DSpace Angular :: Browsing by Author "Gonzalez, Marcelo"

Browsing by Author "Gonzalez, Marcelo"

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A Role for Insulin on L-Arginine Transport in Fetal Endothelial Dysfunction in Hyperglycaemia
(BENTHAM SCIENCE PUBL LTD, 2009) Sobrevia, Luis; Gonzalez, Marcelo
Endothelial cells are key in the regulation of vascular tone through the release of vasoactive molecules, including nitric oxide (NO). NO is a gas synthesized from the cationic amino acid L-arginine via the endothelial NO synthase (eNOS). The semi-essential amino acid L-arginine is a taken up by endothelial cells via systems y(+) and y(+)L in primary cultures of human umbilical vein endothelial cells (HUVEC). System y(+) is a family of membrane transporters including at least five transport systems for cationic amino acids (CAT) of which HUVEC express human CAT-1 (hCAT-1) and hCAT-2B. Exposure of HUVEC to high extracellular concentrations of D-glucose increases L-arginine transport, hCAT-1 mRNA expression and eNOS activity. These phenomena are also related with increased production of reactive oxygen species (ROS), thus supporting the possibility that changes in L-arginine/NO signalling pathway result from elevated ROS. It has been shown that insulin blocks D-glucose-increased L-arginine transport and cGMP accumulation in HUVEC, whereas in this cell type insulin also modulates high D-glucose effects by activating the transcriptional factors Sp1 and NF kappa B. These transcription factors have response elements in SLC7A1 (for hCAT-1) gene promoter region, thus representing 2 possible targets for regulation of the expression of this transporter by D-glucose and/or insulin in this cell type. Recent evidences suggest that insulin blocks the stimulatory effect of D- glucose on L-arginine transport by reducing the transcriptional activity of SLC7A1 via Sp1-, NF kappa B- and ROS-dependent mechanisms. Thus, a role for these transcription factors in response to insulin is proposed in fetal endothelial cells exposed to hyperglycaemia.
Comparison of the electrochemical decarbonation of different-grade limestones used in cement manufacturing
(2023) Ramirez-Amaya, Dario; Dreyse, Paulina; Martinez, Natalia P.; Troncoso, Felipe; Navarrete, Ivan; Noel, Martin; Canales, Roberto I.; Gonzalez, Marcelo
Electrochemical decarbonation (ED) of CaCO3 is a promising method to reduce CO2 emissions from limestone calcination for cement manufacturing. Most cement plants are located near accessible deposits of limestone; therefore, the feasibility of ED deployment depends on the efficiency of natural limestone decarbonation, which has variable CaCO3 content. Accordingly, this research compares the ED efficiency of different limestones (CaCO3 content between 84 % and 68 %) and the chemical and physical characteristics of precipitate materials (PM) obtained from this process. The obtained PMs were comprised mainly of Ca(OH)(2) (similar to 59 %) and had similar particle size distributions. At the same time, the efficiency of Ca(OH)(2) precipitation, energy consumption, and CaO recovery were comparable to the ED of a pure CaCO3 reagent (>99 %). The PMs were found to have higher CaO content and lower loss on ignition than the feedstock material, independent of the type of limestone, facilitating the future ED implementation in cement manufacturing.
High D-Glucose reduces SLC29A1 promoter activity and adenosine transport involving specific protein 1 in human umbilical vein endothelium
(WILEY, 2008) Puebla, Carlos; Farias, Marcelo; Gonzalez, Marcelo; Vecchiola, Andrea; Aguayo, Claudio; Krause, Bernardo; Pastor Anglada, Marcal; Casanello, Paola; Sobrevia, Luis
High D-glucose reduces human equilibrative nucleoside transporter 1 (hENT1)-mediated adenosine uptake involving endothelial nitric oxide synthase (eNOS), mitogen-activated protein (MAP) kinase kinases 1 and 2/MAP kinases p42/44 (MEK/ERKs), and protein kinase C (PKC) activation in human umbilical vein endothelium (HUVEC). Since NO represses SLC29A1 gene (hENT1) promoter activity we studied whether D-glucose-reduced hENT1-adenosine transport results from lower SLC29A1 expression in HUVEC primary cultures. HUVEC incubation (24 h) with high D-glucose (25 mM) reduced hENT1-adenosine transport and pGL3-hENT1(-1114) construct SLC29A1 reporter activity compared with normal D-glucose (5 mM). High D-glucose also reduced pGL3-hENT1(-1114) reporter activity compared with cells transfected with pGL3-hENT1(-795) Construct. N-G-nitro-L-arginine methyl ester (L-NAME, NOS inhibitor), PD-98059 (MEK1/2 inhibitor), and/or calphostin C (PKC inhibitor) blocked D-glucose effects. Insulin(1 nM) and phorbol 12-myristate 13-acetate (PMA, 100 nM, PKC activator), but not 4 alpha-phorbol 12,13-didecanoate (4 alpha PDD, 100 nM, PMA less active analogue) reduced hENT1-adenosine transport. L-NAME and PD-98059 blocked insulin effects. L-NAME, PD-98059, and calphostin C increased hENT1 expression without altering protein or mRNA stability. High D-glucose increased Sp1 transcription factor protein abundance and binding to SLC29A1 promoter, phenomena blocked by L-NAME, PD-98059, and calphostin C. Sp1 overexpression reduced SLC29A1 promoter activity in normal D-glucose, an effect reversed by L-NAME and further reduced by S-nitroso-N-acetyl-L,D-penicillamine (SNAP, NO donor) in high D-glucose. Thus, reduced hENT1 -mediated adenosine transport in high D-glucose may result from increased Sp1 binding to SLC29A1 promoter down-regulating hENT1 expression. This phenomenon depends on eNOS, MEK/ERKs, and PKC activity, suggesting potential roles for these molecules in hyperglycemia-associated endothelial dysfunction.
Improving concrete underground mining pavements performance through the synergic effect of silica fume, nanosilica, and polypropylene fibers
(2021) Brescia-Norambuena, Leonardo; Gonzalez, Marcelo; Avudaiappan, Siva; Saavedra Flores, Erick, I; Grasley, Zachary
Concrete pavements for underground mining are in service under very aggressive exposure conditions (heavy loads and chemical attacks), which reduce their service life and affect mining productivity. Aiming to improve the concrete's performance, the combined use of silica fume, nanosilica, and polypropylene fibers was investigated. While each of these materials contributes independently to improving concrete performance, the similar chemistry of nanosilica and silica fume and the considerable workability loss by using each of these materials could negatively impact the concrete properties when used together. Therefore, it is necessary to demonstrate the synergy of using these three materials together, and quantify their relevance in the concrete response. In comparison to the control mix, the concrete mixes with the combined additions showed an average improvement of i) 17% of compressive strength, ii) 23% of splitting strength, and iii) 22% of flexural strength, iv) 200% of the surface resistivity, v) 212% of the abrasion resistance, and vi) 158% of less sulfate expansion. As the numerical modelling of the results indicated a statistically significant interaction between the independent variables, it is proposed that the silica fume, nanosilica, and fibers act synergically, enhancing the underground mining pavements. (C) 2021 Elsevier Ltd. All rights reserved.
Influence of conventional and functionalized carbon nanotubes in hybrid alkaline pastes with fly ash that contain high amounts of SO₄
(2021) Vasquez, Jeison; Gonzalez, Marcelo; Vergara, Paulina; Munoz, Jose F.; Arellano, Juan; Escalona Burgos, Nestor
This research investigates the effect of incorporating conventional and functionalized carbon nanotubes into a cementitious matrix made of 30% cement and 70% fly ash with high amounts of sulfate. Carbon nanotubes were added in different proportions, and the mechanical and physical properties were evaluated through a compressive strength and minibar test, respectively. The results showed that carbon nanotubes improve the compressive strength up to 17% and the expansion is reduced by 10 times. This research is novel because application of carbon nanotubes in hybrid alkaline pastes with fly ash that contain high amounts of sulfate has not been investigated before. (c) 2021 Elsevier Ltd. All rights reserved.
Insulin Restores Gestational Diabetes Mellitus Reduced Adenosine Transport Involving Differential Expression of Insulin Receptor Isoforms in Human Umbilical Vein Endothelium
(AMER DIABETES ASSOC, 2011) Westermeier, Francisco; Salomon, Carlos; Gonzalez, Marcelo; Puebla, Carlos; Guzman Gutierrez, Enrique; Cifuentes, Fredi; Leiva, Andrea; Casanello, Paola; Sobrevia, Luis
OBJECTIVE-To determine whether insulin reverses gestational diabetes mellitus (GDM)-reduced expression and activity of human equilibrative nucleoside transporters 1 (hENT1) in human umbilical vein endothelium cells (HUVECs).
Insulin-Increased L-Arginine Transport Requires A(2A) Adenosine Receptors Activation in Human Umbilical Vein Endothelium
(PUBLIC LIBRARY SCIENCE, 2012) Guzman Gutierrez, Enrique; Westermeier, Francisco; Salomon, Carlos; Gonzalez, Marcelo; Pardo, Fabian; Leiva, Andrea; Sobrevia, Luis
Adenosine causes vasodilation of human placenta vasculature by increasing the transport of arginine via cationic amino acid transporters 1 (hCAT-1). This process involves the activation of A(2A) adenosine receptors (A(2A)AR) in human umbilical vein endothelial cells (HUVECs). Insulin increases hCAT-1 activity and expression in HUVECs, and A(2A)AR stimulation increases insulin sensitivity in subjects with insulin resistance. However, whether A(2A)AR plays a role in insulin-mediated increase in L-arginine transport in HUVECs is unknown. To determine this, we first assayed the kinetics of saturable L-arginine transport (1 minute, 37 degrees C) in the absence or presence of nitrobenzylthioinosine (NBTI, 10 mu mol/L, adenosine transport inhibitor) and/or adenosine receptors agonist/antagonists. We also determined hCAT-1 protein and mRNA expression levels (Western blots and quantitative PCR), and SLC7A1 (for hCAT-1) reporter promoter activity. Insulin and NBTI increased the extracellular adenosine concentration, the maximal velocity for L-arginine transport without altering the apparent K-m for L-arginine transport, hCAT-1 protein and mRNA expression levels, and SLC7A1 transcriptional activity. An A2AAR antagonist ZM-241385 blocked these effects. ZM241385 inhibited SLC7A1 reporter transcriptional activity to the same extent in cells transfected with pGL3-hCAT-1(-1606) or pGL3-hCAT-1(-650) constructs in the presence of NBTI + insulin. However, SLC7A1 reporter activity was increased by NBTI only in cells transfected with pGL3-hCAT-1(-1606), and the ZM-241385 sensitive fraction of the NBTI response was similar in the absence or in the presence of insulin. Thus, insulin modulation of hCAT-1 expression and activity requires functional A(2A)AR in HUVECs, a mechanism that may be applicable to diseases associated with fetal insulin resistance, such as gestational diabetes.
Insulin-Stimulated L-Arginine Transport Requires SLC7A1 Gene Expression and Is Associated With Human Umbilical Vein Relaxation
(WILEY, 2011) Gonzalez, Marcelo; Gallardo, Victoria; Rodriguez, Natalia; Salomon, Carlos; Westermeier, Francisco; Guzman Gutierrez, Enrique; Abarzua, Fernando; Leiva, Andrea; Casanello, Paola; Sobrevia, Luis
Insulin causes endothelium-derived nitric oxide (NO)-dependent vascular relaxation, and increases L-arginine transport via cationic amino acid transporter 1 (hCAT-1) and endothelialNOsynthase (eNOS) expression and activity in human umbilical vein endothelium (HUVEC). We studied insulin effect on SLC7A1 gene (hCAT-1) expression and hCAT-transport activity role in insulin-modulated human fetal vascular reactivity. HUVEC were used for L-arginine transport and L-[H-3] citrulline formation (NOS activity) assays in absence or presence of N-ethylmaleimide (NEM) or L-lysine (L-arginine transport inhibitors). hCAT-1 protein abundance was estimated by Western blot, mRNA quantification by real time PCR, and SLC7A1 promoter activity by Luciferase activity (-1,606 and -650 bp promoter fragments from ATG). Specific protein 1 (Sp1), and total or phosphorylatedeNOSprotein was determined by Western blot. Sp1 activity (at four sites between -177 and -105 bp from ATG) was assayed by chromatin immunoprecipitation (ChIP) and vascular reactivity in umbilical vein rings. Insulin increased hCATs-L-arginine transport, maximal transport capacity (V-max/K-m), and hCAT-1 expression. NEM and L-lysine blocked L-arginine transport. In addition, it was trans-stimulated (similar to 7.8-fold) by L-lysine in absence of insulin, but unaltered (similar to 1.4-fold) in presence of insulin. Sp1 nuclear protein abundance and binding to DNA, and SLC7A1 promoter activity was increased by insulin. Insulin increasedNOsynthesis and caused endothelium-dependent vessel relaxation and reduced U46619-induced contraction, effects blocked by NEM and L-lysine, and dependent on extracellular L-arginine. We suggest that insulin induces human umbilical vein relaxation by increasing HUVEC L-arginine transport via hCATs (likely hCAT-1) most likely requiring Sp1-activated SLC7A1 expression. J. Cell. Physiol. 226: 2916-2924, 2011. (C) 2011 Wiley-Liss, Inc.
Short- and long-term experimental performance of concrete with copper slag: Mechanical and physical properties assessment
(2024) Silva, Yimmy Fernando; Burbano-Garcia, Claudia; Araya-Letelier, Gerardo; Gonzalez, Marcelo
Industrial waste management has increased in recent years and, at the same time, the production of more sustainable and high-performance concrete has become one of the most important challenges related to the built environment. To contribute to face the previously mentioned challenges, this paper presents an experimental study on the influence of copper slag (CS) as a supplementary cementitious material (SCM) on the physical and mechanical concrete performance at both short- and long -terms. The CS was incorporated to concrete using five increasing levels (0 %, 10 %, 20 %, 30 % and 50 % vol.) as SCM and both fresh state (slump) and hardened state (compressive strength, indirect tensile strength, flexural strength, porosity and capillary suction) properties of concretes were evaluated. The results showed that the highest slump was achieved by the concrete mixture with 50 % CS, reaching a 27 % increment compared to the reference concrete (0 % CS). In the hardened state, both average compressive and splitting tensile strength values monotonically decreased with increasing CS content at short ages (28 days). However, at 360 days, the 10 % SC concrete mixture presented average compressive and splitting tensile strengths of 57 MPa and 4.9 MPa, respectively, reaching and exceeding the corresponding strength values of the reference concrete, respectively. In addition, the mixture with 10 % CS obtained the highest average flexural strength, reaching a 3.2 % and 3.5 % increment compared to the reference mixture at 28 and 360 days, respectively, which might be attributed to the more angular shape of the CS particles compared to the cement particles. In terms of physical properties, voids and absorption values increased as the CS content increased, yet at 360 days of curing, the only concrete that presented higher values than the reference concrete was the mixture with 50 % CS (increments of 5.6 % and 5.4 % for voids and absorption, respectively). In conclusion, this study showed the advantageous potential use of CS as SCM at low percentages (between 10 % and 20 %), especially in long term performance of concrete mixtures.

Browsing by Author "Gonzalez, Marcelo"

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