Should blood gas analysis be part of the diagnostic workup of short children? Auxological data and blood gas analysis in children with renal tubular acidosis.

BACKGROUND: Renal tubular acidosis (RTA) is a rare cause of growth failure, therefore it is uncertain whether routine screening with blood gas analysis of short infants and children is cost-effective. OBJECTIVE: To investigate the clinical, growth and laboratory parameters in children with RTA to estimate the possible value of laboratory screening for this disorder in infants and children referred for short stature according to a recent guideline. METHOD: Retrospective chart analysis of 30 children diagnosed between 1978 and 2005 in The Netherlands and 3 centers in Belgium. RESULTS: The current guideline for short stature detected 33% of children with RTA. Assuming a pre-test probability of RTA of 0.6 per 100,000 births, the likelihood ratio of poor growth was 58 and 17 below and above 3 years, respectively. Sensitivity was 17/30 and 12/24 for a -2.0 SDS cutoff for weight and body mass index, respectively. In infants and toddlers diagnosed before 3 years of age, the mean weight loss was 1.5 SD, and 0.8 SDS in older children. In short children >3 years RTA was extremely rare, always associated with clinical symptoms, and rarely detected by blood gas analysis. CONCLUSION: According to our data a decreasing weight SDS for age is a sufficient indication to perform blood gas analysis in children <3 years of age, particularly in the presence of additional clinical features, whereas it can be omitted in short children >3 years of age.

Protection from obesity in mice lacking the VLDL receptor.

It has previously been reported that mice lacking the VLDL receptor (VLDLR-/-) exhibit normal plasma lipid levels and a modest decrease in adipose tissue mass. In the present study, the effect of VLDLR deficiency on profound weight gain was studied in mice. Obesity was induced either by feeding of a high-fat, high-calorie (HFC) diet or by crossbreeding mice onto the genetically obese ob/ob background. After 17 weeks of HFC feeding, VLDLR-/- mice remained lean, whereas their wild-type littermates (VLDLR+/+) became obese. Similarly, the weight gain of ob/ob mice was less profound in the absence of the VLDLR. Moreover, VLDLR deficiency led to increased plasma triglycerides after HFC feeding. The protection from obesity in VLDLR-/- mice involved decreased peripheral uptake of fatty acids, because VLDLR-/- mice exhibited a significant reduction in whole-body free fatty acid uptake, with no clear differences in food intake and fat absorption. These observations were supported by a strong decrease in average adipocyte size in VLDLR-/- mice of both obesity models, implying reduced adipocyte triglyceride storage in the absence of the VLDLR. These results suggest that the VLDLR plays a role in the delivery of VLDL-derived fatty acids into adipose tissue.

Measuring dew formation and its threshold value for net radiation loss on top leaves in a paddy rice crop by using the dewball: a new and simple instrument.

In a field experiment on dew formation in tropical paddy rice, the threshold value for the nocturnal net radiative loss required for dew formation was investigated during 23 nights from February to April 1994. The onset and cessation of dew were visually observed on both the top leaves of a rice crop and on a glass sphere, the "dewball", installed in the field 1.0 m above the ground. The threshold value for the nocturnal net radiative loss (Rn,thresh) necessary for dew formation on the ball was deduced from the maximum zenith angle on the ball surface reached by the dew formed. Rn,thresh was found to be linearly related to the nightly minimum vapour-pressure deficit. This linear relationship as well as the Penman-Monteith equation (an energy-balance approach) were used to predict both the time of dew onset and the duration of dew on the ball. These predicted values agreed well with the observed results. Dew duration and time of dew onset on the ball were well correlated. During most nights, dew began to form on the top leaf surfaces at almost the same time as it reached the zenith angle of 60 degrees on the ball. A linear relationship was found between the observed daily duration of dew on the top leaf surfaces of the rice crop and the estimated time when dew reached the zenith angle of 60 degrees on the ball. This relationship gave as accurate an estimation of dew duration on the top leaf surface of the rice crop as did the Penman-Monteith combination equation. This study showed that the dewball is a potentially useful device for observing dew formation.

Quantification of Mycelium of Botrytis spp. and the Antagonist Ulocladium atrum in Necrotic Leaf Tissue of Cyclamen and Lily by Fluorescence Microscopy and Image Analysis.

ABSTRACT A technique was developed to localize and quantify the internal mycelial colonization of necrotic leaf tissue of cyclamen (Cyclamen persicum) or lily (Lilium) by pathogenic Botrytis spp. and the antagonist Ulocladium atrum. This technique allows investigation of competitive substrate colonization by both fungi, which is a key process for biological control of Botrytis spp. by U. atrum. A combination of differential fluorescent labeling and image analysis was applied on cryostat sections of necrotic leaf tissue. Botrytis mycelium was labeled specifically by indirect immunofluorescence using a monoclonal antibody specific for Botrytis spp. And an antimouse fluorescein conjugate. Wheat germ agglutinin conjugated to the fluorochrome TRITC was used to label mycelium of both fungi. Image analysis was used to measure the relative surface area of the cryostat section covered by fluorescing hyphae of Botrytis spp. and by fluorescing hyphae of both fungi. A mathematical conversion was derived and used to calculate the relative mycelial volume of each fungal species in the necrotic tissue based on the measured relative surface areas. Temporal aspects of substrate colonization were studied in a short time series. An analysis of components of variance provided insight into spatial colonization patterns for the fungal species involved and allowed the design of efficient sampling strategies for future experiments.

Global climate change: modelling the potential responses of agro-ecosystems with special reference to crop protection.

Pests and diseases reduce yields to lower levels than those that could have been potentially obtained, given the restrictions of climate, nutrients and crop varieties. Climatic change not only affects the potential yield levels, but it may also modify the effects of pests and diseases. Modelling can serve as a tool to integrate these processes, ranging from simple removal of plant material to subtle toxic and hormonal effects. Modelling can help to quantify different modes of action such as on photosynthesis, root activity, assimilate partitioning, morphology, and their interactions. As to climatic change, little is known about pests, diseases and weeds. If climatic change causes a gradual shift of agricultural regions, crops and their associated pests, diseases and weeds will migrate together, though at different rates maybe. To a limited extent, new outbreaks can be foreseen given the changed environmental conditions. Methodology is available, and some interesting results are on record. Specific changes such as an increase in the CO(2) content in the air and in UV radiation are not likely to have large effects. Increasing atmospheric CO(2) reduces crop nitrogen content, which may retard many pests and diseases, and change the composition of the weed flora which accompanies crops. Some cautionary remarks are made to avoid jumping to conclusions.

Assessing the greenhouse effect in agriculture.

Evidence that concentrations of CO2 and trace gases in the atmosphere have increased is irrefutable. Whether or not these increased concentrations will lead to climate changes is still open to debate. Direct effects of increased CO2 concentrations on physiological processes and individual plants have been demonstrated and the consequences for crop growth and production under various circumstances are evaluated with simulation models. The consequences of CO2 enrichment are considerable under optimal growing conditions. However, the majority of crops are grown under sub-optimal conditions where the effects of changes in CO2 are often less. The same holds for the possible indirect effects of environmental changes such as temperature rise. Studies on individual plants under optimal conditions are therefore not sufficient for evaluating the effects at a farm, regional, national or supra-national level. Simulation studies help to bridge the gap between the various aggregation levels and provide a basis for various studies of policy options at various aggregation levels.

The effects of long-term open-air fumigation with SO2 on a field crop of broad bean (Vicia faba L.) II Effects on growth components, leaf area development and elemental composition.

Faba bean crops (Vicia faba L.) were exposed to elevated SO2 concentrations in three different years in an open-air field exposure system for the controlled release of air pollutants. The treated crops were exposed to an average SO, concentration of 165µg m-3 in 1985, 62µg m-3 in 1986 and 74µg m-3 in 1988. The ambient SO2 concentration was about 10 µg m-3 . Plant height, number of internodes and number of pods were not affected by SO2 . The specific leaf area was reduced in the plants exposed to SO2 at the end of the growing season. Leaf area development was strongly affected during the pod-filling period in 1985 and 1988 as a result of leaf injury and defoliation in the fumigated plots. In 1986 a similar trend in leaf area reduction was observed in the early reproductive phase. N and Mg content of the different organs was unaffected by SO2 . The S content was strongly elevated in the leaves and pods of the fumigated plants, and the Ca content of the leaves was reduced by SO2 . Chlorophyll content of different leaf numbers was unaffected by SO2 .

The effects of long-term open-air fumigation with SO2 on a field crop of broad bean (Vicia faba L.) I. Depression of growth and yield.

In an open-air Held exposure system for the controlled release of air pollutants, broad bean (Vida faba L.) crops were exposed to elevated SO2 concentrations in three growing seasons, in order to analyse the effects on crop growth under field conditions. The treated plots were exposed to a mean concentration of 165µgm-3 in 1985, 62µgm -3 in 1986 and 74µgm-3 in 1988. The background concentration was about 10µ m-3 . A reasonably uniform distribution of SO2 concentration was obtained over an area of 8m × 8m and concentrations exceeding the target concentration were rare. In 1985 and 1988, the growth rate of the crop was depressed at the end of the pod-filling period. This resulted in a reduction of total dry-matter production of 17% in 1985 and 9% in 1988, and a seed yield reduction of 23% in 1985 and 10% in 1988. In 1986, dry matter growth was not analysed up to the end of the growing season due to a severe infection of Botrytis fabae (Choclate spot disease) infection in the control plot in the middle of the pod-filling period. Slight B. fabae infections in the control plots only were also observed in 1985 and 1988. In all experiments no significant reductions of dry matter growth were observed in the vegetative and early reproductive phases.

Physical and morphological constraints on transport in nodules.

For active nodule nitrogen fixation, O(2), N(2), and carbohydrate must be transported throughout the nodule. No quantitative analysis of these transport processes in the nodules has been presented. By invoking several simplifying assumptions, a second-order differential equation for the various gradients and concentrations in the nodule was solved. Even though the nodule can only be approximated in this analysis, it indicates clearly that intercellular gas spaces must exist in nodules for adequate O(2) distribution. To preserve low O(2) concentrations and protect the nitrogenase, these gas spaces cannot be in direct contact with the ambient atmosphere. It is hypothesized that a gas barrier exists in the cortical region of the nodule to limit O(2) diffusion. This barrier would not substantially inhibit N(2) transport. Carbohydrate transport from the vascular tissue via diffusion in the liquid phase can adequately accommodate the requirements within the nodule.

An elementary model of nitrogen uptake and redistribution by annual plant species.

A model is presented that simulates nitrogen uptake and response to nitrogen deficiency by a growing annual plant canopy. It is a descriptive model as it is not based on a detailed definition of the biochemical processes involved. It does incorporate a considerable amount of experimental knowledge about these processes as well as some tentative concepts concerning the availability of soil nitrate and the relation between rates of growth, death and nitrogen translocation to the seeds. The model simulates the effect of nitrogen deficiency on plant growth, seed development, death of vegetative tissues and changes in the nitrogen concentration of the different plant parts. The results warrant a verification and development study under specific field conditions. The model is meant to be used in conjunction with another model that simulates the water balance and transpiration of an annual plant canopy under moisture limiting conditions. The nitrogen balance in the soil is not yet treated in either model.

An elementary model of nitrogen uptake and redistribution by annual plant species.

A model is presented that simulates nitrogen uptake and response to nitrogen deficiency by a growing annual plant canopy. It is a descriptive model as it is not based on a detailed definition of the biochemical processes involved. It does incorporate a considerable amount of experimental knowledge about these processes as well as some tentative concepts concerning the availability of soil nitrate and the relation between rates of growth, death and nitrogen translocation to the seeds. The model simulates the effect of nitrogen deficiency on plant growth, seed development, death of vegetative tissues and changes in the nitrogen concentration of the different plant parts. The results warrant a verification and development study under specific field conditions. The model is meant to be used in conjunction with another model that simulates the water balance and transpiration of an annual plant canopy under moisture limiting conditions. The nitrogen balance in the soil is not yet treated in either model.