Browsing by Author "Leiva, A."

Now showing 1 - 15 of 15
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    A facile approach for tuning optical and surface properties of novel biobased Alginate/POTE handleable films via solvent vapor exposure
    (ELSEVIER, 2021) Mendez Lopez, M.; Ramos Hernandez, A.; Moreno Serna, V.; Bonardd, S.; Ramirez, O.; Silva, Hernan; Inostroza Rivera, Ricardo; Diaz, D. Diaz; Leiva, A.; Saldias, C.
    Novel biobased films consisting of alginate blends with poly (octanoic acid 2-thiophen-3-yl-ethyl ester) (POTE), a conducting polymer, were prepared by solution casting, and their optical, morphological, thermal, and surface properties were studied. Using UV-visible spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), the effects of tetrahydrofuran solvent vapors on the optical properties and surface morphology of biobased films with different POTE contents were studied. Results indicate that morphological rearrangements of POTE take place during the process of solvent exposure. Specifically, the solvent vapor induced the formation of POTE small crystalline domains, which allows envisioning the potential of tuning UV-visible absorbance and wettability behavior of biobased films. Finally, theoretical electronic calculations (specifically frontier molecular orbitals analysis) provided consistent evidence on POTE's preferential orientation and selectivity toward the THF-vapor medium.
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    Amino Acid-Functionalized Polyelectrolyte Films as Bioactive Surfaces for Cell Adhesion
    (2019) Leal, M. S.; Briones, X.; Villalobos, V.; Queneau, Y.; Leiva, A.; Rios, H. E.; Pavez, J.; Silva, C. P.; Carrasco, C.; Neira-Carrillo, Andronico; Roth, A. D.; Tamayo, L.; Urzua, M. D.
    Surfaces were prepared with polyelectrolyte derivatives of poly(styrene-alt-maleic anhydride) (PSMA) functionalized with amino acids of different hydropathy indices, with the aim of evaluating the effect of the chemical functionality of polyelectrolytes on SH-SY5Y neuroblastoma cell adhesion. Functionalizing PSMA derivatives with L-glutamine, L-methionine, and L-tyrosine yielded PSMA-Gln, PSMA-Met, and PSMA-Tyr polyelectrolytes, respectively. We first studied the adsorption behavior of PSMA functionalized with amino acids on silicon wafer surfaces modified with 3-aminopropyltriethoxysilane at pH 4.0 and 7.0 and at low and high ionic strengths. The highest rate of polyelectrolyte adsorption was at pH 4.0 and high ionic strength and was higher with the glutamine and tyrosine films. The advance contact angles (BA) of the polyelectrolyte surfaces showed a moderate effect of ionic strength and pH on polyelectrolyte film wettability, with PSMA-Tyr being slightly more hydrophobic. Atomic force microscopy images of the polyelectrolyte surfaces showed two types of morphology: the well-defined globular nanostructure of PSMA-Met and PSMA-Tyr and densely packed nanofibrous-like structure of PSMA-Gln. The highest level of ionic strength caused a slight decrease in the size of the nanostructure that formed the surface domains, which was reflected in the degree of surface roughness. Cell adhesion assays with the polyelectrolyte film showed that SH-SY5Y neuroblastoma cells cultured on PSMA-Met present a well-extended morphology characterized by a stellate shape, with five or more actin-rich thin processes, whereas SH-SY5Y cells that were seeded on PSMA-Gln and PSMAT-yr have a round morphology, with fewer and shorter processes. These results indicate that it is possible to modulate the surface characteristics of polyelectrolyte films based on their chemical functionality and environmental parameters such as pH and ionic strength in order to evaluate their effect on cell adhesion. Thus, surfaces prepared from polyelectrolytes functionalized with amino acids are an attractive and simple platform for cell adhesion, which can be used in developing biomaterials with modulated surface properties.
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    Aromatic rigid poly(urethanes) containing silicon and/or germanium in the main chain
    (2005) Terraza Inostroza, Claudio; Tagle Domínguez, Luis Hernán; Leiva, A.
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    Efectos clínicos del entrenamiento muscular inspiratorio en pacientes con limitación crónica del flujo aéreo
    (1995) Lisboa Basualto, Carmen; Villafranca, Carlos; Pertuzé, Julio; Leiva, A.; Repetto Lisboa, Paula Beatriz
    The clinical role of inspiratory muscle training (IMT) in chronic obstructive pulmonary disease (COPD) has not been established, because data on its clinical effect is scarce and controversial. To further investigate these aspects we studied 20 COPD patients (FEV1 37 +/- 3% P) who were randomly and double blindly trained for 30 minutes a day during 10 weeks using a threshold inspiratory trainer with either 30% (group 1) or 10% (group 2) of PIMax as a training load. The training load was crossed after each patient completed 10 weeks of training. Effects were assessed through changes in PIMax, dyspnea through the transition dyspnea index (ITD) and the respiratory effort with Borg's score. Walking capacity was measured with the six minutes walking distance test (6WD) and depression symptoms with Beck's score. Daily life activities were also assessed. Results showed that after 10 weeks of IMT, PIMax increased in both groups (p < 0.05), dyspnea improved in group 1 as compared to group 2 (p < 0.04), 6WD increased significantly in patients of group 1, who also complained of less dyspnea (p < 0.05). Depression scores fell significantly in group 2. Daily activities improved more in group 1. After the crossover patients in group 1 disclosed a significant deterioration in PIMax whereas group 2 disclosed significant improvements in PIMax, dyspnea and 6WD. We conclude that IMT using a threshold device with 30% PIMax is a useful procedure for the treatment of severe COPD patients.
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    ENDOPLASMIC RETICULUM STRESS IN HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS FROM PRE-GESTATIONAL MATERNAL OBESITY
    (W B SAUNDERS CO LTD, 2017) Villalobos Labra, R.; Salsoso, R.; Subiabre, M.; Silva, L.; Farias Jofre, M.; Leiva, A.; Sobrevia, L.
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    High total cholesterol and triglycerides levels increase arginases metabolism, impairing nitric oxide signaling and worsening fetoplacental endothelial dysfunction in gestational diabetes mellitus pregnancies
    (2021) Contreras-Duarte, S.; Cantin, C.; Farias, M.; Leiva, A.
    Maternal physiological dyslipidemia (MPD) supports fetal development in human pregnancy. However, some women develop maternal supraphysiological dyslipidemia (MSPD: increased total cholesterol (TC) and triglycerides (TG) levels). MSPH is present in normal and also in gestational diabetes mellitus (GDM) pregnancies. MSPD and GDM associate with fetoplacental endothelial dysfunction, producing alterations in nitric oxide (NO)-L-arginine/arginase metabolism. Nevertheless, the effect of MSPD on GDM, and how this synergy alters fetoplacental endothelial function is unknown. Therefore, the aim of this study was to evaluate in human umbilical vein endothelial cells, the effects of MSPD in GDM and how these pathologies together affect the fetoplacental endothelial function. 123 women at term of pregnancy were classified as MPD (n = 40), MSPD (n = 35), GDM with normal lipids (GDM-MPD, n = 23) and with increased lipids (GDM-MSPD, n = 25). TC >= 291 mg/dL and TG >= 275 mg/dL were considered as MSPD. Endothelial NO synthase (eNOS), human cationic amino acid transporter 1 (hCat1), and arginase II protein abundance and activity, were assayed in umbilical vein endothelial cells. In MSPD and GDM-MSPD, TC and TG increased respect to MPD and GDM-MPD. eNOS activity was reduced in MSPD and GDM-MSPD, but increased in GDM-MPD compared with MPD. However, decreased tetrahydrobiopterin levels were observed in all groups compared with MPD. Increased hCatl protein and L-arginine transport were observed in both GDM groups compared with MPD. However, the transport was higher in GDM-MSPD compared to GDM-MPD. Higher Arginase II protein and activity were observed in GDM-MSPD compared with MPD. Thus, MSPD in GDM pregnancies alters fetal endothelial function associated with NO metabolism.
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    In situ synthesis and immobilization of CuO nanoparticles in alginate-poly (amido amine) nanogels for photocatalytic applications
    (2022) Cordoba, A.; Duran, B.; Bonardd, S.; Diaz Diaz, D.; Leiva, A.; Saldias, C.
    Herein, we report a feasible approach for preparation of crosslinked alginate (Alg) and poly(amido amine) (PAMAM) nanogels (Alg-PAMAM NGs), using a water-in-oil-in-water (w/o/w) double emulsion route, via strong electrostatic interactions between anionic groups coming from alginate and previously incorporated Cu2+ ions. CuO nanoparticles (NPs) with average diameter about 65 nm were in situ obtained into Alg/PAMAM nanogels by treatment of embedded Cu2+ ions in NGs with NaBH4 at 25 degrees C under air atmosphere. The prepared Alg-PAMAM and Alg-PAMAM-CuO NGs were characterized using FT-IR and UV-visible spectroscopy, as well as scanning transmission electron microscopy (STEM). The presence of PAMAM dendrimers helped both to obtain structurally compact nanogels and an adequate stabilization of CuO NPs. Finally, the photocatalytic performance of the Alg-PAMAM-CuO NGs was tested via the decomposition of methyl orange in aqueous solution, under visible light irradiation.
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    Insulin Is a Key Modulator of Fetoplacental Endothelium Metabolic Disturbances in Gestational Diabetes Mellitus
    (2016) Sobrevía Luarte, Luis Alberto; Salsoso Rodríguez, M. Rocío; Fuenzalida Saavedra, Bárbara; Barros Lamus, Eric Raúl; Toledo Valenzuela, Lilian Alejandra; Silva Lagos, Luis Alfredo; Pizarro, C.; Subiabre Morales, Mario Enrique; Villalobos, R.; Araos, J.; Toledo, F.; Gonzalez, M.; Gutierrez, J.; Farías Jofré, Marcelo Enrique; Chiarello, D.; Pardo, F.; Leiva, A.
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    Interfacial behavior of PAMAM-PCL dendrimers and in situ spontaneous formation of gold nanoparticles at the toluene-water and air-water interfaces: Experimental and theoretical studies
    (2016) Saldías, César; Méndez Lesser, Manuel; Saavedra, M.; Pereira, A.; Rojas, M.; Avila, F.; Bonardd Salvador, Sebastián Ignacio; Pino, M.; Saldías, S.; Quezada, C.; Leiva, A.; Radić Foschino, Deodato D.
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    Modulation of Intracellular pH in Human Ovarian Cancer
    (2016) Sanhueza, C.; Araos, J.; Naranjo, L.; Villalobos Labra, Roberto Esteban; Westermeier, F.; Salomon, C.; Beltran, A.; Ramirez, M.; Gutierrez, J.; Pardo, F.; Leiva, A.; Sobrevía Luarte, Luis Alberto
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    New Polymers Based on 2,6-di(thiophen-2-yl) aniline and 2,2 '-(thiophen-2,5-diyl) dianiline Monomers. Preparation, Characterization and Thermal, Optical, Electronic and Photovoltaic Properties
    (ESG, 2012) Jessop, I. A.; Zamora, P. P.; Diaz, F. R.; del Valle, M. A.; Leiva, A.; Cattin, L.; Makha, M.; Bernede, J. C.
    A new series of polymers, chemically and electrochemically obtained from monomers containing aniline and thiophene moieties, has been prepared. The purpose is to use them as electron donor layers in the fabrication of dual-layer organic solar cells. Both the monomers and the polymers were characterized using techniques such as NMR, FT-IR, cyclic voltammetry, etc. It was found that polymer growth occurred only through aniline unit(s) and not through thiophene unit(s), as might also be expected. Optical and electronic studies revealed that the products displayed properties suitable for use in photovoltaic devices. However, prepared prototypes yields ranged just between 10(-2) and 10(-3).
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    Sitagliptina, un inhibidor de la enzima DPP-IV, aumenta el colesterol plasmático total, altera el perfil de colesterol lipoproteico y disminuye el transporte reverso de colesterol en ratones
    (2010) Leiva, A.; Varas, P.; Amigo, L.; Contreras-Duarte, S.; Maíz, A.; Rigotti Rivera, Attilio
    Background: Insulin and glucagon regúlate the expression of key lipoprotein metabolism enzymes. Dyslipidemia is a significant risk factor for cardiovascular disease, the main cause of death in diabetic patients. Sitagliptine, an inhibitor of type IV dipep-tidil-peptidase (DPP-IV), controlling the metabolism of incretins, is a new hypoglycemic agent used for treatment of type II diabetes. Its effects on lipid metabolism are not clearly defined. Aim: to study the effects of sitagliptine upon parameters of cholesterol metabolism in mice. Methods: C5BL6/J mice were assigned to receive ei-ther a standard diet or one with sitagliptine supplemen-tation (0.6% P/P) for 8 weeks. DPP-IV plasma, total and lipoprotein cholesterol were measured using enzyme methods. Reverse cholesterol transport was evaluated through the peritoneal injection of cholesterol loaded macrophages followed by measurement of plasma and fecall4C labeled cholesterol. Results: compared to controls, sitagliptine treated mice exhibited a 38% decrease in plasma DPP-IV Total plasma cholesterol increased by 60% with a marked increase in HDL cholesterol. Also, an increased HDL cholesterol recovered from plasma along with a 30% decrease in fecal cholesterol was observed Finally, sitagliptine admi-nistration was associated to a decreased LDL and SR-BI hepatic receptors. Conclusión: Sitagliptine administration is associated to increased levéis of plasma cholesterol, mainly the HDL fraction, and decreased reverse cholesterol transport and fecal excretion. This effects seem to be mediated by a decreased expression of SR-BI in the liver. The expected increase in atherosclerosis associated to the atherogenic changes induced by sitagliptine should be the subject for further studies in mice.
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    Synthesis and characterization of comb-like poly(esters) containing silicon and or germanium in the main chain
    (2006) Tagle Domínguez, Luis Hernán; Terraza Inostroza, Claudio; López, L.; Leiva, A.