Enhanced phytoextraction of uranium and selected heavy metals by Indian mustard and ryegrass using biodegradable soil amendments.

The applicability of biodegradable amendments in phytoremediation to increase the uptake of uranium (U), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn) by Indian mustard (Brassica juncea) and ryegrass (Lolium perenne) was tested in a greenhouse experiment. Plants were cultivated during one month on two soils with naturally or industrially increased contaminant levels of U. Treatments with citric acid, NH4-citrate/citric acid, oxalic acid, S,S-ethylenediamine disuccinic acid (EDDS) or nitrilotriacetic acid (NTA) at a rate of 5 mmol kg(-1) dry soil caused increases in soil solution concentrations that were up to 18 times higher for U and up to 1570 times higher for other heavy metals, compared to the controls. Shoot concentrations increased to a much smaller extent. With EDDS, 19-, 34-, and 37-fold increases were achieved in shoots of Indian mustard for U, Pb and Cu, respectively. The increases in plant uptake of Cd, Cr and Zn were limited to a factor of four at most. Ryegrass generally extracted less U and metals than Indian mustard. Despite a marked increase of U and metal concentrations in shoots after addition of amendments, the estimated time required to obtain an acceptable reduction in soil contaminant concentrations was impractically long. Only for Cu and Zn in one of the studied soils, could the Flemish standards for clean soil theoretically be attained in less than 100 years.

Effect of biodegradable amendments on uranium solubility in contaminated soils.

Chelate-assisted phytoextraction has been proposed as a potential tool for phytoremediation of U contaminated sites. In this context, the effects of five biodegradable amendments on U release in contaminated soils were evaluated. Three soils were involved in this study, one with a relatively high background level of U, and two which were contaminated with U from industrial effluents. Soils were treated with 5 mmol kg(-1) dry weight of either citric acid, NH(4)-citrate/citric acid, oxalic acid, S,S-ethylenediamine disuccinic acid or nitrilotriacetic acid. Soil solution concentration of U was monitored during 2 weeks. All amendments increased U concentration in soil solution, but citric acid and NH(4)-citrate/citric acid mixture were most effective, with up to 479-fold increase. For oxalic acid, S,S-ethylenediamine disuccinic acid and nitrilotriacetic acid, the increase ranged from 10-to 100-fold. The highest concentrations were observed 1 to 7 days after treatment, after which U levels in soil solution gradually decreased. All amendments induced a temporary increase of soil solution pH and TOC that could not be correlated with the release of U in the soil solution. Thermodynamic stability constants (log K) of complexes did not predict the relative efficiency of the selected biodegradable amendments on U release in soil solution. Amendments efficiency was better predicted by the relative affinity of the chelate for Fe compared to U.

Method of diffusive gradients in thin films (DGT) compared with other soil testing methods to predict uranium phytoavailability.

The measurement of diffusive gradients in thin films (DGT) has been proposed as a surrogate for metal uptake by plants. A small-scale experiment was performed to test the predictive capacity of the DGT method with respect to uranium availability and uptake by ryegrass. Correlation analyses were performed to compare the results obtained with the DGT device with more conventional bioavailability indices - concentration of uranium in pore water or in selective extracts. Six soils with different uranium contamination history and with distinct soil characteristics were used for the availability tests and the uptake experiment. The four uranium bioavailability indices screened were highly correlated, indicating that at least partially comparable uranium pools were assessed. The uranium concentration in the pore water was a better predictor for uranium uptake by ryegrass than amounts of uranium recovered following extraction with 0.11 M CH3COOH or 0.4 M MgCl2, the fractions considered exchangeable according to, respectively, the BCR or NIST standardized sequential extraction methods. The DGT measured concentration, C(DGT), was also highly correlated with plant uptake but the significance level was sensitive to the value of the diffusion coefficient (pH depend or not) used to calculate C(DGT). From the results obtained it could not be concluded that the DGT method would have an additional value in assessing uranium bioavailability.

Plant-induced changes in soil chemistry do not explain differences in uranium transfer.

A greenhouse experiment was set up with maize, ryegrass, Indian mustard, wheat and pea to evaluate to what extent differences in uranium (U) transfer factors can be explained by root-mediated changes in selected soil properties. The experiment involved an acid and an alkaline soil contaminated with (238)U. U soil-to-shoot transfer factors (TFs) ranged between 0.0005 and 0.021 on the acid soil and between 0.007 and 0.179 on the alkaline soil. Indian mustard showed the highest U uptake in shoots and maize the lowest. The root TFs, only available for the acid soil, ranged from 0.58 for maize and Indian mustard to 1.38 for ryegrass. The difference in U uptake between the two soils and the five plants was only partially explained by the different initial U concentrations in soil solution or differences in soil properties in the two soils. However, we obtained a significant relation for differences in shoot TFs observed between the two soils when relating shoot TFs with concentration of UO(2)(2+) and uranyl carbonate complexes in soil solution (R(2)=0.88). The physiological mechanisms by which root-to-shoot U transfer is inhibited or promoted seemed at least as important as the plant-induced changes in soil characteristics in determining soil-to-shoot TFs.

Ultrastructural study on nuclear bodies of the rat parotid glands.

Nuclear bodies of types I, II, III and IV are constantly present in rat parotid glands. They become apparent on the 21st day and afterwards. Type IV nuclear bodies were chiefly found in the striated ducts. Nuclei containing 3 and more nuclear bodies were found as early as the 3rd month, although only in the striated ducts. Nuclear bodies are not related to glycogen or DNA replication but probably to rRNA metabolism. This study leads to a better understanding of nuclear bodies modifications which can be observed ultrastructurally in human salivary glands pathology. Their increased number in some nuclei may be the expression of an alteration of the cell metabolism.

Diffusive gradient in thin FILMS (DGT) compared with soil solution and labile uranium fraction for predicting uranium bioavailability to ryegrass.

The usefulness of uranium concentration in soil solution or recovered by selective extraction as unequivocal bioavailability indices for uranium uptake by plants is still unclear. The aim of the present study was to test if the uranium concentration measured by the diffusive gradient in thin films (DGT) technique is a relevant substitute for plant uranium availability in comparison to uranium concentration in the soil solution or uranium recovered by ammonium acetate. Ryegrass (Lolium perenne L. var. Melvina) is grown in greenhouse on a range of uranium spiked soils. The DGT-recovered uranium concentration (C(DGT)) was correlated with uranium concentration in the soil solution or with uranium recovered by ammonium acetate extraction. Plant uptake was better predicted by the summed soil solution concentrations of UO(2)(2+), uranyl carbonate complexes and UO(2)PO(4)(-). The DGT technique did not provide significant advantages over conventional methods to predict uranium uptake by plants.

[The prognostic value of the histopathological diagnosis of salivary gland tumors. Current findings]. / Valeur pronostique du diagnostic histopathologique des tumeurs des glandes salivaires. Acquisitions nouvelles.

The argyrophil (Ag + NOR) staining for nucleolar organizer region (NORs) applied to a series of benign and malignant salivary tumours reveals some differences which can be useful for the prognosis of those tumours. This new technique may be of diagnostic help in equivocal small biopsies or in cytological samples.

[Prognostic value of the histopathological diagnosis of salivary gland tumors. New techniques]. / Valeur pronostique du diagnostic histopathologique des tumeurs des glandes salivaires. Acquisitions nouvelles.

The argyrophil (Ag+ NOR) staining for nucleolar organizer region (NORs) applied to a series of benign and malignant salivary tumours reveals some differences which can be useful for the prognosis of those tumours. This new technique may be of diagnostic help in equivocal small biopsies or in cytological samples.

Nuclear ultrastructure of human parotid gland tumors with special focus on nuclear bodies.

The purpose of our study was to determine the morphology and the proportion of NB in 20 human parotid gland tumors. Types I and III NB were observed in benign as well as malignant tumors. Some atypical forms ("onion-like" NB and NB with lipidic inclusions) were found in benign tumors. The proportion of nuclear profiles containing one and more NB varied from 0 to 60% in the benign tumors, and from 4 to 50% in the malignant tumors. Nuclei containing 3 and more NB were observed as well in the benign as in the malignant tumors. The NB ratio cannot be taken for a malignancy criteria.

[Ultrastructural bases for the synthesis of ribosomal RNA in the nuclei of the parotid gland. The role of intranuclear bodies]. / Bases ultrastructurales de la synthèse de l'ARN ribosomal dans les noyaux de la glande parotide. Rôle des corps intranucléaires.

Identification and numerations on electron microscopic samples of rat parotid glands revealed an unexpected high frequency of nuclear bodies in acini and in striated ducts. Three different morphological types of nuclear bodies were identified: type I corresponded to a circular outline of finely fibrillar or granular bodies. Type II exhibited an outer fibrillar cortex surrounding a central lucent core. Type III possessed a thick granular or fibrillar cortex surrounding dense granules. Type IV nuclear bodies appeared to be circumscribed by a thick lamellar cortex and contained dense and heavy stained granules. The biochemical content of the nuclear bodies mostly corresponds to proteins and it was possible to demonstrate slight quantities of RNA. Recent studies seem to confer to some of those nuclear bodies a possible role in RNA processing or transport. It is however peculiar to find nuclear bodies in striated ducts which are not involved in active protein synthesis as the acini.

Ultrastructure of the nuclear bodies in the human parotid gland.

The ultrastructure of 17 human parotid glands was studied in order to determine the features of the nuclear bodies and their possible relation to various pathological conditions. Types I and III nuclear bodies were frequently identified in acini and in striated ducts. Type IV nuclear bodies were seldom found. The percentage of nuclear sections containing nuclear bodies varied from 5.7 to 66.4 for the acini, and from 17.8 to 80% for the striated ducts. In 4 out of our 6 cases of chronic inflammation, numerous nuclear bodies were observed in the same nucleus. The increase in the number of nuclear bodies seemed to be related to an altered cell metabolism. In 3 cases, membranous type inclusions were found. This type of nuclear inclusion is quite different from the true nuclear bodies.