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Humans have caused growing levels of ecosystem and diversity changes at a global scale in recent centuries but longer-term diversity trends and how they are affected by human impacts are less well understood. Analysing data from 64,305 pollen samples from 1,763 pollen records revealed substantial community changes (turnover) and reductions in diversity (richness and evenness) in the first ~1,500 to ~4,000 years of the Holocene epoch (starting 11,700 years ago). Turnover and diversity generally increased thereafter, starting ~6,000 to ~1,000 years ago, although the timings, magnitudes and even directions of these changes varied among continents, biomes and sites. Here, modelling these diversity changes, we find that most metrics of biodiversity change are associated with human impacts (anthropogenic land-cover change estimates for the last 8,000 years), often positively but the magnitudes, timings and sometimes directions of associations differed among continents and biomes and sites also varied. Once-forested parts of the world tended to exhibit biodiversity increases while open areas tended to decline. These regionally specific relationships between humans and floristic diversity highlight that human-biodiversity relationships have generated positive diversity responses in some locations and negative responses in others, for over 8,000 years.
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Biodiversidade , Humanos , Pólen , Plantas , Atividades Humanas , Efeitos AntropogênicosRESUMO
OBJECTIVE: As one of the most commonly performed cosmetic procedures, liposuction is relatively safe. Bowel injury following liposuction is a rare but devastating complication, which necessitates hospital admission and surgical intervention. The authors highlight a case report describing the presentation, diagnosis, and management of a patient with bowel injury following liposuction. CASE: A 58-year-old woman presented with abdominal pain, erythema, and discharge three days after 360-degree abdominal liposuction with concomitant fat grafting to bilateral buttocks at an outpatient surgery center. Bowel perforation was suspected after CT-scan revealed extraluminal gas in the abdomen and communication that traversed the peritoneum. Exploratory laparotomy was performed which demonstrated at least one site of distinct perforation of the small bowel and an area omentum noted to be inflamed, thickened and with a purulent rind. The patient underwent 20-cm small bowel resection and partial omentectomy temporarily closed with negative pressure wound therapy. After subsequent abdominal wall debridements the patient received ventral hernia repair with bridging mesh and abdominal closure. CONCLUSIONS: While safe, elective cosmetic procedures are not without risk of serious and even fatal complications. Providers must be familiar with the presentation of bowel injury following abdominal liposuction to prevent delays in appropriate surgical and medical care. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.
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Perfuração Intestinal , Lipectomia , Feminino , Humanos , Pessoa de Meia-Idade , Lipectomia/efeitos adversos , Lipectomia/métodos , Perfuração Intestinal/etiologia , Perfuração Intestinal/cirurgia , Músculos Abdominais , Resultado do Tratamento , Estudos RetrospectivosRESUMO
BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a progressive disease for which no curative treatment is currently available. OBJECTIVE: This study aimed to investigate whether cortico-spinal transcranial direct current stimulation (tDCS) could mitigate symptoms in ALS patients via a randomized, double-blind, sham-controlled trial, followed by an open-label phase. METHODS: Thirty-one participants were randomized into two groups for the initial controlled phase. At baseline (T0), Group 1 received placebo stimulation (sham tDCS), while Group 2 received cortico-spinal stimulation (real tDCS) for five days/week for two weeks (T1), with an 8-week (T2) follow-up (randomized, double-blind, sham-controlled phase). At the 24-week follow-up (T3), all participants (Groups 1 and 2) received a second treatment of anodal bilateral motor cortex and cathodal spinal stimulation (real tDCS) for five days/week for two weeks (T4). Follow-up evaluations were performed at 32-weeks (T5) and 48-weeks (T6) (open-label phase). At each time point, clinical assessment, blood sampling, and intracortical connectivity measures using transcranial magnetic stimulation (TMS) were evaluated. Additionally, we evaluated survival rates. RESULTS: Compared to sham stimulation, cortico-spinal tDCS significantly improved global strength, caregiver burden, and quality of life scores, which correlated with the restoration of intracortical connectivity measures. Serum neurofilament light levels decreased among patients who underwent real tDCS but not in those receiving sham tDCS. The number of completed 2-week tDCS treatments significantly influenced patient survival. CONCLUSIONS: Cortico-spinal tDCS may represent a promising therapeutic and rehabilitative approach for patients with ALS. Further larger-scale studies are necessary to evaluate whether tDCS could potentially impact patient survival. CLINICAL TRIAL REGISTRATION: NCT04293484.
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Esclerose Lateral Amiotrófica , Estimulação Transcraniana por Corrente Contínua , Humanos , Esclerose Lateral Amiotrófica/terapia , Qualidade de Vida , Estimulação Magnética Transcraniana , Método Duplo-CegoRESUMO
Although increased temperatures are known to reinforce the effects of habitat destruction at local to landscape scales, evidence of their additive or interactive effects is limited, particularly over larger spatial extents and longer timescales. To address these deficiencies, we created a dataset of land-use changes over 75 years, documenting the loss of over half (>3000 km2) the semi-natural grassland of Great Britain. Pairing this dataset with climate change data, we tested for relationships to distribution changes in birds, butterflies, macromoths, and plants (n = 1192 species total). We show that individual or additive effects of climate warming and land conversion unambiguously increased persistence probability for 40% of species, and decreased it for 12%, and these effects were reflected in both range contractions and expansions. Interactive effects were relatively rare, being detected in less than 1 in 5 species, and their overall effect on extinction risk was often weak. Such individualistic responses emphasise the importance of including species-level information in policies targeting biodiversity and climate adaptation.
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Borboletas , Animais , Reino Unido , Borboletas/fisiologia , Ecossistema , Biodiversidade , Mudança ClimáticaRESUMO
The narrative of biodiversity decline in response to human impacts is overly simplistic because different aspects of biodiversity show different trajectories at different spatial scales. It is also debated whether human-caused biodiversity changes lead to subsequent, accelerating change (cascades) in ecological communities, or alternatively build increasingly robust community networks with decreasing extinction rates and reduced invasibility. Mechanistic approaches are needed that simultaneously reconcile different aspects of biodiversity change, and explore the robustness of communities to further change. We develop a trophically structured, mainland-archipelago metacommunity model of community assembly. Varying the parameters across model simulations shows that local alpha diversity (the number of species per island) and regional gamma diversity (the total number of species in the archipelago) depend on both the rate of extirpation per island and on the rate of dispersal between islands within the archipelago. In particular, local diversity increases with increased dispersal and heterogeneity between islands, but regional diversity declines because the islands become biotically similar and local one-island and few-island species are excluded (homogenisation, or reduced beta diversity). This mirrors changes observed empirically: real islands have gained species (increased local and island-scale community diversity) with increased human-assisted transfers of species, but global diversity has declined with the loss of endemic species. However, biological invasions may be self-limiting. High-dispersal, high local-diversity model communities become resistant to subsequent invasions, generating robust species-community networks unless dispersal is extremely high. A mixed-up world is likely to lose many species, but the resulting ecological communities may nonetheless be relatively robust.
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Biodiversidade , Biota , HumanosAssuntos
Mudança Climática , Mariposas , Animais , Ecossistema , Biodiversidade , Conservação dos Recursos NaturaisRESUMO
BACKGROUND: Seasonal floods pose a commonly-recognised barrier to women's access to maternal services, resulting in increased morbidity and mortality. Despite their importance, previous GIS models of healthcare access have not adequately accounted for floods. This study developed new methodologies for incorporating flood depths, velocities, and extents produced with a flood model into network- and raster-based health access models. The methodologies were applied to the Barotse Floodplain to assess flood impact on women's walking access to maternal services and vehicular emergency referrals for a monthly basis between October 2017 and October 2018. METHODS: Information on health facilities were acquired from the Ministry of Health. Population density data on women of reproductive age were obtained from the High Resolution Settlement Layer. Roads were a fusion of OpenStreetMap and data manually delineated from satellite imagery. Monthly information on floodwater depth and velocity were obtained from a flood model for 13-months. Referral driving times between delivery sites and EmOC were calculated with network analysis. Walking times to the nearest maternal services were calculated using a cost-distance algorithm. RESULTS: The changing distribution of floodwaters impacted the ability of women to reach maternal services. At the peak of the dry season (October 2017), 55%, 19%, and 24% of women had walking access within 2-hrs to their nearest delivery site, EmOC location, and maternity waiting shelter (MWS) respectively. By the flood peak, this dropped to 29%, 14%, and 16%. Complete inaccessibility became stark with 65%, 76%, and 74% unable to access any delivery site, EmOC, and MWS respectively. The percentage of women that could be referred by vehicle to EmOC from a delivery site within an hour also declined from 65% in October 2017 to 23% in March 2018. CONCLUSIONS: Flooding greatly impacted health access, with impacts varying monthly as the floodwave progressed. Additional validation and application to other regions is still needed, however our first results suggest the use of a hydrodynamic model permits a more detailed representation of floodwater impact and there is great potential for generating predictive models which will be necessary to consider climate change impacts on future health access.
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Inundações , Acessibilidade aos Serviços de Saúde , Serviços de Saúde Materna , Estações do Ano , Zâmbia/epidemiologia , Sistemas de Informação Geográfica , Saúde Materna , Humanos , Feminino , Gravidez , Instalações de Saúde , AdultoRESUMO
Estimating biodiversity change across the planet in the context of widespread human modification is a critical challenge. Here, we review how biodiversity has changed in recent decades across scales and taxonomic groups, focusing on four diversity metrics: species richness, temporal turnover, spatial beta-diversity and abundance. At local scales, change across all metrics includes many examples of both increases and declines and tends to be centred around zero, but with higher prevalence of declining trends in beta-diversity (increasing similarity in composition across space or biotic homogenization) and abundance. The exception to this pattern is temporal turnover, with changes in species composition through time observed in most local assemblages. Less is known about change at regional scales, although several studies suggest that increases in richness are more prevalent than declines. Change at the global scale is the hardest to estimate accurately, but most studies suggest extinction rates are probably outpacing speciation rates, although both are elevated. Recognizing this variability is essential to accurately portray how biodiversity change is unfolding, and highlights how much remains unknown about the magnitude and direction of multiple biodiversity metrics at different scales. Reducing these blind spots is essential to allow appropriate management actions to be deployed. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.
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Biodiversidade , Ecossistema , HumanosRESUMO
Compositional change is a ubiquitous response of ecological communities to environmental drivers of global change, but is often regarded as evidence of declining "biotic integrity" relative to historical baselines. Adaptive compositional change, however, is a foundational idea in evolutionary biology, whereby changes in gene frequencies within species boost population-level fitness, allowing populations to persist as the environment changes. Here, we present an analogous idea for ecological communities based on core concepts of fitness and selection. Changes in community composition (i.e., frequencies of genetic differences among species) in response to environmental change should normally increase the average fitnessof community members. We refer to compositional changes that improve the functional match, or "fit," between organisms' traits and their environment as adaptive community dynamics. Environmental change (e.g., land-use change) commonly reduces the fit between antecedent communities and new environments. Subsequent change in community composition in response to environmental changes, however, should normally increase community-level fit, as the success of at least some constituent species increases. We argue that adaptive community dynamics are likely to improve or maintain ecosystem function (e.g., by maintaining productivity). Adaptive community responses may simultaneously produce some changes that are considered societally desirable (e.g., increased carbon storage) and others that are undesirable (e.g., declines of certain species), just as evolutionary responses within species may be deemed desirable (e.g., evolutionary rescue of an endangered species) or undesirable (e.g., enhanced virulence of an agricultural pest). When assessing possible management interventions, it is important to distinguish between drivers of environmental change (e.g., undesired climate warming) and adaptive community responses, which may generate some desirable outcomes. Efforts to facilitate, accept, or resist ecological change require separate consideration of drivers and responses, and may highlight the need to reconsider preferences for historical baseline communities over communities that are better adapted to the new conditions.
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Biodiversidade , Ecossistema , Animais , Evolução Biológica , Clima , Espécies em Perigo de ExtinçãoRESUMO
The National Institute of Allergy and Infectious Diseases (NIAID) established the Bioinformatics Resource Center (BRC) program to assist researchers with analyzing the growing body of genome sequence and other omics-related data. In this report, we describe the merger of the PAThosystems Resource Integration Center (PATRIC), the Influenza Research Database (IRD) and the Virus Pathogen Database and Analysis Resource (ViPR) BRCs to form the Bacterial and Viral Bioinformatics Resource Center (BV-BRC) https://www.bv-brc.org/. The combined BV-BRC leverages the functionality of the bacterial and viral resources to provide a unified data model, enhanced web-based visualization and analysis tools, bioinformatics services, and a powerful suite of command line tools that benefit the bacterial and viral research communities.
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Genômica , Software , Vírus , Humanos , Bactérias/genética , Biologia Computacional , Bases de Dados Genéticas , Influenza Humana , Vírus/genéticaRESUMO
Entomology is key to understanding terrestrial and freshwater ecosystems at a time of unprecedented anthropogenic environmental change and offers substantial untapped potential to benefit humanity in a variety of ways, from improving agricultural practices to managing vector-borne diseases and inspiring technological advances.We identified high priority challenges for entomology using an inclusive, open, and democratic four-stage prioritisation approach, conducted among the membership and affiliates (hereafter 'members') of the UK-based Royal Entomological Society (RES).A list of 710 challenges was gathered from 189 RES members. Thematic analysis was used to group suggestions, followed by an online vote to determine initial priorities, which were subsequently ranked during an online workshop involving 37 participants.The outcome was a set of 61 priority challenges within four groupings of related themes: (i) 'Fundamental Research' (themes: Taxonomy, 'Blue Skies' [defined as research ideas without immediate practical application], Methods and Techniques); (ii) 'Anthropogenic Impacts and Conservation' (themes: Anthropogenic Impacts, Conservation Options); (iii) 'Uses, Ecosystem Services and Disservices' (themes: Ecosystem Benefits, Technology and Resources [use of insects as a resource, or as inspiration], Pests); (iv) 'Collaboration, Engagement and Training' (themes: Knowledge Access, Training and Collaboration, Societal Engagement).Priority challenges encompass research questions, funding objectives, new technologies, and priorities for outreach and engagement. Examples include training taxonomists, establishing a global network of insect monitoring sites, understanding the extent of insect declines, exploring roles of cultivated insects in food supply chains, and connecting professional with amateur entomologists. Responses to different challenges could be led by amateur and professional entomologists, at all career stages.Overall, the challenges provide a diverse array of options to inspire and initiate entomological activities and reveal the potential of entomology to contribute to addressing global challenges related to human health and well-being, and environmental change.
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Megadrought in the western United States is jeopardizing water security. Groundwater regulations, such as California's Sustainable Groundwater Management Act (SGMA), aim to preserve groundwater resources in overdrafted basins. Water agencies must establish sufficient monitoring systems to measure local groundwater abstraction and devise plans to moderate groundwater use. However, few technologies are available to monitor and regulate groundwater abstraction spatially and temporally. In this study, we deployed satellite-connected electrical current sensors on 11 agricultural groundwater pumps in Solano County, California over 2019-2022. A high correlation (R 2 = 0.706) was found between the in situ sensors and in-line flow meters. We then combine in situ sensor data with a land surface model to develop a multiple linear regression model of groundwater abstraction and groundwater level. Using a 10-fold cross-validation, it is found that our predictive groundwater abstraction model has approximately a 3.5% bias and a mean absolute error of 1.21 acre-feet, while our predictive groundwater level model has approximately 4.2% bias and about 5.9 acre-feet mean absolute error. Finally, we integrated these data with a blockchain-based groundwater credit trading platform to demonstrate how such a tool could be used for SGMA compliance.
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Bacterial secondary metabolites are a major source of antibiotics and other bioactive compounds. In microbial communities, these molecules can mediate interspecies interactions and responses to environmental change. Despite the importance of secondary metabolites in human health and microbial ecology, little is known about their roles and regulation in the context of multispecies communities. In a simplified model of the rhizosphere composed of Bacillus cereus, Flavobacterium johnsoniae, and Pseudomonas koreensis, we show that the dynamics of secondary metabolism depend on community species composition and interspecies interactions. Comparative metatranscriptomics and metametabolomics reveal that the abundance of transcripts of biosynthetic gene clusters (BGCs) and metabolomic molecular features differ between monocultures or dual cultures and a tripartite community. In both two- and three-member cocultures, P. koreensis modified expression of BGCs for zwittermicin, petrobactin, and other secondary metabolites in B. cereus and F. johnsoniae, whereas the BGC transcriptional response to the community in P. koreensis itself was minimal. Pairwise and tripartite cocultures with P. koreensis displayed unique molecular features that appear to be derivatives of lokisin, suggesting metabolic handoffs between species. Deleting the BGC for koreenceine, another P. koreensis metabolite, altered transcript and metabolite profiles across the community, including substantial up-regulation of the petrobactin and bacillibactin BGCs in B. cereus, suggesting that koreenceine represses siderophore production. Results from this model community show that bacterial BGC expression and chemical output depend on the identity and biosynthetic capacity of coculture partners, suggesting community composition and microbiome interactions may shape the regulation of secondary metabolism in nature.
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Microbiota , Sideróforos , Antibacterianos , Benzamidas , Humanos , Metabolismo Secundário , Sideróforos/genética , Sideróforos/metabolismoRESUMO
This study provides insight into New York City residents' perceptions about violence after the outbreak of Coronavirus disease (COVID-19) based on information from communities in New York City Housing Authority (NYCHA) buildings. In this novel analysis, we used focus group and social media data to confirm or reject findings from qualitative interviews. We first used data from 69 in-depth, semi-structured interviews with low-income residents and community stakeholders to further explore how violence impacts New York City's low-income residents of color, as well as the role of city government in providing tangible support for violence prevention during co-occurring health (COVID-19) and social (anti-Black racism) pandemics. Residents described how COVID-19 and the Black Lives Matter movement impacted safety in their communities while offering direct recommendations to improve safety. Residents also shared recommendations that indirectly improve community safety by addressing long term systemic issues. As the recruitment of interviewees was concluding, researchers facilitated two focus groups with 38 interviewees to discuss similar topics. In order to assess the degree to which the themes discovered in our qualitative interviews were shared by the broader community, we developed an integrative community data science study which leveraged natural language processing and computer vision techniques to study text and images on public social media data of 12 million tweets generated by residents. We joined computational methods with qualitative analysis through a social work lens and design justice principles to most accurately and holistically analyze the community perceptions of gun violence issues and potential prevention strategies. Findings indicate valuable community-based insights that elucidate how the co-occurring pandemics impact residents' experiences of gun violence and provide important implications for gun violence prevention in a digital era.
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COVID-19 , Violência com Arma de Fogo , Humanos , Pandemias/prevenção & controle , Violência com Arma de Fogo/prevenção & controle , COVID-19/prevenção & controle , Violência/prevenção & controle , Cidade de Nova Iorque/epidemiologiaRESUMO
Land-use change is widely regarded as a simplifying and homogenising force in nature. In contrast, analysing global land-use reconstructions from the 10th to 20th centuries, we found progressive increases in the number, evenness, and diversity of ecosystems (including human-modified land-use types) present across most of the Earth's land surface. Ecosystem diversity increased more rapidly after ~1700 CE, then slowed or slightly declined (depending on the metric) following the mid-20th century acceleration of human impacts. The results also reveal increasing spatial differentiation, rather than homogenisation, in both the presence-absence and area-coverage of different ecosystem types at sub-global scales-at least, prior to the mid-20th century. Nonetheless, geographic homogenization was revealed for a subset of analyses at a global scale, reflecting the now-global presence of certain human-modified ecosystem types. Our results suggest that, while human land-use changes have caused declines in relatively undisturbed or "primary" ecosystem types, they have also driven increases in ecosystem diversity over the last millennium.
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Biodiversidade , Ecossistema , HumanosRESUMO
The use of transcranial Electrical Stimulation (tES) in the modulation of cognitive brain functions to improve neuropsychiatric conditions has extensively increased over the decades. tES techniques have also raised new challenges associated with study design, stimulation protocol, functional specificity, and dose-response relationship. In this paper, we addressed challenges through the emerging methodology to investigate the dose-response relationship of High Definition-transcranial Direct Current Stimulation (HD tDCS), identifying the role of negative valence in tinnitus perception. In light of the neurofunctional testable framework and tES application, hypotheses were formulated to measure clinical and surrogate endpoints. We posited that conscious pairing adequately pleasant stimuli with tinnitus perception results in correction of the loudness misperception and would be reinforced by concurrent active HD-tDCS on the left Dorsolateral Prefrontal Cortex (dlPFC). The dose-response relationship between HD-tDCS specificity and the loudness perception is also modeled. We conducted a double-blind, randomized crossover pilot study with six recruited tinnitus patients. Accrued data was utilized to design a well-controlled adaptive seamless Bayesian dose-response study. The sample size (n = 47, for 90% power and 95% confidence) and optimum interims were anticipated for adaptive decision-making about efficacy, safety, and single session dose parameters. Furthermore, preliminary pilot study results were sufficient to show a significant difference (90% power, 99% confidence) within the longitudinally detected self-report tinnitus loudness between before and under positive emotion induction. This study demonstrated a research methodology used to improve emotion regulation in tinnitus patients. In the projected method, positive emotion induction is essential for promoting functional targeting under HD-tDCS anatomical specificity to indicate the efficacy and facilitate the dose-finding process. The continuous updating of prior knowledge about efficacy and dose during the exploratory stage adapts the anticipated dose-response model. Consequently, the effective dose range to make superiority neuromodulation in correcting loudness misperception of tinnitus will be redefined. Highly effective dose adapts the study to a standard randomized trial and transforms it into the confirmatory stage in which active HD-tDCS protocol is compared with a sham trial (placebo-like). Establishing the HD-tDCS intervention protocols relying on this novel method provides reliable evidence for regulatory agencies to approve or reject the efficacy and safety. Furthermore, this paper supports a technical report for designing multimodality data-driven complementary investigations in emotion regulation, including EEG-driven neuro markers, Stroop-driven attention biases, and neuroimaging-driven brain network dynamics.
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Mammals have experienced high levels of human-mediated extirpations but have also been widely introduced to new locations, and some have recovered from historic persecution. Both of these processes-losses and gains-have resulted in concern about functional losses and changes in ecological communities as new ecological states develop. The question of whether species turnover inevitably leads to declines in functional and phylogenetic diversity depends, however, on the traits and phylogenetic distinctiveness of the species that are lost, gained, or regained. Comparing ~8000 years ago with the last century, we show that extirpations and range retractions have indeed reduced the functional and phylogenetic diversity of mammals in most European regions (countries and island groups), but species recoveries and the introduction of non-native species have increased functional and phylogenetic diversity by equivalent or greater amounts in many regions. Overall, across Europe, species richness increased in 41 regions over the last 8000 years and declined in 1; phylogenetic diversity increased in 33 and declined in 12, while functional diversity results showed 20 increases and 25 decreases. The balance of losses (extirpations) and gains (introductions, range expansions) has, however, led to net increases in functional diversity on many islands, where the original diversity was low, and across most of western Europe. Historically extirpated mega- and mesofaunal species have recolonized or been reintroduced to many European regions, contributing to recent functional and phylogenetic diversity recovery. If conservation rewilding projects continue to reintroduce regionally extirpated species and domestic descendants of "extinct" species to provide replacement grazing, browsing, and predation, there is potential to generate net functional and phylogenetic diversity gains (relative to 8000 years ago) in most European regions.
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Biodiversidade , Mamíferos , Animais , Biota , Europa (Continente) , Humanos , FilogeniaRESUMO
Evolutionary change impacts the rate at which insect pests, pollinators, or disease vectors expand or contract their geographic ranges. Although evolutionary changes, and their ecological feedbacks, strongly affect these risks and associated ecological and economic consequences, they are often underappreciated in management efforts. Greater rigor and scope in study design, coupled with innovative technologies and approaches, facilitates our understanding of the causes and consequences of eco-evolutionary dynamics in insect range shifts. Future efforts need to ensure that forecasts allow for demographic and evolutionary change and that management strategies will maximize (or minimize) the adaptive potential of range-shifting insects, with benefits for biodiversity and ecosystem services.
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Evolução Biológica , Ecossistema , Animais , Biodiversidade , InsetosRESUMO
OBJECTIVE: This study aimed to assess whether non-invasive brain stimulation with transcranial alternating current stimulation at gamma-frequency (γ-tACS) applied over the precuneus can improve episodic memory and modulate cholinergic transmission by modulating cerebral rhythms in early Alzheimer's disease (AD). METHODS: In this randomized, double-blind, sham controlled, crossover study, 60 AD patients underwent a clinical and neurophysiological evaluation including assessment of episodic memory and cholinergic transmission pre and post 60 minutes treatment with γ-tACS targeting the precuneus or sham tACS. In a subset of 10 patients, EEG analysis and individualized modelling of electric field distribution were carried out. Predictors to γ-tACS efficacy were evaluated. RESULTS: We observed a significant improvement in the Rey Auditory Verbal Learning (RAVL) test immediate recall (p < 0.001) and delayed recall scores (p < 0.001) after γ-tACS but not after sham tACS. Face-name associations scores improved with γ-tACS (p < 0.001) but not after sham tACS. Short latency afferent inhibition, an indirect measure of cholinergic transmission, increased only after γ-tACS (p < 0.001). ApoE genotype and baseline cognitive impairment were the best predictors of response to γ-tACS. Clinical improvement correlated with the increase in gamma frequencies in posterior regions and with the amount of predicted electric field distribution in the precuneus. INTERPRETATION: Precuneus γ-tACS, able to increase γ-power activity on the posterior brain regions, showed a significant improvement of episodic memory performances, along with restoration of intracortical excitability measures of cholinergic transmission. Response to γ-tACS was dependent on genetic factors and disease stage. ANN NEUROL 2022;92:322-334.
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Doença de Alzheimer , Memória Episódica , Estimulação Transcraniana por Corrente Contínua , Doença de Alzheimer/terapia , Encéfalo , Colinérgicos , Estudos Cross-Over , HumanosRESUMO
OBJECTIVE: The objective of the study was to investigate transcranial wave propagation through two low-intensity focused ultrasound (LIFU)-based brain stimulation techniques-transcranial focused ultrasound stimulation (tFUS) and transcranial pulse stimulation (TPS). Although tFUS involves delivering long trains of acoustic pulses, the newly introduced TPS delivers ultrashort (â¼3 µs) pulses repeated at 4 Hz. Accordingly, only a single simulation study with limited geometry currently exists for TPS. We considered a high-resolution three-dimensional (3D) whole human head model in addition to water bath simulations. We anticipate that the results of this study will help researchers investigating LIFU have a better understanding of the effects of the two different techniques. APPROACH: With an objective to first reproduce previous computational results, we considered two spherical tFUS transducers that were previously modeled. We assumed identical parameters (geometry, position, and imaging data set) to demonstrate differences, purely because of the waveform considered. For simulations with a 3D head data set, we also considered a parabolic transducer that has been used for TPS delivery. RESULTS: Our initial results successfully verified previous modeling workflow. The tFUS distribution was characterized by the typical elliptical profile, with its major axis perpendicular to the face of the transducer. The TPS distribution resembled two mirrored meniscus profiles, with its widest diameter oriented parallel to the face of the transducer. The observed intensity value differences were theoretical because the two waveforms differ in both intensity and time. The consideration of a realistic 3D human head model resulted in only a minor distortion of the two waveforms. SIGNIFICANCE: This study simulated TPS administration using a 3D realistic image-derived data set. Although our comparison results are strictly limited to the model parameters and assumptions made, we were able to elucidate some clear differences between the two approaches. We hope this initial study will pave the way for systematic comparison between the two approaches in the future.