Emanuele Argese

Heavy metal contamination in the seaweeds of the Venice lagoon

The concentrations of heavy metals (Fe, Zn, Cu, Cd, Ni, Pb, Cr, As) were determined in seven seaweeds of environmental and commercial relevance (Ulva rigida C. Ag., Gracilaria gracilis (Stackhouse) Steentoft, L. Irvine and Farnham, Porphyra leucosticta Thuret, Grateloupia doryphora (Montagne) Howe., Undaria pinnatifida (Harv.) Suringar, Fucus virsoides J. Agardh, Cystoseira barbata (Good. et Wood.) Ag.) collected in four sampling sites in the lagoon of Venice, in spring and autumn 1999. Metals were extracted using hot concentrated acids in a Microwave Digestion Rotor and analysed by absorption spectrophotometry using a flame mode for Fe and Zn and a graphite furnace for Pb, Cr, Cd, Cu, Ni and As. High contamination levels, especially for Pb, were detected in Ulva and to a lesser extent in Gracilaria. Brown seaweeds, especially Cystoseira was highly contaminated by As. The least contaminated genera with all metals except As were Porphyra and Undaria. A concentration decrease for Zn and Cd was observed from the inner parts of the central lagoon, close to the industrial district, towards the lagoon openings to the sea.

Heavy metal and grain-size distributions in estuarine shallow water sediments of the Cona Marsh (Venice Lagoon, Italy)

Anthropogenic heavy metals and grain size were determined in 15 surface sediment samples from the Cona Marsh, an estuarine area of the Venice Lagoon (Italy). The investigation is based on separate analyses of both metal concentrations obtained with two acid extractions and particle-size percentages by laser light scattering. The grain size was also measured in sample aliquots previously submitted to the organic matter removal to disperse mineral-organic aggregates, visualized by scanning electron microscopy. These aggregates apparently shift the particle-size spectrum toward larger diameters, and the intimate association between metals and sediment particles is more evident after their dispersion. The comparison of the two distributions showed a strong correlation between heavy metals and finer particles content in the sediment (d < 7.8 μm). The investigation finally illustrated a spatial zoning of the marsh into three sectors with different degrees of pollution, in relation to the water circulation determined by river discharge and tidal forcing.

Proteomic analysis as a tool for investigating arsenic stress in Pteris vittata roots colonized or not by arbuscular mycorrhizal symbiosis.

Pteris vittata can tolerate very high soil arsenic concentration and rapidly accumulates the metalloid in its fronds. However, its tolerance to arsenic has not been completely explored. Arbuscular mycorrhizal (AM) fungi colonize the root of most terrestrial plants, including ferns. Mycorrhizae are known to affect plant responses in many ways: improving plant nutrition, promoting plant tolerance or resistance to pathogens, drought, salinity and heavy metal stresses. It has been observed that plants growing on arsenic polluted soils are usually mycorrhizal and that AM fungi enhance arsenic tolerance in a number of plant species. The aim of the present work was to study the effects of the AM fungus Glomus mosseae on P. vittata plants treated with arsenic using a proteomic approach. Image analysis showed that 37 spots were differently affected (21 identified). Arsenic treatment affected the expression of 14 spots (12 up-regulated and 2 down-regulated), while in presence of G. mosseae modulated 3 spots (1 up-regulated and 2 down-regulated). G. mosseae, in absence of arsenic, modulated 17 spots (13 up-regulated and 4 down-regulated). Arsenic stress was observed even in an arsenic tolerant plant as P. vittata and a protective effect of AM symbiosis toward arsenic stress was observed.

Modeling and prediction by using WHIM descriptors in QSAR studies: submitochondrial particles (SMP) as toxicity blosensors of chlorophenols

Abstract New 3-dimensional molecular indices (WHIM descriptors) contain information about the whole molecular structure in terms of size, shape, symmetry and atom distribution. These indices are calculated from (x,y,z)-coordinates of a molecule within different weighting schemes in a straightforward manner and represent a very general approach to describe molecules in a unitary conceptual framework. The obtained models confirm the high modeling power of the WHIM descriptors. In this work WHIM descriptors are used for modeling chlorophenols toxicity measured by other not previously considered biosensors. In particular, the attention is stressed on submitochondral particles (SMP) as toxicity biosensors recently proposed and their relationships with other biosensors are further investigated.

Quantitative structure-activity relationships for the toxicity of chlorophenols to mammalian submitochondrial particles

The toxicity of a series of chlorophenols, determined by a short-term in vitro assay utilizing mammalian submitochondrial particles, was related to the physicochemical and structural properties of these compounds. Quantitative Structure-Activity Relationships were defined by correlating EC50 values with six molecular descriptors, chosen to represent lipophilic, electronic and steric effects: the n-octanol/water partition coefficient (log Kow), the constant of Hammett (sigma sigma), the acid dissociation constant (pKa), the first order valence molecular connectivity index (1 chi v), the perimeter of the efficacious section (sigma D) and the melting point (m.p.). The results of regression analysis showed that log Kow is the most successful descriptor, indicating that the ability of chlorophenols to partition into the lipid bilayer of the mitochondrial membrane has an important role in determining their toxic effects. These results are consistent with a molecular mechanism of uncoupling action based on the chemiosmotic theory and on the protonophoric properties of chlorophenols. The quality of the QSAR models confirms the suitability of the SMP assay as a short-term prediction tool for aquatic toxicity of environmental pollutants acting on respiratory functions.

Pollutant Exchange at the Water/Sediment Interface in the Venice Canals

The space-time distribution of some pollutants (Cu, Pb, Zn, Cd, Fe, Mn, V, Ni, Cr) in the sludge of the canals of Venice was studied. The contamination levels were comparable to, or higher, than those measured in the most polluted sediments of the Lagoon of Venice. Sediments were collected by two different sampling techniques: 1) collection of sediment cores (upper 5 cm) by a syringe-type corer; 2) collection by traps, placed on the bottom of the canal. Traps permitted the sampling of sediments essentially resuspended by overlying water turbulence. This sediment fraction is subjected to variations of its physicochemical parameters (principally change of redox conditions) and therefore to pollutant exchange at the water/sediment interface.The metals principally exchanged during sediment resuspension were Cd, Pb, Zn and Cu. These metals have principally an anthropogenic origin and are bound to the most labile geochemical phases of the sediment (such as sulphides), which can be oxidised during sediment resuspension, releasing metals into the water. Fe, Cr and Ni were only partially exchanged, while Mn and V were generally not exchanged; a significant fraction of these metals is of natural origin and is bound to the most refractory phases of the sediment.

A study of the pH dependence of the activity of porcine Cu,Zn superoxide dismutase

Abstract The enzyme activity of porcine Cu,Zn superoxide dismutase, which has an unusually high isoelectric point, decreases almost linearly with increasing pH between pH 7.5 and 12.0, while EPR and NMR parameters of the copper are titrated only above pH 9.5. Elimination of lysine charges by succinylation abolishes the pH dependence of activity between pH 7.5 and 9.5 and produces identical pH-activity curves for both bovine and porcine enzymes. The pH dependence of activity of the succinylated proteins overlaps that of the spectroscopic parameters of the copper in both enzymes. These results indicate that lysines play a critical role in the rate determining step of the mechanism of the Cu,Zn superoxide dismutases.

19F relaxation as a probe of the oxidation state of Cu, Zn superoxide dismutase. Studies of the enzyme in steady-state turnover

Summary 19F nmr relaxation proved to be a proper method to evaluate the Cu2+/Cu+ ratio at the active site of Cu, Zn superoxide dismutase in either equilibrium or turnover conditions. In the steady-state under fluxes of O2−, the enzyme was found to contain 50% Cu2+, in accord with the equal rates of copper catalytic reduction and oxidation. Previous results giving 75% Cu at the steady-state without change of the overall catalytic constant were confirmed for samples subjected to freeze-drying or freezing-thawing.

A rotating disk electrode for kinetic studies of superoxide dismutases: applicability in a wide pH range and for continuous monitoring of enzyme inactivation.

A rotating disk electrode coated with a thin mercury film is described. It is suitable for electrochemical determinations of the catalytic constant of superoxide dismutase in a much wider pH range than that accessible to polarographic methods. In particular this is the only direct method, except for pulse radiolysis, that allows mechanistic studies of the enzyme in the physiological pH range. Furthermore, the continuous response of this electrode allows enzyme activity changes characterized by half-lives in the range from a few to 10(3) s. to be followed.

The symbiosis between Nicotiana tabacum and the endomycorrhizal fungus Funneliformis mosseae increases the plant glutathione level and decreases leaf cadmium and root arsenic contents.

Over time, anthropogenic activities have led to severe cadmium (Cd) and arsenic (As) pollution in several environments. Plants inhabiting metal(loid)-contaminated areas should be able to sequester and detoxify these toxic elements as soon as they enter roots and leaves. We postulated here that an important role in protecting plants from excessive metal(loid) accumulation and toxicity might be played by arbuscular mycorrhizal (AM) fungi. In fact, human exploitation of plant material derived from Cd- and As-polluted environments may lead to a noxious intake of these toxic elements; in particular, a possible source of Cd and As for humans is given by cigarette and cigar smoke. We investigated the role of AM fungus Funneliformis mosseae (T.H. Nicolson & Gerd.) C. Walker & A. Schüßler in protecting Nicotiana tabacum L. (cv. Petit Havana) from the above-mentioned metal(loid) stress. Our findings proved that the AM symbiosis is effective in increasing the plant tissue content of the antioxidant glutathione (GSH), in influencing the amount of metal(loid)-induced chelators as phytochelatins, and in reducing the Cd and As content in leaves and roots of adult tobacco plants. These results might also prove useful in improving the quality of commercial tobacco, thus reducing the risks to human health due to inhalation of toxic elements contained in smoking products.