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Search Results: 1 - 10 of 11206 matches for " Mario Coluzzi "
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The challenges of doing more against malaria, particularly in Africa
Touré Yeya Tiémoko,Coluzzi Mario
Bulletin of the World Health Organization , 2000,
Analysis of apyrase 5' upstream region validates improved Anopheles gambiae transformation technique
Fabrizio Lombardo, Gareth J Lycett, Alessandra Lanfrancotti, Mario Coluzzi, Bruno Arcà
BMC Research Notes , 2009, DOI: 10.1186/1756-0500-2-24
Abstract: We have analyzed the upstream regulatory sequence of the An. gambiae salivary gland-specific apyrase (AgApy) gene in transgenic An. gambiae using a piggyBac transposable element vector marked by a 3xP3 promoter:DsRed gene fusion. Efficient germ-line transformation in An. gambiae mosquitoes was obtained and several integration events in at least three different G0 families were detected. LacZ reporter gene expression was analyzed in three transgenic lines/groups, and in only one group was tissue-specific expression restricted to salivary glands.Our data describe an efficient genetic transformation of An. gambiae embryos. However, expression from the selected region of the AgApy promoter is weak and position effects may mask tissue- and stage- specific activity in transgenic mosquitoes.The mosquito Anopheles gambiae is the main vector of the human malaria parasite Plasmodium falciparum in sub-Saharan Africa. Within the insect, the parasite undergoes a complex life-cycle that includes fertilization, midgut invasion, sporozoite maturation, avoidance of the mosquito innate immune response and, as prerequisite for a successful transmission, recognition and entrance into the salivary glands [1]. The development of tools for mosquito genetic manipulation have provided evidence that Plasmodium development can be modified in the anopheline vector and opened new perspectives for studies on vector biology and on parasite-vector-host interactions [2,3].Several studies in the last decade reported the successful use of tissue-specific promoters for directing the expression of exogenous genes in different mosquito target organs (primarily midgut, hemocoel and salivary glands), mainly in the yellow fever vector Aedes aegypti and in the Asian malaria vector Anopheles stephensi [4-7]. As far as the main African malaria vector An. gambiae is concerned, after the initial successful transformation [8] only one additional study with transgenic An. gambiae has been reported so far [9]. In
Distribution of human CYP2C8*2 allele in three different African populations
Giacomo M Paganotti, Silvia Gramolelli, Francesca Tabacchi, Gianluca Russo, David Modiano, Mario Coluzzi, Rita Romano
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-125
Abstract: A total of 503 young subjects were genotyped for the single nucleotide polymorphism rs11572103 (A/T). Eighty-eight were from southern Senegal, 262 from eastern Uganda and 153 from southern Madagascar. The PCR-RFLP technique was used to discriminate the wild-type (A) from the defective allele (T).A CYP2C8*2 (T) allele frequency of 0.222 ± 0.044 was detected in Senegal, 0.105 ± 0.019 in Uganda and 0.150 ± 0.029 in Madagascar.This study demonstrated that CYP2C8*2 allele is widespread in Africa. This allele occurs at different frequency in West and East Africa, being higher in Senegal than in Uganda and Madagascar. These data indicate that an important fraction of the populations analysed has a decreased enzymatic activity, thus being at higher risk for drug accumulation with two possible consequences: i) an exacerbation of drug-associated adverse side effects; ii) an increase of drug-resistance selection pressure on P. falciparum parasites.Plasmodium falciparum malaria is one of the most important infectious diseases in the developing world, representing a priority in public health mainly in sub-Saharan Africa. Nowadays, anti-malarial strategies include: the development of a vaccine, the vector control, as well as drug treatment, which remains the most effective remedy to clear the infection. However, the spread of anti-malarial drug-resistance affects the outcome of treatments [1], since P. falciparum has selected resistant strains for the majority of the molecules used in anti-malarial therapy [2]. As recently demonstrated, host genetic variation in drug metabolizing enzymes influences the selection of P. falciparum drug-resistance in Burkina Faso [3]. In particular, the cytochrome P450 2 C8 (CYP2C8), a polymorphic enzyme that mainly contributes to the hepatic metabolism of amodiaquine (AQ) and chloroquine (CQ), shows a genetic variant (CYP2C8*2) that is associated with higher rate of drug-resistant parasites in the infected host (pfcrt-76Y and pfmdr1-86Y P. falcipar
Numerical simulations on the 4d Heisenberg spin glass
B. Coluzzi
Physics , 1994, DOI: 10.1088/0305-4470/28/3/027
Abstract: We study the 4d Heisenberg spin glass model with Gaussian nearest-neighbor interactions. We use finite size scaling to analyze the data. We find a behavior consistent with a finite temperature spin glass transition. Our estimates for the critical exponents agree with the results from epsilon-expansion.
Numerical study on a disordered model for DNA denaturation transition
Barbara Coluzzi
Physics , 2005, DOI: 10.1103/PhysRevE.73.011911
Abstract: We study numerically a disordered version of the model for DNA denaturation transition (DSAW-DNA) consisting of two interacting SAWs in 3d, which undergoes a first order transition in the homogeneous case. The two possible values eAT and eGC of the interactions between base pairs are taken as quenched random variables distributed with equal probability along the chain. We measure quantities averaged over disorder such as the energy density, the specific heat and the probability distribution of the loop lengths. When applying the scaling laws used in the homogeneous case we find that the transition seems to be smoother in presence of disorder, in agreement with general theoretical arguments. Nevertheless we can not rule out the possibility of a still first order transition.
Numerical evidence for relevance of disorder in a Poland-Scheraga DNA denaturation model with self-avoidance: Scaling behavior of average quantities
Barbara Coluzzi,Edouard Yeramian
Physics , 2006, DOI: 10.1140/epjb/e2007-00140-5
Abstract: We study numerically the effect of sequence heterogeneity on the thermodynamic properties of a Poland-Scheraga model for DNA denaturation taking into account self-avoidance, i.e. with exponent c_p=2.15 for the loop length probability distribution. In complement to previous on-lattice Monte Carlo like studies, we consider here off-lattice numerical calculations for large sequence lengths, relying on efficient algorithmic methods. We investigate finite size effects with the definition of an appropriate intrinsic length scale x, depending on the parameters of the model. Based on the occurrence of large enough rare regions, for a given sequence length N, this study provides a qualitative picture for the finite size behavior, suggesting that the effect of disorder could be sensed only with sequence lengths diverging exponentially with x. We further look in detail at average quantities for the particular case x=1.3, ensuring through this parameter choice the correspondence between the off-lattice and the on-lattice studies. Taken together, the various results can be cast in a coherent picture with a crossover between a nearly pure system like behavior for small sizes N < 1000, as observed in the on-lattice simulations, and the apparent asymptotic behavior indicative of disorder relevance, with an (average) correlation length exponent \nu_r >= 2/d (=2).
Numerical study of the SK Model in magnetic field
Alain Billoire,Barbara Coluzzi
Physics , 2003, DOI: 10.1103/PhysRevE.68.026131
Abstract: We study numerically the Sherrington--Kirkpatrick model as function of the magnetic field h, with fixed temperature T=0.6 Tc. We investigate the finite size scaling behavior of several quantities, such as the spin glass susceptibility, looking for numerical evidences of the transition on the De Almeida Thouless line. We find strong corrections to scaling which make difficult to locate the transition point. This shows, in a simple case, the extreme difficulties of spin glass simulations in non-zero magnetic field. Next, we study various sum rules (consequences of stochastic stability) involving overlaps between three and four replicas, which appear to be numerically well satisfied, and in a non-trivial way. Finally, we present data on P(q) for a large lattice size (N=3200) at low temperature T=0.4 Tc, where, for the first time, the shape predicted by the RSB solution of the model for non-zero magnetic field is visible.
On the Approach to the Equilibrium and the Equilibrium Properties of a Glass-Forming Model
Barbara Coluzzi,Giorgio Parisi
Physics , 1997, DOI: 10.1088/0305-4470/31/19/004
Abstract: In this note we apply some theoretical predictions that arise in the mean field framework for a large class of infinite range models to structural glasses and we present a first comparison of these predictions with numerical results.
The liquid-glass transition of silica
B. Coluzzi,P. Verrocchio
Physics , 2001, DOI: 10.1063/1.1447905
Abstract: We studied the liquid-glass transition of $SiO_2$ by means of replica theory, utilizing an effective pair potential which was proved to reproduce a few experimental features of silica. We found a finite critical temperature $T_0$, where the system undergoes a phase transition related to replica symmetry breaking, in a region where experiments do not show any transition. The possible sources of this discrepancy are discussed.
Magnetic field chaos in the SK Model
Alain Billoire,Barbara Coluzzi
Physics , 2002, DOI: 10.1103/PhysRevE.67.036108
Abstract: We study the Sherrington--Kirkpatrick model, both above and below the De Almeida Thouless line, by using a modified version of the Parallel Tempering algorithm in which the system is allowed to move between different values of the magnetic field h. The behavior of the probability distribution of the overlap between two replicas at different values of the magnetic field h_0 and h_1 gives clear evidence for the presence of magnetic field chaos already for moderate system sizes, in contrast to the case of temperature chaos, which is not visible on system sizes that can currently be thermalized.
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