1,720,963 research outputs found
Studio sulle potenzialità di bioaccumulo di metalli tossici da parte di molluschi bivalvi in ambiente lagunare
No full textNell'ambito degli studi rivolti all'approfondimento dei meccanismi che regolano l'accumulo di metalli all'interno dei tessuti di Molluschi Bivalvi caratteristici degli ecosistemi lagunari si è voluto approfondire l’aspetto legato all'incorporazione di questi elementi all'interno delle conchiglie. Il lavoro di ricerca è stato condotto considerando la composizione elementale delle valve (1) di diverse specie prelevate nello stesso luogo, (2) di un’unica specie prelevata in diversi siti di campionamento, (3) per un'unica specie in riferimento alla composizione nei tessuti molli e nell'ambiente, (4) in una matrice (lo scarto da venericoltura) composta dall'insieme di conchiglie di specie differenti proveniente da diversi punti di campionamento.
Il design sperimentale è risultato funzionale all'ottenimento di risultati significativi che hanno permesso di chiarire i fattori ambientali e biologici che regolano il processo di bioaccumulo nelle conchiglie, le diversità esistenti tra i meccanismi che operano a livello dei tessuti molli e delle conchiglie dei Bivalvi, l’esistenza di una “impronta” riconoscibile, in termini di tipologia e quantità di elementi presenti nelle conchiglie di organismi della stessa specie cresciuti in ambienti diversi e, con una quota ancora maggiore, nello scarto da venericoltura, dove a questa impronta si somma la particolarità data dalla tipologia di specie dotate di esoscheletro che contribuiscono alla sua differenziazione.
Le conoscenze acquisite, il coinvolgimento degli attori coinvolti nel territorio e l’approfondimento bibliografico hanno portato a individuare un possibile utilizzo del materiale di scarto da venericoltura che risponde alle esigenze e problematiche emerse nel territorio e valorizza contemporaneamente le proprietà caratterizzanti il materiale conchigliare. L’ultima fase del lavoro è stata perciò dedicata allo studio dell’efficacia e la fattibilità dell’utilizzo dello scarto da venericoltura per la costruzione di opere di consolidamento e difesa idraulica delle strutture morfologiche in laguna di Venezia
Heavy metal bioaccumulation trends in the shell of two Bivalve species: a comparative study.
No full textBivalves are extensively used in biomonitoring programmes because they’re known to be efficient accumulators of contaminants and ideal indicators organisms. Various species have been used for assess toxic metals levels in marine environment but the most favourite ones are filter feeding Bivalves such as mussels and oysters. In most cases the laboratory experiments are conducted to evaluate the metals concentration levels in soft tissues: few works concentrate their attention also in shell levels. In the optic of a more exhaustive comprehension of the mechanisms that undergo the transfer of inorganic contaminants to organism’s hard parts, it was decided to operate a comparison between two different bivalve species on their ability to accumulate a specific toxic metal. The tests were carried out with standard size organisms in strictly controlled experimental condition in order to assess the extent at which the physiological characteristics of the species affect the metal equilibrium in the organism. The metal concentrations in both shell and soft tissues are analytically determined and subsequently compared to highlight intraspecific correlations and develop a possible explanation of metal partitioning. In addiction it was determined the different species responses to bioaccumulation tests to achieve an indication about their ability in accumulate the selected toxic metal in the shell. This skill could be used in future applications concerning the comprehension and the following exploitation of Bivalves role in water basin self-purification mechanisms
Estimation of experimental conditions to maximize mussels shell capability in trace metals accumulation.
No full textThe evaluation of mussels shell capability of concentrate heavy metals was performed by means of a set of laboratory experiments conducted with mussels collected in unpolluted sites exposed to sub-lethal concentrations of a known toxic metal. Multiple cycles of accumulation and depuration were carried out all along the experimental period; the constant monitoring of experimental conditions and periodical metal determination in shell and tissue samples allowed the individuation of the accumulation and depuration patterns in both Bivalves materials in the selected species. Alternative exposure to contaminated and clean seawater respectively was performed in order to record the different metal concentration trends in shell and soft tissues. In fact it is demonstrated that once the metal is incorporate in the crystalline calcium carbonate lattice, his loss from the shell during mussels lifetime can be considered of no concern; in the other hand it is known that soft tissues are able to release contaminants in response to changed environmental conditions. The aim was to establish a set of experimental conditions able to optimize metal accumulation in mussel hard parts and to calculate the specific MATC (Maximum Acceptable Toxic Concentration) value. So it was possible to settle physical, chemical and physiological parameters in order to maximize the shell metal content and set the basis for implementation of bioinertization strategies exploiting mussels metabolic activity and detoxification mechanisms
Antioxidant action of two polyphenols, resveratrol and piceid, on a biological model in vitro.
No full textAmong natural antioxidants found in many natural foods and beverages, the flavonoid resveratrol and piceid have been proven to be effective against a broad range of diseases whose origin can be attributed to oxidative damage. Resveratrol is a phytoalexin, a secondary metabolite synthesized by Spermatophytes in response to stress conditions caused, for example, by exposure to UV radiation or fungal infection. Piceid, called also polidatina, is the glucosylated form of resveratrol, and, as its parental compound, also shows two isomers cis and trans; it is more resistant to enzymatic oxidation of resveratrol, enters the cell through an active transport mechanism that uses the glucose transporters, and, because of its higher solubility in water, is more efficiently absorbed from the mammal’s intestine. This work was planning to evaluate the antioxidant action of these polyphenols on a biological model in vitro and to assess, then, any protective action of these stilbenes when the same organelle are exposed to toxic environmental substances known to give rise to a state of oxidative stress. The choice of using a mitochondria-based bioassay was determined by the need to clarify the biochemical mechanisms underlying the antioxidant effect of resveratrol and piceid on natural membranes. In particular, starting from some studies conducted to date on model membranes (i.e. synthetic organelles like micelles or liposomes), we tried to investigate resveratrol and piceid antioxidant action performed at mitochondrial membranes, using frozen beef heart mitochondria. Initially, they has been utilized with the classical mitochondrial endpoint, i.e. respiratory chain inhibition. Then, because it is reported that the antioxidant activity of polyphenols is linked to their ability to block or slow down the lipid peroxidation, reacting with peroxy radicals formed in the propagation phase, we investigated the ability of resveratrol and piceid to interact with initiator radicals, since the possibility exists that oxidation is inhibited at the stage of initiation. Indeed, the action of resveratrol and piceid as a scavenger against radical initiators and propagators of membrane oxidation, and its effectiveness in preventing the lipid peroxidation in different types of substrates, is well known
Bioinertization strategy by Bivalves: A new challenging technique also for CO2 balance.
No full textAreas such as mangroves, salt marshes and seagrasses are known to be responsible for capturing and storing up to some 70 % of the carbon permanently stored in the marine system. The so called “Blue carbon” is thus emerging as another option for controlling climate change because of marine systems ability to sequester vast amounts of carbon dioxide and consequently to act as a carbon sink. In this optic it is important to better understand coastal ecosystem functioning and to quantify the contribution of the singular components in order to improve this ability. We focused our attention on a seagrass, i.e. the Venice Lagoon coastal transition environment, and we tried to estimates the importance of the role of living organisms in capturing atmospheric carbon dioxide and transform it in a storable form. First we considered the autotrophic component and its capacity to fix CO2 as organic matter photosyntheticaly; then, we tried to follow the flow of this carbon in the food web and in particular towards skeletal molluscan organisms.
On the other side it’s known that the crystalline calcium carbonate lattice is able to incorporate metals. This is the reason why Bivalves are extensively used in biomonitoring programmes being efficient accumulators of contaminants and ideal bioindicators. Various species have been used for assess toxic metals levels in marine environment but the most favourite ones are filter feeding Bivalves such as mussels and oysters. This skill could be used in future applications concerning the comprehension and the following exploitation of Bivalves role in water basin self-purification mechanisms.
The comprehension of the relevance of these mechanisms enable us to imagine a new challenging frontier: the exploitation of molluscan commercial production as a mean for carbon sequestration and pollutants bioinertization
Improvement on frozen mitochondria bioassay: a methodological remark.
Full text linkThe protocol for the bioassay with the mitochondria of beef heart frozen at -22 °C, (developed by Iero, Manente, Bragadin and Perin, in Chemosphere, 52, 2003) requires that the reaction cell is thermostatically controlled at 25 °C. This value was chosen because it is used as a reference for the state environmental standard (Standard Ambient Temperature and Pressure, SATP).
The choice is not, therefore, been supported by assessments on the effectiveness of the test at this temperature, but was dictated by the practice of reporting results to a standard temperature value.
Finally, it was decided to make a comparison between the working temperature of 25 °C and the 37 °C one, chosen as close to cattle body temperature (estimated to be 38.6 °C), then "normal" working temperature for mitochondria extracted from heart
Bivalve shells reuse and recovery: bio-inertisation and engineering applications.
No full textThe disposal of waste material constituted by shells resulting from processing subsequent to Bivalve Molluscs harvesting for sale purpose constitutes a big problem for the Venice Lagoon ecosystem from the environmental point of view both because of the large volumes involved and its specific characteristics. In some areas this material, which is currently discarded at sea, comes up to cover the lagoon bed with a thick layer that prevents the benthic communities natural development.
A previous work highlighted that as shells are bio-minerals constituting the exoskeleton of organisms known for their ability to accumulate pollutants, they are able to block these pollutants in the crystal structure of the valve thus acting as bio-inerting tools. So we assessed the possibility of a differing shell waste management studying the opportunity to use it in the construction of protective barriers for hydraulic consolidation such as gabions. This would offer the double advantage, on one hand, to provide a sustainable solution to the shell waste disposal problem, with the aim of an integrated closed-loop (the material produced in the lagoon of Venice will be reused in the same place), and, secondly, to remove inert material that contains pollutants that would, in this way, subtracted from the system.
After the product implementation we evaluated the evolution of its biological and mechanical characteristics with the aim of highlighting its stability, strength and effectiveness, as well as the opportunity to extend the use of this technology in all erosion risk areas located in the Venice Lagoon and, in general, throughout the Northern Adriatic
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Waste from clam harvesting: a resource for environmental engineering in the Venice lagoon.
No full textClams harvesting has been widespread in the Venice lagoon since Ruditapes philippinarum introduction in 1983. Operations involved in this kind of activity include a sieving phase: operators pick out clams of commercial interest by using manual or mechanical tools. During this phase they obtain a waste that is usually discarded in lagoon.
The Institution responsible of fisheries resources supervision in the Venice lagoon highlighted a management problem related to this kind of waste, that is mostly composed by shells, wood, sediment and different kind of inert materials: in the long term it can accumulate in specific areas covering the seabed and leading to an ecological quality decrease and, consequently, to a lower productivity.
So it is necessary to define a strategy in order to collect this material and to avoid the need for its disposal: we took into account the possibility to use it as a filler, in total or partial replacement of the material currently used, for manufactured devices such as gabions and submerged barriers to be used for banks protection and consolidation in the Venice lagoon as well as for beaches protection from erosion.
In order to do this, we worked in two directions: on the one hand we evaluated the scientific and technical devices feasibility and on the other hand we considered logistical and organisational aspects related to the project. For this reason we related to stakeholders and to local Authorities to better comprehend their issues, and find possible solutions and policies: in particular we were able to define quantities involved, collection, transport and storage strategies, operative problems related to different phases.
This effort made possible the definition of a more effective solution: we were able to integrate ecological and technical issues with logistical and social aspects in order to define a holistic management strategy
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