169,894 research outputs found
Confronto tra modelli di approccio in diagnostica e terapia comportamentale
No full textLo studio dei problemi comportamentali richiede un metodo di classificazione che sia funzionale, sia per formulare diagnosi univoche che per proporre terapie idonee. Vengono presi in esame principalmente i metodi di classificazione della scuola americana e di quella francese. La prima, con un approccio tipicamente funzionale, considera “anormali” quei comportamenti che
siano “inappropriati e fuori dal contesto”, la seconda definisce come “patologia”, la “perdita delle funzioni di adattabilità dell’organismo all’ambiente e l’incapacità di ripristinare un equilibro con esso”.Studies about behavioural disorders needs a classification method to formulate diagnosis and to suggest treatment. In this article the American and French school approach to behavioural disorders were examined. The first one, using a functional classification, consider “not normal” all the behaviours “inappropriate and out of contest”, the second one consider as a “pathology” the “lost of adaptability functions to the environment and the inability to restore a balance with it”
Problematiche di diagnostica in medicina comportamentale comparata: evoluzione e comportamento
No full textCapire la natura dei problemi comportamentali è fondamentale per sviluppare una base razionale per il loro trattamento. Dal punto di vista etologico i problemi comportamentali possono essere definiti come comportamenti adattativi ma sconvenienti per il proprietario, tentativi di agire in modo adattativo in situazioni non ottimali, comportamenti non adattativi. Solo un’analisi etologica è in grado di svelare il valore funzionale di problemi quali lo spruzzare urina del gatto o l’aggressività da dominanza nel cane.Understanding the nature of behaviour problems is essential to developing a rational basis for their treatment. With an ethological point of view, behavioural problems may be divided into behaviour which are adaptive but inconvenient for the owner, attempts to behave in an adaptive way in a subotptimal environment, and those which are truly maladaptive
Cytochrome c in a Dry Trehalose Matrix: Structural and Dynamical Effects Probed by X-Ray Absorption Spectroscopy
No full textAbstractWe report on the structure and dynamics of the Fe ligand cluster of reduced horse heart cytochrome c in solution, in a dried polyvinyl alcohol (PVA) film, and in two trehalose matrices characterized by different contents of residual water. The effect of the solvent/matrix environment was studied at room temperature using Fe K-edge x-ray absorption fine structure (XAFS) spectroscopy. XAFS data were analyzed by combining ab initio simulations and multi-parameter fitting in an attempt to disentangle structural from disorder parameters. Essentially the same structural and disorder parameters account adequately for the XAFS spectra measured in solution, both in the absence and in the presence of glycerol, and in the PVA film, showing that this polymer interacts weakly with the embedded protein. Instead, incorporation in trehalose leads to severe structural changes, more prominent in the more dried matrix, consisting of 1), an increase up to 0.2Å of the distance between Fe and the imidazole N atom of the coordinating histidine residue and 2), an elongation up to 0.16Å of the distance between Fe and the fourth-shell C atoms of the heme pyrrolic units. These structural distortions are accompanied by a substantial decrease of the relative mean-square displacements of the first ligands. In the extensively dried trehalose matrix, extremely low values of the Debye Waller factors are obtained for the pyrrolic and for the imidazole N atoms. This finding is interpreted as reflecting a drastic hindering in the relative motions of the Fe ligand cluster atoms and an impressive decrease in the static disorder of the local Fe structure. It appears, therefore, that the dried trehalose matrix dramatically perturbs the energy landscape of cyrochrome c, giving rise, at the level of local structure, to well-resolved structural distortions and restricting the ensemble of accessible conformational substates
Probing the local structure and dynamics of Fe site in cytochrome c embedded in a dry trehalose matrix: An x-ray absorption spectroscopy study
No full textTrehalose, a non-reducing disaccharide of glucose, has a peculiar efficacy in the preservation of
isolated proteins, membranes and tissues (1). A number of experimental techniques, sensitive to
atomic motions, and molecular dynamics simulations (MD) have shown that, in heme proteins
embedded in trehalose matrices, the large-scale internal motions, which in glycerol-water start
above ~ 180 K, are strongly inhibited. Such inhibition increases when the water content is
decreased. Furthermore, FTIR spectroscopy and MD results enabled to infer the existence of water
molecules at the protein interface involved in hydrogen bond networks, which anchor the protein to
the surrounding water-trehalose matrix and couple the internal degrees of freedom of the protein to
those of the external water-sugar matrix (2 and references therein).
This tight dynamical and structural coupling has been investigated in samples of reduced horse
heart cytochrome (cyt) c, in water glycerol solution and embedded in a trehalose matrix, which was
led to extreme drought, but still contained traces of residual water. We performed Fe K-edge X-ray
absorption spectroscopy measurements at liquid nitrogen and at room temperature. Since the
EXAFS function is damped by an exponential term, which contains the mean square relative
displacement, information on thermal fluctuations and static disorder can be obtained. Our
measurements evidenced that, while lowering the temperature from 300 K to 77 K does not
significatively alter the EXAFS signal both in the water-glycerol solution and in the trehalose-water
matrix, large differences are observed between the spectra in the two different environments. In
particular the damping of the EXAFS function is dramatically decreased in the trehalose-water
matrix as compared to the water-glycerol mixture. This indicates that the trehalose-water matrix
drastically alters the protein energy landscape, most likely hindering the protein internal dynamics
and promoting only some conformational substates at the level of local structure
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
The local structure of Zn binding sites in the bovine cytochrome c oxidase: An X-ray Absorption Spectroscopy study
No full textCytochrome c oxidase (COX) is the terminal component of the respiratory chain: it catalyses
the oxidation of cytochrome c reduced by the cytochrome bc1 complex, reducing O2 to H2O and
pumping protons across the mitochondrial membrane. Definition of the proton transfer pathways is
an open question, crucial for understanding the catalytic mechanism of the enzyme (1).
Zn2+ inhibits bovine heart COX (2). The observation that Zn2+ inhibits proton uptake in the
bacterial cytochrome c oxidase led to propose that Zn2+ binds near the H+ entry point of the Dpathway
where a cluster of histidine residues and carboxylates is found (3).
An endogenous Zn ion has been found in the bovine heart COX where it binds to a
structurally well defined site (4) . To characterize the site at which exogenous Zn binds, inhibiting
proton uptake, we performed Zn K-edge X-ray Absorption Spectroscopy (XAS) measurements on
three samples of bovine COX characterized respectively by 1, 1.5 and 2 zinc atoms per complex.
The last two samples were obtained by incubating the protein with a proper amount of ZnSO4.
Metal stoichiometries were measured by ICP-emission spectroscopy.
In agreement with X-ray diffraction data (4), XAS analysis of the endogenous zinc site shows
that Zn binds four sulphur atoms. The average Zn-S distance is slightly bigger (2.33 Å) than that
reported in the crystallographic model (2.25 Å). On the basis of the XAS spectrum of the
endogenous Zn, we extracted the XAS signal of the inhibitory Zn binding site(s). The difference
spectra obtained from samples characterized by 1.5 and 2.0 Zn per complex exhibited very similar
features. This indicates the presence of a unique, high affinity zinc binding site. First shell analysis
of the XAS signal for the exogenous Zn site suggests three nitrogen atoms at 1.99 Å and one O at
1.98 Å as ligands. A complete, multiple-shell, multiple scattering analysis is in progress to possibly
localize a cluster of residues consistent with the XAS local structure
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