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W de Vries

Publications and source records attributed to W de Vries.

At least 19 recordsLinked to original sources
PubMed2001

Assessments of impacts of nitrogen deposition on beech forests: results from the Pan-European Monitoring Programme.

The article reviews effects of nitrogen (N) deposition on beech forest ecosystems in Europe. On the basis of beech plots of the Pan-European Monitoring Programme of ICP Forests and the EU, the deposition of N compounds as well as input-output budgets are listed and compared with studies in North America. The authors also discuss the critical threshold for N leaching. At present, N is leached in 10% of the plots evaluated. An in-depth evaluation of a beech plot in central Germany is presented. The high N leaching results in a considerable increase (four times higher N content in 2000 compared to 1965) in the export of nitrate from the beech forests from a nearby source. Finally, ecophysiological indicators (N content in beech leaves, fine root system, N content, root/shoot ratios) are discussed as a result of high N input.

Aluminum↗
PubMed2001

Modeled impacts of farming practices and structural agricultural changes on nitrogen fluxes in the Netherlands.

In the Netherlands, nutrient emissions from intensive animal husbandry have contributed to decreased species diversity in (semi) natural terrestrial and aquatic ecosystems, pollution of groundwater, and possibly global warming due to N2O emissions. This paper presents the results of a modelling study presenting the impacts of both structural measures and improved farming practices on major nitrogen (N) fluxes, including NH3 and N2O emission, uptake, leaching, and runoff, in the Netherlands, using input data for the year 2000. Average annual fluxes (Gg N year(-1)) for the year 2000 were estimated at 132 for NH3 emission (160 Gg NH 3 year(-1)), 28 for N2O emission, 50 for N inflow to groundwater, and 15 for N inflow to surface water at a total N input of 1046. At this input, nitrate (NO3) concentrations in groundwater often exceeded the target of 50 mg NO3 l(-1), specifically in well-drained sandy soils. The ammonia (NH3) emissions exceeded emission targets that were set to protect the biodiversity of nonagricultural land. Improved farming practices were calculated to lead to a significant reduction in NH3 emissions to the atmosphere and N leaching and runoff to groundwater and surface water, but these improvements were not enough to reach all the targets set for those fluxes. Only strong structural measures clearly improved the situation. The NH3 emission target of 30 Gg NH3 year(-1), suggested for the year 2030, could not be attained, however, unless pig and poultry farming is completely banned in the Netherlands and all cattle stay almost permanently in low emission stables.

Agriculture↗
PubMed2001

Assessment of nitrogen ceilings for Dutch agricultural soils to avoid adverse environmental impacts.

In the Netherlands, high traffic density and intensive animal husbandry have led to high emissions of reactive nitrogen (N) into the environment. This leads to a series of environmental impacts, including: (1) nitrate (NO3) contamination of drinking water, (2) eutrophication of freshwater lakes, (3) acidification and biodiversity impacts on terrestrial ecosystems, (4) ozone and particle formation affecting human health, and (5) global climate change induced by emissions of N2O. Measures to control reactive N emissions were, up to now, directed towards those different environmental themes. Here we summarize the results of a study to analyse the agricultural N problem in the Netherlands in an integrated way, which means that all relevant aspects are taken into account simultaneously. A simple N balance model was developed, representing all crucial processes in the N chain, to calculate acceptable N inputs to the farm (so-called N ceiling) and to the soil surface (application in the field) by feed concentrates, organic manure, fertiliser, deposition, and N fixation. The N ceilings were calculated on the basis of critical limits for NO 3 concentrations in groundwater, N concentrations in surface water, and ammonia (NH3) emission targets related to the protection of biodiversity of natural areas. Results show that in most parts of the Netherlands, except the western and the northern part, the N ceilings are limited by NH 3 emissions, which are derived from critical N loads for nature areas, rather than limits for both ground- and surface water. On the national scale, the N ceiling ranges between 372 and 858 kton year(-1) depending on the choice of critical limits. The current N import is 848 kton year(-1). A decrease of nearly 60% is needed to reach the ceilings that are necessary to protect the environment against all adverse impacts of N pollution from agriculture.

Agriculture↗
PubMed2001

A review of the calculation procedure for critical acid loads for terrestrial ecosystems.

Target loads for acid deposition in the Netherlands, as formulated in the Dutch environmental policy plan, are based on critical load calculations at the end of the 1980s. Since then knowledge on the effect of acid deposition on terrestrial ecosystems has substantially increased. In the early 1990s a simple mass balance model was developed to calculate critical loads. This model was evaluated and the methods were adapted to represent the current knowledge. The main changes in the model are the use of actual empirical relationships between Al and H concentrations in the soil solution, the addition of a constant base saturation as a second criterion for soil quality and the use of tree species-dependant critical Al/base cation (BC) ratios for Dutch circumstances. The changes in the model parameterisation and in the Al/BC criteria led to considerably (50%) higher critical loads for root damage. The addition of a second criterion in the critical load calculations for soil quality caused a decrease in the critical loads for soils with a median to high base saturation such as loess and clay soils. The adaptation hardly effected the median critical load for soil quality in the Netherlands, since only 15% of the Dutch forests occur on these soils. On a regional scale, however, critical loads were (much) lower in areas where those soils are located.

Acid Rain↗
PubMed2000

Evidence against a redshift z > 6 for the galaxy STIS123627+621755.

The identification of galaxies at extreme distances provides the most direct information about the earliest phases of galaxy formation. But at redshifts z > 5 even the most luminous galaxies appear faint; the interpretation of low signal-to-noise ratio data is difficult and misidentifications do occur. Here we report optical and near-infrared observations of the source STIS123627+621755, which was previously suggested to be at a redshift of 6.68 (ref. 1). At that redshift, and with the reported spectral energy distribution, the galaxy should be essentially invisible at wavelengths less than 9,300 A, because the intervening intergalactic medium absorbs almost all light energetic enough to ionize neutral hydrogen--that is, with wavelengths less than the redshifted Lyman limit of lambda = (1 + z) x 912A. At near-infrared wavelengths, however, the galaxy should be relatively bright. Here we report a detection of the galaxy at 6,700 A and a non-detection at a wavelength of 1.2 microm, contrary to expectations for z approximately 6.68. The data conservatively require that STIS123627+621755 has a redshift z < 6.

Journal Article↗
PubMed2000

Cloning and characterization of human histone deacetylase 8.

To date, seven different human histone deacetylases (HDACs) have been identified, which fall into two distinct classes. We have isolated and characterized a cDNA encoding a novel human HDAC, which we name HDAC8. HDAC8 shows a high degree of sequence similarity to HDAC1 and HDAC2 and thus belongs to the class I of HDACs. HDAC8 is expressed in a variety of tissues. Human cells overexpressing HDAC8 localize the protein in sub-nuclear compartments whereas HDAC1 shows an even nuclear distribution. In addition, the HDAC8 gene is localized on the X chromosome at position q13, which is close to the XIST gene and chromosomal breakpoints associated with preleukemia.

Amino Acid Sequence↗
PubMed1999

Platelet-bound immunogloblins before and after platelet transfusion: measurement of in vivo binding.

In routine tests to investigate immunological mechanisms as a cause for enhanced destruction of transfused platelets; serum from the patient is tested against a panel of donor lymphocytes and platelets to demonstrate the presence of antibodies against HLA or platelet specific antibodies. Here we describe a flow cytometric technique in which in vivo binding of immunoglobulins (Ig) is measured. By comparing the histograms of the platelet suspensions before and after transfusion, four different patterns were obtained: no Ig binding before and after transfusion (pattern 1), pre-existent Ig binding (patterns 2 and 3) or preferential Ig binding to the transfused platelets (pattern 4). This technique was tested in 164 random platelet transfusions and 34 HLA-matched platelet transfusions. A statistically significant association was found between pattern 1 and a negative result of the indirect platelet immunofluorescence test for the detection of antibodies in the serum taken before the transfusion studied or a good platelet recovery and between pattern 4 and a positive indirect platelet immunofluorescence test or a low platelet recovery.

Autoimmunity↗
PubMed1998

Correction factors for the NMi free-air ionization chamber for medium-energy x-rays calculated with the Monte Carlo method.

A new method is described for the determination of x-ray quality dependent correction factors for free-air ionization chambers. The method is based on weighting correction factors for mono-energetic photons, which are calculated using the Monte Carlo method, with measured air kerma spectra. With this method, correction factors for electron loss, scatter inside the chamber and transmission through the diaphragm and front wall have been calculated for the NMi free-air chamber for medium-energy x-rays for a wide range of x-ray qualities in use at NMi. The newly obtained correction factors were compared with the values in use at present, which are based on interpolation of experimental data for a specific set of x-ray qualities. For x-ray qualities which are similar to this specific set, the agreement between the correction factors determined with the new method and those based on the experimental data is better than 0.1%, except for heavily filtered x-rays generated at 250 kV. For x-ray qualities dissimilar to the specific set, differences up to 0.4% exist, which can be explained by uncertainties in the interpolation procedure of the experimental data. Since the new method does not depend on experimental data for a specific set of x-ray qualities, the new method allows for a more flexible use of the free-air chamber as a primary standard for air kerma for any x-ray quality in the medium-energy x-ray range.

Air↗
PubMed1998

Enterococcal endocarditis--a case treated with teicoplanin and amoxycillin.

The study aimed to determine the antibacterial therapy effective in the cure of endocarditis caused by Enterococcus faecalis resistant to clinically achievable levels of vancomycin. Isolation of the causative enterococcus had been achieved by direct inoculation of the resected valve into the culture medium in theatre. The patient was known to have had an aortic valve defect since childhood and had recently undergone splenectomy following trauma. Blood cultures were negative prior to valve replacement. A perivalvular abscess was noted at operation. In vitro minimal bactericidal results and serum activity were the basis of the postoperative choice of drugs. The minimal bactericidal level of teicoplanin was 250 micrograms/ml and that of amoxycillin 64 micrograms/ml. Neither is achievable with the advocated dosage. A combination of these two cell-wall-active agents successfully eliminated the infection. Acting at two different sites in the synthesis of the bacterial cell wall, teicoplanin and amoxycillin were found to be bactericidal in vitro at the trough levels of the antibiotics in the serum. The patient recovered fully.

Adult↗
PubMed1996

Detection of static and dynamic activities using uniaxial accelerometers.

Rehabilitation treatment may be improved by objective analysis of activities of daily living. For this reason, the feasibility of distinguishing several static and dynamic activities (standing, sitting, lying, walking, ascending stairs, descending stairs, cycling) using a small set of two or three uniaxial accelerometers signals can be measured with a portable data acquisition system, which potentially makes it possible to perform online detection of static and dynamic activities in the home environment. However, the procedures described in this paper have yet to be evaluated in the home environment. Experiments were conducted on ten healthy subjects, with accelerometers mounted on several positions and orientations on the body, performing static and dynamic activities according to a fixed protocol. Specifically, accelerometers on the sternum and thigh were evaluated. These accelerometers were oriented in the sagittal plane, perpendicular to the long axis of the segment (tangential), or along this axis (radial). First, discrimination between the static or dynamic character of activities was investigated. This appeared to be feasible using an rms-detector applied on the signal of one sensor tangentially mounted on the thigh. Second, the distinction between static activities was investigated. Standing, sitting, lying supine, on a side and prone could be distinguished by observing the static signals of two accelerometers, one mounted tangentially on the thigh, and the second mounted radially on the sternum. Third, the distinction between the cyclical dynamic activities walking, stair ascent, stair descent and cycling was investigated. The discriminating potentials of several features of the accelerometer signals were assessed: the mean value, the standard deviation, the cycle time and the morphology. Signal morphology was expressed by the maximal cross-correlation coefficients with template signals for the different dynamic activities. The mean signal values and signal morphology of accelerometers mounted tangentially on the thigh and the sternum appeared to contribute to the discrimination of dynamic activities with varying detection performances. The standard deviation of the signal and the cycle time were primarily related to the speed of the dynamic activities, and did not contribute to the discrimination of the activities. Therefore, discrimination of dynamic activities on the basis of the combined evaluation of the mean signal value and signal morphology is proposed.

Activities of Daily Living↗
PubMed1993

Quantification of fluorescence properties of lymphocytes in peripheral blood mononuclear cell suspensions using a latent class model.

Lymphocytes, monocytes, granulocytes, and other blood cells can be distinguished on the basis of their forward (FSC) and sideward (SSC) light scatter properties and their expression of CD45 and CD14. A FSC,SSC gate can be set to include > 95% of the lymphocytes using a "back gating" procedure on the CD45+, CD14- cells. However, nonlymphoid cells such as monocytes have light scattering properties similar to lymphocytes. This problem occurs particularly in patient populations where the light scattering properties of lymphocyte subsets have changed (e.g., due to activation) and are similar to those of the monocytes. Thus, immunophenotyping using antibodies specific for other markers than CD45 and CD14 does not allow a direct assessment of the percentage of all lymphocytes positive for those markers. In order to optimize immunophenotyping we have developed analytic model in which the FSC,SSC dot plot is partitioned into six nonoverlapping light scatter regions. Each light scatter region contains a mixture population of different cell types, i.e., lymphocytes, monocytes, granulocytes, and other cells. The proportions of each cell type are known from the CD45,CD14 expression within each light scatter region. Under the assumption of independence of fluorescence and scatter properties conditional on cell type, the expression of markers other than CD45 or CD14 are derived from the cell type composition and the fluorescence properties on the other markers of each light scatter region. The underlying statistical model is a latent class model, and maximum likelihood estimates are computed using the expectation-maximization (EM) algorithm. The application of the model for immunophenotyping of lymphocytes of healthy individuals and cancer patients receiving immunotherapy is shown.

Antibodies, Monoclonal↗
PubMed1993

Acyclic directed graphs for automatic image analysis of lung parenchymal geometry.

We have developed a simple method for encoding pulmonary alveolar geometry suitable for morphometric analysis and modeling. The approach involves the use of 8-bit video microscopic images of lung which are thresholded to produce binary images. Each alveolar wall was thinned to its midline to produce a skeletonized image. We present an algorithm for converting such an image to an acyclic directed graph. Such a representation is quite suitable for mathematical treatment, lending itself to problems involving simulation or modeling. We present as an example application, the measurement of dihedral angles in rat lung using conventional histological sections.

Algorithms↗
PubMed1992

[Ascaris suum infection as a cause of clinical problems in cattle?].

A sudden decrease in milk yield, increased respiratory rate and occasional coughing were observed in dairy cows on two farms in spring 1991. Pigs were also kept on these farms, and pastures grazed by the cattle had been fertilised with pig slurry. Laboratory investigations of some of the cattle showed eosinophilia and high ELISA titres of antibodies against Ascaris suum. On one farm the clinical symptoms disappeared after the animals had been treated with oxfendazole and on the other farm the symptoms disappeared spontaneously with time.

Animals↗
PubMed1991

Simultaneous flow cytometric detection of antibodies against platelets, granulocytes and lymphocytes.

We present a time-saving and objective flow cytometric immunofluorescence assay for the simultaneous detection of antibodies against platelets, granulocytes or lymphocytes using a reconstituted mixture of these cell populations. Platelets, granulocytes and lymphocytes could be distinguished on the basis of their forward (FSC) and sideways (SSC) light scattering properties plotted on scales of 4 log orders. After setting FSC/SSC gates around the platelets, granulocytes and lymphocytes, the reactivity of the sera with the cell populations was determined by histogram analyses of immunofluorescence for each gate. The flow cytometric assay of reconstituted cell mixtures showed a strong, positive correlation with a reference microscopic immunofluorescence assay of separate cell suspensions. The reproducible procedures for the isolation and staining of the cells and the electronic stability of the flow cytometer permitted the use of the same gate and marker settings throughout the experiments. Consequently, the entire analysis of data stored in list mode could be performed using a keystroke, so that time consuming and subjective manual analyses were avoided.

Antibodies↗
PubMed1986

The effect of the dissolved oxygen concentration and anabolic limitations on the behaviour of Rhizobium ORS571 in chemostat cultures.

Chemostat cultures of Rhizobium ORS571 limited by the supply of oxygen or an anabolic substrate contained poly-beta-hydroxybutyrate (PHB). Low amounts of PHB (about 10%) were present in ammonia- or nitrate-limited cultures; higher amounts were found in Mg++-limited cultures (about 20%) and in oxygen-limited nitrogen-fixing cultures (37%). A method is described to calculate YATP values (g PHB-free biomass . mol-1 ATP) from the Ysucc values (g dry wt . mol-1 succinate) measured. Ysucc and YATP values in cultures limited by the supply of an anabolic substrate and in the oxygen-limited ammonia-assimilating culture were much lower than the values found in the PHB-free succinate-limited cultures. This shows that uncoupling of growth and energy production occurred. Therefore, H2/N2 ratio (mol hydrogen formed per mol nitrogen fixed) in nitrogen-fixing cultures could not be calculated from the comparison of the YATP value found in the nitrogen-fixing culture and the value found in the corresponding ammonia-assimilating culture. Although the optimal dissolved oxygen concentration (d.o.c.) for nitrogen-fixing cultures of Rhizobium ORS571 is 5 or 10 microM, nitrogen-fixing cultures could be obtained up to a d.o.c. of 40 microM. Not only nitrogenase but also hydrogenase was active at this d.o.c. However, accumulation of PHB (10%) may indicate that cultures grown at unfavourable oxygen concentrations (15-40 microM O2) were N-limited rather than energy-limited, which may be the result of partial inactivation or repression of nitrogenase at a higher d.o.c.

Adenosine Triphosphate↗
PubMed1984

Localization of hydrogenase and nitrate reductase in Campylobacter sputorum subsp. bubulus.

Campylobacter sputorum subsp. bubulus contained hydrogenase activity after growth with lactate and nitrate and after growth with hydrogen and nitrate. After growth with hydrogen and nitrate a molar growth yield (g dry cells/mol hydrogen) of 5.6 was measured. Hydrogenase and nitrate reductase were membrane-bound enzymes. In cells with high hydrogenase activity the----H+/O,----H+/NO2- and----H+/NO3- values with hydrogen as the electron donor were 3.74, 2.61 and 4.36 respectively. In cells with low hydrogenase activity these values were 2.33, -0.86 and 1.31 respectively. These values and the stoichiometry of respiration-driven proton translocation (----H+/2e = 2) led to the conclusion that hydrogenase is located at the periplasmic side of the cytoplasmic membrane. In cells with low lactate dehydrogenase activity or low hydrogenase activity the reduction of nitrate to nitrite could be separated from the reduction of nitrite to ammonia. Positive----H+/NO3- values (between 0.9 and 1.7) with lactate or hydrogen as the electron donor were measured in these cells whereas----H+/ NO2- values were negative. From this result it was concluded that nitrate reductase is located at the cytoplasmic face of the cytoplasmic membrane. The results explain the previous observation that molar growth yields with nitrate were somewhat higher than those with nitrite.

Campylobacter↗
PubMed1984

Hydrogen oxidation and nitrogen fixation in rhizobia, with special attention focused on strain ORS 571.

In this survey we describe the influence of hydrogen oxidation on the physiology of Rhizobium ORS 571. The presence of hydrogen is required for the synthesis of hydrogenase. Carbon substrates do not repress the synthesis of hydrogenase. The respiratory system contains cytrochromes of the b- and c-type. Cytochrome alpha 600 is present after growth at high oxygen tensions. The nature of the terminal oxidases functioning at low oxygen tensions has not been established yet----H+/O values with endogenous substrates are between 6 and 7. The results show the presence of two phosphorylation sites: site 1 (ATP/2e = 1.0) and site 2(ATP/2e = 1.33). By measuring molar growth yields it has been demonstrated that carbon-limited, nitrogen-fixing cultures obtain additional ATP from hydrogen oxidation, and that site 2 of oxidative phosphorylation is passed during hydrogen oxidation. A method is described to calculate ATP/N2 values (the total amount of ATP used by nitrogenase during the fixation of 1 mol N2) and H2/N2 ratios (mol hydrogen formed per mol N2 fixed) in aerobic organisms. For Rhizobium ORS 571 the ATP/N2 value is about 40 and the H2/N2 ratio is between 5 and 7.5. Cells obtained from oxygen-limited nitrogen-fixing cultures contain 30-40% poly-beta-hydroxybutyrate, which explains the high molar growth yields found. Hydrogen has not been detected in the effluent gas of these cultures, which may point to reoxidation of the hydrogen formed at nitrogen fixation. Calculations show that the effect of hydrogen reoxidation on the efficiency of nitrogen fixation (g N fixed X mol-1 substrate converted) is not very large and that the actual H2/N2 ratio is of much more importance. After addition of hydrogen to succinate-limited, ammonia-assimilating cultures, an initial increase of the Ysuccinate value (g dry wt X mol-1 succinate) is followed by a gradual decrease. This is accompanied by a large decrease of the YO2 value, and an increased permeability of the cytoplasmic membrane to protons. The results may be explained by a transition of the culture from an energy-limited state to a carbon-limited state.

Adenosine Triphosphate↗