Hubert Th. Wolterbeek

Strategies in sampling and sample handling in the context of large-scale plant biomonitoring surveys of trace element air pollution

Aspects of sampling and sample handling in the context of large-scale plant biomonitoring surveys of trace element air pollution are addressed. Topics such as survey goals and planning, choice of elements, biomonitor species (lichens, mosses, bark), interspecies calibration, SO2 effects, local variation, comparability of results, sample homogeneity, the problem of soil-derived elements, and elemental analysis are discussed. The paper stresses the need for stringent accuracy control, indicates the importance of local variation in the concept of the survey, and underlines the relevance of multi-elemental analysis. Furthermore, factor analysis is indicated as a powerful mathematical tool in dealing with the presence of both soil particle contamination and soil-derived absorbed elements.

Predicting metal toxicity revisited: general properties vs. specific effects.

The present paper addresses the prediction of metal toxicity by evaluation of the relationships between general metal properties and toxic effects. For this, metal toxicity data were taken from 30 literature data sets, which varied largely in exposure times, organisms, effects and effect levels. General metal properties were selected on basis of literature reviewing of basic metal property classifications: used were the electrochemical potential deltaE0; the ionization potential IP; the ratio between atomic radius and atomic weight AR/AW; and the electronegativity Xm. The results suggest that toxicity prediction may be performed on basis of these fixed metal properties without any adoption to specific organisms, without any division of metals into classes, or grouping of toxicity tests. The results further indicate that metal properties contribute to the observed effects in relative importances which depend on specific effects, effect levels, exposure times, selected organisms and ambient conditions. The discussion strongly suggests that prediction should be by interpolation rather than by extrapolation of calibrated toxicity data: the concept here is that unknown metal toxicities are predicted on basis of observed metal toxicities in calibration experiments. Considering the used metal properties, the calibration covers the largest number of metals by the simultanuous use of Ge(IV), Cs(I), Li(I), Mn(VII), Sc and Bi in toxicity studies. Based on the data from the 30 studies considered, metal toxicities could be ordered in a relative way. This ordering indicates that the natural abundance of metals or metal ions in the Earths crust may be regarded as a general comparative measure of the metal toxicities. The problems encountered in toxicity interpretation and ordering of toxicities indicate that control of the solution acidity, the metals solubility and the metals oxidation state may be key problems to overcome in future metal ion toxicity studies.

Lanthanide(III) Complexes of Bis(phosphonate) Monoamide Analogues of DOTA : Bone-Seeking Agents for Imaging and Therapy

Lanthanide complexes of DOTA derivatives 2a (BPAMD) and 2b (BPAPD), having a monoamide pendant arm with a bis(phosphonate) moiety, were comparatively tested for application in MRI, radiotherapy, and bone pain palliation. (1)H, (31)P, and (17)O NMR spectroscopy show that they are nine-coordinated, with one water molecule in the first coordination sphere of the Ln(III) ion. The bis(phosphonate) moieties are not coordinated to the lanthanide and predominantly mono- and diprotonated at physiological pH. The parameters governing the longitudinal relaxivities of the Gd complexes are similar to those of other monoamides of DOTA reported in the literature. Upon adsorption on hydroxyapatite, the relaxivities at 20 MHz and 25 degrees C of Gd-2a and Gd-2b were 22.1 and 11 s(-1) mM(-1), respectively. An in vivo gamma-ray imaging study showed that the (177)Lu complexes of 2a and 2b have a high affinity for bones, particularly for growth plates and teeth with a prolonged retention.

Assessing the quality of biomonitoring via signal-to-noise ratio analysis

Abstract The analysis of the signal-to-noise ratio of a survey is introduced as a means to assess the quality of a survey. Here, the survey signal is defined as the survey variance, and the survey noise is determined by measurement of the local variance (variance per site). The signal-to-noise ratio, and thus the quality of the survey, can be improved by factor analysis aided processing of the data. This is illustrated by processing data from various biomonitoring programs on trace element air pollution. Clean-up of the data-set, in which a bias-introducing contribution is removed (for example, the soil factor) or source profile isolation, in which attention is focussed on a single source, yield strikingly different indications of the quality (or suitability) of the biomonitoring species when compared with the indications obtained from the original dataset. The approach presented here stresses that the quality of a survey largely depends on the decisions taken with respect to the selection of the biomonitor material; these decisions should be based on optimization of the signal-to-noise ratio rather than on minimization of the noise only.

Complexes of DOTA−Bisphosphonate Conjugates: Probes for Determination of Adsorption Capacity and Affinity Constants of Hydroxyapatite

The adsorption on hydroxyapatite of three conjugates of a bisphosphonate and a macrocycle having C1, C2, and C3 spacers and their terbium complexes was studied by the radiotracer method using 160Tb as the label. The radiotracer-containing complex of the conjugate with the C3 spacer was used as a probe for the determination of the adsorption parameters of other bisphosphonates that lack a DOTA unit. A physicochemical model describing the competitive adsorption was successfully applied in the fitting of the obtained data. The maximum adsorption capacity of bisphosphonates containing bulky substituents is determined mainly by their size. For bisphosphonates having no DOTA moiety, the maximum adsorption capacity is determined by the electrostatic repulsion between negatively charged bisphosphonate groups. Compounds with a hydroxy or amino group attached to the alpha-carbon atom show higher affinities. Macrocyclic compounds containing a short spacer between the different bisphosphonic acid groups and the macrocyclic unit exhibit high affinities, indicating a synergic effect of the bisphosphonic and the macrocyclic groups during adsorption. The competition method described uses a well-characterized complex and allows a simple evaluation of the adsorption behavior of bisphosphonates. The application of the macrocycle-bisphosphonate conjugates allows easy radiolabeling via complexation of a suitable metal isotope.

Molybdenum Incorporation in Tungsten Aldehyde Oxidoreductase Enzymes from Pyrococcus furiosus

The hyperthermophilic archaeon Pyrococcus furiosus expresses five aldehyde oxidoreductase (AOR) enzymes, all containing a tungsto-bispterin cofactor. The growth of this organism is fully dependent on the presence of tungsten in the growth medium. Previous studies have suggested that molybdenum is not incorporated in the active site of these enzymes. Application of the radioisotope (99)Mo in metal isotope native radioautography in gel electrophoresis (MIRAGE) technology to P. furiosus shows that molybdenum can in fact be incorporated in all five AOR enzymes. Mo(V) signals characteristic for molybdopterin were observed in formaldehyde oxidoreductase (FOR) in electron paramagnetic resonance (EPR)-monitored redox titrations. Our finding that the aldehyde oxidation activity of FOR and WOR5 (W-containing oxidoreductase 5) correlates only with the residual tungsten content suggests that the Mo-containing AORs are most likely inactive. An observed W/Mo antagonism is indicative of tungstate-dependent negative feedback of the expression of the tungstate/molybdate ABC transporter. An intracellular selection mechanism for tungstate and molybdate processing has to be present, since tungsten was found to be preferentially incorporated into the AORs even under conditions with comparable intracellular concentrations of tungstate and molybdate. Under the employed growth conditions of starch as the main carbon source in a rich medium, no tungsten- and/or molybdenum-associated proteins are detected in P. furiosus other than the high-affinity transporter, the proteins of the metallopterin insertion machinery, and the five W-AORs.

Effect of particulate matter, atmospheric gases, temperature, and humidity on respiratory and circulatory diseases’ trends in Lisbon, Portugal

This study addresses the significant effects of both well-known contaminants (particles, gases) and less-studied variables (temperature, humidity) on serious, if relatively common, respiratory and circulatory diseases. The area of study is Lisbon, Portugal, and time series of health outcome (daily admissions in 12 hospitals) and environmental data (daily averages of air temperature, relative humidity, PM10, SO2, NO, NO2, CO, and O3) have been gathered for 1999–2004 to ascertain (1) whether concentrations of air pollutants and levels of temperature and humidity do interfere on human health, as gauged by hospital admissions due to respiratory and circulatory ailments; and (2) whether there is an effect of population age in such admissions. In general terms, statistically significant (p < 0.001) correlations were found between hospital admissions and temperature, humidity, PM10, and all gaseous pollutants except CO and NO. Age appears to influence respiratory conditions in association with temperature, whereas, for circulatory conditions, such an influence likely involves temperature as well as the gaseous pollutants NO2 and SO2.

Estimating the inhaled dose of pollutants during indoor physical activity.

BACKGROUND It is undeniable that many benefits come from physical activity. People exercise in fitness centers to improve their health and well-being, prevent disease and to increase physical attractiveness. However, these facilities join conditions that cause poor indoor air quality. Moreover, increased inhalation rates during exercise have influence on inhaled doses of air pollution. OBJECTIVES This study aims to calculate the inhaled dose of air pollutants during exercise, by estimating minute ventilation of participants and measuring air pollutant concentrations in fitness centers. METHODS Firstly, the 20 participants performed an incremental test on a treadmill, where heart rate and minute ventilation were measured simultaneously to develop individual exponential regression equations. Secondly, heart rate was measured during fitness classes and minute ventilation was estimated based on the calculated regression coefficients. Finally, the inhaled dose of air pollutants was calculated using the estimated minute ventilation and the concentrations of the pollutants measured in a monitoring program performed in 63 fitness classes. RESULTS Estimated inhaled doses were higher in aerobic classes than in holistic classes. The main difference was registered for PM10 inhaled dose that presented an average ratio between aerobic and holistic classes greater than four. Minute ventilation and PM10 concentrations in aerobic classes were, on average, 2.0 times higher than in holistic classes. Results showed that inhalation of pollutants is increased during heavy exercise, demonstrating the need to maintain high indoor air quality in fitness centers. CONCLUSIONS This study illustrates the importance of inclusion minute ventilation data when comparing inhaled doses of air pollution between different population groups. This work has estimated for the first time the minute ventilation for different fitness classes. Also constitutes an important contribution for the assessment of inhaled dose in future studies to be performed in fitness centers.

Uptake kinetics of 99Tc in common duckweed

The uptake of the nuclear waste product technetium-99 was studied in common duckweed (Lemna minor). In addition to measurements, a model involving two compartments in duckweed with different chemical forms of technetium was derived. The model was tested by chemical speciation, i.e. differentiating between reduced Tc-compounds and Tc(VII)O(4)(-). The TcO(4)(-) concentrations measured were in good agreement with those predicted by the model. Two processes determine technetium uptake: (1) transport of Tc(VII)O(4)(-) across the cell membrane, and (2) reduction of Tc(VII). The TcO(4)(-) concentration in duckweed reaches a steady state within 2 h while reduced Tc-compounds are stored, as a result of absence of release or re-oxidation processes. Bioaccumulation kinetic properties were derived by varying 99Tc concentration, temperature, nutrient concentrations, and light intensity. The reduction of technetium in duckweed was highly correlated with light intensity and temperature. At 25 degrees C the maximum reduction rate was observed at light intensities above 200 µmol m(-2) s(-1) while half of the maximum transformation rate was reached at 41 µmol m(-2) s(-1). Transport of TcO(4)(-) over the cell membrane requires about 9.4 kJ mol(-1), indicating an active transport mechanism. However, this mechanism behaved as first-order kinetics instead of Michaelis-Menten kinetics between 1x10(-14) and 2.5x10(-5) mol l(-1) TcO(4)(-). Tc uptake could not be inhibited by 10(-3) mol l(-1) nitrate, phosphate, sulphate or chloride.

Polymersomes as radionuclide carriers loaded via active ion transport through the hydrophobic bilayer

Vesicles composed of amphiphilic block copolymers (i.e. polymersomes) have already been shown to have great potential in drug delivery. Nuclear imaging techniques such as Single Photon Emission Computed Tomography (SPECT) are indispensable in the correct evaluation of biodistribution and pharmacokinetics of newly or not fully investigated polymersome formulations. However, to date, polymer vesicles, in contrast to their lipid counterparts, have not been loaded with radionuclides. In this paper, we have investigated the so-called active loading method to trap radionuclides into preformed polymersomes composed of poly(butadiene-b-ethylene oxide) having variable membrane and brush thickness. We have used tropolone as a lipophilic agent to transport the radioactive isotope of indium, 111In, through the hydrophobic membrane into the aqueous cavity containing the strong hydrophilic chelate diethylene triamine pentaacetic acid (DTPA). The results show that a high loading efficiency of 111In3+ (>85%) can be achieved at short incubation times in polymersomes with membrane thicknesses twice the size of typical lipid bilayers. However, increasing the molecular weight of the block copolymers results in a lower radiolabelling efficiency and a much slower loading rate. In addition, both the DTPA and tropolone concentrations have been found to influence the loading efficiency. Finally, we not only demonstrate that a significant amount of this radioisotope can be successfully encapsulated in the polymersomes, but also report that a negligible loss (<5% in 48 hours) is observed, allowing their safe application in future in vivo studies.