172 research outputs found
Moonstruck Primates: Owl Monkeys (Aotus) Need Moonlight for Nocturnal Activity in Their Natural Environment
Primates show activity patterns ranging from nocturnality to diurnality, with a few species showing activity both during day and night. Among anthropoids (monkeys, apes and humans), nocturnality is only present in the Central and South American owl monkey genus Aotus. Unlike other tropical Aotus species, the Azara's owl monkeys (A. azarai) of the subtropics have switched their activity pattern from strict nocturnality to one that also includes regular diurnal activity. Harsher climate, food availability, and the lack of predators or diurnal competitors, have all been proposed as factors favoring evolutionary switches in primate activity patterns. However, the observational nature of most field studies has limited an understanding of the mechanisms responsible for this switch in activity patterns. The goal of our study was to evaluate the hypothesis that masking, namely the stimulatory and/or inhibitory/disinhibitory effects of environmental factors on synchronized circadian locomotor activity, is a key determinant of the unusual activity pattern of Azara's owl monkeys. We use continuous long-term (6–18 months) 5-min-binned activity records obtained with actimeter collars fitted to wild owl monkeys (n = 10 individuals) to show that this different pattern results from strong masking of activity by the inhibiting and enhancing effects of ambient luminance and temperature. Conclusive evidence for the direct masking effect of light is provided by data showing that locomotor activity was almost completely inhibited when moonlight was shadowed during three lunar eclipses. Temperature also negatively masked locomotor activity, and this masking was manifested even under optimal light conditions. Our results highlight the importance of the masking of circadian rhythmicity as a determinant of nocturnality in wild owl monkeys and suggest that the stimulatory effects of dim light in nocturnal primates may have been selected as an adaptive response to moonlight. Furthermore, our data indicate that changes in sensitivity to specific environmental stimuli may have been an essential key for evolutionary switches between diurnal and nocturnal habits in primates
Estimation of the water balance of for a small tropical andean catchment
The present study seeks to estimate the water balance for a tropical catchment in the Andes of Ecuador. Temporal variation in precipitation and temperature of the Chaquilcay microcatchment were studied; it is a natural ecosystem situated in the Aguarongo Protected Forest in Gualaceo, Ecuador. Four meteorological stations of the National Institute of Meteorology and Hydrology (INAMHI-Instituto Nacional de Meteorología e Hidrología) were studied for 33 years (1982-2015), in order to quantify the contributions and losses of water, and statistical analyzes of the time series. To fill and validate the series of precipitation and temperature, a double mass analysis was used to develop reference stations and fill missing records. Temperature data were supplemented with the isothermal raster of Ecuador. A digital elevation model (DEM) was used to predict the amount of sun light, and the Thornthwaite method (1948) was applied to estimate time series of evapotranspiration. Our water balance analysis indicates 843;7 mm of total annual precipitation, a storage difference of 18;71 mm representing 2;22% of the total annual precipitation, surplus of 144;5 mm, and current evapotranspiration of 680;5 mm, amounting to 17;13% and 80;65% of the total annual precipitation, respectively
ESTIMACIÓN DEL BALANCE HÍDRICO DE UNA CUENCA ANDINA TROPICAL
El presente estudio estima el balance hídrico para una cuenca tropical en los Andes de Ecuador. Se estudió la variación temporal de la precipitación y la temperatura de la microcuenca Chaquilcay, ecosistema natural situado dentro del Bosque y Vegetación Protector Aguarongo en Gualaceo, Ecuador. Para examinar la variabilidad temporal de la temperatura y la precipitación, se estudiaron cuatro estaciones meteorológicas del Instituto Nacional de Meteorología e Hidrología (INAMHI) durante el periodo 1982 a 2015. Para cuantificar las contribuciones y pérdidas de agua, se llevaron a cabo análisis estadísticos de las series temporales. Mientras que, para llenar y validar las series de precipitación y temperatura, se utilizó un análisis de doble masa desarrollando estaciones de referencia y con ello completar los registros faltantes. Los datos de temperatura se complementaron con la trama isotérmica del Ecuador. Además, se usó un modelo de elevación digital (MED) para predecir la cantidad de luz solar y se aplicó el método de Thornthwaite (1948) para estimar series temporales de evapotranspiración. El análisis de balance hídrico indica 843;7 mm de
precipitación anual total, una diferencia de almacenamiento de 18;71 mm que representa el 2;22% de la precipitación anual total, un excedente de 144;5 mm y una evapotranspiración real de 680;5 mm, que asciende a 17;13% y 80;65% del total anual de precipitación, respectivamente.// The present study seeks to estimate the water balance for a tropical catchment in the Andes of Ecuador. Temporal variation in precipitation and temperature of the Chaquilcay microcatchment were studied; it is a natural ecosystem
situated in the Aguarongo Protected Forest in Gualaceo, Ecuador. Four meteorological stations of the National Institute of Meteorology and Hydrology (INAMHI - Instituto Nacional de Meteorología e Hidrología) were studied for 33 years (1982-2015), in order to quantify the contributions and losses of water, and statistical analyzes of the time series. To fill and validate the series of precipitation and temperature, a double mass analysis was used to develop reference stations and fill missing records. Temperature data were supplemented with the isothermal raster of Ecuador. A digital elevation model (DEM) was used to predict the amount of sun light, and the Thornthwaite method (1948) was applied to estimate time series of evapotranspiration. Our water balance analysis indicates 843;7 mm of total annual precipitation, a storage difference of 18;71 mm representing 2;22% of the total annual precipitation, surplus of 144;5 mm, and current evapotranspiration of 680;5 mm, amounting to 17;13% and 80;65% of the total annual precipitation,
respectively
Axiomatic systems and topological semantics for intuitionistic temporal logic
We propose four axiomatic systems for intuitionistic linear temporal logic
and show that each of these systems is sound for a class of structures based
either on Kripke frames or on dynamic topological systems. Our topological
semantics features a new interpretation for the `henceforth' modality that is a
natural intuitionistic variant of the classical one. Using the soundness
results, we show that the four logics obtained from the axiomatic systems are
distinct. Finally, we show that when the language is restricted to the
`henceforth'-free fragment, the set of valid formulas for the relational and
topological semantics coincide
Bevacizumab dose adjustment to improve clinical outcomes of glioblastoma.
Background
Glioblastoma (GBM) is one of the most aggressive and vascularized brain tumors in adults, with a median survival of 20.9 months. In newly diagnosed and recurrent GBM, bevacizumab demonstrated an increase in progression-free survival, but not in overall survival.
Methods
We conducted an in silico analysis of VEGF expression, in a cohort of 1082 glioma patients. Then, to determine whether appropriate bevacizumab dose adjustment could increase the anti-angiogenic response, we used in vitro and in vivo GBM models. Additionally, we analyzed VEGFA expression in tissue, serum, and plasma in a cohort of GBM patients before and during bevacizumab treatment.
Results
We identified that 20% of primary GBM did not express VEGFA suggesting that these patients would probably not respond to bevacizumab therapy as we proved in vitro and in vivo. We found that a specific dose of bevacizumab calculated based on VEGFA expression levels increases the response to treatment in cell culture and serum samples from mice bearing GBM tumors. Additionally, in a cohort of GBM patients, we observed a correlation of VEGFA levels in serum, but not in plasma, with bevacizumab treatment performance.
Conclusions
Our data suggest that bevacizumab dose adjustment could improve clinical outcomes in Glioblastoma treatment.post-print1360 K
Disease Severity in Patients Infected with Leishmania mexicana Relates to IL-1β
Leishmania mexicana can cause both localized (LCL) and diffuse (DCL) cutaneous leishmaniasis, yet little is known about factors regulating disease severity in these patients. We analyzed if the disease was associated with single nucleotide polymorphisms (SNPs) in IL-1β (−511), CXCL8 (−251) and/or the inhibitor IL-1RA (+2018) in 58 Mexican mestizo patients with LCL, 6 with DCL and 123 control cases. Additionally, we analyzed the in vitro production of IL-1β by monocytes, the expression of this cytokine in sera of these patients, as well as the tissue distribution of IL-1β and the number of parasites in lesions of LCL and DCL patients. Our results show a significant difference in the distribution of IL-1β (−511 C/T) genotypes between patients and controls (heterozygous OR), with respect to the reference group CC, which was estimated with a value of 3.23, 95% CI = (1.2, 8.7) and p-value = 0.0167), indicating that IL-1β (−511 C/T) represents a variable influencing the risk to develop the disease in patients infected with Leishmania mexicana. Additionally, an increased in vitro production of IL-1β by monocytes and an increased serum expression of the cytokine correlated with the severity of the disease, since it was significantly higher in DCL patients heavily infected with Leishmania mexicana. The distribution of IL-1β in lesions also varied according to the number of parasites harbored in the tissues: in heavily infected LCL patients and in all DCL patients, the cytokine was scattered diffusely throughout the lesion. In contrast, in LCL patients with lower numbers of parasites in the lesions, IL-1β was confined to the cells. These data suggest that IL-1β possibly is a key player determining the severity of the disease in DCL patients. The analysis of polymorphisms in CXCL8 and IL-1RA showed no differences between patients with different disease severities or between patients and controls
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