Browsing by Author "Fernandez, R."

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    Carotid body chemosensory activity and ventilatory chemoreflexes in cats persist after combined cholinergic-purinergic block
    (ELSEVIER SCIENCE BV, 2007) Reyes, E. P.; Fernandez, R.; Larrain, C.; Zapata, P.
    Acetylcholine (ACh) and ATP have been proposed as excitatory co-transmitters operating at synapses between glomus cells and sensory nerve endings of the carotid body (CB). To test such hypothesis, we performed experiments on cats under pentobarbitone anesthesia and breathing spontaneously. Cholinergic and purinergic agonists and antagonists were given into one common carotid artery. Chemoreflex ventilatory changes initiated from the ipsilateral CB or chemosensory activity from the ipsilateral carotid nerve were recorded. Agonists ACh, nicotine, epibatidine, ATP, beta gamma-methylene-ATP and gamma S-ATP induced transient chemoreflex enhancements of ventilation or increased chemosensory activity. When given in combination, mecamylamine and suramin suppressed both nicotine- and ATP-induced ventilatory chemoreflexes or chemosensory responses. However, neither chemoreflex hyperventilation induced by brief hypoxic exposures or steady-state hypoxic levels, nor chemosensory excitation elicited by these maneuvers were eliminated. Asphyxia-induced chemosensory excitation was not reduced by combined blockade of ACh and ATP receptors. Furthermore, ventilatory or chemosensory depression evoked by 100% O-2 tests was unmodified, thus evidencing that basal chemosensory drive in normoxia was not suppressed by combined cholinergic-purinergic blockade. Therefore, although ACh and ATP may participate in chemoexcitation of the CB, their involvement fails to explain the origin of chemosensory discharges from synaptic transmission between glomus cells and chemosensory nerve endings of the CB. (c) 2006 Elsevier B.V. All rights reserved.
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    Effect of the marine environment on reinforced concrete durability in lberoamerican countries: DURACON project/CYTED
    (2007) de Rincon, O. Troconis; Sanchez, M.; Millano, V.; Fernandez, R.; de Partidas, E. A.; Andrade, C.; Martinez, I.; Castellote, M.; Barboza, M.; Irassar, F.; Montenegro, J. C.; Vera, R.; Carvajal, A. M.; de Gutierrez, R. M.; Maldonado, J.; Guerrero, C.; Saborio-Leiva, E.; Villalobos, A. C.; Tres-Calvo, G.; Torres-Acosta, A.; Perez-Quiroz, J.; Martinez-Madrid, M.; Almeraya-Calderon, F.; Castro-Borges, P.; Moreno, E. I.; Perez-Lopez, T.; Salta, M.; de Melo, A. P.; Rodriguez, G.; Pedron, Miguel; Derregibus, M.
    This work presents some of the results from the project: "Effect of the environment on reinforcement durability" (DURACON) in its first two-years period, which investigates the influence of urban and marine meteorochemical parameters on the performance of reinforced concrete structures. The results presented in this investigation are from 21 marine test sites only (no urban environments are included), distributed among I I countries (Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Mexico, Spain, Uruguay, Portugal and Venezuela). The environment was evaluated using ISO Standard 9223 and the concrete was characterized by measuring compressive strength, elastic modulus, total and effective porosity, chloride permeability according to ASTM standards, as well as the effective porosity and resistance to water absorption using the Fagerlund method. To that effect, concrete specimens (with and without reinforcement) were prepared for electrochemical and physical/mechanical/chemical tests using the existing materials in each participating country, following strict procedures which enabled the preparation of similar concrete samples. Two water/cement (w/c) ratios (0.45 and 0.65) were selected, where the concrete with 0.45 w/c ratio had to have a minimum cement content of 400 kg/m(3) and the one with 0.65 w/c ratio a compressive strength of 210 kg/cm(2). Type I Portland cement, siliceous sand, and crushed rock as coarse aggregates (13-mm maximum nominal size) were used. After a one-year exposure, the results of the corrosion potentiality and probability analysis of the reinforcement in the different test stations showed that, for marine atmospheres, the most aggressive environment to induce steel corrosion was at Portugal's Cabo Raso station, and the least aggressive one was at Chile's Valparaiso station. These results are comparable with the ones found using electrochemical measurements, after a two-year exposure. (C) 2007 Elsevier Ltd. All rights reserved.
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    Effects of combined cholinergic-purinergic block upon cat carotid body chemoreceptors in vitro
    (ELSEVIER SCIENCE BV, 2007) Reyes, E. P.; Fernandez, R.; Larrain, C.; Zapata, P.
    Since acetylcholine (ACh) and ATP have been proposed as excitatory co-transmitters at synapses between glomus cells and sensory nerve endings of the carotid body (CB), we tested such hypothesis by studying the effects of combined cholinergic-purinergic block on the chemosensory activity recorded from cat's carotid bodies perfused and/or superfused in vitro. The preparations were bathed with Tyrode's solution, either normoxic (PO2 = 98.5 +/- 13.5 Torr) or hypoxic (PO2 = 31.8 +/- 5.2 Torr), and the frequency of chemosensory impulses (f(x)) was recorded from the carotid (sinus) nerve. Dose-response curves for f(x) increases evoked by intra-stream boluses of acetylcholine, nicotine and ATP were studied. A combination of mecamylamine 2 mu M and suramin 50 mu M, applied through the perfusate or superfusate, suppressed nicotine- and ATP-induced increases in f(x), but the basal chemosensory activity in normoxia and the chemosensory excitation elicited by hypoxic superfusion were preserved, although variably reduced in most preparations. Thus, in spite of the excitatory effects provoked by applying ACh and ATP to the perfused/superfused CB in vitro, a co-release of these substances cannot account entirely for the chemosensory excitation induced by hypoxic stimulation of the CB. (c) 2006 Elsevier B.V. All rights reserved.
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    Lithraea caustic (Litre) Extract Promotes an Antitumor Response Against B16 Melanoma
    (2019) Robles-Planells, C.; Michelson, S.A.; Mena, J.; Escrig, D.; Rojas, J.L.; Sanchez-Guerrero, G.; Hernandez, R.; Barrera-Avalos, C.; Rojo, L.E.; Kalergis Parra, Alexis Mikes; Sauma, D.; Imarai, M.; Fernandez, R.; Robles, C.A.; Leiva-Salcedo, E.; Santander, R.; Escobar, A.; Acuna-Castillo, C.