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Search Results: 1 - 10 of 462048 matches for " A Meda "
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Chronic hypertension alters the expression of Cx43 in cardiovascular muscle cells
Haefliger, J.-A.;Meda, P.;
Brazilian Journal of Medical and Biological Research , 2000, DOI: 10.1590/S0100-879X2000000400009
Abstract: connexin43 (cx43), the predominant gap junction protein of muscle cells in vessels and heart, is involved in the control of cell-to-cell communication and is thought to modulate the contractility of the vascular wall and the electrical coupling of cardiac myocytes. we have investigated the effects of arterial hypertension on the expression of cx43 in aorta and heart in three different models of experimental hypertension. rats were made hypertensive either by clipping one renal artery (two kidney, one-clip renal (2k,1c) model) by administration of deoxycorticosterone and salt (doca-salt model) or by inhibiting nitric oxide synthase with ng-nitro-l-arginine methyl ester (l-name model). after 4 weeks, rats of the three models showed a similar increase in intra-arterial mean blood pressure and in the thickness of the walls of both aorta and heart. analysis of heart mrna demonstrated no change in cx43 expression in the three models compared to their respective controls. the same 2k,1c and doca-salt hypertensive animals expressed twice more cx43 in aorta, and the 2k,1c rats showed an increase in arterial distensibility. in contrast, the aortae of l-name hypertensive rats were characterized by a 50% decrease in cx43 and the carotid arteries did not show increased distensibility. western blot analysis indicated that cx43 was more phosphorylated in the aortae of 2k,1c rats than in those of l-name or control rats, indicating a differential regulation of aortic cx43 in different models of hypertension. the data suggest that localized mechanical forces induced by hypertension affect cx43 expression and that the cell-to-cell communication mediated by cx43 channels may contribute to regulating the elasticity of the vascular wall.
Chronic hypertension alters the expression of Cx43 in cardiovascular muscle cells
Haefliger J.-A.,Meda P.
Brazilian Journal of Medical and Biological Research , 2000,
Abstract: Connexin43 (Cx43), the predominant gap junction protein of muscle cells in vessels and heart, is involved in the control of cell-to-cell communication and is thought to modulate the contractility of the vascular wall and the electrical coupling of cardiac myocytes. We have investigated the effects of arterial hypertension on the expression of Cx43 in aorta and heart in three different models of experimental hypertension. Rats were made hypertensive either by clipping one renal artery (two kidney, one-clip renal (2K,1C) model) by administration of deoxycorticosterone and salt (DOCA-salt model) or by inhibiting nitric oxide synthase with NG-nitro-L-arginine methyl ester (L-NAME model). After 4 weeks, rats of the three models showed a similar increase in intra-arterial mean blood pressure and in the thickness of the walls of both aorta and heart. Analysis of heart mRNA demonstrated no change in Cx43 expression in the three models compared to their respective controls. The same 2K,1C and DOCA-salt hypertensive animals expressed twice more Cx43 in aorta, and the 2K,1C rats showed an increase in arterial distensibility. In contrast, the aortae of L-NAME hypertensive rats were characterized by a 50% decrease in Cx43 and the carotid arteries did not show increased distensibility. Western blot analysis indicated that Cx43 was more phosphorylated in the aortae of 2K,1C rats than in those of L-NAME or control rats, indicating a differential regulation of aortic Cx43 in different models of hypertension. The data suggest that localized mechanical forces induced by hypertension affect Cx43 expression and that the cell-to-cell communication mediated by Cx43 channels may contribute to regulating the elasticity of the vascular wall.
Comparison of spaces of Hardy type for the Ornstein-Uhlenbeck operator
A. Carbonaro,G. Mauceri,S. Meda
Mathematics , 2009,
Abstract: Denote by g the Gauss measure on R^n and by L the Ornstein-Uhlenbeck operator. In this paper we introduce a local Hardy space h^1(g) of Goldberg type and we compare it with the Hardy space H^1(g) introduced in a previous paper by Mauceri and Meda. We show that for each each positive r the imaginary powers of the operator rI+L are unbounded from h^1(g) to L^1(g). This result is in sharp contrast both with the fact that the imaginary powers are bounded from $H^1(g}$ to L^1(g), and with the fact that for the Euclidean laplacian \Delta and the Lebesgue measure \lambda) the imaginary powers of rI-\Delta are bounded from the Goldberg space h^1(\lambda) to L^1(\lambda). We consider also the case of Riemannian manifolds M with Riemannian measure m. We prove that, under certain geometric assumptions on M, an operator T, bounded on L^2(m), and with a kernel satisfying certain analytic assumptions, is bounded from H^1(m) to L^1(m) if and only if it is bounded from h^1(m) to L^1(m). Here H^1(m) denotes the Hardy space on locally doubling metric measure spaces introduced by the authors in arXiv:0808.0146, and h^1(m) is a Goldberg type Hardy space on M, equivalent to a space recently introduced by M. Taylor. The case of translation invariant operators on homogeneous trees is also considered.
H^1 and BMO for certain locally doubling metric measure spaces of finite measure
A. Carbonaro,G. Mauceri,S. Meda
Mathematics , 2008,
Abstract: In a previous paper the authors developed a H^1-BMO theory for unbounded metric measure spaces $(M,\rho,m)$ of infinite measure that are locally doubling and satisfy two geometric properties, called "approximate midpoint" property and "isoperimetric" property. In this paper we develop a similar theory for spaces of finite measure. We prove that all the results that hold in the infinite measure case have their counterparts in the finite measure case. Finally, we show that the theory applies to a class of unbounded, complete Riemannian manifolds of finite measure and to a class of metric measure spaces of the form (R^n,\rho_\phi, m_\phi), where dm_\phi=e^{-\phi} dx and \rho_\phi$ is the Riemannian metric corresponding to the length element ds^2=(1+ |grad\phi|)^2(dx_1^2+...+dx_n^2)$. This generalizes previous work of the last two authors for the Gauss space.
Applications of Mogulskii, and Kurtz-Feng Large Deviation Results to Risk Reserve Processes with Aggregate Claims  [PDF]
Jorge Garcia, Ana Meda
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.312A291
Abstract: In this paper we examine the large deviations principle (LDP) for sequences of classic Cramér-Lundberg risk processes under suitable time and scale modifications, and also for a wide class of claim distributions including (the non-super- exponential) exponential claims. We prove two large deviations principles: first, we obtain the LDP for risk processes on D[0,1] with the Skorohod topology. In this case, we provide an explicit form for the rate function, in which the safety loading condition appears naturally. The second theorem allows us to obtain the LDP for Aggregate Claims processes on D[0,) with a different time-scale modification. As an application of the first result we estimate the ruin probability, and for the second result we work explicit calculations for the case of exponential claims.
In vitro Antioxidant, Xanthine Oxidase and Acetylcholinesterase Inhibitory Activities of Balanites aegyptiaca (L.) Del. (Balanitaceae)
N.T.R. Meda,A. Lamien-Meda,M. Kiendrebeogo,C.E. Lamien
Pakistan Journal of Biological Sciences , 2010,
Abstract: The present study aimed to test the validity of Balanites aegyptiaca remedies used for the treatment of rheumatisms and mental disorders by examining the antioxidant, xanthine oxidase and acetylcholinesterase inhibitory activities of galls and leaves extracts and fractions. The total phenolics and flavonoids were measured using Folin-Ciocalteu and AlCl3 reagents, respectively. Two methods i.e., FRAP and ABTS were used to estimate the total antioxidant capacity of the plant materials. The FRAP and ABTS antioxidant activities showed that among all extracts and fractions tested, the best antioxidant activities were found with the galls dichloromethane and the leaves ethyl acetate fractions. The antioxidant activities did correlated significantly with the total phenolic and flavonoid contents. The study also showed that B. aegyptiaca galls and leaves fractions exhibited a moderate xanthine oxidase inhibitory activity comparatively to the acetylcholinesterase which was weakly inhibited by the tested extracts and fractions.
[recensione – review] La citazione. Atti del XXXI Convegno Interuniversitario (Bressanone/Brixen, 11-13 luglio 2003) , a cura di G. Peron, Padova, Esedra, 2009
Ambra Meda
Parole Rubate : Rivista Internazionale di Studi sulla Citazione , 2010,
Abstract: ReviewRecensione
Protein-Mediated Interactions of Pancreatic Islet Cells
Paolo Meda
Scientifica , 2013, DOI: 10.1155/2013/621249
Abstract:
Protein-Mediated Interactions of Pancreatic Islet Cells
Paolo Meda
Scientifica , 2013, DOI: 10.1155/2013/621249
Abstract: The islets of Langerhans collectively form the endocrine pancreas, the organ that is soley responsible for insulin secretion in mammals, and which plays a prominent role in the control of circulating glucose and metabolism. Normal function of these islets implies the coordination of different types of endocrine cells, noticeably of the beta cells which produce insulin. Given that an appropriate secretion of this hormone is vital to the organism, a number of mechanisms have been selected during evolution, which now converge to coordinate beta cell functions. Among these, several mechanisms depend on different families of integral membrane proteins, which ensure direct (cadherins, N-CAM, occludin, and claudins) and paracrine communications (pannexins) between beta cells, and between these cells and the other islet cell types. Also, other proteins (integrins) provide communication of the different islet cell types with the materials that form the islet basal laminae and extracellular matrix. Here, we review what is known about these proteins and their signaling in pancreatic β-cells, with particular emphasis on the signaling provided by Cx36, given that this is the integral membrane protein involved in cell-to-cell communication, which has so far been mostly investigated for effects on beta cell functions. 1. Introduction In vertebrates, pancreatic beta cells are the sole source of the insulin hormone [1]. The modulation of insulin secretion as a function of the changing metabolic demand and environmental conditions, specifically the levels of circulating glucose, cannot be quantitatively fulfilled by a single beta cell. Indeed, the total amount of insulin of one cell (~10?pg) will not allow for establishment and maintenance of the basal circulating levels of the hormone (~1.25?mg/L in humans). Assuming that all beta cells of the million islets which are thought to be dispersed in a human pancreas contribute to these levels, this implies that about 125 cells should simultaneously secrete in each islet. After a meal, this number should increase by about 5 to 6-fold to rapidly establish the postprandial levels of insulin, which are required to maintain normoglycemia, and be tightly regulated to ensure the peripheral oscillations of the circulating levels of the hormone, which prevent the target tissues to establish a resistance to the hormone [2–4]. Eventually, the mechanism(s) controlling these surge and oscillations should also be able to synchronously turn off the secreting cells, in order to avoid dangerous hypoglycemia, once insulin has launched its
Magneto-optical imaging technique for hostile environment: the ghost imaging approach
A. Meda,A. Caprile,A. Avella,I. Ruo Berchera,I. P. Degiovanni,A. Magni,M. Genovese
Physics , 2015, DOI: 10.1063/1.4923336
Abstract: We develop a new approach in magneto-optical imaging (MOI), applying for the first time a ghost imaging (GI) protocol to perform Faraday microscopy. MOI is of the utmost importance for the investigation of magnetic properties of material samples, through Weiss domains shape, dimension and dynamics analysis. Nevertheless, in some extreme conditions such as e. g. cryogenic temperatures or high magnetic fields application, there exists a lack of domains images due to the difficulty in creating an efficient imaging system in such environments. Here we present an innovative MOI technique that separates the imaging optical path from the one illuminating the object. The technique is based on thermal light GI and exploits correlations between light beams to retrieve the image of magnetic domains. As a proof of principle, the proposed technique is applied to the Faraday magneto-optical observation of the remanence domain structure of an yttrium iron garnet sample.
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