702 research outputs found
Sort by
Structure-function relationships in the oligopeptide transporter PepT1.
No full textThe proton-dependent di- and tripeptide transporter PepT1 represents the major route of dietary amino acid intake in the intestine of many species. This transporter belongs to the solute carrier family SLC15 and because of its electrogenic properties it may be studied both through electrophysiological and radiotracer uptake experiments.
In this work some functional and structural aspects of PepT1 have been investigated at the molecular level. In addition to the physiological relevance, understanding of the details of its mechanisms of operation is important since PepT1 appears to be involved in the absorption of many important, orally administered, drugs such as antibiotics, angiotensin-converting inhibitors, and antiviral agents.
The electrophisyiological and biophysical properties of PepT1 expressed in Xenopus oocytes were investigated with two-electrode voltage-clamp.
Most of the above functional observations were derived from uptake data, in absence of control of the membrane voltage, or from electrophysiological measurement of steady transport currents, in the presence of a dipeptide substrate. Important additional informations regarding the transport mechanism may arise from measurement of presteady-state currents, the electrophysiological signals that can be observed in absence of organic substrate, and that represent the first steps in the transport cycle. A unified kinetic model for PepT1 has been devised that can describe the different characteristics of the isoforms of different species, with respect to both presteady-state and transport-associated currents.
Mutational studies have provided significant evidence for the functional role of some residues in PepT1. Particularly Arg282 and Asp341, in the transmembrane domain 7 and 8 of the transporter, have been reported to form a charge pair that may break and reform during the transport cycle. The attention has been focused on these two oppositely charged aminoacids to better understand their functional role in the absorption pathway.
Finally, the functional and structural basis of reverse operation of wild-type and mutated forms of PepT1 have been studied. Mutants in the putative charge pair residues Arg282 and Asp341 of rabbit PepT1 have been shown exhibit properties useful to better understand the possibility of reverse transport. This reversed mode of operation may be either the effect or the cause of abnormal or pathological conditions
New microbial hydroxysteroid dehydrogenases and their synthetic application for the selective modification of bile acids.
No full textHydroxysteroid dehydrogenases (HSDHs), mainly obtained from bacterial sources, have been widely employed for the regio- and stereoselective oxidoreduction of the hydroxyl-keto groups of steroids, bile acids and their derivatives. In particular they might be suitable biocatalysts for the industrial synthesis of bile acids derivatives of pharmacological interest such as ursodeoxycholic acid (UDCA; 3α,7β-dihydroxy-5β-cholan-24-oic acid).
Aim of this work was i) to investigate a new enzymatic process for the synthesis of UDCA; ii) to develop new cofactor regeneration systems to be coupled to HSDHs-catalyzed reactions; iii) to clone and overexpress in E. coli new HSDHs suitable for the modification of bile acids up to an industrial level.
Specifically, the preparative-scale HSDHs-catalyzed one-pot enzymatic synthesis of 12-ketoursodeoxycholic acid (3,7-dihydroxy-12-oxo-5-cholanoic acid), a key intermediate for the synthesis of ursodeoxycholic acid, from cholic acid has been investigated. This goal has been achieved by alternating oxidative and reductive steps in a one-pot system and employing HSDHs with different cofactor specificity. To provide the necessary driving force to opposite reactions (i.e., oxidation and reduction) acting concurrently on different sites of the same substrate molecule, suitable cofactor regeneration systems were coupled to these reactions. However, due to a limited cofactor specificity of some of the enzymes used, an undesired reaction equilibrium was established resulting in by-products formation. This problem was overcome by uncoupling the oxidative and reductive biocatalysts (Paper I).
Moreover, a new laccase/mediator system for NAD(P)+ cofactor regeneration in HSDHs-catalyzed oxidations has been developed. This system has been successfully applied in aqueous, buffered reactions (space-time yield of 2.35 g L-1 h-1 ) and in biphasic systems (space-time yields of up to 27.47 g L-1 h-1), demonstrating to be very efficient, to have high stability, to tolerate solvents, and to be simple to employ (Paper II).
Finally, NADPH-dependent 7α- and 7β-hydroxysteroid dehydrogenases (7α-HSDH and 7β-HSDH) from Clostridium absonum were cloned and overexpressed in recombinant form in E. coli. The enzymes were further characterized from a functional and a kinetic point of view, demonstrating that both of them, in suitable bioconversion conditions, could be promising candidates for further applications in the epimerization reaction of bile acids at the C-7 position (Paper III)
Towards a trustworthness model for Open Source software.
No full textTrustworthiness is one of the main aspects that contribute to the adoption/rejection of a software product. This is actually true for any product in general, but it is especially true for Open Source Software (OSS), whose trustworthiness is sometimes still regarded as not as guaranteed as that of closed source products. Only recently, several industrial software organizations have started investigating the potential of OSS products as users or even producers. As they are now getting more and more involved in the OSS world, these software organizations are clearly interested in ways to assess the trustworthiness of OSS products, so as to choose OSS products that are adequate for their goals and needs.
Trustworthiness is a major issue when people and organizations are faced with the selection and the adoption of new software. Although some ad-hoc methods have been proposed, there is not yet general agreement about which software characteristics contribute to trustworthiness. Such methods –like the OpenBQR [30] and other similar approaches [58][59]– assess the trustworthiness of a software product by means of a weighted sum of specific quality evaluations. None of the existing methods based on weighted sums has been widely adopted. In fact, these methods are limited in that they typically leave the user with two hard problems, which are common to models built by means of weighted sums: identify the factors that should be taken into account, and assign to each of these factors the “correct” weight to adequately quantify its relative importance.
Therefore, this work focuses on defining an adequate notion of trustworthiness of Open Source products and artifacts and identifying a number of factors that influence it to help and guide both developers and users when deciding whether a given program (or library or other piece of software) is “good enough” and can be trusted in order to be used in an industrial or professional context.
The result of this work is a set of estimation models for the perceived trustworthiness of OSS.
This work has been carried out in the context of the IST project QualiPSo (http://www.qualipso.eu/), funded by the EU in the 6th FP (IST-034763).
The first step focuses on defining an adequate notion of trustworthiness of software products and artifacts and identifying a number of factors that influence it.
The definition of the trustworthiness factors is driven by specific business goals for each organization. So, we carried out a survey to elicit these goals and factors directly from industrial players, trying to derive the factors from the real user needs instead of deriving them from our own personal beliefs and/or only by reading the available literature.
The questions in the questionnaire were mainly classified in three different categories:
1) Organization, project, and role. 2) Actual problems, actual trustworthiness evaluation processes, and factors. 3) Wishes. These questions are needed to understand what information should be available but is not, and what indicators should be provided for an OSS product to help its adoption.
To test the applicability of the trustworthiness factors identified by means of the questionnaires, we selected a set of OSS projects, widely adopted and generally considered trustable, to be used as references. Afterwards, a first quick analysis was carried out, to check which factors were readily available on each project’s web site.
The idea was to emulate the search for information carried out by a potential user, who browses the project’s web sites, but is not willing to spend too much effort and time in carrying out a complete analysis.
By analyzing the results of this investigation, we discovered that most of the trustworthiness factors are not generally available with information that is enough to make an objective assessment, although some factors have been ranked as very important by the respondents of our survey. To fill this gap, we defined a set of different proxy-measures to use whenever a factor cannot be directly assessed on the basis of readily available information. Moreover, some factors are not measurable if developers do not explicitly provide essential information. For instance, this happens for all factors that refer to countable data (e.g., the number of downloads cannot be evaluated in a reliable way if the development community does not publish it).
Then, by taking into account the trustworthiness factors and the experience gained through the project analysis, we defined a Goal/Question/Metric (GQM[29]) model for trustworthiness, to identify the qualities and metrics that determine the perception of trustworthiness by users.
In order to measure the metrics identified in the GQM model, we identified a set of tools. When possible, tools were obtained by adapting, extending, and integrating existing tools. Considering that most of metrics were not available via the selected tools, we developed MacXim, a static code analysis tool.
The selected tools integrate a number of OSS tools that support the creation of a measurement plan, starting from the main actors’ and stakeholders’ objectives and goals (developer community, user community, business needs, specific users, etc.), down to the specific static and dynamic metrics that will need to be collected to fulfill the goals.
To validate the GQM model and build quantitative models of perceived trustworthiness and reliability, we collected both subjective evaluations and objective measures on a sample of 22 Java and 22 C/C++ OSS products.
Objective measures were collected by means of MacXim and the other identified tools while subjective evaluations were collected by means of more than 500 questionnaires.
Specifically, the subjective evaluations concerned how users evaluate the trustworthiness, reliability and other qualities of OSS; objective measures concerned software attributes like size, complexity, modularity, and cohesion.
Finally, we correlated the objective code measures to users’ and developers’ evaluations of OSS products.
The result is a set of quantitative models that account for the dependence of the perceivable qualities of OSS on objectively observable qualities of the code. Unlike the models based on weighted sums usually available in the literature, we have obtained estimation models [87], so the relevant factors and their specific weights are identified via statistical analysis, and not in a somewhat more subjective way, as usually happens.
Qualitatively, our results may not be totally surprising. For instance, it may be generally expected that bigger and more complex products are less trustworthy than smaller and simpler products; likewise, it is expected that well modularized products are more reliable.
For instance, our analyses indicate that the OSS products are most likely to be trustworthy if:
• Their size is not greater than 100,000 effective LOC;
• The number of java packages is lower than 228.
These models derived in our work can be used by end-users and developers that would like to evaluate the level of trustworthiness and reliability of existing OSS products and components they would like to use or reuse, based on measurable OSS code characteristics. These models can also be used by the developers of OSS products themselves, when setting code quality targets based on the level of trustworthiness and reliability they want to achieve. So, the information obtained via our models can be used as an additional piece of information that can be used when making informed
decisions.
Thus, unlike several discussions that are based on –sometimes interested– opinions about the quality of OSS, this study aims at deriving statistically significant models that are based on repeatable measures and user evaluations provided by a reasonably large sample of OSS users.
The detailed results are reported in the next sections as follows:
•Chapter 1 reports the introduction to this work
•Chapter 2 reports the related literature review
•Chapter 3 reports the identified trustworthiness factors
•Chapter 4 describe how we built the trustworthiness model
•Chapter 5 shows the tools we developed for this activity
•Chapter 6 reports on the experimentation phase
•Chapter 7 shows the results of the experimentation
•Chapter 8 draws conclusions and highlights future works
•Chapter 9 lists the publication made during the Ph
Prevalenza della sintomatologia neuropsichiatrica e suo trattamento farmacologico in una popolazione di anziani istituzionalizzati attraverso l’uso della Neuropsychiatric Inventory-Nursing Home version (NPI-NH).
No full textmissin
Ruolo dei polimorfismi del CYP450 1A2 negli eventi avversi da clozapina: uno studio osservazionale.
No full textObjectives: The genetically polymorphic enzyme cytochrome P450 (CYP) 1A2
contributes to the biotransformation of the antipsychotic drug clozapine (CLO). Two
polymorphisms are known to affect significantly 1A2 activity: 1A2*1F which increase
metabolism and 1A2*1C which decrease it. These SNPs, located in the promoter region
of the gene, may be responsible of a different CYP1A2 mRNA expression and could
help to explain interindividual differences in enzyme activity. Aim of these research
was to evaluate the impact of these polymorphisms on CLO pharmacokinetics and on
the occurrence of adverse reactions (ADRs).
Methods: All enrolled subjects were patients treated with CLO in our department
during the period 2008-2009. Inclusion criteria for case-group were: diagnosis of
psychotic disorder, normal liver and renal function, absence of concomitant diseases,
occurrence of significant CLO-induced ADRs. Patients who assumed CYP1A2 inducer
or inhibitory drugs, except smoking, were excluded. We considered significant CLOinduced
ADRs all reactions which led to CLO discontinuation or a permanent dose
reduction, and were related to CLO according to the clinical evaluation of the clinicians
confirmed by a “certain” or “probable” result at WHO-Uppsala criteria (WHO Uppsala
Monitoring Centre-UMC: http://www.who-umc.org). In the control-group we enrolled
patients treated for at least 1 year with CLO without showing ADRs, with the same
clinical features, matched for age, sex, CLO doses and smoking habits. Clinical
parameters were correlated with the CYP1A2 genotype and allelic combinations and
with CYP1A2 mRNA expression levels.
Results: The ratings for side effects, like sedation, constipation, scialorrea, were
significantly higher in CYP1A2 poor metabolizers genotypes.
Conclusions: Treatment with clozapine could be dangerous in extremely slow
metabolizers and ineffective in extremely rapid. Although genotyping explained only a
fraction of the adverse events, it could be a good predictor of adverse events
Web content mining with multi-source machine learning for intelligent web agents.
No full textThe web is recognized as the largest data source in the world. The nature of such data is characterized by partial or no structure, and even worse there exist no standard data schema for the even low-volumed structured data. Web Mining aims to extract useful knowledge from the Web by using a variety of techniques that have to cope with the heterogeneity and lack of a unique and fixed way of representing information.
An important aspect in Web Mining is played by the automation of extraction rules with proper algorithms. Machine Learning techniques have been successfully applied toWeb Mining and Information Extraction tasks thanks to the generalization and adaptation capabilities that are a key requirement on general content, heterogeneous web pages.
The World Wide Web is a graph, more precisely a directed labeled graph where the nodes are represented by the pages and the edges are represented by links between them. Recent works propose the exploitation of the web structure (Link Analysis) for content extraction, for example one can leverage the content category of neighbor pages to categorize the contents of difficult web pages where word-frequency-based techniques are not robust enough.
In this thesis we propose an automated method suitable for a wide range of domains based on Machine Learning and Link Analysis. In particular we propose an inductive model able to recognize content pages where structured information is located after being trained with proper input data. In order to keep the recognition speed high enough for real-world applications an additional algorithm is proposed which lets the approach to boost both in speed and quality. The proposed method has been tested with controlled dataset in a classic train-and-test scenario and in a real-world web crawling system
Funzione e ruolo nel sistema penale del processo per reati sessuali: luci e ombre dopo la legge n. 38/2009.
No full textmissin
Valutazione epidemiologica e terapeutica dei traumi toraco-addominali.
No full textThe Varese's Circolo Hospital is qualified as a second level Emergency and Admittance Department (DEA), that is a structure able to face any traumatic lesions round the clock.
A 118 operations Center is lovated inside this structure.
Trauma assistance management should be guaranteed by the application of shared protocols and by the synergy between the above mentioned structures.
There are no current data about major thoraco-abdominal traumas incidence in the catchment area of Varese.
The aim of the study is the epidemiological evaluation and the knowledge of surgical therapeutic course of patients with traumatic thoraco-abdominal lesions.
One hundred sixty-seven patients with major thoracic and thoraco-abdominal traumas, admitted into Varese Hospital between January 2007 and August 2009, were included in the study
