Rodrigo A. Vásquez

Role of adenosine transport in gestational diabetes-induced L-arginine transport and nitric oxide synthesis in human umbilical vein endothelium

Gestational diabetes is associated with increased l‐arginine transport and nitric oxide (NO) synthesis, and reduced adenosine transport in human umbilical vein endothelial cells (HUVEC). Adenosine increases endothelial l‐arginine/NO pathway via A2 purinoceptors in HUVEC from normal pregnancies. It is unknown whether the effect of gestational diabetes is associated with activation of these purinoceptors or altered expression of human cationic amino acid transporter 1 (hCAT‐1) or human equilibrative nucleoside transporter 1 (hENT1), or endothelial NO synthase (eNOS) in HUVEC. Cells were isolated from normal or gestational diabetic pregnancies and cultured up to passage 2. Gestational diabetes increased hCAT‐1 mRNA expression (2.4‐fold) and activity, eNOS mRNA (2.3‐fold), protein level (2.1‐fold), and phosphorylation (3.8‐fold), but reduced hENT1 mRNA expression (32%) and activity. Gestational diabetes increased extracellular adenosine (2.7 μm), and intracellular l‐arginine (1.9 mm) and l‐citrulline (0.7 mm) levels compared with normal cells (0.05 μm, 0.89 mm, 0.35 mm, respectively). Incubation of HUVEC from normal pregnancies with 1 μm nitrobenzylthioinosine (NBMPR) mimicked the effect of gestational diabetes, but NBMPR was ineffective in diabetic cells. Gestational diabetes and NBMPR effects involved eNOS, PKC and p42/44mapk activation, and were blocked by the A2a purinoceptor antagonist ZM‐241385. Thus, gestational diabetes increases the l‐arginine/NO pathway involving activation of mitogen‐activated protein (MAP) kinases, protein kinase C (PKC) and NO cell signalling cascades following activation of A2a purinoceptors by extracellular adenosine. A functional relationship is proposed between adenosine transport and modulation of l‐arginine transport and NO synthesis in HUVEC, which could be determinant in regulating vascular reactivity in diabetes mellitus.

Daily and seasonal limits of time and temperature to activity of degus

Presentamos un analisis de la flexibilidad conductual en la actividad diaria del degu (Octodon degus), un roedor caviomorfo, en respuesta a la heterogeneidad del ambiente temporal (diario y estacional), espacial y termico. Junto con las condiciones termicas, cuantificamos la conducta de actividad y forrajeo en una poblacion que vive en un habitat abierto en el matorral arido y estacional de Chile central. La actividad de verano fue bimodal, con 2,5 h de actividad de forrajeo intenso durante la manana y con 2 h durante la tarde. No hubo actividad por mas de 8 h entre ambos eventos. Mas de la mitad de las 4,5 h diarias de actividad de la manana y de la tarde ocurrieron en la sombra, cuando el sol se encuentra bajo la linea local del cielo. La actividad durante el otono y la primavera tambien fue bimodal pero con una mayor proporcion de actividad bajo radiacion solar directa y con un periodo de inactividad menor entre los dos eventos principales. La actividad de invierno fue unimodal y bajo radiacion solar directa. En verano, otono y primavera la actividad estuvo sesgada cuando nuestro indice de temperatura operativa, Te, supero los 40 °C. Usamos una medida de Te (registrada en un maniqui termico que representa las propiedades de forma, tamano y superficie de un degu) como un indice de los efectos interactivos de la radiacion solar y la conveccion sobre la temperatura corporal. Durante el solsticio de invierno (junio), cuando los degus permanecieron todo el dia totalmente expuestos al sol, Te generalmente permanecio bajo 30 °C. La flexibilidad en el tiempo de la actividad superficial le permitio a los degus mantener su homeostasis termica y balance de energia anual. Los degus cambiaron sus periodos de inicio y termino asi como el numero de eventos de actividad (unimodal o bimodal) durante el ano. Estos roedores permanecieron activos en la superficie bajo un rango mucho mas estrecho de condiciones termicas que las que ocurren durante el largo del dia y ano

A restriction site to differentiate Plasmodium and Haemoproteus infections in birds: on the inefficiency of general primers for detection of mixed infections

Avian Plasmodium and Haemoproteus parasites are easily detected by DNA analyses of infected samples but only correctly assigned to each genus by sequencing and use of a phylogenetic approach. Here, we present a restriction site to differentiate between both parasite genera avoiding the use of those analyses. Alignments of 820 sequences currently listed in GenBank encoding a particular cytochrome B region of avian Plasmodium and Haemoproteus show a shared restriction site for both genera using the endonuclease Hpy CH4III. An additional restriction site is present in Plasmodium sequences that would initially allow differentiation of both genera by differential migration of digested products on gels. Overall 9 out of 326 sequences containing both potential restriction sites do not fit to the general rule. We used this differentiation of parasite genera based on Hpy CH4III restriction sites to evaluate the efficacy of 2 sets of general primers in detecting mixed infections. To do so, we used samples from hosts infected by parasites of both genera. The use of general primers was only able to detect 25% or less of the mixed infections. Therefore, parasite DNA amplification using general primers to determine the species composition of haemosporidian infections in individual hosts is not recommended. Specific primers for each species and study area should be designed until a new method can efficiently discriminate both parasites.

Assessment of predation risk via illumination level: facultative central place foraging in the cricetid rodent Phyllotis darwini

It is well known that the risk of predation affects prey decision making. However, few studies have been concerned with the cues used by prey to assess this risk. Prey animals may use indirect environmental cues to assess predation hazard since direct evaluation may be dangerous. I studied the assessment of predation risk, manipulated via environmental illumination level, and the trade-off between foraging and predation hazard avoidance in the nocturnal rodent Phyllotis darwini (Rodentia: Cricetidae). In experimental arenas I simulated dark and full moon nights (which in nature correlate with low and high predation risk, respectively) and measured the immediate responses of animals to flyovers of a raptor model. Second, varying illumination only, I evaluated patch use, food consumption, central place foraging, and nocturnal variation of body weight. During flyover experiments, animals showed significantly more evasive reactions under full moon illumination than in moonless conditions. In the patch use experiments, rodents significantly increased their giving-up density and decreased their total food consumption under moonlight. On dark nights, rodents normally fed in the food patch, but when illumination was high they became central place foragers in large proportion. Moreover, the body weight of individuals decreased proportionately more during bright nights. These results strongly suggest that P. darwini uses the level of environmental illumination as a cue to the risk of being preyed upon and may sacrifice part of its energy return to avoid risky situations.

Toward an integrative understanding of social behavior: New models and new opportunities

Social interactions among conspecifics are a fundamental and adaptively significant component of the biology of numerous species. Such interactions give rise to group living as well as many of the complex forms of cooperation and conflict that occur within animal groups. Although previous conceptual models have focused on the ecological causes and fitness consequences of variation in social interactions, recent developments in endocrinology, neuroscience, and molecular genetics offer exciting opportunities to develop more integrated research programs that will facilitate new insights into the physiological causes and consequences of social variation. Here, we propose an integrative framework of social behavior that emphasizes relationships between ultimate-level function and proximate-level mechanism, thereby providing a foundation for exploring the full diversity of factors that underlie variation in social interactions, and ultimately sociality. In addition to identifying new model systems for the study of human psychopathologies, this framework provides a mechanistic basis for predicting how social behavior will change in response to environmental variation. We argue that the study of non-model organisms is essential for implementing this integrative model of social behavior because such species can be studied simultaneously in the lab and field, thereby allowing integration of rigorously controlled experimental manipulations with detailed observations of the ecological contexts in which interactions among conspecifics occur.

The relationship of telomere length to baseline corticosterone levels in nestlings of an altricial passerine bird in natural populations

BackgroundEnvironmental stressors increase the secretion of glucocorticoids that in turn can shorten telomeres via oxidative damage. Modification of telomere length, as a result of adversity faced early in life, can modify an individual’s phenotype. Studies in captivity have suggested a relationship between glucocorticoids and telomere length in developing individuals, however less is known about that relationship in natural populations.MethodsIn order to evaluate the effect of early environmental stressors on telomere length in natural populations, we compared baseline corticosterone (CORT) levels and telomere length in nestlings of the same age. We collected blood samples for hormone assay and telomere determination from two geographically distinct populations of the Thorn-tailed Rayadito (Aphrastura spinicauda) that differed in brood size; nestlings body mass and primary productivity. Within each population we used path analysis to evaluate the relationship between brood size, body mass, baseline CORT and telomere length.ResultsWithin each distinct population, path coefficients showed a positive relationship between brood size and baseline CORT and a strong and negative correlation between baseline CORT and telomere length. In general, nestlings that presented higher baseline CORT levels tended to present shorter telomeres. When comparing populations it was the low latitude population that presented higher levels of baseline CORT and shorter telomere length.ConclusionsTaken together our results reveal the importance of the condition experienced early in life in affecting telomere length, and the relevance of integrative studies carried out in natural conditions.

Basal metabolism is correlated with habitat productivity among populations of degus (Octodon degus).

Several competing hypotheses attempt to explain how environmental conditions affect mass-independent basal metabolic rate (BMR) in mammals. One of the most inclusive is the hypothesis that associates BMR with food habits, including habitat productivity. The effects of food habits have been widely investigated at the interspecific level, and variation between individuals and populations has been largely ignored. Intraspecific analysis of physiological traits has the potential to compensate for many pitfalls associated with interspecific analyses and serve as a useful approach for evaluating hypotheses regarding metabolic adaptation. Here we tested the effects of climatic variables (mean annual rainfall=PP, mean annual temperature=T(A)), net primary productivity (NPP) and the de Martonne index (DMi) of aridity on mass-independent BMR among four populations of the caviomorph rodent Octodon degus along a geographic gradient in Chile. BMR was measured on animals maintained in a common garden acclimation set-up, thus kept under the same environment and diet quality for at least 6 months. Mass-independent BMR was significantly different among degu populations showing a large intraspecific spread in metabolic rates. A very large fraction of interpopulational variability in mass-independent BMR was explained by NPP, PP and DMi. Our results were conclusive about the effects of habitat productivity on setting the level of mass-independent BMR at the intraspecific-interpopulational level.

BREEDING BIOLOGY OF THE THORN-TAILED RAYADITO (FURNARIIDAE) IN SOUTH-TEMPERATE RAINFORESTS OF CHILE

Abstract We conducted a study of the breeding biology of the Thorn-tailed Rayadito (Aphrastura spinicauda) in secondary forests on the continental island of Chiloé (42° S), southern Chile. Rayaditos are small insectivorous furnariids inhabiting the south-temperate forests of Chile and Argentina. We followed the reproduction of rayadito pairs breeding in nest-boxes. Rayaditos build their nests mainly of rhizomes and stems of epiphytic vines, grasses, and hairs during periods of at least a week, and show a marked population asynchrony in laying dates of more than two months (October–December). Rayaditos lay clutches of 3–6 eggs with a mode of 4 and laying occurs on alternate days. Eggs are 50% larger and hatchlings are 30% larger than expected from allometric equations. Most broods hatch synchronously. Nestling growth curves adjust well to logistic functions and at 2 weeks nestlings attain masses similar to asymptotic values. Nestling growth, which occurs over 3 weeks, is 27% slower than expected from allometry. Fledglings attain adult size with respect to tarsus length, but have less developed plumage and higher body mass than adults. Rayaditos exhibit clutch and brood reduction, suggesting possible food limitation. The protracted breeding periods may preclude second breeding attempts for most pairs in Chiloé. There is evidence for declines in parental quality with season. The low seasonal fecundity, large eggs, and prolonged dependence periods of a truly south-temperate species like the Thorn-tailed Rayadito reflect a ‘slow’ life history similar to that of tropical passerines. Biología Reproductiva de Aphrastura spinicauda (Furnariidae) en Bosques Lluviosos Templados Meridionales de Chile Resumen. Realizamos un estudio de la biología reproductiva del Rayadito Aphrastura spinicauda en bosques secundarios de la isla continental de Chiloé (42° S), sur de Chile. Este pequeño furnárido insectívoro habita los bosques templados meridionales de Chile y Argentina. Seguimos las actividades reproductivas de parejas de rayaditos que utilizaron cajas artificiales para nidificar. Los rayaditos construyen sus nidos utilizando rizomas, hierbas y pelo durante períodos de al menos una semana, y muestran una marcada asincronía a nivel de población de más de dos meses (octubre a diciembre) en el inicio de la puesta. Las puestas incluyen de 3 a 6 huevos, con un tamaño modal de 4 huevos, los cuales son puestos en días alternos. Los huevos son 50% más grandes y los polluelos recién eclosionados 30% más grandes de lo esperado según ecuaciones alométricas. La mayoría de las nidadas eclosionan sincrónicamente. Las curvas de crecimiento se ajustan bien a funciones logísticas y el peso alcanza valores asintóticos a las dos semanas. El crecimiento de los polluelos, que ocurre durante un período de permanencia en el nido de tres semanas, es un 27% más lento de lo esperado por alometría. Los volantones alcanzan el tamaño adulto con respecto a la longitud de tarso, pero presentan un plumaje menos desarrollado y un mayor peso que los adultos. Esta especie presenta casos de reducción de la puesta o de la nidada, lo que sugiere posibles limitaciones en la disponibilidad de alimentos. Los prolongados períodos de reproducción pueden impedir el inicio de segundas puestas en Chiloé. Hay evidencia de disminuciones estacionales en la calidad parental. La baja fecundidad anual, el gran tamaño de los huevos y el prolongado periodo de crecimiento del Rayadito refleja una historia de vida ‘lenta’ similar a la de paseriformes tropicales.

Evidence for differential maternal allocation to eggs in relation to manipulated male attractiveness in the pied flycatcher (Ficedula hypoleuca)

We present evidence of differential maternal allocation to eggs in response to manipulated male attractiveness in the migratory pied flycatcher (Ficedula hypoleuca). We manipulated the size of a male secondary sexual trait, the white forehead patch, right after male arrival to the breeding area and before female arrival. Patch size was (1) enlarged to the maximum observed in the population, (2) reduced by 40% or (3) kept constant by painting with indelible felt markers over the natural feather patch. Male behaviour was affected by the experimental manipulation, as individuals with enlarged patches performed more approaches to the nestbox in response to song playback during the territory occupation and nest-site presentation phases. Females paired with males with reduced forehead patches laid significantly smaller eggs than those paired with males in the control and enlarged-patch treatments. Laying date and clutch size did not differ among the experimental groups. We discuss that manipulations of ornaments designed to study differential allocation at laying should reduce as well as enlarge their expression.

SEXUAL DIMORPHISM AND PARENTAL ROLES IN THE THORN-TAILED RAYADITO (FURNARIIDAE)

Abstract Sexual dimorphism, mating system, and parental care are known for only a few species of the large passerine family Furnariidae. We conducted a study of sexual dimorphism in morphology, coloration, and parental roles during incubation and chick-rearing in the Thorn-tailed Rayadito (Aphrastura spinicauda), a characteristic resident ovenbird of the southern temperate rainforests of Chile and Argentina. Through molecular sexing, morphological measurements, and spectrophotometric analysis of body plumage and rectrices of reproductive adults captured on Chiloé Island (southern Chile), we determined that males were between 2% and 10% larger than females in mass, tarsus length, and wing length, while no difference was found for the length of the bill or the two longest central rectrices and their characteristic spines, or in plumage coloration. Heavy males were paired with heavy females and light males with light females. Males and females participated equally in all reproductive activities during the incubation and nestling phases, except removal of nestling feces, in which females were twice as active as males. In a study of habitat use on Navarino Island (extreme southern Chile) we found that the extended graduated tail, with rectrices that end in spines, which gives the species its name, was not used as a support while foraging and could be related to another function such as sexual or social signaling. The absence of sexual dimorphism in plumage and parental roles in rayaditos may be related to the use of the long, graduated tail as a signal of quality by both sexes, although this hypothesis requires confirmation through future mate choice studies.