Showing papers by "University of Catania published in 2005"

Mechanisms of Antibacterial Action of Three Monoterpenes

Abstract: In the present paper, we report the antimicrobial efficacy of three monoterpenes [linalyl acetate, (+)menthol, and thymol] against the gram-positive bacterium Staphylococcus aureus and the gram-negative bacterium Escherichia coli. For a better understanding of their mechanisms of action, the capability of these three monoterpenes to damage biomembranes was evaluated by monitoring the release, following exposure to the compounds under study, of the water-soluble fluorescent marker carboxyfluorescein from unilamellar vesicles with different lipidic compositions (phosphatidylcholine, phosphatidylcholine/phosphatidylserine [9:1], phosphatidylcholine/stearylamine [9:1], and phosphatidylglycerol/cardiolipin [9:1]). Furthermore, the interaction of the terpenes tested with dimyristoylphosphatidylcholine multilamellar vesicles as model membranes was monitored by means of differential scanning calorimetry. Finally, the results were related to the relative lipophilicity and water solubility of the compounds examined. Taken together, our findings lead us to speculate that the antimicrobial effect of (+)menthol, thymol, and linalyl acetate may result, at least partially, from a perturbation of the lipid fraction of microorganism plasma membrane, resulting in alterations of membrane permeability and in leakage of intracellular materials. Besides being related to physicochemical characteristics of the drugs (such as lipophilicity and water solubility), this effect seems to be dependent on lipid composition and net surface charge of microbial membranes. Furthermore, the drugs might cross the cell membranes, penetrating into the interior of the cell and interacting with intracellular sites critical for antibacterial activity.

Modeling cascading failures in the North American power grid

Abstract: The North American power grid is one of the most complex technological networks, and its interconnectivity allows both for long-distance power transmission and for the propagation of disturbances. We model the power grid using its actual topology and plausible assumptions about the load and overload of transmission substations. Our results indicate that the loss of a single substation can result in up to $25\%$ loss of transmission efficiency by triggering an overload cascade in the network. The actual transmission loss depends on the overload tolerance of the network and the connectivity of the failed substation. We systematically study the damage inflicted by the loss of single nodes, and find three universal behaviors, suggesting that $40\%$ of the transmission substations lead to cascading failures when disrupted. While the loss of a single node can inflict substantial damage, subsequent removals have only incremental effects, in agreement with the topological resilience to less than $1\%$ node loss.

In situ measurements of the physical characteristics of Titan's environment

Abstract: On the basis of previous ground-based and fly-by information, we knew that Titan's atmosphere was mainly nitrogen, with some methane, but its temperature and pressure profiles were poorly constrained because of uncertainties in the detailed composition. The extent of atmospheric electricity (‘lightning’) was also hitherto unknown. Here we report the temperature and density profiles, as determined by the Huygens Atmospheric Structure Instrument (HASI), from an altitude of 1,400 km down to the surface. In the upper part of the atmosphere, the temperature and density were both higher than expected. There is a lower ionospheric layer between 140 km and 40 km, with electrical conductivity peaking near 60 km. We may also have seen the signature of lightning. At the surface, the temperature was 93.65 ± 0.25 K, and the pressure was 1,467 ± 1 hPa.

Implicit---Explicit Runge---Kutta Schemes and Applications to Hyperbolic Systems with Relaxation

Abstract: We consider new implicit---explicit (IMEX) Runge---Kutta methods for hyperbolic systems of conservation laws with stiff relaxation terms. The explicit part is treated by a strong-stability-preserving (SSP) scheme, and the implicit part is treated by an L-stable diagonally implicit Runge---Kutta method (DIRK). The schemes proposed are asymptotic preserving (AP) in the zero relaxation limit. High accuracy in space is obtained by Weighted Essentially Non Oscillatory (WENO) reconstruction. After a description of the mathematical properties of the schemes, several applications will be presented

Oxidant stress from nitric oxide synthase-3 uncoupling stimulates cardiac pathologic remodeling from chronic pressure load.

Abstract: Cardiac pressure load stimulates hypertrophy, often leading to chamber dilation and dysfunction. ROS contribute to this process. Here we show that uncoupling of nitric oxide synthase-3 (NOS3) plays a major role in pressure load-induced myocardial ROS and consequent chamber remodeling/hypertrophy. Chronic transverse aortic constriction (TAC; for 3 and 9 weeks) in control mice induced marked cardiac hypertrophy, dilation, and dysfunction. Mice lacking NOS3 displayed modest and concentric hypertrophy to TAC with preserved function. NOS3(-/-) TAC hearts developed less fibrosis, myocyte hypertrophy, and fetal gene re-expression (B-natriuretic peptide and alpha-skeletal actin). ROS, nitrotyrosine, and gelatinase (MMP-2 and MMP-9) zymogen activity markedly increased in control TAC, but not in NOS3(-/-) TAC, hearts. TAC induced NOS3 uncoupling in the heart, reflected by reduced NOS3 dimer and tetrahydrobiopterin (BH4), increased NOS3-dependent generation of ROS, and lowered Ca(2+)-dependent NOS activity. Cotreatment with BH4 prevented NOS3 uncoupling and inhibited ROS, resulting in concentric nondilated hypertrophy. Mice given the antioxidant tetrahydroneopterin as a control did not display changes in TAC response. Thus, pressure overload triggers NOS3 uncoupling as a prominent source of myocardial ROS that contribute to dilatory remodeling and cardiac dysfunction. Reversal of this process by BH4 suggests a potential treatment to ameliorate the pathophysiology of chronic pressure-induced hypertrophy.

Survival and complications in thalassemia.

Abstract: The life expectancy of patients with thalassemia major has significantly increased in recent years, as reported by several groups in different countries. However, complications are still frequent and affect the patients' quality of life. In a recent study from the United Kingdom, it was found that 50% of the patients had died before age 35. At that age, 65% of the patients from an Italian long-term study were still alive. Heart disease is responsible for more than half of the deaths. The prevalence of complications in Italian patients born after 1970 includes heart failure in 7%, hypogonadism in 55%, hypothyroidism in 11%, and diabetes in 6%. Similar data were reported in patients from the United States. In the Italian study, lower ferritin levels were associated with a lower probability of experiencing heart failure and with prolonged survival. Osteoporosis and osteopenia are common and affect virtually all patients. Hepatitis C virus antibodies are present in 85% of multitransfused Italian patients, 23% of patients in the United Kingdom, 35% in the United States, 34% in France, and 21% in India. Hepatocellular carcinoma can complicate the course of hepatitis. A survey of Italian centers has identified 23 such cases in patients with a thalassemia syndrome. In conclusion, rates of survival and complication-free survival continue to improve, due to better treatment strategies. New complications are appearing in long-term survivors. Iron overload of the heart remains the main cause of morbidity and mortality.

Vulnerability and protection of infrastructure networks.

Abstract: Infrastructure systems are a key ingredient of modern society. We discuss a general method to find the critical components of an infrastructure network, i.e., the nodes and the links fundamental to the perfect functioning of the network. Such nodes, and not the most connected ones, are the targets to protect from terrorist attacks. The method, used as an improvement analysis, can also help to better shape a planned expansion of the network.

Annotated list of marine alien species in the Mediterranean with records of the worst invasive species

Abstract: This collaborative effort by many specialists across the Mediterranean presents an updated annotated list of alien marine species in the Mediterranean Sea. Alien species have been grouped into six broad categories namely established, casual, questionable, cryptogenic, excluded and invasive, and presented in lists of major ecofunctional/taxonomic groups. The establishment success within each group is provided while the questionable and excluded records are commented in brief. A total of 963 alien species have been reported from the Mediterranean until December 2005, 218 of which have been classified as excluded (23%) leaving 745 of the recorded species as valid aliens. Of these 385 (52%) are already well established, 262 (35%) are casual records, while 98 species (13%) remain “questionable” records. The species cited in this work belong mostly to zoobenthos and in particular to Mollusca and Crustacea, while Fish and Phytobenthos are the next two groups which prevail among alien biota in the Mediterranean. The available information depends greatly on the taxonomic group examined. Thus, besides the three groups explicitly addressed in the CIESM atlas series (Fish, Decapoda/Crustacea and Mollusca), which are however updated in the present work, Polychaeta, Phytobenthos, Phytoplankton and Zooplankton are also addressed in this study. Among other zoobenthic taxa sufficiently covered in this study are Echinodermata, Sipuncula, Bryozoa and Ascidiacea. On the contrary, taxa such as Foraminifera, Amphipoda and Isopoda, that are not well studied in the Mediterranean, are insufficiently covered. A gap of knowledge is also noticed in Parasites, which, although ubiquitous and pervasive in marine systems, have been relatively unexplored as to their role in marine invasions. Conclusively the lack of funding purely systematic studies in the region has led to underestimation of the number of aliens in the Mediterranean. Emphasis is put on those species that are current or potential threats to the marine ecosystems, namely the Worst Invasive Alien Species providing their record across major groups.

Functional and morphological alterations of mitochondria in pancreatic beta cells from type 2 diabetic patients

Abstract: Little information is available on the insulin release properties of pancreatic islets isolated from type 2 diabetic subjects. Since mitochondria represent the site where important metabolites that regulate insulin secretion are generated, we studied insulin release as well as mitochondrial function and morphology directly in pancreatic islets isolated from type 2 diabetic patients. Islets were prepared by collagenase digestion and density gradient purification, and insulin secretion in response to glucose and arginine was assessed by the batch incubation method. Adenine nucleotides, mitochondrial membrane potential, the expression of UCP-2, complex I and complex V of the respiratory chain, and nitrotyrosine levels were evaluated and correlated with insulin secretion. Compared to control islets, diabetic islets showed reduced insulin secretion in response to glucose, and this defect was associated with lower ATP levels, a lower ATP/ADP ratio and impaired hyperpolarization of the mitochondrial membrane. Increased protein expression of UCP-2, complex I and complex V of the respiratory chain, and a higher level of nitrotyrosine were also found in type 2 diabetic islets. Morphology studies showed that control and diabetic beta cells had a similar number of mitochondria; however, mitochondrial density volume was significantly higher in type 2 diabetic beta cells. In pancreatic beta cells from type 2 diabetic subjects, the impaired secretory response to glucose is associated with a marked alteration of mitochondrial function and morphology. In particular, UCP-2 expression is increased (probably due to a condition of fuel overload), which leads to lower ATP, decreased ATP/ADP ratio, with consequent reduction of insulin release.

Noncommutative gravitational quantum well

Abstract: We study noncommutative geometry at the quantum mechanics level by means of a model where noncommutativity of both configuration and momentum spaces is considered. We analyze how this model affects the problem of the two-dimensional gravitational quantum well and use the latest experimental results for the two lowest energy states of neutrons in the Earth's gravitational field to establish an upper bound on the fundamental momentum scale introduced by noncommutativity, namely, $\sqrt{\ensuremath{\eta}}\ensuremath{\lesssim}1\text{ }\mathrm{meV}/c$, a value that can be improved in the future by up to $3$ orders of magnitude. We show that the configuration space noncommutativity has, in leading order, no effect on the problem. We also analyze some features introduced by the model, especially a correction to the presently accepted value of Planck's constant to $1$ part in ${10}^{24}$.

Ferulic acid ethyl ester protects neurons against amyloid beta- peptide(1-42)-induced oxidative stress and neurotoxicity: relationship to antioxidant activity.

Abstract: Alzheimer's disease (AD) is neuropathologically characterized by depositions of extracellular amyloid and intracellular neurofibrillary tangles, associated with loss of neurons in the brain. Amyloid β-peptide (Aβ) is the major component of senile plaques and is considered to have a causal role in the development and progress of AD. Several lines of evidence suggest that enhanced oxidative stress and inflammation play important roles in the pathogenesis or progression of AD. The present study aimed to investigate the protective effects of ethyl-4-hydroxy-3-methoxycinnamic acid (FAEE), a phenolic compound which shows antioxidant and anti-inflammatory activity, on Aβ(1–42)-induced oxidative stress and neurotoxicity. We hypothesized that the structure of FAEE would facilitate radical scavenging and may induce protective proteins. Aβ(1–42) decreases cell viability, which was correlated with increased free radical formation, protein oxidation (protein carbonyl, 3-nitrotyrosine), lipid peroxidation (4-hydroxy-2-trans-nonenal) and inducible nitric oxide synthase. Pre-treatment of primary hippocampal cultures with FAEE significantly attenuated Aβ(1–42)-induced cytotoxicity, intracellular reactive oxygen species accumulation, protein oxidation, lipid peroxidation and induction of inducible nitric oxide synthase. Treatment of neurons with Aβ(1–42) increases levels of heme oxygenase-1 and heat shock protein 72. Consistent with a cellular stress response to the Aβ(1–42)-induced oxidative stress, FAEE treatment increases the levels of heme oxygenase-1 and heat shock protein 72, which may be regulated by oxidative stresses in a coordinated manner and play a pivotal role in the cytoprotection of neuronal cells against Aβ(1–42)-induced toxicity. These results suggest that FAEE exerts protective effects against Aβ(1–42) toxicity by modulating oxidative stress directly and by inducing protective genes. These findings suggest that FAEE could potentially be of importance for the treatment of AD and other oxidative stress-related diseases.

Efficiency enhancement of permanent-magnet synchronous motor drives by online loss minimization approaches

Abstract: In this paper, a new loss minimization control algorithm for inverter-fed permanent-magnet synchronous motors (PMSMs), which allows for the reduction of the power losses of the electric drive without penalty on its dynamic performance, is analyzed, experimentally realized, and validated. In particular, after a brief recounting of two loss minimization control strategies, namely, the "search control" and the "loss-model control," both a new modified dynamic model of the PMSM (which takes into account the iron losses) and an innovative "loss-model" control strategy are presented. Experimental tests on a specific PMSM drive employing the proposed loss minimization algorithm have been performed, aiming to validate the actual implementation. The main results of these tests confirm that the dynamic performance of the drive is maintained, and in small motors enhancement up to 3.5% of the efficiency can be reached in comparison with the PMSM drive equipped with a more traditional control strategy.

Cubosome dispersions as delivery systems for percutaneous administration of indomethacin

Abstract: The present study concerns the production and characterization of monooleine (MO) dispersions as drug delivery systems for indomethacin, taken as model anti-inflammatory drug. Dispersions were produced by emulsification and homogenization of MO and poloxamer in water. Morphology and dimensional distribution of the disperse phase have been characterized by cryo-transmission electron microscopy and photon correlation spectroscopy, respectively. X-ray diffraction has been performed to determine the structural organization of the disperse phase. Sedimentation field flow fractionation (SdFFF) has been performed to investigate drug distribution in the dispersion. An in vitro diffusion study was conducted by Franz cell associated to stratum corneum epidermis membrane on cubosome dispersions viscosized by carbomer. In vivo studies based on skin reflectance spectrophotometry and tape stripping were performed to better investigate the performance of cubosome as indomethacin delivery system. Microscopy studies showed the coexistence of vesicles and cubosomes. X-ray diffraction revealed the presence of a bicontinuous cubic phase of spatial symmetry Im3m (Q229). SdFFF demonstrated that no free drug was present in the dispersion. Indomethacin incorporated in viscosized MO dispersions exhibited a lower flux with respect to the analogous formulation containing the free drug in the aqueous phase and to the control formulation based on carbomer gel. Reflectance spectroscopy demonstrated that indomethacin incorporated into MO dispersions can be released in a prolonged fashion. Tape-stripping experiments corroborated this finding. MO dispersions can be proposed as nanoparticulate systems able to control the percutaneous absorption of indomethacin.

Androgens up-regulate the insulin-like growth factor-I receptor in prostate cancer cells.

Abstract: In this study, we show that androgens up-regulate insulin-like growth factor-I receptor (IGF-IR) expression and sensitize prostate cancer cells to the biological effects of IGF-I. Both dihydrotestosterone and the synthetic androgen R1881 induced an approximately 6-fold increase in IGF-IR expression in androgen receptor (AR)-positive prostate cancer cells LNCaP. In accordance with IGF-IR up-regulation, treatment with the nonmetabolizable androgen R1881 sensitized LNCaP cells to the mitogenic and motogenic effects of IGF-I, whereas an IGF-IR blocking antibody effectively inhibited these effects. By contrast, these androgens did not affect IGF-IR expression in AR-negative prostate cancer cells PC-3. Reintroduction of AR into PC-3 cells by stable transfection restored the androgen effect on IGF-IR up-regulation. R1881-induced IGF-IR up-regulation was partially inhibited by the AR antagonist Casodex (bicalutamide). Two other AR antagonists, cyproterone acetate and OH-flutamide, were much less effective. Androgen-induced IGF-IR up-regulation was not dependent on AR genomic activity, because two AR mutants, AR-C619Y and AR-C574R, devoid of DNA binding activity and transcriptional activity were still able to elicit IGF-IR up-regulation in HEK293 kidney cells in response to androgens. Moreover, androgen-induced IGF-IR up-regulation involves the activation of the Src-extracellular signal-regulated kinase pathway, because it was inhibited by both the Src inhibitor PP2 and the MEK-1 inhibitor PD98059. The present observations strongly suggest that AR activation may stimulate prostate cancer progression through the altered IGF-IR expression and IGF action. Anti-androgen therapy may be only partially effective, or almost ineffective, in blocking important biological effects of androgens, such as activation of the IGF system.

Quantum Many Particle Systems in Ring-Shaped Optical Lattices

Abstract: In the present work we demonstrate how to realize a 1D closed optical lattice experimentally, including a tunable boundary phase twist. The latter may induce ''persistent currents,'' visible by studying the atoms' momentum distribution. We show how important phenomena in 1D physics can be studied by physical realization of systems of trapped atoms in ring-shaped optical lattices. A mixture of bosonic and/or fermionic atoms can be loaded into the lattice, realizing a generic quantum system of many interacting particles.

Vector opinion dynamics in a bounded confidence consensus model

Abstract: We study the continuum opinion dynamics of the compromise model of Krause and Hegselmann for a community of mutually interacting agents by solving numerically a rate equation. The opinions are here represented by two-dimensional vectors with real-valued components. We study the situation starting from a uniform probability distribution for the opinion configuration and for different shapes of the confidence range. In all cases, we find that the thresholds for consensus and cluster merging either coincide with their one-dimensional counterparts, or are very close to them. The symmetry of the final opinion configuration, when more clusters survive, is determined by the shape of the opinion space. If the latter is a square, which is the case we consider, the clusters in general occupy the sites of a square lattice, although we sometimes observe interesting deviations from this general pattern, especially near the center of the opinion space.

Decision Rule Approach

Abstract: In this chapter we present the methodology of Multiple-Criteria Decision Aiding (MCDA) based on preference modelling in terms of “if…, then …” decision rules. The basic assumption of the decision rule approach is that the decision maker (DM) accepts to give preference information in terms of examples of decisions and looks for simple rules justifying her decisions. An important advantage of this approach is the possibility of handling inconsistencies in the preference information, resulting from hesitations of the DM. The proposed methodology is based on the elementary, natural and rational principle of dominance. It says that if action x is at least as good as action y on each criterion from a considered family, then x is also comprehensively at least as good as y. The set of decision rules constituting the preference model is induced from the preference information using a knowledge discovery technique properly adapted in order to handle the dominance principle. The mathematical basis of the decision rule approach to MCDA is the Dominance-based Rough Set Approach (DRSA) developed by the authors. We present some basic applications of this approach, starting from multiple-criteria classification problems, and then going through decision under uncertainty, hierarchical decision making, classification problems with partially missing information, problems with imprecise information modelled by fuzzy sets, until multiple-criteria choice and ranking problems, and some classical problems of operations research. All these applications are illustrated by didactic examples whose aim is to show in an easy way how DRSA can be used in various contexts of MCDA.

Effects of Blood Orange Juice Intake on Antioxidant Bioavailability and on Different Markers Related to Oxidative Stress

Abstract: Orange juice is a source of antioxidants that might afford in vivo protection from oxidative stress. To test this hypothesis, we carried out a human intervention study with blood orange juice containing high amounts of vitamin C, anthocyanins, and carotenoids. Sixteen healthy female volunteers were enrolled in a crossover study and were given 600 mL/day of blood orange juice or a diet without juice for 21 days. Before and after each intervention period, plasma vitamin C, cyanidin-3-glucoside, and carotenoids were quantified. Furthermore, plasma antioxidant capacity, malondialdehyde concentration in plasma, 11-dehydrotromboxane B2 urinary excretion, and lymphocyte DNA damage were evaluated as biomarkers of oxidative stress. Blood orange juice consumption determined a significant increase in plasma vitamin C, cyanidin-3-glucoside, β-cryptoxanthin, and zeaxanthin. Also, lymphocyte DNA resistance to oxidative stress was improved whereas no effect was observed on the other markers that we analyzed. In turn, th...

Brain atrophy and lesion load in a large population of patients with multiple sclerosis

Abstract: Objective: To measure white matter (WM) and gray matter (GM) atrophy and lesion load in a large population of patients with multiple sclerosis (MS) using a fully automated, operator-independent, multiparametric segmentation method. Methods: The study population consisted of 597 patients with MS and 104 control subjects. The MRI parameters were abnormal WM fraction (AWM-f), global WM-f (gWM-f), and GM fraction (GM-f). Results: Significant differences between patients with MS and control subjects included higher AWM-f and reduced gWM-f and GM-f. MRI data showed significant differences between patients with relapsing-remitting and secondary progressive forms of MS. Significant correlations between MRI parameters and between MRI and clinical data were found. Conclusions: Patients with multiple sclerosis have significant atrophy of both white matter (WM) and gray matter (GM); secondary progressive patients have significantly more atrophy of both WM and GM than do relapsing-remitting patients and a significantly higher lesion load (abnormal WM fraction); lesion load is related to both WM and even more to GM atrophy; lesion load and WM and GM atrophy are significantly related to Expanded Disability Status Scale score and age at onset (suggesting that the younger the age at disease onset, the worse the lesion load and brain atrophy); and GM atrophy is the most significant MRI variable in determining the final disability.

Acetylcarnitine induces heme oxygenase in rat astrocytes and protects against oxidative stress: Involvement of the transcription factor Nrf2

Abstract: Efficient functioning of maintenance and repair processes seem to be crucial for both survival and physical quality of life. This is accomplished by a complex network of the so-called longevity assurance processes, under control of several genes termed vitagenes. These include members of the heat shock protein system, and there is now evidence that the heat shock response contributes to establishing a cytoprotective state in a wide variety of human conditions, including inflammation, neurodegenerative disorders, and aging. Among the various heat shock proteins, heme oxygenase-1 has received considerable attention; it has been recently demonstrated that heme oxygenase-1 induction, by generating the vasoactive molecule carbon monoxide and the potent antioxidant bilirubin, could represent a protective system potentially active against brain oxidative injury. Acetyl-L-carnitine is proposed as a therapeutic agent for several neurodegenerative disorders. Accordingly, we report here that treatment of astrocytes with acetyl-L-carnitine induces heme oxygenase-1 in a dose- and time-dependent manner and that this effect was associated with up-regulation of heat shock protein 60 as well as high expression of the redox-sensitive transcription factor Nrf2 in the nuclear fraction of treated cells. In addition, we show that addition of acetyl-L-carnitine to astrocytes, prior to proinflammatory lipopolysaccharide- and interferon-γ-induced nitrosative stress, prevents changes in mitochondrial respiratory chain complex activity, protein nitrosation and antioxidant status induced by inflammatory cytokine insult. Given the broad cytoprotective properties of the heat shock response, molecules inducing this defense mechanism appear to be possible candidates for novel cytoprotective strategies. Particularly, manipulation of endogenous cellular defense mechanisms via acetyl-L-carnitine may represent an innovative approach to therapeutic intervention in diseases causing tissue damage, such as neurodegeneration. We hypothesize that maintenance or recovery of the activity of vitagenes may delay the aging process and decrease the risk of age-related diseases. © 2005 Wiley-Liss, Inc.