Polar organic chemical integrative samplers as an effective tool for chemical monitoring of surface waters - Results from one-year monitoring in France.

In an effort to support European Union Water Framework Directive goals, we have set up a national demonstrator project to identify the advantages and limitations of passive samplers for regulatory monitoring of polar contaminants in surface waters. Here we carried out successive 14 day-deployments of polar organic chemical integrative samplers (POCIS) for one year at three sites. In parallel, we used the passive sampler deployment/retrieval operations to collect spot water samples for comparative analysis. We observed that frequency of quantification was significantly higher in POCIS than spot samples for 29 contaminants, similar for 15, and lower for one, because POCIS lowered the limits of quantification for most contaminants (median value factor of 11). We built a database of sampling rates (Rs) according to quality indices to convert concentrations in POCIS to concentrations in water (23 contaminants with a high-quality median Rs value, 20 with an approximate Rs and two with no usable Rs). Several phenomena were observed over one-year monitoring period. For example, after a flood episode, dilution phenomenon in rivers is correctly observed by using POCIS sampling whereas significant concentration increased due to soil leaching is observed with both passive and spot sampling. Cases of episodic contamination that were missed by spot sampling were observed with POCIS as it was able to capture contamination of short duration but sufficient intensity. Contamination by pharmaceuticals was found to come from wastewater treatment plant discharges and showed relatively little variation over the course of the year in both POCIS and spot samples. POCIS enables more reliable annual monitoring of pesticide and pharmaceutical contamination than spot sampling. Furthermore, POCIS also improves the environmental quality standards based assessment of chemical status and on annual average concentrations compared to spot sampling. This study demonstrates the value and practicability of POCIS-based chemical monitoring for use in regulatory control networks.

Metal measurement in aquatic environments by passive sampling methods: Lessons learning from an in situ intercomparison exercise.

Passive sampling devices (PS) are widely used for pollutant monitoring in water, but estimation of measurement uncertainties by PS has seldom been undertaken. The aim of this work was to identify key parameters governing PS measurements of metals and their dispersion. We report the results of an in situ intercomparison exercise on diffusive gradient in thin films (DGT) in surface waters. Interlaboratory uncertainties of time-weighted average (TWA) concentrations were satisfactory (from 28% to 112%) given the number of participating laboratories (10) and ultra-trace metal concentrations involved. Data dispersion of TWA concentrations was mainly explained by uncertainties generated during DGT handling and analytical procedure steps. We highlight that DGT handling is critical for metals such as Cd, Cr and Zn, implying that DGT assembly/dismantling should be performed in very clean conditions. Using a unique dataset, we demonstrated that DGT markedly lowered the LOQ in comparison to spot sampling and stressed the need for accurate data calculation.

Bottom trawling resuspends sediment and releases bioavailable contaminants in a polluted fjord.

Sediments are sinks for contaminants in the world's oceans. At the same time, commercial bottom trawling is estimated to affect around 15 million km(2) of the world's seafloor every year. However, few studies have investigated whether this disturbance remobilises sediment-associated contaminants and, if so, whether these are bioavailable to aquatic organisms. This field study in a trawled contaminated Norwegian fjord showed that a single 1.8 km long trawl pass created a 3-5 million m(3) sediment plume containing around 9 t contaminated sediment; ie. 200 g dw m(-2) trawled, equivalent to c. 10% of the annual gross sedimentation rate. Substantial amounts of PCDD/Fs and non-ortho PCBs were released from the sediments, likely causing a semi-permanent contaminated sediment suspension in the bottom waters. PCDD/Fs from the sediments were also taken up by mussels which, during one month, accumulated them to levels above the EU maximum advised concentration for human consumption.

Migration of enteric neural crest cells in relation to growth of the gut in avian embryos.

Neural crest cell migration in the gut and the growth of the mid- and hindgut of avian embryos was investigated by a combination of whole-mount immunofluorescence of the HNK-1 neural crest marker epitope, chorioallantoic membrane grafting and morphometry. HNK-1-labelled cells advanced rostrocaudally in the gut of quail embryos (to the duodenum by stage HH 21, to the umbilicus by HH 25, to the ceca by HH 27, to the cloaca by HH 33). The timetable in chick embryos appeared to be slightly slower, but neural cells were obscured by background fluorescence in this species. More rostral regions of the gut commenced rapid growth earlier than more caudal regions (preumbilical small intestine after HH 26, postumbilical small intestine after HH 27 and colorectum after HH 28), and the small intestine and ceca grew most rapidly in length while the colorectum grew most rapidly in diameter. The rates of growth of the gut were low prior to the stage when HNK-1-labelled cells normally arrive in the small intestine, ceca and rostral colorectum, but increased dramatically after arrival. In the caudal colorectum rapid growth had commenced at the time of arrival of these cells. These data are consistent with the idea that a delay in arrival of vagal neural crest cells at any point in the intestine could jeopardize the ability of the cells to fully populate the remainder of the gut, due to the normal growth spurt causing the migration end-point to recede faster than the rate of neural crest cell migration. Thus, a mismatch in timing of neural crest cell migration and gut growth could play a role in the etiology of some forms of Hirschsprung's disease.

Accumulation of exogenous catecholamines in the neural tube and non-neural tissues of the early fowl embryo : Correlation with morphogenetic movements.

Catecholamines (CA) were localized in stage 11-34 domestic fowl embryos by the formaldehyde-induced fluorescence (FIF) method after exposure in vivo or in vitro to CA (noradrenaline or α-methylnoradrenaline), or the CA precursorl-DOPA. The effects of drugs known to alter CA metabolism in the adult were also investigated.Negligible FIF was observed in embryos which had not been exposed to CA. After CA loading, FIF could be seen in the neural tube and in non-neural tissues such as the notochord and gut mesenchyme and to a lesser degree in suprarenal area tissue, liver endothelium, sclerotome, and myotome. This FIF was inhibited by desmethylimipramine, a blocker of adult neuronal CA uptake (Uptake1), but not by corticosterone, a blocker of adult extraneuronal CA uptake (Uptake2). The notochord, dorsal pancreas and some blood cells were fluorescent afterl-DOPA loading, and this FIF could be greatly diminished by the DOPA decarboxylase inhibitor RO4-4602.The pattern of FIF in the axial structures (neural tube and notochord) correlated with axial flexure in both position and time, and the intensity of fluorescence was strongest cranially and caudally, where flexure is most pronounced. The FIF in gut mesenchyme cells was closely related to the movement of the intestinal protals during early gut tube formation, and to the regions of the developing intestine that undergo intense morphogenesis during their early formation.

Differentiation of sympathetic and enteric neurons of the fowl embryo in grafts to the chorio-allantoic membrane.

Sympathetic cells (adrenergic neurons, SIF cells and chromaffin cells) and enteric neurons differentiate from migratory cells derived from the neural crest. The development of these cell types was studied in chorio-allantoic membrane (CAM) grafts, using combinations of tissue from domestic fowl embryos. Neural anlagen (neural tube and crest) of the vagal, cervico-thoracic and lumbo-sacral axial levels were equally capable of sympathetic differentiation, but this required somitic tissue for its significant expression. However, the vagal somites possessed only slight sympathogenic activity, thereby accounting for the negligible contribution of the vagal neural crest to the sympathetic nervous system. The same three levels of the neural anlage could furnish enteric neurons when combined directly with the aneuronal colo-rectum. However, the scale of this line of differentiation varied with the level of origin of the neural anlage, in contrast to the apparent equivalence in the ability to diffentiate as sympathetic cells. The density of enteric neurons in combinations with the vagal neural anlage was estimated as 60 times greater than the neuron density in combinations with the cervico-thoracic neural anlage. The lumbo-sacral neural anlage gave results similar to those of the cervico-thoracic level. Moreover, neural crest-derived pigment cells, positioned ectopically in the wall of the colo-rectum, were rare in combinations with the vagal neural anlage, but common in grafts with the other levels. When tested physiologically, the colo-rectum grown with the vagal neural anlage showed non-adrenergic, non-cholinergic inhibitory nervous activity in addition to the expected cholinergic excitatory responses. The neurons derived directly from vagal neural anlagen were similar to those that had reached the colo-rectum via their normal migratory pathways, when studied in terms of histological appearance, density of distribution and physiological responses.

A procedure for the rapid freezing of whole embryos.

A procedure for the rapid freezing of whole chick embryos for histochemical treatment is described. The problems of deformation during preparation for quenching and orientation for sectioning have been largely overcome by placing embryos inside lengths of chicken trachea. The subsequent disorientation of tissues that follows cracking and shattering due to the rapid freezing of whole embryos is avoided. The method permitted a more precise identification of the position and time of appearance of formaldehyde-induced fluorescence and myosin antibody immunofluorescence in serially sectioned embryos.

Catecholamine accumulation in neural crest cells and the primary sympathetic chain.

Catecholamine accumulation in chick embryos of stages 16 to 24 was investigated using formaldehyde-induced fluorescence. Fluorescence first appeared at stage 21 in the anterior sympathetic chain. After L-DOPA treatment, this fluorescence appeared at stage 18. Noradrenaline could not advance the onset of fluorescence or reconstitute fluorescence after its depletion by reserpine at stages 22 to 24. Under no conditions could fluorescence be identified in neural crest cells prior to their aggregation to form the primary sympathetic chain. Noradrenaline induced fluorescence in the neural tube, notochord, myotome, sclerotome, gut mesenchyme and suprarenal cortical cells. In addition to these structures, the dorsal pancreas and some blood cells were fluorescent after l-DOPA treatment. The implication of the results for the neural crest origin of APUD (Amine Precursor Uptake Decaboxylase) cells is considered.

Extraneuronal effects of 6-hydroxydopamine and extraneuronal uptake of noradrenaline. In-vivo and in-vitro studies on adrenocortical cells of lizards and rats.

6-hydroxydopamine (6-OHDA) was shown to cause ultrastructural changes in adrenocortical cells of lizards and rats. These changes comprised the formation of dense bodies with lamellar and crystalloid patterns, a decrease in the number of mitochondria and structural alterations of mitochondria. Alterations in adrenomedullary cells were not affected as a rule. Only in young animals did 6-OHDA cause deposits of an electron-dense material in medullary cells. An attempt was made to obtain information on amine uptake into cortical cells using the Falck-Hillarp technique to analyse the in-vivo and in-vitro uptake of noradrenaline (NA) into the adrenal cortex in adult rats. Extraneuronal uptake into heart and spleen was studied as well. Our results suggest that NA is taken up into cortical cells, particularly into nuclei, after exposure to 10(-4) gm/ml in-vitro indicating that uptake of 6-OHDA is also likely. Investigations using labelled 6-OHDA is also likely. Investigations using labelled 6-OHDA are required for further elucidating its extraneuronal uptake.