1,721,124 research outputs found
Animali e ambiente
No full text- L'organismo vivente può essere definito da un punto di vista termodinamico come un sistema aperto, ossia un sistema che scambia materia ed energia con l'ambiente esterno. L'ambiente esterno di un organismo rappresenta non solo lo spazio fisico in cui l'organismo si trova a vivere, ma viene definito dall'insieme delle "condizioni" e delle "risorse" con cui l'organismo si relaziona nello spazio e nel tempo e senza le quali esso, in quanto sistema termodinamico aperto, non può esistere.
In generale, l'ambiente esterno di un organismo si caratterizza per la variabilità delle sue componenti sia nello spazio che nel tempo.
- Gli organismi animali reagiscono ai cambiamenti ambientali con una molteplicità di risposte, utilizzando meccanismi che operano a diversi livelli di organizzazione biologica, da quello biochimico e molecolare a quello fisiologico e comportamentale. Queste risposte possono manifestarsi su scale temporali differenti: da una scala temporale di minuti o ore, a scale temporali di giorni o mesi fino a scale temporali evolutive.
- Quando un animale si confronta con la variazione di un determinato fattore ambientale nell’immediato può conformare il proprio ambiente interno alla variazione ambientale oppure mantenere il proprio ambiente interno costante nonostante il variare della condizione esterna. Gli organismi che si conformano alle variazioni di un dato fattore ambientale vanno incontro a variazioni dell’ambiente interno simili ai cambiamenti presenti all’esterno. Gli animali regolatori, invece, utilizzano i meccanismi propri dell'omeostasi per mantenere costanti le caratteristiche fisico-chimiche dell’ambiente interno nonostante le fluttuazioni dell’ambiente esterno.
- La regolazione assicura una certa indipendenza dell’organismo nei confronti del variare delle condizioni ambientali esterne, in quanto le condizioni fisico-chimiche dell’ambiente interno vengono mantenute costanti a livelli ottimali per lo svolgimento delle funzioni dell’organismo.
- Un animale che nel suo ambiente di vita sia esposto per periodi relativamente lunghi a variazioni di alcune condizioni ambientali, può manifestare, su una scala temporale di giorni, settimane o mesi, cambiamenti in alcuni aspetti della propria fisiologia, morfologia o del comportamento che favoriscono la sopravvivenza dell'organismo nelle nuove condizioni. Gli effetti di tali modifiche possono protrarsi per mesi o per anni, o addirittura per tutta la vita dell’organismo, ma non implicano cambiamenti nel genoma dell’individuo stesso e, quindi, non vengono trasmessi alle generazioni successive. Essi sono espressione della plasticità del fenotipo dell'organismo
- Il termine "adattamento" viene riferito al processo dell'evoluzione per selezione naturale, ossia al processo attraverso il quale la selezione naturale nell'ambito di una popolazione in un particolare ambiente modifica la frequenza di geni codificanti per caratteri che massimizzano la sopravvivenza e la riproduzione degli individui (ossia massimizzano la fitness della popolazione). Il risultato di questo processo è per gli organismi la condizione di essere "adattati" ad un determinato ambiente, per cui il termine "adattamento" viene utilizzato anche per indicare i caratteri evoluti dalla specie per selezione naturale, che ciascun individuo eredita geneticamente dai genitori e che gli conferiscono la capacità di vivere e riprodursi in un determinato ambiente. Gli "adattamenti" possono, pertanto, essere intesi come risposte evolutive a condizioni ambientali nuove o variate, derivate da molte generazioni di selezione naturale.
- La taglia corporea influenza notevolmente la relazione struttura-funzione negli organismi animali ed anche le loro relazioni con l'ambiente esterno.
Molte variabili fisiologiche variano con la massa corporea secondo equazioni allometriche aventi la formula generale:
Y = a Mb
dove Y rappresenta la variabile fisiologica considerata, M è una misura della taglia dell'organismo considerato, generalmente espressa attraverso la misura della sua massa corporea, a e b sono costanti. Il valore di b fornisce informazioni su come la variabile fisiologica di interesse cambi in funzione della taglia corporea
Metallotioneins as indicators of trace metal pollution
No full textMetallothioneins (MTs) are low-molecular-weight cystein-rich metal-binding proteins that are involved in detoxification and homeostasis of heavy metals. The ubiquitous distribution of MTs in virtually all types of organisms studied to date attests to the conserved nature of MTs and their function. The biological function of MTs is likely related to the physiologically relevant metals that these proteins bind. In mammals, MT is found to bind zinc and copper under normal physiological conditions.Both zinc and copper are trace metals that are essential for life. Recent studies have produced strong evidence to support the idea that MT functions as a metal chaperone for the regulation of gene expression and for synthesis and functional activity of proteins, such as metalloproteins and metal-dependent transcription factors. MT could thus serve as a reservoir of essential metals. MTs are inducible proteins. Exposure of the organisms to high levels of heavy metals (e.g. Zn, Cu, Cd, and Hg) and the following increase of heavy metal cations in the cells stimulates metalloprotein neosynthesis. The importance of metallothionein (MT) in toxicologic responses to heavy metals was early recognized for potential application as “biomarker” of organism exposure to heavy metals in aquatic environments
Cl-absorption in European eel intestine and its regulation.
No full textThe intestinal epithelium of the euryhaline teleost fish, Anguilla anguilla, absorbs Cl-transepithelially. This gives rise to a negative transepithelial potential at the basolateral side of the epithelium and to a measured short circuit current. Cl- absorption occurs via bumetanide-sensitive Na+-K+-2Cl- cotransport, localized on the luminal membrane. The cotransport operates in parallel with a luminal K+ conductance that recycles the ion into the lumen. Cl- leaves the cell across the basolateral membrane by way of Cl- conductance and presumably via a KCl cotransport. The driving force for this process is provided by the electrochemical sodium gradient across the plasma membrane, generated and maintained by the basolateral Na+-K+-ATPase. The resulting NaCl absorption process is active and enables marine fish to take up water, thereby compensating for water that was lost passively from the body. Fresh water acclimatized eel also absorb Cl- actively, although in smaller quantities, utilizing the same ion transport mechanisms as marine eels. This mechanism is basically the same as the model proposed for the thick ascending limb (cTAL).
Cl- absorption is regulated by a number of cellular factors, such as HCO3-, pH, Ca2+, cyclic nucleotides, and cytoskeletal elements. It is sensitive to osmotic stress, and therefore is a good physiological model to study ion transport mechanisms that are activated when osmotic stress induces cell volume regulation. The activation of these various ion transport pathways is dependent on cellular transduction mechanisms in which phosphorylation events (mainly by PKC and MLCK for the hypertonic response) and cytoskeletal elements, either microfilaments or microtubules, seem to play key roles
Na+-K+-2Cl- activation and the osmotic stress response in a model salt transport epithelium
No full textEpithelia are physiologically exposed to osmotic stress resulting in alteration of cell volume in several aspects of their functioning; therefore the activation of “emergency” systems of rapid cell volume regulation is fundamental in their physiology.
In the present study the physiological response to osmotic stress was investigated in a salt transporting epithelium, the intestine of the euryhaline teleost Anguilla anguilla.
This epithelium, when symmetrically bathed with normal Ringer solution, develops a net Cl- current (giving rise to a negative transepithelial potential, Vte), based on the operation of the luminal absorptive Na+-K+-2Cl- cotransporter in parallel with a luminal K+ conductance and in series with a basolateral Cl- conductance.
The eel intestine, because it is physiologically exposed to changes in extracellular osmolarity, constitutes a good model of cellular volume regulation, permitting the study of ion transport activation that occurs in cells or tissues in response to osmotic stress. Tissue responses were studied by using freshly isolated epithelial cell sheets with intact tight junctions.
As determined by morphometrical analysis of epithelium height, the eel intestinal epithelium is able to perform either RVI response following hypertonic shrinkage or RVD response following hypotonic swelling.
RVI response is sustained by the increased activity of the luminal absorptive Na+-K+-2Cl- cotransporter, detectable as a bumetanide-sensitive increase in the basal Isc and Vte. Changes in the cotransporter activity are not involved in the RVD response, since the cotransporter remains still active after hypotonic swelling.
The hypertonic shrinkage activation of the luminal absorptive cotransporter is Ca2+-calmodulin dependent, requires the integrity of cytoskeleton, both microfilaments and microtubules, and it is also dependent on the activity of protein kinase C (PKC) and myosin light chain kinase (MLCK). Therefore, the hypertonicity induced activation of the absorptive Na+-K+-2Cl- cotrasporter is dependent on cellular transduction mechanisms involving an interaction between the cytoskeleton and phosphorylation events
Biomarker application in “sentinel” organisms for the study of chemical contamination risk along Salento (Apulia coasts)
No full textStudio di biomarkers in mitili (Mytilus galloprovincialis) traslocati in Mar Piccolo e in Mar Grande di Taranto
No full textBiomarkers of chemical contamination were measured in M. galloprovincialis sampled in Mar Piccolo of Taranto in order to evaluate the potential ecotoxicological risk in this area exposed to industrial and urban impact. The analysis of a new potential biomarker, the enzymatic activity of carbonic anhydrase, was included in the biomarkers battery utilized and results obtained suggest its applicability in a multimarker approach
Seasonal variation of biomarkers in Mytilus galloprovincialis sampled inside and outside Mar Piccolo of Taranto (Italy).
No full textThe aim of this work was to study spatial and temporal variation in biomarkers in autochthonous Mytilus
galloprovincialis sampled inside and outside Mar Piccolo of Taranto, a typical polluted semi-enclosed
basin of the Mediterranean Sea characterised by scarce hydrodynamism. Mar Piccolo of Taranto represents
a site of Italian National Interest because of the high level of pollution. A battery of biomarkers
(lysosomal destabilisation, catalase, metallothioneins, acetylcholinesterase, air survival) was applied to
assess pollution-induced stress effects in authoctonous mussels. The responses were analysed comparatively
in two different seasons, summer and winter, in order to assess possible changes in the
pollutant-induced stress syndrome throughout the year. No significant difference inside and outside Mar
Piccolo was observed for metallothioneins. By contrast, the dramatically decreased acetylcholinesterase
values and strongly increased catalase activity in organisms taken from Mar Piccolo in winter indicate
an increased risk of exposure to anticholinesterase compounds during this season. The results suggest
the importance of temporal variability in biomarker responses throughout the year for monitoring possible
seasonal changes in the pollutant-induced stress syndrome of organisms living in a certain environment
and, in turn, more properly detecting changes in ecotoxicological risks
Metodo per la valutazione enzimatica della tossicità di matrici acquose ambientali
No full textL’invenzione consiste in un metodo innovativo per la misura del grado di tossicità di matrici acquose ambientali in modo rapido, semplice, a basso costo e senza l’utilizzo di organismi vivi. Il principio sul quale esso si basa consiste nella misura in vitro dell’inibizione dell’attività enzimatica di anidrasi carbonica quando questo enzima sia posto a contatto con matrici acquose ambientali (quali acque interstiziali, acque reflue, percolati, ecc) contenenti sostanze tossiche. L’entità della inibizione enzimatica risulta essere proporzionale al grado di tossicità del campione.
Tale metodo è, pertanto, facilmente applicabile ad operazioni di screening di tossicità ambientale
Morphometrical alteration of coelomocytes in the earthworm Lumbricus terrestris.
No full textEarthworms are very important organisms for soil formation and organic matter breakdown in most terrestrial environment. They are key species responsible for moving large amounts of soil from deeper horizons to the surface layers in many ecosystems. These organisms ingest large amounts of. organic matter, and are continuously exposed to contaminants trough their body. Because of their strong interaction with soil, earthworm populations are profoundly affected by soil pollution. In recent years the use of earthworms biological responses (i.e. biomarker) to chemical pollutants has known a growing interest for polluted soil risk assessment.
The aim of the present work was the in field validation of a multimarker approach on the bioindicator organism Lumbricus terrestris, a large reddish worm native to Europe. Several biomarkers, either specific or general biomarker, either of exposure or of effect, were determined: metallothionein levels, acetylcholinesterase activity, lysosomal membrane stability, coelomocyte morphometric alterations, micronuclei formation. Animals were sampled in four agricultural soil in the Salento Peninsula (ITALY), characterized by different anthropogenic impacts. In parallel the chemical analysis of heavy metals and aromatic polycyclic hydrocarbons were performed in the soil from the four sites.
Obtained results demonstrated the sensitivity of the Lumbricus terrestris biochemical and cellular responses to bioavailable pollutants present in the soil. Moreover, results clearly showed the applicability of the earthworm multrimarker approach in environmental quality monitoring and assessment of the soil
Pollutant-induced alterations of granulocyte morphology in the earthworm Eisenia foetida
No full textEarthworms are considered convenient indicators of land use and soil fertility. Recently the use of
biomarkers in earthworms has been increasingly investigated. The aim of this work was to study
possible pollutant-induced morphometric alterations in Eisenia foetida granulocytes in view of future
applications as a sensitive, simple, and quick biomarker for soil monitoring and assessment
applications. Results showed consistent enlargement of earthworm granulocytes induced by exposure
to either copper sulfate or methiocarb. The increase of cellular size was time-dependent and was about
100% after 14 days of exposure for both treatments. In order to verify the applicability of morphometric
granulocyte alteration, a battery of standardized biomarkers such as lysosomal membrane stability,
metallothionein induction, or acetylcholinesterase (AChE) inhibition were also determined. We
recommend the use of morphometric alterations of granulocytes as a suitable biomarker of pollutant
effect to be included in a multibiomarker strategy including responses at different levels of biological
organization
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