Showing papers by "Wageningen University and Research Centre published in 1992"

The principal neutralization determinant of simian immunodeficiency virus differs from that of human immunodeficiency virus type 1.

Abstract: To identify the principal neutralization determinant (PND) of simian immunodeficiency virus (SIV), antisera were generated using recombinant gp110 [the SIV analog of the human immunodeficiency virus type 1 (HIV-1) external envelope glycoprotein, gp120], gp140, several large recombinant and proteolytic envelope fragments, and synthetic peptides of the SIVmac251 isolate. When purified under conditions that retain its native structure, gp110 bound CD4 and elicited antisera that neutralized SIVmac251 with high titer. Native gp110 also completely inhibited neutralizing antibody in sera from SIVmac251-infected macaques. In contrast, denatured gp110 and gp140, large envelope fragments, and synthetic peptides (including peptides analogous to the HIV-1 PND) elicited very low or undetectable neutralizing antibody titers and did not inhibit neutralizing antibody in infected macaque sera. Enzymatically deglycosylated gp110 efficiently absorbed neutralizing antibodies from macaque sera, showing that neutralizing antibodies primarily bind the protein backbone. A 45-kDa protease digest product, mapping to the carboxyl-terminal third of gp110, also completely absorbed neutralizing antibodies from infected macaque sera. These results show that the PND(s) of this SIV isolate depends on the native conformation and that linear peptides corresponding to the V3 loop of SIV envelope, in contrast to that of HIV-1, do not elicit neutralizing antibody. This may affect the usefulness of SIVmac for evaluating HIV-1 envelope vaccine approaches that rely on eliciting neutralizing antibody.

Fat distribution in European men: a comparison of anthropometric measurements in relation to cardiovascular risk factors.

Abstract: It has been proposed that subcutaneous fat patterning assessed by skinfolds is measuring different aspects of fat distribution compared to circumferences and circumference ratios. In this study in 510 men born in 1950 selected from six European towns we compared the associations between five skinfolds, eight circumferences and several skinfold and circumference ratios and metabolic risk factors after adjustment for body mass index (BMI). All skinfolds were independently of BMI positively related to diastolic blood pressure. Waist circumferences at most levels were independently of BMI positively related to blood pressure and triglycerides and negatively to HDL-cholesterol. Circumferences at the levels of chest, hips, thigh and arm were not related to any of the risk factors studied. Waist/thigh ratios were generally more strongly and more consistently related to risk factors than waist/hip ratios. The partial correlations of anthropometric variables with risk factors were relatively weak and never exceeded r = 0.20. The results give an indication, however, that subcutaneous fat patterning is related to different risk factors compared to waist/hip ratios. Moreover, waist/thigh and waist circumference alone (measured either as the minimal circumference or midway between the lower rib margin and the iliac crest) were stronger correlates of cardiovascular risk factors compared to waist/hip ratio.

Start-up of a thermophilic upflow anaerobic sludge bed (UASB) reactor with mesophilic granular sludge

Abstract: Fast start-up of thermophilic upflow anaerobic sludge bed (UASB) reactors was achieved at process temperatures of 46, 55 and 64° C, using mesophilic granular sludge as inoculum and fatty acid mixtures as feed. The start-up was brought about by increasing the temperature of mesophilic UASB reactors in a single step, which initially led to a sharp drop in the methane production rate. Thereafter, stable thermophilic methanogenesis was achieved within a period of 1 or 2 weeks depending on the temperature of operation. Mesophilic granules functioned initially as effective carrier material for thermophilic organisms. However, long-term operation led to disintegration of the granules, resulting in wash-out of thermophilic biomass. The temperature optima for acetotrophic methanogenic activity of the sludges cultivated at 46, 55 and 64° C, were similar, but differed significantly from the temperature optimum of the mesophilic inoculum. All the sludges examined were dominated by Methanothrix-like rods. These could be distinguished by antigenic fingerprinting into two subpopulations, one predominant at 36° C and the other predominant at 46° C and above.

Dissimilar expression of Autographa californica multiple nucleocapsid nuclear polyhedrosis virus polyhedrin and p10 genes.

Abstract: The temporal expression of the Autographa californica multiple nucleocapsid nuclear polyhedrosis virus polyhedrin and p10 genes in Spodoptera frugiperda cells was studied using virus recombinants in which either gene was replaced by the juvenile hormone esterase (JHE) gene of Heliothis virescens. The JHE served as a highly specific and sensitive reporter for gene expression. Activation of the p10 gene followed a pattern different to that of polyhedrin. The p10 gene was activated a few hours earlier than the polyhedrin gene, but its expression reached a lower maximum level. Northern blot analysis complemented and confirmed the results obtained from the JHE assays. Co-infection of sense recombinants and those containing an anti-sense copy of the JHE gene in place of the polyhedrin or p10 gene resulted in reduced levels of JHE gene expression. These experiments independently supported the hypothesis that the p10 gene promoter is more active at earlier times post-infection than that of the polyhedrin gene. The results also highlight the potential of the antisense strategy as an experimental approach for the study of baculovirus gene regulation and possibly insect metabolism.

On the characterization of properties of an unripe marine clay soil: I. Shrinkage processes of an unripe marine clay soil in relation to physical ripening

Abstract: Shrinkage processes, such as volumetric shrinkage behavior, and the geometry of the volume shrinkage were studied with respect to the physical ripening naturally occurring in a marine clay soil. Three-dimensional volume shrinkage was characterized using the shrinkage characteristic curve determined

Young Adolescents' Perceptions of Environmental Issues: Implications for Environmental Education in Urban Settings.

Abstract: Student's perceptions of the environment and environmental issues and its implications for environmental studies in the Detroit metropolitan area are investigated. Students feel rather than politicizing the environmental problems, they can be tackled by the principles of re-use and recycle, limiting the use of the perks of modern society and boycotting polluting products.

Relations between occupation, smoking, lung function, and incidence and mortality of chronic non-specific lung disease: the Zutphen Study.

Abstract: Information gathered in the "Zutphen study", the Dutch contribution to the Seven Countries Study was used for the present study. Follow up data from 1965 to 1 July 1985 were used. During this follow up, the morbidity state of the participants was verified at regular intervals. In 1965 lung function was measured by spirometry and the vital capacity (VC) and forced expiratory volume in one second (FEV1) were available. A complete set of data was available for 668 men. The occurrence of chronic non-specific lung disease (CNSLD) at a specific time was coded by one physician, using strict criteria. Information about the cause of death was obtained and coded by one physician in 1985. Occupation was coded and a distinction between blue and white collar workers was made. For the analysis of the relation between age, lung function, smoking habits, and occupational state with CNSLD incidence and mortality, proportional hazard models were used. Blue collar workers had a significantly raised risk for incidence of CNSLD only. The hazard ratio for blue v white collar workers with CNSLD mortality was 1.4 but not statistically significant. It was concluded that occupation is clearly related to incidence of CNSLD. There were indications that occupation is related to mortality from CNSLD. A reduced FEV1 was a strong predictor of both CNSLD incidence and mortality. It is noteworthy that small differences in age and height standardised lung function were significantly related to incidence of CNSLD, mortality from CNSLD, and total mortality. Although these differences in lung function have no direct clinical importance for the individual subject, they indicate a raised morbidity and mortality risk for the population.

Influence of NH3 and SO2 on the growth and competitive ability of Arnica montana L. and Viola canina L

Abstract: SUMMARY The effects of atmospheric NH3 and SO2 separately and in combination on the growth and competitive ability of three species of the Violion caninae alliance were investigated. Growth and nutrient concentrations of Viola canina and Arnica montana in mixed culture with Agrostis capillaris were examined in relation to that in monoculture. Seedlings were transplanted into heathland topsoil in pots and placed in open-top chambers for 9 months from autumn to summer, where they were exposed to ambient air, 90,ug m3 SO2, 50,ug m-3 NH3 and to the combination of NH3 and SO2' In the NH3 + SO2 treatment, a more-than-additive increase in nitrogen and sulphur concentrations was observed indicating co-deposition. NH3 influenced the nutritional status of V. canina the most, increasing the nitrogen, phosphorus, and magnesium concentrations and reducing those of potassium and calcium. NH3 fumigation significantly stimulated shoot growth of all three species and root growth of A. capillaris, while SO2 reduced only the root growth of A. capillaris. The relative yield of V. canina was reduced by 20-30 % in the presence of the air pollutants. The relative yield of A. montana was stimulated by 30-40 % in treatments including SO2 compared with that in ambient air or NH3 alone. The competitive ability of both dicotyledons in mixed culture with A. capillaris was strongly reduced by NH3 and was unaffected by SO2' The consequences of exposure to NH3 and S02 for the survival and maintenance of threatened species in heathland vegetation are discussed.

Anaerobic degradation of benzaldehyde in methanogenic granular sludge: the influence of additional substrates.

Abstract: The degradation of benzaldehyde in methanogenic granular sludge was investigated in batch and in upflow anaerobic sludge blanket (UASB) reactors. The effect due to the presence of co-substrates, such as H2, sodium butyrate and sucrose, was studied using formaldehyde as a reference compound. The additional substrates enhanced the activity of benzaldehyde- and formaldehyde-degrading microorganisms (ACTbdm and ACTfdm, respectiveky) and increased the transient production of benzyl alcohol and methanol. As a consequence, the concentrations of benzaldehyde and formaldehyde that caused 50% inhibition of the methanogenic activity (50% ICm) on sucrose were 3133 and 254 mg chemical oxygen demand (COD)/l respectively, three times higher than the literature data values on acetate. Experiments performed in UASB reactors on benzaldehyde showed that the replacement of volatile fatty acids with sucrose as co-substrate improved the treatment capacity of the system from 0.73 to 4.36 kg COD benzaldehyde·m−13·day−1.

Effect of folding and feeding by Cnaphalocrocis medinalis on photosynthesis and transpiration of rice leaves

Abstract: The rice leaffolder Cnaphalocrocis medinalis (Guen6e) is a widely distributed pest of rice crops in South and South-East Asia. The larvae of this moth spin rice leaves longitudinally and feed inside the folded leaves. A detailed description of the spinning and feeding behaviour is given by Fraenkel and Fallil (1981) and Fraenkel etal. (1981). Feeding rates of the larvae have been quantified by Heong and Fabellar (1988). Inside the folded leaves, a substantial leaf area can be left intact by the feeding larvae. The present study has been conducted to quantify the maximum rate of photosynthesis in the remaining green leaf area in folded leaves. This information is needed as input for a crop growth model simulating the effect of leaffolder injury on yield. In the same experiment, transpiration was measured.

Reactions of Cloned Poplars to Air Pollution: Premature Leaf Loss and Investigations of the Nitrogen Metabolism

Abstract: Abstract Young poplar cuttings (Populus nigra L. cv. Loenen and P. maximowiczii Henry x P. nigra L. cv. Rochester) were exposed for six weeks in open-top chambers to realistic concentrations of pollutant mixtures: 1) control; 2) SO2/NOx; 3)O3/ NOx and 4)SO2/O3/NOx. In this sequence of fumigation variants, the degree of influence of the various parameters of the nitrogen metabolism and of premature leaf drop increased very frequently compared to the control plants, P. nigra L. proving to be the more sensitive species. The elevated Kjeldahl nitrogen content of the fumigated leaves was accompanied by either an increase in free amino acids or in total protein or, in the case of particularly large rises (SO2/O3/NOx variants), by increases in both substance groups. Proteolytic processes as a cause of the elevated content of free amino acids could be excluded to a large extent. A diminished de novo synthesis of proteins obviously led to a shift in the amino acid/protein relationship. In the younger fumigated leaves, the total concentration of free amino acids exceeded the values of the older leaves. The elevated amino acid content of the fumigated leaves was produced to a high degree by the glycolate pathway and the Krebs cycle. The increased turnover of the carbon skeletons was connected with a drastic starch degradation, especially in the older leaves. The interaction of the amino acid and carbohydrate metabolisms is probably an important regulator in the promotion of rapid growth of young leaves in order to compensate premature leaf loss.

Erosion surfaces in the Chuka-South area, central Kenya

Abstract: In Kenya, erosion surfaces up to now have been interpreted mainly using the cyclic denudation concept of King (1967), based on their specific altitudes. Detailed fieldwork in the Chuka-South area shows that altitudinal differences are more related to lithological control than to ages of planation surfaces. This strong lithology-landform relationship is thought to be caused by etching and stripping. Rock properties such as texture, mineralogy and the fracture porosity largely determine the rate of chemical decomposition. -from Authors

Computation of the digital lqg regulator and tracker for time‐varying systems

Abstract: Digital optimal control problems, i.e. problems where a continuous-time system is controlled by a digital computer, are very often approximated by either discrete-time or continuous-time optimal control problems. A digital controller based on one of these approximations requires a small sampling time and constitutes only an approximate solution. The digital LQG regulator and tracker constitute solutions to real digital control problems which involve sampled-data, piecewise constant controls and integral criteria. Until now only the numerical computation of the digital LQG regulator in the case of time-invariant system and criterion matrices has been considered in the literature. The control of non-linear stochastic systems about state trajectories is very often performed by an LQG regulator based on the linearized dynamics about the trajectory, which constitute a time-varying system. We present a numerical procedure to compute the digital LQG regulator and tracker in the case where the system and criterion matrices are time-varying. Finally we present a numerical example.

Control of activated sludge plants based on measurement of respiration rates.

Abstract: An integral control strategy for activated sludge plants presented in this paper consists of three low-level control tasks. The first is the actual respiration rate control by manipulating the influent flow rate, whereby the aerators are at a fixed position for each setpoint. The second task is the maximum respiration rate control by manipulating the waste activated sludge flow rate. The third task of the integral control strategy is the instantaneous respiration rate monitoring, which informs the operator about the performance of the process.

The Anomalous Behaviour of the PPE Signal in the Critical Region of a Phase Transition — New Support for the General Theoretical Model

Abstract: The structural (tetragonal-orthorombic) phase transition of La194Sr006CuO4 was detected using the PPE method The experiment, performed in the vicinity of the singular point of the operation diagram, allows for the indirect determination of the material optical absorption coefficient

Dependence of the photoacoustic cell constant on the sample gas.

Abstract: The CO2 laser and the windowless resonant cell equipped with the electronic resonance tracking system were combined into the photoacoustic spectrometer. In order to facilitate the comparison of various analytical purpose PA systems and other spectroscopic methods, we suggest the introduction of instrumental figure characterizing the PA instrument. The photoacoustic spectrometer was calibrated using a series of certified precision mixtures of ammonia, ethylene and carbon-dioxide in a high purity grade nitrogen. The absorbance as low as 2*10−6 could be measured. The instrumental figures were found different: 0.98 V/W for the carbon-dioxide, 1.68 V/W for ethylene and 2.4 V/W for the ammonia.

Photoacoustic detection of temperature phenomena in beeswax.

Abstract: The need for non-destructive monitoring of phase transitions in biological specimens is an important issue in agricultural practice for the status of the membrane stability of various plant materials [1]. This paper is concerned with flashlight photoacoustic detection of phase transitions in beeswax, a biological material that exhibits a pronounced phase transition (change in colour from transparent to milky near 32° C). The same technique was applied to observe phase transitions taking place in a coating of a familiar battery tester. These preliminary studies are initial steps towards development of the flashlight photoacoustic technique for investigations of more complex samples such as seeds and pollen of plants.

Photopyroelectric (PPE) Detection of the Antiferromagnetic 3D-2D Phase Transition in Single Crystal La2CuO4

Abstract: The 3D-2D antiferromagnetic phase transition in La2CuO4 single crystal was detected by the PPE technique. The critical discontinuity of the specific heat found by this method is about 1%.