Range structure analysis: unveiling the internal structure of species’ ranges

Assessing risks of local extinction and shifts in species ranges are fundamental tasks in ecology and conservation. Most studies have focused either on the border of species’ range or on complex spatiotemporal dynamics of populations within the spatial distribution of species. The internal properties of species ranges, however, have received less attention due to a general lack of simple tools. We propose a novel approach within a metapopulation framework to study species ranges based on simple mathematical rules. We formulate and test a model of population fluctuations through space to identify key factors that regulate population density. We propose that spatial variability in species abundance reflects the interaction between temporal variability in population dynamics and the spatial variability of population parameters. This approach, that we call range structure analysis, integrates temporal and spatial properties to diagnose how each parameter contributes to species occupancy throughout its geographic range.     

Sucrose signaling in plants: A world yet to be explored

The role of sucrose as a signaling molecule in plants was originally proposed several decades ago. However, recognition of sucrose as a true signal has been largely debated and only recently this role has been fully accepted. The best-studied cases of sucrose signaling involve metabolic processes, such as the induction of fructan or anthocyanin synthesis, but a large volume of scattered information suggests that sucrose signals may control a vast array of developmental processes along the whole life cycle of the plant. Also, wide gaps exist in our current understanding of the intracellular steps that mediate sucrose action. Sucrose concentration in plant tissues tends to be directly related to light intensity, and inversely related to temperature, and accordingly, exogenous sucrose supply often mimics the effect of high light and cold. However, many exceptions to this rule seem to occur due to interactions with other signaling pathways. In conclusion, the sucrose role as a signal molecule in plants is starting to be unveiled and much research is still needed to have a complete map of its significance in plant function.     

Antiviral bioactivity of resveratrol against Zika virus infection in human retinal pigment epithelial cells

Resveratrol (RES) is a polyphenol with increasing interest for its inhibitory effects on a wide variety of viruses. Zika virus (ZIKV) is an arbovirus which causes a broad spectrum of ophthalmological manifestations in humans. Currently there is no certified therapy or vaccine to treat it, thus it has become a major global health threat. Retinal pigment epithelium (RPE) is highly permissive and susceptible to ZIKV. This work explored the protective effects of RES on ZIKV-infected human RPE cells. RES treatment resulted in a significant reduction of infectious viral particles in infected male ARPE-19 and female hTERT-RPE1 cells. This protection was positively influenced by the action of RES on mitochondrial dynamics. Also, docking studies predicted that RES has a high affinity for two enzymes of the rate-limiting steps of pyrimidine and purine biosynthesis and viral polymerase. This evidence suggests that RES might be a potential antiviral agent to treat ZIKV-induced ocular abnormalities.

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Oscillations and variability in neuronal systems: interplay of autonomous transient dynamics and fast deterministic fluctuations

Journal of Computational Neuroscience - Neuronal systems are subject to rapid fluctuations both intrinsically and externally. These fluctuations can be disruptive or constructive. We investigate...     

First multi-proxy record of Jurassic wildfires from Gondwana: Evidence from the Middle Jurassic of the Neuquén Basin,Argentina

Wildfires play a crucial role in recent and ancient ecosystem modeling but their detailed history on the Earth is still not well recorded or understood. The co-occurrence of charcoal and pyrolytic polycyclic aromatic hydrocarbons (PAHs) is used for the recognition of wildfires in geological record that may have implications for the analysis of the terrestrial environment, ecosystems, climate and the level of atmospheric oxygen. Here we present the first multi-proxy evidence of wildfires on the Gondwana continent during the Jurassic, based on the occurrence of charcoal and pyrolytic PAHs in the Middle Jurassic of the Neuquén Basin, Argentina. This is the first evidence of wildfire in the Aalenian, the lowest stage of the Middle Jurassic, and one of the few records of wildfires in the Bathonian. Temperature interpretations, derived from charcoal reflectance data, show that charcoals formed in low temperature surface fires that only sporadically reached the higher temperatures, possibly related to crown fires. The occurrence of charcoals in the Middle Jurassic deposits confirms recent results that the atmospheric oxygen level reached at least 15% during the Middle Jurassic times.     

Metabolism of the anticancer agent 1-(4-acetylphenyl)-3,3-dimethyltriazene

High pressure liquid chromatography was used in combination with mass spectrometry to confirm that the main products of in vitro metabolism of 1-(4-acetylphenyl)-3,3-dimethyltriazene are 1-(4-acetylphenyl-3-methyltriazene and 4-aminoacetophenone. In addition a novel metabolite, 1-[4-(1-hydroxyethyl)-phenyl]-3,3-dimethyltriazene, possessing antitumour activity similar to the parent drug, was identified.     

Planktivory by larval Odontesthes bonariensis (Atherinidae: Pisces) and its effects on zooplankton community structure

This paper describes the effect of predation by larvae of theatherinid Odontesthes bonariensis upon the zooplankton communityduring a 3-month experiment Three-day-old larvae were stockedin 45 m² concrete tanks at rates of 100 and 200 fish m^–2Gut content analyses showed that the larvae consumed relativelysmall prey all along the experiment Morphological (mouth width)and physiological (gastric inefficiency) constraints seems tohave precluded the capture of the largest prey. The prey community,however, showed all the symptoms generally ascribed to size-selectivepredation upon the largest individuals: decrease in maximumzooplankton size and mean cladoceran size, decrease in cladoceranand copepod biomass, extinction of the largest zooplankton species(Daphnia stmilis), increase in rotifer biomass, etc It is concludedthat size-selective predation is not a necessary condition forthe commonly observed decrease in zooplankton size after theincrease in density of a vertebrate predator. The ecologicalimplications of this result are discussed. Present address: Department of Biology, Lehigh University, WilliamsHall 31, Bethlehem, PA 18015-3189, USA     

Cytoprotective Effect of Ferritin H in Renal Ischemia Reperfusion Injury

Oxidative stress is a major contributor to kidney injury following ischemia reperfusion. Ferritin, a highly conserved iron-binding protein, is a key protein in the maintenance of cellular iron homeostasis and protection from oxidative stress. Ferritin mitigates oxidant stress by sequestering iron and preventing its participation in reactions that generate reactive oxygen species. Ferritin is composed of two subunit types, ferritin H and ferritin L. Using an in vivo model that enables conditional tissue-specific doxycycline-inducible expression of ferritin H in the mouse kidney, we tested the hypothesis that an increased level of H-rich ferritin is renoprotective in ischemic acute renal failure. Prior to induction of ischemia, doxycycline increased ferritin H in the kidneys of the transgenic mice nearly 6.5-fold. Following reperfusion for 24 hours, induction of neutrophil gelatinous-associated lipocalin (NGAL, a urine marker of renal dysfunction) was reduced in the ferritin H overexpressers compared to controls. Histopathologic examination following ischemia reperfusion revealed that ferritin H overexpression increased intact nuclei in renal tubules, reduced the frequency of tubular profiles with luminal cast materials, and reduced activated caspase-3 in the kidney. In addition, generation of 4-hydroxy 2-nonenal protein adducts, a measurement of oxidant stress, was decreased in ischemia-reperfused kidneys of ferritin H overexpressers. These studies demonstrate that ferritin H can inhibit apoptotic cell death, enhance tubular epithelial viability, and preserve renal function by limiting oxidative stress following ischemia reperfusion injury.