Assessment of the Regional Variation in Weathering Rates of Loess and Clay Soils in The Netherlands

To calculate critical acid loads or to predict elementconcentrations in the soil solution, information on weatheringrates is essential. Several studies have taken place in theNetherlands to obtain weathering rates for non-calcareous sandysoils. Recently information on weathering rates in less vulnerable loess and clay soils have become available. However,up to now no system is available to estimate weathering rates ona regional scale by relating them to regionally available soilproperties.To obtain weathering rates of loess and clay soils on a regionalscale for the Netherlands, the applicability of a statisticalregression model and the process based PROFILE model have beenevaluated. Both models were calibrated on a set of laboratoryexperiments. To evaluate their predictive power, both methodswere validated on a number of sites for which field weatheringrates were available.Predictions with the statistical model, for the individual basecations, were generally within a factor 2 of the calculatedhistorical weathering rates, except for Ca, which wasoverestimated, by a factor 3 to 4. PROFILE stronglyoverestimated all weathering rates using both standard parameters and in particular after calibration on the laboratoryrates. However, PROFILE predicted weathering rates of the loesssoils quite good after calibration on historical weatheringrates, indicating that the downscaling procedure used in PROFILEto translate laboratory to field weathering rates is inadequatefor the considered soils.The statistical model was applied to predict weathering rates,for the Netherlands on a 1 × 1 km grid scale. Weathering rates at the present pH values in forested loess and clay soilsranged from 135 to 6000 mol_c ha^-1 a^-1 in loesssoils and from 100 to 1750 mol_c ha^-1 a^-1 in claysoils.     

Competition for inorganic and organic N by blue oak (Quercus douglasii) seedlings, an annual grass, and soil microorganisms in a pot study

Sources of competition for limited soil resources, such as nitrogen (N), include competitive interactions among different plant species and between plants and soil microorganisms (microbes). To study these competitive interactions, blue oak seedlings (Quercus douglasii) were grown alone or grown together with an annual grass, wild oats (Avena barbata) in pots containing field soil. We injected ¹⁵N-labeled ammonium, nitrate or glycine into the soil of each pot and harvested plants 5 days later. Plant shoots and roots, soil microbial N and soil KCl-extractable N were analyzed for ¹⁵N content. When oak and grass were grown together, ¹⁵N recovery from the inorganic N treatments (NH₄⁺, or NO₃⁻) was 34, 9 and 4% for the grass, microbes and oak seedlings, respectively, and only 1% remained as KCl-extractable N. ¹⁵N recovery from the glycine treatment was 18, 22, 5% for the grass, microbes and oak seedlings, respectively, and 4% remained as KCl-extractable N. When oaks were grown alone, ¹⁵N recovery by soil microbes was 21, 48 and 40% in the NO₃⁻, NH₄⁺ and glycine treatments, respectively. N forms had no effects on ¹⁵N recovery in oak seedlings (7%) and in KCl-extractable N pool (13%). In general, total N recovery by the grass was much greater than by oaks. However, on a fine root surface area or length basis, oaks exhibited higher N uptake than the grass. Our results suggest that the high rooting density and rapid growth rate of the annual grasses such as Avena barbata made them superior competitors for available soil N when compared to blue oak seedlings and to microbes. Soil microbes were better competitors for organic than inorganic N when annual grasses were present, but preferred NH₄⁺ when competing only with oak seedlings.     

Secular and socio-economic trends in compliance with dietary targets in the north Glasgow MONICA population surveys 1986-1995: did social gradients widen?

OBJECTIVE: To compare trends in the consumption of key foods over 10 years in the most deprived and least deprived quarters in north Glasgow, Scotland as defined by the Carstairs deprivation index for their postcode of domicile. DESIGN: Four random, cross-sectional, age- and gender-stratified population surveys carried out in 1986, 1989, 1992 and 1995. After assigning a deprivation score, food-frequency questionnaires from 2883 men and 3127 women were examined for compliance with dietary targets, examining trends by gender and within the most and least deprived quarters of the population. SETTING: North Glasgow, Scotland. SUBJECTS: Over 600 men and 600 women (aged 25-64 years) in each of the four survey years who completed a lifestyle questionnaire including a food frequency section. RESULTS: Increasing trends in the reported consumption of fruit and vegetables and oil-rich fish were observed over the 10-year period. However, the trend to increased fruit and vegetable consumption in the most deprived groups was not significant, and in 1995 only 8% of men and 12% of women in this group claimed consumption of these foods 4 or more times a day. In general, a higher percentage of those in the least deprived group met the targets for the key foods. CONCLUSIONS: Trends to increasing consumption of fruit and vegetables and fish were in the right direction, but the targets for consumption of certain key foods were met by a minority of the population. The progress towards the target for fruit and vegetables showed widening social gradients with time.     

Grape seed extract affects proliferation and differentiation of human intestinal Caco-2 cells

The effect of daily contact of a grape seed extract (GSE) on Caco-2 cell proliferation and differentiation was investigated. GSE at 400 mg/L was added to Caco-2 cells for 2 h a day after successive incubation in saliva, gastric, and pancreatic media. When applied at the beginning of the cell culture, GSE triggered inhibition of cell growth associated with a possible cytotoxic reaction. On the other hand, when the treatment was applied to confluent cells, treated cells displayed a higher protein content than control cells and a more developed brush border, with taller and denser microvilli. These observations were accompanied by stimulation of alkaline phosphatase activity, especially at day 5 postconfluency, with a 2.2-fold increase in comparison with the control. On the other hand, aminopeptidase N activity was inhibited throughout the differentiation period in GSE-treated cells to reach 28.8% of control cell activity on day 30. GSE did not affect either sucrase-isomaltase activity or cytoplasmic lactate dehydrogenase (LDH) activity, which otherwise appeared to be a good cellular marker. GSE treatment of Caco-2 cells thus inhibited their proliferation from seeding onward and stimulated both proliferation and differentiation after confluency.     

Shading effect on physiological parameters and in vitro embryo production of tropical adapted Nellore heifers in integrated crop-livestock-forest systems

Tropical Animal Health and Production - The aim of this study was to evaluate the impact of increased shadow supply in integrated crop-livestock-forest systems on in vitro embryonic development and...     

The impact of altered herbicide residues in transgenic herbicide-resistant crops on standard setting for herbicide residues

The global area covered with transgenic (genetically modified) crops has rapidly increased since their introduction in the mid-1990s. Most of these crops have been rendered herbicide resistant, for which it can be envisaged that the modification has an impact on the profile and level of herbicide residues within these crops. In this article, the four main categories of herbicide resistance, including resistance to acetolactate-synthase inhibitors, bromoxynil, glufosinate and glyphosate, are reviewed. The topics considered are the molecular mechanism underlying the herbicide resistance, the nature and levels of the residues formed and their impact on the residue definition and maximum residue limits (MRLs) defined by the Codex Alimentarius Commission and national authorities. No general conclusions can be drawn concerning the nature and level of residues, which has to be done on a case-by-case basis. International residue definitions and MRLs are still lacking for some herbicide-crop combinations, and harmonisation is therefore recommended.     

Epidemiological and histological components of crown rust resistance in oat genotypes

Crown rust, caused by Puccinia coronata f. sp. avenae, can cause significant damage in all regions where oats (Avena sativa L.) are cultivated. The primary means of controlling crown rust has been through genetic resistance, although in most cases resistance has been quickly overcome by the pathogen. More durable partial or non-specific resistance may possess different mechanisms from those underlying genes with specific effects. We studied the epidemiological and histological components of crown rust resistance with potential use in plant protection. Among the components evaluated, pustule density showed the clearest effect on resistance, while the latent period was not an important component. Cell death associated with the accumulation of autofluorescent and phenolic compounds was common in the resistant genotypes, but temporally distinct for the genotypes studied. Genotype Pc68/5*Starter, which has race-specific resistance, showed rapid cell death that prevented the development of pathogen colonies. Conversely, with cultivar URS 21 and genotypes 04B7113-1 and 04B7119-2, cell death and associated accumulation of autofluorescent and phenolic compounds was delayed until pathogen colonies were already established. Pathogen colonies developed normally in susceptible plants genotypes, and had usually produced sporogenic tissue by 5 days after inoculation. The data suggest that the resistance mechanisms, especially hypersensitivity and phenolic compound production, active in resistant plants are similar but may be differently expressed over time. The temporal variation in the expression of hypersensitivity and phenolic compound production reflects the level of field resistance in these genotypes.     

In vitro effect of Aloe vera, Coriandrum sativum and Ricinus communis fractions on Leishmania infantum and on murine monocytic cells

In South America, visceral leishmaniasis is a zoonosis caused by the protozoan species Leishmania infantum (syn. L. chagasi) and is primarily transmitted through the bite of the female Lutzomyia longipalpis. Its main reservoir in urban areas is the dog. The application of control measures recommended by health agencies have not achieved significant results in reducing the incidence of human cases, and the lack of effective drugs to treat dogs resulted in the prohibition of this course of action in Brazil. Therefore, it is necessary to search new alternatives for the treatment of canine and human visceral leishmaniasis. The objectives of this study were to evaluate the in vitro effect of fractions from Aloe vera (aloe), Coriandrum sativum (coriander), and Ricinus communis (castor) on promastigotes and amastigotes of L. infantum and to analyze the toxicity against the murine monocytic cells RAW 264.7. To determine the viability of these substances on 50% parasites (IC50), we used a tetrazolium dye (MTT) colorimetric assay (bromide 3-4.5-dimethylthiazol-2-yl-2,5-dephenyltetrazolium), and on amastigotes we performed an in situ ELISA. All fractions were effective against L. infantum promastigotes and did not differ from the positive control pentamidine (p>0.05). However, the R. communis ethyl acetate and chloroform fractions, as well as the C. sativum methanol fraction, were the most effective against amastigotes and did not differ from the positive control amphotericin B (p>0.05). The R. communis ethyl acetate fraction was the least toxic, presenting 83.5% viability of RAW 264.7 cells, which was similar to the results obtained with amphotericin B (p>0.05). Based on these results, we intend to undertake in vivo studies with R. communis ethyl acetate fractions due the high effectiveness against amastigotes and promastigotes of L. infantum and the low cytotoxicity towards murine monocytic cells.