land and riparian plants were irrigated with a liquid wastewater stream (centrate) from biosolids production at a municipal sewage treatment facility. Centrate containing approximately 1000 mg/l ammonia nitrogen was diluted with Tucson city tap water to provide treatments of 2.5, 5, 10, 25, 50, and 100% centrate, along with a dilution water control. Plants grown in 19-l containers in a greenhouse were irrigated daily with 6.7 l of solution over a 7-week period. All species exhibited a fertilizing effect at concentrations up to 5 and 10% centrate, equivalent to approximately 50 and 100 mg/l NH3–N, but then inhibitory above 100 mg/l. No plants survived on the 50 or 100% treatments. If centrate were to be diverted from the wastewater facility to be disposed of on the land, it was estimated that the total nitrogen content of the biosolids produced by the plant would be reduced by 11%. This reduction would have only a small impact on the value of the biosolids for soil amendment applications. 相似文献
103.
Quantification of seasonal sediment and phosphorus transport dynamics in an agricultural watershed using radiometric fingerprinting techniques 总被引:1,自引:0,他引:1
Natalie L. H. Huisman K. G. Karthikeyan Jasmeet Lamba Anita M. Thompson Graham Peaslee 《Journal of Soils and Sediments》2013,13(10):1724-1734
Purpose
Phosphorus (P) is a limiting nutrient for most US Midwestern aquatic systems and, therefore, increases of P, through point or non-point sources (NPS) of pollution such as agriculture, causes eutrophication. Identifying specific NPS contributions (e.g., upland vs. stream channels) for sediments and P is difficult due to the distributed nature of the pollution. Therefore, studies which link the spatial and temporal aspects of sediment and P transport in these systems can help better characterize the extent of NPS pollution.Materials and methods
Our study used fingerprinting techniques to determine sources of sediments in an agricultural watershed (the North Fork of the Pheasant Branch watershed; 12.4 km2 area) in Wisconsin, USA, during the spring, summer, and fall seasons of 2009. The primary sources considered were uplands (cultivated fields), stream bank, and streambed. The model used fallout radionuclides, 137Cs, and 210Pbxs, along with total P to determine primary sediment sources. A shorter-lived fallout radioisotope, 7Be, was used to determine the sediment age and percent new sediments in streambed and suspended sediment samples (via the 7Be/210Pbxs ratio).Results and discussion
Upland areas were the primary source of suspended sediments in the stream channels followed by stream banks. The sediment age and percent new sediment for the streambed and suspended sediments showed that the channel contained and transported newer (or more recently tagged with 7Be) sediments in the spring season (9–131 days sediment age), while relatively old sediments (165–318 days) were moving through the channel system during the fall season.Conclusions
Upland areas are the major contributors to in-stream suspended sediments in this watershed. Sediment resuspension in stream channels could play an important role during the later part of the year. Best management practices should be targeted in the upland areas to reduce the export of sediments and sediment-bound P from agricultural watersheds. 相似文献104.
D B Prelusky R M Hamilton B C Foster H L Trenholm B K Thompson 《Journal of the Association of Official Analytical Chemists》1987,70(6):1049-1055
The optimization of a simple, sensitive procedure using a chick embryotoxicity screening test (CHEST) bioassay for detection of toxic compounds is presented. Dosing protocols of eggs, using several mycotoxins (aflatoxin B1, deoxynivalenol, T-2 toxin) and appropriate controls, were evaluated for embryonic sensitivity, overall practicality of the procedure, and consistency of results. It was found that both type of carrier solvent and volume injected could significantly affect overall embryonic mortality. The chick embryo was most sensitive to the effects of toxins and solvents after 1 or 2 days of incubation; a rapid decrease in response was observed as the age of the embryo at dosing increased. Following administration of the toxins just below the shell membrane by way of a small hole (less than 0.5 mm diameter) punched in the shell, a good dose-response (% mortality) could be obtained regardless of the site of injection (except directly into the yolk), although dosing via the air sac position resulted in a slightly better statistical outcome. Although some variations in calculated LD50 values were found among repeated assays, statistical analyses showed that the differences were not due to dosing protocol but to the variations in embryo sensitivities among batches of eggs. Thus, if standard reference toxins for comparison are run concurrently, the CHEST assay can prove to be a very satisfactory model, as well as having considerable flexibility to be adapted to the needs and resources of many laboratories. 相似文献
105.
The values of length of synodic month, obtained from tidally controlled periodical growth patterns in mollusks and stromatolites for several geologic periods, indicate that the deceleration rate of the earth's rotation has not been constant. Two breaks in slope, in the Pennsylvanian and Cretaceous, may be related to changes in distribution of continents, oceans, and adjacent shallow seas. 相似文献
106.
J N Thompson 《Journal of the Association of Official Analytical Chemists》1986,69(5):727-738
The official methods for measuring vitamin A and carotene in foods and feeds have evolved over several decades. New procedures are needed to permit the use of modern analytical techniques such as liquid chromatography (LC), and to expand the application of official methods to a wide variety of foods. Recent improvements in methodology are reviewed. Emphasis is often placed on the separations achieved by LC, but all factors that affect quantitation, such as sampling, preparation of standards, and protection of the vitamin against oxidation, must be considered in the development of new methods. Many approaches to analysis are possible because of the versatility of LC but not all of them can be used in official methods. Methods for milk, margarine, and feeds can be prepared now for collaborative assays. Although straightforward methods can be developed for the measurement of beta-carotene in certain foods, a full examination of provitamins will probably continue to require a flexible approach and special expertise. 相似文献
107.
Production and water use in lettuces under variable water supply 总被引:3,自引:0,他引:3
M. Gallardo L. E. Jackson K. Schulbach R. L. Snyder R. B. Thompson L. J. Wyland 《Irrigation Science》1996,16(3):125-137
The effects of a variable water supply on the water use, growth and yield of two crisphead and one romaine (i.e., Cos) lettuce cultivar were examined in a field experiment using a line source sprinkler system that produced a range of water regimes that occur in growers fields. Four locations at increasing distances from the main line were monitored through the season (i.e., from thinning to harvest, 28–63 days after planting (DAP)). These locations at the end of the season corresponded to: (1) rewatering to field capacity (FC); (2) watering with a volume 13% below that required in the field capacity treatment (0.87*FC); (3) 30% below FC (0.70*FC); and (4) 55% below FC (0.45*FC). A linear production function for dry matter accumulation and fresh weight vs. crop evapotranspiration (ETc) was determined for lettuce during this period, giving a water use efficiency for dry matter of 1.86 g m–2 mm–1 and for fresh weight of 48 g m–2 mm–1 . For lettuce irrigated to field capacity, ETc between thinning and harvest was 146 mm; maximum crop coefficients of 0.81–1.02 were obtained at maturity (55–63 DAP). For the three irrigation treatments receiving the largest water application, ETc was higher in the Cos culivar than in the two crisphead lettuce cultivars which had similar ETc. Plant fresh weight was more sensitive than dry weight to reduction in water supply. In the FC treatment, root length density and soil water extraction were greatest in the top 0–45 cm, and decreased rapidly below 45 cm depth. Soil water extraction by roots increased at lower depths when irrigation was reduced. Instantaneous rates of leaf photosynthesis and leaf water potential showed no response to the irrigation treatments in this study, despite differences in biomass production. Evaporation was determined to be the major component of ETc for 45 of the 63 days of the growing season. The large loss of water by evaporation during mid-season and the apparent insensitivity of lettuce to the volume of irrigation during this period may provide an opportunity for reducing irrigation applications. 相似文献
108.
建立了带抛物槽式集热器的太阳能再热式有机朗肯循环发电系统模型,研究了再热式有机朗肯循环系统热效率增加量与输出功增加量随蒸发温度的变化规律。结果表明:当再热压力比为0.25时,太阳能再热式有机朗肯循环系统能有效地提高系统总效率,输出功随蒸发温度增加近似呈线性增加。对分别以R11、R114、R134a和R245fa为工质的再热式有机朗肯循环系统热效率提高量进行比较,以R245fa为工质的再热式有机朗肯循环热效率提高最大,达4.3%。 相似文献
109.
Tape depth and germination method influence patterns of salt accumulation with subsurface drip irrigation 总被引:3,自引:0,他引:3
Trenton L. Roberts Scott A. White Arthur W. Warrick Thomas L. Thompson 《Agricultural Water Management》2008,95(6):669-677
Subsurface drip irrigation (SDI) can result in accumulation of soluble salts at or near the soil surface. In the southwestern USA, rainfall is usually inadequate for stand establishment, thus supplemental irrigation is necessary. Use of sprinklers to minimize salt concentrations near the soil surface is an alternative to using SDI for stand establishment. Our objective was to evaluate the effects of germination method (irrigation with SDI or sprinklers), depth of SDI tape (0.18 and 0.25 m), and irrigation water salinity (1.5 and 2.6 dS m−1) on salt and Br distribution after each of two consecutive growing seasons. Treatments consisted of factorial combinations of these three factors. Bromide was used to trace salt accumulation from the drip tape. After season 1, the highest salt concentrations (ECe up to 11 dS m−1) were in the top 3 cm of soil. Below 3 cm, soil EC dropped significantly and remained constant to 1.05 m. Similarly, Br concentrations were highest in the top 3 cm of soil. The mass of salt and Br recovered in the top 3 cm were significantly affected by tape depth, and water EC significantly affected salt mass. Salt present in the soil after season 1 adversely affected crop emergence in season 2, where SDI was used for stand establishment. After season 2, the highest salt and Br concentrations were at about 25 cm depth, probably due to 210 mm of rainfall that occurred near the end of the growing season. There were no significant differences among treatments in the mass of either salt or Br in the top 3 cm or 16 cm of the soil profile after season 2. Timely rainfall, transplanting rather than direct seeding, and changing bed geometry can reduce dependence on sprinklers for stand establishment. 相似文献
110.
Modern pigs grow fast but are highly susceptible to degenerative joint abnormalities, including osteochondrosis. Normal and osteochondrotic humeri and femurs were obtained from five normal and ten lame adolescent boars to study cartilage proteoglycans. Histological examination of joints indicated a locally-reduced intensity of proteoglycan staining by safranin-O in lesion areas of cartilage. Cartilage proteoglycans extracted with 4.0 M guanidinium chloride were studied using Sepharose 2B gel chromatography. The proteoglycans from severely osteochondrotic joints were less (P less than 0.05) aggregated and contained a greater (P less than 0.05) proportion of smaller monomers than those from normal joints. Loss or damage of core protein, including its hyaluronic acid-binding regions, may account for the greater proportion of small monomers. The results also indicated that the proportion of hyaluronic acid in the total glycosaminoglycan uronic acid fraction, estimated by Sephadex G-200 chromatography and cellulose acetate electrophoresis, was lower (P less than 0.05) for the extracted proteoglycans than for the residual or the whole cartilage proteoglycans in all joints studied. 相似文献