Browsing by Author "Contreras, Rodrigo"

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    A Mesocosm Experiment in Ecological Physiology: The Modulation of Energy Budget in a Hibernating Marsupial under Chronic Caloric Restriction
    (2022) Nespolo, Roberto F.; Fonturbel, Francisco E.; Mejias, Carlos; Contreras, Rodrigo; Gutierrez, Paulina; Oda, Esteban; Sabat, Pablo; Hambly, Catherine; Speakman, John R.; Bozinovic, Francisco
    During the past 60 years, mammalian hibernation (i.e., seasonal torpor) has been interpreted as a physiological adaptation for energy economy. However, direct field comparisons of energy expenditure and torpor use in hibernating and active free-ranging animals are scarce. Here, we followed the complete hibernation cycle of a fat-storing hibernator, the marsupial Dromiciops gliroides, in its natural habitat. Using replicated mesocosms, we experimentally manipulated energy availability and measured torpor use, hibernacula use, and social clustering throughout the entire hibernation season. Also, we measured energy flow using daily food intake, daily energy expenditure (DEE), and basal metabolic rate (BMR) in winter. We hypothesized that when facing chronic caloric restriction (CCR), a hibernator should maximize torpor frequency to compensate for the energetic deficit, compared with individuals fed ad lib. (controls). However, being torpid at low temperatures could increase other burdens (e.g., cost of rewarming, freezing risks). Our results revealed that CCR animals, compared with control animals, did not promote heat conservation strategies (i.e., clustering and hibernacula use). Instead, they gradually increased torpor frequency and reduced DEE and, as a consequence, recovered weight at the end of the season. Also, CCR animals consumed food at a rate of 50.8 kJ d(-1), whereas control animals consumed food at a rate of 98.4 kJ d(-1). Similarly, the DEE of CCR animals in winter was 47.3 & PLUSMN;5.64 kJ d(-1), which was significantly lower than control animals (DEE=88.0 & PLUSMN;5.84 kJ d(-1)). However, BMR and lean mass of CCR and control animals did not vary significantly, suggesting that animals maintained full metabolic capacities. This study shows that the use of torpor can be modulated depending on energy supply, thus optimizing energy budgeting. This plasticity in the use of heterothermy as an energy-saving strategy would explain the occurrence of this marsupial in a broad latitudinal and altitudinal range. Overall, this study suggests that hibernation is a powerful strategy to modulate energy expenditure in mammals from temperate regions.
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    Cirugía reconstructiva de la articulación temporomandibular
    (2013) Ramírez Skinner, Hernán; Goñi Espíldora, Ignacio; Contreras, Rodrigo; Zúñiga R., Sergio; Vargas Díaz, Alex Patricio; Vásquez B., Mauricio; Reinoso D. Carmen; Schulz R., Rolando; Hormazábal N., Fernando; Goñi Espíldora, Ignacio
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    Cold storage effects on oxidative stress of cv. Red Globe table grape rachises
    (2012) Campos-Vargas, Reinaldo; Zamora, Pablo; Contreras, Rodrigo; Koehler, Hans; Zuniga, Gustavo E.; Perez-Donoso, Alonso; Defilippi, Bruno G.
    R. Campos-Vargas, P. Zamora, R. Contreras, H. Kohler, G.E. Zuniga, A. Perez-Donoso, and B.G. Defilippi. 2012. Cold storage effects on oxidative stress of Red Globe table grape rachises. Cien. Inv. Agr. 39(1): 91-104. Table grape (Vitis vinifera L.) quality includes the condition of both the berries and the rachis. In the present report, physiological parameters of Red Globe rachises from fully elongated inflorescences (RFEI) and from mature clusters were studied after storage at 0 or 20 C for different durations. To understand changes in rachis physiology as a result of changes in temperature conditions and storage time, the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) were measured. In addition, hydrogen peroxide content, membrane lipoperoxidation (TBARS), total phenolic compounds and antioxidant capacity (FRAP) were assayed. TBARS was higher in mature rachises than in RFEI. This parameter remained constant throughout storage, indicating a change presumably associated with ontogeny or senescence processes. Short-term storage (0-96 11) increased SOD. CAT and APX activities in RFEI, while in mature rachises, no changes were observed in enzyme activities or in hydrogen peroxide content. Longer cold storage (25 or 53 days at 0 degrees C) of mature rachises reduced CAT activity, but SOD and APX activities did not change under these conditions. At Oh, the FRAP and total phenolic contents of mature rachises were three and 20 times higher than in immature rachises, respectively.
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    RUN1 and REN1 Pyramiding in Grapevine (Vitis vinifera cv. Crimson Seedless) Displays an Improved Defense Response Leading to Enhanced Resistance to Powdery Mildew (Erysiphe necator)
    (2017) Agurto, Mario; Schlechter, Rudolf; Armijo, Grace; Solano, esteban; Serrano Berríos, Carolina Lourdes; Contreras, Rodrigo; Zúñiga, Gustavo; Arce Johnson, Jorge Patricio