CAPTURA. Repositorio Academico de la Universidad de Chile
(5.176 recursos)
Captura almacena y conserva la producción de conocimiento generado por docentes e investigadores de la Universidad de Chile, y la hace visible desde los portales académicos internacionales.
Mostrando recursos 1 - 20 de 358
1.
Analgesic and behavioral effects of amphetamine enantiomers, p-methoxyamphetamine and n-alkyl-p-methoxyamphetamine derivatives - Bustamante, Diego; Díaz Véliz, Gabriela; Paeile, Carlos; Zapata Torres, Gerald; Cassels Niven, Bruce K.
The analgesic effects of (+)- and (-)-amphetamine (AMPH), (+/-)-p-methoxyamphetamine (MA), (+/-)-N-methyl-p-methoxyamphetamine (MMA) and (+/-)-N-ethyl-p-methoxyamphetamine (EMA) were compared using two different algesimetric tests in rats. In the formalin test, (+)-AMPH elicited significant antinociception at doses of 0.2, 2 and 8 mg/kg (i.p.); (-)-AMPH was active at 2 and 8 mg/kg, but not at 0.2 mg/kg; MA elicited very potent and long-lasting antinociception; MMA was less active than MA; EMA showed significant effects only at doses of 2 and 8 mg/kg. In the C-fiber evoked nociceptive reflex assay, i.v. (+)- and (-)-AMPH were ineffective, but the methoxy derivatives showed a similar pattern...
2.
Oxidative stress promotes T dephosphorylation in neuronal cells: The roles of cdk5 and pp1 - Zambrano, Cristian A.; Egaña, José T.; Núñez, Marco T.; Maccioni, Ricardo B.; González-Billault, Christian
Oxidative stress has been demonstrated to produce modifications in several intracellular proteins that lead to alterations in their activities. Alzheimer's disease is related to an increase of oxidative stress markers, which may be an early event in the progression of the disease and neurofibrillary tangles formation. Abnormal phosphorylation of tau has been implicated in the etiopathogenesis of Alzheimer's disease. By using phospho-specific antibodies, we analyzed the changes in 7 phosphorylation patterns after treatment of rat hippocarnpal and SHSY5Y human neuroblastoma cells with H2O2. We found that tau isoforms were hypophosphorylated at the Tau1 epitope after 2 h in the presence...
3.
Water economy of three Cinclodes (Furnariidae) species inhabiting marine and freshwater ecosystems - Sabat, Pablo; Nespolo, Roberto F.; Bozinovic, Francisco
Birds living in desert environments have been the preferred models for the study of physiological adaptations to water scarcity. Passerine birds living in marine coastal habitats face similar problems, yet physiological adaptations to water conservation in such species have been poorly documented. We measured total evaporative water loss (TEWL) and rates of oxygen consumption (VO2) in three species of passerine birds dwelling in marine and fresh water habitats. Mass specific total evaporative water loss was significantly lower in the marine species, Cinclodes nigrofumosus, than in species inhabiting areas near freshwater sources. We found a positive relationship between TEWL and VO2....
4.
Physiological and biochemical responses to dietary protein in the omnivore passerine Zonotrichia capensis (Emberizidae) - Sabat, Pablo; Sepúlveda-Kattan, Esteban; Maldonado, Karin
We studied the physiological, biochemical and morphological responses of the omnivore sparrow Zonotrichia capensis, a small opportunistic passerine from Central Chile acclimated to high- and low-protein diets. After 4 weeks of acclimation to 30% (high-protein group) or 7% (low-protein group) dietary casein, we collected urine and plasma for nitrogen waste production and osmometry analysis, and measured gross renal morphology. Plasma osmolality and hematocrit were not significantly affected by dietary treatment, but urine osmolality was higher in the high-protein group than in the low-protein group. Kidney and heart masses were higher in animals acclimated to the high-protein diet. Mean total nitrogen...
5.
A structure-affinity study of the opioid binding of some 3-substituted morphinans - Gómez Jeria, Juan Sebastián; Gerli Candia, Lorena A.; Hurtado, S. Marcela
A ZINDO/1 quantum-chemical structure-affinity relationship study is presented for the interaction of a group of 3-substituted morphinans with mu, delta and kappa opioid receptors. From this and previous work it is concluded that:
1. Receptor selectivity is regulated by different electronic densities located sometimes at the same atomic center. 2. The equations for the binding to the three opiate receptors are consistent with previous results obtained for other kinds of opiate molecules. 3. Internal occupied molecular orbitals are very important in regulating receptor affinity (and selectivity). 4. The role of molecular orbitals in the saturated rings needs further analysis through...
6.
Geometrical isomerism in beta-nitrostyrenes: Preferred conformations of (E)- and (Z)-1-(4-methylthiophenyl)-2-nitrobutenes - Hurtado Guzmán, Claudio; Iturriaga Vásquez, Patricio; Zapata Torres, Gerald; Cassels Niven, Bruce K.
Condensation of 4-methylthiobenzaldehyde with 1-nitropropane unexpectedly afforded separable amounts of both (E)- and (Z)-1-(4-methylthiophenyl)-2-nitrobutene. The H-1 and C-13 NMR spectra allowed the unequivocal assignment of all signals and their correlation with the preferred conformations adopted by these compounds as determined by NOESY experiments. Hartree Fock theory optimizations at the 6-311 G(d,p) level were carried out for the stereoisomeric 4-methylthionitroethene, -nitropropene, and -nitrobutene pairs, and the relative energy differences between isomers were calculated in order to estimate approximate E/Z equilibrium constants. These energy differences decrease with the increasing number of side chain carbon atoms, explaining the possibility of separating (E)- and...
7.
Diel vertical migration patterns of three zooplankton populations in a Chilean lake - Ramos-Jiliberto, Rodrigo; Carvajal, José; Carter, Mauricio; Zúñiga, Luis R.
In this work we analyzed the depth-distribution, at noon and midnight, of three zooplankton populations which are common inhabitants of lakes from central Chile and coexist in lake El Plateado. The species were Tumeodiaptomus diabolicus, Diaphanosoma chilense and Bosmina longirostris. Also, we analyzed the association between the depth-specific abundances of the groups and the depth-specific temperature and oxygen values during the sampling period. Our results show that: (1) the three population exhibited diel vertical migration during part of the year, (2) T. diabolicus and D. chilense exhibited the normal pattern of vertical migration, and B. longirostris presented both the normal...
8.
1-benzyl-1,2,3,4-tetrahydroisoquinolines. H-1 NMR conformational studies and rotational barriers - Iturriaga Vásquez, Patricio; Zapata Torres, Gerald; Caroli Rezende, Marcos; Cassels Niven, Bruce K.
The conformational preferences of a series of 1-benzyl-1,2,3,4-tetrahydroisoquinolines (norlaudanosine and coclaurine analogues) were investigated with the aid of their H-1 NMR spectra and NOESY experiments, coupled with ab initio theoretical studies to estimate energy barriers among the various stable conformers of these systems. The secondary amines prefer an extended conformation, while the N-alkylated derivatives prefer a semi-folded one, with considerable freedom to exchange between both forms. A third, folded conformation, although not much higher in energy, is relatively inaccessible.
9.
Variability in the assessment of snake predation risk by Liolaemus lizards - Labra, Antonieta; Niemeyer, Hermann
The ability to assess and respond to predation risk is a strong selective force. Detection of predators is carried out by one or more sensory modalities, but the use of chemoreception has significant advantages. This study examines the chemosensorial assessment of snake predation risk and corresponding behaviours in different species and populations of Liolaemus lizards naturally exposed to different levels of snake predation pressure. The species studied were sympatric (Liolaemus lemniscatus), parapatric (L. nigroviridis) and allopatric (L. fitzgeraldi) to the saurophagous snake, Philodryas chamissonis. Additionally, two populations of L. lemniscatus from areas differing in snake densities were compared. Chemo-assessment of...
10.
Short nanotubes or big molecules? The concept of minimal length - Gómez Jeria, Juan Sebastián; Soto Morales, Francisco
We have studied the problem of what must be the minimal length of a nanotube with a given diameter to reasonably assert that its electronic properties can be extrapolated to longer structures. For this purpose the variation of the electronic chemical potential (ECP) was plotted against the number of units composing the nanotube for three systems: (5,5) armchair, (9,0) zigzag and (10,0) zigzag nanotubes. We found that the ECP curve defines a different minimal length for each system. This minimal length corresponds to the boundary between large molecules (short nanotubes) and nanotubes properly speaking. We suggest that this minimal length...
11.
Large-scale patterns of signal evolution: an interspecific study of Liolaemus lizard headbob displays - Martins, Emilia P.; Labra, Antonieta; Halloy, Monique; Thompson, Julie Tolman
Although many factors have been shown to influence the evolution of species recognition signals in a wide variety of taxa, it is difficult to draw general conclusions because of fundamental differences in the morphologies and ecologies of the animals considered. In this study, two morphologically and ecologically similar lizard genera (Sceloporus and Liolaemus) are used to provide replicate examples of the evolution of a complex visual display. New data on the headbob displays of 16 Liolaemus species are presented. As in other taxa, phylogenetic analyses show that evolutionary changes in display structure have been rapid, leaving little, if any, phylogenetic...
12.
Interleukin-6 induces Alzheimer-type phosphorylation of tau protein by deregulating the cdk5/p35 pathway - Quintanilla, Rodrigo A.; Orellana, Daniel I.; González-Billault, Christian; Maccioni, Ricardo B.
Inflammation is a process that has been actively related with the onset of several neurodegenerative disorders including Alzheimer disease (AD). However, the precise implications of inflammatory response for neurodegeneration have not been elucidated. A current hypothesis considers that extracellular insults to neurons could trigger the production of inflammatory cytokines by astrocytes and microglia. These cytokines.. namely, interleukin (IL)-1beta, TNFalpha, and IL-6, could affect the normal behavior of neuronal cells. In the present study, we describe the effect of the administration at physiologic doses of one of these cytokines, IL-6, to hippocampal neurons, on the protein kinase pathways as well as...
13.
Progressive iron accumulation induces a biphasic change in the glutathione content of neuroblastoma cells - Núñez, Marco T.; Gallardo, Vivian; Muñoz, Patricia; Tapia, Victoria; Esparza, Andrés; Salazar, Julio; Speisky, Hernán
Glutathione (GSH) constitutes the single most important antioxidant in neurons, whereas iron causes oxidative stress that leads to cell damage and death. Although GSH and iron produce opposite effects on redox cell status, no mechanistic relationships between iron and GSH metabolism are known. In this work, we evaluated in SHSY5Y neuroblastoma cells the effects of iron accumulation on intracellular GSH metabolism. After 2 d exposure to increasing concentrations of iron, cells underwent concentration-dependent iron accumulation and a biphasic change in intracellular GSH levels. Increasing iron from 1 to 5 muM resulted in a marked increase in intracellular oxidative stress and...
14.
Digestive morphology and enzyme activity in the Andean toad, Bufo spinulosus: hard-wired or flexible physiology? - Naya, Daniel; Farfán, Gonzalo; Sabat, Pablo; Méndez, Marco; Bozinovic, Francisco
Gut plasticity is a trait with implications on animal performance. However, and despite their importance as study models in physiology, research on gut flexibility in amphibians is scarce. In the present work, we analyse digestive adjustments of Bufo spinulosus adult individuals to cope with changes in diet quality and quantity at two organizational levels (i.e., digestive morphology and enzymes). We found that changes in gut:size are related to the amount of food ingested, but not to diet composition. This is in agreement with "the gut seasonal change" hypothesis and offers a proximal explanation for this change. Digestive enzymatic activity (maltase...
15.
Intraspecific differences in metabolic rate of Chroeomys olivaceus (Rodentia : Muridae): the effect of thermal acclimation in arid and mesic habitats - Novoa, Fernando; Rivera Hutinel, Antonio; Rosenmann, Mario; Sabat, Pablo
Studies of metabolic capacities in rodents have been largely Studied at an inter-specific levels, but physiological capacities of populations belonging to the same species have received lesser attention. Here we studied the maximum and basal metabolic rates Of two Populations of the rodent Chroeomys olivaceus dwelling in habitats with contrasting temperature and rainfall regimes, and to test if differences ill metabolic capacities are due to local adaptation or acclimatization effect. After four weeks of acclimation to 25 and 10 degrees C, the BMR arid MMR were determined in individuals from the northern population of Caleta Loa, and the southern population...
16.
A convenient, renewable source of the anxiolytic proaporphine alkaloid glaziovine: Duguetia vallicola leaves - Pérez, Edwin; Sáez, Jairo; Cassels Niven, Bruce K.
The leaves of Duguetia vallicola, a fairly common, large evergreen tree from the coastal regions of Panama, Colombia and Venezuela, contain (6aS)-glaziovine (1) as a major constituent. The abundance and renewable character of the plant material make it an attractive source for this rare, psychoactive alkaloid. The availability of glaziovine and its 0-methyl derivative pronuciferine (2) has made complete H-1 and C-13 NMR assignments of proaporphines possible for the first time.
17.
Resource - consumer models and the biomass conversion principle - Ramos-Jiliberto, Rodrigo
In the search for a unified basis for constructing food-web models, the long-standing discrepancy between biomass conversion (BC) and individual survival (IS) modeling has been revitalized by Ginzburg (J. Anim. Ecol. 67 (1998) 325) and Berryman (J. Anim. Ecol. 68 (1999) 1263) in the context of resource-consumer interactions. In this work, the principles underlying the confronting approaches are summarized and the criticisms addressed against each. Also, it is argued that the achievement of a single theory of resource-consumer ecology could benefit from this debate by incorporating key elements of both approaches. A logical procedure is suggested to build simple continuous...
18.
Phenotypic flexibility in the intestinal enzymes of the African clawed frog Xenopus laevis - Sabat, Pablo; Riveros, José Miguel; López Pinto, Carlos
The intestinal plasticity of digestive enzymes of amphibian species is poorly known. The goal of this study was to characterize digestive enzyme profiles along the small intestine of adult frogs, Xenopus laevis, in response to an experimental diet. We acclimated adult X. laevis for 30 days either to carbohydrate-rich or protein-rich diets, and determined the morphology and digestive enzymes of the small intestine. We found a significant difference of aminopeptidase-N activity between carbohydrate-rich and protein-rich acclimated animals. We also found a little variation in the expression of maltase activity, which contrast with the proposed hypothesis about the existence of digestive...
19.
Seasonal changes in the use of marine food resources by Cinclodes nigrofumosus (furnariidae, aves): carbon isotopes and osmoregulatory physiology - Sabat, Pablo; Martínez del Río, Carlos
Passerines lack functional salt glands and to a large extent avoid feeding on marine invertebrates. An exception is Cinclodes nigrofulnosits. Previous studies reported that the contents of its gastrointestinal tract had a lower osmolality than seawater suggesting that birds were supplementing their marine invertebrate diet with terrestrial invertebrates and fresh water at certain periods of the year. We report seasonal changes in the diet of C. nigrofumosus at two contrasting coastal localities in Central Chile and document the potential correlation between weather and feeding habits with osmoregulatory features in this species. We expected that C.nigrofumosus would increase its use of...
20.
Chronic intermittent hypoxia enhances cat chemosensory and ventilatory responses to hypoxia - Rey, Sergio; Río, Rodrigo del; Alcayaga, Julio; Iturriaga, Rodrigo
The carotid body (CB) chemoreceptors may play an important role in the enhanced hypoxic ventilatory response induced by chronic intermittent hypoxia (CIH). We studied the effects of cyclic hypoxic episodes of short duration on cat cardiorespiratory reflexes, heart rate variability, and CB chemosensory activity. Cats were exposed to cyclic hypoxic episodes (Po-2 similar to 75 Torr) repeated during 8 h for 2-4 days. Cats were anaesthetized with sodium pentobarbitone (40 mg kg(-1) (I.P.,) followed by 8-12 mg (I.V.)), and ventilatory and cardiovascular responses to NaCN (0.1-100 pg kg(-1) (I.V.)) and several isocapnic levels of oxygen (Po-2 similar to 20-740 Torr)...
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