Detection of lead in Zea mays by dual-energy X-ray microtomography at the SYRMEP beamline of the ELETTRA synchrotron and by atomic absorption spectroscopy.

This study is related to the application of the X-ray dual-energy microradiography technique together with the atomic absorption spectroscopy (AAS) for the detection of lead on Zea mays stem, ear, root, and leaf samples. To highlight the places with lead intake, the planar radiographs taken with monochromatic X-ray radiation in absorption regime with photon energy below and above the absorption edge of a given chemical element, respectively, are analyzed and processed. To recognize the biological structures involved in the intake, the dual-energy images with the lead signal have been compared with the optical images of the same Z.

Expression and characterisation in E. coli of mutant forms of saporin.

In the present communication, we report on the expression and characterisation in Escherichia coli of mutant derivatives of saporin, a type 1 ribosome-inactivating protein from Saponaria officinalis L. The effects of substitution of Glu 176 with Lys and those of deletion of 19 amino acids at the C-terminal were evaluated both in vivo, testing the influence of expressed proteins on bacterial growth and in vitro measuring their N-glycosidase and supercoiled DNA relaxation activities. Results indicate that both modifications of the wild-type protein abolish its toxicity to bacterial cells and impair its enzymatic activity on polynucleotide substrates, either RNA or DNA.

Differences in X-ray absorption due to cadmium treatment in Saponaria officinalis leaves.

A method for detecting cadmium uptake in leaves of Saponaria officinalis doped with a solution of cadmium acetate is described. The technique based on the exposure of dried leaves to X-rays of a wavelength close to that of the metal K-edge could be useful for phytoremediation studies as it could reveal the bioaccumulation in plants due to the treatment either in vivo or in vitro with heavy metals. X-ray microradiography measurements are in agreement with those from peroxidase enzyme assay utilized to follow the oxidative damage induced by heavy metals.

Lead acetate genotoxicity on human melanoma cells in vitro.

In this study, chromosomal damage induced in vitro by lead acetate in human melanoma cells (B-Mel) was evaluated using the cytokinesis-blocked micronucleus assay and sister chromatid exchange (SCE) analysis. Lead acetate (10-6, 10-5 and 10-3 mM) induced micronuclei and SCE formation in a dose-dependent manner. Treated cells showed a decrease in cell viability but not concomitant cell death by apoptosis (lead acetate failed to induce internucleosomal DNA fragmentation at any of the doses tested).