Browsing by Author "San Martin, R."
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- ItemAdenosine mediates transforming growth factor-beta 1 release in kidney glomeruli of diabetic rats(WILEY, 2009) Roa, H.; Gajardo, C.; Troncoso, E.; Fuentealba, V.; Escudero, C.; Yanez, A.; Sobrevia, L.; Pastor Anglada, M.; Quezada, C.; San Martin, R.Up regulation of the transforming growth factor-beta 1 (TGF-beta 1) axis has been recognized as a pathogenic event for progression of glomerulosclerosis in diabetic nephropathy. We demonstrate that glomeruli isolated from diabetic rats accumulate up to sixfold more extracellular adenosine than normal rats. Both decreased nucleoside uptake activity by the equilibrative nucleoside transporter 1 and increased AMP hydrolysis contribute to raise extracellular adenosine. Ex vivo assays indicate that activation of the low affinity adenosine A(2B) receptor subtype (A(2B)AR) mediates TGF-beta 1 release from glomeruli of diabetic rats, a pathogenic event that could support progression of glomerulopathy when the bioavailability of adenosine is increased. (C) 2009 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
- ItemHypoxia-reduced nitric oxide synthase activity is partially explained by higher arginase-2 activity and cellular redistribution in human umbilical vein endothelium(W B SAUNDERS CO LTD, 2011) Prieto, C. P.; Krause, B. J.; Quezada, C.; San Martin, R.; Sobrevia, L.; Casanello, P.Hypoxia relates with altered placental vasodilation, and in isolated endothelial cells, it reduces activity of the endothelial nitric oxide synthase (eNOS) and L-arginine transport. It has been reported that arginase-2 expression, an alternative pathway for L-arginine metabolism, is increased in adult endothelial cells exposed to hypoxia as well as in pre-eclamptic placentae. We studied in human umbilical vein endothelial cells (HUVEC) whether hypoxia-reduced NO synthesis results from increased arginase-mediated L-arginine metabolism and changes in subcellular localization of eNOS and arginase-2. In HUVEC exposed (24 h) to 5% (normoxia) or 2% (hypoxia) oxygen, L-arginine transport kinetics, arginase activity (urea assay), and NO synthase (NOS) activity (L-citrulline assay) were determined. Arginase-1, arginase-2 and eNOS expression were determined by RT-PCR and Western blot. Subcellular localization of arginase-2 and eNOS were studied using confocal microscopy and indirect immunofluorescence. Experiments were done in absence or presence of S-(2-boronoethyl)-L-cysteine-HCl (BEC, arginase inhibitor) or N-G-nitro-L-arginine methyl ester (L-NAME). Hypoxia-induced reduction in eNOS activity was associated with a reduction in eNOS phosphorylation at Serine-1177 and increased phosphorylation at Threonine-495. This was paralleled with an induction in arginase-2 expression and activity, and decreased L-arginine transport. In hypoxia the arginase inhibition, restored NO synthesis and L-arginine transport, without changes in the eNOS post-translational modification status. Hypoxia increased arginase-2/eNOS colocalization, and eNOS redistribution to the cell periphery. Altogether these data reinforce the thought that eNOS cell location, post-translational modification and substrate availability are important mechanisms regulating eNOS activity. If these mechanisms occur in pregnancy diseases where feto-placental oxygen levels are reduced remains to be clarified. (C) 2011 Elsevier Ltd. All rights reserved.
- ItemInsulin/adenosine axis linked signalling(2017) Silva Lagos, Luis Alfredo; Subiabre Morales, Mario Enrique; Araos, J.; Saez, T.; Salsoso Rodríguez, M. Rocío; Pardo, F.; Leiva Mendoza, Andrea Alejandra; San Martin, R.; Toledo, F.; Sobrevía Luarte, Luis Alberto
- ItemMultidrug resistance in glioblastoma stem-like cells: Role of the hypoxic microenvironment and adenosine signaling(2017) Uribe, D.; Torres, A.; Rocha, J.; Niechi, I.; Oyarzun, C.; Sobrevía Luarte, Luis Alberto; San Martin, R.; Quezada, C.
- ItemRe-Introduction of Quinoa into Arid Chile: Cultivation of Two Lowland Races under Extremely Low Irrigation(WILEY, 2009) Martinez, E. A.; Veas, E.; Jorquera, C.; San Martin, R.; Jara, P.Annual rainfall in Chile at 30 degrees S decreased from 170 to 70 mm in the last century, forcing a search for new low-rain adapted crops. Chenopodium quinoa Willd. was cultivated by pre-Hispanic cultures, but it disappeared in this region since the Spanish conquest. Two quinoa landraces (Don Javi and Palmilla) were re-introduced from lowlands of central Chile (34 degrees S) evaluating seed saponin content and grain yields under low irrigation. Replicated assays were conducted in two sites with distinct microclimates after august (end of the rains in 2004 and 2005). Treatments included low (40-75 mm) and high (150-250 mm) irrigation and were distributed along the five cultivation months. Fertilization, with the humus of the worms, was carried out in the second season, as soils are poor in organic matter. Results showed significantly higher saponin content in the seeds of Don Javi landrace (1.2 %) with respect to Palmilla seeds (0.3 %). However, grain yields were not different between landraces under the same treatments. Yields were instead affected by microclimate, irrigation and fertilization. Although higher yields corresponded with higher irrigation, 2.6 tons ha(-1) was obtained under high irrigation, but surprisingly, also under low irrigation in the more humid site. Yields of 2006 harvesting season (ca. 7 tons ha(-1)) were higher than that of the previous season (ca. 5.5 tons ha(-1)), mainly because of the addition of organic matter. We suggest that re-introduction of Quinoa in arid Chile is feasible even under the prevailing conditions of low rainfall and deficient soils, but better yields will need some irrigation and addition of organic matter.
- ItemUse of a Saponin Based Molluscicide to Control Pomacea canaliculata Snails in Southern Brazil(SAGE PUBLICATIONS INC, 2009) San Martin, R.; Gelmi, Claudio; de Oliveira, Jaime Vargas; Galo, Jose Luis; Pranto, HonorioPomocea canaliculata snails pose a severe problem to direct seeded rice cultivated in Southern Brazil. Control of this snail is nowadays performed with toxic chemicals such as copper sulfate and fungicides such as fentin. A novel natural molluscicide based on alkali modified quinoa (Chenopodium quinoa) saponins was tested under laboratory conditions. Snails were collected in rice fields close to Porto Alegre (State of Rio Grande do Sul) and in Brusque (State of Santa Catarina, 400 km north of Porto Alegre). In Santa Catarina the product was very effective, while in Porto Alegre it had no effect. This unexpected behavior was probably due to the respiratory habits of the snails under different contents of dissolved oxygen In the water. Near Porto Alegre the water used in rice fields is heavily polluted, with dissolved oxygen levels of 1-2 ppm, and the snails rely primarily oil their siphon and lungs to breathe. Since saponin control is probably due to ail interaction between saponins with the sterols present in the cell walls in the gills, no control was observed. By contrast, in Santa Catarina the dissolved oxygen level of the water is 5-6 ppm, and the snails remain mostly underwater, breathing with their gills. In this case the snails died within 24 h at a dose of 20 and 30 ppm of product. To test this observation, snails grown in polluted waters were forced to remain underwater in saponin solutions and water (control) preventing the use of their siphon to breathe. The snails exposed to saponin Solutions died, while the control snails survived, indicating that they were still able to use their gills to breathe. These results indicate that the use of the saponin product is limited to rice fields not irrigated with heavily polluted waters.