Explore the vast range of titles available.

Mercury emissions from artisanal and small-scale gold mining throughout the Global South exceed coal combustion as the largest global source of mercury. We examined mercury deposition and storage in an area of the Peruvian Amazon heavily impacted by artisanal gold mining. Intact forests in the Peruvian Amazon near gold mining receive extremely high inputs of mercury and experience elevated total mercury and methylmercury in the atmosphere, canopy foliage, and soils. Here we show for the first time that an intact forest canopy near artisanal gold mining intercepts large amounts of particulate and gaseous mercury, at a rate proportional with total leaf area. We document substantial mercury accumulation in soils, biomass, and resident songbirds in some of the Amazon’s most protected and biodiverse areas, raising important questions about how mercury pollution may constrain modern and future conservation efforts in these tropical ecosystems. The Peruvian Amazon is facing the highest known input of mercury pollution of any ecosystem globally. Intact forests located near artisanal gold mining are particularly at risk from this toxin.

Background Excitotoxicity is a process in which NADPH oxidase‐2 (NOX‐2) plays a pivotal role in the generation of reactive oxygen species (ROS). Oxidative stress influences the expression of Aquaporin 4 (AQP4), a water channel implicated in blood–brain barrier (BBB) permeability and edema formation. The endocannabinoid system is widely distributed in the brain, particularly through the cannabinoid receptor type 1 (CB1) and type 2 (CB2), which have been shown to have a neuroprotective function in brain injury. Given the significant involvement of NOX‐2 in ROS production during excitotoxicity, our research aims to assess the participation of NOX‐2 in the neuroprotective effect of the cannabinoid receptor agonist WIN55,212‐2 against glutamate‐induced excitotoxicity damage in the striatum using in vivo model. Methods Wild‐type mice (C57BL/6) and NOX‐2 KO (gp91Cybbtm1Din/J) were stereotactically injected in the striatum with monosodium glutamate or vehicle. Subsequently, a group of mice was administered an intraperitoneal dose of WIN55,212‐2, AM251, or AM251/WIN55,212‐2 following the intracerebral injection. Motor activity was assessed, and the lesion was examined through histological sections stained with cresyl violet. Additionally, brain water content and Evans blue assay were conducted. The activity of NOX was quantified, and the protein expression of CB1, gp91phox, AQP4, Iba‐1, TNF‐α, and NF‐κB was analyzed using Western blot. Furthermore, ROS formation was measured through the DHE assay. Results The activation of the endocannabinoid receptors demonstrated a neuroprotective response during excitotoxicity, meditated by NOX‐2. The reduction in ROS production led to a decrease in neuroinflammation, and AQP4 expression, resulting in reduced edema formation, and BBB permeability. Conclusions During excitotoxic damage, WIN55,212‐2 inhibits NOX‐2‐induced ROS production, reducing brain injury. During excitotoxicity, reactive oxygen species, produced by NADPH‐oxidase 2 (NOX‐2), increases the levels of aquaporin‐4 (AQP4) leading to the rupture of the blood–brain barrier and cerebral edema. This along with oxidative stress contributes to neuronal death. Stimulation of cannabinoid receptor type 1 receptors relieves oxidative stress by a reduction of NOX‐2 activity and thus inhibits AQP4 increase, edema, and brain damage. The endocannabinoid system can be a therapeutic target for limiting brain damage.

Predation is a strong ecological force that shapes animal communities through natural selection. Recent studies have shown the cascading effects of predation risk on ecosystems through changes in prey behavior. Minimizing predation risk may explain why multiple prey species associate together in space and time. For example, mixed-species flocks that have been widely documented from forest systems, often include birds that eavesdrop on sentinel species (alarm calling heterospecifics). Sentinel species may be pivotal in (1) allowing flocking species to forage in open areas within forests that otherwise incur high predation risk, and (2) influencing flock occurrence (the amount of time species spend with a flock). To test this, we conducted a short-term removal experiment in an Amazonian lowland rainforest to test whether flock habitat use and flock occurrence was influenced by sentinel presence. Antshrikes (genus Thamnomanes) act as sentinels in Amazonian mixed-species flocks by providing alarm calls widely used by other flock members. The alarm calls provide threat information about ambush predators such as hawks and falcons which attack in flight. We quantified home range behavior, the forest vegetation profile used by flocks, and the proportion occurrence of other flocking species, both before and after removal of antshrikes from flocks. We found that when sentinel species were removed, (1) flock members shifted habitat use to lower risk habitats with greater vegetation cover, and (2) species flock occurrence decreased. We conclude that eavesdropping on sentinel species may allow other species to expand their realized niche by allowing them to safely forage in high-risk habitats within the forest. In allowing species to use extended parts of the forest, sentinel species may influence overall biodiversity across a diverse landscape.

Brain edema is a critical complication arising from stroke and traumatic brain injury (TBI) with an important impact on patient recovery and can lead to long-term consequences. Therapeutic options to reduce edema progression are limited with variable patient outcomes. Aquaporin 4 (AQP4) is a water channel that allows bidirectional water diffusion across the astrocyte membrane and participates in the distinct phases of cerebral edema. The absence or inhibition of this channel has been demonstrated to ameliorate edema and brain damage. The endocannabinoid system (ECS) is a neuromodulator system with a wide expression in the brain and its activation has shown neuroprotective properties in diverse models of neuronal damage. This review describes and discusses the major features of ECS and AQP4 and their role during brain damage, observing that ECS stimulation reduces edema and injury size in diverse models of brain damage, however, the relationship between AQP4 expression and dynamics and ECS activation remains unclear. The research on these topics holds promising therapeutic implications for the treatment of brain edema following stroke and TBI.

IntroductionThis case report illustrates a new variant in the anterior cerebral artery complex, identified during carotid angioplasty.Clinical caseA 50-year-old male patient diagnosed with left carotid stenosis was diagnosed and treated by a cerebral angiography. During the procedure, crossed circulation in the anterior cerebral artery was identified. The presence of this variation demanded to discard distal emboli or artery dissection. Angioplasty was performed and the patient followed up without neurological deficit.DiscussionAmong the most possible and prevalent variations in anterior circulation, none of them explain the phenomenon we observed. Therefore, a new variant is established. The knowledge about variants in cerebral circulation is important to rule out pathology.ConclusionCerebral diagnostic angiography has become more available and frequent because of the rising in endovascular tools to treat stroke patients. Considering this new variation and others is important to discard pathology.

Within a community, different species might share similar predation risks, and, thus, the ability of species to signal and interpret heterospecific threat information may determine species’ associations. We combined observational, experimental, and phylogenetic approaches to determine the extent to which evolutionary history and functional traits determined flocking propensity and perceived predation risk (response to heterospecific alarm calls) in a lowland Amazonian bird community. We predicted that small birds that feed myopically and out in the open would have higher flocking propensities and account for a higher proportion of positive responses to alarms. Using generalized linear models and the incorporation of phylogeny on data from 56 species, our results suggest that phylogenetic relationships alongside body size, foraging height, vegetation density, and response to alarm calls influence flocking propensity. Conversely, phylogenetic relationships did not influence response to heterospecific alarm calls. Among functional traits, however, foraging strategy, foraging density, and flocking propensity partially explained responses to alarm calls. Our results suggest that flocking propensity and perceived predation risk are positively related and that functional ecological traits and evolutionary history may explain certain species’ associations.

Animals eavesdrop on other species to obtain information about their environments. Heterospecific eavesdropping can yield tangible fitness benefits by providing valuable information about food resources and predator presence. The ability to eavesdrop may therefore be under strong selection, although extensive research on alarm-calling in avian mixed-species flocks has found only limited evidence that close association with another species could select for innate signal recognition. Nevertheless, very little is known about the evolution of eavesdropping behaviour and the mechanism of heterospecific signal recognition, particularly in other ecological contexts, such as foraging. To understand whether heterospecific eavesdropping was an innate or learned behaviour in a foraging context, we studied heterospecific signal recognition in ant-following birds of the Neotropics, which eavesdrop on vocalizations of obligate ant-following species to locate and recruit to swarms of the army ant Eciton burchellii, a profitable food resource. We used a playback experiment to compare recruitment of ant-following birds to vocalizations of two obligate species at a mainland site (where both species are present) and a nearby island site (where one species remains whereas the other went extinct approx. 40 years ago). We found that ant-following birds recruited strongly to playbacks of the obligate species present at both island and mainland sites, but the island birds did not recruit to playbacks of the absent obligate species. Our results strongly suggest that (i) ant-following birds learn to recognize heterospecific vocalizations from ecological experience and (ii) island birds no longer recognize the locally extinct obligate species after eight generations of absence from the island. Although learning appears to be the mechanism of heterospecific signal recognition in ant-following birds, more experimental tests are needed to fully understand the evolution of eavesdropping behaviour.

Urbanization is a significant pressure affecting wildlife and has the potential to greatly alter behavioral responses in animal communities. A behavioral response that is potentially affected by urbanization is the mobbing of predators by potential avian prey species. We tested three hypotheses concerning the effects of various abiotic and biotic factors in influencing avian mobbing responses along an urban–rural gradient. We conducted predator simulations by using playback of the vocalizations of the Western Screech‐owl, Megascops kennicottii, which is a predatory species that elicits a mobbing response from other birds. These vocalizations, accompanied by stuffed models of the screech‐owls, were broadcast at a variety of points along an urban–rural gradient in Los Angeles and Orange Counties in Southern California. We used an experimental approach using playback, that is, vocalization and models, to investigate whether mobbing responses of birds change in areas where predators may be naturally present (high vegetation density) or absent (high impervious cover). We recorded the number of individual birds and species that exhibited mobbing behavior at experimental sites, as well as various biotic and abiotic factors that may influence avian mobbing, including noise level, impervious surface cover, avian community turnover across the urban‐to‐rural gradient, and the structure of local vegetation, which we assumed may be important for either hosting roosting screech‐owls or providing cover for mobbing bird species. For both the number of mobbing individuals and species, we showed that mobbing responses decreased with increasing noise levels and percentage of impervious surfaces and increased with increasing woody vegetation. There was some evidence that predator presence influenced mobbing responses. Our results show that the changes associated with urbanization can significantly alter antipredator behavior in birds, and that these changes can alter avian social eavesdropping networks.

The stability of tropical systems has been hypothesized to explain the evolution of complex behavioral interactions among species. We evaluate the degree to which one highly evolved social system, mixed-species flocks, are stable in space and time in French Guiana, where flocks were characterized 17 years apart. These flocks are led by alarm-calling “sentinels,” which may benefit from food flushed by other “beater” species. Using null models, we found that flock roost sites, home range overlap, and composition were more similar than expected by chance; home ranges were nearly identical between the two time periods. Such extremely stable conditions may be essential for the evolution and maintenance of the sentinel-beater system that appears to characterize some flocks. These results may reflect an evolutionarily stable strategy among potentially interdependent species within mixed-species flocks, where home ranges contribute to stability by being far larger than the most common local disturbances in the forest.

Batrachochytrium dendrobatidis (Bd), an amphibian fungal pathogen, has infected >500 species and caused extinctions or declines in >200 species worldwide. Despite over a decade of research, little is known about its invasion biology. To better understand this, we conducted a museum specimen survey (1910–1997) of Bd in amphibians on 11 California islands and found a pattern consistent with the emergence of Bd epizootics on the mainland, suggesting that geographic isolation did not prevent Bd invasion. We propose that suitable habitat, host diversity, and human visitation overcome isolation from the mainland and play a role in Bd invasion.